Muscle fatigue and discomfort associated with standing and walking : Comparison of work surfaces

Localized muscle fatigue and perception of fatigue/discomfort in the lower legs induced by a 5 hour standing work task were evaluated for 3 different work surfaces (linoleum tiles on concrete floor, rubber mat, sole insert) in young adults and older individuals. Muscle fatigue was quantified by the muscle twitch force (MTF) magnitude and subjective ratings. The results indicate that the work task induces fatigue in lower leg muscles and this fatigue is similar for both age groups. Recovery from fatigue 1-hour post work was partial only and was greater for the younger than for the older participants. In other words, fatigue persisted and tended to persist longer for the older than the younger individuals. For younger individuals the long lasting effects of fatigue (0.5 hour post work) tended to be more pronounced on the laboratory floor and the mat than on the sole inserts and recovery (1 hour post work) tended to be more pronounced for the sole inserts than the other surfaces. For older individuals the long lasting effects of fatigue and recovery were similar for all surfaces. Fatigue was not significant on the control day. Generally, subjective perception of fatigue/discomfort in the feet and lower back tended to increase with time during the work task and was negligible 1-hour post work as well as on the control day. However, subjective and objective measures are not highly correlated since dissociations exist for both younger and older individuals. Hence, the results strongly suggest that reduction of leg muscle fatigue may not be adequately achieved by the use of at least some work mats or shoes. In addition, perception of fatigue/discomfort is an inappropriate indicator of long-term health effects and for the evaluation of muscle fatigue on work surfaces. Although perception of better comfort may have a positive influence on workers this does not resolve the issue.