Daniel Hammarström

• Lian, Kristian; Hammarström, Daniel; Hamarsland, Håvard; Mølmen, Knut Sindre; Moen, Sara Christine & Ellefsen, Stian (2024). Glucose ingestion before and after resistance training sessions does not augment ribosome biogenesis in healthy moderately trained young adults. European Journal of Applied Physiology. ISSN 1439-6319. doi: 10.1007/s00421-024-05446-x.
• Lundby, Carsten; Hamarsland, Håvard; Hansen, Joar; Bjørndal, Hege; Berge, Simen Næss & Hammarström, Daniel [Vis alle 7 forfattere av denne artikkelen] (2023). Hematological, skeletal muscle fiber, and exercise performance adaptations to heat training in elite female and male cyclists. Journal of applied physiology. ISSN 8750-7587. 135(1), s. 217–226. doi: 10.1152/japplphysiol.00115.2023. Vis sammendrag

  Heat exercise training may increase exercise performance in athletes. The underlying mechanisms remain partly unresolved, and it is unknown if female and male athletes may experience comparable gains. The aims were to investigate whether heat training (HEAT) increases hemoglobin mass (Hbmass), skeletal muscle fiber characteristics, and thermoneutral exercise performance in elite female and male endurance athletes. Female (n = 20; V̇o2max = 58.2 ± 6.7 mL·min−1·kg−1) and male (n = 27; V̇o2max = 76.4 ± 7.8 mL·min−1·kg−1) cyclists were studied before and after 5 wk of randomized control or HEAT consisting of five weekly sessions each of 50 min duration, which were included in their normal training regimes. Overall, the observed relative responses to HEAT were largely similar in female and male study participants. HEAT increased (P < 0.05) Hbmass in females from 650 ± 77 to 675 ± 76 g (4.0 ± 1.6%) and from 1,008 ± 155 to 1,041 ± 147 g (3.5 ± 2.3%) in males. In contrast, skeletal muscle citrate synthase activity, fiber type distribution, and capillary density remained unchanged with HEAT. Lactate threshold, V̇o2max, and mean power output during 15-min all-out testing were all enhanced (P < 0.05) following HEAT in female and male study participants. In conclusion, 5 wk of HEAT increases Hbmass in female and male elite cyclists and improves exercise performance in a thermoneutral environment. Based on this, heat training may be recommended to elite female and male athletes aiming to perform in a thermoneutral environment. NEW & NOTEWORTHY We demonstrate in elite female and male cyclists that heat exercise training (5 × 50 min sessions/wk for 5 wk) facilities Hbmass and other hematological parameters more than control exercise training, whereas skeletal muscle properties remain unaltered. Collectively, this coincided with improvements in lactate threshold, V̇o2max, and 15-min all-out cycling performance.

• Khan, Yusuf; Hammarström, Daniel; Ellefsen, Stian & Ahmad, Rafi (2022). Normalization of gene expression data revisited: the three viewpoints of the transcriptome in human skeletal muscle undergoing load-induced hypertrophy and why they matter. BMC Bioinformatics. ISSN 1471-2105. 23(1). doi: 10.1186/s12859-022-04791-y. Fulltekst i vitenarkiv Vis sammendrag

  Background The biological relevance and accuracy of gene expression data depend on the adequacy of data normalization. This is both due to its role in resolving and accounting for technical variation and errors, and its defining role in shaping the viewpoint of biological interpretations. Still, the choice of the normalization method is often not explicitly motivated although this choice may be particularly decisive for conclusions in studies involving pronounced cellular plasticity. In this study, we highlight the consequences of using three fundamentally different modes of normalization for interpreting RNA-seq data from human skeletal muscle undergoing exercise-training-induced growth. Briefly, 25 participants conducted 12 weeks of high-load resistance training. Muscle biopsy specimens were sampled from m. vastus lateralis before, after two weeks of training (week 2) and after the intervention (week 12), and were subsequently analyzed using RNA-seq. Transcript counts were modeled as (1) per-library-size, (2) per-total-RNA, and (3) per-sample-size (per-mg-tissue). Result Initially, the three modes of transcript modeling led to the identification of three unique sets of stable genes, which displayed differential expression profiles. Specifically, genes showing stable expression across samples in the per-library-size dataset displayed training-associated increases in per-total-RNA and per-sample-size datasets. These gene sets were then used for normalization of the entire dataset, providing transcript abundance estimates corresponding to each of the three biological viewpoints (i.e., per-library-size, per-total-RNA, and per-sample-size). The different normalization modes led to different conclusions, measured as training-associated changes in transcript expression. Briefly, for 27% and 20% of the transcripts, training was associated with changes in expression in per-total-RNA and per-sample-size scenarios, but not in the per-library-size scenario. At week 2, this led to opposite conclusions for 4% of the transcripts between per-library-size and per-sample-size datasets (↑ vs. ↓, respectively). Conclusion Scientists should be explicit with their choice of normalization strategies and should interpret the results of gene expression analyses with caution. This is particularly important for data sets involving a limited number of genes or involving growing or differentiating cellular models, where the risk of biased conclusions is pronounced.

