Affiliations: [a] School of Human Sciences, St Mary's University
College, Twickenham, UK | [b] School of Life Sciences, Kingston University,
Kingston-upon-Thames, UK
Note: [] Address for correspondence: Glyn Howatson, School of Human
Sciences, St Mary's University College, Strawberry Hill, Twickenham, Middlesex
TW1 4SX, UK. Tel.: +44 208240 4076; Fax: +44 208240 4255; E-mail:
howatsong@smuc.ac.uk
Abstract: The aim of this investigation was to examine the intra-subject and
group reproducibility of isokinetic muscle function testing and the associated
surface electromyography (EMG) signal on repeated days testing. Fifteen
subjects who were unfamiliar with isokinetic dynamometry completed maximal
isokinetic elbow flexor contractions at 60°/s and
210°/s on five consecutive days. Surface
electromyography was recorded from the biceps brachii to examine the electrical
activity associated with the peak torque. The intra-subject reproducibility was
moderate for isokinetic torque: mean coefficient of variation (CV) of 8.93% at
60°/s and 9.14% at 210°/s, however the EMG and EMG:torque ratio
were somewhat more variable: mean CV of 15.18% and 18.42% at 60°/s,
respectively and 11.97% and 14.50% at 210°/s, respectively. The group
reproducibility for all variables at both isokinetic speeds were high with
intraclass correlation coefficients ranging from 0.92 and 0.99. In addition,
the group CV for isokinetic peak torque, EMG and EMG:torque ratio for both
contraction speeds ranged from 1.47% to 5.12%. These results illustrate that
individual subjects can show large day-to-day variations in torque and EMG,
however when group data are examined, both torque and the associated EMG
activity demonstrate high reproducibility. Practitioners should therefore
express caution when interpreting longitudinal changes in an individual's
isokinetic data.
