Kristoffer Toldnes Cumming

• Vikmoen, Olav; Teien, Hilde Kristin; Tansø, Rita; Aandstad, Anders; Lander, Elise & Cumming, Kristoffer Toldnes [Vis alle 7 forfattere av denne artikkelen] (2023). Effects of a 10-d Military Field Exercise on Body Composition, Physical Performance, and Muscle Cells in Men and Women. Medicine & Science in Sports & Exercise. ISSN 0195-9131. 56(4), s. 682–696. doi: 10.1249/MSS.0000000000003340. Vis sammendrag

  Purpose: To investigate the effects of a demanding military field exercise on physical performance, body composition and muscle cellular outcomes in men and women. Methods: Ten men (20.5 ± 0.5 years) and 8 women (21.4 ± 1.4 years) completed a 10-day field exercise consisting of extensive physical activity with food and sleep restriction. Acquisition of body composition, physical performance, blood and muscle biopsies samples were done before and 1,7 and 14 days after the exercise. Results: There were no sex differences in the response to the exercise. Body mass was decreased with 5.6 ± 1.8% and fat mass with 31 ± 11% during the exercise. Both were still reduced after 14 days (2.5 ± 2.3%, p˂0.001 and 12.5 ± 7.7%, p˂0.001 respectively). Isometric leg strength did not change. Peak leg extension torque at 240 °·s-1 and counter movement jump height were reduced with 4.6 ± 4.8% (p = 0.012) and 6.7 ± 6.2% (p˂0.001) respectively and was still reduced after 14 days (4.3 ± 4.2%, p = 0.002, and 4.1 ± 4.7%, p = 0.030). No changes occurred in fiber CSA, fiber types, proteins involved in calcium handling or HSP70. During the exercise, αB-crystallin levels decreased by 14 ± 19% (p = 0.024) in the cytosolic fraction and staining intensity on muscle sections tended to increase (17 ± 25%, p = 0.076). MuRF1 levels in the cytosolic fraction tended to decrease (19 ± 35%) and increased with 85 ± 105% (p = 0.003) in the cytoskeletal fraction 1 week after the exercise. Conclusions: The field exercise resulted in reduced body mass and physical performance in both sexes. The ability to produce force at high contraction velocities and explosive strength was more affected than isometric strength, but this was not related to any changes in fiber type composition, fiber area, Ca2+ handling or fiber type specific muscle damage.

• Andersen, Vidar; Prieske, Olaf; Stien, Nicolay; Cumming, Kristoffer Toldnes; Solstad, Tom Erik Jorung & Paulsen, Gøran [Vis alle 9 forfattere av denne artikkelen] (2022). Comparing the effects of variable and traditional resistance training on maximal strength and muscle power in healthy adults: A systematic review and meta-analysis. Journal of Science and Medicine in Sport. ISSN 1440-2440. 25(12), s. 1023–1032. doi: 10.1016/j.jsams.2022.08.009. Fulltekst i vitenarkiv Vis sammendrag

  Objectives: The aim of the study was to aggregate different effects between variable resistance training and traditional resistance training on maximal muscle strength and muscle power and identify potential sex- and training program-related moderator variables. Design: Meta-analysis. Methods: A systematic literature search was conducted in SPORTDiscus, PubMed, and Web of Science. Interventions were included if they compared variable resistance training and traditional resistance training in healthy adults and examined the effects on measures of maximal muscle strength and/or muscle power of the lower and/or upper body. A random-effects model was used to calculate weighted and averaged standardized mean differences. Additionally, univariate sub-group analyses were independently computed for sex and training-related moderator variables. Results: Seventeen studies comprising a total of 491 participants (341 men and 150 women, age 18–37 years) were included in the analyses. In terms of maximal muscle strength, there were no statistically significant differences between variable resistance training and traditional resistance training for the lower (p = 0.46, standardized mean difference = −0.10) or the upper body (p = 0.14, standardized mean difference = −0.17). Additionally, there were no significant training-related differences in muscle power for the lower (p = 0.16, standardized mean difference = 0.21) or upper body (p = 0.81, standardized mean difference = 0.05). Sub-group analyses showed a significant moderator effect for training period and repetitions per set for maximal muscle strength in the lower body (p = 0.03–0.04) with larger strength gains following traditional resistance training when performing more repetitions per set (p = 0.02, standardized mean difference = 0.43). No other significant sub-group effects were found (p = 0.18–0.82). Conclusions: Our results suggest that variable resistance training and traditional resistance training are equally effective in improving maximal muscle strength and muscle power in healthy adults.

• Gjesdal, Beate Eltarvåg; Mæland, Silje; Bogen, Bård Erik; Cumming, Kristoffer Toldnes; Nesse, Vilde Cathrine & Torberntsson, Silje Marie Rydningen [Vis alle 7 forfattere av denne artikkelen] (2022). Ballistic strength training in adults with cerebral palsy may increase rate of force development in plantar flexors, but transition to walking remains unclear: a case series. BMC sports science, medicine and rehabilitation. ISSN 2052-1847. 14(1). doi: 10.1186/s13102-022-00487-1. Fulltekst i vitenarkiv
• Pedersen, Helene; Fimland, Marius Steiro; Schoenfeld, Brad J; Iversen, Vegard Moe; Cumming, Kristoffer Toldnes & Jensen, Susanne [Vis alle 8 forfattere av denne artikkelen] (2022). A randomized trial on the efficacy of split-body versus full-body resistance training in non-resistance trained women. BMC sports science, medicine and rehabilitation. ISSN 2052-1847. 14(1). doi: 10.1186/s13102-022-00481-7. Fulltekst i vitenarkiv
• Sæterbakken, Atle Hole; Stien, Nicolay; Andersen, Vidar; Scott, Suzanne; Cumming, Kristoffer Toldnes & Behm, David G. [Vis alle 8 forfattere av denne artikkelen] (2022). The Effects of Trunk Muscle Training on Physical Fitness and Sport-Specific Performance in Young and Adult Athletes: A Systematic Review and Meta-Analysis. Sports Medicine. ISSN 0112-1642. 52, s. 1599–1622. doi: 10.1007/s40279-021-01637-0. Fulltekst i vitenarkiv
• Wiig, Håvard; Cumming, Kristoffer Toldnes; Handegard, Vilde; Stabell Hansen, Jostein; Spencer, Matthew & Raastad, Truls (2022). Muscular heat shock protein response and muscle damage after semi-professional football match. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 32(6), s. 984–996. doi: 10.1111/sms.14148. Vis sammendrag

  Purpose: A typical football match leads to neuromuscular fatigue and physical performance impairments up to 72–96 h post-match. While muscle damage is thought to be a major factor, damage on the ultrastructural level has never been documented. The purpose of this study was to investigate post-match cellular muscle damage by quantifying the heat shock protein (HSP) response as a proxy for protein damage. Methods: Muscle biopsies, blood samples, countermovement jumps, and perception of muscle soreness were obtained from twelve semi-professional football players 1, 24, 48, and 72 h after a 90-min football match. Muscle biopsies were analyzed for αB-crystallin and HSP70 in the cytosolic and cytoskeletal sub-cellular fractions by Western blotting. Fiber type-specific αB-crystallin and HSP70 staining intensity, and tenascin-C immunoreactivity were analyzed with immunohistochemistry. Blood samples were analyzed for creatine kinase and myoglobin. Results: Within 24 h post-match, a 2.7- and 9.9-fold increase in creatine kinase and myoglobin were observed, countermovement jump performance decreased by −9.7% and muscle soreness increased by 0.68 units. αB-crystallin and HSP70 accumulated in cytoskeletal structures evident by a 3.6- and 1.8-fold increase in the cytoskeletal fraction and a parallel decrease in the cytosolic fraction. In type I and II fibers, αB-crystallin staining intensity increased by 15%–41% and remained elevated at 72 h post-match. Lastly, the percentage of fibers with granular staining of αB-crystallin increased 2.2-fold. Conclusions: Football match play induced a muscular HSP stress response 1–72 h post-match. Specifically, the accumulation of HSPs in cytoskeletal structures and the granular staining of αB-crystallin suggests occurrence of ultrastructural damage. The damage, indicated by the HSP response, might be one reason for the typically 72 h decrease in force-generating capacity after football matches.