• Rønnestad, Bent; Urianstad, Thomas; Hamarsland, Håvard; Hansen, Joar; Nygård, Håvard & Ellefsen, Stian [Vis alle 8 forfattere av denne artikkelen] (2022). Heat Training Efficiently Increases and Maintains Hemoglobin Mass and Temperate Endurance Performance in Elite Cyclists. Medicine & Science in Sports & Exercise. ISSN 0195-9131. 54(9), s. 1515–1526. doi: 10.1249/MSS.0000000000002928.
• Rønnestad, Bent; Lid, Ole Martin; Hansen, Joar; Hamarsland, Håvard; Mølmen, Knut Sindre & Nygård, Håvard [Vis alle 9 forfattere av denne artikkelen] (2022). Heat suit training increases hemoglobin mass in elite cross-country skiers. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. doi: 10.1111/sms.14156.
• Oberholzer, Laura; Mølmen, Knut Sindre; Hammarström, Daniel; Falch, Gunnar Slettaløkken; Lundby, Anne-Kristine & Rønnestad, Bent [Vis alle 8 forfattere av denne artikkelen] (2022). Resistance exercise training increases skeletal muscle mitochondrial respiration in chronic obstructive pulmonary disease. JCSM Rapid Communications. 5. doi: 10.1002/rco2.58. Fulltekst i vitenarkiv Vis sammendrag

  Chronic obstructive pulmonary disease (COPD) is associated with skeletal muscle mitochondrial dysfunc-tion. Resistance exercise training (RT) is a training modality with a relatively small pulmonary demand that has beensuggested to increase skeletal muscle oxidative enzyme activity in COPD. Whether a shift into a more oxidative profilefollowing RT also translates into increased mitochondrial respiratory capacity in COPD is yet to be established.

• Hammarström, Daniel; Øfsteng, Sjur Johansen; Jacobsen, Nicolai Blindheim; Flobergseter, Krister; Rønnestad, Bent & Ellefsen, Stian (2022). Ribosome accumulation during early phase resistance training in humans. Acta Physiologica. ISSN 1748-1708. 235(1). doi: 10.1111/apha.13806. Vis sammendrag

  Aim: To describe ribosome biogenesis during resistance training, its relation to training volume and muscle growth. Methods: A training group (n = 11) performed 12 sessions (3-4 sessions per week) of unilateral knee extension with constant and variable volume (6 and 3-9 sets per session respectively) allocated to either leg. Ribosome abundance and biogenesis markers were assessed from vastus lateralis biopsies obtained at baseline, 48 hours after sessions 1, 4, 5, 8, 9 and 12, and after eight days of de-training, and from a control group (n = 8). Muscle thickness was measured before and after the intervention. Results: Training led to muscle growth (3.9% over baseline values, 95% CrI: [0.2, 7.5] vs. control) with concomitant increases in total RNA, ribosomal RNA, upstream binding factor (UBF) and ribosomal protein S6 with no differences between volume conditions. Total RNA increased rapidly in response to the first four sessions (8.6% [5.6, 11.7] per session), followed by a plateau and peak values after session 8 (49.5% [34.5, 66.5] above baseline). Total RNA abundance was associated with UBF protein levels (5.0% [0.2, 10.2] per unit UBF), and the rate of increase in total RNA levels predicted hypertrophy (0.3 mm [0.1, 0.4] per %-point increase in total RNA per session). After de-training, total RNA decreased (-19.3% [-29.0, -8.1]) without muscle mass changes indicating halted biosynthesis of ribosomes. Conclusion: Ribosomes accumulate in the initial phase of resistance training with abundances sensitive to training cessation and associated with UBF protein levels. The average accumulation rate predicts muscle training-induced hypertrophy. Keywords: muscle hypertrophy; resistance training; ribosome biogenesis. © 2022 The Authors. Acta Physiologica published by John Wiley & Sons Ltd on behalf of Scandinavian Physiological Society.

• Rønnestad, Bent; Bakken, Timo André; Thyli, Vetle; Hansen, Joar; Ellefsen, Stian & Hammarström, Jens Konrad Daniel (2021). Increasing Oxygen Uptake in Cross-Country 8 Skiers by Speed Variation in Work Intervals. International Journal of Sports Physiology and Performance (IJSPP). ISSN 1555-0265. 17(3), s. 384–390. doi: 10.1123/ijspp.2021-0226. Vis sammendrag

  Purpose: Accumulated time at a high percentage of peak oxygen consumption (VO2peak) is important for improving performance in endurance athletes. The present study compared the acute physiological and perceived effects of performing high-intensity intervals with roller ski double poling containing work intervals with (1) fast start followed by decreasing speed (DEC), (2) systematic variation in exercise intensity (VAR), and (3) constant speed (CON). Methods: Ten well-trained cross-country skiers (double-poling VO2peak 69.6 [3.5] mL·min−1·kg−1) performed speed- and duration-matched DEC, VAR, and CON on 3 separate days in a randomized order (5 × 5-min work intervals and 3-min recovery). Results: DEC and VAR led to longer time ≥90% VO2peak (P = .016 and P = .033, respectively) and higher mean %VO2peak (P = .036, and P = .009) compared with CON, with no differences between DEC and VAR (P = .930 and P = .759, respectively). VAR, DEC, and CON led to similar time ≥90% of peak heart rate (HRpeak), mean HR, mean breathing frequency, mean ventilation, and mean blood lactate concentration ([La−]). Furthermore, no differences between sessions were observed for perceptual responses, such as mean rate of perceived exertion, session rate of perceived exertion or pain score (all Ps > .147). Conclusions: In well-trained XC skiers, DEC and VAR led to longer time ≥90% of VO2peak compared with CON, without excessive perceptual effort, indicating that these intervals can be a good alternative for accumulating more time at a high percentage of VO2peak and at the same time mimicking the pronounced variation in exercise intensities experienced during XC-skiing competitions.

