Anthropometry of Wheeled Mobility Project: Final Report

3.3.14 Grip Strength

There were large differences in the percentage of individuals capable of completing the gripping tasks and, for those able to complete the tasks, the distribution of the grip strength for the three different grips were different between men and women, and across WhMD types (Figure 3‒14). For power grips, the percentage capable of completing three repetitions of maximal grips ranged from 77% (male power wheelchair users) to 100% (male scooter users). Overall, fewer WhMD users were able to complete the lateral pinching tasks (e.g. 73‒74% of power wheelchair users) and thumb-forefinger pinching tasks (e.g. 68‒69% of power wheelchair users).

For those individuals able to complete the pinching tasks, the results showed that both the ability to perform a grip and the magnitude of maximum grip force are substantially affected by the type of hand grip being considered. In particular, the magnitude of maximum power grip forces was noticeably greater in a power grip than in a pinch grip. Further, between the two pinch grip postures, the data show lateral pinch grips to be marginally greater than thumb-forefinger pinch grips.

Hand grip forces were typically greater for men than women, across users of the three different WhMD types. When compared across WhMD types, users of manual chairs typically produced the greatest magnitude of grip force, followed by scooter users and then lowest for power chair users. An exception to this trend was the lateral pinch grip forces among women. Not included in this analysis, are the effects of arm posture (e.g. elbow flexed at 90-degrees vs. an outstretched arm) (see D’Souza et al., in review), medical condition and age (see Joseph et al., 2010).

A comparison with the ADA-ABA permissible force limit for operating controls showed that more than 95% of the sampled WhMD users who were able to perform a power grip could exert a maximum power grip force exceeding 5 lbf.

However, the 5 lbf force limit substantially exceeds the 5%tile values of grip for the pinch postures. For the WhMD users who were able to perform a power grip in this study, approximately 25% of the WhMD users could not exert a maximum lateral pinch force that exceeded 5 lbf. About 25% of male WhMD users and 50% of female WhMD users could not exert a thumb-forefinger grip that exceeded 5 lbf.

* Percent capable indicate the percentage of the sample (grouped by gender and device type) capable of successfully forming a hand grip and exerting a force for three repetitions of the prescribed grip postures.

** 95^th percentile value same as maximum value due to small sample size.

Figure 3-14. Grip force: research findings versus the standard.

* Percent capable indicate the percentage of the sample (grouped by gender and device type) capable of successfully forming a pinch grip and exerting a force for three repetitions of the prescribed grip type.

** 95^th percentile value same as maximum value due to small sample size.

Figure 3-14. Grip force: research findings versus the standard. (Cont’d)