Crouch gait can be an effective form of forced-use/no constraint exercise for the paretic lower limb in stroke

Abstract

In hemiplegic gait the paretic lower limb provides less muscle power and shows a briefer stance compared with the unaffected limb. Yet, a longer stance and a higher power can be obtained from the paretic lower limb if gait speed is increased. This supports the existence of a 'learned non-use' phenomenon, similar to that underlying some asymmetric impairments of the motion of the eyes and of the upper limbs. Crouch gait (CG) (bent-hip bent-knee, about 30° minimum knee flexion) might be an effective form of 'forced-use' treatment of the paretic lower limb. It is not known whether it also stimulates a more symmetric muscle power output. Gait analysis on a force treadmill was carried out in 12 healthy adults and seven hemiplegic patients (1-127 months after stroke, median: 1.6). Speed was imposed at 0.3 m/s. Step length and single and double stance times, sagittal joint rotations, peak positive power, and work in extension of the hip, knee, and ankle (plantar flexion), and surface electromyography (sEMG) area from extensor muscles during the generation of power were measured on either side during both erect and crouch walking. Significance was set at P less than 0.05; corrections for multiplicity were applied. Patients, compared with healthy controls, adopted in both gait modalities and on both sides a shorter step length (61-84%) as well as a shorter stance (76-90%) and swing (63-83%) time. As a rule, they also provided a higher muscular work (median: 137%, range: 77-250%) paralleled by a greater sEMG area (median: 174%, range: 75-185%). In erect gait, the generation of peak extensor power across hip, knee, and ankle joints was in general lower (83-90%) from the paretic limb and higher (98-165%) from the unaffected limb compared with control values. In CG, peak power generation across the three lower limb joints was invariably higher in hemiparetic patients: 107-177% from the paretic limb and 114-231% from the unaffected limb. When gait shifted from erect to crouch, only for hemiplegic patients, at the hip, the paretic/unaffected ratio increased significantly. For peak power, work, sEMG area, and joint rotation, the paretic/unaffected ratio increased from 55 to 85%, 56 to 72%, 68 to 91%, and 67 to 93%, respectively. CG appears to be an effective form of forced-use exercise eliciting more power and work from the paretic lower limb muscles sustained by a greater neural drive. It also seems effective in forcing a more symmetric power and work from the hip extensor muscles, but neither from the knee nor the ankle.

Fig. 1

Percent ratio of body weight loading on the lower limbs during standing (0°) and with knee flexed at 30°, 60°, and 90°. White and black columns refer to the unaffected and paretic side of seven hemiparetic patients, respectively (+SD). At all angles, the pairwise comparisons between the lower limbs were significant at P<0.05, with Bonferroni correction (see Methods section).

Fig. 2

(a) The curves show the grand-mean of six subsequent strides performed by 12 healthy adults during erect (left panels) and crouch gait (right panels) on a force treadmill, right step first, at a speed of 0.3 m/s. On the abscissa, the standardized stride time is given. The bottom horizontal bar shows the stance time (average+SD between the two lower limbs). Dashed and filled segments represent the average time of the single and the double stance phases, respectively. From top to bottom, the curves show the power (in W/kg), the surface electromyography (sEMG) from the extensor muscles (gluteus maximus), and the sagittal joint excursion (hip extension downward, see ‘ext’ arrow). The shaded areas and the thickened lines mark the stride phases when power is generated or positive (see ‘gen’ arrow and Table 3). (b) Replication of the information for an average of seven hemiplegic patients. The red and black colors refer to the paretic and the unaffected lower limb, respectively.

Fig. 3

The panels replicate the information shown in (a) healthy controls and (b) hemiplegic patients. The variables refer to the knee joint and the surface electromyography (sEMG) signal from the rectus femoris.

Fig. 4

The panels replicate the information shown in (a) healthy controls and (b) hemiplegic patients. The variables refer to the ankle joint and the surface electromyography (sEMG) signal from the lateral Gastrocnemius.

Fig. 5

From top to bottom, the panels refer to (a) hip, (b) knee, and (c) ankle joints, respectively. The ordinate shows the % ratio of the mean values recorded from the paretic and the unaffected side, shown in Tables 3–5. White and black bars refer to erect and crouch gait, respectively. In all panels, each pair of bars refers to one of the parameters shown in the abscissa [peak power, work, surface electromyography (sEMG) area, joint excursion, and rotation speed, all computed while positive power is generated]. Asterisks mark the significant pairwise comparisons (P<0.05, Bonferroni correction for multiplicity; see Methods section).