The effect of exercise-induced hypoxemia on blood redox status in well-trained rowers

Exercise-induced arterial hypoxemia (EIAH), characterized by decline in arterial oxyhemoglobin saturation (SaO(2)), is a common phenomenon in endurance athletes. Acute intensive exercise is associated with the generation of reactive species that may result in redox status disturbances and oxidation of cell macromolecules. The purpose of the present study was to investigate whether EIAH augments oxidative stress as determined in blood plasma and erythrocytes in well-trained male rowers after a 2,000-m rowing ergometer race. Initially, athletes were assigned into either the normoxemic (n = 9, SaO(2) >92%, [Formula: see text]: 62.0 ± 1.9 ml kg(-1) min(-1)) or hypoxemic (n = 12, SaO(2) <92%, [Formula: see text]: 60.5 ± 2.2 ml kg(-1 )min(-1), mean ± SEM) group, following an incremental [Formula: see text] test on a wind resistance braked rowing ergometer. On a separate day the rowers performed a 2,000-m all-out effort on the same rowing ergometer. Following an overnight fast, blood samples were drawn from an antecubital vein before and immediately after the termination of the 2,000-m all-out effort and analyzed for selective oxidative stress markers. In both the normoxemic (SaO(2): 94.1 ± 0.9%) and hypoxemic (SaO(2): 88.6 ± 2.4%) rowers similar and significant exercise increase in serum thiobarbituric acid-reactive substances, protein carbonyls, catalase and total antioxidant capacity concentration were observed post-2,000 m all-out effort. Exercise significantly increased the oxidized glutathione concentration and decreased the ratio of reduced (GSH)-to-oxidized (GSSG) glutathione in the normoxemic group only, whereas the reduced form of glutathione remained unaffected in either groups. The increased oxidation of GSH to GSSG in erythrocytes of normoxemic individuals suggest that erythrocyte redox status may be affected by the oxygen saturation degree of hemoglobin. Our findings indicate that exercise-induced hypoxemia did not further affect the increased blood oxidative damage of lipids and proteins observed after a 2,000-m rowing ergometer race in highly-trained male rowers. The present data do not support any potential link between exercise-induced hypoxemia, oxidative stress increase and exercise performance.     

Does a bout of strength training affect 2,000 m rowing ergometer performance and rowing-specific maximal power 24 h later?

Rowers regularly undertake rowing training within 24 h of performing bouts of strength training; however, the effect of this practice has not been investigated. This study evaluated the impact of a bout of high-intensity strength training on 2,000 m rowing ergometer performance and rowing-specific maximal power. Eight highly trained male club rowers performed baseline measures of five separate, static squat jumps (SSJ) and countermovement jumps (CMJ), maximal rowing ergometer power strokes (PS) and a single 2,000 m rowing ergometer test (2,000 m). Subsequently, participants performed a high-intensity strength training session consisting of various multi-joint barbell exercises. The 2,000 m test was repeated at 24 and 48 h post-ST, in addition SSJ, CMJ and PS tests were performed at these time points and also at 2 h post-ST. Muscle soreness, serum creatine kinase (CK) and lactate dehydrogenase (LDH) were assessed pre-ST and 2, 24 and 48 h post-ST. Following the ST, there were significant elevations in muscle soreness (2 and 24 h, P < 0.01), CK (2, 24 and 48 h, P < 0.01), and LDH (2 h, P < 0.05) in comparison to baseline values. There were significant decrements across all time points for SSJ, CMJ and PS, which ranged between 3 and 10% (P < 0.05). However, 2,000 m performance and related measurements of heart rate and blood lactate were not significantly affected by ST. In summary, a bout of high-intensity strength training resulted in symptoms of muscle damage and decrements in rowing-specific maximal power, but this did not affect 2,000 m rowing ergometer performance in highly trained rowers.     

A comparison of critical velocity estimates to actual velocities in predicting simulated rowing performance.

