BACKGROUND:

Hemiparesis causes a reduction in neuromuscular structure and function and affects the contractile properties of the plantar flexors.

OBJECTIVE:

To compare the triceps surae volume, activation and mechanical properties in hemiparetic stroke survivors to those of healthy subjects.

METHODS:

Twelve hemiparetic stroke survivors (mean age, 62 years) and twelve healthy subjects (mean age, 60 years) participated in the study. The triceps surae muscle volume was estimated by ultrasound and anthropometric data. Plantar flexor muscle activation and dorsiflexor co-activation were measured with surface electromyography, and isometric plantar flexor moment was measured with an isokinetic dynamometer. Muscle quality was determined by the moment/muscle volume ratio. One-way ANOVA was used for between-groups comparisons (α = 0.05).

RESULTS:

The paretic and non-paretic limbs of stroke survivors showed smaller muscle volume (∼ 36% and ∼ 35%, respectively) than the dominant limb of healthy subjects (p< 0.01). The muscle quality was similar between the non-paretic limb and the dominant limb of healthy subjects (p> 0.05) but was lower in the paretic limb (p< 0.05). Peak moment was lower (∼ 61%) in the paretic and non-paretic (∼ 33%) limbs compared to the dominant limb of healthy subjects (p< 0.01). The paretic limb showed lower gastrocnemius medialis activation than did the non-paretic (∼ 45%) and dominant (∼ 33%) limbs of healthy subjects (p< 0.01).

CONCLUSION:

Structural and functional losses are higher in the paretic than in the non-paretic limb and in the non-paretic compared to a healthy limb.