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In‐magnet bicycling exercise: a novel 31P MRS window on the energetics of human locomotion
Author(s) -
Jeneson Jeroen,
Schmitz Joep,
Nicolay Klaas
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1176.6
Subject(s) - glycogenolysis , skeletal muscle , cardiology , physical medicine and rehabilitation , medicine , exercise physiology , anaerobic exercise , physical therapy , endocrinology , metabolism
The clinical standard test of patient fitness is the upright bicycle exercise test. For a number of reasons, no proper equivalent human MR exercise test has been available. Past 31 P MR studies employing single limb exercise regimens generally failed to put any significant demands on the cardiovascular system (1). As such, a comprehensive understanding of skeletal muscle performance during whole body activity has been lacking. Here, we report on 31 P MRS studies employing a novel ergometer that for the first time offers true in‐magnet human bicycling exercise testing. Heart rates directly following exercise were of 150 + 15 bpm. In addition to 31 P MRS study of ATP metabolism over a 100‐fold dynamic range of ATP turnover at near‐constant pH, it allows for non‐invasive 31 P MRS study of glycogenolysis through the dynamics of hexose monophosphate (HMP) resonances. Here (but not previously (2)) we routinely observed HMP accumulations of up to 10 mM within 2 minutes after termination of exercise at high workloads indicating massive activation of glycogenolysis during the preceding exercise. Yet intramuscular pH typically did not fall below 6.8 during exercise confirming our previous observation of unique homeostatic robustness of quadriceps muscle involved in two‐legged exercise (2).