Coactivation and peak torque of extensors and flexors knee muscle in chronic hemiparetics in sitting and supine positions

ABSTRACT

Disorders in co-activation and decreased muscle strength are often described in hemiparetic subjects. Changes in muscle length resulting from postural change may result in different responses of co-activation and strength of these individuals. The objective of this study was to evaluate the influence of sitting and supine positions in Co-activation Index (CI) and peak torque (PT) of chronic hemiparetic subjects after stroke. The participants were twenty individuals with mean age of 54±12.14 years; mean body mass index of 26.93±3.34 kg/m²; average stroke time of 55.85±49.4 months; Mini-Mental State Examination score between 27-30; and Fugl-Meyer of lower limb between 15-30. The electromyographic record was obtained while the volunteers performed five isokinetic contractions (60º/s) of knee extension and flexion in the sitting and supine positions. The semitendinosus muscle of paretic limb exhibited lower CI in the supine position compared to sitting: 0.36±0.33; 0.44±0.33 (p=0.048). There was no difference in CI of the rectus femoris between positions: 0.28±0.25 sitting and 0.23±0.21 supine. The PT of extensor and flexor muscles of the paretic limb did not vary between positions (PT extensor: sitting = 56.48±37.62 Nm, supine = 52.29±32.37 Nm; PT flexor: sitting = 12±11.1 Nm, supine = 10.95±6.4 Nm). The supine position showed lower CI in the semitendinosus muscle of paretic limb. The change of position did not influence the CI of rectus femoris muscle neither the PT of both muscle groups of the paretic limb. Thus, the supine position appears to be indicated during movement and strength training of these muscles in chronic hemiparetic patients after stroke.

Keywords:
Stroke; Muscle Strength; Electromyography