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RELATIONSHIP BETWEEN DYNAMIC POSTURAL STABILITY AND DYNAMIC KNEE VALGUS WHEN RUNNING

Abstract

Excessive knee valgus is correlated with many orthopedic injuries. Gaining insights into potential relationships between knee valgus and other biomechanical assessments has potential to inform more effective training, injury prevention, and rehabilitation programs. Dynamic postural stability (DPS) may be correlated with dynamic knee valgus (DKV) during a running task due to potentially overlapping muscle activation and sensory input required for both the DPS and running tasks. PURPOSE: To investigate the relationship between DPS during a unilateral jump task and DKV during a running task. METHODS: 28 participants (n = 12 female) completed a horizontal, unilateral jump task onto a pressure sensor platform. Participants jumped off and landed on the same leg. All participants performed the task on both legs. Participants held their landing for 5 seconds. The pressure sensor platform calculated the following center of pressure (CoP) metrics with a frequency of 250Hz: area, distance, anterior to posterior excursion, and lateral to medial excursion. After the jump task, participants completed a 5.5-minute treadmill run. At the 5 minute-mark of the run, an iPad recorded a frontal plane video of the participants’ lower extremities at 1080 frames per second. Maximum DKV angle was measured during the period immediately after the stance leg reached midstance and prior to the femur of the swing leg passing the femur of the stance leg. Maximum DKV measurements were measured across 4 steps per leg and then averaged. These measurements were taken via video analysis of previously placed anatomical markers. Four linear regression models, in which the covariate of shoe size was controlled for, were created per leg. RESULTS: The maximum DKV angles had mean values of 6.0 ± 5.7 (right) and 5.4 ± 5.3 (left). The anterior-posterior CoP excursion had mean values of 15.3 ± 3.6 cm (right) and 15.8 ± 3.1 cm (left). The lateral-medial CoP excursion had mean values of 5.4 ± 1.5 cm (right) and 5.5 ± 2.2 cm (left). No significant relationships were found between any CoP metrics and maximum DKV (P>0.05). CONCLUSION: Dynamic postural stability, as assessed by a unilateral jump task, does not correlate with maximum DKV when running. The clinical implications suggest that training to reduce DKV does not need to include exercises aimed at improving DPS.

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