Strenuous Training Research Articles

Knochendichte, endokrine Parameter und Essverhalten bei Läuferinnen

The prominence and number of female athletes has grown dramatically during this century. This increased participation in physical activity has led to significant health benefits and improved physical fitness. Regular weight-bearing exercise has a beneficial effect on the bone mineral density (BMD). But strenuous training can affect the female reproductive system and become a major problem concerning female athlete's health. Furthermore, female runners driven to excel in her sport and pressured to have a thin physique may attempt to lose bodyweight or body fat and can develop patterns of eating disorder. These patterns may lead to menstrual dysfunction and subsequent osteoporosis. Many female athletes are at risk of developing one or more of a group of three medical disorders, described by the American College of Sports Medicine in 1992 as the Female Athlete Triad. The Female Athlete Triad can be prevented. Medical management requires an early diagnosis for the improvement of the treatment efficiency.

The Menstrual Cycle and Human Performance: An Overview

Physiological events during the normal menstrual cycle are determined by feedback loops within the hypothalamic-pituitary-ovarian axis. Hormonal changes within the menstrual cycle have potential impact on human performance. Relevant stages to consider are pre-menses and menses, the follicular and luteal phases separated by an abrupt elevation in lutenizing hormone and characterised by a sharp rise in body temperature coinciding with ovulation. Strenuous athletic training may affect the normal menstrual cycle. Such disruptions include delayed menarche in ballet dancers and gymnasts, shortened luteal phase and secondary amenorrhea associated with high training loads and competitive stress. Amenorrhea is also noted in flight attendants, linked with an inhibiting effect of disrupted circadian rhythm on lutenizing hormone. The so-called 'athlete triad' considers secondary amenorrhea, abnormal eating behaviour and osteoporosis (attributed to chronic hypoestrogenia). The normal cycle may also be disrupted when circadian rhythms are disturbed, for example in rapid time-zone transitions. Fluctuations in the steroid hormones have been associated with changes in muscle strength. There is evidence also of elevations in heart rate: changes may be partly specific to time of day. Effects on muscle strength may be determined at selected stages of the menstrual cycle, using whole-body performance, local muscle groups or isolated individual muscles. Whilst oestrogen has been implicated in the ergogenic effect of steroid hormones, there is accumulating evidence that a role for progesterone cannot be discounted. The isolation of the ovarian hormones separately is feasible with studies of IVF patients or groups on hormone replacement therapy.

Exercise affects the mechanical properties and histological appearance of equine articular cartilage.

Dorsal carpal osteochondral injury is a major cause of reduced performance in horses undergoing high-intensity training. It was hypothesised that the mechanical behaviour and histology of cartilage are influenced by the intensity of exercise and by location within a joint. Relationships between histology and mechanical behaviour were identified in 2-year-old horses undergoing 19 weeks of high-intensity treadmill training or low-intensity exercise and then compared between groups. Dorsal and palmar test sites were identified on radial, intermediate, and third carpal articular surfaces after euthanasia. The mechanical properties of cartilage were determined with an automated creep indentation apparatus as previously described for equine cartilage. Cartilage morphology was assessed with use of sections stained with haematoxylin and eosin and toluidine blue. Dorsal cartilage was less permeable, thinner, and had a loss of chondrocyte alignment compared with palmar cartilage. Cartilage from strenuously trained horses showed more fibrillation and chondrocyte clusters than did cartilage from gently exercised animals. Dorsal radial carpal cartilage and third carpal cartilage of strenuously trained animals were significantly less stiff than that from gently exercised animals, and the former had reduced superficial toluidine blue staining compared with that from the gently exercised group. These results indicate that topographical and exercise-related differences exist in the morphology and mechanical properties of carpal cartilage and suggest that strenuous training may lead to deterioration of cartilage at sites with a high clinical incidence of lesions.

Effects of potassium bicarbonate supplementation on axial and peripheral bone mass in rats on strenuous treadmill training exercise.

