Altitude training is sometimes employed by elite endurance athletes to improve their sea level performance. This improvement results from the increased red cell mass consequent upon the boost in erythropoietin (EPO) level that occurs as a response to the relatively hypoxic environment at high altitudes. We measured serum EPO levels together with various red cell and reticulocyte parameters including immature reticulocyte fraction (IRF) in eight national track-endurance cyclists, resident at sea-level, prior to and upon return from an altitude of approximately 1905 m. Reticulocytes and soluble transferrin receptor (sTfR) were significantly increased with reduction in ferritin levels immediately on return from high altitude indicating increased erythropoietic activity. IRF in particular showed a significant peak immediately on return but decline to sub-baseline levels by day 9, and recovery to baseline by day 16. Our results indicate that IRF is a sensitive marker of erythropoietic status in athletes undergoing altitude training and subsequent loss of EPO stimuli on return to sea level.
This study examined the thermoregulatory and circulatory responses, and exercise performance of trained distance runners during exercise in the heat (31°C) at varying relative humidity (RH). In a randomized order, 11 trained male distance runners performed 5 60 min steady-state runs at a speed eliciting 70% of VO2max in RH of 23, 43, 52, 61 and 71%. This was followed immediately with an incremental exercise test to volitional exhaustion. Core (Tre) and mean skin temperature (T¯sk), cardiac output (Q), heart rate (HR), and stroke volume (SV) were recorded at regular intervals. A significant (P = 0.003) main effect was detected for RH on mean body temperature (Tb), with a significantly higher Tb detected during steady-state exercise in the 61 and 71% RH compared to that in the 23% RH. During the steady-state exercise, no differences were detected in whole body sweat loss (P = 0.183). However, a significant main effect of RH was observed for HR and SV (P = 0.001 and 0.006, respectively) but not Q (P = 0.156). The time to exhaustion of the incremental exercise test was significantly reduced at 61 and 71% RH compared with 23% RH (P = 0.045 and 0.005, respectively). Despite an increase in dry heat loss, a greater thermoregulatory and circulatory stress was evident during steady-state exercise at 61 and 71% RH. This ultimately limits the capacity to perform the subsequent incremental exercise to exhaustion. This study highlighted that in a warm environment, the range of the prescriptive zone progressively narrows as RH increases.
To identify the effect of additional elastic force on the kinetic and kinematic characteristics, as well as the magnitude of leg stiffness, during the performance of accentuated countermovement jumps (CMJs).
The understanding that fluid ingestion attenuates thermoregulatory and circulatory stress during exercise in the heat was based on studies conducted in relatively dry (∼50% RH) environments. It remains undetermined whether similar effects occur during exercise in a warm and more humid environment, where evaporative capacity is reduced. Nine well-trained, unacclimatised male runners were randomly assigned to perform four experimental trials where they ran for 60 min at an intensity of 70% VO2max followed by an incremental exercise test until volitional exhaustion. The four trials consisted of non-fluid ingestion (NF) and fluid ingestion (FI) in a warm-dry (WD) and warm-humid condition (WH). Time to exhaustion (TTE), body temperature (Tb), whole body sweat rate, partitional calorimetry measures, heart rate and plasma volume were recorded during exercise. There was no significant difference in Tb following 60 min of exercise in FI and NF trial within both WD (37.3°C ± 0.4 vs. 37.4°C ± 0.3; p > 0.05) and WH conditions (38.0°C ± 0.4 vs. 38.1°C ± 0.4; p > 0.05). The TTE was similar between FI and NF trials in both WH and WD, whereas exercise capacity was significantly shorter in WH than WD (9.1 ± 2.8 min vs. 12.7 ± 2.4 min, respectively; p = 0.01). Fluid ingestion failed to provide any ergogenic benefit in attenuating thermoregulatory and circulatory stress during exercise in the WH and WD conditions. Consequently, exercise performance was not enhanced with fluid ingestion in the warm-humid condition, although the humid environment detrimentally affected exercise endurance.
The aims of this study were to establish the physical and physiological attributes of elite and sub-elite Malaysian male badminton players and to determine whether these attributes discriminate elite players from sub-elite players. Measurements and tests of basic anthropometry, explosive power, anaerobic recovery capacity, badminton-specific movement agility, maximum strength, and aerobic capacity were conducted on two occasions, separated by at least one day. The elite (n = 12) and sub-elite (n = 12) players' characteristics were, respectively: mean age 24.6 years (s = 3.7) and 20.5 years (s = 0.7); mass 73.2 kg (s = 7.6) and 62.7 kg (s = 4.2); stature 1.76 m (s = 0.07) and 1.71 m (s = 0.05); body fat 12.5% (s = 4.8) and 9.5% (s = 3.4); estimated VO(2max) 56.9 ml . kg(-1) . min(-1) (s = 3.7) and 59.5 ml . kg(-1) . min(-1) (s = 5.2). The elite players had greater maximum absolute strength in one-repetition maximum bench press (P = 0.015) compared with the sub-elite players. There were significant differences in instantaneous lower body power estimated from vertical jump height between the elite and sub-elite groups (P < 0.01). However, there was no significant difference between groups in shuttle run tests and on-court badminton-specific movement agility tests. Our results show that elite Malaysian male badminton players are taller, heavier, and stronger than their sub-elite counterparts. The test battery, however, did not allow us to discriminate between the elite and sub-elite players, suggesting that at the elite level tactical knowledge, technical skills, and psychological readiness could be of greater importance.