• Rønnestad, Bent; Øfsteng, Sjur Johansen; Zambolin, Fabio; Raastad, Truls & Hammarström, Jens Konrad Daniel (2021). Superior physiological adaptations after a microcycle of short intervals versus long intervals in cyclists. International Journal of Sports Physiology and Performance (IJSPP). ISSN 1555-0265. 16(10), s. 1432–1438. doi: 10.1123/IJSPP.2020-0647.
• Mølmen, Knut Sindre; Hammarström, Jens Konrad Daniel; Falch, Gunnar Slettaløkken; Grundtvig, Morten; Koll, Lise & Hanestadhaugen, Marita [Vis alle 14 forfattere av denne artikkelen] (2021). Chronic obstructive pulmonary disease does not impair responses to resistance training. Journal of Translational Medicine. ISSN 1479-5876. 19. doi: 10.1186/s12967-021-02969-1. Fulltekst i vitenarkiv Vis sammendrag

  Background: Subjects with chronic obstructive pulmonary disease (COPD) are prone to accelerated decay of muscle strength and mass with advancing age. This is believed to be driven by disease-inherent systemic pathophysiologies, which are also assumed to drive muscle cells into a state of anabolic resistance, leading to impaired abilities to adapt to resistance exercise training. Currently, this phenomenon remains largely unstudied. In this study, we aimed to investigate the assumed negative effects of COPD for health- and muscle-related responsiveness to resistance training using a healthy control-based translational approach. Methods: Subjects with COPD (n = 20, GOLD II-III, FEV1predicted 57 ± 11%, age 69 ± 5) and healthy controls (Healthy, n = 58, FEV1predicted 112 ± 16%, age 67 ± 4) conducted identical whole-body resistance training interventions for 13 weeks, consisting of two weekly supervised training sessions. Leg exercises were performed unilaterally, with one leg conducting high-load training (10RM) and the contralateral leg conducting low-load training (30RM). Measurements included muscle strength (nvariables = 7), endurance performance (nvariables = 6), muscle mass (nvariables = 3), muscle quality, muscle biology (m. vastus lateralis; muscle fiber characteristics, RNA content including transcriptome) and health variables (body composition, blood). For core outcome domains, weighted combined factors were calculated from the range of singular assessments. Results: COPD displayed well-known pathophysiologies at baseline, including elevated levels of systemic low-grade inflammation ([c-reactive protein]serum), reduced muscle mass and functionality, and muscle biological aberrancies. Despite this, resistance training led to improved lower-limb muscle strength (15 ± 8%), muscle mass (7 ± 5%), muscle quality (8 ± 8%) and lower-limb/whole-body endurance performance (26 ± 12%/8 ± 9%) in COPD, resembling or exceeding responses in Healthy, measured in both relative and numeric change terms. Within the COPD cluster, lower FEV1predicted was associated with larger numeric and relative increases in muscle mass and superior relative improvements in maximal muscle strength. This was accompanied by similar changes in hallmarks of muscle biology such as rRNA-content↑, muscle fiber cross-sectional area↑, type IIX proportions↓, and changes in mRNA transcriptomics. Neither of the core outcome domains were differentially affected by resistance training load. Conclusions: COPD showed hitherto largely unrecognized responsiveness to resistance training, rejecting the notion of disease-related impairments and rather advocating such training as a potent measure to relieve pathophysiologies. Trial registration: ClinicalTrials.gov ID: NCT02598830. Registered November 6th 2015, https://clinicaltrials.gov/ct2/show/NCT02598830. Keywords: Anabolic resistance; COPD; Pathophysiology; Skeletal muscle; Strength training; Training load.

• Mølmen, Knut Sindre; Hammarström, Jens Konrad Daniel; Pedersen, Karianne; Lie, Anne Cecilie Lian; Steile, Ragnvald B. & Nygård, Håvard [Vis alle 18 forfattere av denne artikkelen] (2021). Vitamin D3 supplementation does not enhance the effects of resistance training in older adults . Journal of Cachexia, Sarcopenia and Muscle. ISSN 2190-5991. 12(3), s. 599–628. doi: 10.1002/jcsm.12688. Fulltekst i vitenarkiv Vis sammendrag

