Date of Award
Master of Science (MS)
Kinesiology and Health Science
Background: Forward falls are the most common fall direction and pose safety concerns for adults. To prevent forward falls, compensatory steps, and change-in-support reactions (e.g., foot contact) are critical for restabilizing center of mass after unpredictable, balance disturbances. Multi-joint, lower limb eccentric and isometric strength may provide additional insight on foot contact responses after a forward, temporally unpredictable perturbation. Multi-joint, eccentric muscular contractions have been found to result in significant neuromuscular adaptations (e.g., hypertrophy and muscular strength) and have higher retention capabilities than concentric contractions. Due to the importance of muscular strength in balance recovery, eccentric muscular strength could provide a new insight into improving future fall prevention programs. The primary aim of our investigation was to determine the relationship between restabilization after foot contact, age, and self-reported physical activity in response to a forward, temporally unpredictable perturbation and multi-joint muscular strength in the lower limbs. We hypothesized that adults who were faster at restabilizing after foot contact (e.g., time to restabilize), would produce greater multi-joint eccentric and/or isometric peak force. Our secondary aim was to assess the mean difference between preferred and non-preferred limb time to restabilize. We hypothesized that adults would restabilize faster on their preferred limb compared to non-preferred limb.
Research Question: Are adults with a greater capacity to restabilize after foot contact (time to restabilize) able to produce greater multi-joint eccentric and/or isometric peak force?
Our central hypothesis was that adults who have a greater capacity to restabilize after foot contact, or time to restabilize, would produce greater multi-joint eccentric and/or isometric peak force. Do adults restabilize faster on their preferred limb compared to their non-preferred? Our secondary hypothesis was that adults would restabilize faster on their preferred limb compared to non-preferred limb.
Methods: Our sample consisted of 30 adults (31.2 ± 12.1 years, range: 18-58). Participants performed two blocks of 12 trials of forward, temporally unpredictable perturbation trials on both their preferred and non-preferred stepping limbs followed by assessments of multi-joint eccentric and isometric strength. Multivariate, linear regressions were used to evaluate the relationships and trends among variables. A paired-samples t-test was conducted to assess the mean differences between preferred and non-preferred limb time to restabilize.
Results: Individual multiple linear regression analyses indicated that neither multi-joint eccentric (r = 0.385, p = 0.308) nor isometric (r = 0.317, p = 0.519) strength had a significant impact on restabilization time in response to a forward perturbation in our sample of adults. A paired-sample t-test indicated no mean difference between preferred limb and non-preferred limb time to restabilize (t (28) = 0.980, p = 0.335).
Significance: Eccentric and isometric multi-joint lower body strength was not a performance predictor for restabilization time to a forward perturbation. Additionally, restabilization time did not differ between limbs. Future work will investigate the impact of lower limb multi-joint eccentric rate of force development as well as surface electromyography to assess whether these measures provide additional insight on forward step restabilization.
Ashworth, Leandra K., "Relationship of Eccentric Strength and Forward Perturbation Restabilization After Foot Contact" (2022). All Graduate Plan B and other Reports. 1643.
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