Hyponatremia in ultradistance triathletes.

PURPOSE: Hyponatremia ([plasma sodium] <135 mmol x L(-1)) is a potentially serious complication of ultraendurance sports. However, the etiology of this condition is still uncertain. This observational cohort study aimed to determine prospectively the incidence and etiology of hyponatremia in an ultradistance triathlon. METHODS: The subjects consisted of 605 of the 660 athletes entered in the New Zealand Ironman triathlon (3.8-km swim, 180-km cycle, and 42.2-km run). Subjects were weighed before and after the race. A blood sample was drawn for measurement of plasma sodium concentration after the race. RESULTS: Complete data on pre- and postrace weights and plasma sodium concentrations were available in 330 race finishers. Postrace plasma sodium concentrations were inversely related to changes in body weight (P = 0.0001). Women (N = 38) had significantly lower plasma sodium concentrations (133.7 vs 137.4 mmol x L(-1); P = 0.0001) than men (N = 292) and lost significantly less relative weight (-2.7 vs -4.3%; P = 0.0002). Fifty-eight of 330 race finishers (18%) were hyponatremic; of these only 18 (31%) sought medical care for the symptoms of hyponatremia (symptomatic). Eleven of the 58 hyponatremic athletes had severe hyponatremia ([plasma sodium] < 130 mmol x L(-1)); seven of these 11 severely hyponatremic athletes were symptomatic. The relative body weight change of the 11 severely hyponatremic athletes ranged from 2.4% to +5%; eight (73%) of these athletes either maintained or gained weight during the race. In contrast, relative body weight changes in the 47 athletes with mild hyponatremia ([plasma sodium] 130-134 mmol x L(1)) were more variable, ranging from -9.25% to +2.2%. CONCLUSIONS: Hyponatremia is a common biochemical finding in ultradistance triathletes but is usually asymptomatic. Although mild hyponatremia was associated with variable body weight changes, fluid overload was the cause of most (73%) cases of severe, symptomatic hyponatremia.     

Prevalence of exercise-induced arterial hypoxemia in healthy women

PURPOSE: Exercise-induced arterial hypoxemia (EIAH) is reported to occur in approximately 50% of highly trained male endurance athletes. Few studies have examined EIAH in women and the prevalence remains unclear. It has been reported that some female subjects who develop EIAH possess maximal oxygen consumption (VO2max) values that are within 15% of their predicted value. This is unique to women, where EIAH has generally been reported in men who have a high VO2max. The primary objective of this investigation was to determine the prevalence of EIAH in a large female population with a wide range of VO2max values. It was hypothesized that EIAH would occur with a greater prevalence and at relatively lower predicted VO2max than that previously reported in males. METHODS: Young women (N = 52; 26.5 +/- 4.9 yr) performed a cycle test to exhaustion to determine VO2max, and oxyhemoglobin saturation (SaO2) was monitored via pulse oximetry. All subjects were tested during the early follicular phase of their menstrual cycle. A >/= 4% drop in SaO2 represented EIAH. RESULTS: Values for VO2max were variable (VO2max range: 28.0-61.3 mL x kg(-1) x min(-1)). EIAH was present in 67% of the women with N = 19 displaying mild EIAH (92-94%SaO2) and N = 16 displaying moderate EIAH (87-91%SaO2). CONCLUSION: It appears that the prevalence of EIAH in women is slightly greater than the 50% prevalence value that is typically reported for highly fit men.     

The effects of physical exercise on the concentrations of ferritin and transferrin receptor in plasma of male judoists

