The effect of repeated exposure to a simulated moving environment on lower limb muscle co-contraction and balance

Stone, Maria (2020) The effect of repeated exposure to a simulated moving environment on lower limb muscle co-contraction and balance. Masters thesis, Memorial University of Newfoundland.

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Abstract

The use of 6 Degrees of Freedom motion platforms to induce habituation to offshore motions is a relatively new area of study. One of the biggest challenges is assessing and determining the effectiveness of the training. This is assessed by measuring muscle activity of postural control muscles in the lower limb by analyzing changes in total muscle activity over the course of a trial or using an equation to compare co-contraction between muscle pairs, termed the co-contraction index (CCI). These techniques combined allow researchers to draw conclusions regarding the use of habituation as a preventative intervention to workplace injuries that may occur in offshore environments. The purpose of the present study was to examine changes in lower limb muscle activity and interpret the effectiveness of implementing varied motion profiles on an individual’s ability to habituate to these environments. Participants, with no previous experience in moving environments, were exposed to a total of 9, 5-minute trials of simulated motion, performed on a 6 degrees of freedom motion simulator. During trials 1, 8 and 9, muscle activation and video data were recorded. The remaining 6 trials consisted of varied motion sequences and were considered the habituation trials. Results indicated decreased total muscle activation, CCI and total number of steps taken values from pre-habituation to post-habituation trials. There were no significant changes between pre-habituation and retention trials, which were completed no longer than 48 hours after the habituation session. This indicates that longer-term effects did not occur. Frequency analysis of electromyographic data indicates there was no effect of fatigue from pre to post-habituation trials. The decrease in muscle activity seen can be indicative of decreased energy cost during postural control tasks. It is possible that this may lead to a decrease in the onset of fatigue and subsequently injury risk in maritime occupations.

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