Exploring the differences in muscle activation of unilateral transtibial amputees during rehabilitation exercises and walking

Unilateral transtibial amputees (UTTA) often experience biomechanical and neuromuscular asymmetry during daily activities1–3. Task complexity has been suggested as a contributing factor to this asymmetry4. The use of a prosthesis during gait-related daily activities requires additional energy expenditure compared to a biological limb and as such muscle strength and biomechanical efficiency are important5. Understanding the differences in muscle activity during different activities could add further insights. How does muscle activation differ between exercises used during rehabilitation and walking in a population of UTTA? Ten UTTA (41 ± 12 years, 7 men & 3 women) performed a combination of exercises including self-paced walking (SPW), walking (4 km/hr), glute bridge, squat, and sit-to-stand (SiSt). Muscle activation of 10 muscles (Unaffected side (UN): tibialis anterior (TA), medial gastrocnemius (MG). Affected (AF) & UN sides: vastus lateralis (VL), bicep femoris (BF), gluteus maximus (GMax) and lumbar erector spinae (LES)) were recorded using surface electromyography (EMG) (Noraxon, USA). Raw EMG data were filtered using a high pass, eighth-order Butterworth bidirectional filter at 20 Hz and a low pass Butterworth filter at 450 Hz. EMG recordings were full wave rectified and filtered using a bandpass eighth-order Butterworth filter between 20 - 200 Hz. Signals were smoothed using the root mean squared with a 50ms window6. Data were normalised to the SPW trial per participant7. Repeated measures ANOVAs were calculated for each muscle over the five activities. Ethical clearance and consent were attained prior to testing. Statistically significant differences were found in the muscle activation between the different activities for all muscles (p<0.05) except the GMax(AF). The SPW had higher average activation (range=20-75%) than the walking and glute bridge activities, and during the squat and SiSt for the TA (69 & 46% respectively), MG (70 & 59%), GMax (UN=66%; UN=48%) and BF (UN=27 & AF=46%) muscles. The 4 km/hr walk had significantly higher average activation of the TA (42%), MG (52%), GMax (UN=36%), and BF (UN=38%, AF=42%) than the squat, however, significantly lower activation of the VL (UN=-107%) compared to the squat and MG (41%) during the SiSt. The SiSt had greater activation of the VL (UN=68%, AF=88%) compared to the glute bridge. While not significant, mean activations were highest for LES(AF) and VL(UN) during the SiSt compared to all other activities. Self-paced walking had the highest average muscle activation for most of the muscles compared to the other exercise activities. Based on these results, the choice of exercises should be based on the phase of rehabilitation. Where asymmetry has been detected the focus of the exercise could be on strength development of specific muscle groups. Self-paced walking as a daily activity with progressions and cues can be regarded as an effective training modality within this population.