Shoe cushioning reduces impact and muscle activation during landings from unexpected, but not self-initiated, drops.

OBJECTIVES To date, few rigorous scientific studies have been conducted to understand the impact mechanics and muscle activation characteristics of different landing tasks and the influence of shoe properties. The aim of this study was to examine the effects of shoe cushioning on impact biomechanics and muscular responses during drop landings. DESIGN A single-blinded and randomized design. METHODS Twelve male collegiate basketball players performed bipedal landings from self-initiated and unexpected drops (SIDL and UDL) from a 60-cm height wearing highly-cushioned basketball shoes (Bball) and less cushioned control shoes (CC). Sagittal plane kinematics, ground reaction forces (GRF), accelerations of the shoe heel-cup, and electromyography (EMG) of the tibialis anterior (TA), lateral gastrocnemius, rectus femoris (RF), vastus lateralis (VL), and biceps femoris (BF) were collected simultaneously. RESULTS In SIDL, no significant differences were observed in peak vertical GRF, peak heel acceleration, or EMG amplitude (root mean square, EMGRMS) for all muscles between the two shoe conditions. In UDL, however, both peak vertical GRF and heel acceleration were significantly lower in Bball compared to CC. Furthermore, the EMGRMS of TA, RF, VL, and BF muscles showed a significant decrease in Bball compared to CC within the 50ms after contact. CONCLUSIONS These observations suggest that shoe cushioning may make only a limited contribution to reducing landing impact forces provided that neuromuscular adjustments occur properly, as in SIDL. However, in the situation where pre-planned neuromuscular activity is reduced or absent, as in UDL, wearing a highly-cushioned shoe decreases peak impact and muscle activation in the 50ms after ground contact.