Relationships between mechanical power, O2 consumption, O2 deficit and high-energy phosphates during calf exercise in humans

Abstract

Whole-body O(2) uptake ( VO(2)), O(2) deficit and the concentration of high-energy phosphates (determined by (31)P spectroscopy) in human calf muscle were measured during moderate aerobic square-wave exercise of increasing intensity in ten volunteers. Net VO(2) (above resting) increased linearly with mechanical power, yielding a delta efficiency of 13.1%. "Gross" O(2) deficit increased linearly with net VO(2). The fraction of phosphocreatine (PC) split at steady state increased linearly with the mechanical power and with the O(2) deficit. If the [PC] in resting muscle is known, the slope of the regression between PC split and O(2) deficit (in millimoles) yields the P/O(2) ratio. To calculate this, the O(2) deficit was corrected for the amount of O(2) derived from the body stores, as obtained from literature data. The value so obtained, for a resting [PC] of 30 mM was 5.9, consistent with canonical textbook values. Furthermore, the ratio of "true" O(2) deficit to steady-state VO(2) is a measure of the time constant of VO(2) kinetics at work onset at the muscle level: assuming a monoexponential time course without time delays it amounted to about 17 s, close to the value that can be expected in mammalian muscle at 37 degrees C.

High-energy phosphate metabolism during two bouts of progressive calf exercise in humans measured by phosphorus-31 magnetic resonance spectroscopy

“…The work rate is given between the vertical lines. Statistically significant effects were marked with * (P <0.001) 31 P-MRS studies reported intramuscular mean pH values between 7.0 and 7.1 (Barstow et al 1994a(Barstow et al , 1994bFrancescato et al 2003;Marsh et al 1991;Rossiter et al 2001Rossiter et al , 2002. Collectively, the intramuscular pH of our volunteers at rest ranged between 6.94 and 7.02.…”

Hybrid diffuse optical techniques for continuous hemodynamic measurement in gastrocnemius during plantar flexion exercise

“…Given the complexity of the operation of muscle tissue and the dynamically regulated interplay of local versus global controls of blood perfusion in response to the tissue demand for oxygen, mechanical effects, and aggregation of feedback metabolites, it is no wonder that muscle physiology and diseases thereof remain a highly active field of study. 5,[10][11][12][13][14][15][16][17] Our particular interest is the mechanism of local muscle action and the specific pathology of peripheral arterial disease (PAD). PAD is emphasized in muscle research because it is associated with a rather high morbidity and has a distinctly detrimental effect on the patient's health and quality of life.…”

Sprint running: a new energetic approach

“…Let us assume that the maximal blood lactate concentration in an élite athlete can attain 20·mmol·l -1 . Thus, since the accumulation of 1·mmol·l -1 lactate in blood is energetically equivalent to the consumption of 3·ml·O 2 ·kg -1 (see di Prampero and Ferretti, 1999), the maximal amount of energy that can obtained from lactate is about: Francescato et al, 2003). We can assume that the muscle mass involved in the all-out effort in question, for an élite sprinter, is about 25% of his body mass (e.g.…”