سوال 682677

Question

بخش8 8The pinch hand position of our study involved some opposition from the thumb similar to that with handgrip dynamometry (Figure 1). Although the pinch grip yielded the third lowest IEMG amplitude, the mean value was still significantly higher than the handgrip IEMG (169±22%). A qualitative comparison of the resistance force between handgrip dynamometry and the pinch grip employed during the climbing task reveals differences. The primary resistance forces during handgrip dynamometry are directed against flexion of the fingers and the base of the thumb. With the pinch grip there would be a resistance force, generated by the effect of gravity, acting as a shear force against the finger-hold interface. This shear force, in effect, attempts to pull the rock feature from the hand. This could demand an additional muscular force to maintain flexion of the fingers and generation of friction to oppose the shear force. Although limitations of our study prevent closer determination of the nature of handgrip dynamometry versus the use of the hand during climbing, it appears that significant differences exist. The suggestion that handgrip dynamometry may not be specific to the force requirements for climbing is supported indirectly by reported handgrip strength data for rock climbers. Previous studies have not found handgrip strength to be unusually high in expert and elite climbers (13). Watts, et al. (15) found handgrip strength in elite male and female climbers to score at the 50th and 75th percentiles, respectively, for agematched North American norms. Furthermore absolute handgrip strength was not found to be a significant predictor of climbing performance in elite competitive rock climbers (15). Newer strength measurement instruments such as that employed by Grant, et al. (4, 5) may prove useful in future study. Measurement of applied force and impulse of hold contact and release during actual climbing awaits exploration. There were limited significant differences among the different hand positions for the upward movement (Table 1). The highest IEMG amplitudes during upward movement were observed for the crimp (C) position and the smaller 2-finger (2F1) position. Climbers would consider these two grips as the most difficult positions of the six in the HIT Strip system. Likewise, the lowest IEMG amplitudes were observed for the open (O) and the larger 2-finger (2F3) configurations. These two grip positions would be rated as the least difficult of the six. Although no significant differences were found among hand positions for the downward movement, a 111 1 similar ranking, with the exception of C, was observed. Observation of responses for a larger sample of subjects may reveal more diversity among the hand positions. Still, it seems clear that, during climbing-specific training, the use of body weight alone will result in varying magnitudes of stress on the musculature dependent upon which specific grips and hand positions are employed.

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سوال 682677

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