AltitudeOmics: exercise-induced supraspinal fatigue is attenuated in healthy humans after acclimatization to high altitude

Goodall, Stuart, Twomey, Rosie, Amann, Markus, Ross, Emma, Lovering, Andrew, Romer, Lee, Subudhi, Andrew and Roach, Robert (2014) AltitudeOmics: exercise-induced supraspinal fatigue is attenuated in healthy humans after acclimatization to high altitude. Acta Physiologica, 210 (4). pp. 875-888. ISSN 1748-1716

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Abstract

Aims: We asked whether acclimatisation to chronic hypoxia (CH) attenuates the level of supraspinal fatigue that is observed after locomotor exercise in acute hypoxia (AH). Methods: Seven recreationally-active participants performed identical bouts of constant-load cycling (131±39W, 10.1±1.4min) on three occasions: 1) in normoxia (N, PIO2, 147.1mmHg); 2) in AH (FIO2, 0.105; PIO2, 73.8mmHg); 3) after 14 days in CH (5,260m; PIO2, 75.7mmHg). Throughout trials, prefrontal-cortex tissue oxygenation and middle cerebral artery blood velocity (MCAV) were assessed using near-infrared-spectroscopy and transcranial Doppler sonography. Pre- and post-exercise twitch responses to femoral nerve stimulation and transcranial magnetic stimulation were obtained to assess neuromuscular and corticospinal function. Results: In AH, prefrontal oxygenation declined at rest (Δ7±5%) and end-exercise (Δ26±13) (P<0.01); the degree of deoxygenation in AH was greater than N and CH (P<0.05). The cerebral O2 delivery index (MCAv×CaO2) was 19±14% lower during the final minute of exercise in AH compared to N (P=0.013) and 20±12% lower compared to CH (P=0.040). Maximum voluntary and potentiated twitch force were decreased below baseline after exercise in AH and CH, but not N. Cortical voluntary activation decreased below baseline after exercise in AH (11%, P=0.014), but not CH (6%, P=0.174) or N (4%, P=0.298). A twofold greater increase in motor evoked potential amplitude was evident after exercise in CH compared to AH and N. Conclusion: These data indicate that exacerbated supraspinal fatigue after exercise in AH is attenuated after 14 days of acclimatisation to altitude. The reduced development of supraspinal fatigue in CH may have been attributable to increased corticospinal excitability, consequent to an increased cerebral O2 delivery.

Item Type:	Article
Additional Information:	Published online first before print 14 March 2014.
Uncontrolled Keywords:	adaptation, altitude, exercise, transcranial magnetic stimulation
Subjects:	B100 Anatomy, Physiology and Pathology C600 Sports Science
Department:	Faculties > Health and Life Sciences > Sport, Exercise and Rehabilitation
Related URLs:	Publisher
Depositing User:	Dr Stuart Goodall
Date Deposited:	20 Mar 2014 10:08
Last Modified:	12 Oct 2019 16:26
URI:	http://nrl.northumbria.ac.uk/id/eprint/15855

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