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1.
Abstract

Three experimental groups of 45 S's each were given 30 repeated isometric wrist flexion trials. Each trial consisted of a maximal 5-sec. effort followed by a rest period of 5,10, or 20 sec. In each recuperation group S's were divided into subgroups representing high, middle, and low levels of absolute strength. The data were analyzed by an analysis of variance of trends allowing statistical tests for best fitting trend components and trend differences between subgroups. Low level of strength groups always demonstrated a fatigue pattern significantly different from high and middle levels. High and middle levels displayed similar patterns differing only on absolute level of strength. Caution isefore indicated in definition and magnitude assessment of derived curve components based upon composite fatigue curves secured on unknown levels of strength. It seems unlikely that the same factors responsible for muscular fatigue can be operating in the same manner at different levels of isometric strength.  相似文献   

2.
Abstract

Twenty-seven male subjects performed two 5-min bouts of rhythmic, isometric elbow flexion and two similar bouts of knee extension at a rate of 30 maximal contractions per min. Exponential analyses revealed that the pattern of fatigue for each limb followed a single component curve of the form: Yt = a0e ?Kot + c. An analysis of variance comparing the results from the two limbs revealed that (a) the strength scores for the leg were significantly (p < .05) higher than those for the arm throughout the exercise bouts; (b) both limbs experienced a significant strength decrement; and (c) there was significant interaction between trials and limbs. It appeared that the greater loss of strength by the knee extensors was reponsible for this interaction. It was concluded that during a rhythmic, all-out task, the rates of fatigue experienced by the two muscle groups tend to differ, with the elbow flexors fatiguing more rapidly initially but reaching a plateau at a relatively higher level than the knee extensors.  相似文献   

3.
Abstract

Plantar flexion and knee extension fatigue patterns elicited by 25 serial isometric contractions were assessed on eight female distance runners. Fiber type composition of the vastus lateralis and gastrocnemius muscles was examined by a needle biopsy technique. Two different isometric exercise regimens were administered: 10-sec contractions separated by 5-sec intertrial rest (10:5) designed to elicit a rapid rate of fatigue, and 10-sec contractions separated by 20-sec intertrial rest (10:20) designed to induce less fatigue. No fatigue pattern was found for the 10:20 regimen which was consistent with previous data on male distance runners but unlike male power athletes who did exhibit significant fatigue. Significant fatigue decrements were found for the 10:5 knee extension (55.7%) and plantar flexion (75.8%) conditions. Fiber type composition and fatigue decrements did not correlate. Knee extension and plantar flexion maximum strength correlated significantly with the amount of fatigue induced with r's of .82 and .83, respectively. For each separate muscle group, maximum isometric strength was a better predictor of fatigability than fiber type composition. Even though differences in maximal strength and muscle mass existed between knee extension and plantar flexion muscle groups, elicited fatigue curves were similar in pattern differing only in absolute level. High versus low strength classification analysis showed similar knee extension but dissimilar plantar flexion fatigue patterns. Results suggest that the role of fiber type composition, muscle mass, and maximum strength level as they influence local muscular fatigue patterns must be elucidated for each muscle group separately.  相似文献   

4.
Abstract

Muscle fiber type composition in the vastus lateralis and knee extension isometric strength fatigue patterns were assessed in eight endurance-trained and eight power-trained males. Two different 25-trial isometric contraction exercise regimens were administered: a 10-second contraction, 5-second intertrial rest condition designed to induce a fast rate of fatigue and a 10-second contraction, 20-second intertrial rest condition designed to induce a slower rate of fatigue. The power group fatigued almost four times faster than the endurance group in the 10:5 exercise condition. In the 10:20 exercise condition, the endurance group showed no fatigue pattern while the power group had a significant strength decrement of 32%. In both exercise conditions, the power group exhibited more complex fatigue patterns in terms of statistically significant trend components. Maximum isometric strength correlated positively with slow twitch (ST) percent number in power (r = .80) and endurance (r = .48) groups, but negatively with linear trend coefficients in endurance (r = -.62) and power (r = -.80) groups. Maximum isometric strength also correlated higher with fatigue curve trend coefficients than did muscle fiber type composition. Thus, a faster rate of fatigue was associated with higher maximum isometric strength and with higher ST percent number and area. Since maximum isometric strength correlated with body weight (r = .86 for groups combined), both maximum isometric strength and muscle mass appear to be more important determinants of knee extension isometric strength fatigue patterns than muscle fiber type composition.  相似文献   