We administered a potassium bicarbonate supplement to rats on strenuous treadmill training in order to determine the effect on bone mass and the metabolic acidosis seen with this type of training. A sample of 45 93-day-old female Wistar rats with a mean initial weight of 267 +/- 17 g were studied. The control group (15 rats) was not exercised or given potassium bicarbonate (Ex- PB-). The experimental group (30 rats) was randomly divided into two subgroups of 15 rats each, one that exercised and did not receive potassium bicarbonate (Ex+ PB-) and one that exercised and received potassium bicarbonate (Ex+ PB+), at a dose of 0.05 mg/kg/day administered by esophageal catheter on exercise days. Training consisted of treadmill running on 5 out of 7 days for a period of 11 weeks. Running time, treadmill speed, and the percent grade were gradually increased until week 7, then maintained until rats were sacrificed at the ened of 11 weeks. The bone mineral content (BMC) and bone mineral density (BMD) of the whole right femur and 5th lumbar vertebra were measured. Femoral and vertebral length were also measured. Femur length, weight, BMC, and BMD, and femur BMC/final weight ratio, and vertebral weight, BMD, and BMC, and vertebral BMC/final weight ratio were lower in the Ex+ PB- group than in either the controls or the Ex+ PB+ group (P < 0.01-P < 0.0001); the length of the 5th lumbar vertebra did not differ between groups.

Effects of summer camp endurance training on non-specific immunity in long-distance runners.

The present study was conducted to investigate the effects of endurance training during a 1-month summer camp on the non-specific host defence systems of ten highly trained male long-distance runners. Examinations with informed consent were carried out three times: 2 days before the training began, an intermediate day, and 2 days after the camp. The subjects ran a total of about 800 km during the camp. Neutrophilic reactive oxygen species (ROS) generation determined by luminol- and lucigenin-dependent chemiluminescence and cytochrome c reduction methods was assayed at two time points because the camp was held far from our laboratory: neutrophils isolated 6 hours after blood sampling were examined at all three time points and neutrophils isolated immediately after blood sampling were examined before and after the camp. The ROS production indicated by peak height of luminol-dependent chemiluminescence and peak velocity of cytochrome c reduction from neutrophils isolated 6 hours after blood sampling was suppressed after the camp (P < 0.05 for both), but, the ROS production from neutrophils isolated immediately after blood sampling and the serum opsonic activity appeared not to be affected. Neutrophils diminished their activity during the 6-hour waiting time after the camp. These results suggest that the non-specific host defence system is not directly impaired by long, strenuous endurance training.

Evaluating physiological strain during cold exposure using a new cold strain index.

A cold strain index (CSI) based on core (T(core)) and mean skin temperatures (T(sk)) and capable of indicating cold strain in real time and analyzing existing databases has been developed. This index rates cold strain on a universal scale of 0-10 and is as follows: CSI = 6.67(T(core t) - T(core 0)). (35 - T(core 0))(-1) + 3.33(T(sk (t)) - T(sk 0)). (20 - T(sk 0))(-1), where T(core 0) and T(sk 0) are initial measurements and T(core t) and T(sk t) are simultaneous measurements taken at any time t; when T(core t) > T(core 0), then T(core t) - T(core 0) = 0. CSI was applied to three databases. The first database was obtained from nine men exposed to cold air (7 degrees C, 40% relative humidity) for 120 min during euhydration and two hypohydration conditions achieved by exercise-heat stress-induced sweating or by ingestion of furosemide 12 h before cold exposure. The second database was from eight men exposed to cold air (10 degrees C) immediately on completion of 61 days of strenuous outdoor military training, 48 h later, and after 109 days. The third database was from eight men repeatedly immersed in 20 degrees C water three times in 1 day and during control immersions. CSI significantly differentiated (P < 0.01) between the trials and individually categorized the strain of the subject for two of these three databases. This index has the potential to be widely accepted and used universally.

Exertional fatigue, sleep loss, and negative energy balance increase susceptibility to hypothermia.

The purpose of this study was to determine how chronic exertional fatigue and sleep deprivation coupled with negative energy balance affect thermoregulation during cold exposure. Eight men wearing only shorts and socks sat quietly during 4-h cold air exposure (10 degreesC) immediately after (<2 h, A) they completed 61 days of strenuous military training (energy expenditure approximately 4,150 kcal/day, energy intake approximately 3,300 kcal/day, sleep approximately 4 h/day) and again after short (48 h, SR) and long (109 days, LR) recovery. Body weight decreased 7.4 kg from before training to A, then increased 6.4 kg by SR, with an additional 6.4 kg increase by LR. Body fat averaged 12% during A and SR and increased to 21% during LR. Rectal temperature (Tre) was lower before and during cold air exposure for A than for SR and LR. Tre declined during cold exposure in A and SR but not LR. Mean weighted skin temperature (Tsk) during cold exposure was higher in A and SR than in LR. Metabolic rate increased during all cold exposures, but it was lower during A and LR than SR. The mean body temperature (0.67 Tre + 0.33 Tsk) threshold for increasing metabolism was lower during A than SR and LR. Thus chronic exertional fatigue and sleep loss, combined with underfeeding, reduced tissue insulation and blunted metabolic heat production, which compromised maintenance of body temperature. A short period of rest, sleep, and refeeding restored the thermogenic response to cold, but thermal balance in the cold remained compromised until after several weeks of recovery when tissue insulation had been restored.