The aim of the study was to assess the within-subject (day-to-day) variability for iron status variables: ferritin (ferr) and soluble transferrin receptor (sTfR) concentrations in plasma and the sTfR/log ferr index in athletes subjected daily to high physical loads. Blood was sampled in the morning from 8 healthy male elite judoists, aged 20 - 31 years, for 10 consecutive days while at training camp. Mean concentrations of ferritin and sTfR in plasma for the 10 day period were 32.0. 1.771(+/-1) and 2.41. 1.324(+/-1) mg/l, respectively. The average within-subject, day-to-day variability for ferritin was 27.4 % (range: 16 - 44 %), and was much lower for sTfR (6.7 %; range: 4 - 15 %). Ferritin concentrations were significantly, albeit weakly, correlated with training loads on the preceding day (r = 0.256; p < 0.05) and with creatine kinase (CK) activities on the same day (r = 0.397; p < 0.001), while sTfR did not correlate with either training loads or CK activities. Mean day-to-day variability for the sTfR/log ferr index was 11.8 % (range: 5 - 21 %), i.e. markedly lower than for ferritin. Although the physical load-induced changes in iron metabolism indices in male subjects were similarly oriented as in the earlier reported female ones representing the same sport, the magnitude of those changes was less pronounced than in the females. This was evidenced by a markedly lower within-subject day-to-day variability in ferritin, still significant but weak correlation between load magnitude and ferritin levels, and a significant, negative correlation between ferritin and sTfR concentrations, not found previously in the female athletes. However, despite lower variability in ferritin than in women, the exercise-induced ferritin increases in male athletes might make a reliable assessment of iron stores in them difficult. The present results confirm our earlier reports that sTfR levels are stable under high physical loads, thus making them a useful indicator of iron status. Also sTfR/log ferr index is of a much higher diagnostic value than ferritin, despite high variability of the latter. That index is particularly valuable in detecting iron-deficient erythropoiesis.     

Body-mass management of Australian lightweight rowers prior to and during competition

PURPOSE: Although the body-mass management strategies of athletes in high-participation weight-category sports such as wrestling have been thoroughly investigated, little is known about such practices among lightweight rowers. This study examined the body-mass management practices of lightweight rowers before competition and compared these with current guidelines of the International Federation of Rowing Association (FISA). Quantification of nutrient intake in the 1-2 h between weigh-in and racing was also sought. METHODS: Lightweight rowers (N = 100) competing in a national regatta completed a questionnaire that assessed body-mass management practices during the 4 wk before and throughout a regatta plus recovery strategies after weigh-in. Biochemical data were collected immediately after weigh-in to validate questionnaire responses. Responses were categorized according to gender and age category (Senior B or younger than 23 yr old, i.e., U23, Senior A or OPEN, i.e., open age limit) for competition. RESULTS: Most athletes (male U23 76.5%, OPEN 92.3%; female U23 84.0%, OPEN 94.1%) decreased their body mass in the weeks before the regatta at rates compliant with FISA guidelines. Gradual dieting, fluid restriction, and increased training load were the most popular methods of body-mass management. Although the importance of recovery after weigh-in was recognized by athletes, nutrient intake and especially sodium (male U23 5.3 +/- 4.9, OPEN 7.7 +/- 5.9; female U23 5.7 +/- 6.8, OPEN 10.2 +/- 5.4 mg x kg(-1)) and fluid intake (male U23 12.1 +/- 7.1, OPEN 13.5 +/- 8.1; female U23 9.4 +/- 7.4, OPEN 14.8 +/- 6.9 mL x kg(-1)) were below current sports nutrition recommendations. CONCLUSION: Few rowers were natural lightweights; the majority reduced their body mass in the weeks before a regatta. Nutritional recovery strategies implemented by lightweight rowers after weigh-in were not consistent with current guidelines.     

Muscle damage and resting metabolic rate after acute resistance exercise with an eccentric overload

PURPOSE: The purpose of this investigation was to determine whether muscle damage caused from acute resistance exercise with an eccentric overload would influence resting metabolic rate (RMR) up to 72 h postexercise in resistance-trained (RT) and untrained (UT) subjects. METHODS: Nine RT and 9 UT male subjects (mean +/- SD; age = 20.7 +/- 2.1 yr; body mass = 79.0 +/- 1.4 kg; height = 178.4 +/- 3.1 cm; and body fat = 10.2 +/- 1.6%) were measured for RMR, creatine kinase concentration ([CK]), and rating of perceived muscle soreness (RPMS) on five consecutive mornings. To induce muscle damage, after the measurements on day 2, each subject performed leg presses that emphasized the eccentric movement for 8 sets at his six-repetition maximum (6-RM). RESULTS: Compared with baseline, the RMR (kJ x d(-1) and kJ x kg FFM(-1) x h(-1) was significantly elevated for RT and UT at 24 h and 48 h postexercise. From 24 h to 48 h to 72 h postexercise, RMR significantly decreased within both groups. The UT group had a significantly higher RMR at 24 h (9,705.4 +/- 204.5 kJ x d(-1)) and 48 h postexercise (8,930.9 +/- 104.4 kJ x d(-1)) when compared with the RT group (9,209.3 +/- 535.3 and 8,601.7 + 353.7 kJ x d(-1)). Both [CK] and RPMS showed a similar time course. CONCLUSION: There was a significantly higher [CK] for the UT group at 24 h postexercise (320.4 +/- 20.1 U x L(-1)) and for both [CK] and RPMS at 48 h (1,140.3 +/- 37.1 U x L(-1) and 4.4 +/- 0.5, respectively) and 72 h postexercise (675.9 +/- 41.7 U x L(-1) and 1.67 +/- 0.5, respectively) when compared with the RT group (24 h, 201.9 +/- 13.4 U x L(-1); 48 h, 845.4 +/- 30.7 U x L(-1) and 3.7 +/- 0.5: and 72 h postexercise, 420.2 +/- 70.2 U x L(-1) and 0.89 +/- 0.3). These data indicate that eccentrically induced muscle damage causes perturbations in RMR up to 48 h postexercise.     

