Explore the vast range of titles available.

The asymptote (critical power; CP) and curvature constant (W') of the hyperbolic power–duration relationship can predict performance within the severe‐intensity exercise domain. However, the extent to which these parameters relate to skeletal muscle mitochondrial content and respiratory function is not known. Fifteen males (peak O2 uptake, 52.2 ± 8.7 mL kg−1 min−1; peak work rate, 366 ± 40 W; and gas exchange threshold, 162 ± 41 W) performed three to five constant‐load tests to task failure for the determination of CP (246 ± 44 W) and W' (18.6 ± 4.1 kJ). Skeletal muscle biopsies were obtained from the vastus lateralis to determine citrate synthase (CS) activity, as a marker of mitochondrial content, and the ADP‐stimulated respiration (P) and maximal electron transfer (E) through mitochondrial complexes (C) I–IV. The CP was positively correlated with CS activity (absolute CP, r = 0.881, P < 0.001; relative CP, r = 0.751, P = 0.001). The W' was not correlated with CS activity (P > 0.05). Relative CP was positively correlated with mass‐corrected CI + IIE (r = 0.659, P = 0.038), with absolute CP being inversely correlated with CS activity‐corrected CIVE (r = −0.701, P = 0.024). Relative W' was positively correlated with CS activity‐corrected CI + IIP (r = 0.713, P = 0.021) and the phosphorylation control ratio (r = 0.661, P = 0.038). There were no further correlations between CP or W' and mitochondrial respiratory variables. These findings support the assertion that skeletal muscle mitochondrial oxidative capacity is positively associated with CP and that this relationship is strongly determined by mitochondrial content. What is the central question of this study? The asymptote (critical power; CP) and curvature constant (W') of the hyperbolic power–duration relationship are important determinants of severe‐intensity exercise performance. We assessed the relationship between these parameters and skeletal muscle mitochondrial content and respiration. What us the main finding and its importance? Citrate synthase (CS) activity was positively correlated with CP. Relative CP was positively correlated with mass‐corrected CI + IIE; absolute CP was inversely correlated with CS activity‐corrected CIVE. CS activity was not correlated with W'. CS activity‐corrected CI + IIP and the phosphorylation control ratio were positively correlated with relative W'. Mitochondrial content influences CP. Some facets of mitochondrial respiration might influence W'.

The aim of this study was to evaluate athletic performance and training in transgender women (TW) athletes competing in running and swimming both pre and post gender affirming hormone therapy (GAHT). Using survey methods, 9 TW runners and 1 TW swimmer provided independently verified retrospective data for race times, training volume, height, body mass, and testosterone, oestrogen and haemoglobin concentrations and pre‐GAHT and post‐GAHT. Prospective data were collected for a further 12 months. Changes in performance and age‐grade scores (AGs) for runners and FINA scores for the swimmer were calculated. For runners, pre‐GAHT and post‐GAHT differences in AGs were adjusted based on training differences over time. Post‐GAHT, testosterone concentrations in TW (1.10 ± 0.52 nmol·L−1) were female typical. Average race time for the runners increased by 14.6 ± 5.6% after 31 ± 23 months (range 5–86 months) of GAHT. Changes in training were positively associated with changes in AGs (p = 0.008). Pre‐GAHT and post‐GAHT average AGs of the runners did not differ with or without adjustment (p = 0.304) for training differences. Average race times for the swimmer increased by 5.2 ± 2.3% and FINA score increased by 65 points after 34 months of GAHT. In our sample of TW athletes taking GAHT, longer distance events were associated with larger decrements in performance compared with shorter distance events, with exercise training helping attenuate these decrements. Event demands and exercise training may be important considerations in understanding the effects of GAHT on athletic performance in TW athletes. Highlights This is the first study in TW athletes to use both retrospective and prospective methods to assess decreases in athletic performance, changes in training and hormone concentrations both pre‐GAHT and post‐GAHT. Nine TW runners had decreases in performance of approximately 15% with > 1 year of GAHT whereas 1 TW swimmer had decreases in performance of approximately 5%. In both running and swimming, the performance decrements were greater in longer‐duration (> 240 s) events than in shorter‐duartion (< 120 s) events. Using sport specific evaluation methods, the TW runners were collectively equally as competitive in the men's category pre‐GAHT and the women's category post‐GAHT, whereas the swimmer was more competitive post‐GAHT in the women's category than in the men's category pre‐GAHT.

