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1.
Abstract

The study investigated different electromyographic (EMG) normalisation methods for upper-limb muscles. This assessment aimed at comparing the EMG amplitude and the reliability of EMG values obtained with each method. Eighteen male tennis players completed isometric maximal voluntary contractions and dynamic strength exercises (push-ups and chin-ups) on three separate test sessions over at least 7 days. Surface EMG activity of nine upper body muscles was recorded. For each muscle, an analysis of variance for repeated measures was used to compare maximal EMG amplitudes between test conditions. The intra-class correlation coefficient, the coefficient of variation and the standard error of measurement were calculated to determine the EMG reliability of each condition. On the basis of a compromise between maximal EMG amplitude and high reliability, the chin-ups appeared to be the optimal normalisation method for M. latissimus dorsi, M. posterior deltoid, M. biceps brachii, M. flexor carpi radialis and M. extensor carpi radialis. The push-ups seemed relevant to normalise M. anterior deltoid and M. triceps brachii activity, while isometric maximal voluntary contraction remained the most appropriate method for M. pectoralis major and M. middle deltoid. Thus, original methods are proposed to normalise EMG signal of upper-limb muscles.  相似文献   

2.
Abstract

This experiment examined muscle activation measured using electromyography (EMG) during a standardized push-up performed on stable and unstable surfaces. Fifteen highly trained participants performed four push-ups: standard (hands and feet on the floor), either the hands or feet on an unstable surface (single instability), and with both hands and feet on unstable surfaces (dual instability). Unstable surfaces were created using a stability ball and an extreme balance board. EMG activity was recorded from three core stabilizers (erector spinae, rectus abdominus and internal obliques), one prime mover (triceps), and one lower body stabilizer (soleus). The EMG time series were smoothed using a 10-point moving average and root mean squares (RMS) were calculated for the entire time series. The results showed that push-ups performed with dual instability had significantly greater EMG activation compared to single instability or the stable push-up. In addition, as instability increased, there was a greater amount of muscle activation for the core stabilizers, prime movers and lower body stabilizers. The findings are consistent with the position that unstable surfaces in conjunction with standard exercises can be used to increase activation of core trunk stabilizers. This may in turn provide increased trunk strength and greater resistance to injury.  相似文献   

3.
Abstract

The purpose of this investigation was to determine the yearly changes in body composition as well as absolute and relative isokinetic forearm flexion and extension strength of high school wrestlers. Evaluations of body composition (underwater weighing) were performed on 27 high school wrestlers prior to three consecutive seasons. In addition, isokinetic forearm flexion and extension strength values at 180°/s (Cybex II) were available for 20 of the subjects. The mean ages at the times of laboratory testing were 15.5 (± .5), 16.5 (± .5), and 17.5 (± .5) years. Repeated measures ANOVA or ANCOVA with Tukey post-hoc comparisons were used to locate significant (p<.05) differences across age for height, body weight, relative fat, body density, fat weight, fat-free weight, absolute muscular strength, and muscular strength covaried for body weight and fat-free weight. There were yearly increases in all variables except fat weight, forearm flexion covaried for fat-free weight and forearm extension covaried for fat-free weight. The results of this study indicated that the improved wrestling performance and the increase in weight classification which normally occurs during high school are, in part, a function of yearly changes in body composition and muscular strength.  相似文献   

4.
Abstract

The aim of the study was to evaluate changes in the stature, body mass, age and number of players by playing position in the first team squads of English Premiership rugby union teams from 2002 to 2011. Medical personnel at each club reported the individual data for every first team squad player. The average annual number of players included in the study was 485.2 players per season (standard deviation: 58.0). The mean stature of players in all positions increased in the period 2002 to 2011 but statistically significant trends (P < 0.01) were only observed at fly half and prop. While the mean body mass of players increased in most positions only fly half and back row players showed statistically significant (P < 0.01) upward trends. Apart from second row forwards, the average age of players in all positions decreased but this trend was only significant (P < 0.01) at prop. The numbers of registered players in every position increased but these trends were only significant (P < 0.01) at prop. English Premiership professional rugby players are generally getting taller, heavier and younger but statistically significant changes were limited to fly halves (taller and heavier), props (taller and younger) and back row forwards (heavier).  相似文献   