  Background: Lifestyle therapy with resistance training is a potent measure to counteract age-related loss in muscle strength and mass. Unfortunately, many individuals fail to respond in the expected manner. This phenomenon is particularly common among older adults and those with chronic diseases (e.g. chronic obstructive pulmonary disease, COPD) and may involve endocrine variables such as vitamin D. At present, the effects of vitamin D supplementation on responses to resistance training remain largely unexplored. Methods: Ninety-five male and female participants (healthy, n = 71; COPD, n = 24; age 68 ± 5 years) were randomly assigned to receive either vitamin D3 or placebo supplementation for 28 weeks in a double-blinded manner (latitude 61°N, September-May). Seventy-eight participants completed the RCT, which was initiated by 12 weeks of supplementation-only (two weeks with 10 000 IU/day, followed by 2000 IU/day), followed by 13 weeks of combined supplementation (2000 IU/day) and supervised whole-body resistance training (twice weekly), interspersed with testing and measurements. Outcome measures included multiple assessments of muscle strength (nvariables = 7), endurance performance (n = 6), and muscle mass (n = 3, legs, primary), as well as muscle quality (legs), muscle biology (m. vastus lateralis; muscle fibre characteristics, transcriptome), and health-related variables (e.g. visceral fat mass and blood lipid profile). For main outcome domains such as muscle strength and muscle mass, weighted combined factors were calculated from the range of singular assessments. Results: Overall, 13 weeks of resistance training increased muscle strength (13% ± 8%), muscle mass (9% ± 8%), and endurance performance (one-legged, 23% ± 15%; whole-body, 8% ± 7%), assessed as weighted combined factors, and were associated with changes in health variables (e.g. visceral fat, -6% ± 21%; [LDL]serum , -4% ± 14%) and muscle tissue characteristics such as fibre type proportions (e.g. IIX, -3% points), myonuclei per fibre (30% ± 65%), total RNA/rRNA abundances (15%/6-19%), and transcriptome profiles (e.g. 312 differentially expressed genes). Vitamin D3 supplementation did not affect training-associated changes for any of the main outcome domains, despite robust increases in [25(OH)D]serum (∆49% vs. placebo). No conditional effects were observed for COPD vs. healthy or pre-RCT [25(OH)D]serum . In secondary analyses, vitamin D3 affected expression of gene sets involved in vascular functions in muscle tissue and strength gains in participants with high fat mass, which advocates further study. Conclusions: Vitamin D3 supplementation did not affect muscular responses to resistance training in older adults with or without COPD. Keywords: Cholecalciferol; Muscle plasticity; Strength training. © 2021 The Authors. Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of Society on Sarcopenia, Cachexia and Wasting Disorders.

• Noordhof, Dionne; Øfsteng, Sjur Johansen; Nirenberg, Linnea; Hammarström, Jens Konrad Daniel; Hansen, Joar & Rønnestad, Bent [Vis alle 7 forfattere av denne artikkelen] (2021). Performance-determining variables in long-distance events: should they be determined from a rested state or after prolonged submaximal exercise? International Journal of Sports Physiology and Performance (IJSPP). ISSN 1555-0265. 16(5), s. 647–654. doi: 10.1123/ijspp.2019-0987. Fulltekst i vitenarkiv Vis sammendrag

  Performance-determining variables are usually measured from a rested state and not after prolonged exercise, specific to when athletes compete for the win in long-distance events. Purpose: (1) To compare cross-country skiing double-poling (DP) performance and the associated physiological and biomechanical performance-determining variables between a rested state and after prolonged exercise and (2) to investigate whether the relationship between the main performance-determining variables and DP performance is different after prolonged submaximal DP than when tested from a rested state. Methods: Male cross-country skiers (N = 26) performed a blood lactate profile test and an incremental test to exhaustion from a rested state on day 1 (D1; all using DP) and after 90-minute submaximal DP on day 2 (D2). Results: The DP performance decreased following prolonged submaximal DP (D1: peak speed = 15.33–20.75 km·h−1, median = 18.1 km·h−1; D2: peak speed = 13.68–19.77 km·h−1, median = 17.8 km·h−1; z = −3.96, P < .001, effect size r = −.77), which coincided with a reduced submaximal gross efficiency and submaximal and peak cycle length, with no significant change in peak oxygen uptake (P = .26, r = .23). The correlation coefficient between D1 cycle length at 12 km·h−1 and D2 performance is significantly smaller than the correlation coefficient between D2 cycle length at 12 km·h−1 and D2 performance (P = .033), with the same result being found for peak cycle length (P < .001). Conclusions: The reduced DP performance after prolonged submaximal DP coincided with a reduced submaximal gross efficiency and shorter peak cycle length. The results indicate that performance-determining variables could be determined after prolonged exercise to gain more valid insight into long-distance DP performance.

• Khan, Yusuf; Hammarström, Jens Konrad Daniel; Rønnestad, Bent; Ellefsen, Stian & Ahmad, Rafi (2020). Increased biological relevance of transcriptome analyses in human skeletal muscle using a model-specific pipeline. BMC Bioinformatics. ISSN 1471-2105. 21(1). doi: 10.1186/s12859-020-03866-y. Fulltekst i vitenarkiv Vis sammendrag

