Reliable and sensitive physical testing of elite trapeze sailors

It was investigated whether a newly developed discipline-specific test for elite-level trapeze sailors is reliable and sensitive. Furthermore, the physical demands of trapeze sailing were examined. In part 1, 9 national team athletes were accustomed to a simulated sailing test, which subsequently was completed on 4 occasions to determine test reliability and sensitivity to manipulations in body weight. Rope-pulling mean power output (MPO), oxygen consumption (VO₂ ), heart rate (HR), and blood lactate values were acquired in all trials. In part 2, 6 sailors completed on-water racing with concurrent measurements of VO₂ , HR, and blood lactate. VO_2max was determined during an incremental treadmill running test. Typical error, minimal difference, and ICC for average MPO in the test were 1.3%, 1.7%, and 0.99%, respectively. Adding 4 kg of external body weight caused a decrease in average MPO (270 ± 45W vs 265 ± 45W, P < .05) and an increase in VO₂ (2.44 ± 0.23 L·min^-1 vs 2.55 ± 0.26 L·min^-1 , P < .01). VO₂ , HR, and blood lactate during on-water sailing were 54.5% ± 7.2% VO_2max , 75.1% ± 3.1% HR_max , and 5.8 ± 2.7 mmol·L^-1 , respectively. However, VO₂ and HR were substantially higher for periods of the race as peak values were 83.5% ± 11.4% and 89.9% ± 1.7% of max, respectively. In conclusion, the present test is reliable and sensitive, thus providing a sailing-specific alternative to traditional physical testing of elite trapeze sailors. Additionally, on-water racing requires moderate aerobic energy production, although oxygen consumption can approach maximal levels for short periods of time.

Validity of physical activity and cardiorespiratory fitness in the Danish cohort "Diet, Cancer and Health-Next Generations"

Valid assessments of physical activity (PA) and cardiorespiratory fitness (CRF) are essential in epidemiological studies to define dose-response relationship for formulating thorough recommendations of an appropriate pattern of PA to maintain good health. The aim of this study was to validate the Danish step test, the physical activity questionnaire Active-Q, and self-rated fitness against directly measured maximal oxygen uptake (VO₂ max). A population-based subsample (n=125) was included from the "Diet, Cancer and Health-Next Generations" (DCH-NG) cohort which is under establishment. Validity coefficients, which express the correlation between measured and "true" exposure, were calculated, and misclassification across categories was evaluated. The validity of the Danish step test was moderate (women: r=.66, and men: r=.56); however, men were systematically underestimated (43% misclassification). When validating the questionnaire-derived measures of PA, leisure-time physical activity was not correlated with VO₂ max. Positive correlations were found for sports overall, but these were only significant for men: total hours per week of sports (r=.26), MET-hours per week of sports (r=.28) and vigorous sports (0.28) alone were positively correlated with VO₂ max. Finally, the percentage of misclassification was low for self-rated fitness (women: 9% and men: 13%). Thus, self-rated fitness was found to be a superior method to the Danish step test, as well as being less cost prohibitive and more practical than the VO₂ max method. Finally, even if correlations were low, they support the potential for questionnaire outcomes, particularly sports, vigorous sports, and self-rated fitness to be used to estimate CRF.