• Gjesdal, Beate Eltarvåg; Mæland, Silje; Williams, Gavin; Aaslund, Mona Kristin; Rygh, Cecilie Brekke & Cumming, Kristoffer Toldnes (2021). Can adults with cerebral palsy perform and benefit from ballistic strength training to improve walking outcomes? A mixed methods feasibility study. BMC sports science, medicine and rehabilitation. ISSN 2052-1847. 13. doi: 10.1186/s13102-021-00382-1. Fulltekst i vitenarkiv Vis sammendrag

  Background Power bursts of hips and ankle plantar flexors are prerequisites to walking propulsion. However, these power bursts are reduced during gait for persons with cerebral palsy (CP) and mainly in the ankle plantar flexors. Hence, task specific training, such as ballistic strength training, is suggested to increase muscle power in walking but not investigated in adults with CP. Therefore, the aim was to investigate if adults with CP could perform and benefit from ballistic strength training to improve walking, evaluated through physical measures and self-reported measures and interviews. Methods In this mixed methods feasibility study, eight ambulatory adults (aged 24–56) with spastic CP conducted ballistic strength training on a glideboard targeting the ankle plantarflexors two times a week for eight weeks. The feasibility of the training was assessed through objectives described by Orsmond and Cohn. Before and after the intervention, physical measures (6-Minute Walk Test and the eight-item High-level Mobility Assessment Tool) and self-reported measures (Patient Global Impression of Change, Numeric Pain Rating Scale, Fatigue Impact and Severity Self-Assessment, and Walk-12) were collected. After the intervention, semi-structured interviews explored experiences of this training. Results The participants experienced training the ankle plantar flexor as relevant but reported it took about four weeks to coordinate the exercises successfully. Although we observed no changes in the physical performance measures, most participants reported improvements; some felt steadier when standing, walking, and hopping. Conclusion This study demonstrated that ballistic strength training was feasible and suitable in adults with CP. However, guidance and a long (4 weeks) familiarization time were reported necessary to master the exercises. Most participants reported self-experienced improvements, although no physical performance measures improved. Thus, prolonged intervention may be required for perceived physical improvements to emerge. Also, other outcome measures sensitive to power output remains to be investigated.

• Sæterbakken, Atle Hole; Andersen, Vidar; Behm, David G; Cumming, Kristoffer Toldnes; Prieske, Olaf & Solstad, Tom Erik Jorung [Vis alle 8 forfattere av denne artikkelen] (2021). The role of trunk training for physical fitness and sport-specific performance. Frontiers in Sports and Active Living. ISSN 2624-9367. 3. doi: 10.3389/fspor.2021.625098. Fulltekst i vitenarkiv
• Davids, Charlie J.; Næss, Tore Christian; Moen, Maria; Cumming, Kristoffer Toldnes; Horwath, Oscar & Psilander, Niklas [Vis alle 11 forfattere av denne artikkelen] (2021). Acute cellular and molecular responses and chronic adaptations to low-load blood flow restriction and high-load resistance exercise in trained individuals. Journal of applied physiology. ISSN 8750-7587. doi: 10.1152/japplphysiol.00464.2021. Vis sammendrag

  Blood flow restriction (BFR) with low-load resistance exercise (RE) is often used as a surrogate to traditional high-load RE to stimulate muscular adaptations, such as hypertrophy and strength. However, it is not clear whether such adaptations are achieved through similar cellular and molecular processes. We compared changes in muscle function, morphology and signaling pathways between these differing training protocols. Twenty-one males and females (mean ± SD: 24.3 ± 3.1 years) experienced with resistance training (4.9 ± 2.6 years) performed nine weeks of resistance training (three times per week) with either high-loads (75-80% 1RM; HL-RT), or low-loads with BFR (30-40% 1RM; LL-BFR). Before and after the training intervention, resting muscle biopsies were collected, and quadricep cross-sectional area (CSA), muscular strength and power were measured. Approximately 5 days following the intervention, the same individuals performed an additional 'acute' exercise session under the same conditions, and serial muscle biopsies were collected to assess hypertrophic- and ribosomal-based signaling stimuli. Quadricep CSA increased with both LL-BFR (7.4±4.3%) and HL-RT (4.6±2.9%), with no significant differences between training groups (p=0.37). Muscular strength also increased in both training groups, but with superior gains in squat 1RM occurring with HL-RT (p<0.01). Acute phosphorylation of several key proteins involved in hypertrophy signaling pathways, and expression of ribosomal RNA transcription factors occurred to a similar degree with LL-BFR and HL-RT (all p>0.05 for between-group comparisons). Together, these findings validate low-load resistance training with continuous BFR as an effective alternative to traditional high-load resistance training for increasing muscle hypertrophy in trained individuals.

• Sæterbakken, Atle Hole; Stien, Nicolay; Pedersen, Helene; Solstad, Tom Erik Jorung; Cumming, Kristoffer Toldnes & Andersen, Vidar (2021). The effect of grip width on muscle strength and electromyographic activity in bench press among novice-and resistance-trained men. International Journal of Environmental Research and Public Health (IJERPH). ISSN 1661-7827. 18(12), s. 1–12. doi: 10.3390/ijerph18126444. Fulltekst i vitenarkiv
• Cumming, Kristoffer Toldnes; Kvamme, Nils Helge; Schaad, Laura; Ugelstad, Ingrid & Raastad, Truls (2021). Muscular HSP70 content is higher in elderly compared to young, but is normalized after 12 weeks of strength training. European Journal of Applied Physiology. ISSN 1439-6319. 121(6), s. 1689–1699. doi: 10.1007/s00421-021-04633-4. Fulltekst i vitenarkiv Vis sammendrag

  Purpose: Aging is associated with increased myocellular stress and loss of muscle mass and function. Heat shock proteins (HSPs) are upregulated during periods of stress as part of the cells protective system. Exercise can affect both acute HSP regulation and when repeated regularly counteract unhealthy age-related changes in the muscle. Few studies have investigated effects of exercise on HSP content in elderly. The aim of the study was to compare muscular HSP levels in young and elderly and to investigate how training affects HSP content in muscles from aged males and females. Methods: Thirty-eight elderly were randomized to 12 weeks of strength training (STG), functional strength training (FTG) or a control group (C). To compare elderly to young, 13 untrained young performed 11 weeks of strength training (Y). Muscle biopsies were collected before and after the intervention and analyzed for HSP27, αB-crystallin and HSP70. Results: Baseline HSP70 were 35% higher in elderly than in young, whereas there were no differences between young and elderly in HSP27 or αB-crystallin. After the training intervention, HSP70 were reduced in STG (− 33 ± 32%; P = 0.001) and FTG (− 28 ± 30%; P = 0.012). The decrease in HSP70 was more pronounced in the oldest. In contrast, Y increased HSP27 (134 ± 1%; P < 0.001) and αB-crystallin (84 ± 94%; P = 0.008). Conclusion: Twelve weeks of STG or FTG decreased the initial high levels of HSP70 in aged muscles. Thus, regular strength training can normalize some of the increases in cellular stress associated with normal aging, and lead to a healthier cellular environment in aged muscle cells.