  Background: Human skeletal muscle responds to weight-bearing exercise with significant inter-individual differences. Investigation of transcriptome responses could improve our understanding of this variation. However, this requires bioinformatic pipelines to be established and evaluated in study-specific contexts. Skeletal muscle subjected to mechanical stress, such as through resistance training (RT), accumulates RNA due to increased ribosomal biogenesis. When a fixed amount of total-RNA is used for RNA-seq library preparations, mRNA counts are thus assessed in different amounts of tissue, potentially invalidating subsequent conclusions. The purpose of this study was to establish a bioinformatic pipeline specific for analysis of RNA-seq data from skeletal muscles, to explore the effects of different normalization strategies and to identify genes responding to RT in a volume-dependent manner (moderate vs. low volume). To this end, we analyzed RNA-seq data derived from a twelve-week RT intervention, wherein 25 participants performed both low- and moderate-volume leg RT, allocated to the two legs in a randomized manner. Bilateral muscle biopsies were sampled from m. vastus lateralis before and after the intervention, as well as before and after the fifth training session (Week 2). Result: Bioinformatic tools were selected based on read quality, observed gene counts, methodological variation between paired observations, and correlations between mRNA abundance and protein expression of myosin heavy chain family proteins. Different normalization strategies were compared to account for global changes in RNA to tissue ratio. After accounting for the amounts of muscle tissue used in library preparation, global mRNA expression increased by 43-53%. At Week 2, this was accompanied by dose-dependent increases for 21 genes in rested-state muscle, most of which were related to the extracellular matrix. In contrast, at Week 12, no readily explainable dose-dependencies were observed. Instead, traditional normalization and non-normalized models resulted in counterintuitive reverse dose-dependency for many genes. Overall, training led to robust transcriptome changes, with the number of differentially expressed genes ranging from 603 to 5110, varying with time point and normalization strategy. Conclusion: Optimized selection of bioinformatic tools increases the biological relevance of transcriptome analyses from resistance-trained skeletal muscle. Moreover, normalization procedures need to account for global changes in rRNA and mRNA abundance. Keywords: Bioinformatics pipeline; Normalization; RNA-seq; Skeletal muscle.

• Almquist, Nicki Winfield; Nygård, Håvard; Vegge, Geir; Hammarström, Jens Konrad Daniel; Ellefsen, Stian & Rønnestad, Bent (2020). Systemic and muscular responses to effort-matched short intervals and long intervals in elite cyclists. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 30, s. 1140–1150. doi: 10.1111/sms.13672. Fulltekst i vitenarkiv Vis sammendrag

  The purpose of this study was to compare the acute effects of time- and effort-matched high-intensity intervals on physiological, endocrine, and skeletal muscle molecular variables in elite cyclists. Eight elite cyclists performed short intervals (SI: 30-seconds) and long intervals (LI: 5-minutes) with work:recovery ratio 2:1, using a randomized crossover design. SI was associated with 14% ± 3% higher mean power output (SI; 421 ± 27 vs LI; 371 ± 22 W), and longer working time above 90% of maximal oxygen uptake (VO2max, 54% ± 76%) and 90% peak heart rate (HRpeak, 153% ± 148%) than LI (all P < .05), despite similar degrees of perceived exertion, blood lactate levels and muscle activation measured using EMG root mean square (EMG rms). In blood, SI was associated with more pronounced increases in testosterone and testosterone-tosex hormone-binding globulin (SHBG) ratios, as well as prolonged cortisol responses (P < .05). In skeletal muscle (m. Vastus lateralis), SI and LI led to similar changes in mRNA abundance for a range of transcripts, with the exception of NHE1 mRNA, which decreased after SI (P < .05). Overall, SI was associated with more pronounced physiological and endocrine responses than LI in elite cyclists, suggesting that such training might lead to superior adaptations in elite cyclists.

• Hammarström, Daniel; Øfsteng, Sjur Johansen; Koll, Lise; Hanestadhaugen, Marita; Hollan, Ivana & Apro, William [Vis alle 10 forfattere av denne artikkelen] (2019). Benefits of higher resistance‐training volume are related to ribosome biogenesis. Journal of Physiology. ISSN 0022-3751. 598(3), s. 543–565. doi: 10.1113/JP278455. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Resistance-exercise volume is a determinant of training outcomes. However not all individuals respond in a dose-dependent fashion. In this study, 34 healthy individuals (males n = 16, 23.6 (4.1) years; females n = 18, 22.0 (1.3) years) performed moderate- (3 sets per exercise, MOD) and low-volume (1 set, LOW) resistance training in a contralateral fashion for 12 weeks (2–3 sessions per week). Muscle cross-sectional area (CSA) and strength were assessed at Weeks 0 and 12, along with biopsy sampling (m. vastus lateralis). Muscle biopsies were alsosampled before and 1 h after the fifth session (Week 2). MOD resulted in larger increases in muscleCSA (5.2 (3.8)% versus 3.7 (3.7)%, P < 0.001) and strength (3.4–7.7% difference, all P < 0.05.This coincided with greater reductions in type IIX fibres from Week 0 to Week 12 (MOD,−4.6 percentage p oints; LOW −3.2 percentage points), greater phosphorylation of S6-kinase 1(p85 S6K1Thr412, 19%; p70 S6K1Thr389, 58%) and ribosomal protein S6Ser235/236(37%), greaterrested-state total RNA (8.8%) and greater exercise-induced c-Myc mRNA expression (25%;Week 2, all P < 0.05). Thirteen and sixteen participants, respectively, displayed clear benefits inresponse to MOD on muscle hypertrophy and strength. Benefits were associated with greateraccumulation of total RNA at Week 2 in the MOD leg, with every 1% difference increasing theodds of MOD benefit by 7.0% (P = 0.005) and 9.8% (P = 0.002). In conclusion, MOD led togreater functional and biological adaptations than LOW. Associations between dose-dependenttotal RNA accumulation and increases in muscle mass and strength point to ribosome biogenesisas a determinant of dose-dependent training responses.

