The Influence of Leg Dominance on Coordination during a Closed-Chain Tracking Task
Context: The Monitored Rehabilitation Functional Squat System (MRFSS) provides objective feedback on closed-chain activities and has been found to be accurate, valid, and reliable. Clinicians often compare an injured limb to a non-injured limb as a measure of progress for patients undergoing rehabilitation. Knowledge of inherent differences in coordination based on leg dominance is critical to helping the clinician set appropriate outcome goals.
Objective: To determine if healthy dominant and non-dominant legs have comparable coordination.
Design: Single group, repeated measures.
Setting: Outpatient clinic.
Participants: Convenience sample of 21 males (age 26.4±4.7; height 177.9±5.6cm; weight 81.5±14.9kg; visual acuity left 20/24.8, right 20/25.8) recruited from an adult recreation league. Exclusion criteria included past ACL injury, current lower extremity injury and central nervous system pathology.
Interventions: After providing consent, participants’ height, weight and visual acuity were measured (Sloan eye chart) then participants performed a five-minute unresisted stationary-bike warm-up. Leg dominance was assessed with 3 tests (ball kick, step-up, jump-landing) and the leg used for 2 or 3 of the tests was considered dominant. Participants were blinded to the study’s dominance component; they were simply asked to perform the tasks. The MRFSS was adjusted so participants started each test with their knee flexed between 90˚-100˚ and hip flexed between 85˚-95˚. Foot placement on the footplate was marked with tape to ensure consistency throughout testing. MRFSS resistance was set at 10% (to the nearest 5kg) of body weight. Scripted instructions were read. Participants acclimated to the leg-press-like apparatus by sliding the sled through flexion and extension of the knees and hips bilaterally. Participants were positioned with the test foot flat on the footplate, arms crossed on the chest and non-test foot on the adjacent footrest. The MRFSS monitor was visible to the participant. During each trial a consistent path was displayed on the monitor; participants had to flex or extend lower extremity joints to keep the computer cursor positioned on the path. Participants completed eight 60-second trials per leg with 60 seconds of rest between trials. Leg test order was randomized. Mean results of trials 5-8 (to minimize effects of learning) for both dominant and non-dominant legs were compared using a paired samples t-test.
Main Outcome Measure: Tracking accuracy (i.e., distance from target path (mm)) as measured by the MRFSS software.
Results: The mean distance from the target for dominant limbs was 4.53±0.89mm and for non-dominant limbs 4.56±0.81mm (t(19)=.27, p=0.79).
Conclusions: There was no significant difference in tracking accuracy between dominant and non-dominant legs. The objective representation of coordination in this tracking-accuracy task supports the appropriateness of using the non-injured limb as the standard for comparison when goal-setting or measuring progress for those undergoing rehabilitation.
