Monitoring ‘Altitude Natives" in Professional Cycling

“Sergio was raised in the mountains, goes back in winter and lives and trains at different levels. We’ve looked as far as we can at the effects of this, but our own understanding is limited by a lack of scientific research into ‘altitude natives’ such as Sergio.We are commissioning independent scientific research to better understand the effects of prolonged periods at altitude after returning from sea level, specifically on altitude natives. The independent experts are looking to use Wada-accredited laboratories and Team Sky will make the data and findings available to Wada, the UCI and CADF.”

– Dave Brailsford, General Manager, Team Sky

You may have already read the breaking news on Sergio Henao who has been taken off Team Sky’s racing schedule. No doubt many commentators have already come to the conclusion that ‘questions’ in out-of-competition, anti-doping testing means guilty. Maybe. But let’s look at the difficulties for cycling’s anti-doping enforcement to monitor the performance and physiology of ‘altitude natives’.

I suppose in mother nature’s way of stopping increased blood viscosity, and thus increased likelihood of thrombosis and stroke, Tibetans actually have lower oxygen saturation in their tissues and lower red blood cell count than their ancestors – the Han Chinese.  Instead it seems that there was a gene selection for endothelial PAS domain protein 1 (EPAS1) in this population, with variations regulating the physiological responses to high-altitude hypoxia (low oxygen conditions) via a hypoxia-inducible transcription factor pathway (PLoS One paper on genetic adaptation in Sherpas). These responses include encoding for the HIF-2alpha protein, which up-regulates numerous hypoxia -inducible genes (including EPO) in the lung and other tissues. However mutations of EPAS-1 not only bring an advantage from EPO but include metabolism, vascular permeability (Hypoxia: adapting to high altitude by mutating EPAS-1) and  influence aerobic-anaerobic conditions in elite endurance athletes – including cardiovascular function, energetic demand, muscular activity and oxygen availability .

But, it doesn’t stop there. Sergio Henao is a South American. Tibetan and Andean populations exhibit quantitatively different responses to hypobaric hypoxic stress. At the same altitude, Tibetan mean resting ventilation and hypoxic ventilatory response were more than one-half standard deviation higher than Andean Aymara means while Tibetan mean oxygen saturation and hemoglobin concentration were more than one standard deviation below the Andean means. Yet when you compare Tibetan and Andean patterns of oxygen transport they appear equally effective functionally as evaluated by birthweight and maximal aerobic capacity across a range of altitudes (Contrasting adaptations – aka it is convergent adaptation and rose completely independently).