AN EMG ANALYSIS OF MUSCLE ACTIVATION PATTERNS DURING

TREADMILL AND FLOOR WALKING

O’Dell W, Dietz L, McCarter M,  Robbins J, Svalina S

Clarke College, Dubuque, Iowa

PURPOSE:  Patients with low back pain are often instructed on exercise programs which include treadmill or floor walking. This study examined variation of the muscle activation pattern of the lumbar paravertebral, external oblique, and biceps femoris muscles in subjects with no known pathology in floor walking and three different speeds on a treadmill. SUBJECTS: Ten female subjects without low back pain, aged 18 to 23 years participated in this study. METHODS: A maximal voluntary isometric contraction (MVIC) of external obliques, lumbar paravertebrals, and biceps femoris was performed by each subject and recorded by surface electromyography (EMG). EMG measurements were taken for these same muscles during floor walking at a self-selected speed and for three treadmill speeds (self-selected, 2.9 mph, 4.4 mph). A heel switch was placed in the right shoe of each participant, which marked the heel strike of each gait cycle.

RESULTS: Raw EMG data from MVIC and at heelstrike in each walking condition was converted to root mean square for statistical analysis. ANOVA results showed that within subjects, there was a significant difference of EMG data among the six muscles (F=3.13, p=0.020).  A significant difference was also detected between the walking conditions (F=6.04, p0.003).  No significant muscle by condition interaction was determined. Intraclass Correlation Coefficient of EMG data selected from two separate gait cycles for each participant showed good reliability of the right and left paraspinals and right and left obliques during floor walking. Poor reliability was found for the biceps femoris bilaterally. During treadmill walking, poor reliability was found in all muscle groups except for the left external oblique.

CONCLUSIONS: Results suggest that on average, the six muscles did not fire differently when walking on the floor compared to walking on a treadmill at similar speeds.  However, muscle EMG activity differed from one gait cycle to the next within the same subject when walking on the treadmill. Differences detected in the reliability study imply that there may be variations in muscle firing across gait cycles during treadmill walking that are not present when walking on the floor at a similar speed. CLINICAL RELEVANCE: Studies have demonstrated that unexpected loads generate complex patterns of spinal response.  These loading patterns may pose an increased risk of injury. The results of this study suggest that treadmill walking generate variations in muscle activation. This variation may be inappropriate for some patients.  

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