The ‘cycling hour‐record’ is one of the most prestigious events in cycling. However, little detailed analysis of such attempts is available. In preparation for a successful cycling hour‐record attempt, an elite cyclist performed a full‐hour simulation to provide insights into performance, physiological, aerodynamic and biomechanical limitations that could be identified in the preparation for a subsequent official attempt. Performance (speed, lap time, power and cadence), physiological (heart rate and estimated body temperature), aerodynamic (CDA, helmet angle, rotation and rock) and biomechanical (helmet, thigh and foot position changes) measurements were made throughout the attempt, in which an even‐pacing strategy was employed where the point of task failure was defined as the lap which the rider could no longer perform at the targeted lap split (16.6 s) or quicker. The cyclist did not achieve the target distance (54,000 m) during the simulation. The final distance achieved for the hour was 53,250 m. Task failure occurred at 38 min and 33 s (lap 139/34,750 m) into the simulation. Notably, there was a decrease in power output, accompanied with an increase in the estimated body temperature, changes in pedalling kinematics and an increase in aerodynamic drag. The reduction in performance (leading to task failure) during a cycling hour record simulation is underpinned by a decrease in power output as well as an increase in aerodynamic drag due to biomechanical changes in the cycling technique. Highlights An elite cyclist performed a cycling hour record simulation to provide insights into physiological, aerodynamic and biomechanical determinants of performance. An even‐pacing strategy was employed where the point of task failure was defined as the lap which the cyclist could no longer perform at the targeted lap split (16.6 s) or quicker. Task failure occurred at 38 min and 33 s (lap 139/34,750 m) into the simulation, and they failed to achieve target distance (54,000 m), achieving 53,250 m. The reduction in performance (leading to task failure) was underpinned by a decrease in power output as well as an increase in aerodynamic drag due to biomechanical changes in the cycling technique.

The response of calf muscle strength, resting ( R bf ) and post-occlusive (PO bf ) blood flow were investigated following 4 weeks resistance training with and without blood flow restriction in a matched leg design. Sixteen untrained females performed unilateral plantar-flexion low-load resistance training (LLRT) at either 25% ( n  = 8) or 50% ( n  = 8) one-repetition maximum (1 RM). One limb was trained with unrestricted blood flow whilst in the other limb blood flow was restricted with the use of a pressure applied cuff above the knee (110 mmHg). Regardless of the training load, peak PO bf , measured using venous occlusion plethysmography increased when LLRT was performed with blood flow restriction compared to no change following LLRT with unrestricted blood flow. A significant increase ( P  < 0.05) in the area under the blood time–flow curve was also observed following LLRT with blood flow restriction when compared LLRT with unrestricted blood flow. No changes were observed in R bf between groups following training. Maximal dynamic strength (1 RM), maximal voluntary contraction and isokinetic strength at 0.52 and 1.05 rad s −1 also increased ( P  < 0.05) by a greater extent following resistance training with blood flow restriction. Moreover, 1 RM increased to a greater extent following training at 50% 1 RM compared to 25% 1 RM. These results suggest that 4 weeks LLRT with blood flow restriction provides a greater stimulus to increase peak PO bf as well as strength parameters than LLRT with unrestricted blood flow.

Tissue engineered skeletal muscle allows investigation of the cellular and molecular mechanisms that regulate skeletal muscle pathology. The fabricated model must resemble characteristics of tissue and incorporate cost-effective and high content primary human tissue. Current models are limited by low throughput due to the complexities associated with recruiting tissue donors, donor specific variations, as well as cellular senescence associated with passaging. This research presents a method using fused deposition modeling (FDM) and laser sintering (LS) 3D printing to generate reproducible and scalable tissue engineered primary human muscle, possessing aligned mature myotubes reminiscent of tissue. Many existing models are bespoke causing variability when translated between laboratories. To this end, a scalable model has been developed (25-500 μL construct volumes) allowing fabrication of mature primary human skeletal muscle. This research provides a strategy to overcome limited biopsy cell numbers, enabling high throughput screening of functional human tissue.

