Relevance of individual characteristics for thermoregulation during exercise in a hot-dry environment

The aim of this study was to investigate the relevance of individual characteristics for thermoregulation during prolonged cycling in the heat. For this purpose, 28 subjects cycled for 60 min at 60% VO_2peak in a hot-dry environment (36 ± 1°C; 25 ± 2% relative humidity, airflow 2.5 m/s). Subjects had a wide range of body mass (99–43 kg), body surface area (2.2–1.4 m²), body fatness (28–5%) and aerobic fitness level (VO_2peak = 5.0–2.1 L/min). At rest and during exercise, rectal and mean skin temperatures were measured to calculate the increase in body temperature (ΔT _body) during the trial. Net metabolic heat production (M _NET) and potential heat loss (by means of evaporation, radiation and convection) were calculated. Although subjects exercised at the same relative intensity, ΔT _body presented high between-subjects variability (range from 0.44 to 1.65°C). ΔT _body correlated negatively with body mass (r = −0.49; P < 0.01), body surface area (r = −0.47; P < 0.01) and T_body at rest (r = −0.37; P < 0.05), but it did not significantly correlate with body fatness (r = 0.12; P > 0.05). ΔT _body positively correlated with the body surface area/mass ratio (r = 0.46; P < 0.01) and the difference between M _NET and potential heat loss (r = 0.56; P < 0.01). In conclusion, a large body size (mass and body surface area) is beneficial to reduce ΔT _body during cycling exercise in the heat. However, subjects with higher absolute heat production (more aerobically fit) accumulate more heat because heat production may exceed potential heat loss (uncompensability).     

Aerobic fitness testing in 6- to 9-year-old children: reliability and validity of a modified Yo–Yo IR1 test and the Andersen test

This study analysed the reliability and validity of two intermittent running tests (the Yo–Yo IR1 test and the Andersen test) as tools for estimating VO_2max in children under the age of 10. Two groups, aged 6–7 years (grade 0, n = 18) and 8–9 years (grade 2, n = 16), carried out two repetitions of a modified Yo–Yo IR1 test (2 × 16 m) and the Andersen test, as well as an incremental treadmill test, to directly determine the VO_2max. No significant differences were observed in test–retest performance of the Yo–Yo IR1 test [693 ± 418 (±SD) and 670 ± 328 m, r ² = 0.79, CV = 19%, p > 0.05, n = 32) and the Andersen test (988 ± 77 and 989 ± 87 m, r ² = 0.86, CV = 3%, p > 0.05, n = 31). The Yo–Yo IR1 (r ² = 0.47, n = 31, p < 0.002) and Andersen test performance (r ² = 0.53, n = 32, p < 0.001) correlated with the VO_2max. Yo–Yo IR1 performance correlated with Andersen test performance (r ² = 0.74, n = 32, p < 0.0001). In conclusion, the Yo–Yo IR1 and the Andersen tests are reproducible and can be used as an indicator of aerobic fitness for 6- to 9-year-old children.     

Aerobic power and peak power of elite America’s Cup sailors

Big-boat yacht racing is one of the only able bodied sporting activities where standing arm-cranking (‘grinding’) is the primary physical activity. However, the physiological capabilities of elite sailors for standing arm-cranking have been largely unreported. The purpose of the study was to assess aerobic parameters, VO_2peak and onset of blood lactate (OBLA), and anaerobic performance, torque–crank velocity and power–crank velocity relationships and therefore peak power (P _max) and optimum crank-velocity (ω_opt), of America’s Cup sailors during standing arm-cranking. Thirty-three elite professional sailors performed a step test to exhaustion, and a subset of ten grinders performed maximal 7 s isokinetic sprints at different crank velocities, using a standing arm-crank ergometer. VO_2peak was 4.7 ± 0.5 L/min (range 3.6–5.5 L/min) at a power output of 332 ± 44 W (range 235–425 W). OBLA occurred at a power output of 202 ± 31 W (61% of W_max) and VO₂ of 3.3 ± 0.4 L/min (71% of VO_2peak). The torque–crank velocity relationship was linear for all participants (r = 0.9 ± 0.1). P _max was 1,420 ± 37 W (range 1,192–1,617 W), and ω_opt was 125 ± 6 rpm. These data are among the highest upper-body anaerobic and aerobic power values reported. The unique nature of these athletes, with their high fat-free mass and specific selection and training for standing arm cranking, likely accounts for the high values. The influence of crank velocity on peak power implies that power production during on-board ‘grinding’ may be optimised through the use of appropriate gear-ratios and the development of efficient gear change mechanisms.     

