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1.
In this study, we examined the effects of weight reduction by restricting energy intake on muscle function and serum concentrations of myogenic enzymes in judoists. Twenty-seven male judoists aged 19.3±0.6 years (mean±s) were divided into three groups based on the extent of body weight reduction: high weight reduction (height 1.70±0.05?m, body mass 78.5 ±13.6?kg), low weight reduction (height 1.70±0.05?m, body mass 80.7±13.1?kg) and a group that maintained body weight while continuing to perform exercise training (height 1.78± 0.07?m, body mass 78.7±8.8?kg). Body composition, blood biochemistry, energy intake and anaerobic power were assessed on four occasions: 20 days (baseline data), 4 days and 1 day before and 7 days after competition. Compared with baseline, body mass and fat-free mass were significantly lower 1 day before competition in the high and low weight reduction groups (both P?<0.01); these changes persisted for 7 days after competition in the high weight reduction group. Serum creatine kinase was significantly elevated 1 day before competition in all groups (all P?<0.05), and remained higher 7 days after competition in both the high and low weight reduction groups. Compared with baseline, maximal anaerobic power was significantly lower 1 day before competition only in the high weight reduction group (P?<0.01). Our results suggest that energy restriction in addition to intense exercise training before major competition has an adverse effect on anaerobic power and elevates serum creatine kinase concentration, leading to an impairment of muscular function and an increased susceptibility of muscle tissue to injury.  相似文献   

2.
Strenuous physical exercise of the limb muscles commonly results in damage, especially when that exercise is intense, prolonged and includes eccentric contractions. Many factors contribute to exercise-induced muscle injury and the mechanism is likely to differ with the type of exercise. Competitive sports players are highly susceptible to this type of injury. AM3 is an orally administered immunomodulator that reduces the synthesis of proinflammatory cytokines and normalizes defective cellular immune fractions. The ability of AM3 to prevent chronic muscle injury following strenuous exercise characterized by eccentric muscle contraction was evaluated in a double-blind and randomized pilot study. Fourteen professional male volleyball players from the First Division of the Spanish Volleyball League volunteered to take part. The participants were randomized to receive either placebo (n=7) or AM3 (n=7). The physical characteristics (mean+/-s) of the placebo group were as follows: age 25.7+/-2.1 years, body mass 87.2+/-4.1 kg, height 1.89+/-0.07 m, maximal oxygen uptake 65.3+/-4.2 ml.kg(-1).min(-1). Those of the AM3 group were as follows: age 26.1+/-1.9 years, body mass 85.8+/-6.1 kg, height 1.91+/-0.07 m, maximal oxygen uptake 64.6+/-4.5 ml.kg(-1).min(-1). All participants were evaluated for biochemical indices of muscle damage, including concentrations of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, creatine kinase (CK) and its MB fraction (CK-MB), myoglobin, lactate dehydrogenase, urea, creatinine and gamma-glutamyltranspeptidase, both before and 30 days after treatment (over the peak of the competitive season). In the placebo group, competitive exercise (i.e. volleyball) was accompanied by significant increases in creatine kinase (494+/-51 to 560+/-53 IU.l(-1), P < 0.05) and myoglobin (76.8+/-2.9 to 83.9+/-3.1 microg.l(-1), P < 0.05); aspartate aminotransferase (30.8+/-3.0 to 31.1+/-2.9 IU.l(-1)) and lactate dehydrogenase (380+/-31 to 376+/-29 IU.l(-1)) were relatively unchanged after the 30 days maximum effort. AM3 not only inhibited these changes, it led to a decrease from baseline serum concentrations of creatine kinase (503+/-49 to 316+/-37 IU.l(-1), P < 0.05) and myoglobin (80.1+/-3.2 to 44.1+/-2.6 IU.l(-1), P < 0.05), as well as aspartate aminotransferase (31.1+/-3.3 to 26.1+/-2.7 IU.l(-1), P < 0.05) and lactate dehydrogenase (368+/-34 to 310+/-3 IU.l(-1), P < 0.05). The concentration of CK-MB was also significantly decreased from baseline with AM3 treatment (11.6+/-1.2 to 5.0+/-0.7 IU.l(-1), P < 0.05), but not with placebo (11.4+/-1.1 to 10.8+/-1.4 IU.l(-1)). In conclusion, the use of immunomodulators, such as AM3, by elite sportspersons during competition significantly reduces serum concentrations of proteins associated with muscle damage.  相似文献   

