Physical Activity, Exercise Physiology, Movement
Limb strength and limb initiation during a step forward to upright standing task
(School of Public Health (UMD) Kinesiology Master's Student)
This work aimed to determine if neurological preference for selecting an initiation limb while stepping forward is associated with limb strength. Due to reported initiation preference and established able-bodied termination loading analysis, it was hypothesized that 1) limb strength and dominance would correlate with the second limb to impact and 2) loading of the first limb to terminate would be greater than the second. 62 uninjured participants completed a single motion capture data collection after completing IRB approved informed consent. Participants were fit with a lower body marker set, asked to stand with their feet “about shoulder-width apart”, and took 2 foot strikes forward onto two embedded force platforms (Kistler, USA). Kinematics (200Hz) were collected simultaneously with analog data (1000Hz). An isokinetic dynamometer (Biodex, USA) was used to measure 3 reps each of max voluntary isokinetic (60 deg/s) knee flexion and extension. The stronger limb was defined as the limb which produced more torque. The dominant limb was the one participants would use to kick a soccer ball. Between-limb extension torque deficits were not different between groups who took the first or second step with the stronger limb (p = 0.72). Limb dominance was not associated with strength (p = 1.00) or limb selection (p = 0.12). Limb strength was not associated with limb selection (p =0 .43). Limb loading was greater for the initiating limb (KAM: p < 0.001; vGRF: p < 0.001). In an able-bodied population, there appears to be no correlation between limb strength and the selected initiation limb. Contrary to our hypothesis, this result suggests that the demands of stepping-to-upright-standing are not sufficient for the nervous system to control this motion in a consistent fashion between individuals. Future research should evaluate completion of this task in individuals with varying levels of strength and between-limb functional deficits.