Describing individual variation in local sweating during exercise in a temperate environment

It has been previously demonstrated that the individual variation in whole-body sweat rate is described by differences in each participant’s heat balance status. It was hypothesized that the individual variation in local sweat rate of the forehead (LSR_head) and forearm (LSR_arm) would be similarly described using a whole-body heat balance approach, specifically the ratio of evaporation required for heat balance relative to the maximum evaporation possible (i.e. E _req:E _max). Twelve males cycled at 60% [(V)\dot]\textO _{2 \textmax} \dot{V}{\text{O}}_{{ 2 {\text{max}}}} for 60 min at 24.9 ± 0.5°C, 31 ± 14% relative humidity. Rectal (T _re) and aural canal (T _au) temperatures as well as mean skin temperature ( [`(T)]<sub>\textsk</sub> \bar{T}_{\text{sk}} ), metabolic energy expenditure (M) and rate of external work (W) were measured throughout. In addition, whole-body sweat rate at steady state (WBSR<sub>ss</sub>) was estimated using the change in body mass over the last 15 min of exercise, with LSR<sub>head</sub> and LSR<sub>arm</sub> estimated using technical absorbent patches applied between the 50th and 55th minute. WBSR<sub>ss</sub> significantly correlated with M–W (r = 0.66, P = 0.021), E <sub>req</sub> (r = 0.69, P = 0.013) and E <sub>req</sub>:E <sub>max</sub> (r = 0.87, P < 0.001); LSR<sub>head</sub> was significantly correlated with E <sub>req</sub>:E <sub>max</sub> (r = 0.82, P = 0.001), but not M–W (r = 0.31, P = 0.328) or E <sub>req</sub> (r = 0.38, P = 0.227); and LSR<sub>arm</sub> significantly correlated with E <sub>req</sub> (r = 0.62, P = 0.031) and E <sub>req</sub>:E <sub>max</sub> (r = 0.78, P = 0.003) but not M–W (r = 0.56, P = 0.059). None of WBSR<sub>ss</sub>, LSR<sub>head</sub> or LSR<sub>arm</sub> significantly correlated with any variations in T <sub>re</sub>, T <sub>au</sub> or [`(T)]_\textb \bar{T}_{\text{b}} (i.e. 0.8T _re + 0.2 [`(T)]_\textsk \bar{T}_{\text{sk}} ). Secondary analyses also demonstrated that both LSR_head (r = 0.79, P = 0.002) and LSR_arm (r = 0.89, P < 0.001) correlated with WBSR_ss. In conclusion, the individual variation in WBSR_ss, LSR_head and LSR_arm is described by the ratio of E _req relative to E _max.     

Length Adaptation of the Passive-to-Active Tension Ratio in Rabbit Detrusor

The passive and active length–tension (L–T _p and L–T _a) relationships in airway, vascular, and detrusor smooth muscles can adapt with length changes and/or multiple contractions. The present objectives were to (1) determine whether short-term adaptation at one muscle length shifts the entire L–T _a curve in detrusor smooth muscle (DSM), (2) compare adaptation at shorter versus longer lengths, and (3) determine the effect of adaptation on the T _p/T _a ratio. Results showed that multiple KCl-induced contractions on the descending limb of the original L–T _a curve adapted DSM strips to that length and shifted the L–T _a curve rightward. Peak T _a at the new length was not different from the original peak T _a, and the L–T _p curve shifted rightward with the L–T _a curve. Multiple contractions on the ascending limb increased both T _a and T _p. In contrast, multiple contractions on the descending limb increased T _a but decreased T _p. The T _p/T _a ratio on the original descending limb adapted from 0.540 ± 0.084 to 0.223 ± 0.033 (mean ± SE, n = 7), such that it was not different from the ratio of 0.208 ± 0.033 at the original peak T _a length, suggesting a role of length adaptation may be to maintain a desirable T _p/T _a ratio as the bladder fills and voids over a broad DSM length range.     