3.
Bilateral leg extension power and fat-free mass in young oarsmen   总被引：1，自引：0，他引：1  
We evaluated the impact of bilateral leg extension power and fat-free mass on 2000 m rowing ergometer performance in 332 young oarsmen (age 21+/-2 years, height 1.76+/-0.05 m, body mass 62+/-6 kg; mean+/-s). The 2000 m rowing performance time was correlated with height (1.62-1.93 m; R2=0.23, P<0.001), body mass (53-95 kg; R2=0.53, P<0.001), fat-free mass (47-82 kg; R2=0.58, P<0.001) and bilateral leg extension power (1202-3302 W; R2=0.38, P<0.001). Multiple regression analysis selected fat-free mass and bilateral leg extension power as regressor variables. Fat-free mass explained 58% of the variability in rowing performance and the inclusion of bilateral leg extension power improved the power of prediction by 5%. The results suggest that rowing involves almost every muscle in the body and that bilateral leg extension power is very important during this activity.  相似文献   

4.
The aims of this study were to assess the validity and reliability of body volume and percent body fat determined by sulphur hexafluoride dilution, using underwater weighing as the criterion method, and to determine the influence of the magnitude of body volume. Thirty-one healthy Japanese individuals aged 18-27 years (16 males: height 1.70 +/- 0.06 m, mass 64.8 +/- 7.7 kg; 15 females: height 1.60 +/- 0.05 m, mass 55.2 +/- 6.2 kg; mean +/- s) participated in the study. Sulphur hexafluoride dilution measures the concentration of sulphur hexafluoride gas in the chamber (BSF-200, Shimazu Corp.). Underwater weighing was performed five times using a weight scale (AD-6204, A&D) after residual volume had been determined (System9, Minato Medical Corp.). There were no significant differences in the mean between two trials for body volume, body density or percent body fat determined by sulphur hexafluoride dilution. The intra-class correlation coefficient of these variables ranged from 0.985 to 0.999. The results suggest that sulphur hexafluoride dilution is a reliable method for assessing body composition. There was no significant difference in body volume or percent body fat between sulphur hexafluoride dilution (males: 61.3 +/- 7.6 litres, 18.4 +/- 6.7%; females: 52.8 +/- 6.9 litres, 21.0 +/- 8.9%) and underwater weighing (males: 60.6 +/- 7.0 litres, 15.6 +/- 3.5%; females: 53.0 +/- 6.5 litres, 23.7 +/- 6.1%) and there was a high correlation between the two (r = 0.997, P < 0.05). A Bland-Altman plot of the difference between percent body fat estimated by underwater weighing and sulphur hexafluoride dilution versus average percent body fat by the two methods showed no systematic difference (mean difference = -0.12 +/- 6.6 kg). The upper and lower limits of agreement were 13.2% and -13.4%, respectively. Determination by sulphur hexafluoride dilution resulted in both over- and underestimations in body volume and the difference between the two body volumes (determined by underwater weighing and by sulphur hexafluoride dilution) was inversely proportional to the mean body volume by the two methods. This suggests that improvements need to be made to the device or to the technique to maintain a constant volume of sulphur hexafluoride in the chamber.  相似文献   