The most accurate critical velocity (CV) estimate for the prediction of velocity during a simulated 2,000-m rowing race and the relationship to aerobic power were studied. Sixteen male rowers completed randomized maximal exertion trials (200, 400, 600, 800, 1,000, and 1,200 m), a maximal oxygen consumption (VO(2)max) on a Concept II rowing machine, and an actual 2,000-m simulated rowing race. Three mathematical models were applied to 4 rowing distance combinations producing 12 CV estimates. Seven of the 12 possible CV estimates were not significantly different from actual 2,000-m velocity. Comparison of the 3 CV models using all 6 trial distances revealed that the nonlinear model produced a CV estimate lower than the 2 linear CV models. CV was significantly correlated to VO(2)max (r = 0.91) and the mean velocity achieved during the 2,000-m simulated rowing race (r = 0.97). VO(2)max was significantly correlated to 2,000-m simulated rowing race velocity (r = 0.93).     

Development of race profiles for the performance of a simulated 2000-m rowing race.

The purpose of this study was to determine the race profile for a 2000-m simulated rowing race as well as the effect of training and gender on the race profile. Nineteen men and 19 women undertook a 2000-m simulated rowing race before and after 10 weeks of a typical off-season training program for rowing. Velocity was calculated every 200 m and the deviation in velocities from the mean race velocity (MRV) was plotted every 200 m to produce race profiles for each gender before and after training. The three fastest male rowers varied approximately 0.02 m.s from the MRV after training and displayed a constant-pace model. The fastest female rowers displayed an all-out strategy after training, producing large deviations from MRV. Average squared deviations from the mean (SDM) determined that all groups except the fastest females had a reduction in MRV deviation after training. These results suggest that the optimal race profile for a simulated 2000-m rowing race may be different between genders. Training reduces SDM and influences both male and female pacing patterns such that both exhibit a pacing strategy that is more similar to that of elite athletes in other events of similar and shorter duration.     

The development of physiological profiles and identification of training needs in NCAA female collegiate rowers using isoperformance curves

The purpose of this study was to propose a systematic method for the identification of training strategies and team selection using isoperformance curves. Rowing is a sport that relies on both aerobic and anaerobic energy contributions during a standard 2,000 m competition. The critical velocity model combines both aerobic (critical velocity, CV) and anaerobic (anaerobic rowing capacity, ARC) parameters in a single two-dimensional graphic display. The concept of isoperformance curves, a series of linear equations corresponding to minimum performance standards, allows for an objective overview of a large group of athletes of varying talent. The purpose of this study was to develop physiological profiles from the CV test, and to evaluate results with isoperformance curves to identify training strategies for collegiate rowers. Thirty-five female collegiate rowers completed four time trials over various distances (400, 600, 800, and 1,000 m). CV and ARC were calculated and compared between novice and varsity athletes. CV values for the varsity group were significantly higher than the novice group (P = 0.016). No significant differences were found between groups for ARC (P = 0.068). Mean and individual CV and ARC values were plotted on the x- and y-axes, respectively, and junior, collegiate, and elite isoperformance curves were developed using 2,000 m times from recent indoor rowing competitions. Stratification of athletes through isoperformance curves was used to identify specific training interventions (anaerobic and/or aerobic) needed to improve their 2,000 m performance. The information drawn from isoperformance curves and the parameters of the CV test can be used to provide an objective view of physiological capabilities and training needs on both an individual and team basis.     

The prediction of power and efficiency during near-maximal rowing

The relationship between power and gross efficiency during near-maximal rowing, and physiological measures of strength, power, aerobic and anaerobic capacities and United State Rowing Association (USRA) performance tests (independent variables) was investigated among collegiate male rowers. Criterion measures of rowing power and gross efficiency were measured in a moving-water rowing tank, using an oar instrumented with strain gauges to assess force and a potentiometer to assess oar position. Bivariate correlation analysis (n = 28) indicated no relationship between the independent variables and rowing gross efficiency (P > 0.05). Rowing power [mean (SD) 483.4 (34.75) W] was significantly related to inboard leg extension strength (IL strength, r = 0.63), outboard leg extension strength (r = 0.45), combined leg extension strength (r = 0.45), and time to complete the USRA 2000-m simulated rowing race (r = –0.52; P < 0.05). Stepwise regression using resampling cross-validation of 15 random samples (21 subjects per sample selected from a total group of 28 intercollegiate oarsmen) indicated that predictors of rowing power were IL strength and blood lactate following a peak oxygen uptake rowing test with significant multiple correlations of R = 0.61 to 0.86 (P < 0.05). The standard error of estimate (SEM) ranged from 18.1 to 29.9 W, or 5.3 (0.77)% of the criterion value. Cross-validation with a hold-out group (seven subjects per sample) was performed for each equation and correlations ranged from R = 0.14 to 0.97 (SEM = 8.0 to 38.9 W). In conclusion, data from the present study suggest that to increase rowing power, training should emphasize leg strength and anaerobic training to decrease the level of lactate accumulated during rowing.     

