Hindlimb unloading-induced muscle atrophy and loss of function: protective effect of isometric exercise. J Appl Physiol (1985) 2003 Oct;95(4):1405-17
Date
06/24/2003Pubmed ID
12819219DOI
10.1152/japplphysiol.00516.2002Scopus ID
2-s2.0-0141567924 (requires institutional sign-in at Scopus site) 53 CitationsAbstract
The primary objective of this study was to determine the effectiveness of isometric exercise (IE) as a countermeasure to hindlimb unloading (HU)-induced atrophy of the slow (soleus) and fast (plantaris and gastrocnemius) muscles. Rats were assigned to either weight-bearing control, 7-day HU (H7), H7 plus IE (I7), 14-day HU (H14), or H14 plus IE (I14) groups. IE consisted of ten 5-s maximal isometric contractions separated by 90 s, administered three times daily. Contractile properties of the soleus and plantaris muscles were measured in situ. The IE attenuated the HU-induced decline in the mass and fiber diameter of the slow-twitch soleus muscle, whereas the gastrocnemius and plantaris mass were not protected. These results are consistent with the mean electromyograph recordings during IE that indicated preferential recruitment of the soleus over the gastrocnemius and plantaris muscles. Functionally, the IE significantly protected the soleus from the HU-induced decline in peak isometric force (I14, 1.49 +/- 0.12 vs. H14, 1.15 +/- 0.07 N) and peak power (I14, 163 +/- 17 vs. H14, 75 +/- 11 mN.fiber length.s-1). The exercise protocol showed protection of the plantaris peak isometric force at H7 but not H14. The IE also prevented the HU-induced decline in the soleus isometric contraction time, which allowed the muscle to produce greater tension at physiological motoneuron firing frequencies. In summary, IE resulted in greater protection from HU-induced atrophy in the slow soleus than in the fast gastrocnemius or plantaris.
Author List
Hurst JE, Fitts RHAuthor
Robert Fitts PhD Professor in the Biological Sciences department at Marquette UniversityMESH terms used to index this publication - Major topics in bold
AnimalsBody Weight
Eating
Electromyography
Hindlimb Suspension
Male
Muscle Contraction
Muscle, Skeletal
Muscular Atrophy
Organ Size
Physical Conditioning, Animal
Rats
Rats, Sprague-Dawley