Vol. 92, Issue 1, 109-116, January 2002
Effects of stimulation frequencies and patterns on
performance of repetitive, nonisometric tasks
Maikutlo B.
Kebaetse1,
Amanda E.
Turner2, and
Stuart A.
Binder-Macleod1,2
1 Interdisciplinary Programs in Biomechanics and Movement
Science, McKinly Laboratory, and 2 Department of Physical
Therapy, University of Delaware, Newark, Delaware 19107
The purpose of this paper was to
determine the effects of stimulation pattern and frequency on
repetitive human knee movements. Quadriceps femoris muscles were
stimulated against a load equal to 10% of each subject's maximum
voluntary isometric force. The main variable of interest was the number
of repetitions in which the leg reached a target angle of 40° of knee
extension. Sixteen different trains were tested, including
1) six constant-frequency trains with frequencies ranging
from 9 to 100 Hz, 2) five variable-frequency trains with an
initial 5-ms triplet and mean frequencies ranging from 11 to 35 Hz, and
3) five doublet-frequency trains, which used doublets (2 pulses with a 5-ms interpulse interval) to replace single pulses, with
mean frequencies of 17-57 Hz. Testing was stopped when the subject
failed to reach the target angle for three consecutive activations.
Results showed that no single pattern was best for all subjects. The
33- and 100-Hz constant-frequency trains, 35-Hz variable-frequency
trains, and 27- and 36-Hz doublet frequency trains each met the target
the most times for some subjects. The results showed that, under our
testing conditions, higher frequency trains were better suited for
producing repetitive knee movements than lower frequency trains.
functional electrical stimulation; doublets; variable-frequency
trains