Oral creatine supplementation decreases plasma markers of adenine nucleotide degradation during a 1-h cycle test

We investigated the effect of oral creatine supplementation (20 g d(-1) for 7 days) on metabolism during a 1-h cycling performance trial. Twenty endurance-trained cyclists participated in this double-blind placebo controlled study. Five days after familiarization with the exercise test, the subjects underwent a baseline muscle biopsy. Thereafter, a cannula was inserted into a forearm vein before performing the baseline maximal 1-h cycle (test 1 (T1)). Blood samples were drawn at regular intervals during exercise and recovery. After creatine (Cr) loading, the muscle biopsy, 1-h cycling test (test 2 (T2)) and blood sampling were repeated. Resting muscle total creatine (TCr), measured by high performance liquid chromatography, was increased (P < 0.001) in the creatine group from 123.0 +/- 3.8 - 159.8 +/- 7.9 mmol kg(-1) dry wt, but was unchanged in the placebo group (126.7 +/- 4.7 - 127.5 +/- 3.6 mmol kg(-1) dry wt). The extent of Cr loading was unrelated to baseline Cr levels (r=0.33, not significant). Supplementation did not significantly improve exercise performance (Cr group: 39.1 +/- 0.9 vs. 39.8 +/- 0.8 km and placebo group: 39.3 +/- 0.8 vs. 39.2 +/- 1.1 km) or change plasma lactate concentrations. Plasma concentrations of ammonia (NH(3)) (P < 0.05) and hypoxanthine (Hx) (P < 0.01) were lower in the Cr group from T1 to T2. Our results indicate that Cr supplementation alters the metabolic response during sustained high-intensity submaximal exercise. Plasma data suggest that nett intramuscular adenine nucleotide degradation may be decreased in the presence of enhanced intramuscular TCr concentration even during submaximal exercise.     

Leptin as a marker of training stress in highly trained male rowers?

The purpose of this study was to investigate the potentially important role leptin may play during training monitoring in athletes. Twelve highly trained male rowers underwent a 3-week period of maximally increased training stress followed by a 2-week tapering period. Fasting blood was sampled after a rest day. Subjects also performed a maximal 2000-m rowing ergometer test before and after 3 weeks of heavy training, and after 2 weeks of tapering. Blood samples were obtained before, immediately after and after 30 min of recovery. Leptin concentrations were measured in duplicate by radioimmunoassay. Mean training time was about 100% higher during the heavy training period (17.5 h·week^–1) compared to the tapering period (8.9 h·week^–1). The 3-week heavy training period induced a significant reduction (P<0.05) in the fasting leptin concentration [from 2.5 (0.4) to 1.5 (0.4) ng·ml^–1]. Fasting plasma leptin was significantly increased by the end of the 2-week tapering period [2.0 (0.4) ng·ml^–1] but remained significantly lower compared to the pretraining value. Leptin levels were also significantly decreased only after the 2000-m rowing ergometer test performed at the end of the heavy training period. No differences in leptin concentrations were observed after other performance tests compared to their respective baseline values. In addition, fasting leptin concentration was significantly related to the weekly training time (r=–0.45; P=0.006). In conclusion, it appears that leptin is sensitive to the rapid and pronounced changes in training volume. A greater training time is associated with a lower leptin concentration in highly trained male rowers. It is suggested that it may be possible to direct typical rowing training by monitoring leptin status.     

