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Blackwell, Kornatz, and Heath (1999) investigated the effect of grip span on isometric grip force. An optimal grip size allowed for the greatest forces. Batra et al. (1994) demonstrated that reduction in grip strength was positively correlated with glove thickness but not with glove size. In a subsequent analysis, the following selected glove attributes were correlated to reductions in demonstrated strength: (1) tenacity—friction between the glove and a standard piece of plastic, (2) snugness—hand volume versus glove volume, (3) suppleness—a measure of pliability, and (4) thickness. A decrease in grip force was significantly affected by glove type—asbestos and leather gloves reduced grip strength to approximately 82.5 percent of bare-handed levels, while surgical gloves reduced grip strength to 96.3 percent of bare-handed levels.
Mital and colleagues studied the influence of a variety of commercially available gloves on the force-torque exertion capability of workers when using wrenches and screwdrivers in routine maintenance and repair tasks (Mital, Kuo, and Faard, 1994). Subjects exerted a maximum volitional torque during a simulated task. The results indicated that tool type was a predictor of volitional torque. Gloves also affected volitional torque; torque was greater with the use of gloves.
Temperature can be an important moderating variable. Riley and Cochran (1984) studied manual dexterity performance at different ambient temperatures. Subjects wore typical industrial worker apparel without gloves during manual dexterity tests. Results indicated that after 15 minutes of cold exposure, there was no difference between performance at 12.8 and 23.9 degrees Celsius, but there was a difference between performance at 1.7 and 12.8 degrees as well as between performance at 1.7 and 23.9 degrees. Holewijn and Heus (1992) found that isometric grip strength was significantly reduced by cooling. The rate of force buildup was also influenced by temperature, with slower buildup under conditions of cooling. Cooling reduced the maximum grip frequency by 50 percent compared with the reference condition. The endurance time for the sustained contraction at 15 percent MVC was reduced by 50 percent with warming compared with the reference condition.
A psychomotor task was developed by Jeng, Radwin, and Rodriquez (1994) for investigating functional deficits associated with carpal tunnel syndrome. A rapid pinch and release psychomotor task utilizing muscles innervated by the median nerve was administered. Subjects were instructed to pinch the dynamometer above an upper force level and then release below a lower force level as quickly as possible. Average pinch rate decreased from 5.4 pinches/sec to 3.7 pinches/sec as the upper force increased from 5 to 50 percent MVC. Pinch rate was significantly faster and overshoot force was less for the dominant hand. Control subjects