Differences in Lower Limb Muscle Activation and Centre of Pressure Movement Between Expert Workers and Novices in Simulated Maritime Environments

Abstract

OCCUPATIONAL APPLICATIONS Better understanding of lower limb muscle activations and habituation processes has implications for injury prevention. This study examined the influence of repeated exposures to simulated wave motions on lower limb muscle activity. Our findings suggest that, at least while standing, novice maritime workers can quickly adapt their lower extremity muscle activity and, to a lesser extent, their center of pressure movement, so that is similar to expert maritime workers. These decreases in muscle activations with repeated exposures suggest that individuals can adapt rapidly to the motions to decrease muscle fatigue and the risk of falling. Such information should therefore be considered when developing ergonomic interventions for maritime occupations such as ship design and training for new workers.

TECHNICAL ABSTRACT Background: Work in moving environments, such as maritime workplaces, exposes workers to unique neuromuscular control challenges that may increase risk of falls or fatigue-related injury. Purpose: The purpose of this study was to determine if muscle activations differ based on previous experience working in a moving environment and/or with repeated exposure to the same motions. Methods: Twelve individuals with no maritime work experience, and 14 individuals with maritime work experience, were exposed to five 5-minute trials of simulated maritime motion. Electromyography (EMG) was collected bilaterally from several lower-extremity muscles and center of pressure was collected using a pressure mat over the full duration of all of the trials. EMG data were normalized to maximal voluntary isometric contractions (MVICS) collected before the trials, and then compared between groups and trials. Results: Muscle activation in both groups significantly increased with motion exposure, however the activation amplitudes were lower in the experienced (346% increase) vs. the novice group (542% increase). With repeated exposure to the five motion trials, muscle activations for all individuals gradually decreased from trial 1 (∼5–15%MVIC) to trial 5 (∼1.5–4.5%MVIC).

Conclusions: While all individuals demonstrated adaptations with repeated exposures, those with experience working in maritime environments adopted postural responses that required substantially less activation of the lower limb muscles. This difference may be due, at least in part, to these individuals having adapted postural control strategies to optimize stability. The decrease in muscle activation observed with repeated exposure to the motion profile suggests that individuals can adapt rapidly to the destabilizing nature of the motion profiles, implying that they are learning to adopt more efficient postural control strategies.

KEYWORDS:

• industrial Ergonomics
• Effects on the musculo-skeletal system
• Posture