Journal
GAIT & POSTURE
Volume 95, Issue -, Pages 264-269Publisher
ELSEVIER IRELAND LTD
DOI: 10.1016/j.gaitpost.2020.11.010
Keywords
Stability; Elderly; Motor control; Muscle quickness; Muscle response
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This study investigated the associations between hip abductor muscle strength, RTD (rate of torque development), RTD-SF (rate of torque development scaling factor) and responses to external postural perturbations in older adults. The results showed a moderate positive correlation between RTD-SF and the consistency of postural responses at the lowest perturbation intensity. No other significant relationships were found.
Background: Recently, the rate of torque development scaling factor (RTD-SF) has been proposed as a useful tool that could contribute to a more comprehensive insight into muscular capacity. While lower RTD-SF is associated with ageing and certain neuromuscular diseases, it remains unknown whether this novel measure is associated with the postural control in the older adults. Research question: Are hip abductor muscle strength, RTD and RTD-SF associated with responses to external postural perturbations in medio-lateral direction in older adults? Methods: Twenty healthy older adults (14 females, 6 males) were assessed for hip abductor muscle strength, RTD and RTD-SF, using a custom-built dynamometer. Perturbations were applied at waist level (4 perturbation intensities, 15 repetitions each) using a wire-pull paradigm, with centre-of-pressure (CoP) being recorded with force plates. For each condition (i.e. perturbation intensity), medio-lateral displacement and velocity of the CoP were computed. For both parameters, within-individual variation (representing consistency of the responses), expressed by the standard deviation (SD) of CoP parameters was also considered. Pearson correlation coefficients were computed between parameters of hip muscle capacity and CoP responses and SD values of CoP responses. Results: RTD-SF was moderately positively related to the consistency of the responses of both CoP displacement and velocity (r = 0.53-0.56; p = 0.011-0.016) at the lowest level of the perturbation magnitude (15 N). No other statistically significant relationships were found (all r < 0.35). Significance: RTD-SF could play a role in preserving postural balance in older adults when low-intensity perturbations are applied. RTD-SF is a novel outcome measure that could represent an important alternative clinical tool to traditional strength assessments. It could represent a supplementary tool to assess the risk of falls, however, several limitations and ambiguities need to be resolved by future research before it can be utilized in practice.
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