• Robach, Paul; Hansen, Joar; Pichon, Aurelien; Meinild Lundby, Anne-Kristine; Dandanell, Sune & Slettaløkken, Gunnar [Vis alle 14 forfattere av denne artikkelen] (2018). Hypobaric live high-train low does not improve aerobic performance more than live low-train low in cross-country skiers. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 28(6), s. 1636–1652. doi: 10.1111/sms.13075.
• Skovereng, Knut; Sylta, Øystein; Tønnessen, Espen; Hammarström, Daniel; Danielsen, Jørgen & Seiler, Stephen [Vis alle 8 forfattere av denne artikkelen] (2018). Effects of initial performance, gross efficiency and VO_2peak characteristics on subsequent adaptations to endurance training in competitive cyclists. Frontiers in Physiology. ISSN 1664-042X. 9, s. 1–9. doi: 10.3389/fphys.2018.00713. Fulltekst i vitenarkiv
• Øfsteng, Sjur Johansen; Sandbakk, Øyvind; Van Beekvelt, Mireille; Hammarström, Daniel; Kristoffersen, Roger & Hansen, Joar [Vis alle 8 forfattere av denne artikkelen] (2017). Strength training improves double-poling performance after prolonged submaximal exercise in cross-country skiers. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 28(3), s. 893–904. doi: 10.1111/sms.12990. Fulltekst i vitenarkiv Vis sammendrag

  The purpose of this study was to investigate the effects of adding strength training with or without vibration to cross-country (XC) skiers' endurance training on double-poling (DP) performance, physiological, and kinematic adaptations. Twenty-one well-trained male XC-skiers combined endurance- and upper-body strength training three times per week, either with (n = 11) or without (n = 10) superimposed vibrations for 8 weeks, whereas eight skiers performed endurance training only (CON). Testing included 1RM in upper-body exercises, work economy, neural activation, oxygen saturation in muscle, and DP kinematics during a prolonged submaximal DP roller ski test which was directly followed by a time to exhaustion (TTE) test. TTE was also performed in rested state, and the difference between the two TTE tests (TTEdiff ) determined the ability to maintain DP performance after prolonged exercise. Vibration induced no additional effect on strength or endurance gains. Therefore, the two strength training groups were pooled (STR, n = 21). 1RM in STR increased more than in CON (P < .05), and there were no differences in changes between STR and CON in any measurements during prolonged submaximal DP. STR improved TTE following prolonged DP (20 ± 16%, P < .001) and revealed a moderate effect size compared to CON (ES = 0.80; P = .07). Furthermore, STR improved TTEdiff more than CON (P = .049). In conclusion, STR superiorly improved 1RM strength, DP performance following prolonged submaximal DP and TTEdiff , indicating a specific effect of improved strength on the ability to maintain performance after long-lasting exercise.

• Sylta, Øystein; Tønnessen, Espen (red.); Sandbakk, Øyvind; Hammarström, Daniel; Danielsen, Jørgen & Skovereng, Knut [Vis alle 8 forfattere av denne artikkelen] (2017). Effects of high-intensity training on physiological and hormonal adaptions in well-trained cyclists. Medicine & Science in Sports & Exercise. ISSN 0195-9131. 49(6), s. 1137–1146. doi: 10.1249/MSS.0000000000001214. Fulltekst i vitenarkiv
• Nygård, Håvard; Rønnestad, Bent; Hammarström, Daniel; Holmboe-Ottesen, Gerd & Høstmark, Arne Torbjørn (2017). Effects of exercise in the fasted and postprandial state on interstitial glucose in hyperglycemic individuals. Journal of Sports Science and Medicine. ISSN 1303-2968. 16(2), s. 254–263. Vis sammendrag

  The purpose of the present study was to test if one bout of moderate exercise performed in either the fasted or the postprandial state affects glucose values measured over 22 hours. Twelve participants diagnosed with hyperglycemia not using antidiabetic medications underwent 3 test days in a randomized cross-over design encompassing one test day without exercise, one test day with 60 min of treadmill walking prior to breakfast, and one test day with an identical bout of exercise 30 min after the start of breakfast. Continuous glucose monitoring was performed until the next morning (>22 hours). There was no significant effect of type of test day on the area under the glucose curve for the entire 22 hours period (p = 0.111). None of the exercise interventions had a significant effect on the area under the glucose curve after breakfast, lunch or dinner. However, the postprandial exercise bout tended to decrease the area under the glucose curve after the evening meal compared to the fasted exercise bout (24.2 ± 6.2 vs. 27.6 ± 6.0 mmol·hour·L-1, p = 0.031). Furthermore, the postprandial exercise decreased the mean of the 10 highest glucose values measured in each individual (8.6 ± 1.9 mmol·L-1) over 22 hours compared to both the control day (9.3 ± 2.1 mmol.L-1) and the day with fasted exercise (9.6 ± 1.7 mmol·L-1, p = 0.012 and 0.009 respectively). Postprandial exercise also decreased the glycemic variability compared to the control day (1.22 ± 0.49 vs. 1.58 ± 0.52 mmol·L-1, p = 0.015). We conclude that performing moderate exercise in the postprandial state after breakfast, but not in the fasted state, decreases glucose excursions during the subsequent 22 hours period in hyperglycemic individuals not using antidiabetic medications.

