Leg muscle activity during walking with assistive devices at varying levels of weight bearing1

Clark BC, Manini TM, Ordway NR, Ploutz-Snyder LL. Leg muscle activity during walking with assistive devices at varying levels of weight bearing. Arch Phys Med Rehabil 2004;85:1555–60.

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±13.6y).

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.