• Andersen, Vidar; Pedersen, Helene; Fimland, Marius Steiro; Shaw, Matthew Peter; Solstad, Tom Erik Jorung & Stien, Nicolay [Vis alle 8 forfattere av denne artikkelen] (2021). Comparison of muscle activity in three single-joint, hip extension exercises in resistance-trained women. Journal of Sports Science and Medicine. ISSN 1303-2968. 20(2), s. 181–187. doi: 10.52082/jssm.2021.181. Fulltekst i vitenarkiv Vis sammendrag

  The aim of the study was to compare neuromuscular activation in the gluteus maximus, the biceps femoris and the erector spinae from the Romanian deadlift, the 45-degree Roman chair back extension and the seated machine back extension. Fifteen resistance-trained females performed three repetitions with 6-RM loading in all exercises in a randomized and counterbalanced order. The activation in the whole movement as well as its lower and upper parts were analyzed. The results showed that the Romanian deadlift and the Roman chair back extension activated the gluteus maximus more than the seated machine back extension (94-140%, p < 0.01). For the biceps femoris the Roman chair elicited higher activation compared to both the Romanian deadlift and the seated machine back extension (71-174%). Further, the Romanian deadlift activated the biceps femoris more compared to the seated machine back extension (61%, p < 0.01). The analyses of the different parts of the movement showed that the Roman chair produced higher levels of activation in the upper part for both the gluteus maximus and the biceps femoris, compared to the other exercises. There were no differences in activation of the erector spinae between the three exercises (p = 1.00). In conclusion, both the Roman deadlift and the Roman chair back extension would be preferable to the seated machine back extension in regards to gluteus maximus activation. The Roman chair was superior in activating the biceps femoris compared to the two other exercises. All three exercises are appropriate selections for activating the lower back muscles. For overall lower limb activation, the Roman chair was the best exercise.

• Peake, Jonathan M.; Markworth, James F.; Cumming, Kristoffer Toldnes; Aas, Sigve Nyvik; Roberts, Llion A. & Raastad, Truls [Vis alle 8 forfattere av denne artikkelen] (2020). The Effects of Cold Water Immersion and Active Recovery on Molecular Factors That Regulate Growth and Remodeling of Skeletal Muscle After Resistance Exercise. Frontiers in Physiology. ISSN 1664-042X. 11. doi: 10.3389/fphys.2020.00737. Fulltekst i vitenarkiv Vis sammendrag

  Regular postexercise cooling attenuates muscle hypertrophy, yet its effects on the key molecular factors that regulate muscle growth and remodeling are not well characterized. In the present study, nine men completed two sessions of single-leg resistance exercise on separate days. On 1 day, they sat in cold water (10°C) up to their waist for 10 min after exercise. On the other day, they exercised at a low intensity for 10 min after exercise. Muscle biopsies were collected from the exercised leg before, 2, 24, and 48 h after exercise in both trials. These muscle samples were analyzed to evaluate changes in genes and proteins involved in muscle growth and remodeling. Muscle-specific RING finger 1 mRNA increased at 2 h after both trials (P < 0.05), while insulin-like growth factor (IGF)-1 Ec, IGF-1 receptor, growth arrest and DNA damage-inducible protein 45, collagen type I alpha chain A, collagen type III alpha chain 1, laminin and tissue inhibitor of metallopeptidase 1 mRNA increased 24−48 h after both trials (P < 0.05). By contrast, atrogin-1 mRNA decreased at all time points after both trials (P < 0.05). Protein expression of tenascin C increased 2 h after the active recovery trial (P < 0.05), whereas FoxO3a protein expression decreased after both trials (P < 0.05). Myostatin mRNA and ubiquitin protein expression did not change after either trial. These responses were not significantly different between the trials. The present findings suggest that regular cold water immersion attenuates muscle hypertrophy independently of changes in factors that regulate myogenesis, proteolysis and extracellular matrix remodeling in muscle after exercise.

• Skattebo, Øyvind; Bjerring, Anders W.; Auensen, Marius; Sarvari, Sebastian; Cumming, Kristoffer Toldnes & Capelli, Carlo [Vis alle 7 forfattere av denne artikkelen] (2020). Blood volume expansion does not explain the increase in peak oxygen uptake induced by 10 weeks of endurance training. European Journal of Applied Physiology. ISSN 1439-6319. 120(5), s. 985–999. doi: 10.1007/s00421-020-04336-2. Fulltekst i vitenarkiv Vis sammendrag

  Purpose: The endurance training (ET)-induced increases in peak oxygen uptake (V˙O2peak) and cardiac output (Q˙peak) during upright cycling are reversed to pre-ET levels after removing the training-induced increase in blood volume (BV). We hypothesised that ET-induced improvements in V˙O2peak and Q˙peak are preserved following phlebotomy of the BV gained with ET during supine but not during upright cycling. Arteriovenous O2 difference (a-v¯O2diff; V˙O2/Q˙), cardiac dimensions and muscle morphology were studied to assess their role for the V˙O2peak improvement. Methods: Twelve untrained subjects (V˙O2peak: 44 ± 6 ml kg−1 min−1) completed 10 weeks of supervised ET (3 sessions/week). Echocardiography, muscle biopsies, haemoglobin mass (Hbmass) and BV were assessed pre- and post-ET. V˙O2peak and Q˙peak during upright and supine cycling were measured pre-ET, post-ET and immediately after Hbmass was reversed to the individual pre-ET level by phlebotomy. Results: ET increased the Hbmass (3.3 ± 2.9%; P = 0.005), BV (3.7 ± 5.6%; P = 0.044) and V˙O2peak during upright and supine cycling (11 ± 6% and 10 ± 8%, respectively; P ≤ 0.003). After phlebotomy, improvements in V˙O2peak compared with pre-ET were preserved in both postures (11 ± 4% and 11 ± 9%; P ≤ 0.005), as was Q˙peak (9 ± 14% and 9 ± 10%; P ≤ 0.081). The increased Q˙peak and a-v¯O2diff accounted for 70% and 30% of the V˙O2peak improvements, respectively. Markers of mitochondrial density (CS and COX-IV; P ≤ 0.007) and left ventricular mass (P = 0.027) increased. Conclusion: The ET-induced increase in V˙O2peak was preserved despite removing the increases in Hbmass and BV by phlebotomy, independent of posture. V˙O2peak increased primarily through elevated Q˙peak but also through a widened a-v¯O2diff, potentially mediated by cardiac remodelling and mitochondrial biogenesis.

• Andersen, Vidar; Pedersen, Helene; Fimland, Marius Steiro; Shaw, Matthew Peter; Solstad, Tom Erik Jorung & Stien, Nicolay [Vis alle 8 forfattere av denne artikkelen] (2020). Acute Effects of Elastic Bands as Resistance or Assistance on EMG, Kinetics, and Kinematics During Deadlift in Resistance-Trained Men. Frontiers in Sports and Active Living. ISSN 2624-9367. doi: 10.3389/fspor.2020.598284. Fulltekst i vitenarkiv Vis sammendrag

  The aim of the study was to compare neuromuscular activation, kinetics and kinematics in three variations of the deadlift: (1) free weights, (2) free weights with elastic bands as resistance (bands anchored to the ground) and (3) free weights with elastic bands as assistance (bands attached above the bar). Sixteen resistance-trained men performed one repetition of the three variations as fast as possible using a 2-repetition maximum load in randomized and counterbalanced order. Muscle activation (gluteus maximus, semitendinosus, biceps femoris, erector spinae, vastus lateralis, and vastus medialis), kinematics (average-, peak-, and time to peak velocity), and kinetics (average-, peak,-and time to peak force) were measured during the ascending movement. Resisted and assisted deadlifts led to higher average and peak force outputs (p < 0.001–0.037, ES = 0.29–0.58), and time to peak velocity was shorter when compared to the free weights deadlift (p = 0.005–0.010, ES = 0.83–1.01). However, peak force was achieved faster when using free weights (p < 0.001, ES = 1.58–2.10) and assisted deadlifts had a lower peak velocity compared to resisted and free weights deadlift (p = 0.004–0.046, ES = 0.43–0.60). There were no significant differences in muscle activation between the different conditions (p = 0.082–1.000). In conclusion, the assisted and resisted deadlift produced higher force when compared to free weights. However, free weight and resisted deadlift seem more favorable for the barbell velocity. These findings are of importance for athletes and coaches which should select exercise depending on the goal of the session.