Hiking strap force decreases during sustained upwind sailing

The hypothesis, that sailing upwind in wind speeds above 12 knots causes fatigue, which manifests as a reduction in exerted hiking strap force and/or maximal isometric voluntary contraction force (MVC) of the knee extensors, was evaluated. Additionally, it was investigated if a relationship exists between maximal exerted hiking force (hMVC) and sailing performance. In part 1 of the study, 12 national level athletes sailed upwind for 2 × 10 min while hiking strap forces were continuously acquired. Before, in between and after sailing periods, the MVC of the knee extensors was measured. In part 2 of the study, hMVC was measured dry land in a hiking bench and correlated with the overall results at a national championship. Hiking strap force decreased from the first to the last minute in both 10 min sailing periods (430 ± 131 vs. 285 ± 130 N, P < .001 and 369 ± 74 vs. 267 ± 97 N, P < .001, respectively), but MVC was similar before, between and after the two 10 min sailing periods (878 ± 215 vs. 852 ± 202 vs. 844 ± 211 130 N). In part 2, a significant positive correlation (r² = 0.619, P < .01) was observed between hMVC and regatta results. In conclusion, upwind sailing in wind speeds above 12 knots causes sailing-specific fatigue as evidenced by a marked reduction in exerted hiking strap force. However, MVC of the knee extensors was not compromised ∼45 s after hiking was terminated. Additionally, sailing performance is related to maximal hiking force.

Use of nutritional supplements by Danish elite athletes and fitness customers

The nutritional supplement (NS) industry is one of the fastest growing in the world, and NS use in Denmark is among the highest in Europe. However, the exact use in elite athletes and fitness customers targeted for doping control is unknown. Information from 634 doping control forms obtained in 2014 was evaluated (elite athletes: n = 361; fitness customers: n = 273). The majority of female (92.6%) and male (85.0%) elite athletes and female (100.0%) and male (94.0%) fitness customers declared using one or more NS. The use of non-ergogenic NS was more prevalent in women than in men and in younger (15-34 years) compared with older (35-49 years) subjects, but it was less prevalent in intermittent compared with endurance and power/strength sports. Additionally, fitness customers who tested positive for doping also reported using more NS than subjects testing negative, indicating an association between NS and doping abuse. The present results demonstrate a very high prevalence of NS usage in both elite athletes and fitness customers. This highlights the importance of a strong national regulation of NS to avoid contamination of NS with doping substances.

Hypoxia increases exercise heart rate despite combined inhibition of β-adrenergic and muscarinic receptors

Hypoxia increases the heart rate response to exercise, but the mechanism(s) remains unclear. We tested the hypothesis that the tachycardic effect of hypoxia persists during separate, but not combined, inhibition of β-adrenergic and muscarinic receptors. Nine subjects performed incremental exercise to exhaustion in normoxia and hypoxia (fraction of inspired O2 = 12%) after intravenous administration of 1) no drugs (Cont), 2) propranolol (Prop), 3) glycopyrrolate (Glyc), or 4) Prop + Glyc. HR increased with exercise in all drug conditions ( P < 0.001) but was always higher at a given workload in hypoxia than normoxia ( P < 0.001). Averaged over all workloads, the difference between hypoxia and normoxia was 19.8 ± 13.8 beats/min during Cont and similar (17.2 ± 7.7 beats/min, P = 0.95) during Prop but smaller ( P < 0.001) during Glyc and Prop + Glyc (9.8 ± 9.6 and 8.1 ± 7.6 beats/min, respectively). Cardiac output was enhanced by hypoxia ( P < 0.002) to an extent that was similar between Cont, Glyc, and Prop + Glyc (2.3 ± 1.9, 1.7 ± 1.8, and 2.3 ± 1.2 l/min, respectively, P > 0.4) but larger during Prop (3.4 ± 1.6 l/min, P = 0.004). Our results demonstrate that the tachycardic effect of hypoxia during exercise partially relies on vagal withdrawal. Conversely, sympathoexcitation either does not contribute or increases heart rate through mechanisms other than β-adrenergic transmission. A potential candidate is α-adrenergic transmission, which could also explain why a tachycardic effect of hypoxia persists during combined β-adrenergic and muscarinic receptor inhibition.

