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Faculty Advisor(s)

Joaquin Barrios, PT, PhD


Purpose: 3D joint kinetics are routinely studied in various lower limb musculoskeletal conditions. Often, a condition affecting a joint is associated with altered kinetics at that same joint, such as knee osteoarthritis being associated with reduced knee flexion moments. However, these same-joint alterations may also contribute to altered comprehensive movement patterns of the entire limb in a synergistic manner. A lower limb biomechanical metric that represents this multi-joint kinetic chain synergy is the total support moment (TSM). Indeed, TSM has been found to be altered in knee osteoarthritis, anterior cruciate ligament reconstruction, and partial meniscectomy. Despite this, psychometric studies are lacking and the test-retest reliability of TSM metrics are unknown. Therefore, the purpose of this study was to assess the test-retest reliability of TSM metrics during walking and running. We hypothesized that at least moderate strength reliability estimates would be observed.

Subjects: 12 healthy participants (5 females, body mass index = 23.1±3.42kg/m2, age = 23.9±1.4 years) completed all testing.

Methods/Materials: Established 3D motion capture procedures and inverse dynamics calculations were conducted for stance-phase overground walking at 1.5 m/s and running at 3.7 m/s. Five successful trials per condition were captured for the right lower extremity. The anti-gravity internal extensor moments for the ankle, knee, and hip joint were derived and time-normalized to 101 point waveforms. TSM was determined by summing the three normalized waveforms. Peak TSM was expressed in Nm/(kg*m) and TSM impulse was expressed in Nm/(kg*m)%stance. Participants returned after one week to repeat the testing. Intraclass correlation coefficients were calculated for a two-way mixed effects model with absolute agreement. Minimum detectable change (MDC) values were calculated as percentages.

Results: For walking peak TSM and TSM impulse respectively, test-retest reliability coefficients were 0.944 and 0.862. MDC percent thresholds were 20% and 24%. Running coefficients were 0.941 and .937, respectively, with MDC percent thresholds of 11% and 13%.

Conclusion: As hypothesized, TSM measurements demonstrated good-to-excellent test-retest reliability during overground walking and running. MDC percent thresholds were smaller for running than walking.

Clinical Relevance: The use of TSM to characterize the kinetics of lower extremity movement strategies is increasing in the movement sciences. TSM metrics during running may be more sensitive to changes in movement strategy than for walking. Efforts to clinically translate this metric are warranted.

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Physical Therapy | Rehabilitation and Therapy

Altering the Lower Limb Kinetic Chain: Reliability and Minimum Detectable Change of Total Support Moment