Exercise with hypoventilation induces lower muscle oxygenation and higher blood lactate concentration: role of hypoxia and hypercapnia.
Eight men performed three series of 5-min exercise on a cycle ergometer at 65% of normoxic maximal O(2) consumption in four conditions: (1) voluntary hypoventilation (VH) in normoxia (VH(0.21)), (2) VH in hyperoxia (inducing hypercapnia) (inspired oxygen fraction [F(I)O(2)] = 0.29; VH(0.29)), (3) normal breathing (NB) in hypoxia (F(I)O(2) = 0.157; NB(0.157)), (4) NB in normoxia (NB(0.21)). Using near-infrared spectroscopy, changes in concentration of oxy-(Delta[O(2)Hb]) and deoxyhemoglobin (Delta[HHb]) were measured in the vastus lateralis muscle. Delta[O(2)Hb - HHb] and Delta[O(2)Hb + HHb] were calculated and used as oxygenation index and change in regional blood volume, respectively. Earlobe blood samples were taken throughout the exercise. Both VH(0.21) and NB(0.157) induced a severe and similar hypoxemia (arterial oxygen saturation [SaO(2)] < 88%) whereas SaO(2) remained above 94% and was not different between VH(0.29) and NB(0.21). Arterialized O(2) and CO(2) pressures as well as P50 were higher and pH lower in VH(0.21) than in NB(0.157), and in VH(0.29) than in NB(0.21). Delta[O(2)Hb] and Delta[O(2)Hb - HHb] were lower and Delta[HHb] higher at the end of each series in both VH(0.21) and NB(0.157) than in NB(0.21) and VH(0.29). There was no difference in Delta[O(2)Hb + HHb] between testing conditions. [La] in VH(0.21) was greater than both in NB(0.21) and VH(0.29) but not different from NB(0.157). This study demonstrated that exercise with VH induced a lower tissue oxygenation and a higher [La] than exercise with NB. This was caused by a severe arterial O(2) desaturation induced by both hypoxic and hypercapnic effects.
Woorons
Xavier
X
Université Paris 13, Laboratoire Réponses cellulaires et fonctionnelles à l'hypoxie, EA 2363 UFR-SMBH, Bobigny, France. xwoorons@laposte.net
Bourdillon
Nicolas
N
Vandewalle
Henri
H
Lamberto
Christine
C
Mollard
Pascal
P
Richalet
Jean-Paul
JP
Pichon
Aurélien
A
D000328:Adult; D001642:Bicycling; D002245:Carbon Dioxide / Q000097:blood; D004423:Ear / Q000098:blood supply; D015444:Exercise; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D006935:Hypercapnia / Q000097:blood* / Q000503:physiopathology; D007040:Hypoventilation / Q000097:blood* / Q000503:physiopathology; D000860:Hypoxia / Q000097:blood* / Q000503:physiopathology; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism*; D010092:Oximetry; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010108:Oxyhemoglobins / Q000378:metabolism; D015656:Respiratory Mechanics; D019265:Spectroscopy, Near-Infrared; D013997:Time Factors; D015854:Up-Regulation; D055815:Young Adult
D006454:Hemoglobins; D010108:Oxyhemoglobins; D002245:Carbon Dioxide; D019344:Lactic Acid; C100003:deoxyhemoglobin; D010100:Oxygen