Decreasing landing forces in children: The effect of instructions

Study Design: Randomized controlled experimental design. Objectives: To examine the effects of verbal instructions related to control of joint kinematics and auditory feedback on lowering the vertical peak ground reaction forces associated with landing from a jump in children. Background: The majority of children's injuries are associated with activities that involve jumping and landing. Instructions related to joint motion may assist children in decreasing landing forces and thus reduce the chances of sustaining an injury. Methods and Measures: Sixty-one school children whose mean (+/-SD) age was 9 (+/-0.89) years participated. The children were randomly assigned (by school) to either experimental (received instruction on lower limb position and auditory cues) or control (received no instruction) groups. Participants were required to step off a box 300 mm in height and land on a force plate. The testing procedure involved 5 sessions. The first 4 sessions were performed over 3 days in the same week, while session 5 was performed approximately 3 months later to assess retention of the skill. The main outcome measure was the peak vertical ground reaction force recorded at foot strike. Results: After instructions, subjects in the experimental group produced lower peak ground reaction forces (P<0.05) during landing compared to their control counterparts (ie, sessions 24). There was no significant difference (P<0.05) between groups at session 5 (3 months postinstruction). Conclusions: Children are capable of assimilating precise instruction to minimize forces on the lower limbs during landing from a jump. Providing further opportunity (ie, more than 1 session) to perform the skill does not alter the magnitude of the effect observed after the initial session of instruction. However, the improvements in landing performance were temporary.