A comparison of muscle activity and 1-RM strength of three chest-press exercises with different stability requirements

Abstract

The purpose of this study was to compare one-repetition maximum (1-RM) and muscle activity in three chest-press exercises with different stability requirements (Smith machine, barbell, and dumbbells). Twelve healthy, resistance-trained males (age 22.7 ± 1.7 years, body mass 78.6 ± 7.6 kg, stature 1.80 ± 0.06 m) were tested for 1-RM of the three chest-press exercises in counterbalanced order with 3–5 days of rest between the exercises. One-repetition maximum and electromyographic activity of the pectoralis major, deltoid anterior, biceps, and triceps brachii were recorded in the exercises. The dumbbell load was 14% less than that for the Smith machine (P ≤ 0.001, effect size [ES] = 1.05) and 17% less than that for the barbell (P ≤ 0.001, ES = 1.11). The barbell load was ～3% higher than that for the Smith machine (P = 0.016, ES = 0.18). Electrical activity in the pectoralis major and anterior deltoid did not differ during the lifts. Electrical activity in the biceps brachii increased with stability requirements (i.e. Smith machine <barbell <dumbbells; P ≤ 0.005; ES = 0.57, 1.46, and 2.00, respectively), while triceps brachii activity was reduced using dumbbells versus barbell (P = 0.007, ES = 0.73) and dumbbells versus Smith machine (P = 0.003, ES = 0.62). In conclusion, high stability requirements in the chest press (dumbbells) result in similar (pectoralis major and anterior deltoid), lower (triceps brachii) or higher (biceps brachii) muscle activity. These findings have implications for athletic training and rehabilitation.     

Agonist and Antagonist Muscle EMG Activity Pattern Changes with Skill Acquisition

Abstract

The purpose of this research was to investigate the modifications in the control of the biceps brachii (agonist) and triceps brachii (antagonist) muscles during the learning of two elbow flexion tasks in sixteen college-age women. A positioning and a coincidence task were each performed at 40° and 200° per second angular velocity while bipolar surface electrodes recorded the electromyographic (EMG) activity of the muscles involved. Data on the EMG activity, angular kinematics, and timing and angular displacement error were quantified and subjected to statistical analyses. The results of the error analyses indicated that subjects did learn the various tasks over the 120 trials. Because there were no significant changes in the angular velocity patterns over trials, the EMG activity modifications are suggested to reflect differences in the control of the muscles monitored during the movements. In addition, EMG activity pattern modifications which occurred in discrete portions of the movements in both muscles indicate an increased cocontraction of the opposing muscles as subjects learned the tasks. Temporal periods in which modifications were observed appear to represent the critical periods in each movement task.     

Influence of wheel size on muscle activity and tri-axial accelerations during cross-country mountain biking

ABSTRACT

This study aimed to investigate the influence of different mountain bike wheel diameters on muscle activity and whether larger diameter wheels attenuate muscle vibrations during cross-country riding. Nine male competitive mountain bikers (age 34.7 ± 10.7 years; stature 177.7 ± 5.6 cm; body mass 73.2 ± 8.6 kg) participated in the study. Riders performed one lap at race pace on 26, 27.5 and 29 inch wheeled mountain bikes. sEMG and acceleration (RMS) were recorded for the full lap and during ascent and descent phases at the gastrocnemius, vastus lateralis, biceps brachii and triceps brachii. No significant main effects were found by wheel size for each of the four muscle groups for sEMG or acceleration during the full lap and for ascent and descent (P > .05). When data were analysed between muscle groups, significant differences were found between biceps brachii and triceps brachii (P < .05) for all wheel sizes and all phases of the lap with the exception of for the 26 inch wheel during the descent. Findings suggest wheel diameter has no influence on muscle activity and vibration during mountain biking. However, more activity was observed in the biceps brachii during 26 inch wheel descending. This is possibly due to an increased need to manoeuvre the front wheel over obstacles.     

Reliability of EMG normalisation methods for upper-limb muscles

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.     