5.
The aim of this study was to examine heart rate, blood lactate concentration and estimated energy expenditure during a competitive rugby league match. Seventeen well-trained rugby league players (age, 23.9 +/- 4.1 years; VO2max, 57.9 +/- 3.6 ml x kg(-1) x min(-1); height, 1.82 +/- 0.06 m; body mass, 90.2 +/- 9.6 kg; mean +/- s) participated in the study. Heart rate was recorded continuously throughout the match using Polar Vantage NV recordable heart rate monitors. Blood lactate samples (n = 102) were taken before the match, after the warm-up, at random stoppages in play, at half time and immediately after the match. Estimated energy expenditure during the match was calculated from the heart rate-VO2 relationship determined in laboratory tests. The mean team heart rate (n = 15) was not significantly different between halves (167 +/- 9 vs 165 +/- 11 beats x min(-1)). Mean match intensity was 81.1 +/- 5.8% VO2max. Mean match blood lactate concentration was 7.2 +/- 2.5 mmol x l(-1), with concentrations for the first half (8.4 +/- 1.8 mmol x l(-1)) being significantly higher than those for the second half (5.9 +/- 2.5 mmol x l(-1)) (P<0.05). Energy expenditure was approximately 7.9 MJ. These results demonstrate that semi-professional rugby league is a highly aerobic game with a considerable anaerobic component requiring high lactate tolerance. Training programmes should reflect these demands placed on players during competitive match-play.  相似文献   

6.
We describe the physiological characteristics of amateur outrigger canoe paddlers. Twenty-one paddlers (13 males, 8 females) were evaluated for body stature, aerobic power, muscular strength and endurance, peak paddle force, flexibility and 250 m sprint paddle performance at the end of the outrigging season. The mean variables (+/- s) for the males were: age 27 +/- 9 years, height 175 +/- 5 cm, body mass 80 +/- 5 kg, arm span 178 +/- 7 cm, sitting height 100 +/- 2 cm, aerobic power 3.0 +/- 0.4 l x min(-1), maximum bench press strength 85 +/- 19 kg, right peak paddle force 382 +/- 66 N and left peak paddle force 369 +/- 69 N. For the females, these were: age 26 +/- 6 years, height 168 +/- 5 cm, body mass 70 +/- 8 kg, arm span 170 +/- 5 cm, sitting height 97 +/- 3 cm, aerobic power 2.3 +/- 0.51 l x min(-1), maximum bench press strength 47 +/- 10 kg, right peak paddle force 252 +/- 63 N and left peak paddle force 257 +/- 60 N. Analysis of variance revealed differences (P < 0.05) between the dominant and non-dominant sides of the body for peak paddle force, isokinetic internal and external rotation, and flexion and extension torque of the shoulder joint. The outrigger canoe paddlers were generally within the range of scores found to describe participants of other water craft sports. Outrigger canoeists should be concerned with the muscular strength imbalances associated with paddling technique.  相似文献   

7.
The aim of this study was to assess the relationship between several commonly used aerobic and anaerobic cycle ergometer tests and performance during a treadmill cycling hill climb. Eight competitive cyclists (age 27+/-7 years; body mass 73.2+/-5.2 kg; height 177+/-6 cm; mean +/- s) completed six tests in random order: a lactate minimum test; a Wingate anaerobic power test; and two 6-km climbs at 6% and two 1-km climbs at 12% gradient performed on a motorized treadmill. The mean times and power outputs for the 6-km and 1-km climbs were 16:30+/-1:08 min: s and 330+/-17.8 W, and 4:19+/-0:27 min: s and 411+/-24.4 W, respectively. The best individual predictor of 6-km and 1-km performance times was the time for the corresponding climb at the other distance (r = 0.97). The next strongest predictor of both hill climb performances was the average power produced during the Wingate test divided by body mass. Stepwise regression analysis showed that the two variables contributing most to the prediction equation for both climbs were the Wingate average power per unit of body mass and maximal aerobic power divided by total mass (rider + bike), which together accounted for 92 and 96% of the variability in the 6-km and 1-km climbs. In conclusion, among competitive cyclists, the Wingate average power per unit of body mass was the best single predictor of simulated cycling hill climb performance at the distance and gradient used.  相似文献   