Effectiveness of short-term heat acclimation for highly trained athletes

Effectiveness of short-term acclimation has generally been undertaken using untrained and moderately-trained participants. The purpose of this study was to determine the impact of short-term (5-day) heat acclimation on highly trained athletes. Eight males (mean ± SD age 21.8 ± 2.1 years, mass 75.2 ± 4.6 kg, [(V)\dot] \dot{V}O_2peak 4.9 ± 0.2 L min⁻¹ and power output 400 ± 27 W) were heat acclimated under controlled hyperthermia (rectal temperature 38.5°C), for 90-min on five consecutive days (T _a = 39.5°C, 60% relative humidity). Acclimation was undertaken with dehydration (no fluid-intake) during daily bouts. Participants completed a rowing-specific, heat stress test (HST) 1 day before and after acclimation (T _a = 35°C, 60% relative humidity). HST consisted 10-min rowing at 30% peak power output (PPO), 10 min at 60% PPO and 5-min rest before a 2-km performance test, without feedback cues. Participants received 250 mL fluid (4% carbohydrate; osmolality 240–270 mmol kg⁻¹) before the HST. Body mass loss during acclimation bouts was 1.6 ± 0.3 kg (2.1%) on day 1 and 2.3 ± 0.4 kg (3.0%) on day 5. In contrast, resting plasma volume increased by 4.5 ± 4.5% from day 1 to 5 (estimated from [Hb] & Hct). Plasma aldosterone increased at rest (52.6 pg mL⁻¹; p = 0.03) and end-exercise (162.4 pg mL⁻¹; p = 0.00) from day 1 to 5 acclimation. During the HST T _re and f _c were lowered 0.3°C (p = 0.00) and 14 b min⁻¹ (p = 0.00) after 20-min exercise. The 2-km performance time (6.52.7 min) improved by 4 s (p = 0.00). Meaningful physiological and performance improvements occurred for highly trained athletes using a short-term (5-day) heat acclimation under hyperthermia control, with dehydration.     

Relationship between plasma thyroid hormones and some biochemical parameters in Iranian Sarabi calves

The thyroid gland has some important endocrine hormones that regulate basal metabolism in various tissues of domestic animals. Thyroid hormones have a central role in animals’ development and their tissue functions. In this study, the relationship between the plasma thyroxine (T₄), triiodothyronine (T₃), free thyroxine (fT₄), free triiodothyronine (fT₃), triglyceride, cholesterol, glucose, total protein, and albumin concentrations as well as albumin/globulin ratio in different ages of Iranian Sarabi calves was investigated. Blood samples were collected from the jugular vein of 47 clinically healthy calves free from internal and external parasites (grouped according to their age—1–14 days, 1–2, and 3–6 months) in early of winter. The level of thyroid hormones was determined by chemiluminescence, and other parameters were measured by spectrophotometry using commercial kits. Our data from this study indicates that there was no significant difference and correlation in all the studied parameters between age groups and sexes. But we found a significant correlation between plasma T₄ and total protein (P < 0.05, r = 0.600), T₄ and albumin (P < 0.05, r = 0.575), T₃ and fT₃ (P < 0.05, r = 0.610), T₃ and total protein (P < 0.01, r = 0.725), T₃ and glucose (P < 0.01, r = 0.685), and fT₄ and fT₃ (P < 0.05, r = 0.609) concentrations as well as between total protein and albumin/globulin ratio (P < 0.01, r = −0.783).     

Thermoregulation, pacing and fluid balance during mass participation distance running in a warm and humid environment

Deep body temperature (T _c), pacing strategy and fluid balance were investigated during a 21-km road race in a warm and humid environment. Thirty-one males (age 25.3 ± 3.2 years; maximal oxygen uptake 59.1 ± 4.2 ml kg⁻¹ min⁻¹) volunteered for this study. Continuous T _c responses were obtained in 25 runners. Research stations at approximately 3-km intervals permitted accurate assessment of split times and fluid intake. Environmental conditions averaged 26.4°C dry bulb temperature and 81% relative humidity. Peak T _c was 39.8 ± 0.5 (38.5–40.7) °C with 24 runners achieving T _c > 39.0°C, 17 runners ≥39.5°C, and 10 runners ≥40.0°C. In 12 runners attaining peak T _c ≥ 39.8°C, running speed did not differ significantly when T _c was below or above this threshold (208 ± 15 cf. 205 ± 24 m min⁻¹; P = 0.532). Running velocity was the main significant predictor variable of ∆T _c at 21 km (R ² = 0.42, P < 0.001) and was the main discriminating variable between hyperthermic (T _c ≥ 39.8°C) and normothermic runners (T _c < 39.8°C) up to 11.8 km. A reverse J-shaped pacing profile characterised by a marked reduction in running speed after 6.9 km and evidence of an end-spurt in 16 runners was observed. Variables relating to fluid balance were not associated with any T _c parameters or pacing. We conclude that hyperthermia, defined by a deep body temperature greater than 39.5°C, is common in trained individuals undertaking outdoor distance running in environmental heat, without evidence of fatigue or heat illness.     