5.
Abstract

This experiment was undertaken to determine the effects of a six-week progressive weight training program on the development of strength and muscle hypertrophy, using one exercise, the deep-knee bend, with varying repetitions. Thirty students were chosen by random from beginning weight lifting classes at Michigan State University. Following a two-week conditioning period the subjects were divided into three groups of ten each for the controlled training period. The programs were as follows: Group A—3 sets of 9-10 repetitions, Group B—3 sets of 5-6 repetitions, and Group C—3 sets of 2-3 repetitions. Individuals in each group handled maximum weight loads for the number of repetitions each was required to perform. The effectiveness of the program was determined by three measurements: (a) thigh girth, (b) dynamic strength as measured by one RM on the deep-knee bend, and (c) static strength as measured on the dynamometer. The results were graphically analyzed and percentages calculated. The data were also statistically-treated using analysis of covariance. No significant differences were found between the three systems of training. All training procedures resulted in the improvement of static and dynamic strength.  相似文献   

6.
Abstract

The purpose of this study was to compare the perceptual response to absolute exercise intensities of individuals differing in cardiovascular fitness using both the RPE scale and a magnitude estimation procedure. Male (N = 34) and female (N = 41) subjects were classified as either high or low fit on the basis of predicted maximal oxygen uptake. Subjects cycled for two six-minute periods separated by a five-minute rest period. Following two minutes of cycling at 600 kpm ? min-1, work loads of 200, 400, 800, and 1000 kpm ? min-1 were presented in random order for one minute. The mean (± SD) perceptual exponent for the high fit women (1.33 ± .41) was significantly (p < .05) higher than that for the low fit women (1.06 ± .42). Perceptual exponents for the high (1.16 ± .45) and low (1.04 ± .39) fit men did not differ (p > .05). For both samples, RPE values did not differ significantly between high and low fit groups at any work load (p > .05). Heart rate was significantly (p < .05) higher at each work load for the low fit subjects. It was concluded that perceived exertion as measured by the RPE scale does not discriminate between groups of high and low fit subjects during short term exercise at low to moderate intensities, despite differences in cardiovascular strain.  相似文献   

7.
Abstract

Tests were made with the hand carrying weights of 0.2, 3.1, and 16.6 kg. during a 72° horizontal adductive arm swing of maximal speed timed at 12° intervals. Five practice swings and 20 trials, under each condition, were performed by 60 male subjects. Reliability coefficients were high. The first 24° of movement exhibited declining acceleration, followed by linearly increasing acceleration for the 24°—60° interval and deceleration for the next 12°. Compared with static strength in the movement position, action strength computed from acceleration was much greater with the heaviest weight and considerably less with the light weights. The correlation between static strength and speed was quite low for the normal arm swing but increased with added weight, becoming r = .76 for the heaviest. There was little correlation of individual differences in speed between different phases of movement or between movements with light and heavy weights. Specificity was high, although correlations were made for attenuation.  相似文献   

8.
Abstract

The purpose of this study was to establish criterion-referenced standards for selected tests of arm and shoulder girdle strength and endurance for college females. Several popular tests of arm and shoulder girdle strength and endurance were administered to equal numbers of trained and untrained college females (N = 92) to generate data for the analysis. The contrasting groups method (Berk, 1976; Safrit & Wood, 1990) yielded the following criterion cutoff scores that classified college females as trained or untrained on the basis of regular upper arm and shoulder girdle resistance training: pull-ups = .5 repetitions (reps), 90° push-ups = 16 reps, flexed arm hang = 5s, seated chest press = 24.5 kg, seated biceps curl = 16.4 kg, seated lat pull (latissmus dorsi pull-down) = 38.2 kg, absolute strength index = 86.4 kg, and relative strength index = .6 kg per kg of body weight. Cross-validation of the standards on an independent sample of college females (N = 112) suggested stability of the cutoff scores for pull-ups, flexed arm hang, and relative strength.  相似文献   

