Combined spiroergometry and ³¹P–MRS of human calf muscle during high‐intensity exercise

Abstract

Simultaneous measurements of pulmonary oxygen consumption (VO ), carbon dioxide exhalation (VCO ) and phosphorus magnetic resonance spectroscopy ( P-MRS) are valuable in physiological studies to evaluate muscle metabolism during specific loads. Therefore, the aim of this study was to adapt a commercially available spirometric device to enable measurements of VO and VCO whilst simultaneously performing P-MRS at 3 T. Volunteers performed intense plantar flexion of their right calf muscle inside the MR scanner against a pneumatic MR-compatible pedal ergometer. The use of a non-magnetic pneumotachograph and extension of the sampling line from 3 m to 5 m to place the spirometric device outside the MR scanner room did not affect adversely the measurements of VO and VCO . Response and delay times increased, on average, by at most 0.05 s and 0.79 s, respectively. Overall, we were able to demonstrate a feasible ventilation response (VO = 1.05 ± 0.31 L/min; VCO = 1.11 ± 0.33 L/min) during the exercise of a single calf muscle, as well as a good correlation between local energy metabolism and muscular acidification (τ and pH; R = 0.73, p < 0.005) and global respiration (τ and VO ; R = 0.55, p = 0.01). This provides improved insights into aerobic and anaerobic energy supply during strong muscular performances.

Competitive cation binding computations of proton balance for reactions of the phosphagen and glycolytic energy systems within skeletal muscle

“…During 3 min of sustained intense exercise, muscle CrP stores fall in an exponential decay function, but the half-life (t 0.5 ) of CrP during such conditions is still in the order of 1 min (6). More recent data applying advanced 31 P NMR equipment and methodologies during intense exercise [ 20 ] and in recovery from intense exercise [ 20 ], further supports this evidence. The data reveal that there is near instantaneous support of CrP derived ATP from the myokinase reaction and glycolysis.…”

“…over 3 min of intense exercise to contractile failure. The ATP capacity of the creatine kinase reaction approximates 30 mmol/kg wet wt [ 4 , 6 , 20 , 21 ], leaving a difference of 60 mmol/kg wet wt of ATP regeneration from the sum of the adenylate kinase reaction and glycolysis. During 3 min of sustained intense exercise, muscle CrP stores fall in an exponential decay function, but the half-life (t 0.5 ) of CrP during such conditions is still in the order of 1 min (6).…”

Comparison of metabolic adaptations between endurance‐ and sprint‐trained athletes after an exhaustive exercise in two different calf muscles using a multi‐slice 31P‐MR spectroscopic sequence

“…After the exercise, VO 2 decreased instantly for both groups, with the time constant, τ VO2_f , for the fast component of the bi‐exponential decay being shorter in endurance athletes ( τ VO2_f , sprinters 60 (55, 65) s vs. endurance 48 (45, 59) s; p = 0.16). The weighting factors of the bi‐exponential function ( f VO2 and f VCO2 ) showed a distinct weighting towards the fast component and a rather negligible impact of the slower component …”

“…Oxygen uptake (VO 2 in l/min) and carbon dioxide production (VCO 2 in l/min) were monitored continuously by using a spirometry system PowerCube (LF8, Ganshorn, Medizin Electronic, Niederlauer, Germany), which had been adapted to enable measurements in the MR scanner . The acquisition of the respiratory data started immediately after placing the subject into the scanner to allow habituation to the breathing mask and to avoid unusual breathing patterns due to the small breathing resistance of the pneumotachograph membrane.…”

“…Post‐processing of the respiratory data has been described in detail in our previous work . In brief, the raw spirometric data were resampled to a temporal resolution of 10 s by the vendor software.…”