• Sylta, Øystein; Tønnessen, Espen; Hammarström, Daniel; Danielsen, Jørgen; Skovereng, Knut & Ravn, Troels [Vis alle 9 forfattere av denne artikkelen] (2016). The Effect of Different High-Intensity Periodization Models on Endurance Adaptations. Medicine & Science in Sports & Exercise. ISSN 0195-9131. 48(11), s. 2165–2174. doi: 10.1249/MSS.0000000000001007. Fulltekst i vitenarkiv
• Carlsson, Tomas; Carlsson, Magnus; Hammarström, Daniel; Rønnestad, Bent; Malm, Christer & Tonkonogi, Michail (2015). Optimal V̇O2max-to-mass ratio for predicting 15 km performance among elite male cross-country skiers . Open Access Journal of Sports Medicine. ISSN 1179-1543. s. 353–360. doi: 10.2147/OAJSM.S93174. Vis sammendrag

  The aim of this study was 1) to validate the 0.5 body-mass exponent for maximal oxygen uptake (V̇O2max) as the optimal predictor of performance in a 15 km classical-technique skiing competition among elite male cross-country skiers and 2) to evaluate the influence of distance covered on the body-mass exponent for V̇O2max among elite male skiers. Twenty-four elite male skiers (age: 21.4±3.3 years [mean ± standard deviation]) completed an incremental treadmill roller-skiing test to determine their V̇O2max. Performance data were collected from a 15 km classical-technique cross-country skiing competition performed on a 5 km course. Power-function modeling (ie, an allometric scaling approach) was used to establish the optimal body-mass exponent for V̇O2max to predict the skiing performance. The optimal power-function models were found to be race speed = 8.83 • (V̇O2max m-0.53)0.66 and lap speed = 5.89 • (V̇O2max m-(0.49+0.018lap))0.43e0.010age, which explained 69% and 81% of the variance in skiing speed, respectively. All the variables contributed to the models. Based on the validation results, it may be recommended that V̇O2max divided by the square root of body mass (mL • min-1 • kg-0.5) should be used when elite male skiers’ performance capability in 15 km classical-technique races is evaluated. Moreover, the body-mass exponent for V̇O2max was demonstrated to be influenced by the distance covered, indicating that heavier skiers have a more pronounced positive pacing profile (ie, race speed gradually decreasing throughout the race) compared to that of lighter skiers.

• 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.

• Carlsson, Magnus; Carlsson, Tomas; Hammarström, Daniel; Malm, Christer & Tonkonogi, Michail (2014). Prediction of race performance of elite cross-country skiers by lean mass. International Journal of Sports Physiology and Performance (IJSPP). ISSN 1555-0265. 9(6), s. 1040–1045. doi: 10.1123/ijspp.2013-0509.
• Ellefsen, Stian; Vikmoen, Olav; Zacharoff, Erika; Rauk, Irene; Slettaløkken, Gunnar & Hammarström, Daniel [Vis alle 14 forfattere av denne artikkelen] (2014). Reliable determination of training-induced alterations in muscle fiber composition in human skeletal muscle using quantitative polymerase chain reaction. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 24(4), s. e332–e342. doi: 10.1111/sms.12185. Vis sammendrag

  Determination of muscle fiber composition in human skeletal muscle biopsies is often performed using immunohistochemistry, a method that tends to be both time consuming, technically challenging, and complicated by limited availability of tissue. Here, we introduce quantitative reverse transcriptase polymerase chain reaction (qRT-PCR)-based Gene-family profiling (GeneFam) of myosin heavy chain (MyHC) mRNA expression as a high-throughput, sensitive, and reliable alternative. We show that GeneFam and immunohistochemistry result in similar disclosures of alterations in muscle fiber composition in biopsies from musculus vastus lateralis and musculus biceps brachii of previously untrained young women after 12 weeks of progressive strength training. The adaptations were evident as (a) consistent increases in MyHC2A abundance; (b) consistent decreases in MyHC2X abundance; and (c) consistently stable MyHC1 abundance, and were not found using traditional reference gene-based qRT-PCR analyses. Furthermore, muscle fiber composition found using each of the two approaches was correlated with each other (r = 0.50, 0.74, and 0.78 for MyHC1, A, and X, respectively), suggesting that GeneFam may be suitable for ranking of individual muscle phenotype, particularly for MyHC2 fibers. In summary, GeneFam of MyHC mRNA resulted in reliable assessment of alterations in muscle fiber composition in skeletal muscle of previously untrained women after 12 weeks of strength training.

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• Odden, Ingvill; Østli Nymoen, Lars; Urianstad, Tomas; Hammarström, Daniel; Mølmen, Knut Sindre & Rønnestad, Bent (2023). The higher fraction of V̇O2max during interval training, the greater gains in performance.
• Ellefsen, Stian; Hammarström, Daniel; Mølmen, Knut Sindre & Hamarsland, Håvard (2022). The Trainome – combining exercise training and nutrition to improve the health efficacy of lifestyle therapy.
• Hamarsland, Håvard; Hammarström, Jens Konrad Daniel; Hafsmo, Mads-Henrik; Varpestuen, Tomas & Ellefsen, Stian (2022). Evidence for volume-dependent cross-learning during 10 weeks of unilateral heavy resistance training. Vis sammendrag