Training induced changes in maximum heart rate

The present study aimed to examine maximum heart rate (HRmax) in elite athletes. 130 (68 male, 23.2 +/- 4.8 years, 62 female, 21.0 +/- 5.1 years) endurance trained athletes, 40 (24 male, 24.0 +/- 5.6 years, 16 female, 22.8 +/- 4.6 years) anaerobically trained athletes, and 95 (39 male, 24.8 +/- 4.8 years, 56 female, 23.0 +/- 4.8 years) sedentary participants entered the study. All participants undertook a standard ramp protocol to volitional exhaustion to establish HRmax. Significant differences in HRmax were identified due to mode of exercise (p < 0.001) and gender (p = 0.001). The mean HRmax for the three modes of exercise were; aerobic 190.3 (SEE = 0.66), anaerobic 190.1 (SEE = 1.12) and sedentary 194.8 (SEE = 0.73) beats . min (-1) estimated at the average age of 23.1 years. The slope parameter for age varied between genders, the beta slope for females being significantly more negative than male subjects (- 1.1 beats . min (-1) . year (-1) vs. - 0.55 beats . min (-1) . year (-1), respectively). The predictive HRmax equation for male athletes was HRmax = 202 - 0.55 x age, and for female athletes it was HRmax = 216 - 1.09 x age. HRmax is similar between aerobically and anaerobically trained athletes. HRmax is significantly lower in athletes compared with age matched sedentary counterparts. The mechanisms underlying the lower HRmax remain to be elucidated.     

Effect of rhEPO administration on serum levels of sTfR and cycling performance

PURPOSE: We assessed the possibility of using soluble transferrin receptor (sTfR) as an indicator of doping with recombinant erythropoietin (rhEPO). METHODS: A double-blind, placebo-controlled study was conducted with the administration of 5,000 U of rhEPO (N = 10) or placebo (N = 10) three times weekly (181-232 U x kg(-1) x wk-1) for 4 wk to male athletes. We measured hematocrit and the concentration of hemoglobin, sTfR, ferritin, EPO, and quantified the effects on performance by measuring time to exhaustion and maximal oxygen uptake (VO2max) on a cycle ergometer. RESULTS: Hematocrit increased from 42.7 +/- 1.6% to 50.8 +/- 2.0% in the EPO group, and peaked 1 d after treatment was stopped. In the EPO group, there was an increase in sTfR (from 3.1 +/- 0.9 to 6.3 +/- 2.3 mg x L(-1) , P < 0.001) and in the ratio between sTfR and ferritin (sTfR-ferritin(-1)) (from 3.2 +/- 1.6 to 11.8 +/- 5.1, P < 0.001). The sTfR increase was significant after 1 wk of treatment and remained so for 1 wk posttreatment. Individual values for sTfR throughout the study period showed that 8 of 10 subjects receiving rhEPO, but none receiving placebo, had sTfR levels that exceeded the 95% confidence interval for all subjects at baseline (= 4.6 mg x L(-1)). VO2max increased from 63.6 +/- 4.5 mL x kg(-1) x min(-1) before to 68.1 +/- 5.4 mL x kg(-1) x min(-1) 2 d post rhEPO administration (7% increase, P = 0.001) in the EPO group. Hematocrit, sTfR, sTfR-ferritin(-1), and VO2max did not change in the placebo group. CONCLUSION: Serum levels of sTfR may be used as an indirect marker of supranormal erythropoiesis up to 1 wk after the administration of rhEPO, but the effects on endurance performance outlast the increase in sTfR.     