5.
Abstract

Knee extension isokinetic peak torque was assessed at angular velocities of 0, 30, 180, and 240[ddot]/sec, and isokinetic endurance was assessed by 50 consecutive contractions at 180[ddot]/sec in eight college age men. Also, muscle fiber type of the vastus lateralis was determined and related to isokinetic strength and fatigability. To determine the influence of initial strength on isokinetic endurance the 50 serial isokinetic contractions were assessed after subjects performed two bicycle exercise regimens designed to affect initial strength levels. Neither isokinetic peak torques (made relative to MVC or per Kg of body weight) nor the amount of strength loss over the 50 contractions correlated with fiber type. The peak torques at 180[ddot]/sec at the start of the 50 contractions differed over the three conditions (unfatigued and after the two bicycle exercise regimens), however, the amount of of strength loss over the 50 trials was similar for the three conditions. Also, the patterns of the three isokinetic fatigue curves were remarkably similar. Thus, the initial strength level across the treatments did not affect the rate of fatigue. However, when the treatment conditions were examined separately, the amount of strength loss over the 50 trials correlated significantly with initial strength. Thus, factors other than, or in addition to, fiber type and initial strength level must influence the rate of isokinetic fatigue.  相似文献   

6.
Abstract

Two matched groups of 10 subjects each were employed to assess possible central facilitation effects over 4 weeks of training. Each of the 12 training sessions consisted of 20 trials of maximum isometric wrist flexion for 5 sec. with a 30-sec. rest period between trials. Two experimental conditions were used. On alternate sessions condition one consisted of 20 trials with odd-numbered trials being unilateral and even-numbered trials being simultaneous bilateral efforts. Condition two consisted of the first 15 trials being unilateral and the last 5 trials simultaneous bilateral. The right limb in Group I and the left limb in Group II constituted the criterion measures. Central facilitation effects due to simultaneous bilateral isometric wrist contractions were: (a) not present initially and (b) not elicited through the 4 weeks of training. The finding held for both dominant and nondominant limbs and for fatigued and nonfatigued states.  相似文献   

7.
Abstract

A study was made on the effects of a 10-sec. isometric exercise, which involved much of the large musculature, upon the heart-rate, blood pressure, and net oxygen cost. Six subjects exercised in a semireclining, fixed position against a Medart spring dynamometer. Each subject pulled to 60 percent of his previously determined maximum effort. Heart rate showed a slight increase during exercise followed by a sharp rise in the few seconds following exercise. This was followed by a drop almost to the resting level within 20 to 30 sec. following exercise. Systolic pressure rose following exercise and was highest in the period immediately following exercise, then dropped slowly to resting levels within 2 1/2 min. Oxygen consumption varied widely both between subjects and between experiments in the same subject.  相似文献   

8.
Abstract

To evaluate the effect of concurrent augmented feedback on isometric force output during familiar and unfamiliar muscle movements, 18 men and 21 women, 18 to 23 years of age, completed two isometric exercises: flexion of the thumb (a familiar muscle movement) and abduction of the fifth digit (an unfamiliar movement). The exercises consisted of 10 maximum voluntary isometric contractions lasting 10 s each and separated by 10-s intertrial rest intervals. Concurrent visual feedback was provided during alternate contractions. The order of exercises and trials for feedback was randomly assigned and balanced over subjects. Peak force output during abduction of the fifth digit was significantly (p ≤ .01) greater with (4.4 ± 0.29 kg) than without feedback (4.1 ± 0.26 kg). Feedback did not influence (p > .05) peak force output during thumb flexion (232 ±1.09 kg vs 22.5± 1.05 kg). Muscular fatigue was more pronounced during thumb flexion without feedback (18.4 ± 1.17%) than when feedback was provided (11.8 ±136%). These data suggest that fatigue may increase the effect of feedback on force generation during familiar muscular movements. To obtain maximal isometric force measures during strength testing, augmented feedback should be provided.  相似文献   

