tasks requiring a brief increase in force require-ments (Fransson-Hall & Kilbom, 1993).Of further note is the force difference observed between the one-handed pinch and the two-handed pinch. One may expect that the force should double when using both hands. The results illustrate that this did not occur and may indicate the possibility of force sharing between both hands. If both hands share the same force, then a decrease in relative force for each hand occurs. It is also important to consider that the one-handed pinch used both the index and mid-dle finger while the two-handed pinch was con-strained to using only the index finger, which may have also influenced the force generated.Wrist postures were captured for each pinch type, and it was found that even though partici-pants were encouraged to position the syringe using neutral wrist postures and as comfortable as possible, deviated, flexed, and extended wrist pos-tures were still observed. This may indicate that neutral wrist posture may not be the most comfort-able for maximum strength generation. It may also suggest that users may have reduced ability to maintain a neutral wrist posture during maximum static grip exertions compared to submaximal exertions. Our previous work with gripping found that to maximum grip forces were similar between a neutral and extended wrist but reduced greatly with flexion. At lower force levels, this effect was reduced (Mogk & Keir, 2003). The use of an extended wrist while applying force also has con-sequences to the median nerve due to increased pressure in the carpal tunnel (Keir, Bach, Hudes, & Rempel, 2007; Keir, Bach, & Rempel, 1998). It is important to note that while wrist postures were not analyzed, the use of neutral posture is encouraged, especially understanding that majority of work tasks require lower relative forces. Therefore, the ability for the individual to control the wrist pos-ture along with choice of pinch grip is possible and subsequently reduces the risk of MSDs.There are a few limitations to this study. While we used a fixed force transducer to measure static press forces, the maximal forces obtained should be considered representative of the very slow push rates (1–2 ml/minute). It is also important to con-sider that liquids are incompressible, thus the “feel” of the test was similar to starting a press or when there is a blockage in the line. Second, we Figure 3.Mean maximal pinch grip force (N) with standard deviations of all pinch grip types in both wide and narrow grip spans. The thenar pinch had higher forces in the wide span while all other pinch grip types had greater force in the narrow span (p< .05). The * indicates there was a statistically significant difference between wide and narrow grip spans for this grip type, whereas the + indicates that these grips were significantly different from grips denoted by #.
1094 November 2017 - Human Factorsused administrative workers who were not accus-tomed to operating a syringe. This combined with a relatively small sample size limits our ability to generalize the findings to all trained workers. In
- Fall '07
- Statistical significance, Median nerve, Hand strength, pinch grip