Date of Award

2003

Document Type

Scholarly Project

Degree Name

Master of Physical Therapy (MPT)

Department

Physical Therapy

First Advisor

Thomas Mohr

Keywords

Muscles -- physiology

Abstract

Numerous studies have been done on the Plyo Press, with focus on the concentric phase of the exercise. However, for athletes eccentric training has always been a topic of interest. Most leg press machines have a concentric and an eccentric phase involved with the exercise. However, during the eccentric phase of the leg press the muscles are underloaded because of the force-velocity relationship of the human skeletal muscle and the fact that eccentric contractions require fewer motor units for the same force and workload. This means that the leg press exercise is limited by the concentric phase. A new machine called the Agaton Max Series Leg Press takes this into consideration by being able to overload the eccentric phase of the exercise. The purpose of this study was to study the muscle activity in the back and lower extremities during both a jump on the Plyo Press and a leg press on the Agaton Max Series Leg Press. EMG analysis was performed on selected trunk and lower extremity muscles in order to provide information on the muscle activity and recruitment pattern evoked by the Plyo Jump compared to the Agaton.

Thirteen healthy male subjects performed an exercise at 100% of their body weight on the Plyo Press, which was used as the dynamic baseline. The subjects performed three repetitions of a Plyo Jump and a leg press on the Agaton, both at 80% of their 1 RM. In addition, the eccentric phase of the Agaton was loaded at 200% of the concentric phase. These results were then analyzed using normalized EMG and motion analysis, and then compared using statistical analysis.

The results of this study showed a significant difference in EMG activity on the Plyo Jump as compared to the Agaton. The results also showed a significant difference in EMG activity between the concentric and eccentric phases on the Agaton, with the concentric phase producing more EMG activity. The results appeared to show advantages of training on the Plyo Jump and the Agaton, specifically incorporating eccentric muscle contractions.

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