Faculty Collaboration Database

Contractile responses of the rat gastrocnemius and soleus muscles to isotonic resistance exercise. J Appl Physiol (1985) 2004 Dec;97(6):2322-32

Date

08/24/2004

Pubmed ID

15322071

DOI

10.1152/japplphysiol.00955.2003

Scopus ID

2-s2.0-9244238161 (requires institutional sign-in at Scopus site)   21 Citations

Abstract

Male rats were divided into control and weight-trained (WT) groups. WT rats performed squat-type exercises twice daily, 5 days/wk, for 14 wk. They averaged 36 lifts/day, with an average weight of 555 g. Muscle-to-body weight ratio (mg/g) of the soleus (Sol) was not different from control, but it increased 11 and 6% in the gastrocnemius (Gast) and plantaris, respectively (P < 0.05). The normalized twitch tension of the in situ Sol was elevated by 21%, whereas single-skinned type I fibers from the Sol showed an increased rate constant of tension redevelopment (K(tr)) but no other contractile adaptations to WT. In contrast, the Gast type I fibers showed an increase (P < 0.05) in maximal velocity of shortening (25%), peak power (15%), K(tr) (18%), and normalized tension (7%). The K(tr) and normalized tension of the Gast type IIa fibers increased by 24% (P < 0.05) and 12% (P < 0.05), respectively, whereas velocity and power showed a tendency to increase. Fiber size, determined by myosin ATPase histochemistry, was not different for any fiber type from the Gast or Sol. These results indicate that isotonic resistance exercise of the calf targets the Gast (type I and type IIa fibers) and has little effect on the Sol.

Author List

Norenberg KM, Fitts RH

Author

Robert Fitts PhD Professor in the Biological Sciences department at Marquette University

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

Animals
Body Weight
Isotonic Contraction
Male
Muscle Fibers, Fast-Twitch
Muscle Fibers, Slow-Twitch
Muscle, Skeletal
Organ Size
Physical Exertion
Rats
Rats, Sprague-Dawley