Premium
Muscle metabolic economy is inversely related to exercise intensity and type II myofiber distribution
Author(s) -
Hunter Gary R.,
Newcomer Brad R.,
LarsonMeyer D. Enette,
Bamman Marcas M.,
Weinsier Roland L.
Publication year - 2001
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.1051
Subject(s) - isometric exercise , skeletal muscle , medicine , endocrinology , intensity (physics) , exercise intensity , myocyte , muscle hypertrophy , economy , cardiology , economics , physics , heart rate , blood pressure , quantum mechanics
It is not known what causes the well‐established inverse relationship between whole‐body exercise economy and exercise intensity. The purpose of this study was to: (1) evaluate muscle exercise economy at 45%, 70%, and maximum isometric strength using 31 P magnetic resonance spectroscopy ( 31 P‐MRS); and (2) determine the relationship between percent type II muscle fiber cross‐section, whole‐body exercise economy, and muscle exercise economy. Subjects included 32 premenopausal women. Muscle exercise economy was significantly different across the three exercise intensities (28.1 ± 10.4, 24.8 ± 8.2, and 20.2 ± 7.5 N/cm 2 · mmol/L adenosine triphosphate [ATP] for the 45%, 70%, and maximum intensities, respectively). Percent type II muscle area was significantly related to whole‐body metabolic economy during activities of daily living ( r = −0.68) and 31 P‐MRS muscle metabolic economy during isometric plantar flexion ( r = −0.53). These data suggest that skeletal muscle becomes less economical as force production increases, and that these decreases in metabolic economy may be related to increased dependence on inefficient type II muscle. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 654–661, 2001