Faculty Collaboration Database

Elastic, viscous, and mass load effects on poststroke muscle recruitment and co-contraction during reaching: a pilot study. Phys Ther 2009 Jul;89(7):665-78

Date

05/16/2009

Pubmed ID

19443557

Pubmed Central ID

PMC2704029

DOI

10.2522/ptj.20080128

Scopus ID

2-s2.0-67649817339 (requires institutional sign-in at Scopus site)   22 Citations

Abstract

BACKGROUND: Resistive exercise after stroke can improve strength (force-generating capacity) without increasing spasticity (velocity-dependent hypertonicity). However, the effect of resistive load type on muscle activation and co-contraction after stroke is not clear.

OBJECTIVE: The purpose of this study was to determine the effect of load type (elastic, viscous, or mass) on muscle activation and co-contraction during resisted forward reaching in the paretic and nonparetic arms after stroke.

DESIGN: This investigation was a single-session, mixed repeated-measures pilot study.

METHODS: Twenty participants (10 with hemiplegia and 10 without neurologic involvement) reached forward with each arm against equivalent elastic, viscous, and mass loads. Normalized shoulder and elbow electromyography impulses were analyzed to determine agonist muscle recruitment and agonist-antagonist muscle co-contraction.

RESULTS: Muscle activation and co-contraction levels were significantly higher on virtually all outcome measures for the paretic and nonparetic arms of the participants with stroke than for the matched control participants. Only the nonparetic shoulder responded to load type with similar activation levels but variable co-contraction responses relative to those of the control shoulder. Elastic and viscous loads were associated with strong activation; mass and viscous loads were associated with minimal co-contraction.

LIMITATIONS: A reasonable, but limited, range of loads was available.

CONCLUSIONS: Motor control deficits were evident in both the paretic and the nonparetic arms after stroke when forward reaching was resisted with viscous, elastic, or mass loads. The paretic arm responded with higher muscle activation and co-contraction levels across all load conditions than the matched control arm. Smaller increases in muscle activation and co-contraction levels that varied with load type were observed in the nonparetic arm. On the basis of the response of the nonparetic arm, this study provides preliminary evidence suggesting that viscous loads elicited strong muscle activation with minimal co-contraction. Further intervention studies are needed to determine whether viscous loads are preferable for poststroke resistive exercise programs.

Author List

Stoeckmann TM, Sullivan KJ, Scheidt RA

Authors

Robert Scheidt BS,MS,PhD Associate Professor in the Biomedical Engineering department at Marquette University
Tina Stoeckmann PT, DSc, MA Associate Clinical Professor & Neurologic PT Residency Program Coordinator in the Physical Therapy department at Marquette University

MESH terms used to index this publication - Major topics in bold

Adaptation, Physiological
Aged
Arm
Elasticity
Elbow
Female
Hemiplegia
Humans
Male
Middle Aged
Muscle Contraction
Muscle, Skeletal
Paresis
Pilot Projects
Range of Motion, Articular
Recovery of Function
Recruitment, Neurophysiological
Shoulder
Stress, Mechanical
Stroke
Stroke Rehabilitation
Task Performance and Analysis
Viscosity
Weight-Bearing