9.
Abstract

An investigation was conducted to determine the effects of fatiguing exercise upon the Achilles tendon reflex. Eleven subjects performed one of four exercise tasks on each of four separate days. The exercise conditions involved low-intensity isometric, high-intensity isometric, low-intensity isotonic or high-intensity isotonic exercise. The low-intensity tasks required a 25% MVC load, while the high-intensity conditions required a 50% MVC load. Results showed that low-intensity isometric exercise reduced reflex force, as well as the time needed to reach peak force, while high-intensity exercise produced an enhancement of reflex force. Half-relaxation time was faster after subjects executed low-intensity isometric exercise, but generally somewhat prolonged following high-intensity isometric exercise. Thus, the Achilles tendon reflex may be either enhanced or depressed depending upon the type and intensity of exercise performed.  相似文献   

10.
Abstract

The purpose of the study was to investigate the effect of a 2-min. isometric exercise training program on force and fatigue in a skeletal muscle. The subjects (N=60) were divided into two equal groups, control and experimental. The control group was tested twice, once at the beginning of the experiment and again after 20 days. The subjects in the experimental group were tested before embarked on a 20-day period of isometric training. held the tension for 2 min. in the morning and again in the afternoon. Periodic tests were on the 5th, 10th, 15th, and 20th days. Large gains of initial strength were recorded on the 5th day. Isometric training continued beyond five days produced no significant gains in initial strength althoughe was a significant increase in isometric endurance. Isometric exercise continued longer than 15 days resulted in a significant decrease in initial strength and isometric endurance.  相似文献   

11.
Abstract

The present investigation verified that strength is improved by a training programme consisting of repetitions of maximal isometric voluntary co-contractions without increasing co-activations during contractions against external resistances. Ten participants performed 12 training sessions (four sets of 6 × 4 second maximal isometric co-contraction of the elbow flexor and extensors, 3 days a week for 4 weeks). Surface electromyograms of triceps and biceps brachii were collected during maximal voluntary isometric elbow flexion and extension against a force transducer. Maximal voluntary isometric force increased significantly after training, by 13.8 ± 6.0% (extension) and 9.6 ± 9.5% (flexion), but the observed increases in EMG of agonist muscles during maximal voluntary contraction were not significant. No significant changes in the levels of co-activation of the elbow flexors and extensors were observed. No significant change was observed for all the parameters in a control group of ten participants. These results indicated that the strength improvements after co-contraction training occur without increases in co-activation level.  相似文献   

12.
Rebuttal     
Abstract

The problem of the study was to investigate the relationship between maximum strength and muscular endurance; also the relationship between maximum strength and percentage of maximum strength held before and after an extended period of isometric training. The subjects (N = 60) were divided into two equal groups, control and experimental. The experimental group was further divided into two subgroups of high and low strength. The control group was tested for maximum strength and endurance once at the beginning of the experiment and once after 20 days. The subjects in the experimental group were tested for maximum strength and endurance before they embarked on a 20-day period of isometric training. They held tension for 100 sec. in the morning and again in the afternoon. Periodic tests were on the 5th, 10th, 15th, and 20th day. There was a significant relationship between maximum strength and endurance and a negative and generally significant relationship between maximum strength and percentage of maximum strength held.  相似文献   

13.
Abstract

This study was made to determine the influence of five selected motive-incentive conditions upon the effectiveness of a 6-week isometric training program for the development of strength in the elbow flexor muscle group. Data were obtained from an initial test, from each training session, and from a final test. The mean gains in best strength scores from the initial to the final test were statistically significant (p = .05) for all five motive-incentive groups. No significant differences (p = .05) were found between the mean of the scores for the five motive inventive groups obtained during the first training session, during the last training session, from the final test, and from the cumulative scores for the 12 training sessions.  相似文献   

14.
Abstract

Twelve subjects were used to determine the effect of isotonic and isometric exercises on heart rate using a military press in a sitting position. The isotonic exercise was performed for 45 sec. with one half of maximum resistance, and the isometric exercises were performed for 45 sec, with one half, two thirds, and maximum resistance. The results indicated that isometric exercise performed for 45 sec. with one half of maximum resistance could stimulate heart rate to the same extent that isotonic exercise could, using the same intensity and duration. The results also showed that increasing the load in isometric contraction resulted in a proportional increase in heart rate and that increasing the load to maximum isometric contraction resulted in a near twofold increase in heart rate.  相似文献   