Skeletal muscle and liver lipoyllysine content in response to exercise, training and dietary alpha-lipoic acid supplementation.

In human cells, alpha-lipoic acid (LA) is present in a bound lipoyllysine form in mitochondrial proteins that play a central role in oxidative metabolism. The possible effects of oral LA supplementation, a single bout of strenuous exercise and endurance exercise training on the lipoyllysine content in skeletal muscle and liver tissues of rat were examined. Incorporation of lipoyl moiety to tissue protein was not increased by enhanced abundance of LA in the diet. Endurance exercise training markedly increased lipoyllysine content in the liver at rest. A bout of exhaustive exercise also increased hepatic lipoyllysine content. A significant interaction of exhaustive exercise and training to increase tissue lipoyllysine content was evident. In vastus lateralis skeletal muscle, training did not influence tissue lipoyllysine content. A single bout of exhaustive exercise, however, clearly increased the level of lipoyllysine in the muscle. Comparison of tissue lipoyllysine data with that of free or loosely-bound LA results showed a clear lack of association between the two apparently related parameters. Tightly protein-bound lipoyllysine pool in tissues appeared to be independent of the loosely-bound or free LA status in the tissue.

Intravenous glucose tolerance test—derived glucose effectiveness in strength-trained humans

The effect of long-term strenuous resistance training on glucose effectiveness (SG) was examined by comparing 11 strength-trained and 20 sedentary males by a minimal model approach. Lean body mass (LBM) was measured by hydrostatic weighing. The LBM in strength-trained subjects (65.7 ± 3.1 kg) was significantly larger than in sedentary subjects (56.6 ± 1.2 kg, P < .01). The glucose disappearance constant ([KG] 3.07% ± 0.45% · min −1) and insulin sensitivity ([SI] 17.5 ± 2.0 × 10 −5 · min −1 · pmol/L −1) in strength-trained subjects were significantly higher than in sedentary subjects (2.06% ± 0.14% · min −1 and 10.3 ± 1.2 × 10 −5 · min −1 · pmol/L −1, P < .05). SG in strength-trained subjects (0.024 ± 0.003 min −1) was significantly higher than in sedentary subjects (0.018 ± 0.001 min −1, P < .05). These results thus suggest that the improved glucose tolerance in strength-trained subjects was due to increased SG and SI.

Plasma Insulin-Like Growth Factor-I and High Affinity Growth Hormone-Binding Protein Levels Increase After Two Weeks of Strenuous Physical Training

The high affinity growth hormone-binding protein (GHBP) circulates in human blood and represents the extracellular domain of the growth hormone (GH) receptor. It is well known that repetitive bouts of endurance type exercise result in increased integrated GH secretion. As the effects of chronic exercise on plasma GHBP levels have never been studied systematically, we investigated the effect of 2 weeks of intense endurance training on plasma GHBP as well as on plasma insulin-like growth factor (IGF)-I levels in 10 healthy, young, non-obese men. IGF-I was measured as an indicator of the effects of GH release. We also studied 10 control subjects matched for sex, age and activity, who were instructed not to change their customary activities. GHBP was determined by FPLC size exclusion chromatography and subsequent Scatchard plot analysis of the binding data; IGF-I levels were measured by RIA. The results showed that plasma IGF-I and GHBP levels were increased in the subjects who followed the training program. IGF-I and GHBP changed from 252 +/- 56 ng/ml and 912 +/- 59 pmol/l before training, to 344 +/- 61 ng/ml (p < 0.01) and 1020 +/- 48 pmol/l (p < 0.01), respectively. Another effect of the training was that the aerobic capacity of these subjects was better utilized and endurance was improved. In contrast, plasma IGF-I, GHBP, utilization of aerobic capacity and endurance did not change significantly in the control subjects. We conclude that two weeks of strenuous endurance training lead to increased plasma IGF-I and high affinity GHBP levels.

