Sports Performance Wearable Technology, sEMG, and Manual Muscle Testing: Practical Methods for Measuring Maximal Voluntary Contractions

Abstract

PURPOSE: The development in sports performance wearable technology has allowed for the monitoring of an athletes’ internal load via surface electromyography (sEMG) - based garments. These garments have been shown to be a valid tool for measuring sEMG in sports settings. However, to conduct valid comparisons of sEMG, current methods often involve referencing data from a particular movement to a maximal voluntary contraction (MVC). MVCs are typically measured using an isokinetic dynamometer (ISO); however, with the application of sEMG in a sports environment utilizing an ISO can be impractical. An alternative is the use of manual muscle testing (MMT), in which manual resistance is applied by a trained practitioner to invoke a MVC. The purpose of this study was to compare sEMG-based garment measurement of MVCs elicited using ISO versus MMT in lower extremity muscles. METHODS: Twelve healthy, physically active participants (7 males, 5 females) were recruited for this study. Participants were fitted with a sEMG-based compression short or legging embedded with sEMG sensors. Following a dynamic warm-up, participants performed, in a randomized order, either ISO or MMT normalization protocols to measure the MVC of the vastus medialis (VM), vastus lateralis (VL), bicep femoris (BF) and gluteus maximus (GM). Data were sampled at 1KHz and band pass filtered, with the peak amplitude of the MVC used for analysis. Paired samples t-tests (p < .05) were used to compare the mean peak amplitudes from each muscle between ISO and MMT protocols. Pearson’s correlations (p < .05) were conducted to evaluate the degree of the relationship of peak amplitudes obtained by the two protocols for each muscle. RESULTS: No significant differences (p = .47-.88) were found between any of the muscles when comparing mean peak amplitudes for the ISO and MMT protocols. Significant correlations indicated a positive association between peak amplitudes obtained through ISO and MMT for the VM, RF, and BF (r > 0.80, p < .001 for all) and for the GM (r = .63, p = .022. CONCLUSIONS: The present data demonstrated that similar sEMG MVC data for the VM, VL, BF, and GM were recorded for the ISO and MMT. This suggests that the use of MMT, when administered by a trained member of staff, could be a practical method for normalizing each of the measured muscles to the MVC in a field environment.