title: Excess VO2 during ramp exercise is positively correlated to intercostal muscles deoxyhemoglobin levels above the gas exchange threshold in young trained cyclists.
abstract: We assessed respiratory muscles oxygenation responses during a ramp exercise to exhaustion and further explored their relationship with the non-linear increase of VO2 (VO2 excess) observed above the gas-exchange threshold. Ten male cyclists completed a ramp exercise to exhaustion on an electromagnetically braked cycle-ergometer with a rate of increment of 30Wmin(-1) with continuous monitoring of expired gases (breath-by-breath) and oxygenation status of intercostal muscles. Maximal inspiratory and expiratory pressure measurements were taken at rest and at exhaustion. The VO2 excess represents the difference between VO2max observed and VO2max expected using linear equation between the VO2 and the intensity before gas-exchange threshold. The deoxyhemoglobin remained unchanged until 60% of maximal aerobic power (MAP) and thereafter increased significantly by 37±18% and 40±22% at 80% and 100% of MAP, respectively. Additionally, the amplitude of deoxyhemoglobin increase between 60 and 100% of MAP positively correlated with the VO2 excess (r=0.69, p<0.05). Compared to exercise start, the oxygen tissue saturation index decreased from 80% of MAP (-4.8±3.2%, p<0.05) onwards. At exhaustion, maximal inspiratory and expiratory pressures declined by 7.8±16% and 12.6±10% (both p<0.05), respectively. In summary, our results suggest a significant contribution of respiratory muscles to the VO2 excess phenomenon.
authors.affiliation: EA-3300, APERE, Sport Sciences Department, University of Picardie Jules Verne, Amiens, France; UR12ES06, Medicine Department, University of Sousse, Sousse, Tunisia; Faculty of Sciences of Bizerte, University of Carthage, Tunisia. Electronic address: oueslati.ferid@hotmail.com.
authors.forename: Ferid
authors.initials: F
authors.lastname: Oueslati
authors.affiliation: Institute of Sport Sciences University of Lausanne (ISSUL), University of Lausanne, Lausanne, Switzerland.
authors.forename: Olivier
authors.initials: O
authors.lastname: Girard
authors.affiliation: UR12ES06, Medicine Department, University of Sousse, Sousse, Tunisia.
authors.forename: Zouhair
authors.initials: Z
authors.lastname: Tabka
authors.affiliation: EA-3300, APERE, Sport Sciences Department, University of Picardie Jules Verne, Amiens, France.
authors.forename: Said
authors.initials: S
authors.lastname: Ahmaidi
mesh_terms: D000293:Adolescent; D001642:Bicycling / Q000502:physiology*; D001944:Breath Tests; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007366:Intercostal Muscles / Q000378:metabolism*; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology*; D011312:Pressure; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012119:Respiration; D019265:Spectroscopy, Near-Infrared
chemical_list: D006454:Hemoglobins; C100003:deoxyhemoglobin; D010100:Oxygen
keywords: Excess VO2; NIRS; Respiratory muscles oxygenation; Respiratory muscles strength