Indirect measures of human vagal withdrawal during head-up tilt with and without a respiratory acidosis

Human ECG records were analyzed during supine (SUP) rest and whole body 80° head-up tilt (HUT), with a respiratory acidosis (5%CO₂) and breathing room air (RA). HUT increased heart rate in both conditions (RA_SUP 60 ± 13 vs. RA_HUT 79 ± 16; 5%CO_2SUP 63 ± 12 vs. 5%CO_2HUT 79 ± 14 beats min⁻¹) and decreased mean R–R interval, with no changes in the R–R interval standard deviation. When corrected for changes in frequency spectrum total power (NU), the high frequency (0.15–0.4 Hz) component (HF_NU) of heart rate variability decreased (RA_SUP 44.01 ± 21.57 vs. RA_HUT 24.05 ± 13.09; 5%CO_2SUP 69.23 ± 15.37 vs. 5%CO_2HUT 47.64 ± 21.11) without accompanying changes in the low frequency (0.04–0.15 Hz) component (LF_NU) (RA_SUP 52.36 ± 21.93 vs. RA_HUT 66.58 ± 19.49; 5%CO_2SUP 22.97 ± 11.54 vs. 5%CO_2HUT 40.45 ± 21.41). Positive linear relations between the tilt-induced changes (Δ) in HF_NU and R–R interval were recorded for RA (ΔHF_NU = 0.0787(ΔR−R) − 11.3, R ² = 0.79, P < 0.05), and for 5%CO₂ (ΔHF_NU = 0.0334(ΔR−R) + 1.1, R ² = 0.82, P < 0.05). The decreased HF component suggested withdrawal of vagal activity during HUT. For both RA and 5%CO₂, the positive linear relations between ΔHF_NU and ΔR−R suggested that the greater the increase in heart rate with HUT, the greater the vagal withdrawal. However, a reduced range of ΔHF during HUT with respiratory acidosis suggested vagal withdrawal was lower with a respiratory acidosis.     

Cardiac vagal withdrawal and reactivation during repeated rest–exercise transitions

It is not known whether subjects that have higher cardiac vagal reactivation (CVR) during repeated exercise transitions also have higher cardiac vagal withdrawal (CVW) at the onset of exercise, which would lead to better heart rate (HR) regulation during exercise transitions. Therefore, our aims were to investigate: (a) the influence of CVR on CVW during repeated rest–exercise transitions; and (b) the influence of the sympathetic activity on CVR and CVW. Fifty-eight healthy men (22 ± 4 years) performed 20 rest–exercise transitions interspaced by 30 s. In addition, nine healthy men (24 ± 3 years) ingested either 25 mg of atenolol or placebo, on a crossover, double-blind, randomized design, then performed 20 rest–exercise transitions interspaced by 30 s. Cardiac vagal reactivation was assessed by a HR variability index (RMSSD) and CVW by the HR increase at the onset of a valid and reliable cycling protocol. The CVR and CVW responses were associated (partial r ranged from 0.60 to 0.66; p < 0.05). Participants with higher CVR over transitions maintained their CVW over repeated transitions [first transition (mean ± SEM) = 1.59 ± 0.04 vs. 20th = 1.50 ± 0.03 (a.u.), p = 0.24], while participants with lower CVR had a CVW decrease over repeated transitions [first transition (mean ± SEM) = 1.38 ± 0.04 vs. 20th = 1.19 ± 0.03 (a.u.), p < 0.01). In addition, the CVR and CVW over the rest–exercise transitions were similar during atenolol and placebo (ANCOVA interaction p = 0.12 and p = 0.48, respectively). In conclusion, the CVR among repeated rest–exercise transitions influenced the CVW at the onset of exercise, which was not affected by a partial β₁ cardioselective adrenoceptor blockade.     

