TY - JOUR
T1 - Is lactic acidosis a cause of exercise induced hyperventilation at the respiratory compensation point?
AU - Meyer, Tim
AU - Faude, O.
AU - Scharhag, J.
AU - Urhausen, A.
AU - Kindermann, W.
PY - 2004/10
Y1 - 2004/10
N2 - Objectives: The respiratory compensation point (RCP) marks the onset of hyperventilation ("respiratory compensation") during incremental exercise. Its physiological meaning has not yet been definitely determined, but the most common explanation is a failure of the body's buffering mechanisms which leads to metabolic (lactic) acidosis. It was intended to test this experimentally. Methods: During a first ramp-like exercise test on a cycle ergometer, RCP (range: 2.51-3.73 l*min-1 oxygen uptake) was determined from gas exchange measurements in five healthy subjects (age 26-42; body mass index (BMI) 20.7-23.9 kg*m-2; VO2peak 51.3-62.1 ml*min-1*kg-1). On the basis of simultaneous determinations of blood pH and base excess, the necessary amount of bicarbonate to completely buffer the metabolic acidosis was calculated. This quantity was administered intravenously in small doses during a second, otherwise identical, exercise test. Results: In each subject sufficient compensation for the acidosis, that is, a pH value constantly above 7.37, was attained during the second test. A delay but no disappearance of the hyperventilation was present in all participants when compared with the first test. RCP occurred on average at a significantly (p=0.043) higher oxygen uptake (+0.15 l*min-1) compared with the first test. Conclusions: For the first time it was directly demonstrated that exercise induced lactic acidosis is causally involved in the hyperventilation which starts at RCP. However, it does not represent the only additional stimulus of ventilation during intense exercise. Muscle afferents and other sensory inputs from exercising muscles are alternative triggering mechanisms.
AB - Objectives: The respiratory compensation point (RCP) marks the onset of hyperventilation ("respiratory compensation") during incremental exercise. Its physiological meaning has not yet been definitely determined, but the most common explanation is a failure of the body's buffering mechanisms which leads to metabolic (lactic) acidosis. It was intended to test this experimentally. Methods: During a first ramp-like exercise test on a cycle ergometer, RCP (range: 2.51-3.73 l*min-1 oxygen uptake) was determined from gas exchange measurements in five healthy subjects (age 26-42; body mass index (BMI) 20.7-23.9 kg*m-2; VO2peak 51.3-62.1 ml*min-1*kg-1). On the basis of simultaneous determinations of blood pH and base excess, the necessary amount of bicarbonate to completely buffer the metabolic acidosis was calculated. This quantity was administered intravenously in small doses during a second, otherwise identical, exercise test. Results: In each subject sufficient compensation for the acidosis, that is, a pH value constantly above 7.37, was attained during the second test. A delay but no disappearance of the hyperventilation was present in all participants when compared with the first test. RCP occurred on average at a significantly (p=0.043) higher oxygen uptake (+0.15 l*min-1) compared with the first test. Conclusions: For the first time it was directly demonstrated that exercise induced lactic acidosis is causally involved in the hyperventilation which starts at RCP. However, it does not represent the only additional stimulus of ventilation during intense exercise. Muscle afferents and other sensory inputs from exercising muscles are alternative triggering mechanisms.
UR - http://www.scopus.com/inward/record.url?scp=4844228232&partnerID=8YFLogxK
U2 - 10.1136/bjsm.2003.007815
DO - 10.1136/bjsm.2003.007815
M3 - Article
C2 - 15388552
AN - SCOPUS:4844228232
SN - 0306-3674
VL - 38
SP - 622
EP - 625
JO - British Journal of Sports Medicine
JF - British Journal of Sports Medicine
IS - 5
ER -