Saliva immunoglobulins in elite women rowers

Saliva immunoglobulins (sIgA, sIgG, and sIgM) and upper respiratory tract infection (URTI) rates were evaluated in 20 elite female rowers and 19 nonathletes. Also, the influence of carbohydrate versus placebo beverage consumption on saliva immunoglobulin responses to rowing training sessions was measured in 15 rowers and in 5 non-exercising rowers. Saliva samples were collected 1 day before, and 5–10 min and 1.5 h after rowing or rest. Pre-exercise sIgA (but not sIgG or sIgM) concentration was 77% higher in the rowers compared to nonathletes (P < 0.001). Health records kept over 2 months revealed mean 5.2 (SEM 1.2) and 3.3 (SEM 1.1) days with URTI symptoms for the rowers and controls, respectively. For all 39 subjects, and for the 20 rowers separately, no significant correlation was found between URTI symptoms or insulin, cortisol, and growth hormone concentrations and pre-exercise or exercise-related changes in saliva immunoglobulin concentrations or secretion rates. The patterns of change in saliva immunoglobulin concentration and secretion rate did not differ between the carbohydrate and placebo rowing trials, or between exercised and rested athletes. These data indicated an increased sIgA concentration in the female elite rowers compared to the nonathletes, no association between saliva immunoglobulins and URTI, and no effect of a normal 2-hour training session or carbohydrate ingestion on saliva immunoglobulin concentrations or secretion rates. Accepted: 23 August 1999     

Seasonal changes in performance and free testosterone: cortisol ratio of elite female rowers

Summary The aim of this study was to investigate the seasonal behaviour of the plasma free testosterone: cortisol ratio (FTCR) and to relate hormonal changes to daily training volume and performance parameters on a rowing ergometer in elite female rowers. During 9 months of training preceding the 1988 Olympic Games the resting values of the FTCR in six elite female rowers were regularly (ten times) studied. Daily training volume was analysed in terms of rowed distance (l _rowad) and time (t). In addition, two performance parameters, the power at 4.0 mmol·l^–1 lactate concentration in the blood and the maximal power, were determined by a test on a rowing ergometer. The results indicated that the mean FTCR test value did not differ significantly from the level of the initial test or from the mean value of the directly preceding test. A significant negative correlation (r=–0.98, P<0.01) between FTCR and l _rowed was found in a period i.e. at a training camp, when there was a sudden increase in training volume. When FTCR was related to t a significant positive correlation (r=0.88, P<0.05) was found only for the period at the training camp. Our data further suggested that the FTCR alone was not an adequate indicator for the anabolic/catabolic balance in elite female rowers. This finding was contrary to previous findings in elite male rowers. However, in training practice the FTCR seems useful as an indicator of the hormonal training status of elite female rowers when complemented with data about total and free testosterone, performance parameters and knowledge concerning cyclic variations of the FTCR.Both departments co-operate in the working group Janus Jongbloed Research Centre, Utrecht, The Netherlands     

Age at menarche in relation to anthropometric characteristics,competition level and boat category in elite junior rowers

BACKGROUND: Within the context of the effects of training for sports on growth and maturation, there is very little menarcheal data for elite rowing athletes. Knowledge of the relationship of the maturational status with training level, different boat categories, and somatic features of the athletes will clarify the assumed impact of rowing training on the growth and maturational process of youngsters. AIM: The aim of this study was to determine the age at menarche in world top junior rowing athletes and to investigate its relationship with anthropometric characteristics, and competition level, rowing style and boat category. SUBJECTS AND METHODS: The sample consisted of 212 female junior rowers, with a mean chronological age of 17.6 +/- 0.8 years, all participants at the 1997 FISA World Junior Rowing Championships. Anthropometric dimensions, somatotype and body composition characteristics were measured, and age at menarche and training data were retrospectively obtained by questionnaires. RESULTS: Results revealed that the mean age at menarche of the total group of rowers was 12.8 +/- 1.2 years and did not differ from a non-athletic reference population. Rowers who started their rowing training before menarche (n = 78) showed a significant (p 相似文献   

Steroid and pituitary hormone responses to rowing: relative significance of exercise intensity and duration and performance level