Changes in glutamine and glutamate concentrations for tracking training tolerance

PURPOSE: The purpose was to monitor high-performance athletes throughout training macrocycles and competitions and examine the changes in plasma glutamine (Gm) and glutamate (Ga) concentrations in order to develop a model of tolerance to training. METHODS: Plasma glutamine and glutamate concentrations of 52 National team athletes (31 male and 21 female) divided into male and female groups of speed skating, swimming, and cross-country skiing were measured in an early season rested condition to determine highest Gm and lowest Ga concentrations and over 2-4 macrocycles, which included heavy training to establish lowest Gm and highest Ga concentrations. RESULTS: In the rested condition, there were no differences within and between the male and female groups, excluding five athletes (OTA) who became overtrained in heavy training. The mean (+/-SD) Gm concentration was 585 +/- 54 micromol x L(-1), Ga concentration 101 +/- 16 micromol x L(-1), and Gm/Ga ratio 5.88 +/- 0.84 micromol x L(-1). The OTA had a significantly higher Ga concentration of 128 +/- 16 micromol x L(-1) and lower Gm/Ga ratio of 4.43 +/- 0.49 micromol x L(-1) than all the other groups. In heavy training, there was a significant decrease (P < 0.05) in Gm concentration to 522 +/- 53 micromol x L(-1), significant increase in Ga concentration to 128 +/- 19 micromol x L(-1) and significant decrease in Gm/Ga ratio to 4.15 +/- 0.57 micromol x L(-1). The OTA Gm concentration of 488 +/- 31 micromol x L(-1) was significant lower than only the male speed skating and swimming groups. However, the Ga concentration of 171 +/- 17 micromol x L(-1) and Gm/Ga ratio of 2.88 +/- 0.27 micromol x L(-1) were significantly higher and lower respectively than all other groups. CONCLUSIONS: Based on the changes in Gm and Ga concentration under different training conditions, we propose an athlete tolerance to training model where glutamine concentration reflects tolerance to volume of work and glutamate concentration reflects tolerance to high intensity training. We suggest that the Gm/Ga ratio may globally represent overall tolerance to training.     

Heart rate and blood pressure variability during heavy training and overtraining in the female athlete

We investigated heavy training- and overtraining-induced changes in heart rate and blood pressure variability during supine rest and in response to head-up tilt in female endurance athletes. Nine young female experimental athletes (ETG) increased their training volume at the intensity of 70-90% of maximal oxygen uptake (VO2max) by 125% and training volume at the intensity of < 70% of VO2max by 100% during 6-9 weeks. The corresponding increases in 6 female control athletes were 5% and 10%. The VO2max of the ETG and the control athletes did not change, but it decreased from 53.0 +/- 2.2 ml x kg(-1) x min(-1) to 50.2 +/- 2.3 ml x kg(-1) x min(-1) (mean+/-SEM, p < 0.01) in five overtrained experimental athletes. In the ETG, low-frequency power of R-R interval (RRI) variability during supine rest increased from 6 +/- 1 ms2 x 10(2) to 9 +/- 2 ms2 x 10(2) (p < 0.05). The 30/15 index (= RRI(max 30)/RRI(min 15), where RRI(max 30) denotes the longest RRI close to the 30th RRI and RRI(min 15) denotes the shortest RRI close to the 15th RRI after assuming upright position in the head-up tilt test), decreased as a result of training (analysis of variance, p = 0.05). In the ETG, changes in VO2max were related to the changes in total power of RRI variability during standing (r = 0.74, p < 0.05). Heart rate response to prolonged standing after head-up tilt was either accentuated or attenuated in the overtrained athletes as compared to the normal training state. We conclude that heavy training could increase cardiac sympathetic modulation during supine rest and attenuated biphasic baroreflex-mediated response appearing just after shifting to an upright position. Heavy-training-/overtraining-induced decrease in maximal aerobic power was related to decreased heart rate variability during standing. Physiological responses to overtraining were individual.     

Weight and diet concerns in Finnish female and male athletes

PURPOSES AND METHODS: Factors related to eating disorders were studied in five groups of female (N = 173) and male (N = 190) athletes, and in female (N = 79) and male (N = 61) controls. Factors associated with menstrual status were also examined. RESULTS: The sum of drive for thinness and body dissatisfaction subscales in the Eating Disorders Inventory was higher (P < 0.05) in female controls (median: 5; 25th and 75th percentiles: 1 and 14) than in endurance athletes (0; 0 and 2). The male groups did not differ from each other (P = 0.08) or from female subjects (P = 0.62). The preferred weight loss in the female controls (-4.0 kg; -6.2 and -2.0) was larger (P < 0.05) than in most athletic groups. Males, on average, did not want to lose weight (different from females, P < 0.001). The prevalence of weight reduction attempts (85%) in female weight-class athletes was higher (P < 0.05) compared with endurance and ballgame athletes and the controls (29-58%). In males, the frequency (93%) of weight reduction attempts was also highest in the weight-class athletes (P < 0.05). The prevalence of menstrual disturbances was 27-37% in aesthetic, endurance, and weight-class athletes, and 5% in controls (P = 0.06). CONCLUSIONS: The results confirmed that the risk for eating disorders is dependent on the type of sport. The claim that some female athlete groups are at greater risk than controls did not receive evidence.     