• Aas, Sigve Nyvik; Breit, Markus; Karsrud, Stian; Aase, Ole Jølle; Rognlien, Simen Helset & Cumming, Kristoffer Toldnes [Vis alle 11 forfattere av denne artikkelen] (2020). Musculoskeletal adaptations to strength training in frail elderly: a matter of quantity or quality? Journal of Cachexia, Sarcopenia and Muscle. ISSN 2190-5991. 11(3), s. 663–677. doi: 10.1002/jcsm.12543. Fulltekst i vitenarkiv Vis sammendrag

  Background: The improvement in muscle strength generally exceeds the increase in muscle size following strength training in frail elderly, highlighting the complex aetiology of strength deficit in aging. The aim of this study was to investigate the effect of heavy‐load strength training on a broad number of factors related to specific strength in frail elderly. Methods: Thirty‐four frail elderly men (n = 18) and women (n = 16) aged 67 to 98 (86 ± 7 years) were randomized to either a group performing strength training twice a week for 10 weeks (ST) or a non‐exercising control group (CON). Knee extensor muscle strength was tested as one‐repetition maximum (1RM) and isometric maximal voluntary contraction (MVC) torque. Muscle activation was assessed by the interpolated twitch technique, and muscle density [mean Hounsfield units (HU)] and intermuscular adipose tissue (IMAT) by computed tomography scans of the quadriceps femoris. Muscle biopsies from the vastus lateralis were obtained to investigate changes in intramyocellular lipids and single‐fibre specific tension. Results: In ST, knee extension 1RM and MVC improved by 17 and 7%, respectively. Muscle cross‐sectional area of the quadriceps femoris increased by 7%, accompanied by a 4% increase of muscle density. No changes in IMAT, voluntary activation level, single‐fibre specific tension, or lipid content were observed. Conclusions: In contrast to several previous reports, the improvements in isometric muscle strength and muscle area were in good agreement in the present study. The training‐induced increase in muscle density was not due to changes in skeletal muscle lipid content. Instead, the increase in muscle density may reflect increased packing of contractile material or simply an increased ratio of muscle tissue relative to IMAT.

• Bårdstu, Hilde Bremseth; Andersen, Vidar; Fimland, Marius Steiro; Aasdahl, Lene; Raastad, Truls & Cumming, Kristoffer Toldnes [Vis alle 7 forfattere av denne artikkelen] (2020). Effectiveness of a resistance training program on physical function, muscle strength, and body composition in community-dwelling older adults receiving home care: A cluster-randomized controlled trial. European Review of Aging and Physical Activity. ISSN 1813-7253. 17. doi: 10.1186/s11556-020-00243-9. Fulltekst i vitenarkiv Vis sammendrag

  Background: Aging is associated with reduced muscle mass and strength leading to impaired physical function. Resistance training programs incorporated into older adults’ real-life settings may have the potential to counteract these changes. We evaluated the effectiveness of 8 months resistance training using easily available, low cost equipment compared to physical activity counselling on physical function, muscle strength, and body composition in community-dwelling older adults receiving home care. Methods: This open label, two-armed, parallel group, cluster randomized trial recruited older adults above 70 years (median age 86.0 (Interquartile range 80–90) years) receiving home care. Participants were randomized at cluster level to the resistance training group (RTG) or the control group (CG). The RTG trained twice a week while the CG were informed about the national recommendations for physical activity and received a motivational talk every 6th week. Outcomes were assessed at participant level at baseline, after four, and 8 months and included tests of physical function (chair rise, 8 ft-up-and-go, preferred- and maximal gait speed, and stair climb), maximal strength, rate of force development, and body composition. Results: Twelve clusters were allocated to RTG (7 clusters, 60 participants) or CG (5 clusters, 44 participants). The number of participants analyzed was 56–64 (6–7 clusters) in RTG and 20–42 (5 clusters) in CG. After 8 months, multilevel linear mixed models showed that RTG improved in all tests of physical function and maximal leg strength (9–24%, p = 0.01–0.03) compared to CG. No effects were seen for rate of force development or body composition. Conclusion: This study show that resistance training using easily available, low cost equipment is more effective than physical activity counselling for improving physical function and maximal strength in community-dwelling older adults receiving home care.

• Wernbom, M.; Paulsen, Gøran; Bjørnsen, Thomas; Cumming, Kristoffer Toldnes & Raastad, Truls (2019). Risk of Muscle Damage With Blood Flow–Restricted Exercise Should Not Be Overlooked. Clinical Journal of Sports Medicine. ISSN 1050-642X. 00(00). doi: 10.1097/JSM.0000000000000755.
• Berntsen, Kristin Schjander; Raastad, Truls; Marstein, Henriette; Kirkhus, Eva Astrid; Merckoll, Else & Cumming, Kristoffer Toldnes [Vis alle 9 forfattere av denne artikkelen] (2019). Functional and Structural Adaptations of Skeletal Muscle in Long-Term Juvenile Dermatomyositis; a Controlled Cross-Sectional Study. Arthritis & Rheumatology. ISSN 2326-5191. doi: 10.1002/art.41174. Fulltekst i vitenarkiv
• Aas, Sigve Nyvik; Hamarsland, Håvard; Cumming, Kristoffer Toldnes; Rognlien, Simen Helset; Aase, Ole Jølle & Nordseth, Martin [Vis alle 11 forfattere av denne artikkelen] (2019). The impact of age and frailty on skeletal muscle autophagy markers and T specific strength: A cross-sectional comparison. Experimental Gerontology. ISSN 0531-5565. 125. doi: 10.1016/j.exger.2019.110687. Vis sammendrag

  Aging is associated with reduced specific strength, defined as strength normalized to the cross-sectional area of a given muscle or muscle group. Dysregulated autophagy, impairing removal of dysfunctional proteins and organelles, is suggested as one of the underlying mechanisms. The aim of this study was to investigate levels of autophagic markers in skeletal muscle in groups known to differ in specific strength. Sixty-two volunteers were assigned to the following study groups: young, old non-frail, old pre-frail, and old frail individuals. Leg lean mass was assessed with dual-energy X-ray absorptiometry and quadriceps femoris muscle strength by isometric maximal voluntary contraction. The abundance of autophagic proteins within skeletal muscle cytosolic and membrane sub-fractions were determined by western blotting. In addition, the level of heat shock proteins and proteins involved in the regulation of protein synthesis were measured. The abundance of LC3-I was higher in old frail compared to young individuals. If the three elderly groups were pooled, the level of LC3-II was higher in old compared to young subjects. Pre-frail and frail elderly also displayed higher levels of certain heat shock proteins. No between-group differences were observed for p62, LC3-II/LC3-I ratio, or any of the anabolic signaling molecules. A negative correlation was observed between cytosolic LC3-I and specific strength. Higher levels of LC3-I in the frail elderly might represent attenuated autophagosome formation. However, higher LC3-II levels indicate an increased abundance of autophagosomes. These findings may therefore imply that both the process of autophagosome formation and autophagosome-lysosome fusion are affected in frail elderly. Higher levels of heat shock proteins might represent an auto-protective mechanism against increased levels of misfolded proteins, possibly due to inefficient degradation. In conclusion, the reduction in specific strength with aging and frailty may partly be caused by alterations in muscle protein quality control.

