B-26: Free Communication/Poster – Sport Biomechanics: WEDNESDAY, JUNE 1, 2005 2:00 PM - 5:00 PM ROOM: Ryman C1
It has been suggested that the ability to maintain a specific hand-finger configuration against force generated by the effect of gravity on body mass is important in rock climbing performance. In this regard, climbers often attempt to reduce the effect of mass by using lightweight equipment and, in some cases, reducing fat weight of the body. The effects of variations in mass upon vertical ground reaction force at the point of hand contact have not been reported.
The purpose of this study was to record vertical ground reaction force at the hand during a common rock climbing movement performed with body mass and with 4.5 kg of added mass.
Eight experienced climbers volunteered as subjects. Each subject completed four trials of a climbing movement sequence on a vertical indoor wall. The specific movement sequence is known to climbers as a high-step rock-on. Climbers performed 2 trials (T1, T2) under each randomized condition of body mass (BM) and body mass plus 4.5 kg of added mass (AM). Two force platforms (FP) were imbedded into the wall flush with the climbing surface. The FP surfaces were modified to accept artificial climbing holds typical of indoor climbing venues. During the movement sequence, a point was attained at which all weight was supported by the right foot on one FP, and the right hand on the second FP. Vertical ground reaction force (FV) for the hand was recorded at 500 Hz throughout the movement. Forearm EMG was recorded at 500 Hz from surface electrodes placed 1/3 of the distance from the medial epicondyle of the humerus to the styloid process of the radius and a point 2 cm distal. EMG and force data were acquired simultaneously and matched via a common data signal. The raw EMG was integrated via root mean squared (RMS).
There were no differences in peak FV between T1 and T2 under either mass condition. Peak FV was significantly higher for AM vs BM (T1: 26.0±4.6 vs 25.1±5.2; T2: 26.5±4.4 kg vs 24.2±5.0). RMS at Peak FV did not differ between trials or between mass conditions. Vertical hand force was lower at the point of peak RMS than at peak FV (p<.05) and did not differ between AM and BM.
Added weight increases the vertical force support of the hand, however this is not reflected by a change in motor unit recruitment in the forearm at the point of peak force. Furthermore, the EMG amplitude does not reflect the point of peak force at the hand.