title: Maximal voluntary hyperpnoea increases blood lactate concentration during exercise.
abstract: Ventilatory work during heavy endurance exercise has not been thought to influence systemic lactate concentration. We evaluated the effect of maximal isocapnic volitional hyperpnoea upon arterialised venous blood lactate concentration ([lac-]B) during leg cycling exercise at maximum lactate steady state (MLSS). Seven healthy males performed a lactate minimum test to estimate MLSS, which was then resolved using separate 30 min constant power tests (MLSS=207+/-8 W, mean +/- SEM). Thereafter, a 30 min control trial at MLSS was performed. In a further experimental trial, the control trial was mimicked except that from 20 to 28 min maximal isocapnic volitional hyperpnoea was superimposed on exercise. Over 20-28 min minute ventilation, oxygen uptake, and heart rate during the control and experimental trials were 87.3+/-2.4 and 168.3+/-7.0 l min(-1) (P<0.01), the latter being comparable to that achieved in the maximal phase of the lactate minimum test (171.9+/-6.8 l min(-1)), 3.46+/-0.20 and 3.83 +/- 0.20 l min(-1) (P<0.01), and 158.5+/-2.7 and 166.8+/-2.7 beats min(-1) (P<0.05), respectively. From 20 to 30 min of the experimental trial [lac-]B increased from 3.7+/-0.2 to 4.7+/-0.3 mmol l(-1) (P<0.05). The partial pressure of carbon dioxide in arterialised venous blood increased approximately 3 mmHg during volitional hyperpnoea, which may have attenuated the [lac-]B increase. These results show that, during heavy exercise, respiratory muscle work may affect [lac-]B. We speculate that the changes observed were related to the altered lactate turnover in respiratory muscles, locomotor muscles, or both.
authors.affiliation: School of Biomedical and Natural Sciences, Nottingham Trent University, Nottingham, NG11 8NS, UK.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Johnson
authors.forename: Graham R
authors.initials: GR
authors.lastname: Sharpe
authors.forename: Alison K
authors.initials: AK
authors.lastname: McConnell
mesh_terms: D000328:Adult; D002245:Carbon Dioxide / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D006985:Hyperventilation / Q000503:physiopathology*; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D010100:Oxygen / Q000097:blood; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology; D012132:Respiratory Muscles / Q000502:physiology*; D014836:Volition
chemical_list: D002245:Carbon Dioxide; D019344:Lactic Acid; D010100:Oxygen