Bone mineral density of olympic-level female winter sport athletes

PURPOSE: To compare areal bone mineral density (aBMD) of female winter sport athletes to healthy controls of similar age and body mass index (BMI). METHODS: Areal BMD (g x cm(-2)) of the whole body, lumbar spine (L2-L4), and right proximal femur were assessed by dual energy x-ray absorptiometry in athletes (N = 40; age: 26.1 +/- 5.7 yr; ht: 165.6 +/- 0.1 cm; wt: 63.0 +/- 6.5 kg; BMI: 23.0 +/- 1.9 kg x m(-2)) involved in speed skating (N = 9), snowboarding (N = 13), freestyle skiing (N = 3), biathlon (N = 8), bobsleigh, skeleton, luge (N = 7), and controls (N = 21; age: 26.0 +/- 5.1 yr; ht: 165.8 +/- 0.1 cm; wt: 62.8 +/- 5.9 kg; BMI: 22.9 +/- 1.3 kg x m(-2)). RESULTS: Using independent t-tests, athletes had lower fat mass, percent body fat, and higher lean mass than controls (P < 0.001). Areal BMD was higher in athletes than controls for all skeletal sites (P 相似文献   

Effect of intense training on plasma leptin in male and female swimmers

PURPOSE: The purpose of this study was to determine whether fasting plasma leptin concentration was altered with an increase in training volume in competitive male and female athletes. METHODS: Intercollegiate male (N = 9) and female (N = 12) swimmers were examined during the preseason and at two times during the mid-season (mid-season 1 and mid-season 2) when training volume was relatively high (33,000 m.wk(-1)). Body composition (hydrostatic weighing), energy intake and expenditure, and fasting plasma leptin concentration were measured. RESULTS: In the women, there was a significant (P < 0.05) decline in fat mass (2 kg) with the increase in training volume, which was not accompanied by a reduction in fasting leptin (12.8 +/- 1.5 vs 11.0 +/- 1.2 vs 11.0 +/- 1.5 ng.mL(-1) for preseason, mid-season 1, and mid-season 2, respectively). In the men, there were no significant changes in body composition, body mass, or fasting leptin (4.4 +/- 0.8 vs 4.3 +/- 0.8 vs 4.6 +/- 0.8 ng.mL(-1), respectively). CONCLUSION: These findings suggest 1) plasma leptin is not sensitive to an increase in training volume and 2) leptin may not be indicative of changes in fat mass with an increase in training volume in female athletes. These data suggest that leptin may not be useful in monitoring relative training stress in athletes.     

Urinary profile of androgen metabolites in a population of sportswomen during the menstrual cycle

The aim of this investigation was to evaluate the urinary profile of androgen metabolites during menstrual cycle in both young-trained female athletes, and young sedentary women, not presenting any pathological signs. Urines were collected for 24 hours (08 : 00 a. m. the first day to 08 : 00 a. m. the second day) from all sportive and sedentary subjects. All steroids were measured by specific radioimmunological analysis, and the implications of these results in terms of concentrations and modifications by exercise will be discussed. During follicular phase, control values were respectively, testosterone glucuronide (TG): 1.67 +/- 0.70 nmol x mmol C -1; epitestosterone glucuronide (ETG): 2.51 +/- 0.88 nmol x mmol C -1; TG/ETG ratio: 0.72 +/- 0.26 and cortisol (FLU): 10.02 +/- 0.79 nmol x mmol C -1. No significant modifications were observed during luteal phase (respectively: TG: 1.48 +/- 0.50 nmol x mmol C -1; ETG: 2.65 +/- 0.93 nmol x mmol C -1; TG/ETG ratio: 0.67 +/- 0.31 and FLU: 9.29 +/- 3.37 nmol x mmol C -1. Similarly, no significant effect of physical training was observed on studied parameters between these two groups during either follicular phase (TG: 1.96 +/- 1.00 nmol x mmol C -1; ETG: 1.97 +/- 0.70 nmol x mmol C -1; TG/ETG ratio: 0.66 +/- 0.05 and FLU: 11.31 +/- 3.73 nmol x mmol C -1) or luteal phase (TG: 1.93 +/- 0.86 nmol x mmol C -1; ETG: 3.19 +/- 1.23 nmol x mmol C -1; TG/ETG ratio: 0.69 +/- 0.33 and FLU: 9.52 +/- 3.86 nmol x mmol C -1). It is concluded that although physical training could play a role in androgen metabolism, it has no significant incidence on urinary TG/ETG ratio. This study thus confirms that sportswomen can also be considered as normal subjects when they do not present any obvious endocrine disorder induced by physical activity.     