Monitoring changes in physical performance with heart rate measures in young soccer players

The aim of the present study was to verify the validity of using exercise heart rate (HRex), HR recovery (HRR) and post-exercise HR variability (HRV) during and after a submaximal running test to predict changes in physical performance over an entire competitive season in highly trained young soccer players. Sixty-five complete data sets were analyzed comparing two consecutive testing sessions (3–4 months apart) collected on 46 players (age 15.1 ± 1.5 years). Physical performance tests included a 5-min run at 9 km h⁻¹ followed by a seated 5-min recovery period to measure HRex, HRR and HRV, a counter movement jump, acceleration and maximal sprinting speed obtained during a 40-m sprint with 10-m splits, repeated-sprint performance and an incremental running test to estimate maximal cardiorespiratory function (end test velocity V _Vam-Eval). Possible changes in physical performance were examined for the players presenting a substantial change in HR measures over two consecutive testing sessions (greater than 3, 13 and 10% for HRex, HRR and HRV, respectively). A decrease in HRex or increase in HRV was associated with likely improvements in V _Vam-Eval; opposite changes led to unclear changes in V _Vam-Eval. Moderate relationships were also found between individual changes in HRR and sprint [r = 0.39, 90% CL (0.07;0.64)] and repeated-sprint performance [r = −0.38 (−0.05;−0.64)]. To conclude, while monitoring HRex and HRV was effective in tracking improvements in V _Vam-Eval, changes in HRR were moderately associated with changes in (repeated-)sprint performance. The present data also question the use of HRex and HRV as systematic markers of physical performance decrements in youth soccer players.     

Influence of moderate hypoxia on tolerance to high-intensity exercise

It remains uncertain as how the reduction in systemic oxygen transport limits high-intensity exercise tolerance. 11 participants (5 males; age 35 ± 10 years; peak [(V)\dot]\textO₂ max {\dot{V}\text{O}}_{2} \max 3.5 ± 0.4 L min⁻¹) performed cycle ergometry to the limit of tolerance: (1) a ramp test to determine ventilatory threshold (VT) and peak [(V)\dot]\textO₂ {\dot{V}\text{O}}_{2} ; (2) three to four constant-load tests in order to model the linear P–t ⁻¹ relationship for estimation of intercept (critical power; CP) and slope (AWC). All tests were performed in a random order under moderate hypoxia (FiO₂ = 0.15) and normoxia. The linearity of the P–t ⁻¹ relationship was retained under hypoxia, with a systematic reduction in CP (220 ± 25 W vs. 190 ± 28 W; P < 0.01) but no significant difference in AWC (11.7 ± 5.5 kJ vs. 12.1 ± 4.4 kJ; P > 0.05). However, large individual variations in the change of the latter were observed (−36 to +66%). A significant relationship was found between the % change in CP (r = 0.80, P < 0.01) and both peak [(V)\dot]\textO₂ {\dot{V}\text{O}}_{2} (CP: r = −0.65, P < 0.05) and VT values recorded under normoxia (CP: r = −0.65, P < 0.05). The present study demonstrates the aerobic nature of the intercept of the P–t ⁻¹ relationship, i.e. CP. However, the extreme within-individual changes in AWC do not support the original assumption that AWC reflects a finite energy store. Lower hypoxia-induced decrements in CP were observed in aerobically fitter participants. This study also demonstrates the greater ability these participants have to exercise at supra-CP but close to CP workloads under moderate hypoxia.     