The role of the knee brace in the prevention of anterior knee pain syndrome.

Our prospective study evaluates the use of a knee brace with a silicon patellar support ring as a method of preventing anterior knee pain from developing in young persons undergoing strenuous physical exercise. We studied 60 young athletes, who qualified for a strenuous physical training course and who had not suffered from anterior knee pain previously. Twenty-seven subjects were in the brace group and 33 were in the nonbrace control group. The incidence of anterior knee pain syndrome increased with the intensity of exertion as the study progressed; i.e., subjects ran 6 km in the 1st week, gradually increasing each week up to 42 km/week at the 8th week. Yet, there was a significant reduction in the incidence of the syndrome at the end of the study in male athletes who had applied the braces before exercise sessions and in the brace group as a whole, compared with the control group. Prophylactic use of the brace, as described, did not reduce the ability of the athletes who wore braces to improve their physical fitness parameters in response to exercise. These data indicate that the use of a brace may be an effective way to prevent the development of anterior knee pain syndromes in persons participating in strenuous and intensive physical exercise.

Exertional rhabdomyolysis as a result of strenuous military training

We reviewed biochemical data from 19 soldiers who marched intermittently over 4 weeks, carrying about 45 kg of kit, with a limited intake of food and water. The mean serum creatine kinase activity was higher after the march ( p < 0.01), although the subjects did not develop symptomatic rhabdomyolysis. The mean serum potassium level ( p < 0.005) and the mean serum sodium level ( p < 0.05) were lower after the march. The level of serum osmolality showed no significant changes. Subclinical rhabdomyolysis was not rare among the soldiers. We also report a case of the soldier with exertional clinical rhabdomyolysis.

Bone mass at lumbar spine and tibia in young males—impact of physical fitness, exercise, and anthropometric parameters: A prospective study in a cohort of military recruits

Bone mineral density (BMD) and bone mineral content (BMC) were measured using DXA at lumbar spine and tibial diaphyses at the beginning and at the end of a 15-week training period in 151 military recruits of the Swiss army belonging to 5 different troop categories (infantry grenadiers, tank drivers, tank gunners, signalmen, and privates) who each were exposed to physical training of various intensity. At baseline, height, body mass index, and degree of physical fitness independently correlated with vertebral and tibial BMD. Over the 15 weeks of physical training BMD at tibial diaphyses increased by 2.2 +/- 0.3% at the left leg (p = 0.0001) and by 1.1% at the right leg (p = 0.002) with differences between troop categories. At lumbar spine, BMD decreased significantly in tank drivers (-1.2 +/- 0.4%, p = 0.001) and particularly in infantry grenadiers (-2.1 +/- 0.4%) who had the most strenuous weight-bearing training, but not in other troop categories. This decrease was twice as large at the center of the vertebra than for the whole vertebra. These BMD changes were associated with increments in serum levels of osteocalcin and alkaline phosphatase activity. From the initial cohort, 48 subjects volunteered for a third investigation carried out 2 years after the end of the military training period. At this time, lumbar BMD and BMC had risen back to baseline, whereas at tibial diaphyses bone width and BMC but not BMD increased by 5.8 +/- 1.1% and 6.2 +/- 0.9%, respectively, vs. baseline (p = 0.0001 for both).(ABSTRACT TRUNCATED AT 250 WORDS)

Lipoprotein profile changes during intense training of Israeli military recruits

The effect of prolonged strenuous military training on serum lipoproteins was studied in 73 new recruits. Dietary intake, body weight, and average energy expenditure were recorded, and blood samples collected at three time periods before training began (time 0), and after 6 and 12 wk of intense physical activity (times I and II, respectively). There was a significant increase in high density lipoprotein (HDL) cholesterol and a decrease in low density lipoprotein (LDL) cholesterol accompanying an increase of duration and intensity of exercise. HDL increased from 40.5 +/- 7.7 mg.dl-1 at time 0 to 44.5 +/- 9.4 mg.dl-1 at time I and to 52.8 +/- 8.7 mg.dl-1 at time II, and each mean P-value for increases in HDL from time 0-I, I-II, and 0-II were P < 0.0001). For LDL cholesterol, the mean decreases were -1.1, -6.1, and -7.3 mg.dl-1, respectively (P = 0.003 from I-II, and 0.01 from 0-II). These changes did not correlate with weight loss, reduced energy, or fat intake. We conclude that intense physical activity is associated with beneficial changes in the lipoprotein profile in new military recruits during a training period extending over 12 wk.

