Effects of Gloves and Pulling Task on Achievable Downward Pull Forces on a Rung

Abstract

Objective We examined the impacts of pulling task (breakaway and pull-down tasks at different postures), glove use, and their interaction on achievable downward pull forces from a ladder rung. Background Posture, glove use, and the type of pulling task are known to affect the achievable forces. However, a gap in the literature exists regarding how these factors affect achievable downward pulling forces, which are relevant to recovery from a perturbation during ladder climbing. Methods Forty subjects completed four downward pulling tasks (breakaway force; pull force at maximum height, shoulder height, and a middle height), using three glove conditions with varying coefficient of friction (COF) levels (cotton glove, low COF; bare hand, moderate COF; and latex-coated glove, high COF) with their dominant and nondominant hand. The outcome variable was the maximum force normalized to body weight. Results The highest forces were observed for the highest hand postures (breakaway and maximum height). Increased COF led to higher forces and had a larger effect on breakaway force than the other tasks. The dominant hand was associated with higher forces than the nondominant hand. Male subjects generated greater forces than female subjects, particularly for higher hand positions. Conclusion This study suggests that a higher hand position on the ladder, while avoiding low-friction gloves, may be effective for improving recovery from ladder perturbations. Application This study may guide preferred climbing strategies (particularly those that lead to a higher hand position) for improving recovery from a perturbation during ladder climbing.

Keywords: biomechanics; falls; hand forces; ladder climbing; pull strength.

Figure 1:

A) Diagram of the testing apparatus (reproduced with permission from Hur et al. (2012)). B) The three postures included in this study were shoulder height (upper left), medium height (lower left) and full height (right). C) The two glove designs used in this study included a cotton (left) and latex (right). A reprinted from Journal of Biomechanics, 45/6, Hur, P., Motawar, B., & Seo, N. J., Hand breakaway strength model—Effects of glove use and handle shapes on a person’s hand strength to hold onto handles to prevent fall from elevation, 958-964, Copyright (2012), with permission from Elsevier.

Figure 2:

Impact of task and glove condition on the maximum achievable force. Error bars represent standard deviation. Numbers are used to indicate statistical significance across task type for each glove conditions. Task types with the same number are not significantly different within a glove condition. Letters are used to indicate statistical significance across gloves for each task type. Gloves that have the same letter are not significantly different within a given task. Results are averaged across the two hands.

Figure 3:

The effect of gender and its interaction with task type on the peak force that was generated. Forces are averaged across hand and glove conditions. Error bars represent standard deviation. Numbers are used to indicate statistical significance across task type for each gender. Task types with the same number are not significantly different within a gender. Letters are used to indicate statistical significance across gender for each task type. Different letters indicate a difference in generated force across genders within a given task.

Figure 4:

Impact of hand dominance and task type on the peak force that was generated. Forces are averaged across glove condition.