Effects of athletes’ muscle mass on urinary markers of hydration status

To determine if athletes’ muscle mass affects the usefulness of urine specific gravity (U _sg) as a hydration index. Nine rugby players and nine endurance runners differing in the amount of muscle mass (42 ± 6 vs. 32 ± 3 kg, respectively; P = 0.0002) were recruited. At waking during six consecutive days, urine was collected for U _sg analysis, urine osmolality (U _osm), electrolytes ( \mathop U\nolimits_{[\textNa ⁺ ]} {\mathop U\nolimits_{[{\text{Na}}^{ + } ]} }, \mathop U\nolimits_{[\textK ⁺ ]} {\mathop U\nolimits_{[{\text{K}}^{ + } ]} } and \mathop U\nolimits_{[\textCl ^- ]} {\mathop U\nolimits_{[{\text{Cl}}^{ - } ]} }) and protein metabolites (U _[Creatinine], U _[Urea] and U _{[Uric acid]}) concentrations. In addition, fasting blood serum osmolality (S _osm) was measured on the sixth day. As averaged during 6 days, U _sg (1.021 ± 0.002 vs. 1.016 ± 0.001), U _osm (702 ± 56 vs. 554 ± 41 mOsmol kg⁻¹ H₂O), U _[Urea] (405 ± 36 vs. 302 ± 23 mmol L⁻¹) and U _{[Uric acid]} (2.7 ± 0.3 vs. 1.7 ± 0.2 mmol L⁻¹) were higher in rugby players than runners (P < 0.05). However, urine electrolyte concentrations were not different between groups. A higher percentage of rugby players than runners (56 vs. 11%; P = 0.03) could be cataloged as hypohydrated by U _sg (i.e., >1.020) despite S _osm being below 290 mOsmol kg⁻¹ H₂O in all participants. A positive correlation was found between muscle mass and urine protein metabolites (r = 0.47; P = 0.04) and between urine protein metabolites and U _sg (r = 0.92; P < 0.0001). In summary, U _sg specificity to detect hypohydration was reduced in athletes with large muscle mass. Our data suggest that athletes with large muscle mass (i.e., rugby players) are prone to be incorrectly classified as hypohydrated based on U _sg.     

Changes in heart rate recovery after high-intensity training in well-trained cyclists

Heart rate recovery (HRR) after submaximal exercise improves after training. However, it is unknown if this also occurs in already well-trained cyclists. Therefore, 14 well-trained cyclists (VO_2max 60.3 ± 7.2 ml kg⁻¹ min⁻¹; relative peak power output 5.2 ± 0.6 W kg⁻¹) participated in a high-intensity training programme (eight sessions in 4 weeks). Before and after high-intensity training, performance was assessed with a peak power output test including respiratory gas analysis (VO_2max) and a 40-km time trial. HRR was measured after every high-intensity training session and 40-km time trial. After the training period peak power output, expressed as W kg⁻¹, improved by 4.7% (P = 0.000010) and 40-km time trial improved by 2.2% (P = 0.000007), whereas there was no change in VO_2max (P = 0.066571). Both HRR after the high intensity training sessions (7 ± 6 beats; P = 0.001302) and HRR after the 40-km time trials (6 ± 3 beats; P = 0.023101) improved significantly after the training period. Good relationships were found between improvements in HRR_40-km and improvements in peak power output (r = 0.73; P < 0.0001) and 40-km time trial time (r = 0.96; P < 0.0001). In conclusion, HRR is a sensitive marker which tracks changes in training status in already well-trained cyclists and has the potential to have an important role in monitoring and prescribing training.     

Bone and lean mass inter-arm asymmetries in young male tennis players depend on training frequency

Professional tennis players (TP) have marked inter-arm asymmetry in bone mass (BMC) and density (BMD). To determine if this asymmetry is influenced by training frequency and volume, we studied 24 young tennis players (mean age 10.6 years, Tanner 1–2), 17 physically active control boys (CG) and ten male professional tennis players. Young TP were divided into two groups depending on the number of training days per week (TP5: 5 days/week, n = 10; TP2: 2 days/week, n = 14). In young TP, the dominant arm (DA) compared to the non-dominant arm (NDA) had greater lean mass (TP5, 13.3 ± 2.0% and TP2, 8.3 ± 1.3%), BMC (TP5, 22.4 ± 4.1% and TP2, 12.1 ± 2.2%), bone area (TP5, 15.6 ± 3.3% and TP2, 7.9 ± 2.2%) and BMD (TP5, 4.6 ± 1.5% and TP2, 3.8 ± 0.6%). Inter-arm asymmetry in lean mass, BMC and bone area was greater in TP5 than TP2, being related to the number of weekly hours devoted to tennis (r = 0.45–52, P < 0.05). No significant differences in lumbar spine or femoral neck BMC or BMD were observed between TP5, TP2 and CG. In professional TP, the DA had 18, 32, 11 and 15% greater lean mass, BMC, bone area and BMD than the NDA. Thus, TP5 had 69% of the inter-arm asymmetry in BMC observed in professional TP and a similar inter-arm asymmetry in bone area, although this comparison may not be generalisable. Young tennis players have increased BMC, bone area and lean mass in dominant arm, which magnitude depends on the number of weekly hours devoted to tennis.     

