Intraindividual Variability and Validity in Smart Apparel Muscle Activity Measurements During Exercise in Men

The purpose of the study was to compare smart apparel (SA) muscle activity measurements to surface electromyography (sEMG) muscle activity measurements during exercise, and determine if any systematic bias of the apparel exists. Thirty-five male participants (Ages 23.1±2.92 yrs, height 178±0.09 cm, mass 81.14±10.59 kg, body fat percentage 15.4±4.79%) provided informed consent for participation. During two separate exercise sessions, participants performed three sets of 12 bodyweight squats and pushups in both SA and sEMG. Conditions (sEMG or SA) were randomly counterbalanced. During sEMG, sensors were placed at selected anatomical locations on the right side. During SA, sEMG sensors were sewn into the fabric. Percent of maximal voluntary contractions (%MVC) were calculated. Paired t-test were used to analyze group mean differences in %MVC between conditions. Bland & Altman plots were created to determine any systematic bias. A Pearson's product correlation was run to determine any association with intertrial variability and body fat percentage. The alpha levels were set a p<0.05. It was determined that there were no significant differences between %MVC in the SA and sEMG for three of the selected muscles (p>0.05). There was a significant difference in %MVC measured in the SA and sEMG for the RDELT (p=0.02). Specifically, the %MVC for the deltoid during pushups was 11.8% greater compared to sEMG. Intertrial differences were not significantly correlated with %BF (p>0.05). The apparel appears to be valid in the recreational population and appears to have no systematic bias.