Håvard Hamarsland

Repeating the same exercise training intervention within the same individuals after an adequate detraining period provides a direct test of whether physiological adaptations are reproducible within individuals. This study demonstrates that individual physiological adaptations to a repeated endurance training program are largely nonreproducible across multiple physiological and performance outcomes, despite highly standardized and closely supervised training conditions. The substantial within-individual response variability challenges the notion that physiological training responsiveness is a stable, trait-like characteristic.

Adding three weekly heat training sessions to a training camp at moderate natural altitude (<2,000 m.a.s.l.) resulted in greater increase in hemoglobin mass compared with traditional training at moderate altitude or sea level in well-trained endurance athletes. However, these hematological improvements were not accompanied by significant between-group differences in submaximal or maximal roller-ski performance indicators. Heat training may represent a practical strategy for coaches and athletes to enhance erythropoietic adaptations when higher-altitude environments are unavailable.

The purpose of this study was to compare the effects of a 1‐week block of moderate‐intensity interval training (MIT) and high‐intensity interval training (HIT) in well‐trained cyclists. Cyclists (♀ = 1; ♂ = 21; maximal oxygen uptake (V̇O _2max ) = 69.5 (6.0) mL·min ⁻¹ ·kg ⁻¹ ) performed both a MIT block involving 6 sessions over 7 days (5–7 × 10–14‐min work intervals, rate of perceived exertion (RPE): 14.5 (0.3)) and a HIT block involving 5 sessions over 6 days (5 × 8.75‐min with multiple short intervals, RPE: 17.1 (0.4)). Post‐testing was performed after 6 days of active recovery, and blocks were separated by 2 months. Testing included 15‐min maximal cycling power (PO _15min ), 10 s maximal sprint power (PO _10sec ), and power output at a blood lactate concentration of 4 mmol·L ⁻¹ (PO _4mmol ). Both the MIT and HIT block improved PO _15min (4.9 (8.7)% and 2.8 (5.3)%, respectively), with no difference between blocks ( p = 0.44). MIT displayed greater improvement than HIT in PO _4mmol (4.5 (4.5)% vs. 2.1 (2.7)%, respectively, p = 0.03, moderate effect size (ES)), while HIT had a moderate ES compared to MIT for improvement in PO _10sec (1.5 (3.7)% vs. −1.5 (7.3)%, respectively), that was not significant ( p = 0.08). No differences were observed between blocks in changes in V̇O _2max ( p = 0.43) or measures of gross efficiency ( p range = 0.43–0.79). However, MIT induced a larger increase in % of V̇O _2max at PO _4mmol compared to HIT (1.2 (3.4)%‐points vs. −0.9 (2.5)%‐points, respectively, p = 0.02, moderate ES). In conclusion, both a MIT block (lower work interval intensity but longer work duration) and a HIT block (higher work interval intensity but shorter work duration) can improve endurance performance determinants and PO _15min with some work intensity‐specific adaptations.

Purpose: Resistance training-induced skeletal muscle hypertrophy seems to depend on ribosome biogenesis and content. High glucose treatment may augment ribosome biogenesis through potentiating resistance training-induced adaptations. This was investigated with total RNA and ribosomal RNA abundances as main outcomes, with relevant transcriptional/translational regulators (c-Myc/UBF/rpS6) as a secondary outcome. Methods: Sixteen healthy, moderately trained individuals [male/female, n = 9/7; age, 24.1 (3.3)] participated in a within-participant crossover trial with unilateral resistance training (leg press and knee extension, 3 sets of 10 repetitions maximum) and pre- and post-exercise ingestion of either glucose (3 × 30 g, 90 g total) or placebo supplements (Stevia rebaudiana, 3 × 0.3 g, 0.9 g total), together with protein (2 × 25 g, 50 g total), on alternating days for 12 days. Six morning resistance exercise sessions were conducted per condition, and the sessions were performed in an otherwise fasted state. Micro-biopsies were sampled from m. vastus lateralis before and after the intervention. Results: Glucose ingestion did not have beneficial effects on resistance training-induced increases of ribosomal content (mean difference 7.6% [− 7.2, 24.9], p = 0.34; ribosomal RNA, 47S/18S/28S/5.8S/5S, range 7.6–37.9%, p = 0.40–0.98) or levels of relevant transcriptional or translational regulators (c-MYK/UBF/rpS6, p = 0.094–0.292). Of note, both baseline and trained state data of total RNA showed a linear relationship with UBF; a ∼14% increase in total RNA corresponded to 1 SD unit increase in UBF (p = 0.003). Conclusion: Glucose ingestion before and after resistance training sessions did not augment ribosomal RNA accumulation during twelve days of heavy-load resistance training in moderately trained young adults.