Acute hyperhydration reduces athlete biological passport OFF-hr score

Anecdotal evidence suggests that athletes hyperhydrate to mask prohibited substances in urine and potentially counteract suspicious fluctuations in blood parameters in the athlete biological passport (ABP). It is examined if acute hyperhydration changes parameters included in the ABP. Twenty subjects received recombinant human erythropoietin (rhEPO) for 3 weeks. After 10 days of rhEPO washout, 10 subjects ingested normal amount of water (∼ 270 mL), whereas the remaining 10 ingested a 1000 mL bolus of water. Blood variables were measured 20, 40, 60, and 80 min after ingestion. Three days later, the subjects were crossed-over with regard to water ingestion and the procedure was repeated. OFF-hr was reduced by ∼ 4%, ∼ 3%, and ∼ 2% at 40, 60, and 80 min, respectively, after drinking 1000 mL of water, compared with normal water ingestion (P < 0.05). Forty percent of the subjects were identified with atypical blood profiles (99% specificity level) before drinking 1000 mL of water, whereas 11% (n = 18), 10% and 11% (n = 18) were identified 40, 60, and 80 min, respectively, after ingestion. This was different (P < 0.05) compared with normal water intake, where 45% of the subjects were identified before ingestion, and 54% (n = 19), 45%, and 47% (n = 19) were identified 40, 60, and 80 min, respectively, after ingestion. In conclusion, acute hyperhydration reduces ABP OFF-hr and reduces ABP sensitivity.

Oral quercetin supplementation hampers skeletal muscle adaptations in response to exercise training

We aimed to test exercise-induced adaptations on skeletal muscle when quercetin is supplemented. Four groups of rats were tested: quercetin sedentary, quercetin exercised, placebo sedentary, and placebo exercised. Treadmill exercise training took place 5 days a week for 6 weeks. Quercetin groups were supplemented with quercetin, via gavage, on alternate days throughout the experimental period. Sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor γ coactivator-1α mRNA levels, mitochondrial DNA (mtDNA) content, and citrate synthase (CS) activity were measured on quadriceps muscle. Redox status was also quantified by measuring muscle antioxidant enzymatic activity and oxidative damage product, such as protein carbonyl content (PCC). Quercetin supplementation increased oxidative damage in both exercised and sedentary rats by inducing higher amounts of PCC (P < 0.001). Quercetin supplementation caused higher catalase (P < 0.001) and superoxide dismutase (P < 0.05) activity in the non-exercised animals, but not when quercetin is supplemented during exercise. Quercetin supplementation increased SIRT1 expression, but when quercetin is supplemented during exercise, this effect is abolished (P < 0.001). The combination of exercise and quercetin supplementation caused lower (P < 0.05) mtDNA content and CS activity when compared with exercise alone. Quercetin supplementation during exercise provides a disadvantage to exercise-induced muscle adaptations.

Four weeks of normobaric "live high-train low" do not alter muscular or systemic capacity for maintaining pH and K⁺ homeostasis during intense exercise

It was investigated if athletes subjected to 4 wk of living in normobaric hypoxia (3,000 m; 16 h/day) while training at 800-1,300 m ["live high-train low" (LHTL)] increase muscular and systemic capacity for maintaining pH and K(+) homeostasis as well as intense exercise performance. The design was double-blind and placebo controlled. Mean power during 30-s all-out cycling was similar before and immediately after LHTL (650 ± 31 vs. 628 ± 32 W; n = 10) and placebo exposure (658 ± 22 vs. 660 ± 23 W; n = 6). Supporting the performance data, arterial plasma pH, lactate, and K(+) during submaximal and maximal exercise were also unaffected by the intervention in both groups. In addition, muscle buffer capacity (in mmol H(+)·kg dry wt(-1)·pH(-1)) was similar before and after in both the LHTL (140 ± 12 vs. 140 ± 16) and placebo group (145 ± 2 vs. 140 ± 3). The expression of sarcolemmal H(+) transporters (Na(+)/H(+) exchanger 1, monocarboxylate transporters 1 and 4), as well as expression of Na(+)-K(+) pump subunits-α(1), -α(2), and -β(1) was also similar before and after the intervention. In conclusion, muscular and systemic capacity for maintaining pH and K(+) balance during exercise is similar before and after 4 wk of placebo-controlled normobaric LHTL. In accordance, 30-s all-out sprint ability was similar before and after LHTL.