• Psilander, Niklas; Eftestøl, Einar; Cumming, Kristoffer Toldnes; Solgård, Inga Juvkam; Ekblom, Maria M. & Sunding, Kerstin [Vis alle 12 forfattere av denne artikkelen] (2019). Effects of training, detraining, and retraining on strength, hypertrophy, and myonuclear number in human skeletal muscle. Journal of applied physiology. ISSN 8750-7587. 126(6), s. 1636–1645. doi: 10.1152/japplphysiol.00917.2018. Fulltekst i vitenarkiv Vis sammendrag

  Previously trained mouse muscles acquire strength and volume faster than naïve muscles; it has been suggested that this is related to increased myonuclear density. The present study aimed to determine whether a previously strength-trained leg (mem-leg) would respond better to a period of strength training than a previously untrained leg (con-leg). Nine men and 10 women performed unilateral strength training (T1) for 10 wk, followed by 20 wk of detraining (DT) and a 5-wk bilateral retraining period (T2). Muscle biopsies were taken before and after each training period and analyzed for myonuclear number, fiber volume, and cross-sectional area (CSA). Ultrasound and one repetition of maximum leg extension were performed to determine muscle thickness (MT) and strength. CSA (~17%), MT (~10%), and strength (~20%) increased during T1 in the mem-leg. However, the myonuclear number and fiber volume did not change. MT and CSA returned to baseline values during DT, but strength remained elevated (~60%), supporting previous findings of a long-lasting motor learning effect. MT and strength increased similarly in the mem-leg and con-leg during T2, whereas CSA, fiber volume, and myonuclear number remained unaffected. In conclusion, training response during T2 did not differ between the mem-leg and con-leg. However, this does not discount the existence of human muscle memory, since no increase in the number of myonuclei was detected during T1 and no clear detraining effect was observed for cell size during DT; thus, the present data did not allow for a rigorous test of the muscle memory hypothesis.

• Andersen, Vidar; Fimland, Marius Steiro; Cumming, Kristoffer Toldnes; Vraalsen, Øyvind Fougli & Sæterbakken, Atle Hole (2018). Explosive Resistance Training Using Elastic Bands in Young Female Team Handball Players. Sports Medicine International Open. ISSN 2367-1890. 2(6), s. E171–E178. doi: 10.1055/a-0755-7398. Fulltekst i vitenarkiv Vis sammendrag

  The aim of the study was to examine the effects of full-body elastic resistance band training in young female team handball players. 12 players (16.5±0.7 years, 166±5.0cm, 65.9±8.8kg) completed an 11-week control period followed by a 9-week elastic resistance band training period. The training program, consisting of 6 exercises, was incorporated into the teams’ regular handball training sessions 3 times per week. Each exercise was performed with 3 sets of 6–10 explosive repetitions (5–9 on the Borg CR10 Scale®). The maximal power output in squat and bench press, jump height, throwing velocity and repeated agility run was tested before and after the control and training periods. The elastic resistance band period had greater improvement vs. the control period for countermovement jump with or without arm swing (10% vs. –6 to –2%) and power output at lighter loads (10 to 12 % vs. –6 to 0 %). For the 3 throwing velocity tests, there were tendencies towards increased velocity in the elastic resistance band period compared to the control period (p = 0.07–0.10). For the repeated agility run, there was a reduction in the mean and fastest time compared to the training period (2 to 3% vs. –1 to 1%). In conclusion, a brief, elastic resistance band training program, incorporated into the regular handball training sessions, improved explosive lower-limb performance in young female handball players more than handball training alone.

• Cumming, Kristoffer Toldnes; Raastad, Truls; Sørstrøm, Andreas Natvig; Paronetto, Maria Paola; Mercatelli, Neri & Ugelstad, Ingrid [Vis alle 8 forfattere av denne artikkelen] (2017). Vitamin C and E supplementation does not affect heat shock proteins or endogenous antioxidants in trained skeletal muscles during 12 weeks of strength training. BMC Nutrition. ISSN 2055-0928. 3. doi: 10.1186/s40795-017-0185-8. Fulltekst i vitenarkiv Vis sammendrag

  Background: Supplementation with large doses of antioxidants, such as vitamin C and E, has been shown to blunt some adaptations to endurance training. The effects of antioxidant supplementation on adaptations to strength training is sparsely studied. Herein we investigated the effects of vitamin C and E supplementation on acute stress responses to exercise and adaptation to traditional heavy load strength training. Methods: In a double blind placebo-controlled design, twenty-eight, young, trained males and females were randomly assigned to receive either vitamin C and E (C: 1000 mg, E: 235 mg, per day) or placebo supplements, and underwent strength training for 10 weeks. After five weeks, a subgroup conducted a strength training session to investigate acute stress responses. Muscle samples were obtained to investigate changes in stress responses and in proteins and mRNA related to the heat shock proteins (HSPs) or antioxidant enzymes. Results: The acute responses to the exercise session revealed activation of the NFκB pathway indicated by degradation of IκBα in both groups. Vitamin C and E supplementation had, however, no effects on the acute stress responses. Furthermore, ten weeks of strength training did not change muscle αB-crystallin, HSP27, HSP70, GPx1 or mnSOD levels, with no influence of supplementation. Conclusions: Our results showed that although vitamin C and E supplementation has been shown to interfere with training adaptations, it did not affect acute stress responses or long-term training adaptations in the HSPs or antioxidant enzymes in this study.

• Rustad, Per Inge; Sailer, Manuela; Cumming, Kristoffer Toldnes; Jeppesen, Per Bendix; Kolnes, Kristoffer Jensen & Sollie, Ove [Vis alle 10 forfattere av denne artikkelen] (2016). Intake of protein plus carbohydrate during the first two hours after exhaustive cycling improves performance the following day. PLOS ONE. ISSN 1932-6203. 11:e0153229(4). doi: 10.1371/journal.pone.0153229. Vis sammendrag

  Intake of protein immediately after exercise stimulates protein synthesis but improved recovery of performance is not consistently observed. The primary aim of the present study was to compare performance 18 h after exhaustive cycling in a randomized diet-controlled study (175 kJ·kg-1 during 18 h) when subjects were supplemented with protein plus carbohydrate or carbohydrate only in a 2-h window starting immediately after exhaustive cycling. The second aim was to investigate the effect of no nutrition during the first 2 h and low total energy intake (113 kJ·kg-1 during 18 h) on performance when protein intake was similar. Eight endurance-trained subjects cycled at 237±6 Watt (~72% VO2max) until exhaustion (TTE) on three occasions, and supplemented with 1.2 g carbohydrate·kg-1·h-1 (CHO), 0.8 g carbohydrate + 0.4 g protein·kg-1·h-1 (CHO+PRO) or placebo without energy (PLA). Intake of CHO+PROT increased plasma glucose, insulin, and branch chained amino acids, whereas CHO only increased glucose and insulin. Eighteen hours later, subjects performed another TTE at 237±6 Watt. TTE was increased after intake of CHO+PROT compared to CHO (63.5±4.4 vs 49.8±5.4 min; p<0.05). PLA reduced TTE to 42.8±5.1 min (p<0.05 vs CHO). Nitrogen balance was positive in CHO+PROT, and negative in CHO and PLA. In conclusion, performance was higher 18 h after exhaustive cycling with intake of CHO+PROT compared to an isocaloric amount of carbohydrate during the first 2 h post exercise. Intake of a similar amount of protein but less carbohydrate during the 18 h recovery period reduced performance.