Evaluation of mean power spectral frequency of EMG signal during 100 metre crawl

Abstract

The aim of our study was to compare mean frequency (MNF) decrease in some upper body muscles during a 100-metre all-out crawl by using two different normalization methods: firstly, when MNF at the end of swimming (MNF_Send) was normalized with respect to its initial value at the beginning and expressed with a fatigue index (FI) labelled FI_start, and secondly when MNF_min was used to calculate FI_min. MNF_min presented the lowest MNF obtained during isometric contractions until exhaustion executed on land after swimming for each of three observed muscles – triceps brachii (TB), latissimus dorsi (LD) and pectoralis major (PM). Eleven experienced swimmers participated in the study and surface electromyography (EMG) signals from TB, the upper and lower parts of LD (LD1 and LD2 respectively) and the upper and lower parts of PM (PM1 and PM2 respectively) were recorded during both swimming and isometric contractions. Results showed no differences in FI_start; however, when FI_min values were compared differences between the muscles were found (P<0.05). The triceps brachii (TB) and the upper part of the latissimus dorsi muscles (LD1) showed the lowest FI_min (40.0±15.7 and 40.7±24.4 respectively), which implied that MNF_Send obtained from these muscles most closely approached their respective MNF_min values during swimming. This might suggest that these muscles fatigued more than other observed muscles. The use of a different type of muscle contraction for calculating FI_min (isometric versus dynamic) might represent a drawback to our study, but this approach could be acceptable when between-muscle comparisons are made.     

Gender,age, and sport differences in relative age effects among US Masters swimming and track and field athletes

Abstract

The aim of the present study was to examine elbow joint extension power-load characteristics with and without a countermovement. Eight male participants performed maximal elbow extensions with and without a countermovement against different loads (0, 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0 kg). Electromyographic activity of the lateral and long heads of the triceps brachii and the biceps brachii muscles was recorded. The average joint power in the concentric phase was significantly enhanced in the countermovement condition at all loads except for 0 kg. The optimal load for the maximal joint power was greater in the countermovement (7.5 kg) than in the no countermovement condition (5.0 kg). Electromyographic activity was unchanged over the intensities and conditions. Our results suggest that the optimal load for the maximal joint power depends on the type of action (i.e. with or without a counter-movement), and that the enhanced joint power in the countermovement condition is due primarily to the storage and utilization of elastic energy.     

Effects of Food Supplement on the Performance of Selected Gross Motor Tests

Abstract

The purpose of this investigation was to study the effect of a well-advertised vitamin-mineral supplement on three selected gross motor tests. Experimental and control groups were formed in two groups, football players and physical education majors. Measurements were taken at five different time periods covering a period of 12 weeks. No statistically significant differences in motor performance were found between those subjects taking the supplement and those taking the placebo.     

Effect of warm-up exercise on delayed-onset muscle soreness

Abstract

In this study, we wished to determine whether a warm-up exercise consisting of 100 submaximal concentric contractions would attenuate delayed-onset muscle soreness and decreases in muscle strength associated with eccentric exercise-induced muscle damage. Ten male students performed two bouts of an elbow flexor exercise consisting of 12 maximal eccentric contractions with a warm-up exercise for one arm (warm-up) and without warm-up for the other arm (control) in a randomized, counterbalanced order separated by 4 weeks. Muscle temperature of the biceps brachii prior to the exercise was compared between the arms, and muscle activity of the biceps brachii during the exercise was assessed by surface integral electromyogram (iEMG). Changes in visual analogue scale for muscle soreness and maximal voluntary isometric contraction strength (MVC) of the elbow flexors were assessed before, immediately after, and every 24 h for 5 days following exercise, and compared between the warm-up and control conditions by a two-way repeated-measures analysis of variance. The pre-exercise biceps brachii muscle temperature was significantly (P<0.01) higher for the warm-up (35.8±0.2°C) than the control condition (34.4±0.2°C), but no significant differences in iEMG and torque produced during exercise were evident between conditions. Changes in muscle soreness and MVC were not significantly different between conditions, although these variables showed significant (P<0.05) changes over time. It was concluded that the warm-up exercise was not effective in mitigating delayed-onset muscle soreness and loss of muscle strength following maximal eccentric exercise.     

Anthropometrics and electromyography as predictors for maximal voluntary isometric arm strength

BackgroundMuscular strength can be conceptually determined by two components: muscle activation and size. Muscle activation by the central nervous system can be measured by surface electromyography (sEMG). Muscular size reflects the amount of contractile protein within a skeletal muscle and can be estimated by anthropometric measurements. The purpose of this study was to determine the relative contributions of size parameters and muscle activation to the prediction of maximal voluntary isometric elbow flexion strength.MethodsA series of anthropometric measurements were taken from 96 participants. Torque and root-mean-square (RMS) of the sEMG from the biceps brachii were averaged across three maximal voluntary isometric contractions. A multiple linear regression analysis was performed based on a Pearson's correlation matrix.ResultsBody weight (BW) accounted for 39.1% and 27.3% in males and females, respectively, and was the strongest predictor of strength for males. Forearm length (L3) was the strongest predictor of strength in females (partial R² = 0.391). Elbow circumference (ELB) accounted for a significant (p < 0.05) amount of variance in males but not females. The addition of sEMG RMS as a third variable accounted for an average of 10.1% of the variance excluding the equation of BW and L3 in females. The strongest prediction equation included BW, L3, and ELB accounting for 55.6% and 58.5% of the variance in males and females, respectively.ConclusionAnthropometrics provide a strong prediction equation for the estimation of isometric elbow flexion strength. Muscle activation, as measured by sEMG activity, accounted for a significant (p < 0.05) amount of variance in most prediction equations, however, its contribution was comparable to an additional anthropometric variable.     