The effects of 6-week-decoupled bi-pedal cycling on submaximal and high intensity performance in competitive cyclists and triathletes

Aim of this work was to examine the effects of decoupled two-legged cycling on (1) submaximal and maximal oxygen uptake, (2) power output at 4 mmol L⁻¹ blood lactate concentration, (3) mean and peak power output during high intensity cycling (30 s sprint) and (4) isometric and dynamic force production of the knee extensor and flexor muscles. 18 highly trained male competitive male cyclists and triathletes (age 24 ± 3 years; body height 179 ± 11 cm; body mass 78 ± 8 kg; peak oxygen uptake 5,070 ± 680 mL min⁻¹) were equally randomized to exercise on a stationary cycle equipped either with decoupled or with traditional crank system. The intervention involved 1 h training sessions, 5 times per week for 6 weeks at a heart rate corresponding to 70% of VO_2peak. VO₂ at 100, 140, 180, 220 and 260 and power output at 4 mmol L⁻¹ blood lactate were determined during an incremental test. VO_2peak was recorded during a ramp protocol. Mean and peak power output were assessed during a 30 s cycle sprint. The maximal voluntary isometric strength of the quadriceps and biceps femoris muscles was obtained using a training machine equipped with a force sensor. No differences were observed between the groups for changes in any variable (P = 0.15–0.90; effect size = 0.00–0.30). Our results demonstrate that a 6 week (30 sessions) training block using decoupled crank systems does not result in changes in any physiological or performance variables in highly trained competitive cyclists.     

Pre-exposure to hyperoxic air does not enhance power output during subsequent sprint cycling

Previous studies have indicated that aerobic pathways contribute to 13–27% of the energy consumed during short-term (10–20 s) sprinting exercise. Accordingly, the present investigation was designed to test the hypothesis that prior breathing of oxygen-enriched air (F_inO₂ = 60%) would enhance power output and reduce fatigue during subsequent sprint cycling. Ten well-trained male cyclists (mean ± SD age, 25 ± 3 years; height, 186.1 ± 6.9 cm; body mass, 79.1 ± 8.2 kg; maximal oxygen uptake [VO_2max]: 63.2 ± 5.2 ml kg⁻¹ min⁻¹) took 25 breaths of either hyperoxic (HO) or normoxic (NO) air before performing 15 s of cycling at maximal exertion. During this performance, the maximal and mean power outputs were recorded. The concentration of lactate, pH, partial pressure of and saturation by oxygen, [H⁺] and base excess in arterial blood were assessed before and after the sprint. The maximal (1,053 ± 141 for HO vs. 1,052 ± 165 W for NO; P = 0.77) and mean power outputs (873 ± 123 vs. 876 ± 147 W; P = 0.68) did not differ between the two conditions. The partial pressure of oxygen was approximately 2.3-fold higher after inhaling HO in comparison to NO, while lactate concentration, pH, [H⁺] and base excess (best P = 0.32) after sprinting were not influenced by exposure to HO. These findings demonstrate that the peak and mean power outputs of athletes performing short-term intense exercise cannot be improved by pre-exposure to oxygen-enriched air.     

Psychometric evaluation of the simplified Japanese version of the Athens Insomnia Scale: The Fukushima Health Management Survey

We investigated the psychometric properties of the simplified Japanese version of the Athens Insomnia Scale (AIS‐SJ) using baseline data from the Fukushima Health Management Survey. Data from 22 878 men and 27 669 women aged 16 years and older were analysed (M_age = 52.9 ± 18.6). Participants lived in the Fukushima evacuation zone and experienced the Great East Japan Earthquake. The AIS‐SJ was used to assess participants’ insomnia symptoms, and its validity was examined by administering the Kessler 6‐item Psychological Distress Scale (K6) and assessing education, self‐rated health and disaster‐related experiences. A confirmatory factor analysis revealed that the two‐factor model was a better fit than the one‐factor model. The AIS‐SJ and its subscales had acceptable reliability (Cronbach's alpha, 0.81). Test of measurement invariance confirmed strict invariance across groups for the participants’ characteristics of gender and mental illness history, but not for participants’ age. AIS‐SJ scores exhibited a near‐normal distribution (skewness, 0.45; kurtosis, ?0.89). There were significant age differences only among women, and gender differences in AIS‐SJ scores with small effect sizes. The AIS‐SJ scores had weak‐to‐moderate correlations with mental illness history, bereavement, experiencing the tsunami, experiencing the nuclear power plant incident, housing damage and losing one's job (polyserial correlations, 0.36, 0.17, 0.13, 0.18, 0.13, and 0.15, respectively), and strong correlations with self‐rated health (polyserial correlation, 0.51), psychological distress (r_s, 0.60) and post‐traumatic stress disorder (r_s, 0.60). The AIS‐SJ is a useful instrument for assessing community dwellers’ insomnia symptoms.     