• Cumming, Kristoffer Toldnes; Ellefsen, Stian; Rønnestad, Bent; Ugelstad, Ingrid & Raastad, Truls (2016). Acute and long-term effects of blood flow restricted training on heat shock proteins and endogenous antioxidant systems. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 27(11), s. 1190–1201. doi: 10.1111/sms.12774. Vis sammendrag

  Blood flow restricted exercise (BFRE) with low loads has been demonstrated to induce considerable stress to exercising muscles. Muscle cells have developed a series of defensive systems against exercise-induced stress. However, little is known about acute and long-term effects of BFRE training on these systems. Nine previously untrained females trained low-load BFRE and heavy load strength training (HLS) on separate legs and on separate days to investigate acute and long-term effects on heat shock proteins (HSP) and endogenous antioxidant systems in skeletal muscles. BFRE and HLS increased muscle strength similarly by 12 ± 7% and 12 ± 6%, respectively, after 12 weeks of training. Acutely after the first BFRE and HLS exercise session, αB-crystallin and HSP27 content increased in cytoskeletal structures, accompanied by increased expression of several HSP genes. After 12 weeks of training, this acute HSP response was absent. Basal levels of αB-crystallin, HSP27, HSP70, mnSOD, or GPx1 remained unchanged after 12 weeks of training, but HSP27 levels increased in the cytoskeleton. Marked translocation of HSP to cytoskeletal structures at the commencement of training indicates that these structures are highly stressed from BFRE and HLS. However, as the muscle gets used to this type of exercise, this response is abolished.

• Ellefsen, Stian; Hammarström, Daniel; Strand, Tor; Zacharoff, Erika; Whist, Jon Elling & Rauk, Irene [Vis alle 14 forfattere av denne artikkelen] (2015). Blood flow-restricted strength training displays high functional and biological efficacy in women: a within-subject comparison with high-load strength training. American Journal of Physiology. Regulatory Integrative and Comparative Physiology. ISSN 0363-6119. 309(7), s. R767–R779. doi: 10.1152/ajpregu.00497.2014. Vis sammendrag

  Limited data exist on the efficacy of low-load blood flow-restricted strength training (BFR), as compared directly to heavy-load strength training (HST). Here, we show that 12 wk of twice-a-week unilateral BFR [30% of one repetition maximum (1RM) to exhaustion] and HST (6-10RM) of knee extensors provide similar increases in 1RM knee extension and cross-sectional area of distal parts of musculus quadriceps femoris in nine untrained women (age 22 ± 1 yr). The two protocols resulted in similar acute increases in serum levels of human growth hormone. On the cellular level, 12 wk of BFR and HST resulted in similar shifts in muscle fiber composition in musculus vastus lateralis, evident as increased MyHC2A proportions and decreased MyHC2X proportions. They also resulted in similar changes of the expression of 29 genes involved in skeletal muscle function, measured both in a rested state following 12 wk of training and subsequent to singular training sessions. Training had no effect on myonuclei proportions. Of particular interest, 1) gross adaptations to BFR and HST were greater in individuals with higher proportions of type 2 fibers, 2) both BFR and HST resulted in approximately four-fold increases in the expression of the novel exercise-responsive gene Syndecan-4, and 3) BFR provided lesser hypertrophy than HST in the proximal half of musculus quadriceps femoris and also in CSApeak, potentially being a consequence of pressure from the tourniquet utilized to achieve blood flow restriction. In conclusion, BFR and HST of knee extensors resulted in similar adaptations in functional, physiological, and cell biological parameters in untrained women.

• Paulsen, Gøran; Hamarsland, Håvard; Cumming, Kristoffer Toldnes; Johansen, Rasmus Einar; Hulmi, Juha J. & Børsheim, Elisabet [Vis alle 9 forfattere av denne artikkelen] (2014). Vitamin C and E supplementation alters protein signalling after a strength training session, but not muscle growth during 10 weeks of training. Journal of Physiology. ISSN 0022-3751. 592(24), s. 5391–5408. doi: 10.1113/jphysiol.2014.279950. Vis sammendrag

  This study investigated the effects of vitamin C and E supplementation on acute responses and adaptations to strength training. Thirty-two recreationally strength-trained men and women were randomly allocated to receive a vitamin C and E supplement (1000 mg day−1 and 235 mg day−1, respectively), or a placebo, for 10 weeks. During this period the participants’ training involved heavy-load resistance exercise four times per week. Muscle biopsies from m. vastus lateralis were collected, and 1 repetition maximum (1RM) and maximal isometric voluntary contraction force, body composition (dual-energy X-ray absorptiometry), and muscle cross-sectional area (magnetic resonance imaging) were measured before and after the intervention. Furthermore, the cellular responses to a single exercise session were assessed midway in the training period by measurements of muscle protein fractional synthetic rate and phosphorylation of several hypertrophic signalling proteins. Muscle biopsies were obtained from m. vastus lateralis twice before, and 100 and 150 min after, the exercise session (4 × 8RM, leg press and knee-extension). The supplementation did not affect the increase in muscle mass or the acute change in protein synthesis, but it hampered certain strength increases (biceps curl). Moreover, increased phosphorylation of p38 mitogen-activated protein kinase, Extracellular signal-regulated protein kinases 1 and 2 and p70S6 kinase after the exercise session was blunted by vitamin C and E supplementation. The total ubiquitination levels after the exercise session, however, were lower with vitamin C and E than placebo. We concluded that vitamin C and E supplementation interfered with the acute cellular response to heavy-load resistance exercise and demonstrated tentative long-term negative effects on adaptation to strength training.

• Paulsen, Gøran; Cumming, Kristoffer Toldnes; Hamarsland, Håvard; Børsheim, Elisabeth; Berntsen, Sveinung & Raastad, Truls (2014). Can supplementation with vitamin C and E alter physiological adaptations to strength training? BMC sports science, medicine and rehabilitation. ISSN 2052-1847. 6(1). doi: 10.1186/2052-1847-6-28. Vis sammendrag

  Background: Antioxidant supplementation has recently been demonstrated to be a double-edged sword, because small to moderate doses of exogenous antioxidants are essential or beneficial, while high doses may have adverse effects. The adverse effects can be manifested in attenuated effects of exercise and training, as the antioxidants may shut down some redox-sensitive signaling in the exercised muscle fibers. However, conditions such as age may potentially modulate the need for antioxidant intake. Therefore, this paper describes experiments for testing the hypothesis that high dosages of vitamin C (1000 mg/day) and E (235 mg/day) have negative effects on adaptation to resistance exercise and training in young volunteers, but positive effects in older men. Methods/design: We recruited a total of 73 volunteers. The participants were randomly assigned to receiving either vitamin C and E supplementation or a placebo. The study design was double-blinded, and the participants followed an intensive training program for 10 – 12 weeks. Tests and measurements aimed at assessing changes in physical performance (maximal strength) and physiological characteristics (muscle mass), as well as biochemical and cellular systems and structures (e.g., cell signaling and morphology). Discussion: Dietary supplements, such as vitamin C and E, are used by many people, especially athletes. The users often believe that high dosages of supplements improve health (resistance to illness and disease) and physical performance. These assumptions are, however, generally not supported in the scientific literature. On the contrary, some studies have indicated that high dosages of antioxidant supplements have negative effects on exercise-induced adaptation processes. Since this issue concerns many people and few randomized controlled trials have been conducted in humans, further studies are highly warranted.

