A multi-mode dynamometer for in vivo mrs studies of human skeletal
muscle.
Ryschon, Timothy W., Mark D. Fowler, Andrew A. Arai, Robert E. Wysong,
Stephen B. Leighton, Thomas R. Clem Sr. and Robert S. Balaban.
Laboratory of Cardiac Energetics, NHLBI and Biomedical Engineering
and Instrumentation Program, NCRR, National Institutes of Health,
9000 Rockville Pike, Bethesda, MD 20892
APStracts 2:0376A, 1995.
The implementation of muscle ergometry during magnetic resonance
spectroscopy and imaging is complicated by the restrictive dimensions
of the magnet bore and the presence of a strong, static magnetic
field. We have developed a dynamometer that is compatible with these
constraints. This device can provide resistance to voluntary muscle
contraction during isometric, isokinetic concentric, and isokinetic
eccentric muscle contraction. While controlling muscle contraction
speed, the dynamometer simultaneously records muscle torque
production at a 10 Hz sampling frequency to allow assessment of
compliance and retrospective normalization of power output for the
mass of active muscle. All parameters relevant to muscle contraction
are selectable, including: percentage of maximal voluntary
contraction, velocity of muscle contraction, duty cycle, and range of
motion for the contraction. This paper provides examples of 31P-MRS
measurements during isokinetic concentric contractions of the ankle
dorsiflexors, isokinetic eccentric contractions of the soleus, and
isometric contractions of the soleus. Operation of the dynamometer
has no adverse affects on the integrity of the 31P-MR spectra at 4
tesla, permitting temporal resolution of phosphocreatine (PCr)
resynthesis rate of 1 sec-1. The unique capabilities of this
dynamometer will facilitate studies into the metabolic response of
working muscle in healthy and diseased populations.
Received 3 April 1995; accepted in final form 17 July 1995.
APS Manuscript Number A370-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 15 September 1995.