Asthma and wheezing among Norwegian elite athletes

PURPOSE: The objectives were to estimate the prevalence of self-reports of asthma and wheezing among Norwegian elite athletes compared with the general population and to estimate the associations between asthma and types of sports, exercise and team level. METHODS: The study population included all Norwegian elite athletes on the national junior and senior teams in 1997 (N = 1620) and a random sample from the general population (N = 1680). The surveys included items for asthma, respiratory symptoms, the history of participation in sports, sports events, and exercise and team level. The associations between the exposure variables and the outcomes adjusting for potential confounding factors were estimated using logistic regression. Crude (c) and adjusted odds ratio (aOR) with 95% confidence interval (CI) are presented. RESULTS: The prevalence of asthma was greater among athletes (10.0%) compared with that in the general population (6.9%) and remained so after controlling for confounders, aOR = 1.5 (95%CI 1.1-2.1). The risk of asthma was highest in sports requiring strength and endurance. This was the case for comparisons between athletes and the general population, aOR = 3.5 (1.6-7.6) for strength and aOR = 2.2 (1.4-3.5) for endurance sports. Comparisons within the sample of athletes using technical sports as the reference category revealed similar results, aOR = 3.0 (1.1-8.0) and aOR = 2.0 (1.0-4.3), respectively. Furthermore, asthma was more common among female than male athletes (aOR 1.7 (1.1-2.7)). Training more than 20 h x wk(-1) was associated with asthma when compared with levels of training less than 10 h x wk(-1) (aOR 1.9 (1.0-4.1)). CONCLUSION: These results indicate that asthma is more common among athletes compared with the general population. Asthma among athletes may define a subgroup of asthma cases for whom etiology is related to extensive exercise.     

Stroke volume does not plateau during graded exercise in elite male distance runners.

Stroke volume (SV) responses during graded treadmill exercise were studied in 1) elite male distance runners (N = 5), 2) male university distance runners (N = 10), and 3) male untrained university students (N = 10). METHODS: Cardiac output (Q) and SV were determined by a modified acetylene rebreathing procedure. RESULTS: There were no differences in SV responses among the three groups during the transition from rest to light exercise (P > 0.05). However, the rates of change of SV during light to maximal exercise in untrained subjects (slope = -0.1544 mL x beat(-1)) and university distance runners (slope = 0.1041) did not change, whereas it dramatically increased (P < 0.001) in elite distant runners (slope = 0.6734). Moreover, the elite distance runners showed a further slope increase in SV when heart rate was above 160 bpm, which resulted in an average maximal SV of 187 +/- 14 mL x beat(-1) compared with 145 +/- 8 and 128 +/- 14 mL x beat(-1) in the university runners and untrained students, respectively (P < 0.001). Similarly, max Q reached 33.8 +/- 2.3, 26.3 +/- 1.7, and 21.3 +/- 1.5 L x min(-1) in the three groups, respectively (P < 0.001). On the other hand, there was a nonsignificant tendency for maximal arteriovenous oxygen content difference to be lower in the elite athletes compared with the other groups. CONCLUSION: Results from university distance runners and untrained university students support the classic observation that SV plateaus at about 40% of maximal oxygen consumption despite increasing intensity of exercise. In contrast, stroke volume in the elite athletes does not plateau but increases continuously with increasing intensity of exercise over the full range of the incremental exercise test.     

