Perceived mental strain dissociates from perceived physical strain during relative intensity submaximal exercise on ascent from low to high altitude

Perceived fatigability, which has perception of physical strain and of mental strain as its components, can impact exercise tolerance. Upon ascent to high altitude, low landers experience reduced exercise capacity and reduced tolerance for a given absolute submaximal work rate. It is established that perceived physical strain tracks with relative exercise intensity. However, it is not known how altitude ascent affects perceived mental strain relative to perceived physical strain. We tested the hypothesis that when exercising at the same relative exercise intensity perceived physical strain will remain unchanged whereas perceived mental strain will decrease on ascent from low to high altitude in the Everest region in Nepal. Twelve hours after arriving at each of three elevations; 1400 m, 3440 m, and 4240 m, 12 untrained participants used the task effort awareness (TEA) and physical-rating of perceived exertion (P-RPE) scales to report perceived mental and physical strain during a 20 min walking test at a self-monitored heart rate reserve (HRR) range of 40-60% (Polar HR Monitor). TEA and P-RPE were recorded twice during exercise (5-7 min and 14-16 min). Neither P-RPE (1400 m: 11.1 ± 1.8, 3440 m: 10.7 ± 1.2, 4240 m: 11.5 ± 1.5) nor %HRR (1400 m: 55.25 ± 7.34, 3440 m: 51.70 ± 6.70, 4240 m: 50.17 ± 4.02) changed as altitude increased. TEA decreased at 4240 m (2.05 ± 0.71) compared to 1400 m (3.44 ± 0.84)--this change was not correlated with any change in %HRR nor was it due to a change in core affect. These findings support our hypothesis and demonstrate the independence of perceived physical and perceived mental strain components of perceived fatigability. Implications for exercise tolerance remain to be determined.