Effect of graded ankle immobilization on toe push-down strength and muscle activity

Introduction The graded ankle immobilization may affect muscle strength and agonist muscle activity during toe push-down. Therefore, in this study, we evaluated how the modification of ankle immobilization affected toe push-down strength and agonist muscle activity. Method We investigated the dominant foot of 21 healthy adult men using a custom-made measurement instrument, an ankle immobilization belt with adjustable immobilization, and surface electromyography. The subject muscles were the abductor hallucis (ABDH), flexor hallucis longus (FHL), tibialis anterior, and soleus (SOL). We measured the muscle activity and great toe push-down strength (GTPS) under five immobilization conditions: 0 (no immobilization), 20, 40, 60, and 80 mmHg. Finally, we calculated and compared the GTPS, muscle activity of each muscle, and the ABDH/FHL muscle activity ratio for each condition. Results The GTPS was significantly higher at 40, 60, and 80 mmHg than at 0 mmHg. It was also significantly higher at 80 mmHg than at 40 and 60 mmHg. FHL activity increased significantly at 40 mmHg and higher, whereas SOL activity increased at 60 mmHg and higher. The ABDH/FHL activity ratio was significantly greater at 0 mmHg than at 40 mmHg and above. It was also greater at 20 mmHg than at 80 mmHg. These results indicate that graded ankle immobilization affects the GTPS and FHL activities. Conclusion Our findings demonstrate that graded ankle immobilization influences the GTPS and FHL activities. This suggests that consideration of graded ankle immobilization levels may help minimize measurement errors in GTPS.