The power–duration relationship describes the time to exhaustion for exercise at different intensities. It is believed to be a “fundamental bioenergetic property of living systems” that this relationship is hyperbolic. Indeed, the hyperbolic (a.k.a. critical-power) model which formalises this belief is the dominant tool for describing and predicting high-intensity exercise performance, e.g. in cycling, running, rowing or swimming. However, the hyperbolic model is now the focus of a heated debate in the literature because it unrealistically represents efforts that are short (< 2 min) or long (> 15 min). We contribute to this debate by demonstrating that the power–duration relationship is more adequately represented by an alternative, power-law model. In particular, we show that the often-observed good fit of the hyperbolic model between 2 and 15 min should not be taken as proof that the power–duration relationship is hyperbolic. Rather, in this range, a hyperbolic function just happens to approximate a power law fairly well. We also prove mathematical results which suggest that the power-law model is a safer tool for pace selection than the hyperbolic model and that the former more naturally models fatigue than the latter.

Superoxide dismutase-rich Tetraselmis chuii (T. chuii) is derived from marine microalgae and has been reported to increase gene expression of nuclear factor erythroid 2-related factor 2 (NRF2) and related antioxidant enzymes in myoblast tissue culture models. Human research has indicated that T. chuii supplementation can improve recovery from exercise-induced muscle damage, but its effects on endurance exercise performance and the molecular bases that may underlie any ergogenic effects are unclear. Healthy participants underwent 14 days of supplementation with 25 mg·day−1T. chuii and placebo in a randomized, double-blind, crossover experimental design. Prior to and following each supplementation period, participants completed a high-intensity cycling test to assess time to exhaustion and peak oxygen uptake (V˙O2peak). A resting skeletal muscle biopsy was collected after both supplementation periods to assess gene expression changes. Compared to pre-supplementation values, V˙O2peak was increased following T. chuii (p = 0.013) but not placebo (p = 0.66). Fold-change in glutathione peroxidase 7 [(GPX7) 1.26 ± 1.37], glutathione-disulfide reductase [(GSR) 1.22 ± 1.41], glutathione S-transferase Mu 3 [(GSTM3) 1.34 ± 1.49], peroxiredoxin 6 [(PRDX6) 1.36 ± 1.57], extracellular signal-regulated kinase 3 [(ERK3) 1.92 ± 2.42], NRF2 (1.62 ± 2.16), p38 alpha [(p38a) 1.33 ± 1.58] and sirtuin 1 [(SIRT1) 1.73 ± 2.25] gene expression were higher after T. chuii compared to placebo supplementation (p < 0.05). Short-term T. chuii supplementation increased V˙O2peak and skeletal muscle gene expression of key enzymatic antioxidants (GPX7, GSR, GSTM3, and PRDX6), signalling kinases (ERK3 and p38a), post-translational regulators (SIRT1), and transcription factors (NRF2) that may protect against cellular stress insults.

Purpose Previous investigations to establish factors influencing the blood flow restriction (BFR) stimulus have determined cuff pressures required for complete arterial occlusion, which does not reflect the partial restriction prescribed for this training technique. This study aimed to establish characteristics that should be accounted for when prescribing cuff pressures required for partial BFR. Methods Fifty participants were subjected to incremental blood flow restriction of the upper and lower limbs by proximal pneumatic cuff inflation. Popliteal and brachial artery diameter, blood velocity and blood flow was assessed with Doppler ultrasound. Height, body mass, limb circumference, muscle–bone cross-sectional area, adipose thickness (AT) and arterial blood pressure were measured and used in different models of hierarchical linear regression to predict the pressure at which 60 % BFR (partial occlusion) occurred. Results Combined analysis revealed a difference in cuff pressures required to elicit 60 % BFR in the popliteal (111 ± 12 mmHg) and brachial arteries (101 ± 12 mmHg). MAP ( r  = 0.58) and AT ( r  = −0.45) were the largest independent determinants of lower and upper body partial occlusion pressures. However, greater variance was explained by upper and lower limb regression models composed of DBP and BMI (48 %), and arm AT and DBP (30 %), respectively. Conclusion Limb circumference has limited impact on the cuff pressure required for partial blood flow restriction which is in contrast to its recognised relationship with complete arterial occlusion. The majority of the variance in partial occlusion pressure remains unexplained by the predictor variables assessed in the present study.

