Affiliations: [a] Exercise Research Laboratory, School of Physical Education, Physical Therapy and Dance, Federal University of Rio Grande do Sul, Porto Alegre, Brazil | [b] School of Physical Education, Faculty of Serra Gaúcha, Caxias do Sul, Brazil | [c] Neurology Service, São Lucas Hospital, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, RS, Brazil | [d] Biomedical Gerontology and Neurology Department, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, RS, Brazil
Correspondence:
[*]
Corresponding author: Marco Aurélio Vaz, Exercise Research Laboratory, School of Physical Education, Physical Therapy and Dance, Federal University of Rio Grande do Sul, Rua Felizardo, 750, CEP 90690-200, Porto Alegre, RS, Brazil. Tel.: +55 51 33085860; E-mail:marco.vaz@ufrgs.br
Abstract: 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.
