The phosphocreatine concentration ([PCr]) falls during exercise by forming an equimolar amount of inorganic phosphate ([Pi]) as described by the creatineinase reaction. Metabolic cycles employed during the exercise are governed by the level of
oxygen
supply. Therefore, depending the level of oxygen during the exercise, the exercise can be described by three major categories, which may be attributed from the intensity, frequency, and duration of the exercise: anaerobic, lactic acid, and
aerobic
exercises. In the present work, the time course of changes in [Pi/PCr] during the maximal intermittent isokinetic exercise of forearm muscle, which involves the three categories, were measured by in vivo 31P MR spectroscopy. Compare the time
course of
changes in [Pi/PCr] between sedentaries and trained oarsman during the maximal intermittent isokinetic exercise. Characterise the aerobic and anaerobic exercises by observing different time course of changes in[pi/PCr]. Forearm(nondominant side)
muscle
of each subject was placed in the center of RF coil, which was double tuned for the 1Hand 31P resonance frequencies of 200.21 MH and 81.0MH respectively (Bruker, Switzerland). Forearm flexion was performed with a fixed 0.5P by a home made
ergometer. In
vivo 31P MR Spectroscopy was performed on a Bruker Biospec 4.7T Imaging and Spectroscopy System (Bruker, Fallanden, Swizerland). Shimming was done on the 1H signal, and the 31P signal was obtained from M.Flex or Digitorum Superficialis. A series
of
spectrum was acquired before the initial exercise starts and during the time intervals, 1 minute between exercises. Peak areas were measured by integration. Subjects were ordered to do the forearm flexion exercise. For Group 1 (N=10), trained
oarsmen
were subjected to a series of 30, 90 or 180 seconds of exercises intervaled by 1 minute of resting period until 20 minutes passed the all-out, and for Group 2, sedentaries (n=10) were employed, as a control group, to do the same exercise protocol
as for
the oarsmen. 31P MR spectra of the forearm muscle before exercise, during exercise, at the end of the exercise(i.e.all-out). For the maximal intermittent 90 seconds isokinetic exercise, the ratio of [Pi/PCr] of the trained oarsmen has the value
of
0.9±0.07 at the plateau during about 25 minutes of the exercise. In contrary, the value of the sedentaries is continuously rising until the all-out, during about 10 minutes of the exercise. For the maximal intermittent 180 seconds isokinetic
exercise,
the ratio of [Pi/PCr] of the trained oarsmen has the value of 0.65±0.07 at the plateau during about 20 minutes of the exercise. In contrary, the value of the value of the sedentaries is continuously rising until the all-out, during about 8
minutes
of
the exercise. The plateau achieved in the time course of [Pi/PCr] during the exercise by the trained oarsmen may indicate that the exercise can be categorized as the aerobic exercise. The continuously rising [Pi/PCr] observed during the exercise
by
the
sedentaries may indicate that the exercise can be categorized as the anaerobic exercise. We may deduce a conclusion from the above that the above that the accumulation of the [Pi/PCr] may not be an indication of the fatigue.
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