Endurance time is joint-specific: A modelling and meta-analysis investigation

Abstract

Static task intensity–endurance time (ET) relationships (e.g. Rohmert's curve) were first reported decades ago. However, a comprehensive meta-analysis to compare experimentally-observed ETs across bodily regions has not been reported. We performed a systematic literature review of ETs for static contractions, developed joint-specific power and exponential models of the intensity–ET relationships, and compared these models between each joint (ankle, trunk, hand/grip, elbow, knee, and shoulder) and the pooled data (generalised curve). 194 publications were found, representing a total of 369 data points. The power model provided the best fit to the experimental data. Significant intensity-dependent ET differences were predicted between each pair of joints. Overall, the ankle was most fatigue-resistant, followed by the trunk, hand/grip, elbow, knee and finally the shoulder was most fatigable. We conclude ET varies systematically between joints, in some cases with large effect sizes. Thus, a single generalised ET model does not adequately represent fatigue across joints.

Statement of Relevance: Rohmert curves have been used in ergonomic analyses of fatigue, as there are limited tools available to accurately predict force decrements. This study provides updated endurance time–intensity curves using a large meta-analysis of fatigue data. Specific models derived for five distinct joint regions should further increase prediction accuracy.

Keywords:

• holding time
• fatigue
• isometric
• muscle
• references
• elbow
• knee
• shoulder
• ankle
• trunk
• grip

Acknowledgements

We would like to acknowledge Ting Xia for his assistance with the initial literature search process, Mardy Frazier for his valuable manuscript feedback, and Carol Leigh for assistance with manuscript preparation.

The authors were funded in part by the National Institutes for Health, K12 HD055931 and 1K01AR056134 (LFL) and NRSA F31 AR056175 (KA), the Foundation for Physical Therapy (KA), and through a contract with the United States Council for Automotive Research (USCAR), Dearborn, MI. Preliminary results were presented in abstract form at the American Society for Biomechanics, August 2009.