Effects of induced metabolic alkalosis on prolonged intermittent-sprint performance

PURPOSE: Previous studies have shown that induced metabolic alkalosis, via sodium bicarbonate (NaHCO3) ingestion, can improve short-term, repeated-sprint ability. The purpose of this study was to assess the effects of NaHCO3 ingestion on a prolonged, intermittent-sprint test (IST). METHODS: Seven female team-sport athletes (mean +/- SD: age = 19 +/- 1 yr, VO2peak = 45.3 +/- 3.1 mL x kg(-1) x min(-1)) volunteered for the study, which had received ethics clearance. The athletes ingested two doses of either 0.2 g x kg(-1) of NaHCO3 or 0.138 g x kg(-1) of NaCl (placebo), in a double-blind, random, counterbalanced order, 90 and 20 min before performing the IST on a cycle ergometer (two 36-min "halves" of repeated approximately 2-min blocks: all-out 4-s sprint, 100 s of active recovery at 35% VO2peak, and 20 s of rest). Capillary blood samples were drawn from the ear lobe before ingestion, and before, during, and after each half of the IST. VO2 was also recorded at regular intervals throughout the IST. RESULTS: Resting plasma bicarbonate concentration ([HCO3-]) averaged 22.6 +/- 0.9 mmol x L(-1), and at 90 min post-ingestion was 21.4 +/- 1.5 and 28.9 +/- 2.8 mmol x L-1 for the placebo and NaHCO3 conditions, respectively (P < 0.05). Plasma [HCO3-] during the NaHCO3 condition remained significantly higher throughout the IST compared with both placebo and pre-ingestion. There was a trend toward improved total work in the second (P = 0.08), but not first, half of the IST after the ingestion of NaHCO3. Furthermore, subjects completed significantly more work in 7 of 18 second-half, 4-s sprints after NaHCO3 ingestion. CONCLUSIONS: The results of this study suggest that NaHCO3 ingestion can improve intermittent-sprint performance and may be a useful supplement for team-sport athletes.     

Stability of the blood lactate-heart rate relationship in competitive athletes

INTRODUCTION: The identification of the HR (or RPE) associated with blood lactate concentrations of 2.5 mmol x L(-1)(aerobic threshold) (AerT) and 4.0 mmol x L(-1)(anaerobic threshold) (AnT) is a common method for defining training intensities. It is often assumed that the HR at AerT and AnT changes with changes in fitness, much as the power output (Watts: W) associated with AerT and AnT is known to change. METHODS: We studied speed skaters (N = 13, 7 male, 6 female) during spring (deconditioned) and fall (conditioned) evaluations, using cycle ergometry (stage duration = 5 min) to determine W, HR, and RPE at AerT, AnT, and at maximal exercise (3000 (female) and 5000 (male) m cycle time trials). RESULTS: In the spring vs. fall evaluations, the power output at AerT was 127+/-12 vs 162+/-9 W (P<0.05), at AnT was 216+/-14 vs. 230+/-13 W (P<0.05), and at maximal exercise was 341+/-15 vs. 364+/-19 W (P<0.05); HR at AerT was 129+/-6 vs. 130+/-7 bpm (P>0.05), at AnT was 162+/-7 vs. 164+/-7 bpm (P>0.05), and at maximal exercise was 196+/-6 vs. 198+/-5 bpm (P>0.05); RPE at AerT was 2.7+/-0.9 vs. 2.6+/-0.8 (P>0.05), at AnT was 5.3+/-1.0 vs. 5.3+/-0.9 (P>0.05). CONCLUSIONS: These data suggest that although power output at AerT, AnT, and maximal exercise changes significantly with conditioning, there is no systematic change in the associated values for HR and/or RPE used as practical markers of training intensity. Accordingly, a single well-conducted evaluation may allow evaluation of appropriate training markers that may be longitudinally stable.     

Is determination of exercise intensities as percentages of VO2max or HRmax adequate?