Summary To analyse the relative significance of exercise intensity and duration as well as of performance capacity, hormone changes were recorded in 16 male rowers in two experiments separated by a year. The test exercises consisted of 7-min (at the supramaximal intensity) and 40-min rowing (at the level of the anaerobic threshold) on a rowing apparatus. In addition, somatotropin and cortisol responses were estimated in rowing for 8 × 2000 m in 14 rowers of national class. All three tests caused significant increases in somatotropin and cortisol concentrations in the blood. Follitropin concentrations were elevated in the 7-min exercise test in the second experiment and in the 40-min exercise test in both experiments. Lutropin and progesterone concentrations increased during the more prolonged exercise in the first experiment. No common change was found in testosterone concentrations. Cortisol and somatotropin responses to the 40-min rowing test at anaerobic threshold were more pronounced than to the 7-min exercise test at supramaximal intensity. When the rowers achieved a national class level of performance (the second experiment) the hormone responses to 7-min supramaximal exercise were increased. During the 8 × 2000-m rowing test cortisol but not somatotropin concentration increased to an extremely high level in the rowers of national class. It is concluded that in strenuous exercise cortisol and somatotropin responses were triggered by the exercise intensity threshold. The exact magnitude of the response would seem to have depended on additional stimuli caused by exercise duration and on possibility of mobilizing hormone reserves.     

Hormonal responses to three training protocols in rowing

The aim of this study was to examine the acute responses of serum growth hormone, testosterone, and cortisol to three training protocols in rowing. Six young rowers, members of the national team, carried out three frequently used protocols in rowing, i.e., an endurance, a moderate interval, and a resistance protocol, on separate days in a counterbalanced design. Blood samples were collected before, immediately after, and 4 h after exercise for the determination of growth hormone, testosterone, cortisol, and creatine kinase. All three protocols caused marked increases in growth hormone, the most spectacular being that immediately after the endurance protocol. The change in testosterone concentration immediately after the endurance protocol was significantly higher than the changes after the other two protocols. Cortisol concentration was significantly higher immediately after the endurance protocol than after the other two protocols, but remained relatively low in all cases, suggesting that these protocols did not considerably promote catabolism in muscle tissue. Based on these data, endurance training caused greater responses of the three hormones studied compared to interval or resistance training. In fact, resistance training (at intensities above 85% of 1RM) did not cause any significant changes in the three hormones. We therefore propose that evaluation of training programmes designed for elite athletes should include measurements of hormonal changes in order to ascertain that the programmes do cause the expected adaptations.     

Age at menarche in relation to anthropometric characteristics,competition level and boat category in elite junior rowers

Background : Within the context of the effects of training for sports on growth and maturation, there is very little menarcheal data for elite rowing athletes. Knowledge of the relationship of the maturational status with training level, different boat categories, and somatic features of the athletes will clarify the assumed impact of rowing training on the growth and maturational process of youngsters. Aim : The aim of this study was to determine the age at menarche in world top junior rowing athletes and to investigate its relationship with anthropometric characteristics, and competition level, rowing style and boat category. Subjects and methods : The sample consisted of 212 female junior rowers, with a mean chronological age of 17.6 &#45 0.8 years, all participants at the 1997 FISA World Junior Rowing Championships. Anthropometric dimensions, somatotype and body composition characteristics were measured, and age at menarche and training data were retrospectively obtained by questionnaires. Results : Results revealed that the mean age at menarche of the total group of rowers was 12.8 &#45 1.2 years and did not differ from a non-athletic reference population. Rowers who started their rowing training before menarche ( n = 78) showed a significant ( p &#104 0.01) later age at menarche compared with rowers who started their training after menarche ( n = 134), with mean ages of 13.4 and 12.4 years, respectively. No significant relationship between the age at menarche and physical and body composition characteristics could be demonstrated, with r varying between &#109 0.11 and 0.11. Furthermore, no significant differences in ages at menarche between competition levels (finalists versus non-finalists/medallists versus non-medallists) and between the different boat categories could be observed. Conclusions : Based on the results of this study, there is no direct evidence to state that intensive rowing training has a negative influence on the maturation status of junior female athletes.     

