Functional pools of fast and slow twitch fibers observed by /sup 31/P-NMR during exercise of flexor wrist muscles in man
Functional compartments of fast and slow twitch fibers have been observed by /sup 31/P-NMR spectroscopy during exercise of the wrist flexor muscles in a sedentary, young male subject. Values of Pi, phosphocreatine (PCr) and adenine nucleotides were determined at rest and during an exercise protocol. The subject flexed his wrist muscles at 20% of maximum strength every 5 sec for 6 min and then increased his effort in the next two 6 min intervals to 40% and 60% of maximum. With exercise, the Pi/PCr rose rapidly to the exceptionally high value of 2.2 at 60% effort. As the Pi increased, the initial single peak (pH 7.0-6.9) split into two distinct components with pH values of 6.8 and 6.3. Quantitatively, distribution of the Pi was 40% in the pH 6.8 peak and 60% in the pH 6.3 peak as determined by area estimation following curve fitting. This presumably reflects two pools of Pi corresponding to the oxidative (slow twitch, high pH) and glycolytic (fast twitch, low pH) fibers. In the second identical exercise sequence which followed immediately, only one Pi peak (pH 6.8-6.9) appeared. This suggested that the glycolytic contribution to energy production was largely exhausted and the residual energy was derived from oxidative metabolism. During exercise at high levels, total phosphate decreased due primarily to loss of NMR visible adenine nucleotides. Similar phenomena have been observed in three other sedentary individuals, but not in trained athletes.
- Research Organization:
- Univ. of Pennsylvania, Philadelphia
- OSTI ID:
- 5721464
- Report Number(s):
- CONF-870644-
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
- Country of Publication:
- United States
- Language:
- English
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62 RADIOLOGY AND NUCLEAR MEDICINE
MUSCLES
DYNAMIC FUNCTION STUDIES
ADENINES
EXERCISE
GLYCOLYSIS
MEN
METABOLISM
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEOTIDES
PH VALUE
PHOSPHOCREATINE
PHOSPHORUS 31
AMINES
AMINO ACIDS
ANIMALS
ANTIMETABOLITES
AROMATICS
AZAARENES
CARBOXYLIC ACIDS
DRUGS
HETEROCYCLIC COMPOUNDS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MALES
MAMMALS
MAN
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
PRIMATES
PURINES
RESONANCE
SPECTRA
STABLE ISOTOPES
VERTEBRATES
551000* - Physiological Systems
550600 - Medicine