8.
A total of 36 non-elite male body builders were observed at the time of competition. Their mean physical characteristics (+/- S.D.) were: age, 24.6 +/- 4.8 years; height, 174.4 +/- 6.7 cm; bodyweight, 80.3 +/- 11.0 kg. Their body composition values were: percentage body fat, 9.3 +/- 1.6%; fat-free mass, 72.8 +/- 9.8 kg. The mean somatotype for all subjects was: endomorphy, 2.3 +/- 0.6; mesomorphy, 6.2 +/- 0.9; ectomorphy, 1.2 +/- 0.6. The body proportions (cm) included: biacromial diameter/bi-iliac diameter, 1.463 +/- 0.132; torso length/height, 0.468 +/- 0.018; chest circumference/abdominal circumference, 1.345 +/- 0.059. The body builders in the present study were younger, had lower bodyweights, lower fat-free mass, lower mesomorphy ratings, smaller circumferences, and smaller skeletal dimensions than elite body builders reported in the scientific literature. When the body builders in the present study were divided into successful and unsuccessful groups based on actual competition results, a multiple-discriminant analysis found that biacromial diameter/bi-iliac diameter, torso length/height, chest circumference/abdominal circumference, percentage body fat, height, and bodyweight accounted for 80.6% of the explained variance. These data indicate that the success of a body builder can be accounted for in large part by easily obtained physical variables.  相似文献   

9.
许汪宇  蔡广  沈勋章  葛珺 《体育科研》2013,34(1):75-78,103
目的：探讨女青少年运动员生长发育与15S无氧功特点及其相关关系．对象和方法：以650名上海市10-18岁女运动员为对象,分别测试身高、体重、体脂率、肌肉量、瘦体重和立定跳远．并采集15S无氧功率自行车的最大功率、平均功率、最大转速、最大转速出现时间等指标,分析其特点及相关性、结果：上海市女青少年运动员身高及体重在10-13岁、最大和平均功率在㈤～15岁增长最快,15岁后趋于稳定,瘦体重、体重和肌肉与功率的相关性依次降低、结论：对女青少年运动员速度力量的训练要在15岁之前,评价女青少年运动员磷酸原代谢能力时最好使用瘦体重相对功率。  相似文献   

10.
In this study, we assessed the ventilatory response in 84 children (46 males: age 8.1 +/- 1.0 years, body mass 34.2 +/- 7.9 kg, height 1.32 +/- 0.16 m; 38 females: age 8.0 +/- 0.8 years, body mass 31.7 +/- 8.7 kg, height 1.31 +/- 0.08 m) during a cycle ergometer test to determine if there was an influence of gender on ventilatory efficiency. The test commenced at 25 W and increased by 10 W every minute. Expired air was collected through a face mask and analysed breath by breath. The ventilatory anaerobic threshold was determined according to gas exchange methods and we focused our attention on the analysis of carbon dioxide production (VCO(2)), ventilation (V(E)), the ratio V(E)/VCO(2) and its slope. Differences between the sexes at maximal power output were strongly significant for V(E) and VCO(2) (P = 0.0001 and P = 0.0004 respectively) and moderately significant for the V(E)/VCO(2) ratio (P = 0.05). The slope of V(E) versus VCO(2) was 30.8 +/- 4.2 for males and 29.4 +/- 3.2 for females, with no difference between the sexes (P = 0.1). In conclusion, although the peak values of V(E) and VCO(2) were significantly different between the sexes, there were no such differences in ventilatory efficiency during a maximal incremental test expressed as the slope of V(E)/VCO(2), at least in young children.  相似文献   