We demonstrate in elite female and male cyclists that heat exercise training (5 × 50 min sessions/wk for 5 wk) facilities Hb_mass and other hematological parameters more than control exercise training, whereas skeletal muscle properties remain unaltered. Collectively, this coincided with improvements in lactate threshold, V̇o_2max, and 15-min all-out cycling performance.

Background: Changes in tryptophan metabolism through the kynurenine pathway (KP) are observed in several disorders and coupled with pathophysiological deviations. Methods: This study retrospectively compared the KP in serum in healthy subjects (108) with subjects with obesity (141), depression (49), and chronic obstructive pulmonary disease (COPD) (22) participating in four clinical studies and explored predictors of the changes in the KP metabolites. Results: Compared with the healthy group, the KP was upregulated in the disease groups with high kynurenine, quinolinic acid (QA), kynurenine/tryptophan-ratio and QA/xanthurenic acid-ratio and low kynurenic acid/QA-ratio. Tryptophan and xanthurenic acid were upregulated in the depressed group compared with the groups with obesity and COPD. The covariates BMI, smoking, diabetes, and C-reactive protein explained the significant differences between the healthy group and the group with obesity but not between the healthy group and the groups with depression and COPD, indicating that different pathophysiological conditions result in the same changes in the KP. Conclusions: The KP was significantly upregulated in the disease groups compared with the healthy group, and there were significant differences between the disease groups. Different pathophysiological abnormalities seemed to result in the same deviations in the KP.

The main goal of the current study was to compare the effects of volume-equated training frequency on gains in muscle mass and strength. In addition, we aimed to investigate whether the effect of training frequency was affected by the complexity, concerning the degrees of freedom, of an exercise. Participants were randomized to a moderate training frequency group (two weekly sessions) or high training frequency group (four weekly sessions). Twenty-one participants (male: 11, female: 10, age: 25.9 ± 4.0) completed the 9-week whole-body progressive heavy resistance training intervention with moderate (n = 13) or high (n = 8) training frequency. Whole-body and regional changes in lean mass were measured using dual-energy x-ray absorptiometry, while the vastus lateralis thickness was measured by ultrasound. Changes in muscle strength were measured as one repetition maximum for squat, hack squat, bench press, and chest press. No differences between groups were observed for any of the measures of muscle growth or muscle strength. Muscle strength increased to a greater extent in hack squat and chest press than squat and bench press for both moderate (50 and 21% vs. 19 and 14%, respectively) and high-frequency groups (63 and 31% vs. 19 and 16%, respectively), with no differences between groups. These results suggest that training frequency is less decisive when weekly training volume is equated. Further, familiarity with an exercise seems to be of greater importance for strength adaptations than the complexity of the exercise.

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 D ₃ 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 ( n _variables = 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 D ₃ 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 D ₃ 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 D ₃ supplementation did not affect muscular responses to resistance training in older adults with or without COPD.

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 chronically diseased (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 D ₃ 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 (in average, 3333 IU.day ^-1 ), followed by 13 weeks of combined supplementation (2000 IU.day ^-1 ) and supervised whole-body resistance training (twice weekly), interspersed with testing and measurements. Outcome measures included multiple assessments of muscle strength (n=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·fibre ^-1 (30% ± 65%), total RNA/rRNA abundances (15%/6-19%), and transcriptome profiles (e.g. ∼336 differentially expressed genes). Vitamin D ₃ supplementation led to robust increases in [25(OH)D] _serum (Δ49% vs placebo), but did not affect training-associated changes for any of the main outcome domains, with no interaction being evident with disease status or pre-RCT [25(OH)D] _serum . In secondary analyses, vitamin D ₃ affected expression of gene sets involved in vascular functions in muscle tissue, strength gains in participants with high fat mass, and [cortisol] _serum (Δ20%), all of which advocate further study. Conclusions: Vitamin D ₃ supplementation did not affect muscular responses to resistance training in old adults with or without COPD.

Background: Large amounts of protein (40 g) or supplementing suboptimal servings of protein with leucine are able to overcome the anabolic resistance in elderly muscle. Our aim was to compare the effects of supplementation of native whey, high in leucine, with milk on gains in muscle mass and strength during a period of strength training, in elderly individuals. Methods: In this double-blinded, randomized, controlled study, a total of 30 healthy men and women received two daily servings of 20 g of either milk protein or native whey, during an 11-week strength training intervention. Muscle strength, lean mass, m. vastus lateralis thickness, muscle fiber area, and resting and post-exercise phosphorylation of p70S6K, 4E-BP1, and eEF-2 were assessed prior to and after the intervention period. Results: Muscle mass and strength increased, by all measures applied in both groups (p < 0.001), with no differences between groups (p > 0.25). p70S6K phosphorylation increased (~1000%, p < 0.045) 2 h after exercise in the untrained and trained state, with no differences between supplements. Total and phosphorylated mTORC-1 decreased after training. Conclusion: Supplementation with milk or native whey during an 11-week strength training period increased muscle mass and strength similarly in healthy elderly individuals.