Article

OBJECTIVE: To compare paralyzed quadriceps force properties and femur compressive
loads in an upright functional task during conventional constant-frequency stimulation and force feedback-modulated stimulation. DESIGN: Crossover trial.
SETTING: Research laboratory. PARTICIPANTS: Subjects (N=13; 12 men, 1 woman) with
motor-complete spinal cord injury. INTERVENTIONS: Subjects performed 2 bouts of
60 isometric quadriceps contractions while supported in a standing frame. On
separate days, subjects received constant-frequency stimulation at 20Hz (CONST)
or frequency-modulated stimulation triggered by a change in force (FDBCK). During
FDBCK, a computer algorithm responded to each 10% reduction in force with a 20%
increase in stimulation frequency. MAIN OUTCOME MEASURES: A biomechanical model
was used to derive compressive loads on the femur, with a target starting dose of
load equal to 1.5 times body weight. RESULTS: Peak quadriceps force and fatigue
index were higher for FDBCK than CONST (P<.05). Within-train force decline was
greater during FDBCK bouts, but mean force remained above CONST values (P<.05).
As fatigue developed during repetitive stimulation, FDBCK was superior to CONST
for maintenance of femur compressive loads (P<.05). CONCLUSIONS:
Feedback-modulated stimulation in electrically activated stance is a viable
method to maximize the physiologic performance of paralyzed quadriceps muscle.
Compared with CONST, FDBCK yielded compressive loads that were closer to a
targeted dose of stress with known osteogenic potential. Optimization of muscle
force with FDBCK may be a useful tactic for future training-based
antiosteoporosis protocols.
CI - Copyright (c) 2011 American Congress of Rehabilitation Medicine. Published by
Elsevier Inc. All rights reserved.

Langue : ANGLAIS