Accuracy of neuro-fuzzy logic and regression calculations in determining maximal lactate steady-state power output from incremental tests in humans

The aim of this study was to employ neuro-fuzzy logic and regression calculations to determine the accuracy of prediction of the power output (P) of the maximal lactate steady-state (MLSS) on a cycle ergometer calculated from the results of incremental tests. A group of 17 male and 17 female sports students underwent two incremental tests (a 1 min test T₁: initial exercise intensity 0.2 W·kg^–1 increasing 0.2 W·kg^–1 every minute; a 3 min test T₃: initial exercise intensity 0.6 W·kg^–1 increasing 0.6 W·kg^–1 every 3 min) and at least four constant-intensity tests of 30 min duration. Two models for MLSS calculation were developed using the data from T₁ and T₃, a forward stepwise linear regression model (REG) and a neuro-fuzzy model (FUZ). A group of 26 randomly selected subjects (model group, MG) were used to generate the REG and the FUZ models. The data from the remaining 8 subjects (4 men and 4 women; verifying group, VG) were used to verify the REG and FUZ models. The precision of the MLSS calculation in MG produced a better correlation when using data from T₁ (REG r=0.95, FUZ r=0.99) than data from T₃ (REG r=0.88, FUZ r=0.98). Our calculation models were confirmed using data from VG for T₁ (REG r=0.97, FUZ r=0.98) as well as for T₃ (REG r=0.97, FUZ r=0.97). Based on our subject population of young, healthy sport students, our results suggest that a single incremental test may be used for prediction of P at the MLSS using a cycle ergometer. Furthermore, the results from T₁ yielded higher correlations compared to T₃. Calculations from REG were similar to FUZ but the precision of REG and FUZ was better compared to calculations derived using data from a single threshold. Electronic Publication     

The effect of HMB supplementation on body composition, fitness, hormonal and inflammatory mediators in elite adolescent volleyball players: a prospective randomized, double-blind, placebo-controlled study

The use of ergogenic nutritional supplements is becoming inseparable from competitive sports. β-Hydroxy-β-Methylbutyric acid (HMB) has recently been suggested to promote fat-free mass (FFM) and strength gains during resistance training in adults. In this prospective randomized, double-blind, placebo-controlled study, we studied the effect of HMB (3 g/day) supplementation on body composition, muscle strength, anaerobic and aerobic capacity, anabolic/catabolic hormones and inflammatory mediators in elite, national team level adolescent volleyball players (13.5–18 years, 14 males, 14 females, Tanner stage 4–5) during the first 7 weeks of the training season. HMB led to a significant greater increase in FFM by skinfold thickness (56.4 ± 10.2 to 56.3 ± 8.6 vs. 59.3 ±  11.3 to 61.6 ± 11.3 kg in the control and HMB group, respectively, p < 0.001). HMB led to a significant greater increase in both dominant and non-dominant knee flexion isokinetic force/FFM, measured at fast (180°/sec) and slow (60°/sec) angle speeds, but had no significant effect on knee extension and elbow flexion and extension. HMB led to a significant greater increase in peak and mean anaerobic power determined by the Wingate anaerobic test (peak power: 15.5 ± 1.6 to 16.2 ± 1.2 vs. 15.4 ± 1.6 to 17.2 ± 1.2 watts/FFM, mean power: 10.6 ± 0.9 to 10.8 ± 1.1 vs. 10.7 ± 0.8 to 11.8 ± 1.0 watts/FFM in control and HMB group, respectively, p < 0.01), with no effect on fatigue index. HMB had no significant effect on aerobic fitness or on anabolic (growth hormone, IGF-I, testosterone), catabolic (cortisol) and inflammatory mediators (IL-6 and IL-1 receptor antagonist). HMB supplementation was associated with greater increases in muscle mass, muscle strength and anaerobic properties with no effect on aerobic capacity suggesting some advantage for its use in elite adolescent volleyball players during the initial phases of the training season. These effects were not accompanied by hormonal and inflammatory mediator changes.