Study Of Validity Of Lower Work-load as Weight Training Exercisse From Viewpoints Of Energy Dynamics Usingnirs And Emg Methods

Introduction
Weight training for increasing the volume of muscular mass and power output, in general, is performed by using higher
work-load, which is mainly required anaerobic energy. Using the higher work-load during weight training has to pay
some attentions keeping a safety, especially for elderly and/or low fitness persons. However, there are little reports
concerning the threshold of the lower exercise intensity for getting the effects of weight training. The purpose of this
study was to examine the lower threshold of work-load for getting the effects of weight training from viewpoints of
muscular energy dynamic during various exercise intensities using NIRS and EMG methods.

Methods
Thirteen male subjects(aged:22±3yrs)participated in this study. They performed 2 different modes of the elbow flexor
and extensor curl exercise with the tempo of 15 times/min of repeated number. One mode of exercise was the
continuously incremental curl exercise with the increase of 10% of MVC (Maximal Voluntary Contraction), of workload
every minute until exhaustion. Another one mode of exercise was to perform the three constant work-load of curl
exercises, 30, 50, 70% of MVC, 4 min duration of each exercise with sufficient resting periods. They were measured
the oxy-Hb and deoxy-Hb relative concentrations and EMG signals from biceps muscle during the exercise by NIRS
and EMG methods, respectively. Energy dynamics in muscle tissue and integrated EMG were calculated.

Results
The oxy-Hb showed decreasing, and deoxy-Hb showed increasing with the increase of exercise intensity. These were
significant differences between 10% of MVC and the other intensities, but no significant differences between the
intensities more than 20% of MVC (Table 1). The changes in oxy-Hb and deoxy-Hb during constant work-load
exercise showed the similar changes as the results of the continuously incremental test (Table 2). The relationship
between oxy and deoxy-Hb and work-load was clarified non-linear relation from both experiments. The integrated
EMG showed to increase the increase with in work-loads.

Discussion / Conclusion
These results suggested that the threshold of energy dynamic from aerobic to anaerobic pathway in muscle might exit in
the lower work-load, and it might be available for weight training workload.

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