11.
A well-documented observation after eccentric exercise is a reduction in maximal voluntary force. However, little is known about the ability to maintain maximal isometric force or generate and maintain dynamic peak power. These aspects of muscle function were studied in seven participants (5 males, 2 females). Knee extensor isometric strength and rate of fatigue were assessed by a sustained 60 s maximal voluntary contraction at 80 degrees and 40 degrees knee flexion, corresponding to an optimal and a shortened muscle length, respectively. Dynamic peak power and rate of fatigue were assessed during a 30 s Wingate cycle test. Plasma creatine kinase was measured from a fingertip blood sample. These variables were measured before, 1 h after and 1, 2, 3 and 7 days after 100 repetitions of the eccentric phase of the barbell squat exercise (10 sets x 10 reps at 80% concentric one-repetition maximum). Eccentric exercise resulted in elevations in creatine kinase activity above baseline (274+/-109 U x l(-1); mean +/- s(x)) after 1 h (506+/-116 U x l(-1), P < 0.05) and 1 day (808+/-117 U x l(-1), P < 0.05). Isometric strength was reduced (P < 0.05) for 7 days (35% at 1 h, 5% at day 7) and the rate of fatigue was lower (P < 0.05) for 3 days at 80 degrees and for 1 day at 40 degrees. Wingate peak power was reduced to a lesser extent (P < 0.05) than isometric strength at 1 h (13%) and, although the time course of recovery was equal, the two variables differed in their pattern of recovery. Eccentrically exercised muscle was characterized by an inability to generate high force and power, but an improved ability to maintain force and power. Such functional outcomes are consistent with the proposition that type II fibres are selectively recruited or damaged during eccentric exercise.  相似文献   

12.
This investigation was undertaken in an effort to establish physiological characteristics of soccer players and to relate them to positional roles. A total of 135 footballers (age 24.4 +/- 4.6 years) were assessed for body mass, % body fat, haemoglobin, maximal oxygen uptake (VO2 max), leg power, anaerobic capacity and speed prior to an English league season. The sample included 13 goalkeepers, 22 full-backs, 24 centre-backs, 35 midfield players and 41 forwards. The goalkeepers were significantly heavier (86.1 +/- 5.5 kg; P < 0.01) than all groups except the centre-backs, had significantly higher estimated body fat percentages than centre-backs, forwards, midfield players (P < 0.01) or full-backs (P < 0.05), significantly lower estimated VO2 max values (56.4 +/- 3.9 ml kg-1 min-1; P < 0.01) and were slowest over 60 m (12.71 +/- 0.42 s). The midfield players had the highest predicted VO2 max values (61.4 +/- 3.4 ml kg-1 min-1), this being significantly greater (P < 0.05) than for the centre-backs. The forwards were the fastest group over 60 m (12.19 +/- 0.30 s), being significantly quicker than goalkeepers or centre-backs (P < 0.01) and full-backs (P < 0.05). Anaerobic power, as well as knee extensor torques (corrected for body mass) and extensor-flexor ratios, were similar between groups. No difference in estimated body fat percentage was observed between any of the outfield players, and haemoglobin concentrations were similar among players of all positions.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

