Influences of span and wrist posture on peak chuck pinch strength and time needed to reach peak strength

• Published in: International journal of industrial ergonomics 2005-06, Vol.35 (6), p.527-536
• Main Authors: Shih, Yuh-Chuan, Ou, Yu-Chin
• Format: Article
• Language: English
• Subjects: Maximum acceptable sustained time; Maximum volitional contraction; Pinch; Splints
• ISSN: 0169-8141; 1872-8219
• DOI: 10.1016/j.ergon.2004.12.002

Evaluation of pinch strength is useful in alleviating carpal tunnel syndrome (CTS), and when peak strength is reached (denoted as T MVC), may be a useful and interesting index for evaluating strength generation and the relationship between resistance and response time. This paper intends to investigate the effects of pinch span and wrist posture on how much time is required to reach MVC ( T MVC), as well as MVC. Thirty right-handed subjects including 15 males and 15 females volunteered for this experiment. A nested-factorial design was employed with four fixed independent variables of gender, subject (nested within gender), span (2, 4, 6, and 8 cm) and wrist posture (neutral, maximal extension and maximal flexion). The ANOVA results indicate that male MVC is greater than female MVC at any given span or wrist posture. On average, male MVC is 89.6 N, and female MVC is 53.6 N, nearly 60% that of males. For both genders and under four spans, neutral MVC is the greatest and maximal-flexion MVC is the least. Additionally, both neutral and maximal-extension MVCs increase as span increases, but maximal-flexion MVC increases up to 6 cm, and then decreases at 8 cm. On the other hand, only the gender effect on T MVC is significant. Average male T MVC is 1.828 s, and it is 1.346 s for females. Notably, the effects of span and wrist posture are not able to affect T MVC at all, even if they affect MVC pronouncedly. Present data provide useful information about the effects of grip span and extreme wrist posture on tool/task design requiring pinch strength. The T MVC possible becomes the upper limit of response time to overcome resistance in tools/tasks.