  INTRODUCTION: Unilateral training protocols allow one individual to undergo two different treatments within the same timeframe, allocated to each of the two limbs. The benefit of such designs includes increased statistical power, due to within-individual comparisons, with accompanying reductions in required resources. Despite this, training interventions seldom employ unilateral designs, which is likely due to potential cross-learning effects between the two limbs, whereby training of one limb induces gains in strength in the contralateral limb, as reported in a number of studies. Although the presence of such cross-learning effects is widely accepted, it has proven difficult to conclude on this perspective, due to several methodological issues with previous studies. The goal of the current study was to investigate the potential cross-learning effects during a 10-week unilateral training intervention with two different training volumes or lack thereof. METHODS: Healthy untrained subjects (♂:12, ♀:27, 24.4±3.9 yrs) participated in a 10-week whole-body training intervention, wherein the legs were exposed to either of three interventions, i) no training, ii) three sets of 10RM resistance training (RT), or iii) six sets of 10RM RT, performed three times per week in a contralateral manner (leg press and knee extension). For these interventions, participants performed either of five combinations: 0-3, 0-6, 3-6, 0-0 and 3-3. Muscle strength was assessed as 1RM (leg press and knee extension) and isokinetic strength (0°/sec, 60°/sec and 240°/sec), performed 4 times during the initial 3 weeks of training and 2 times in week 11. Average weighted mean changes after familiarization were used in analyses. Muscle mass was assessed as mid-thigh muscle thickness (m. vastus lateralis and m. vastus intermedius, ultrasound) in weeks 1, 3, 7 and 11. Group * Time effects were evaluated using mixed-effects models. RESULTS: Strength development in non-trained legs showed an interaction effect with the training volume performed by the other leg (group * time P=0.011), increasing 6.9 % in 0-6 (95% CI: 1.7, 12.4) and 2.0 % in 0-3 [-2.8, 7.0] compared to 0-0. This was not seen in the 3-set leg (group * time P=0.110). For muscle thickness, neither non-trained legs nor three-set legs displayed contralateral spillover from the trained leg (non-trained legs, group * time P=0.728; three-set leg, group * time P=0.728). CONCLUSION: In contralateral training designs, cross-learning may affect strength outcome in non-training control limbs, but not muscle mass. The extent of the contralateral training effect seems to be influenced by the prescribed training volume in the trained limb.

• Ellefsen, Stian & Hammarström, Jens Konrad Daniel (2021). Forskere har undersøkt myten om at tung trening gir størst fremgang. Forskersonen.no.
• Khan, Yusuf; Hammarström, Jens Konrad Daniel; Ellefsen, Stian & Ahmad, Rafi (2019). RNA-seq pipeline and transcriptome response to resistance training.
• Khan, Yusuf; Hammarström, Jens Konrad Daniel; Ellefsen, Stian & Ahmad, Rafi (2019). RNA-seq pipeline and transcriptome response to resistance training.
• Mølmen, Knut Sindre; Lian Lie, Anne Cecilie; Hammarström, Daniel; Lie Eriksen, Atle; Malerbakken, Bente & Ellefsen, Stian (2019). Tilpasninger til høy- og lavmotstandsstyrketrening for KOLS-rammede og friske, eldre personer.
• Mølmen, Knut Sindre; Lian Lie, Anne Cecilie; Hammarström, Daniel; Rønnestad, Bent; Lie Eriksen, Atle & Malerbakken, Bente [Vis alle 8 forfattere av denne artikkelen] (2019). ADAPTATIONS TO HIGH-LOAD AND LOW-LOAD RESISTANCE TRAINING IN COPD PATIENTS AND HEALTHY OLDER SUBJECTS.
• Hammarström, Daniel; Øfsteng, Sjur Johansen; Jacobsen, Nicolai; Flobergseter, Krister; Rønnestad, Bent & Ellefsen, Stian (2019). Characteristics of ribosomal accumulation during short-term resistance training with variable training volume and the effect of short-term de-training.
• Nygård, Håvard; Hammarström, Jens Konrad Daniel & Ellefsen, Stian (2019). Does vitamin d supplementation entail a 2x 2a fibertype shift? .
• Noordhof, Dionne; Øfsteng, Sjur Johansen; Nirenberg, Linnea; Hammarström, Daniel; Hansen, Joar & Rønnestad, Bent [Vis alle 7 forfattere av denne artikkelen] (2019). Double-poling performance-determining variables should be evaluated after prolonged exercise.
• Rønnestad, Bent; Øfsteng, Sjur Johansen; Knox, Silje; Hammarström, Daniel; Helkala, Kirsi Marjaana & Knox, Benjamin James [Vis alle 9 forfattere av denne artikkelen] (2016). 10 RM vs 30 RM : Training load does matter.
• Ellefsen, Stian; Hammarström, Daniel & Rønnestad, Bent (2016). Strength training alters expression of genes involved in regulation of steroid hormone availability in M. Vastus Lateralis of untrained women.
• Hammarström, Daniel; Rønnestad, Bent; Blomstrand, E.; Whist, Jon Elling & Ellefsen, Stian (2016). Ribosome biogenesis and individual responses to strength-training of low and moderate volume.
• Hammarström, Daniel; Rønnestad, Bent; Blomstrand, Eva & Ellefsen, Stian (2015). Myosin heavychain 2X expression interacts with acute regulation of PGC-1alpha splice-4 following strength exercise with low and moderate volume.
• 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.
• 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.
• Hammarström, Daniel (2021). Determinants of intra-individual variation in adaptability to resistance training of different volumes. Gymnastik- och idrottshögskolan, GIH. ISSN 9789198649024.

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