Determinants of 2,000 m rowing ergometer performance in elite rowers

This study examined the physiological determinants of performance during rowing over 2,000 m on an ergometer in finalists from World Championship rowing or sculling competitions from all categories of competion rowing (19 male and 13 female heavyweight, 4 male and 5 female lightweight). Discontinuous incremental rowing to exhaustion established the blood lactate threshold, maximum oxygen consumption (V˙O_2max) and power at V˙O_2max; five maximal strokes assessed maximal force, maximal power and stroke length. These results were compared to maximal speed during a 2,000 m ergometer time trial. The strongest correlations were for power at V˙O_2max, maximal power and maximal force (r=0.95; P<0.001). Correlations were also observed for V˙O_2max (r=0.88, P<0.001) and oxygen consumption (V˙O₂) at the blood lactate threshold (r=0.87, P=0.001). The physiological variables were included in a stepwise regression analysis to predict performance speed (metres per second). The resultant model included power at V˙O_2max, V˙O₂ at the blood lactate threshold, power at the 4 mmol·l^–1 concentration of blood lactate and maximal power which together explained 98% of the variance in the rowing performance over 2,000 m on an ergometer. The model was validated in 18 elite rowers, producing limits of agreement from –0.006 to 0.098 m·s^–1 for speed of rowing over 2,000 m on the ergometer, equivalent to times of –1.5 to 6.9 s (–0.41% to 1.85%). Together, power at V˙O_2max, V˙O₂ at the blood lactate threshold, power at 4 mmol·l^–1 blood lactate concentration and maximal power could be used to predict rowing performance. Electronic Publication     

Rowing performance,a mathematical model based on analysis of body dimensions as exemplified by body weight

Summary The theory of body dimensional influence on muscular work is employed for calculating the racing time of heavy- and lightweight male, and female rowers. The developed equation predicts racing results with an accuracy of 1 s±1.7 (SE). The prediction of a 2.6% advantage of the heavyweights (average bodyweight) 93 kg over the lightweights (70 kg) is in excellent agreement with observations (2.5%). Significant implications of the equation would be to row without a coxswain, to reduce boat weight to a minimum, and to increase racing distance e.g., for females to the racing distance rowed by the males (2,000 m) in order to reduce the influence of body dimensions on rowing performance.     

Rib stress fracture in a male adaptive rower from the arms and shoulders sport class: case report

Adaptive rowing is rowing or sculling for rowers with a physical disability. It debuted at the Paralympic Games in 2008. In order to ensure an equitable playing field, rowers with similar levels of physical function and disability are classified into different sport classes for competition. Rowers with an inability to use a sliding seat and impaired trunk function resulting in an inability to perform trunk forward and backward lean via hip flexion/extension are assigned to the Arms and Shoulders (AS) class. AS rowers have to use a chest strap set immediately below the chest in order to localize any trunk movement in AS class. Conditions created by adaptations of rowing equipment and technique within the AS class create unique stresses on the upper thoracic region. The following case report demonstrates how etiology and management of a rib stress fracture in an AS rower differs in comparison to able-body rowers. Of significant importance were the limitations imposed on the rower's ability to maintain rowing-specific fitness, due to the nature of the rib stress fracture and requirement to decrease force transmission through the ribs for several weeks. The rower's gradual return to full training was further impacted by obligatory use of the chest strap, which directly applied pressure over the injured area. Protective orthosis for the chest was designed and applied in order to dissipate pressure of the chest strap over the thorax during rowing (most importantly at the catch position) both on the ergometer and in the boat.     

Oral creatine supplementation decreases plasma markers of adenine nucleotide degradation during a 1‐h cycle test

We investigated the effect of oral creatine supplementation (20 g d^?1 for 7 days) on metabolism during a 1‐h cycling performance trial. Twenty endurance‐trained cyclists participated in this double‐blind placebo controlled study. Five days after familiarization with the exercise test, the subjects underwent a baseline muscle biopsy. Thereafter, a cannula was inserted into a forearm vein before performing the baseline maximal 1‐h cycle (test 1 (T1)). Blood samples were drawn at regular intervals during exercise and recovery. After creatine (Cr) loading, the muscle biopsy, 1‐h cycling test (test 2 (T2)) and blood sampling were repeated. Resting muscle total creatine (TCr), measured by high performance liquid chromatography, was increased (P < 0.001) in the creatine group from 123.0 ± 3.8 ? 159.8 ± 7.9 mmol kg^?1 dry wt, but was unchanged in the placebo group (126.7 ± 4.7 ? 127.5 ± 3.6 mmol kg^?1 dry wt). The extent of Cr loading was unrelated to baseline Cr levels (r=0.33, not significant). Supplementation did not significantly improve exercise performance (Cr group: 39.1 ± 0.9 vs. 39.8 ± 0.8 km and placebo group: 39.3 ± 0.8 vs. 39.2 ± 1.1 km) or change plasma lactate concentrations. Plasma concentrations of ammonia (NH₃) (P < 0.05) and hypoxanthine (Hx) (P < 0.01) were lower in the Cr group from T1 to T2. Our results indicate that Cr supplementation alters the metabolic response during sustained high‐intensity submaximal exercise. Plasma data suggest that nett intramuscular adenine nucleotide degradation may be decreased in the presence of enhanced intramuscular TCr concentration even during submaximal exercise.     

