Leg muscle activity during walking with assistive devices at varying levels of weight bearing

OBJECTIVE: To evaluate the muscle activation patterns at varying levels of weight-bearing forces during assisted walking with an axillary crutch and a recently designed device that allows weight transfer through the pelvic girdle (ED Walker). DESIGN: Descriptive, repeated measures. SETTING: University-based research laboratory. PARTICIPANTS: Twelve healthy volunteers (age, 39.6+/-13.6 y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Electromyographic activity was recorded from the anterior tibialis, soleus, biceps femoris, and vastus lateralis muscles on a test leg during assisted axillary crutch and ED Walker ambulation. Force platform readings measured weight-bearing load (non, light, heavy). These values were normalized to normal walking gait. RESULTS: In the vastus lateralis and soleus muscles, both devices allowed for approximately 50% and 65% reductions in electromyographic activity during the non-weight-bearing condition. During crutch ambulation, electromyographic activity of the soleus was significantly reduced compared with that required for normal walking at all levels of weight-bearing load. In the vastus lateralis for the weight-bearing conditions, the ED Walker required significantly higher electromyographic activity than crutch ambulation (light: 105.0%+/-12.3% vs 72.7%+/-10.1%; heavy: 144.8%+/-23.5% vs 100.0%+/-13.5%). Both devices required similar peak vertical ground reaction forces during the heavy weight-bearing conditions (crutch: 75%+/-1.6%; ED Walker: 73%+/-1.8%), whereas axillary crutch gait produced less force than the ED Walker in the light condition (32%+/-2.0% vs 48%+/-1.6%). CONCLUSIONS: During walking with assistive devices, muscle activation patterns varied with weight-bearing load. The leg extensor muscles appeared to incur a greater reduction in muscle activity when compared with their flexor counterparts. Additionally, the ED Walker and axillary crutch differed with respect to their muscle activity levels and weight-bearing characteristics. Clinically, knowledge of these muscle activity and force characteristics may aid in the decision-making process of prescribing a device type and timeline to follow in restoring weight-bearing loads.