Context: Ankle plantarflexion is thought to play an important role in swimming performance; thus, coaches and swimmers often seek ways to increase range of motion (ROM) in the ankles.

Objective: To assess whether osteopathic manipulative treatment (OMT), specifically applying the muscle energy technique (MET) principle of post–isometric relaxation, increases ankle plantarflexion and therefore improves swimming performance.

Methods: Healthy young male and female competitive swimmers were randomly assigned to either a control, sham, or MET group. At baseline, ankle plantarflexion was measured via goniometer, and a 25-yard flutter kick swim with a kickboard was timed. After receiving the ascribed intervention, the ankle plantarflexion measurements and timed flutter kick were repeated. The initial plantarflexion measurement was retrospectively used to determine the presence of somatic dysfunction, by way of restricted motion, with reference to expected normal ranges based on age and gender. Paired t tests were used to analyze the pre- to postintervention changes in ROM and flutter kick speed within each group.

Results: Fifty-five swimmers (32 girls and 23 boys; mean age, 12 years) participated in this study. Sixteen participants were in the control group, 17 in the sham group, and 22 in the MET intervention group. Among participants with restricted ROM, those in the MET group showed a statistically significant increase in ankle plantarflexion for the left and right ankles (P=.041 and P=.011, respectively). There was no significant difference in ROM of the control or sham groups. For flutter kick speed, there was no significant pre- to postintervention difference in any group.

Conclusion: Although a single application of MET, using post–isometric relaxation, on participants with restricted ROM immediately significantly increased swimmers’ ROM for bilateral ankle plantarflexion, it did not immediately improve their swimming performance.