Altered Force Ratio in Unanticipated Side Jumps After Treadmill Run

Objective: The aim was to investigate the influence of a run at the individual anaerobic threshold (IAT) on postural control in jumps with an unanticipated change of direction. Hypothesis: Dynamic postural control is less affected by the run in trained athletes than in recreational ones. Design: Controlled prospective cohort study with an intervention. Setting: Biomechanics laboratory. Participants: A total of 18 female high-level handball and volleyball players, 16 female and 8 male recreational athletes, with a mean age of 21.7 ±4.1 years. Interventions: In the jump test, the ball switch, hit above the force plate during a forward jump, triggers indicator lamps on either side. After landing on the dominant leg, a second jump 90 degrees sideways following a light signal or a stabilization in one-leg stance was required. Nine jumps (randomized order) were performed before and at 1, 5, 10, 15 and 20 min after a 30-min treadmill run at the IAT. Main Outcome Measurements: For the second jump, the ratio of the absolute values of the maximum forces in anteroposterior and mediolateral direction was calculated as a parameter of dynamic postural control in the change of direction. Results: In both groups, the force ratio increased significantly at 1 and 5 min after the treadmill run. The relative increase did not differ between groups. Dynamic postural control in transfer from a forward to a sideward jump was reduced after the run. Recovery occurred within 10 min. Conclusions: This study shows that dynamic postural control in jumps with an unanticipated change of direction is influenced by fatigue. These findings could be used to develop training programs aimed at reducing lower limb injuries in high-level ball sport athletes. The preventive effects have to be evaluated in further studies.