Effect of exercise-induced arterial hypoxemia on quadriceps muscle fatigue in healthy humans

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2006-02, Vol.290 (2), p.R365-R375
• Main Authors: Romer, Lee M, Haverkamp, Hans C, Lovering, Andrew T, Pegelow, David F, Dempsey, Jerome A
• Format: Article
• Language: English
• Subjects: Adult; Blood Gas Analysis; Exercise - physiology; Health; Humans; Hypoxia - blood; Male; Muscle Fatigue - physiology; Oxygen Consumption; Quadriceps Muscle - physiology; Time Factors
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00332.2005

1 Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, United Kingdom; and 2 John Rankin Laboratory of Pulmonary Medicine, Department of Population Health Sciences, Medical Sciences Center, University of Wisconsin, Madison, Wisconsin Submitted 10 May 2005 ; accepted in final form 7 September 2005 The effect of exercise-induced arterial hypoxemia (EIAH) on quadriceps muscle fatigue was assessed in 11 male endurance-trained subjects [peak O 2 uptake ( O 2 peak ) = 56.4 ± 2.8 ml·kg –1 ·min –1 ; mean ± SE]. Subjects exercised on a cycle ergometer at 90% O 2 peak to exhaustion (13.2 ± 0.8 min), during which time arterial O 2 saturation (Sa O 2 ) fell from 97.7 ± 0.1% at rest to 91.9 ± 0.9% (range 84–94%) at end exercise, primarily because of changes in blood pH (7.183 ± 0.017) and body temperature (38.9 ± 0.2°C). On a separate occasion, subjects repeated the exercise, for the same duration and at the same power output as before, but breathed gas mixtures [inspired O 2 fraction (F I O 2 ) = 0.25–0.31] that prevented EIAH (Sa O 2 = 97–99%). Quadriceps muscle fatigue was assessed via supramaximal paired magnetic stimuli of the femoral nerve (1–100 Hz). Immediately after exercise at F I O 2 0.21, the mean force response across 1–100 Hz decreased 33 ± 5% compared with only 15 ± 5% when EIAH was prevented ( P < 0.05). In a subgroup of four less fit subjects, who showed minimal EIAH at F I O 2 0.21 (Sa O 2 = 95.3 ± 0.7%), the decrease in evoked force was exacerbated by 35% ( P < 0.05) in response to further desaturation induced via F I O 2 0.17 (Sa O 2 = 87.8 ± 0.5%) for the same duration and intensity of exercise. We conclude that the arterial O 2 desaturation that occurs in fit subjects during high-intensity exercise in normoxia (–6 ± 1% Sa O 2 from rest) contributes significantly toward quadriceps muscle fatigue via a peripheral mechanism. magnetic stimulation; low- and high-frequency fatigue; quadriceps twitch force; voluntary activation; peripheral fatigue; central fatigue Address for reprint requests and other correspondence: L. M. Romer, Centre for Sports Medicine and Human Performance, Brunel Univ., Uxbridge, Middlesex UB8 3PH, UK (e-mail: lee.romer{at}brunel.ac.uk )