Determinants of time trial performance and maximal incremental exercise in highly trained endurance athletes

Human endurance performance can be predicted from maximal oxygen consumption (Vo(2max)), lactate threshold, and exercise efficiency. These physiological parameters, however, are not wholly exclusive from one another, and their interplay is complex. Accordingly, we sought to identify more specific measurements explaining the range of performance among athletes. Out of 150 separate variables we identified 10 principal factors responsible for hematological, cardiovascular, respiratory, musculoskeletal, and neurological variation in 16 highly trained cyclists. These principal factors were then correlated with a 26-km time trial and test of maximal incremental power output. Average power output during the 26-km time trial was attributed to, in order of importance, oxidative phosphorylation capacity of the vastus lateralis muscle (P = 0.0005), steady-state submaximal blood lactate concentrations (P = 0.0017), and maximal leg oxygenation (sO(2LEG)) (P = 0.0295), accounting for 78% of the variation in time trial performance. Variability in maximal power output, on the other hand, was attributed to total body hemoglobin mass (Hb(mass); P = 0.0038), Vo(2max) (P = 0.0213), and sO(2LEG) (P = 0.0463). In conclusion, 1) skeletal muscle oxidative capacity is the primary predictor of time trial performance in highly trained cyclists; 2) the strongest predictor for maximal incremental power output is Hb(mass); and 3) overall exercise performance (time trial performance + maximal incremental power output) correlates most strongly to measures regarding the capability for oxygen transport, high Vo(2max) and Hb(mass), in addition to measures of oxygen utilization, maximal oxidative phosphorylation, and electron transport system capacities in the skeletal muscle.

Contraction-induced changes in skeletal muscle Na(+), K(+) pump mRNA expression - importance of exercise intensity and Ca(2+)-mediated signalling

AIM

To investigate if exercise intensity and Ca(2+) signalling regulate Na(+),K(+) pump mRNA expression in skeletal muscle.

METHODS

The importance of exercise intensity was evaluated by having trained and untrained humans perform intense intermittent and prolonged exercise. The importance of Ca(2+) signalling was investigated by electrical stimulation of rat soleus and extensor digitorum longus (EDL) muscles in combination with studies of cell cultures.

RESULTS

Intermittent cycling exercise at approximately 85% of VO(2peak) increased (P < 0.05) alpha1 and beta1 mRNA expression approximately 2-fold in untrained and trained subjects. In trained subjects, intermittent exercise at approximately 70% of VO(2peak) resulted in a less (P < 0.05) pronounced increase ( approximately 1.4-fold; P < 0.05) for alpha1 and no change in beta1 mRNA. Prolonged low intensity exercise increased (P < 0.05) mRNA expression of alpha1 approximately 3.0-fold and alpha2 approximately 1.8-fold in untrained but not in trained subjects. Electrical stimulation of rat soleus, but not EDL, muscle increased (P < 0.05) alpha1 mRNA expression, but not when combined with KN62 and cyclosporin A incubation. Ionomycin incubation of cultured primary rat skeletal muscle cells increased (P < 0.05) alpha1 and reduced (P < 0.001) alpha2 mRNA expression and these responses were abolished (P < 0.05) by co-incubation with cyclosporin A or KN62.

CONCLUSION

(1) Exercise-induced increases in Na(+),K(+) pump alpha1 and beta1 mRNA expression in trained subjects are more pronounced after high- than after moderate- and low-intensity exercise. (2) Both prolonged low and short-duration high-intensity exercise increase alpha1 mRNA expression in untrained subjects. (3) Ca(2+)(i) regulates alpha1 mRNA expression in oxidative muscles via Ca(2+)/calmodulin-dependent protein kinase (CaMK) and calcineurin signalling pathways.