13.
To evaluate the effectiveness of recovery strategies on physical performance during a 3-day tournament style basketball competition, 29 male players (mean age 19.1 years, s= 2.1; height 1.84 m, s= 0.34; body mass 88.5 kg, s= 14.7) were assigned to one of three treatment groups: carbohydrate+stretching (7.7 g kg(-1) day(-1), s= 1.7; 'n = 9), cold water immersion (11 degrees C, 5 x 1; n = 10) or full leg compression garments (18 mmHg, approximately 18 h; n = 10). Effects of the recovery strategies on pre-post tournament performance tests were expressed as the mean change (% +/- standard deviation of the change score). Changes and differences were standardized for accumulated game time, assessed against the smallest worthwhile change for each test, and reported qualitatively. Accumulated fatigue was evident over the tournament with small to moderate impairments in performance tests. Sprint and agility performance decreased by 0.7% (s = 1.3) and 2.0% (s = 1.9) respectively. Vertical jump decreased substantially after the first day for all treatments, and remained suppressed post-tournament. Cold water immersion was substantially better in maintaining 20-m acceleration with only a 0.5% (s = 1.4) reduction in 20-m time after 3 days compared with a 3.2% (s = 1.6) reduction for compression. Cold water immersion (-1.4%, s = 1.7) and compression (-1.5%, s = 1.7) showed similar substantial benefits in maintaining line-drill performance over the tournament, whereas carbohydrate+stretching elicited a 0.4% (s =1.8) reduction. Sit-and-reach flexibility decreased for all groups, although cold water immersion resulted in the smallest reduction in flexibility. Basketball tournament play elicited small to moderate impairments in physical test performance. In conclusion, cold water immersion appears to promote better restoration of physical performance measures than carbohydrate + stretching routines and compression garments.  相似文献   

14.
The aim of this study was to examine the effects of an acute stretching regime on hamstring muscle fatigue and rating of perceived exertion during a dynamic, sub-maximal bout of resistance exercise. Sixteen healthy males (age 25.7 +/- 4.3 years, height 1.81 +/- 0.06 m, body mass 87.5 +/- 15.1 kg; mean +/- s) and 16 healthy females (age 24.9 +/- 4.5 years, height 1.67 +/- 0.06 m, body mass 62.9 +/- 9.4 kg) volunteered to participate in two experimental sessions. After establishing their one-repetition maximum for the hamstring curl, the participants were assigned at random to one of two groups. Group 1 performed three bouts of 20 s hamstring stretches with the assistance of one of the investigators, while group 2 did not perform the stretches; instead, they sat resting for 3 min. Then, after stretching or resting, the participants performed as many hamstring curls as they could at 60% of their one-repetition maximum established earlier. All participants were assessed for their perceived exertion using a modified Borg category ratio (CR-10) scale. The participants returned within 1 week to complete the experiment. This time group 1 did not perform hamstring stretches, whereas group 2 did. As on the first occasion, all participants performed hamstring curls after stretching or resting. The participants in group 1 were able to perform more curls on the second day of testing than their counterparts in group 2. There were no significant differences between males and females or between the stretch and non-stretch conditions. There was a significantly higher first repetition rating of perceived exertion for the stretch condition (2.88 +/- 1.01) than for the non-stretch condition (2.50 +/- 0.95); there was no significant difference in the median ratings of perceived exertion between the stretch and non-stretch conditions. Significantly higher power function exponents were exhibited in the non-stretch (0.57 +/- 0.16) than in the stretch condition (0.51 +/- 0.12). In addition, females exhibited significantly higher power function exponents than males, irrespective of stretch condition and day (females: 0.59 +/- 0.12; males: 0.49 +/- 0.11). In conclusion, we found a small but statistically significant effect of an acute bout of stretching on ratings of perceived exertion during fatiguing hamstring muscle resistance exercise.  相似文献   