Often exercise intensities are defined as percentages of maximal oxygen uptake (VO2max) or heart rate (HRmax). PURPOSE: The purpose of this investigation was to test the applicability of these criteria in comparison with the individual anaerobic threshold. METHODS: One progressive cycling test to exhaustion (initial stage 100 W, increment 50 W every 3 min) was analyzed in a group of 36 male cyclists and triathletes (24.9 +/- 5.5 yr; 71.6 +/- 5.7 kg; VO2max: 62.2 +/- 5.0 mL x min(-1) x kg(-1); individual anaerobic threshold = IAT: 3.64 +/- 0.41 W x kg(-1); HRmax: 188 +/- 8 min). Power output and lactate concentrations for 60 and 75% of VO2max as well as for 70 and 85% of HRmax were related to the IAT. RESULTS: There was no significant difference between the mean value of IAT (261 +/- 34 W, 2.92 +/- 0.65 mmol x L(-1)), 75% of VO2max (257 +/- 24 W, 2.84 +/-0.92 mmol x L(-1)), and 85% of HRmax (259 +/- 30 W, 2.98 +/- 0.87 mmol L(-1)). However, the percentages of the IAT ranged between 86 and 118% for 75% VO2max and 87 and 116% for 85% HRmax (corresponding lactate concentrations: 1.41-4.57 mmol x L(-1) and 1.25-4.93 mmol x L(-1), respectively). The mean values at 60% of VO2max (198 +/- 19 W, 1.55 +/- 0.67 mmol x L(-1)) and 70% of HRmax (180 +/- 27 W, 1.45 +/- 0.57 mmol x L(-1)) differed significantly (P < 0.0001) from the IAT and represented a wide range of intensities (66-91% and 53-85% of the IAT, 0.70-3.16 and 0.70-2.91 mmol x L(-1), respectively). CONCLUSIONS: In a moderately to highly endurance-trained group, the percentages of VO2max and HRmax vary considerably in relation to the IAT. As most physiological responses to exercise are intensity dependent, reliance on these parameters alone without considering the IAT is not sufficient.     

Blood lactate and heart rate during national and international women's basketball

AIM: In order to measure game intensity in female basketball players, 2 teams (Olympic National Team - I -and a team at 1(st) National Division - N) were studied for a total of 12 games (10 official competitions and 2 practice games -P). METHODS: Both blood lactate concentration ([La](b)) and mean heart rate (HR) were measured during the games and then compared with a progressive field test where maximal blood lactate (max[La](b)), individual lactate threshold and maximal heart rate (HR max) values were obtained. All different categories (International, National and Practice) and positions (Guard, Forward and Center) were taken into account in this study. RESULTS: Differences (p<0.05) in HR were found between all positions (Guard=185+/-5.9; Forward=175+/-11 and Center=167+/-12 beats x min(-1)) and between the International team and the rest of the categories (International=186+/-6; National=175+/-13 and Practice=170+/-11 beats x min(-1)). The [La](b) differed between the Guard and the other 2 positions (Guard=5.7+/-2.1; Forward=4.2+/-2.1 and Center=3.9+/-2.0 mmol x L(-1)) and between Practice and the rest of the categories (International=5.0+/-2.3; National=5.2+/-2.0 and Practice=2.7+/-1.2 mmol x L(-1)). The game intensity of International players reached 94.6% of their maximum HR value, whereas National players reached 90.8%, this percentage descending to 89.8% during Practice. International games reached the individual lactate threshold at 89.2% of the maximum HR; National games at 88.6%. CONCLUSION: We can conclude that the game intensity of female basketball increases according to the level of competition. It may also differ according to playing position, being greatest in guards. The game intensity at international level surpasses the individual lactate threshold, whereas it reaches a lower level in training games.     

Resistance exercise effects on plasma cortisol, testosterone and creatine kinase activity in anabolic-androgenic steroid users

Anabolic-androgenic steroids (AS) users have been reported to have an improved ability to withstand exhaustive resistance workouts and to recover more rapidly. The purpose of this investigation was to study the effects of AS usage on the cortisol (C), testosterone (T) and creatine kinase (CK) response to a resistance training session. Eleven trained body builders and power lifters (5.0 +/- 1.6 training years, mean +/- SD), 5 AS users (SU) and 6 nonusers (NU), completed a standardized resistance training session consisting of 10 sets of back squats at preset percentages of the subject's 1 RM max. Blood samples were obtained at rest, immediately post exercise and 24 hours after the exercise session. SU had significantly lower T at rest. Neither group exhibited a significant change in T at 1 min or at 24 h post exercise. Both the NU and SU exhibited a significant increase in CK at 1 min post exercise (129 +/- 23.3 U.l-1, 81 +/- 15.3 U.l-1, respectively), with the NU response significantly greater than the SU. After 24 h, CK for NU was significantly elevated (171.9 +/- 54.5 U.l-1) above resting level. In contrast, CK for SU had returned to resting level. NU had a significant increase in cortisol (C) (p less than 0.05) at 1 min post exercise (156.8 +/- 10.9 nmol.l-1), while the SU cortisol was not significantly changed. By 24 h C for the NU returned to resting level. The results of this investigation support the concept that AS users have a diminished CK response and an altered stress response to a single bout of resistance exercise.