Asymmetrical strength changes and injuries in athletes training on a smallradius curve indoor track

Objectives: 1) To evaluate strength changes in the hindfoot invertor and ev ertor muscle groups of athletes training and competing primarily in the cou nterclockwise direction on an indoor, unbanked track, and 2) to observe inj uries occurring in these same runners over the course of an indoor season. Design: Prospective observational study. Setting: Fowler-Kennedy Sport Medicine Clinic, The University of Western On tario, London, Ontario. Participants: A convenience sample of 25 intercollegiate, long sprinters (2 00-600 m) and middle distance runners (800-3,000 m) competing and training with the 1995-1996 University of Western Ontario Track and Field team. Main Outcome Measures: A standardized protocol using the Cybex 6000 isokine tic dynamometer was used to measure peak torques of the hindfoot invertor a nd evertor muscle groups of both limbs using concentric and eccentric contr actions performed at angular velocities of 60, 120, and 300 degrees /sec. C hanges in peak torques between the preseason and postseason values were cal culated and compared using a repeated measures analysis of variance test. I njury reports were collected by student athletic trainers and in the Sport Medicine and Physiotherapy clinic. Results: Primary analysis indicated that the left (inside limb) inverters i ncreased in strength significantly more than the right (outside limb) inver ters (p = 0.01), while the right evertors increased in strength significant ly more than the left evertors (p = 0.04). A high incidence of lower extrem ity injury (68%) occurred in this sample of runners, corresponding to an in jury rate of 0.75 injuries per 100 person-hours of sport exposure. Although sample size was limited, secondary analysis indicated that strength change s were not significantly different for injured (n = 17) and uninjured (n = 8) runners (p > 0.05). Conclusions: The observed small, but statistically significant, asymmetrica l changes in strength of the hindfoot invertor and evertor muscle groups ca n best be described as a training effect. Altered biomechanics proposed to occur in the stance fool while running on the curve of the track are discus sed in relation to the observed strength imbalance. A causal link between s trength changes and lower extremity injuries cannot be inferred from this s tudy, but suggestions for further research are made.