15.
Abstract

The purpose of the present study was to evaluate dietary intake and body composition of elite rhythmic gymnastics (RG) athletes prior to a competition event. Sixty-seven rhythmic gymnasts (18.7 ± 2.9 years old) of high performance level, with 36.6 ± 7.6 h of training/week were evaluated in order to collect training and competition data, medical and gynaecological history, detailed dietary intake and body composition before an international competition. The majority of the participants (n = 40; 59.7%) had already menstruated, but age of menarche was delayed (15.3 ± 1.3 years) and all revealed menstrual irregularities. Gymnasts' body mass (48.4 ± 4.9 kg) and body mass index (BMI; 17.4 ± 1.1 kg/m2) were below the normal for age, and height (1.66 ± 0.05 m) was normal or even slightly above normal for age. Body fat was 9.0 ± 2.0% with no significant differences between age strata. Gymnasts exhibited low energy availability (EA; 31.5 ± 11.9 kcal/kg fat-free mass (FFM)/day). The average carbohydrate and protein intakes were 5.1 ± 2.3 g/kg/day and 1.6 ± 04 g/kg/day, which correspond to 51.4 ± 7.2% and 16.9 ± 3.4% of total energy intakes, respectively; average fat contribution was 33.0 ± 5.3%. Low intakes of pantothenic acid, folate and vitamins D, E and K and of minerals, including calcium, iron and magnesium were reported. Intakes of thiamine, riboflavin, niacin, vitamins A, B-6, B-12, C and manganese and zinc were above-adequate (P < 0.05). Low EA, low body fat and micronutrient deficiencies are common among RG.  相似文献   

16.
Physical training and competition in football markedly increase the need for macro- and micronutrient intake. This requirement can generally be met by dietary management without the need for dietary supplements. In fact, the efficacy of most supplements available on the market is unproven. In addition, players must be cautious of inadequate product labelling and supplement impurities that may cause a positive drug test. Nonetheless, a number of dietary supplements may beneficially affect football performance. A high endurance capacity is a prerequisite for optimal match performance, particularly if extra time is played. In this context, the potential of low-dose caffeine ingestion (2 - 5 mg . kg body mass(-1)) to enhance endurance performance is well established. However, in the case of football, care must be taken not to overdose because visual information processing might be impaired. Scoring and preventing goals as a rule requires production of high power output. Dietary creatine supplementation (loading dose: 15 - 20 g . day(-1), 4 - 5 days; maintenance dose: 2 - 5 g g . day(-1)) has been found to increase muscle power output, especially during intermittent sprint exercises. Furthermore, creatine intake can augment muscle adaptations to resistance training. Team success and performance also depend on player availability, and thus injury prevention and health maintenance. Glucosamine or chondroitin may be useful in the treatment of joint pain and osteoarthritis, but there is no evidence to support the view that the administration of these supplements will be preventative. Ephedra-containing weight-loss cocktails should certainly be avoided due to reported adverse health effects and positive doping outcomes. Finally, the efficacy of antioxidant or vitamin C intake in excess of the normal recommended dietary dose is equivocal. Responses to dietary supplements can vary substantially between individuals, and therefore the ingestion of any supplement must be assessed in training before being used in competition. It is recommended that dietary supplements are only used based on the advice of a qualified sports nutrition professional.  相似文献   

17.
Complex training, a combination of resistance training and plyometrics is growing in popularity, despite limited support for its efficacy. In pre- and early pubertal children, the study of complex training has been limited, and to our knowledge an examination of its effect on anaerobic performance characteristics of the upper and lower body has not been undertaken. Furthermore, the effect of detraining after complex training requires clarification. The physical characteristics (mean+/-s) of the 54 male participants in the present study were as follows: age 12.3 +/- 0.3 years, height 1.57 +/- 0.07 m, body mass 50.3 +/- 11.0 kg. Participants were randomly assigned to an experimental (n = 33) or control group (n = 21). The training, which was performed three times a week for 12 weeks, included a combination of dynamic constant external resistance and plyometrics. After training, participants completed 12 weeks of detraining. At baseline, after training and after detraining, peak and mean anaerobic power, dynamic strength and athletic performance were assessed. Twenty-six participants completed the training and none reported any training-related injury. Complex training was associated with small increases (< or =5.5%) in peak and mean power during training, followed by decreases of a similar magnitude (< or = -5.9%) during detraining (P < 0.05). No changes or minor, progressive increases (< or =1.5%) were evident in the control group (P > 0.05). In the experimental group, dynamic strength was increased by 24.3 - 71.4% (dependent on muscle group; P < 0.01), whereas growth-related changes in the control group varied from 0 to 4.4% (P > 0.05). For 40-m sprint running, basketball chest pass and vertical jump test performance, the experimental group saw a small improvement (< or =4.0%) after training followed by a decline (< or = -4.4%) towards baseline during detraining (P < 0.05), whereas the control group experienced no change (P > 0.05). In conclusion, in pre- and early pubertal boys, upper and lower body complex training is a time-effective and safe training modality that confers small improvements in anaerobic power and jumping, throwing and sprinting performance, and marked improvements in dynamic strength. However, after detraining, the benefits of complex training are lost at similar rates to other training modalities.  相似文献   

