Lower extremity biomechanics and muscle activity differ between 'new' and 'dead' pointe shoes in professional ballet dancers.

The purpose of this study was to compare lower extremity (LE) biomechanics and muscle activity between 'new' and 'dead' pointe shoes in professional female ballet dancers performing relevé and arabesque. We compared sway area, peak ankle moments, and tibialis anterior and medial gastrocnemius muscle activation amplitudes. Nine ballet dancers participated (age = 22.2 ± 2.2 years, height = 163.2 ± 6.3 cm, body mass = 50.8 ± 6.5 kg) executed three trials of relevé and arabesque on pointe shoes under two conditions: 'dead' (108-144 training hours) and 'new' (3-36 training hours). While wearing 'dead' pointe shoes, dancers had significantly higher sway area during both relevé and arabesque (p = 0.017 and 0.028, respectively). Dancers exhibit significantly higher tibialis anterior activation (root mean square, %maximum voluntary contraction) during arabesque while wearing 'dead' pointe shoes (p = 0.043). No significant differences were identified in other dependent variables. The increased sway area and tibialis anterior muscle activity when wearing 'dead' pointe shoes during relevé and arabesque movements demonstrates that using 'dead' shoes is more demanding. Our findings provide quantitative evidence of possible deleterious biomechanical changes when wearing dead pointe shoes that may increase LE injury risk in dancers.

The Effect of Foam Rolling of the Hamstrings on Proprioception at the Knee and Hip Joints.

The purpose of this study was to determine the acute effect of hamstring foam rolling on proprioception at the knee and hip joints. Twenty-five participants completed two proprioceptive tests on separate days, in a random order. The joint position matching test used no visual feedback. Participants were verbally guided to a target lunge position, which was maintained for six seconds while right hip and knee angles were recorded. After rest, participants reproduced this position without guidance for six seconds. Three trials were completed at baseline, and zero, 10, and 20 minutes post-intervention. In the force matching test, participants completed three trials with feedback about force output from a graph, and three trials without. They gradually applied knee flexion force against the dynamometer until reaching target force output. This test was also completed at baseline, and zero, 10, and 20 minutes post-intervention. A significant main effect was found for absolute knee position matching error (F(1.97, 47.36), p = 0.004). No significant differences were found between post-intervention values at zero and 10 minutes, zero and 20 minutes, or 10 and 20 minutes for absolute hip position matching error or absolute knee force matching error at zero, 10, or 20 minutes (p > 0.05). Foam rolling improved knee joint position sense for at least 20 minutes post-intervention, and did not decrease hip joint position sense or knee joint force sense. This indicates that foam rolling may be used immediately prior to exercise without the risk of injury due to proprioceptive deficits.