Physiological factors to predict on traditional rowing performance

The purpose of this study was to determine the best prediction factors of traditional rowing performance in traditional elite (ER) and amateur (AR) rowers. Average power during the 20-min all-out test (W _20 min), average power output which elicited a blood lactate concentration of 4 mmol l^?1 $ \left( {W_{{4\;{\text{mmol}}\;{\text{l}}^{ - 1} }} } \right), $ power output in 10 maximal strokes (W _10 strokes), maximal strength and muscle power output during a bench pull (BP) and anthropometric values were all measured for 46 trained male rowers aged 21–30 with 8–15 years of rowing training experience. The ER group showed greater body mass (5%, p < 0.05), greater fat free body mass (5%, p < 0.05), greater 1RM_BP (13%, p < 0.001), longer training experience (43%, p < 0.001), and a shorter time in the 2,000 m test (4%, p < 0.05) than the AR group. The ER group showed higher power output values in W _10 strokes (9%, p < 0.01), W _20 min (15.4%, p < 0.01) and $ W_{{4\;{\text{mmol}}\;{\text{l}}^{ - 1} }} $ (17.8%, p < 0.01) compared with the AR group. Significant relationships were observed between $ W_{{4\;{\text{mmol}}\;{\text{l}}^{ - 1} }} $ and W _20 min (r = 0.65 and 0.80; p < 0.01 in ER and AR, respectively). The indices for rowing performance suggested that W _20 min, $ W_{{4\;{\text{mmol}}\;{\text{l}}^{ - 1} }} , $ W _10 strokes and 1RM_BP were the most important predictors of traditional rowing performance in elite and amateur rowers.     

Creatine supplementation enhances maximum voluntary isometric force and endurance capacity in resistance trained men

The present study examined the hypothesis that creatine (Cr) supplementation can increase the performance of isometric exercise in subjects engaged in a strength training program. Ten male subjects were tested in three experimental trials 7 days apart (days 1, 8 and 15). In each trial the subjects' maximum voluntary force of contraction (MVC) was measured in both legs and isometric endurance capacity at 80, 60, 40 and 20% of MVC of their stronger leg (knee extensor group) was measured with a 4-min rest between contractions. Additionally, the subjects' isometric endurance capacity at 80% of MVC of their weaker leg was measured in 10 repeated bouts interspersed with 2-min rest. A double-blind cross-over design was adopted for administering Cr or placebo. Subjects were randomized into either the Cr–placebo (Group A: days 2–6: 10 g day^?1 of Cr; days 9–13: 10 g day^?1 of glucose polymers) or the placebo–Cr group (Group B reverse supplementation order). The daily diet was analysed, and urine samples from 24-h collections were subjected to Cr and creatinine analysis. In each subject, ≈18 g (35%) of Cr was eliminated in the urine during the Cr supplementation period. MVC increased by about 10% (P < 0.01 in the weaker leg, P < 0.05 in the stronger leg) and body mass increased by 1.7 ± 0.4 kg (2.3%, P < 0.01) and 1.8 ± 0.3 kg (2.1%, P < 0.01) in groups A and B, respectively, after Cr supplementation, while energy intake and diet composition remained constant throughout the study. The subjects' endurance capacity increased (P < 0.05) in all the bouts after Cr supplementation. Muscle hypertrophy in response to Cr supplementation and weight training may explain the findings of the present study.