15.
Abstract

Three groups of 11 subjects enrolled in required physical education were equated on the basis of bicycling for two minutes at 14 kg. resistance. Group I did weight training, Group II used the Commander Set series of isometric contractions, and Group III participated in normal activities. At the conclusion of the 8-week experimental period all subjects were retested on the bicycle ergometer under the original conditions. Both experimental groups showed statistically significant improvements in the bicycle ergometer test and there were no statistically significant differences between the means of the differences between the initial and final scores of the two experimental groups. It is hypothesized that increases in muscular endurance may be effected by certain programs of isometric contractions as well as by isotonic exercises.  相似文献   

16.
Abstract

It is argued that previous studies of active flexibility have not achieved experimental control. An experiment then is described which achieved experimental control by using daily flexibility training over a 7-day period.

Forty-two female subjects were randomly assigned to one of six treatment groups or a control group. The six treatment groups received proprioceptive neuromuscular facilitation training for six consecutive days with isometric contraction periods of 0 sec, 3 sec, or 6 sec. Three of the treatment groups followed an active regime (concentric contraction of the agonists) and three a passive regime. All subjects were pretested for active flexibility on Day 1. They were also posttested after training on Day 6, and without training on Day 7. A two factor multivariate analysis of covariance with trend analysis on the period of isometric contraction factor indicated a significant positive linear trend for this factor, approximate F(2, 28) = 7.90, p < .002, together with a significant interaction between this linear trend and the active-passive regime factor, approximate F(2, 28) = 3.81, p < .034. Follow-up tests revealed that this interaction was due to larger gains in active flexibility being associated with longer periods of isometric contraction in the active groups, but not in the passive groups.  相似文献   

17.
Abstract

Two groups of college men (N = 41) participated for 12 weeks in two different exercise programs to determine the relative effects of unilateral isometric and isotonic contractions of equal load, duration, and range of movement on the muscular strength of the contralateral limb. Data examined by the t test for correlated means indicated that both methods of exercise produced significant increases in the strength of the unexercised limb. Application of the multiple linear regression technique for covariance analysis revealed that no significant difference existed between the effectiveness of the exercise methods.  相似文献   

18.
Abstract

In an attempt to extend the laws of fatigue to the performance of highly practiced subjects, 24 college males were trained for four days (50 trials/day) on a coincident timing task prior to manipulation of the fatigue variable. On day 5, motor performance was immediately preceded by either local fatigue (static exercise), general fatigue (treadmill running), or no fatigue. Increased variable error was found for both local and general fatigue subjects as compared with controls on the first block of five trials following fatigue. However, by block 2 this difference had diminished. A constant error analysis on the first and second postfatigue trials revealed transitory overshooting of the criterion timing response for local fatigue subjects and undershooting for general fatigue subjects. The results suggested that local and general fatigue may alter the timing mechanism in different ways and that both are sources of at least transient decrements in the performance of well-practiced subjects.  相似文献   

19.
Abstract

Relative isometric endurance tests of 50, 60, 70, and 80 percent weight loads were used to evaluate the muscular endurance of three groups of male college students. The 47 students were grouped according to level of athletic achievement. Analysis of variance models failed to detect any differences between the endurance of the three groups. Consideration was given to the use of relative endurance tests for evaluating levels of motivation.  相似文献   

20.
Abstract

This study investigated the time needed to change a motor program that specified the elbow flexor muscles to gradually increase the isometric force production from 15% to 75% of one's maximum voluntary contraction (MVC). A double-stimulation paradigm was used with the restriction that subjects (N = 12) be at 15% of their MVC before the presentation of the first stimulus. Subjects reacted to the first stimulus (randomly presented) by gradually increasing their isometric force from 15% to 75% of their MVC and then reacted to the second stimulus by altering the force production in one of four ways: (a) increasing the force to the 75% level rapidly instead of gradually, (b) discontinuing the increase and maintaining the level of force attained, (c) discontinuing all force production, or (d) reversing the direction of force so that it is produced by the elbow extensors. The data revealed that more time was needed to increase the force rapidly than to perform any of the other three conditions.  相似文献   

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