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Indexed/Abstracted in: BIOSIS Previews, EMBASE, Scopus, Emerging Sources Citation Index
Online ISSN 1827-1812
Kato M. 1, Wakita H. 2, Yagi N. 2, Ikegami Y. 3, Yabe K. 4
1 Department of Health and Nutrition, Yonezawa Women’s Junior College of Yamagata Prefecture, Yamagata, Japan;
2 Department of Health and Physical Education Physical Education, Faculty of Education, Mie University, Mie, Japan;
3 Research Center of Health, Physical Fitness and Sports, Nagoya University, Furocho, Aichi, Japan;
4 Osaka University of Health and Sport Science, Osaka, Japan
Aim. The maximum voluntary contraction (MVC) changes by psychological factors. The shout is one that causes a psychological change. As for the influence of the shouting effects on MVC, isometric contraction has been used. However when it assumed the adjustment of some sports situation, it is interesting to examine the shouting effect on various contraction types. In the present study, we investigated the shouting effect on maximal voluntary strength in concentric, isometric and eccentric contractions.
Methods. Fifteen health male subjects tested maximal voluntary knee extension strength in concentric (60deg/sec.), isometric and eccentric (60deg/sec.). Each muscle contraction type was done on two conditions (SC: shouting condition and NSC: non shouting condition). The EMG activities of m. rectus femoris (RF) and m. obliquus externus abd (OE) were measured by mean of bipolar surface electrodes.
Results. In SC, MVC has increased significantly in all muscle contraction type and this effect was greater in dynamic muscle contractions than in static muscle contraction. Additionally, shout was enhanced the rate of increase of muscle strength in the isometric contraction. RF and OE EMG activity were significantly increased in SC than NCS.
Conclusion. These results suggest that the shout is the effective method for elevating MVC. This mechanism would be caused by enhancement of agonist muscle activity, such as increasing the firing rate of motor neurons and increasing the recruitment of fast type motor unit. Furthermore, the enhancement of trunk stabilization by increased OE muscle activity might also contribute to the increase of MVC.