9.
Abstract

This study examined the influence of holding a bag with one hand on the center of foot pressure (COP) and the electromyographic responses in lower leg muscles. Thirteen healthy male adults participated in this study to keep an upright posture while holding a load with the dominant hand with four bag weight conditions (0%, 15%, 30%, and 45% of maximal voluntary contraction (MVC) of the jerk strength). Integrated Electromyography (iEMG) and mean power frequency (MPF) of EMG were calculated to estimate the degree of muscle activity and fatigue in the tibialis anterior and soleus that are involved in ankle joint control. Body sway was evaluated by the mean position of left-right (X) and front-back (Y) axis sway and the following 4 body sway factors; unit time sway factor (F1), front-back sway factor (F2), left-right sway factor (F3), high frequency band power spectrum factor (F4). When holding a bag at 45% MVC or more of the jerk strength with a single hand for one minute, muscle activity in the lower leg on the side of the bag increased markedly, and muscle fatigue was induced in the antigravity muscles of both legs. As a result, anteroposterior sway increased to a short, quick sway.  相似文献   

10.
ABSTRACT

The purpose of the study was to assess factors that contribute to countermovement jump (CMJ) performance in women’s basketball athletes. Thirteen female athletes participated and were tested for maximal oxygen uptake (VO2max) and heart rate (HRmax). Athletes were monitored, daily for a total of 21 weeks with heart rate-based wearable devices and CMJ performance and body weight were tested weekly after one day of recovery. 3-jump average height (CMJavg), maximum height jump (CMJmax), and CMJ power (Watts) were calculated and recorded. Playing intensities >85% HRmax, HRavg, HRmax and training load were averaged for three consecutive days prior to the recovery day. After the season, data was grouped as changes in CMJ power from week one: Large (≤ ?4.39% change), Moderate (?4.4% to ?0.62% change), and Minimal (≥ ?0.61% change) changes. Fixed-effects models revealed a main effect of group (p ≤ 0.05) for CMJavg, CMJmax, VO2max, weekly percent changes in body weight and for 3-day training load, HRavg, and playing time at >85% HRmax. When athletes experienced minimal changes in CMJ performance, relative to large changes, they produced greater power, jumped higher, avoided negative changes in weekly body weight, had a greater preseason VO2max and 3-day average workloads appeared to have an impact on CMJ performance  相似文献   

11.
Abstract

Percent body fat, ratings of perceived exertion and maximal oxygen consumption during a continuous running treadmill test were obtained on 127 high school female cross country runners. These young runners (x 15.6 yrs) were running approximately 25 miles per week at the time of testing. They had an average [Vdot]O2 max of 50.8 ml · min-1 and an HR max of 198.0 bpm. The mean percent body fat, as determined from hydrostatic weighing, was 15.4%. The onset of metabolic acidosis was estimated to occur at 78% of [Vdot]O2 max. A stepwise multiple regression with the 3000 meter run as the dependent variable indicated that max treadmill run time, weight relative [Vdot]O2 max and [Vdot] max entered the equation in that order, yielding an R of 0.67. Both HR and RPE increased with work intensity, but not at equal rates. These high school female runners had higher [Vdot]O2 max's than previously reported for this age group; however, they were considerably below these values reported for national caliber distance runners.  相似文献   

12.
Abstract

The present study examined the relative importance of body size and composition as determinants of individual differences in isokinetic leg extensor strength in young adult males performing at slow, moderate, and fast speeds. The subjects were 31 males between the ages of 19 and 29 years, who were not participating in weight training programs. Low to moderate correlations were found between isokinetic strength and body size or body composition measurements. At each speed, similar proportions of the variance in peak torque values were accounted for by lean body weight (23-30%) and thigh volume (20-37%). However, body weight, often suggested as the best reference standard for equalizing strength scores, also accounted for only 13-24% of the variance in peak torque values at each of the speeds tested. The moderate correlations reported in this study do not support the use of body size and composition measurements as a means of adjusting strength values.  相似文献   

13.
ABSTRACT

Exercise at different cadences might serve as potential stimulus for functional adaptations of the brain, because cortical activation is sensitive to frequency of movement. Therefore, we investigated the effects of high (HCT) and low cadence training (LCT) on brain cortical activity during exercise as well as endurance performance.

