Author Wai-Po Tang, 2000. Webpublish Dec 2001

 

A Comparative Analysis of Myoelectric Activity Between Three Different Hand-Widths of
Press Up

 

Introduction
Press-up is a very common type of exercise in many recreational sports, and the hand positioning effects biomechanical efficiency or alters the load on specific muscles (Bartlett, 1996). These positions are comparable to bench press hand-grip width on the bar. Weightlifters need an optimal hand-width to ensure biomechanical efficiency to push maximum load. As for the novice recreational exerciser, the difficulty of the press ups may be overcome by adjusting width position of the hands. Two of the prime skeletal muscles, pectoralis major and triceps are found to substantially contribute to the motions of press-ups. McLaughlin (1985) found that wider grip involves the pectoralis more, and narrow grip involved the triceps. The contractile forces of the muscles are relative to the electrical activity within the muscles (Hamil & Knutzen, 1995).

A typical recording of electrical activity of the muscular contraction is the use of an electromyography (EMG). Action potentials of muscular activity are a result of motor unit recruitment, and the electrical impulses are measured in voltage. Skin-surface electrodes pick up the signals, and converting it via EMG into quantifiable data can obtain the measurements.

Madsen and McLaughlin (1984) used EMG to measure the effects of grip width in bench press, and found that expert lifters used wider grip than novices did. Clemon and Aron (1997) found that weightlifters using moderate grip width in bench press could lift significantly heavier load. However, these findings were contradicted by Elliot (1989), and stated that grip width was not an independent variable.

The present study's objectives were to examine the action potentials of the pectoralis major and the triceps, and to compare the myoelectrical activity between three different hand widths during press-ups.

 

Discussion
The main objectives of the present study were to investigate the myoelectrical activity in the pectoralis major and the triceps during press ups, also compare the effects of different hand-widths.

The results indicated that triceps had highest electrical activity during the narrow hand-width trials, and the pectoralis major's highest electrical activity was found during the wide hand-width trials. The experimenter noted during visual observation of the subjects performing the press ups, the narrow and wide hand-width appeared to be more strenuous. Noticeable shaking occurred among the subjects especially in the isometric phase of the press ups. This suggested that normal hand-width at 60cm was the least strenuous position, and therefore advantageous in pressing heavier load.

The findings support McLaughlin's (1985) findings that wide grip in bench press involves the pectoralis, and narrow grip involves the triceps. Also, supports Clemont and Aron (1997) argument that moderate grip width in bench press allows subjects to significantly lift heavier load. However, the present study dispute the findings of Elliot (1989) claiming that grip-width is not an independent variable in bench press.

The important consideration of hand-width position must be based on the objective of the effect of exercise. For example, a weightlifter objective is to find an optimal hand-width to lift heavier load but a bodybuilder or strength athlete may wish to elicit hypertrophy and not concerned with the amount of load lifted. Therefore, the optimal hand-width of the press ups is dependent on the objectives of the exerciser, and the method in achieving the desire results.

The methodology of the experiment was somewhat basic and extraneous variables such as elbow angles, shoulder angles and the angle of back extension were not considered. This meant that inconsistent motions affect the internal validity of the experiment. The speed of the press up motion was also inconsistent but errors were within a time period of one second. It would appear that goniometer should be introduced to measure the joint angles, an audio/visual metronome to maintain cadence, and a timer in synchronisation with the EMG and the motions.

Future investigation should implement more control, and conduct experiment on a larger population. Also, look at the inter-relationship of pectoralis and triceps in producing maximal lift or press.

The findings of the present study suggest that a beginner exerciser should initially adopt the normal hand-width (60cm), and a strength athlete should adopt various of widths depending on the desire effect. The wide hand-width works the pectoralis more, and the narrow hand-width works the triceps more. However, the weightlifter must consider the optimal hand-width in terms of motor recruitment as well as the displacement of the bar.

 

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