Electromyographic and Motion Analysis of Forward and Backward Walking

Sarah Badding, Lori Guderian, Kerry Hendricksen, Glenda Scott and Thomas Mohr

ABSTRACT

Purpose:  The purpose of this project is to describe muscle activity (EMG) and range of motion (ROM) while walking both forward and backward on a treadmill at various inclines.  Subjects.  Eighteen, health male subjects participated in the study.  Methods.  Surface electromyography (EMG) activity was recorded from the vastus lateralis, vastus medialis, biceps femoris and semitendinosus.  Reflective markers were placed on the iliac crest, greater trochanter, fibular head and lateral malleolus.  Footswitches were used to determine the phase of the gait cycle.  Data was collected while each subject walked both forward and backward on the treadmill at 3.5 mph at 0% and 15% grades.  Results.  There was an increase in EMG activity in all the muscles at the 15% incline for both forward and backward walking.  The greatest increase in activity (for all the muscles) was with backward walking at a 15% incline.  Conclusion.  Overall, our results indicated a greater increase in muscle activity during backward walking than forward walking, and greater muscle activity when walking on an incline as compared to level. 

PURPOSE

Currently there is a limited amount of research available to attest to the efficacy of rehabilitation techniques with FW and BW on a treadmill.  Although some research exists regarding forward and backward walking with EMG analysis, there is a need to evaluate whether differences, if any, occur in muscle EMG activity at various inclines as well as direction.  The purpose of this project is to describe muscle activity and range of motion (ROM) while walking both forward and backward on a treadmill at various inclines. 

Methods  

Subjects.  Eighteen, healthy, male subjects ages 20-31 participated in this study.  Instrumentation.  The EMG data was collected on a Noraxon Telemyo8 system.  The motion analysis data was collected using the Peak Motus System.  Procedure.  The muscles analyzed included the (1) vastus lateralis(VL), (2) vastus medialis (VM), (3) biceps femoris(BF), and (4) semitendinosus (St).  A ground electrode was applied over the superior medial tibial plateau.  Reflective markers were placed on the iliac crest, greater trochanter, head of the fibula, and the lateral malleolus of each subject.  Footswitches were used to determine the phase of the gait cycle.  The subjects were given a one-minute warm-up trial prior to testing at 0 and 15% grades for both forward and backward walking to become familiarized with treadmill use.  Data was then collected in 10-second intervals while walking at 3.5 mph at 0% and 15% grades in both directions.  Data Analysis.  The EMG data was normalized to forward walking at 0% grade.  The normalization procedure was performed using the following formula: 

% change in EMG activity = (EMG during trial) – (EMG during FW at 0% grade)

                                                 EMG during FW at 0% grade

Repeated measures Analysis of Variance (ANOVA) was used to compare the muscle activity during the different inclines and directions.

RESULTS

Muscle Activity Table 1 shows the descriptive statistics of the percent change in EMG activity of the muscles during the walking trials of forward 15, backward 0, and backward 15 as compared to the baseline EMG activity during forward 0.  There were increases in EMG activity in all walking trials as compared to forward 0.  In all muscles, the greatest increase in activity was during the backward 15 walking trial.  The lowest change in activity was found during forward 15 for all muscles except the biceps femoris, which had the lowest activity during backward 0.  Figures 1 and 2 depict the EMG activity during the walking trials (significant differences noted by asterisks).  EMG activity for all of the muscles was increased when comparing forward 15, backward 0, and backward 15 walking trials to forward 0.

Table 1. Descriptive Statistics showing changes in EMG activity during walking.

Vastus Medialis.  A significant increase in EMG activity was found between backward walking at 15 percent compared to backward walking at 0 percent and forward walking at both 0 and 15 percent.  Vastus Lateralis.  A significant increase in EMG activity was found between backward walking at 15 percent compared to backward walking at 0 percent and forward walking at both 0 and 15 percent.  Biceps Femoris.  A significant increase in EMG activity was found between backward walking at 15 percent compared to forward walking at 0 percent.  There was no significant difference in biceps femoris activity between backward and forward walking at a 15 percent incline or backward at 0 percent.  Semitendinosus.  A significant increase in EMG activity was found between backward walking at both 0 and 15 percent compared to forward walking at 0 percent.

Range of Motion.  Average knee flexion angles for the subjects are displayed in Table 2. When knee flexion angles were compared between walking trials, backward 15 required the greatest range of knee motion, followed by forward 15, forward 0, and backward 0, respectively.

Table 2. Average Knee flexion angles during walking trials.

CONCLUSION

We found increased muscle activity in backward walking as compared to forward walking.  The vastus lateralis showed the largest percent increase in muscle activity (relative to forward walking) during backward walking.  We also found that inclined walking, both forward and backward, increases EMG activity of the vastus lateralis, vastus medialis, biceps femoris, and semitendinosus.  The greatest activity for all muscles analyzed was seen during backward walking at a 15% grade.  Although the degree of knee flexion during walking was similar between trials, the greatest amount of knee flexion was seen with backward walking at 15% grade.