Cyclists were randomly assigned to low and high cadence training. Over the 4-week training period, participants performed 4 h of basic endurance training as well as four additional cadence-specific exercise sessions, 60 min weekly. At baseline and after 4 weeks, participants completed an incremental exercise test with spirometry and exercise at constant load with registration of electroencephalogram (EEG).

Compared with LCT, a greater increase of frontal alpha/beta ratio was confirmed in HCT. This was based on a lower level of beta activity during exercise. Both groups showed similar improvements in maximal oxygen consumption and power at the individual anaerobic threshold.

Whereas HCT and LCT elicit similar benefits on aerobic performance, cycling at high pedalling frequencies enables participants to perform an exercise bout with less cortical activation.  相似文献   

14.
Purpose: The purpose of this study was to determine magnitudes of differences for anthropometric and athletic performance scores between high school and elite college-level American football players. Method: Participants included high school-age (n = 3,666) athletes who participated in American football combines, as well as elite college-level (n = 5,537) athletes who participated in the National Football League (NFL) scouting combine. Combine data included position; height; weight; 10-, 20-, and 40-yard dash; pro-agility (PA); L-cone drill (LC); vertical jump (VJ); and broad jump (BJ). Athletes were separated into their respective position group, defensive back (DB), wide receiver (WR), linebacker (LB), quarterback (QB), running back (RB), tight end (TE), defensive line (DL), and offensive line (OL) for analysis of performance differences. Percent differences for each dependent variable were calculated to quantify magnitudes of differences. Results: NFL combine participants scored 3% to 25% better on all measurements, with the largest differences between weight and VJ (14%–25%). Conclusion: The largest measurement-specific differences between high school-age and elite college-level American football players were body size and power. Although it may seem intuitive that elite college-level players would perform better, these data provide a unique perspective to high school players, parents, and coaches, giving new information to use when designing measurement-specific athletic development programs. Thus, strength and conditioning professionals may benefit from emphasizing increases in muscle mass and power output in strength and conditioning programs.  相似文献   

15.
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16.
Abstract

This study investigated the interaction between emotion-eliciting pictures and power output during a repetitive supra-maximal task on a cycle ergometre. Twelve male participants (mean (±SD) age, height and weight: 28.58 ± 3.23 years, 1.78 ± 0.05 m and 82.41 ± 13.29 kg) performed 5 repeated sprint tests on a cycle ergometre in front of neutral, pleasant or unpleasant pictures. For each sprint, mechanical (peak power and work), physiological (heart rate) and perceptual (affective load) indices were analysed. Affective load was calculated from the ratings of perceived exertion, which reflected the amount of pleasant and unpleasant responses experienced during exercise. The results showed that peak power, work and heart rate values were significantly lower (P < 0.05) for unpleasant pictures (9.18 ± 0.20 W ? kg?1; 47.69 ± 1.08 J ? kg?1; 152 ± 4 bpm) when compared with pleasant ones (9.50 ± 0.20 W ? kg?1; 50.11 ± 0.11 J ? kg?1; 156 ± 3 bpm). Furthermore, the affective load was found to be similar for the pleasant and unpleasant sessions. All together, these results suggested that the ability to produce maximal power output depended on whether the emotional context was pleasant or unpleasant. The fact that the power output was lower in the unpleasant versus pleasant session could reflect a regulatory process aimed at maintaining a similar level of affective load for both sessions.  相似文献   