18.
The aim of this study was to characterize sprint ability, anthropometry, and lower extremity power in the US National Team Skeleton athletes. Fourteen athletes (male n = 7; mean +/- SD: height 1.794 +/- 0.063 m, body mass 81.2 +/- 3.7 kg, age 26.9 +/- 4.1 years; female n = 7; 1.642 +/- 0.055 m, 60.1 +/- 5.9 kg, 27.3 +/- 6.9 years) volunteered to participate. Sprinting ability was measured over multiple intervals using custom infrared timing gates in both an upright and a crouched sprint. The crouched sprint was performed while pushing a wheeled-simulated skeleton sled on rails on an outdoor skeleton and bobsleigh start track. Crouched skeleton sprint starts were able to achieve about 70% to 85% of the upright sprint times. The mean somatotype ratings for females were: 3.5-3.5-2.1, and males: 3.6-4.9-1.9. Lower extremity strength and power were measured via vertical jumps on a portable force platform using squat and countermovement jumps, and jumps with added mass. Jump height, power, rate offorce development and peak force were determined from force-time data. Lower extremity strength and power were strongly correlated with both upright and crouched sprint times. The results indicated that these athletes are strong sprinters with varying body structures, mostly mesomorphic, and that stronger and more powerful athletes tend to be better starters.  相似文献   

19.
We investigated the effect of an acute creatine loading (25 g per day for 4 days) and longer-term creatine supplementation (5 g of creatine or 5 g of placebo per day for 2 months) on the performance of 22 elite swimmers during maximal interval sessions. After the acute creatine loading, the mean of the average interval swim times for all swimmers (n = 22) improved (44.3 +/- 16.5 s before vs 43.7 +/- 16.3 s after supplementation; P ? 0.01). Three of the 22 swimmers did not respond positively to supplementation. After 2 months of longer term creatine supplementation or placebo,neither group showed a significant change in swimming performance (38.7 +/-13.5 s before vs 38.7 +/- 14.1 s after for the creatine group; 48.7 +/- 18.0 s before vs 48.7 +/- 18.1 s after for the placebo group). We conclude that, in elite swimmers, 4 days of acute creatine loading improves swimming performance significantly when assessed by maximal interval sessions. However, longer-term supplementation for 2 months (5 g of creatine per day) did not benefit significantly the creatine group compared with the placebo group.  相似文献   

20.
The purpose of this study was to investigate the relationship between the cable force and linear hammer speed in the hammer throw and to identify how the magnitude and direction of the cable force affects the fluctuations in linear hammer speed. Five male (height: 1.88 +/- 0.06 m; body mass: 106.23 +/- 4.83 kg) and five female (height: 1.69 +/- 0.05 m; body mass: 101.60 +/- 20.92 kg) throwers participated and were required to perform 10 throws each. The hammer's linear velocity and the cable force and its tangential component were calculated via hammer head positional data. As expected, a strong correlation was observed between decreases in the linear hammer speed and decreases in the cable force (normalised for hammer weight). A strong correlation was also found to exist between the angle by which the cable force lags the radius of rotation at its maximum (when tangential force is at its most negative) and the size of the decreases in hammer speed. These findings indicate that the most effective way to minimise the effect of the negative tangential force is to reduce the size of the lag angle.  相似文献   

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