表題番号：2009B-308
日付：2010/04/06
研究課題反動動作を用いた筋パワー向上のためのトレーニング方法の確立
| 研究者所属（当時） | 資格 | 氏名 | |
|---|---|---|---|
| （代表者） | スポーツ科学学術院 | 助手 | 宮本 直和 |
- 研究成果概要
- INTRODUCTION
During the actions involving a counter-movement (CM), the tendinous tissues have been considered to play an important role in energy storage and release. However there are contradictory reports regarding the relationship between the stiffness of tendon and the extent of joint performance enhancement induced by a CM (Kubo et al. 1999, Bojsen-Møller et al. 2005). On the other hand, the extent of joint power enhancement by a CM was reported to be influenced by the load intensity against which the task was performed (Miyamoto et al. in submission). Therefore, the purpose of this study was to investigate the relation between the tendon stiffness and the CM induced enhancement of the joint power output against different loads.
METHODS
Nineteen adult participants performed maximal elbow extensions with and without a CM against different loads (0, 2.5, 5.0, 7.5, 10.0, and 12.5 kg) at their maximal effort. The increase in the average joint power by the CM during concentric phase (75-135 deg: full extension=180 deg) was defined as the CM effect for the given load. The tendon stiffness of the lateral head of the triceps brachii muscle was measured using ultrasonography during isometric ramp contraction of elbow extension. The isometric maximal muscle strength of elbow extension and the tendon stiffness were measured with elbow and shoulder joint angles of 90 deg flexed. The storage capacity of elastic energy by tendon was estimated as the integrated area below the tendon force-elongation curve during the ramp contraction. Multiple stepwise linear regression analysis was used to identify independent predictors of the CM effect at each load intensity, employing tendon stiffness, maximal strength, and storage capacity of elastic energy.
RESULTS & DISCUSSION
In both conditions with and without a CM, the average joint power varied across different load intensities, and peaked at 5.0 kg and 10.0 kg in the tasks without and with a CM condition, respectively (Fig. 1). The CM effect tended to increase with the load intensity (Fig. 1). The multiple stepwise linear regression analyses revealed that none of the variables contributed significantly to the prediction of the extent of the CM effect for the loads within 0-5.0 kg whereas the muscle strength at 7.5 kg (r=0.62, P<0.05) and the tendon stiffness at 10.0 and 12.5 kg contributed significantly to the prediction (r=0.60 and 0.67, P<0.05, respectively, Table 1). The results indicate that for the high load tasks the extent of CM effect was greater in subjects with stiffer tendon. In a CM exercise, it has been reported that short coupling time was necessary for enhancing the performance during the concentric phase (Bosco et al. 1981). The increased stiffness causes the recoiling time to shorten, enabling the tendon to transmit the muscle force to the attached bone quickly and effectively. In fact, a significant correlation was reported between the rate of isometric torque development (a key parameter of rapid muscle force exertion) and the tendon stiffness (Bojsen-Møller et al. 2005). Taken together, our results suggest that, at least in elbow extension task, for the high load intensity tendinous tissues play an important role to transmit muscle force to the bone quickly and effectively, and thereby, a stiffer tendon could lead to greater extent of joint power enhancement induced by a CM.