Blood flow restriction (BFR) is increasingly being used to enhance aerobic performance in endurance athletes. This study examined physiological responses to BFR applied in recovery phases within a high‐intensity interval training (HIIT) session in trained cyclists. Eleven competitive road cyclists (mean ± SD, age: 28 ± 7 years, body mass: 69 ± 6 kg, peak oxygen uptake: 65 ± 9 mL · kg−1 · min−1) completed two randomised crossover conditions: HIIT with (BFR) and without (CON) BFR applied during recovery phases. HIIT consisted of six 30‐s cycling bouts at an intensity equivalent to 85% of maximal 30‐s power (523 ± 93 W), interspersed with 4.5‐min recovery. BFR (200 mmHg, 12 cm cuff width) was applied for 2‐min in the early recovery phase between each interval. Pulmonary gas exchange (V̇O2, V̇CO2, and V̇E), tissue oxygen saturation index (TSI), heart rate (HR), and serum vascular endothelial growth factor concentration (VEGF) were measured. Compared to CON, BFR increased V̇CO2 and V̇E during work bouts (both p < 0.05, dz < 0.5), but there was no effect on V̇O2, TSI, or HR (p > 0.05). In early recovery, BFR decreased TSI, V̇O2, V̇CO2, and V̇E (all p < 0.05, dz > 0.8) versus CON, with no change in HR (p > 0.05). In late recovery, when BFR was released, V̇O2, V̇CO2, V̇E, and HR increased, but TSI decreased versus CON (all p < 0.05, dz > 0.8). There was a greater increase in VEGF at 3‐h post‐exercise in BFR compared to CON (p < 0.05, dz > 0.8). Incorporating BFR into HIIT recovery phases altered physiological responses compared to exercise alone. Highlights Blood flow restriction (BFR) during high‐intensity interval training recovery phases increased acute physiological perturbations and angiogenic markers compared to interval training alone. During the early recovery phases of high‐intensity interval cycling, BFR decreased muscle oxygenation, V̇O2, V̇CO2, and V̇E compared to CON condition with unrestricted recovery.

It has been suggested that circulating hormones and cytokines are important in the adaptive response to low-load resistance training (LLRT) with blood flow restriction (BFR); however, their response following this type of training in older men is unclear. Seven healthy older men (age 71.0 ± 6.5 year, height 1.77 ± 0.05 m, body mass 80.0 ± 7.5 kg; mean ± SD) performed five sets of unilateral LLRT knee extensions (20 % 1-RM) of both limbs, with or without BFR in a counterbalanced order. For the BFR condition, a pressure cuff was applied on the upper thigh and inflated to ~110 mmHg. Venous blood samples were taken at rest and 30-, 60- and 120-min post-exercise and measured for plasma concentrations of growth hormone (GH), insulin-like growth factor 1 (IGF-1), vascular endothelial growth factor (VEGF), cortisol and interleukin-6 (IL-6). GH increased ( P  < 0.05) from rest to 30-min post-exercise and was greater ( P  < 0.05) during LLRT with BFR than without. VEGF was significantly ( P  < 0.05) elevated from resting levels at 30-, 60- and 120-min post-exercise following LLRT with BFR with no change seen following LLRT without BFR. IL-6 increased ( P  < 0.05) from 30- to 60-min post-exercise and remained elevated at 120-min post-exercise in both conditions. Cortisol and IGF-1 were unaffected following exercise. In conclusion, a single bout of LLRT with BFR increases the circulating concentrations of GH and VEGF in older men and may explain the skeletal muscle and peripheral vascular adaptations observed following training with BFR.