17.
Purpose: An advanced system for the assessment of climbing-specific performance was developed and used to: (a) investigate the effect of arm fixation (AF) on construct validity evidence and reliability of climbing-specific finger-strength measurement; (b) assess reliability of finger-strength and endurance measurements; and (c) evaluate the relationship between finger flexor all-out test scores and climbing ability. Methods: To determine the effect of AF, 22 male climbers performed 2 maximal strength and all-out tests with AF (shoulder and elbow flexed at 90°) and without AF (shoulder flexed at 180° and elbow fully extended). To determine reliability, 9 male climbers completed 2 maximal strength tests with and without AF and an all-out and intermittent test without AF. Results: The maximal strength test without AF more strongly determined climbing ability than the test with AF (r2 = .48 and r2 = .42 for sport climbing; r2 = .66 and r2 = .42 for bouldering, respectively). Force and time variables were highly reliable; the rate of force development and fatigue index had moderate and low reliability. The maximal strength test with AF provided slightly higher reliability than without AF (intraclass correlation coefficient [ICC] = 0.94, ICC = 0.88, respectively). However, smaller maximal forces were achieved during AF (484 ± 112 N) than without AF (546 ± 132 N). All-out test average force had sufficiently high reliability (ICC = 0.92) and a relationship to sport climbing (r2 = .42) and bouldering ability (r2 = .58). Conclusion: Finger strength and endurance measurements provided sufficient construct validity evidence and high reliability for time and force parameters. Arm fixation provides more reliable results; however, the position without AF is recommended as it is more related to climbing ability.  相似文献   

18.
目的:探讨不同快速降体重量对肌肉功能的影响;方法:以12名健康男生为实验对象,测定脱水前(0%bw l)、桑拿脱水快速降体重2%(2%bw l)、桑拿脱水快速降体重4%(4%bw l)这3种不同体重状态下最大等速肌力、等速肌耐力与无氧作功能力;在测定无氧作功能力时,结合运用主观用力程度等级评价量表(RPE),对肌肉功能进行系统评价;结果:1)2%bw l和4%bw l对肌肉的最大等速力量均没有削弱作用;2%bw l后,屈肘肌群的最大等速肌力反而增大。2)2%bw l对屈、伸肘肌群以及屈、伸膝肌群的等速肌耐力均没有影响;4%bw l后,屈肘肌群与屈、伸膝肌群的等速肌耐力不变,而伸肘肌群的等速肌耐力显著性下降。3)2%bw l和4%bw l对下肢的无氧耐力没有削弱作用。  相似文献   

19.
Inspiratory muscle fatigue may occur in as little as 6 min during high-intensity spontaneously breathing exercise. The aims of this study were to determine whether inspiratory muscle fatigue occurs during swimming exercise and whether inspiratory muscle strength differs between the supine and standing body positions. Seven competitive swimmers were recruited to perform a single 200 m front-crawl swim, corresponding to 90-95% of race pace. Inspiratory muscle strength was measured at residual volume using a hand-held mouth pressure meter that measured maximal inspiratory pressure in the upright and supine positions. At baseline, maximal inspiratory pressure in the supine position was significantly lower than maximal inspiratory pressure in the upright position (112 +/- 20.4 and 133 +/- 16.7 cmH2O, respectively; P < or = 0.01). Post-exercise maximal inspiratory pressure in the supine position (80 +/- 15.7 cmH2O) was significantly lower than baseline maximal inspiratory pressure in the supine position (P < or = 0.01). The results indicate that a single 200 m front-crawl swim corresponding to 90-95% of race pace was sufficient to induce inspiratory muscle fatigue in less than 2.7 min. Furthermore, although diaphragm muscle length is optimized when supine, our results indicate that the force output of the diaphragm and inspiratory accessory muscles is greater when upright than when supine.  相似文献   

20.
Abstract

Two groups of 23 junior high school boys were tested before and after an eight weeks' progressive resistance training program. The experimental group participated in this program, but the control group took part only in regularly scheduled physical education classes. At the end of the eight weeks, it was found that the experimental group increased their ability to do pull-ups, push-ups, the Harvard Step Test, Dodge run, the Burpee test, and trunk extension and flexion. The control group improved in the Dodge run, the Burpee test, push-ups, and trunk extension. In no case did the improvement of the control group exceed the improvement of the experimental group. The experimental group also increased in anthropometric measurements. Medical examinations indicated that no harmful effects were experienced by either group.  相似文献   

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