Effects of an intensive 12-wk training program by elite swimmers on neutrophil oxidative activity

The effects of an intensive 12-wk training program by 12 national-level swimmers on neutrophil oxidative activity were studied. Eleven sedentary (untrained) subjects (6 males and 5 females) served as environmental controls. Blood samples (10 ml) were taken at rest from an antecubital vein and neutrophils isolated by standard separation techniques. The oxidative burst activity of isolated neutrophils was assessed with an in vitro flow cytometric assay that used the fluorescent probe dihydrorhodamine 123. Two-way ANOVA (repeated measures) showed that oxidative activity was lower (P < 0.05) in the elite swimmers compared with the sedentary control group across the 12-wk period. Analysis of cells from swimmers in training was made: repeated measures ANOVA provided evidence of a significant decline (P < 0.05) in the number of cells responding positively ito in vitro challenge. Despite this decline, there was no significant difference in self-reported upper respiratory tract infection rate between the swimmers and sedentary individuals. These data show that: (i) elite swimmers undertaking intensive training have a significantly lower neutrophil oxidative activity at rest than do age- and sex-matched sedentary individuals; (ii) aspects of oxidative activity in swimmers are further suppressed during periods of strenuous training, and (iii) the extent of the suppression does not appear to be of clinical significance.

Effect of endurance training on hepatic glycogenolysis and gluconeogenesis during prolonged exercise in men.

In humans, endurance training markedly reduces the rate of hepatic glucose production during exercise. To determine whether this is due to a reduction in glycogenolysis, in gluconeogenesis, or in both processes, six men were studied at rest and during 2 h of cycle ergometer exercise at 60% pretraining peak O2 consumption (VO2peak), both before and after completion of a strenuous endurance training program (cycling at 75-100% VO2peak for 45-90 min/day, 6 days/wk for 12 wk). The overall rate of glucose appearance (Ra) was determined using a primed continuous infusion of [6,6-2H]glucose, whereas the rate of gluconeogenesis (Rgng) was estimated from the incorporation of 13C into glucose (via pyruvate carboxylase) from simultaneously infused [13C]bicarbonate. Training did not affect glucose kinetics at rest but reduced the average Ra during exercise by 42% [from 36.8 +/- 3.8 to 21.5 +/- 3.6 (SE) mumol.min-1.kg-1; P < 0.001]. This decrease appeared to be mostly due to a reduction in hepatic glycogenolysis. However, the estimated Rgng during exercise also decreased significantly (P < 0.001) with training, falling from 7.5 +/- 1.6 mumol.min-1.kg-1 (23 +/- 3% of total Ra) before training to 3.1 +/- 0.6 mumol.min-1.kg-1 (14 +/- 3% of total Ra) after training. These training-induced adaptations in hepatic glucose metabolism were associated with an attenuated hormonal response to exercise (i.e., higher insulin and lower glucagon, norepinephrine, and epinephrine concentrations) as well as a reduced availability of gluconeogenic precursors (i.e., lower lactate and glycerol concentrations). We conclude that endurance training reduces both hepatic glycogenolysis and gluconeogenesis during prolonged exercise in men.

Changes in the susceptibility of red blood cells to oxidative and osmotic stress following submaximal exercise

