J. Bangsbo et al., NMR AND ANALYTIC BIOCHEMICAL EVALUATION OF CRP AND NUCLEOTIDES IN THEHUMAN CALF DURING MUSCLE-CONTRACTION, Journal of applied physiology, 74(4), 1993, pp. 2034-2039
This study compared biochemical and P-31-nuclear magnetic resonance (N
MR) determinations of energy metabolites during isometric contractions
of the human calf muscle at various exercise intensities. Seven male
subjects performed one-legged isometric contractions at a work load of
28, 64, and 90% of maximal voluntary contraction force (28-, 64-, and
90%-CON, respectively) for 3 min, 40 s, and 40 s, respectively, in a
magnet and in an exact model of the magnet with an arrangement for rap
id muscle biopsy sampling from the gastrocnemius. The decrease in phos
phocreatine (CrP) determined by NMR was 20, 33, and 71% for 28%-, 64%-
, and 90%-CON, respectively. These decreases were the same as those de
termined biochemically (25,34, and 61%, respectively). Muscle CrP 1 mi
n after 90%-CON was also found to be similar between NMR and biochemic
al determinations (88 and 74% of resting value, respectively). Althoug
h no significant change in muscle ATP was found by NMR, a decrease of
29% was observed biochemically at 90%-CON. The ratio between muscle Cr
P and ATP was the same between NMR and biochemical determinations exce
pt for 90%-CON (1.98 and 0.78, respectively). The increase in muscle A
DP determined by NMR was two-, five-, and eightfold higher than that f
ound biochemically for 28%-, 64%-, and 90%-CON, respectively. This was
related to the change in muscle inosine monophosphate concentration (
r = 0.61, P < 0.05). The present data suggest that biochemical measure
ments and NMR spectroscopy provide the same information on muscle CrP
during isometric muscle contractions. This also appears to be true for
muscle ATP, with the exception of measurements during muscle contract
ions at high work loads. The more pronounced increase in muscle ADP de
termined by NMR compared with that determined by biochemical measureme
nts is consistent with free ADP being a major modulator of muscle meta
bolism during muscle contractions.