What this means is that someone who runs repeatedly counterclockwise on an oval track will drive skill, endurance and strength (the 3 basic tenets to solidifying a motor pattern) into the inside limb invertor muscles. This means the tibialis posterior, medial gastrocsoleus complex, flexor hallucis longus (likely) as well as some of the medial foot intrinsics. Because they are invertors, they are fighting the pronatory eversion forces on the track surface. These muscles will help to keep the ankle and foot neutral and slow the rate of foot pronation. When these muscles are weak we see posterior shin splints in the left foot/ankle early in the track season.
It is also imperative to point out that the inside foot will see more ankle (mortise) dorsiflexion and eversion and the outside ankle will be seeing more (mortise) dorsiflexion and inversion. We know that there are two heads to the tibialis anterior, one helps create more eversion and one more inversion. Do we also want to see an imbalance and experience differential there as well ? If you have been with The Gait Guys for the last 4 years you will know that we harp on symmetrical ankle rocker range and function. How can we expect to stay injury free with all this purposely driven asymmetrical skill, endurance and strength ?
Our point here is that we are driving massive asymmetry into the human track machine. As as with any machine, loosen one bolt on one side and tighten the same bold on the other side and there will be a price to pay in the function of the machine. In the short term it will be one of performance, in the slightly longer term it will be one of injury. As this study suggested, ” a high incidence of lower extremity injury (68%) occurred in this sample of runners, corresponding to an injury rate of 0.75 injuries per 100 person-hours of sport exposure. Although sample size was limited, secondary analysis indicated that strength changes were not significantly different for injured (n = 17) and uninjured (n = 8) runners (p > 0.05)”. Our response to the later statement is “give it time!”. If you are one of these track athletes and are not injured, we like to say that you are likely lucky……. for now.
Clin J Sport Med. 2000 Oct;10(4):245-50.
Asymmetrical strength changes and injuries in athletes training on a small radius curve indoor track.
1) To evaluate strength changes in the hindfoot invertor and evertor muscle groups of athletes training and competing primarily in the counterclockwise direction on an indoor, unbanked track, and 2) to observe injuries occurring in these same runners over the course of an indoor season.
Prospective observational study.
Fowler-Kennedy Sport Medicine Clinic, The University of Western Ontario, London, Ontario.
A convenience sample of 25 intercollegiate, long sprinters (200-600 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 isokinetic dynamometer was used to measure peak torques of the hindfoot invertor and evertor muscle groups of both limbs using concentric and eccentric contractions performed at angular velocities of 60, 120, and 300 degrees/sec. Changes in peak torques between the preseason and postseason values were calculated and compared using a repeated measures analysis of variance test. Injury reports were collected by student athletic trainers and in the Sport Medicine and Physiotherapy clinic.
Primary analysis indicated that the left (inside limb) invertors increased in strength significantly more than the right (outside limb) invertors (p = 0.01), while the right evertors increased in strength significantly more than the left evertors (p = 0.04). A high incidence of lower extremity injury (68%) occurred in this sample of runners, corresponding to an injury rate of 0.75 injuries per 100 person-hours of sport exposure. Although sample size was limited, secondary analysis indicated that strength changes were not significantly different for injured (n = 17) and uninjured (n = 8) runners (p > 0.05).
The observed small, but statistically significant, asymmetrical changes in strength of the hindfoot invertor and evertor muscle groups can best be described as a training effect. Altered biomechanics proposed to occur in the stance foot while running on the curve of the track are discussed in relation to the observed strength imbalance. A causal link between strength changes and lower extremity injuries cannot be inferred from this study, but suggestions for further research are made.