Previous research has shown that excessive hip internal rotation can lead to abnormal patellar maltracking and thereby to lower limb injuries, such as patellofemoral pain and non-contact ACL injuries. Researchers in the USA invented the PowersTM strap to increase external rotation of the femur and to thereby stabilise the patellofemoral joint during leisure and sport activities. This study aimed to investigate whether the PowersTM strap influences knee and hip biomechanics during the single leg squat (SLS) and step down task (SDT), which are activities which involve excessive hip internal rotation, adduction and knee valgus. 17 healthy participants, 7 males and 10 females (age: 29±4 y, height: 1.72±0.07 m, mass: 65.4±8.7 kg) were required to perform the single leg squat and step down tasks during two conditions: without and with the PowersTM strap. Three-dimensional analysis was conducted with ten Qualisys OQUS7 cameras and three AMTI force plates using a 6DoF biomechanical model. The normality was assessed using the Shapiro-Wilk test. Paired sample t-tests were performed at the 95% confidence interval. The PowersTM strap condition (red line) reduced hip internal rotation and knee internal rotation during the SLS (hip IR: p=0.000, knee IR: p=0.007) and the step down task (hip IR: p=0.000, knee IR: p=0.003). In addition, the PowersTM strap increased the hip internal rotation moment (p=0.000) and knee adducting moment (p=0.000) during the SLS task. The PowersTM strap decreased hip and knee internal rotation, decreased the knee valgus and increased the hip internal rotation moment as well as knee adducting moment. These results suggest that the PowersTM strap might have a strong potential to improve abnormal hip motion during leisure activities and sports in patients with lower limb injuries. Thus, the PowersTM strap should be further tested in subjects who suffer from lower limb malalignment to investigate the full potential of it and to enable an implementation for therapeutic use in future.
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