Red blood cell (RBC) susceptibility to oxidative and osmotic stress in vitro was investigated in cells from trained and untrained men before and after submaximal exercise. Whilst no significant change in peroxidative haemolysis occurred immediately after 1 h of cycling at 60% of maximal aerobic capacity (VO2max), a 20% increase was found 6h later in both groups (P < 0.05). The RBC osmotic fragility decreased by 15% immediately after exercise (P < 0.001) and this was maintained for 6h (P < 0.001). There was an associated decrease in mean cell volume (P < 0.05). Training decreased RBC susceptibility to peroxidative haemolysis (P < 0.025) but it did not influence any other parameter. These exercise-induced changes were smaller in magnitude but qualitatively similar to those found in haemopathological states involving haem-iron incorporation into membrane lipids and the short-circuiting of antioxidant protection. To explore this similarity, a more strenuous and mechanically stressful exercise test was used. Running at 75% VO2max for 45 min reduced the induction time of O2 uptake (peroxidation), consistent with reduced antioxidation capacity, and increased the maximal rate of O2 uptake in RBC challenged with cumene hydroperoxide (P < 0.001). The proportion of high-density RBC increased by 10% immediately after running (P < 0.001) but no change in membrane-incorporated haem-iron occurred. In contrast, treatment of RBC with oxidants (20-50 mumol.l-1) in vitro increased cell density and membrane incorporation of haem-iron substantially. These results showed that single episodes of submaximal exercise caused significant changes in RBC susceptibility to oxidative and osmotic stress. Such responses may account for the increase in RBC turnover found in athletes undertaking strenuous endurance training.

Health aspects of horse production including training with special reference to Nordic conditions

Standardbred and coldblooded trotters start racing at the young age of 3 years. In order to sustain strenuous training beginning at 18 months of age, optimal nutrition and access to free exercise during the rearing period are needed to cope with the physiological demands during training. Training on a hard ground with spikes under the horse-shoes may be deleterious to the horse's hooves and joints. In the Nordic countries, alternative methods of training the young horse can be used in order to prepare the horse for later more strenous speed training. Lungeing horses in deep sand or rubber-shavings gives good development of the cardiovascular system as well as of the skeletal muscles of the young horse. Endurance training on frozen lakes is also a good alternative to training on the track or roads. For 3-year old or older horses training with a braked cart is practiced as a popular method for strength training. No adverse effects have been reported when training or racing is performed at low temperatures, even as low as −25°Celsius.

Exercise training does not alter cytochrome P-450 content and microsomal metabolism

The purpose of this investigation was to determine whether increased endurance exercise capacity alters total hepatic cytochrome P-450 content and cytochrome P-450 (CYP1A and CYP2B) mediated hepatic microsomal mixed-function oxidase drug metabolism. Twenty adult male Sprague-Dawley rats were randomly assigned to either a control (C) or an endurance trained group (ET). ET rats were progressively trained 5 d.wk-1 for 11 wk. Both C and ET rats were administered in random order single posttraining doses of probe drugs theophylline (probe for CYP1A) and antipyrine (probe for CYP2B). Soleus muscle citrate synthase activity of ET rats was significantly greater (P < 0.01) than for C rats (mean +/- SD; C, 26.4 +/- 1.3 mumol.g-1.min-1; ET, 46.1 +/- 2.7). In contrast, total liver cytochrome P-450 content was not significantly different (P > 0.01) among C and ET rats (mean +/- SD; C, 0.554 +/- 0.055 nmol.mg-1 liver protein; ET, 0.604 +/- 0.080). Likewise, the posttraining C and ET single-sample plasma clearances of theophylline (mean +/- SD; C, 1.89 +/- 0.360 1.h-1.kg-1 total liver weight; ET, 2.08 +/- 0.49) and antipyrine (mean +/- SD; C, 6.44 +/- 1.56 1.h-1.kg-1 total liver weight; ET, 6.51 +/- 1.02) were not significantly different (P > 0.01). Therefore, it was concluded that strenuous endurance training of 11 wk duration did not alter total hepatic cytochrome P-450 content or CYP1A or CYP2B activity.

Longitudinal Exercise-Heat Tolerance and Running Economy of Collegiate Distance Runners

To evaluate the effects of strenuous physical training on the exercise-heat tolerance (EHT) and running economy (RE) of endurance athletes, 5 male collegiate distance runners performed three strenuous 20-min exercise trials in a hot environment during the winter (Tl) indoor track and field season and during the latter stages (T2 and T3) of the outdoor track and field season. EHT was highest at Tl and did not change during 17.5 wks of training and competition. Similarly, RE was not significantly enhanced from Tl to T3. RE was strongly correlated with the change in rectal temperature pre- to postexercise, suggesting that RE may be an important factor in the development of hyperthermia during exercise in the heat. The runners did not significantly improve their EHT and RE during training and competition. However, the magnitudes of change in mean RE and in sweat rate suggest that these training related adaptations may have been physiologically though not statistically significant.