Biomedical subjects

Scott C White

Publications and source records attributed to Scott C White.

4 recordsLinked to original sources

PubMed2005

Altering asymmetric limb loading after hip arthroplasty using real-time dynamic feedback when walking.

OBJECTIVE: To evaluate a walking program incorporating real-time biofeedback to reduce asymmetric limb loading after total hip arthroplasty (THA). DESIGN: Within-subject clinical intervention. SETTING: Biomechanics laboratory. PARTICIPANTS: Volunteers were screened for confounding disorders that could affect their gait other than unilateral THA. Participants included 28 subjects who were evaluated a minimum of 2 months after surgery and ambulatory without assistive devices. INTERVENTIONS: THA subjects were assigned to a feedback, no-feedback, or control group. The feedback group walked on a treadmill 15 minutes, 3 times a week for 8 weeks while matching step-to-step reaction forces. Subjects walking without feedback had equal time. The control group did not train. MAIN OUTCOME MEASURES: Symmetry indices for peak limb-loading force, rate of rise of loading force, and impulse calculated from vertical foot-ground forces. Symmetry index changes were evaluated using 2-factor, repeated-measures analyses of variance with a Tukey post hoc test. RESULTS: Loading rate and impulse equalization improved for the feedback group (P<.01). Loading rate equalization improved for the no-feedback group (P=.01). There were no changes for the control group. CONCLUSIONS: This preliminary study suggests that a treadmill walking program may help persons with a THA achieve a more symmetric gait. Additional investigation of the potential benefits of a rehabilitation program incorporating treadmill walking with and without biofeedback is recommended.

Aged↗

PubMed2005

Differences in peak knee valgus angles between individuals with high and low Q-angles during a single limb squat.

BACKGROUND: Differences in anatomical alignment between genders have been suggested as causes of the disparity in anterior cruciate ligament injury rates. A larger Q-angle may be associated with increased knee valgus during movement resulting in anterior cruciate ligament strain. This study investigated whether healthy college-aged subjects with a large Q-angle display greater peak knee valgus during a single limb squat compared to those with a small Q-angle. The study also determined whether the high and low Q-angle groups displayed differences in other select anatomical variables, and whether these anatomical variables were related to knee valgus. METHODS: Twenty subjects, categorized as having a "high Q-angle" (> or = 17 degrees) or a "low Q-angle" (< or = 8 degrees) were videotaped during the performance of a single leg squat. The peak valgus angles for the right knee were calculated. One-tailed independent measures t-tests were used to determine whether individuals with a large Q-angle exhibit (1) significantly greater peak knee valgus during a single leg squat compared to those with a small Q-angle and, (2) greater pelvic width to femoral length ratios and greater static knee valgus than subjects with a small Q-angle. The Pearson product-moment correlation was used to establish the relationships between pelvic width to femoral length ratios and static knee valgus, pelvic width to femoral length ratios and dynamic knee valgus, and static knee valgus and dynamic knee valgus. FINDINGS: Peak knee valgus during the single leg squat, and static knee valgus were not significant greater in the high Q-angle group compared to the low Q-angle group (P=0.09; P=0.31). Subjects with a larger Q-angle, however, had a significantly greater pelvic width to femoral length ratios (P=0.015) compared to subjects with a small Q-angle. Pelvic width to femoral length ratios was related to both static and dynamic knee valgus (r=0.47, P=0.02; r=0.48, P=0.02), but static knee valgus was not related to dynamic knee valgus. INTERPRETATION: The findings suggest that pelvic width to femoral length ratios, rather than Q-angle, may be a better structural predictor of knee valgus during dynamic movement.

Adolescent↗

PubMed2005

Kinetic changes with fatigue and relationship to injury in female runners.

PURPOSE: This research examined how ground reaction forces (GRF) changed with fatigue induced by an exhaustive treadmill run in female runners. A separate retrospective and prospective analysis correlated initial magnitude of GRF and fatigue-induced changes in GRF with lower-extremity injury. METHODS: Ninety adult female runners had vertical GRF measured before and after an exhaustive treadmill run. Subjects initially were questioned about previous running injuries, and were contacted during the following year and asked to report any additional running injuries. RESULTS: Fatigue induced by the exhaustive treadmill run resulted in decreased impact peak and loading rates in all runners by an average of 6 and 11%, respectively. The changes in GRF were attributed to altered running cadence, step length, and lower-extremity joint kinematics. It is unclear whether these changes were attempts by the runners to minimize impact forces and protect against injury, or represented a fatigue-induced loss of optimal performance capabilities. An interaction between injury in the previous year and change in impact loading rate with fatigue was observed, suggesting previously injured runners are exposed to relatively higher impact forces over time. CONCLUSION: Habitual female runners appear to adapt their running style with fatigue, resulting in altered GRF. Changes in GRF with fatigue may be associated with lower-extremity running injuries.

Adolescent↗

PubMed2004

Asymmetric limb loading with true or simulated leg-length differences.

Unequal leg lengths result in asymmetric limb loading but opinions vary on the size of the difference inducing abnormal loading, and which limb sustains the greater load. Our study compared limb-loading asymmetries during walking for subjects with anatomic leg-length discrepancies between 1.0 and 3 cm, subjects without length discrepancies, and for subjects with a simulated a 1.31-cm leg-length discrepancy. Symmetry indices were calculated for peak ground reaction force during weight acceptance, rate of change of weight acceptance force, peak push-off force, and rate of change of push-off force. All symmetry measures were significantly different from normal for the simulated leg-length discrepancy. The shorter limb sustained a greater proportion of the load and loading rate. The anatomic leg-length discrepancy group showed the same trend with the exception of the push-off force rate. There were equivalent size-effect differences for both leg-length discrepancy conditions; however, for the anatomic leg-length discrepancy group, only the weight acceptance force symmetry value was statistically different from normal. The shorter limb sustains a greater proportion of load and loading rates; therefore, equalizing leg lengths should be considered even with bilateral differences less than 3 cm.

Adaptation, Physiological↗