Relationship between Motor Performance and Arousal

Abstract

Forty male subjects were tested on a motor learning task called a stabilometer. Skin conductance was taken prior to the introduction of the task and immediately after each of the learning trials. Subjects were then dichotomized on the basis of initial conductance, final conductance, total change in conductance, conductance after trial one, and changes in conductance from rest to trial one. There was no difference in performance between groups when subjects were divided on the basis of initial conductance, but for all other measures performance was significantly better for the group with higher conductance. These results lend support to the concept of an arousal continuum as proposed by Duffy and Malmo.     

Effect of Strenuous Physical Activity upon Reaction Time

Abstract

This study was concerned with the effect of bench-stepping in the Harvard Step Test upon finger and foot reaction time and, secondarily, with ascertaining the relationship, if any, between these reaction times and scores on the Harvard Step Test. The subjects were university freshman males. Reaction times were taken before, immediately after, and four minutes after the stepping exercise for 80 subjects. Thirty-six subjects served as controls, involving the reaction times and pulse counts at the prescribed intervals but without exercise. The findings failed to divulge any discernible effect of stepping exercise upon reaction time, or any apparent relationship between reaction time and the sum of the recovery pulse counts following the exercise. In view of these findings it is suggested that study be directed to two related aspects — the effect of exercise to exhaustion on reaction time, and the effect of strenuous and exhaustive exercise upon speed of movement.     

A comparison of muscle activity and 1-RM strength of three chest-press exercises with different stability requirements

The purpose of this study was to compare one-repetition maximum (1-RM) and muscle activity in three chest-press exercises with different stability requirements (Smith machine, barbell, and dumbbells). Twelve healthy, resistance-trained males (age 22.7 ± 1.7 years, body mass 78.6 ± 7.6 kg, stature 1.80 ± 0.06 m) were tested for 1-RM of the three chest-press exercises in counterbalanced order with 3-5 days of rest between the exercises. One-repetition maximum and electromyographic activity of the pectoralis major, deltoid anterior, biceps, and triceps brachii were recorded in the exercises. The dumbbell load was 14% less than that for the Smith machine (P ≤ 0.001, effect size [ES] = 1.05) and 17% less than that for the barbell (P ≤ 0.001, ES = 1.11). The barbell load was ～3% higher than that for the Smith machine (P = 0.016, ES = 0.18). Electrical activity in the pectoralis major and anterior deltoid did not differ during the lifts. Electrical activity in the biceps brachii increased with stability requirements (i.e. Smith machine 相似文献   

The Measurement of Postures

Abstract

Thirty-three college men doing the toe-touch test were used as subjects to ascertain the relative contribution of the back and hamstring muscles to hip joint flexibility. The subjects, performing six tests over a 5-week period, were photographed during each of their tests. Anthropometric measurements were taken prior to testing to determine if there was any relationship to flexibility. Making use of concentric circles and marking reference points on the subject prior to testing, it was possible to ascertain the curvature of the back, the angle of straight back flexibility, and the angle of bent back flexibility.

Results indicate that the extensibility of the hamstring muscles appeared to be one of the main contributing factors to hip joint flexion, and since the warm-up did not affect the flexibility of the back, one might conclude that the back made no increased contribution to hip joint flexion, as measured in this study. There was no significant relationship to the angle of bent back flexibility.     

Fatigue effects upon sticking region and electromyography in a six-repetition maximum bench press

Abstract

The aim of the study was to examine the sticking region and concomitant neuromuscular activation of the prime movers during six-repetition maximum (RM) bench pressing. We hypothesised that both peak velocities would decrease and that the electromyography (EMG) of the prime movers (deltoid, major pectoralis and triceps) would increase during the pre-sticking and sticking region during the six repetitions due to fatigue. Thirteen resistance-trained males (age 22.8 ± 2.2 years, stature 1.82 ± 0.06 m, body mass 83.4 ± 7.6 kg) performed 6-RM bench presses. Barbell kinematics and EMG activity of pectoralis major, deltoid anterior, and triceps brachii during the pre-, sticking and post-sticking region of each repetition in a 6-RM bench press were analysed. For both the sticking as the post-sticking region, the time increased significantly from the first to the sixth repetition. Vertical barbell height at the start of sticking region was lower, while the height at the end of the sticking region and post-sticking region did not change during the six repetitions. It was concluded that in 6-RM bench pressing performance, the sticking region is a poor mechanical force region due to the unchanged barbell height at the end of the sticking region. Furthermore, when fatigue occurs, the pectoralis and the deltoid muscles are responsible for surpassing the sticking region as indicated by their increased activity during the pre- and sticking region during the six-repetitions bench press.     