• Cumming, Kristoffer Toldnes; Raastad, Truls; Holden, Geir; Bastani, Nasser Ezzatkhah; Schneeberger, Damaris & Paronetto, Maria Paola [Vis alle 12 forfattere av denne artikkelen] (2014). Effects of vitamin C and E supplementation on endogenous antioxidant systems and heat shock proteins in response to endurance training. Physiological Reports. ISSN 2051-817X. 2(10). doi: 10.14814/phy2.12142. Vis sammendrag

  Reactive oxygen and nitrogen species are important signal molecules for adaptations to training. Due to the antioxidant properties of vitamin C and E, supplementation has been shown to blunt adaptations to endurance training. In this study, we investigated the effects of vitamin C and E supplementation and endurance training on adaptations in endogenous antioxidants and heat shock proteins (HSP). Thirty seven males and females were randomly assigned to receive Vitamin C and E (C + E; C: 1000 mg, E: 235 mg daily) or placebo (PLA), and underwent endurance training for 11 weeks. After 5 weeks, a subgroup conducted a high intensity interval session to investigate acute stress responses. Muscle and blood samples were obtained to investigate changes in proteins and mRNA related to the antioxidant and HSP system. The acute response to the interval session revealed no effects of C + E supplementation on NFκB activation. However, higher stress responses to exercise in C + E group was indicated by larger translocation of HSPs and a more pronounced gene expression compared to PLA. Eleven weeks of endurance training decreased muscle GPx1, HSP27 and αB‐crystallin, while mnSOD, HSP70 and GSH remained unchanged, with no influence of supplementation. Plasma GSH increased in both groups, while uric acid decreased in the C + E group only. Our results showed that C + E did not affect long‐term training adaptations in the antioxidant‐ and HSP systems. However, the greater stress responses to exercise in the C + E group might indicate that long‐term adaptations occurs through different mechanisms in the two groups.

• Cumming, Kristoffer Toldnes; Paulsen, Gøran; Wernbom, Mathias; Ugelstad, Ingrid & Raastad, Truls (2014). Acute response and subcellular movement of HSP27, αB-crystallin and HSP70 in human skeletal muscle after blood-flow-restricted low-load resistance exercise. Acta Physiologica. ISSN 1748-1708. 211(4), s. 634–646. doi: 10.1111/apha.12305. Vis sammendrag

  Aim: Heat-shock proteins (HSP) are important chaperones for stressed and damaged proteins. Low-load blood-flow-restricted resistance exercise (BFRE) is generally believed not to induce significant muscle damage, but is hitherto unverified with intracellular markers. Consequently, the aim of this study was to investigate the HSP response after BFRE in human skeletal muscle. Methods: Nine healthy volunteers performed five sets to failure of unilateral knee extension at 30% of 1RM with partial blood-flow restriction. The contralateral leg performed the same work with free blood flow. Muscle biopsies were collected before exercise, 1, 24 and 48 h after exercise and analysed for HSP27, αB-crystallin, HSP70, desmin, glycogen content and myosin heavy chain by immunohistochemistry, ELISA and western blotting. Results: One hour after exercise, HSP27 and αB-crystallin levels were reduced in the cytosolic and increased in the cytoskeletal fraction in the BFRE leg. HSP70 showed a delayed response and was increased over 48 h in the BFRE leg. Immunohistochemical analyses showed higher staining intensity of HSP70 in type 1 fibres in the BFRE leg at 24 and 48 h post-exercise. PAS staining showed decreased glycogen levels after BFRE, and interestingly, glycogen was still depleted 48 h after exercise in the same fibres displaying high HSP70 staining (type 1 fibres). Conclusion: Translocation of HSP27 and αB-crystallin from cytosol to cytoskeletal structures indicates that cytoskeletal proteins are stressed during BFRE. However, overt signs of myofibrillar disruptions were not observed. Interestingly, the stress response was more pronounced in type 1 than in type 2 fibres and coincided with low glycogen levels.

• Paulsen, Gøran; Cumming, Kristoffer T.; Holden, Geir; Hallén, Jostein; Rønnestad, Bent & Sveen, Ole [Vis alle 19 forfattere av denne artikkelen] (2014). Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind randomized controlled trial. Journal of Physiology. ISSN 0022-3751. 592(8), s. 1887–1901. doi: 10.1113/jphysiol.2013.267419. Vis sammendrag

  In this double-blind, randomised, controlled trial, we investigated the effects of vitamin C and E supplementation on endurance training adaptations in humans. Fifty-four young men and women were randomly allocated to receive either 1000 mg of vitamin C and 235 mg of vitamin E or a placebo daily for 11 weeks. During supplementation, the participants completed an endurance training programme consisting of three to four sessions per week (primarily of running), divided into high-intensity interval sessions [4-6 × 4-6 min; >90% of maximal heart rate (HRmax)] and steady state continuous sessions (30-60 min; 70-90% of HRmax). Maximal oxygen uptake (VO2 max ), submaximal running and a 20 m shuttle run test were assessed and blood samples and muscle biopsies were collected, before and after the intervention. Participants in the vitamin C and E group increased their VO2 max (mean ± s.d.: 8 ± 5%) and performance in the 20 m shuttle test (10 ± 11%) to the same degree as those in the placebo group (mean ± s.d.: 8 ± 5% and 14 ± 17%, respectively). However, the mitochondrial marker cytochrome c oxidase subunit IV (COX4) and cytosolic peroxisome proliferator-activated receptor-γ coactivator 1 α (PGC-1α) increased in the m. vastus lateralis in the placebo group by 59 ± 97% and 19 ± 51%, respectively, but not in the vitamin C and E group (COX4: -13 ± 54%; PGC-1α: -13 ± 29%; P ≤ 0.03, between groups). Furthermore, mRNA levels of CDC42 and mitogen-activated protein kinase 1 (MAPK1) in the trained muscle were lower in the vitamin C and E group than in the placebo group (P ≤ 0.05). Daily vitamin C and E supplementation attenuated increases in markers of mitochondrial biogenesis following endurance training. However, no clear interactions were detected for improvements in VO2 max and running performance. Consequently, vitamin C and E supplementation hampered cellular adaptations in the exercised muscles, and although this did not translate to the performance tests applied in this study, we advocate caution when considering antioxidant supplementation combined with endurance exercise.

• Lin, Fang-Chin; Bolling, Astrid; Stuenæs, Jorid Thrane; Cumming, Kristoffer T.; Ingvaldsen, Ada & Lai, Yu-Chiang [Vis alle 8 forfattere av denne artikkelen] (2012). Effect of insulin and contraction on glycogen synthase phosphorylation and kinetic properties in epitrochlearis muscles from lean and obese Zucker rats. American Journal of Physiology - Cell Physiology. ISSN 0363-6143. 302(10), s. C1539–C1547. doi: 10.1152/ajpcell.00430.2011. Vis sammendrag

  In the present study, the effects of insulin and contraction on glycogen synthase (GS) kinetic properties and phosphorylation were investigated in epitrochlearis muscles from lean and obese Zucker rats. Total GS activity and protein expression were ∼15% lower in epitrochlearis from obese rats compared with lean rats. Insulin-stimulated GS fractional activity and affinity for UDP-glucose were lower (higher Km) in muscles from obese rats. GS Ser641 and Ser645,649,653,657 phosphorylation was higher in insulin-stimulated muscles from obese rats, which agreed with lower GS activation. Contraction-mediated GS dephosphorylation of Ser641, Ser641+645, Ser645,649,653,657, and Ser7+10 was normal in muscles from obese Zucker rats, and GS fractional activity increased to similar levels in epitrochlearis muscles from lean and obese rats. GS affinity for UDP glucose was ∼0.8, ∼0.4, and ∼0.1 mM with assay buffers containing 0, 0.17, and 12 mM glucose 6-phosphate, respectively. Contraction increased affinity for UDP-glucose (reduced Km) at a physiological concentration of glucose 6-phosphate (0.17 mM) to ∼0.2 mM in muscles from both lean and obese rats. Interestingly, in the absence of glucose 6-phosphate in the assay buffer, contraction (and insulin) did not influence GS affinity for UDP-glucose, indicating that affinity is regulated by sensitivity for glucose 6-phosphate. In conclusion, contraction-mediated activation and dephosphorylation of GS were normal in muscles from obese Zucker rats, whereas insulin-mediated GS activation and dephosphorylation were impaired.

