Journal of Applied Physiology, Vol 69, Issue 1 67-73, Copyright © 1990 by American Physiological Society
Exercise-induced swelling of rat soleus muscle: its relationship with intramuscular pressure
F. M. Peeze Binkhorst, D. W. Slaaf, H. Kuipers, G. J. Tangelder and R. S. Reneman
Department of Physiology, University of Limburg, Maastricht, The Netherlands.
Exercise-induced tissue swelling and its possible consequence for tissue
pressure were studied in rat soleus muscle. Rats ran for 75 min on a belt
with a 10 degree positive incline. Wet weights of cryofixed soleus muscles
were increased at 3 (16%), 6 (28%), 9 (16%), and 24 (16%) h after running
compared with those of nonexercised controls. The transient increase in
muscle wet weight correlated in time with an increase in muscle volume.
Muscle fiber swelling accounted for most of the muscle swelling in absolute
terms because of the large proportion (approximately 90%) of the muscle
volume composed of fibers, but swelling of the interstitium was about
twofold larger than fiber swelling per unit area. Muscle fiber degeneration
was most frequently found at the end of the observation period, i.e., 24 h
after running. The muscle swelling was not associated with an increase in
intramuscular pressure. During the postexercise measuring period (18 min to
24 h after exercise), intramuscular pressures of exercised rats (1.3 +/-
0.3 mm Hg) did not differ significantly from control values (1.0 +/- 0.2 mm
Hg). These findings indicate that increased intramuscular pressure is not
responsible for the muscle fiber degeneration found in rat soleus muscle 24
h after endurance running.