Relationship between the Perception and Reproduction of Body Postures

Abstract

One hundred and seven college women were tested in their ability to recognize a demonstrated body posture from among similar ones and to reproduce demonstrated body postures. Two original tests were devised for this purpose. A low but statistically significant correlation (- .34) was found between the two. In addition, the subjects completed a questionnaire regarding the extent and nature of their motor experience. The extent of the individual's motor experience had a significant role in each of these abilities. The direction to be taken in reproducing the postures was found to be a complicating factor.     

A New Perspective on Motor Skill Automation

Abstract

The article by Richard A. Schmidt is directed to the locus of movement control. The paper's major goal is to describe a reconciliation between the peripheralists and the centralists. Schmidt describes major research issues for the future, along with current thinking about the central control of action in various theoretical conceptualizations of the structure of central motor programs. In the presentation on motor skill automation George E. Stelmach and Douglas D. Larish introduce the concept of attention and review research findings concerning attention, automation, and movement. They recommend automatic sequencing as a more viable theoretical position. Empirical support is given for the stance taken by these authors, followed by examples of potential approaches to research in motor behavior.     

Relationships among peak power output,peak bar velocity,and mechanomyographic amplitude during the free-weight bench press exercise

Abstract

The purpose of this study was to examine the relationships among mechanomyographic (MMG) amplitude, power output, and bar velocity during the free-weight bench press exercise. Twenty-one resistance-trained men [one-repetition maximum (1-RM) bench press = 125.4 ± 18.4 kg] performed bench press muscle actions as explosively as possible from 10% to 90% of the 1-RM while peak power output and peak bar velocity were assessed with a TENDO Weightlifting Analyzer. During each muscle action, surface MMG signals were detected from the right and left pectoralis major and triceps brachii, and the concentric portion of the range of motion was selected for analysis. Results indicated that power output increased from 10% to 50% 1-RM, followed by decreases from 50% to 90% 1-RM, but MMG amplitude for each of the muscles increased from 10 to 80%1-RM. The results of this study indicate that during the free-weight bench press exercise, MMG amplitude was not related to power output, but was inversely related to bar velocity and directly related to the external load being lifted. In future research, coaches and sport scientists may be able to estimate force/torque production from individual muscles during multi-joint, dynamic constant external resistance muscle actions.     

Learning from the Experts: Practice Activities of Expert Decision Makers in Sport

Abstract

This study was an experimental investigation of the emotional responses of boys 9 through 15 years of age to highly organized competitive baseball. The subjects were 75 boys who participated in Little League Baseball, 50 boys who were members of Middle League teams, and 80 boys who did not play on an organized team.

The Galvanic Skin Response test was employed to measure the emotional changes of boys participating in league baseball and to compare the results of these tests with those of the same boys participating in softball competition in physical education classes. Insofar as the Galvanic Skin Response test can be taken to be a valid measure of emotional excitation of boys of this age level, the results of this study suggest that youngsters were no more stimulated by competition in league games than they were by competition in physical education games.     

Effect of Strenuous and Mild Pre-Meal Exercise on Postprandial Lipemia

Abstract

An attempt was made to elucidate the mechanism whereby exercise facilitates postprandial lipid clearance. Two separate experiments examined the effects of mild and strenuous pre-meal exercise on postprandial lipemia among human male subjects. In each case, a high fat meal was consumed after a fasting blood sample was taken. Additional samples were drawn 3, 5, and 7 hr. following the meal on both a control and an experimental day. Optical density was employed as a measure of serum turbidity. Data were analyzed through analysis of variance.

Strenuous pre-meal exercise appeared to hasten postprandial lipid clearance without affecting the magnitude of lipemia. Mild pre-meal exercise was seen to reduce the magnitude and duration of postprandial lipemia. These observations tend to negate the concept that exercise influences postprandial lipemia via digestive and/or absorptive mechanisms.

It is hypothesized that gross differences in response to the high fat meal witnessed between the two experimental populations may be due to the variance in the mean ages of the groups.     

Effect of Training Program on Total Body Reaction Time of Individuals of Low Fitness

Abstract

Twenty-six low fitness subjects were tested for total body reaction time, strength, agility, and explosive power and then retested on these items seven weeks later. During the intervening six-week period, the subjects participated in a vigorous training program consisting of four 30-minute sessions per week. Statistically significant improvements were displayed in all items tested following the training program.