The effect of two types of maximal voluntary contraction and two electrode positions in field recordings of forearm extensor muscle activity during hotel room cleaning

Abstract

This study aimed to investigate the effects of using hand grip or resisted wrist extension as the reference contraction, and two electrode positions, on field recordings of forearm extensor muscle activity. Materials and methods. Right forearm extensor muscle activity was recorded using two electrode pairs (over the most prominent part (position 2) and proximal to that (position 1)) during one working day in 13 female hotel housekeepers. Each subject performed the two maximal voluntary contractions (MVCs), and the electrical activity obtained during these (maximal voluntary electrical activity (MVE)) was used for normalization. Each set of recordings was analysed twice, once using hand grip as the MVC and once using resisted wrist extension. Results. Resisted wrist extension showed a higher group mean MVE than hand grip. Position 2 had higher correlation between MVE and force during the MVCs. The workload during cleaning was lower when using resisted wrist extension as reference than when using hand grip (24%MVE vs 46%MVE; p = 0.002 at position 2) for the 90th percentile. The workload (99th percentile) was overestimated in two subjects when using hand grip as reference. Conclusions. Problems associated with poorly activated forearm extensors can be overcome by using resisted wrist extension as reference.

Correlations between Ratings and Technical Measurements in Hand-Intensive Work

“…The used window length was 0.1 s. The FCR EMG electrode-pair was located at the forearm, three to four fingerbreadths distal to the midpoint of a line connecting the medial epicondyle and the biceps tendon [41]. The ECR electrode-pair was located on the radial side of the forearm, approximately one-third of the distance of the forearm length from the elbow in a line from the lateral epicondyle [42,43]. The muscle bellies were located through palpation during voluntary wrist flexion (FCR) and extension (ECR).…”

Development and Assessment of a Method to Estimate the Value of a Maximum Voluntary Isometric Contraction Electromyogram from Submaximal Electromyographic Data

“…35 Moving average filter with a 500-millisecond window size was used on the 2-second MVIC EMG data, and the maximum of these processed MVIC EMG data was found across the 2 MVIC trials performed. 36,37 The values of the SVC EMGs were calculated for each muscle and day of data collection following a similar procedure except that the mean values of the EMG data over the 2 seconds of SVC exertions were used instead of the 500-millisecond moving average filter. This was because, during the SVC exertions, the participant was exerting an acceptably steady torque (error of ±5%), while during the MVIC exertions, confirming a steady torque is not easily achievable due to the intense nature of the maximum exertions.…”