Reliability of measurements of wrist extension force obtained with a Nicholas Manual Muscle Tester (NMMT)

Abstract

The primary aim was to determine the intra- and interexaminer reliability of measurements of isometric wrist extension force obtained with the Nicholas Manual Muscle Tester (NMMT) in a “break test.” A secondary aim was to use NMMT measurements to describe the relation between electromyographic (EMG) activity and force produced in wrist extensors at different levels of contraction strain. Two examiners tested 51 healthy subjects (aged 19–46) in a test-retest approach with 6–7 days between the tests. Eleven subjects from this sample were also recruited for the study investigating the relation between EMG and force in the wrist extensor. Intraexaminer reliability was excellent for both examiners (ICC 0.944 and 0.902). The results also showed excellent interexaminer reliability (ICC 0.925) and relatively low CV% and S_diff. The EMG-force relation in wrist extensor muscles was strong (r = 0.985). The excellent test-retest stability indicates that measurements of isometric wrist extension force obtained with NMMT are appropriate for clinical evaluation as well as for further studies of wrist isometric extensor muscle strength. The tests indicated that the relation between force produced and levels of EMG activity in wrist extensor muscles is approximately linear.

ACKNOWLEDGEMENTS

This article is based on a Swedish edition previously published in the journal Nordisk Fysioterapi (Nordic Physiotherapy) 2005; 9: 25–39. The authors wish to thank the prior publisher Taylor & Francis, Stockholm for giving their permission for publication in English. Additionally, parts of this paper was presented as an abstract for poster presentation at The International Congress on Gait and Mental Function, February 3–5, 2006, Madrid, Spain.

Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.