This study compared trunk and lower extremity muscle activity during SLR in ICCI patients, according to their levels of walking independence at discharge or transfer from an acute-care hospital.
Thirty-four patients who acquired both left and right SLR after admission were included. They were classified into the non-independent and independent groups based on Mobility Indoors of the Spinal Cord Independence Measure at discharge or transfer. Patients performed SLR three times on each side, holding the leg at 30 degrees for 10 seconds. We measured accelerations using inertial sensors and calculated combined accelerations for the pelvis, thighs, and lower legs. Additionally, we calculated normalized root mean square (RMS) as an indicator of muscle activity amplitude and median frequency as a marker of muscle fatigue from surface electromyography in 10 muscles: ipsilateral rectus femoris, contralateral biceps femoris, bilateral rectus femoris, internal oblique, external oblique, and lumbar multifidus. Data were averaged every second during each SLR for the dominant and non-dominant legs. The mean of the three trials for each side was analyzed using a split-plot factorial design, with two factors: group (between-subject) and time (within-subject as repeated measures).
We analyzed 14 patients in the non-independent group and 20 in the independent group. The lower extremity muscle strength was significantly higher in the independent group than in the non-independent group (P0.01). Combined accelerations did not differ between groups at any site. During non-dominant SLR, the median frequency of the contralateral biceps femoris showed a significant main effect of group (P0.05) and was higher in the independent group. The RMS values of the contralateral internal and external obliques also showed a significant main effect of group (P0.05 and P0.01) and were higher in the non-independent group. During dominant SLR, only the RMS of the contralateral external oblique showed a significant main effect of group and interaction (both P0.01) and was higher in the non-independent group.
These results indicate that muscle activity during SLR varies by walking independence, despite similar accelerations: the independent group primarily mobilized the contralateral biceps femoris, while the non-independent group engaged contralateral trunk muscles to compensate for lower extremity weakness. Future studies should measure psoas major muscle activity, which has been reported to mobilize bilaterally during SLR, and include healthy older adults to further clarify the effects of ICCI.
In ICCI patients, trunk muscle activity should be assessed through palpation or electromyography, even if they can perform SLR. These findings could inform standard assessment practices in rehabilitation.
Straight-leg raising
Muscle activity
