Early Ventilation-Heart Rate Breakpoint during Incremental Cycling Exercise

• Published in: International journal of sports medicine 2014-03, Vol.35 (3), p.191-198
• Main Authors: Gravier, G., Delliaux, S., Ba, A., Delpierre, S., Guieu, R., Jammes, Y.
• Format: Article
• Language: English
• Subjects: Adult; Bicycling - physiology; Biological and medical sciences; Carbon Dioxide - blood; Exercise - physiology; Female; Fundamental and applied biological sciences. Psychology; Heart Rate - physiology; Human physiology applied to population studies and life conditions. Human ecophysiology; Humans; Lactic Acid - blood; Male; Medical sciences; Oxygen - blood; Partial Pressure; Physiology & Biochemistry; Pneumology; Reproducibility of Results; Respiration; Respiratory system : syndromes and miscellaneous diseases; Tidal Volume; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports
• ISSN: 0172-4622; 1439-3964
• DOI: 10.1055/s-0033-1345145

Abstract Abstract Previous observations having reported a transient hypoxia at the onset of incremental exercise, we investigated the existence of concomitant ventilatory and heart rate (HR) breakpoints. 33 subjects executed a maximal cycling exercise with averaging for successive 5-s periods of HR, ventilation, tidal volume (V T ), mean inspiratory flow rate (V T /Ti), and end-tidal partial pressures of O 2 (P ET O 2 ) and CO 2 . In 10 subjects, the transcutaneous partial pressure of O 2 (PtcO 2 ) was recorded and the venous blood lactic acid (LA) concentration measured. At the beginning of exercise, P ET O 2 decreased, reaching a nadir, then progressively increased until the exercise ended. PtcO 2 varied in parallel. Whether or not a 0-W cycling period preceded the incremental exercise, the rate of changes in V E , V T , V T /Ti and HR significantly increased when the nadir PO 2 was reached. The ventilatory/ HR breakpoint was measured at 33±4% of VO 2 max, whereas the ventilatory threshold (V Th ) was detected at 67±4% of VO 2 max and LA began to increase at 45 to 50% of VO 2 max. During incremental cycling exercise, we identified the existence of HR and ventilatory breakpoints in advance of both lactate and ventilatory thresholds which coincided with modest hypoxia and hypercapnia.