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• Mølmen, Knut Sindre; Cumming, Kristoffer Toldnes; Wang, Eivind & Solberg, Trine (2023). Gå eller løpe? : dette sier forskningen. [Avis]. Nettavisen pluss.
• Bjørnsen, Thomas; Hody, Stephanie; Raastad, Truls; Paulsen, Gøran; Wernbom, Mathias & Vårvik, Fredrik Tonstad [Vis alle 8 forfattere av denne artikkelen] (2022). High-Frequency Blood Flow Restricted Resistance Exercise To Failure Induces Higher Cellular Stress In Muscle Fibres Than A Non-Failure Protocol .
• Vikmoen, Olav; Teien, Hilde Kristin; Aandstad, Anders; Lander, Elise; Cumming, Kristoffer Toldnes & Helkala, Kirsi Marjaana (2021). Sex Differences in Changes in Body Composition, Physical Performance, and Muscle Fibers After a Strenuous Military Field Exercise.
• Wernbom, Mathias; Paulsen, Gøran; Bjørnsen, Thomas; Cumming, Kristoffer Toldnes & Raastad, Truls (2021). Reply - Letter to the editor. Clinical Journal of Sports Medicine. ISSN 1050-642X. 31(6), s. e513–e513. doi: 10.1097/JSM.0000000000000854.
• Bårdstu, Hilde; Andersen, Vidar; Fimland, Marius Steiro; Aasdahl, Lene; Raastad, Truls & Cumming, Kristoffer Toldnes [Vis alle 7 forfattere av denne artikkelen] (2020). Erratum: Effectiveness of a resistance training program on physical function, muscle strength, and body composition in community-dwelling older adults receiving home care: A cluster-randomized controlled trial (European Review of Aging and Physical Activity (2020) 17 (11) DOI: 10.1186/s11556-020-00243-9). European Review of Aging and Physical Activity. ISSN 1813-7253. 17(1). doi: 10.1186/s11556-020-00245-7.
• Wernbom, Mathias; Schoenfeld, Brad J; Paulsen, Gøran; Bjørnsen, Thomas; Cumming, Kristoffer Toldnes & Aagaard, Per [Vis alle 8 forfattere av denne artikkelen] (2020). Commentary: Can Blood Flow Restricted Exercise Cause Muscle Damage? Commentary on Blood Flow Restriction Exercise: Considerations of Methodology, Application, and Safety. Frontiers in Physiology. ISSN 1664-042X. 11. doi: 10.3389/fphys.2020.00243.
• Cumming, Kristoffer Toldnes (2020). Unngå formtap med enkle grep. [Internett]. NHI.no.
• Indrebø-Langlo, Marlene & Cumming, Kristoffer Toldnes (2019). Sliter du med fremgang på styrketreningen? Dette gjør du kanskje feil. [Avis]. Aftenposten/SPREK.
• Westeng, Kjersti & Cumming, Kristoffer Toldnes (2019). Det finnes mange måter å måle din fysiske form på, men som med mye annet gjelder følgende: Det enkle er ofte det beste. [Internett]. Nettavisen.no.
• Westeng, Kjersti & Cumming, Kristoffer Toldnes (2019). Dette avgjør hvor god fysisk form du er i. [Internett]. Nettavisen.no.
• Cumming, Kristoffer Toldnes (2019). Ny studie: Femten minutters trening tre ganger i uken ga stor helseeffekt. [Internett]. Nettavisen.no.
• Cumming, Kristoffer Toldnes (2019). Dette skjer med formen om du dropper trening i ferien. [Avis]. Aftenposten/SPREK.
• Eftestøl, Einar; Psilander, Niklas; Cumming, Kristoffer Toldnes; Juvkam, Inga; Ekblom, Maria M. & Sunding, Kerstin [Vis alle 12 forfattere av denne artikkelen] (2019). Muscle memory: Are myonuclei ever lost? Journal of applied physiology. ISSN 8750-7587. 128(2), s. 456–457. doi: 10.1152/japplphysiol.00761.2019.
• Dyregrov, Silje & Cumming, Kristoffer Toldnes (2018). Nytt treningskonsept: Gir pengene tilbake hvis ikke kundene får effekt. - Dette er det mest geniale som er laget i styrketreningsbransjen. . [Internett]. Aftenposten/SPREK.
• Minge, Anders & Cumming, Kristoffer Toldnes (2018). Dette tjener du på å løpe i trapper. [Internett]. Stavanger Aftenblad/SPREK.
• Kurth, Maria & Cumming, Kristoffer Toldnes (2018). Dette skjer i kroppen når du trener for mye. [Internett]. Side2/Shapeup.
• Bakken, Benedicte & Cumming, Kristoffer Toldnes (2018). Mette (32) har blitt både sterkere og fått bedre kondis med denne treningen. Slik gjør du det. [Internett]. Aftenposten/SPREK.
• Cumming, Kristoffer Toldnes (2018). NIH-forsker: - All forskning viser at det er nærmest umulig å trene seg slank. [Internett]. Nettavisen.no.
• Wikan, Magnus; Bøyum, Kim & Cumming, Kristoffer Toldnes (2017). Så raskt mister du formen når du stopper å trene. Hva skjer med utholdenheten og musklene hvis du dropper trening i to til fire uker? . [Internett]. Aftenposten/SPREK.
• Cumming, Kristoffer Toldnes & Raastad, Truls (2017). Musklene husker gammel storhetstid. Forskning.no. ISSN 1891-635X.
• Holth Hansen, Anette & Cumming, Kristoffer Toldnes (2017). Å komme i form trenger ikke være så vanskelig. [Internett]. nrk.no.
• Cumming, Kristoffer Toldnes (2016). Bør du trene når du er støl? [Internett]. forskning.no.
• Ellefsen, Stian; Hammarström, Daniel; Strand, Tor A; Nygård, Håvard; Whist, Jon Elling & Vegge, Geir [Vis alle 9 forfattere av denne artikkelen] (2015). Effects of Blood Flow-Restricted Strength Training and High-Load Strength Training on Muscular Endurance Characteristics.
• Johansen, Andreas Birger & Cumming, Kristoffer Toldnes (2014). Bra for muskelcellen at du løper. [Internett]. forskning.no.
• Ellefsen, Stian; Hammarström, Daniel; Vegge, Geir; Rønnestad, Bent; Whist, Jon Elling & Strand, T.A. [Vis alle 10 forfattere av denne artikkelen] (2014). The functional and biological efficacy of blood flowrestricted strength training in untrained women.
• Cumming, Kristoffer T. (2012). Acute Effects Of Resistance Exercise With Blood Flow Restriction On HSP70 Response In Humans. Medicine & Science in Sports & Exercise. ISSN 0195-9131. 44, s. 200–200.
• Andersen, Vidar; Cumming, Kristoffer T.; Kvamme, Nils Helge; Solberg, Paul Andre; Tomten, Sissel Erland & Hallén, Jostein [Vis alle 7 forfattere av denne artikkelen] (2009). The effect of three different training modalities on muscle strength, muscle mass and physical function, among older people.

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