Relationship between decrement of muscular pH and CO2 excess during incremental exercise / 体力科学

ABSTRACT

A study was conducted to investigate using <SUP>31</SUP>P NMR the relationship between the total excess volume of CO<SUB>2</SUB> output (CO<SUB>2</SUB> excess) due to bicarbonate buffering of lactic acid produced in exercise and the decrease of intracellular pH during incremental exercise. Five sprinters and 5 joggers performed incremental exercise to exhaustion on an bicycle ergometer. The values of CO<SUB>2</SUB> excess and CO<SUB>2</SUB> excess per body weight (CO<SUB>2</SUB> excess/W) were not different between the sprinters (2388±659m<I>l</I>, 36.7±8.5 m<I>l</I>·kg<SUP>-1</SUP>) and the joggers (2275±278m<I>l</I>, 40.0±6, 3m<I>l</I>·kg<SUP>-1</SUP>) . Below the ventilatory threshold (VT), from VT to the respiratory compensation point (RCP), and above RCP, the V<SUB>od2</SUB>-V<SUB>co2</SUB> slopes were not different between the sprinters and the joggers, respectively (0.95±0.05 vs 0.95±0.06, 1.21±0.11 vs 1.30±0.14, 1.69±0.24 vs 1.76±0.18) . However, the joggers showed significantly higher CO<SUB>2</SUB> excess/W per blood lactate accumulation (&Delta;La) in exercise (CO<SUB>2</SUB> excess/W/&Delta;La, 5.34±0.32m<I>l</I>·kg<SUP>-1</SUP>·mmol<SUP>-1</SUP>·<I>l</I><SUP>-1</SUP>) than the sprinters (4.50±0.14m<I>l</I>·kg<SUP>-1</SUP>·mmol<SUP>-1</SUP>·<I>l</I><SUP>-1</SUP>) . The decrement of intracellular pH during incremental exercise showed a tendency to be smaller in joggers (0.63±0.18 pH unit) than in sprinters (0.83±0.10 pH unit), although there was no significant difference between the two groups. The values of CO<SUB>2</SUB> excess/W/&Delta;La were correlated with the decrease of intracellular pH (r=-0.792, p<0.01) . It is suggested that CO<SUB>2</SUB> excess/W/&Delta;La reflects the efficiency of the bicarbonate buffering system, and could be an important factor influencing the decrease of intracellular pH due to lactate production.