Moderate Intensity Exercise Ameliorates Negative Impacts of Simulated Altitude on Executive Function.

Abstract

PURPOSE: The present study was conducted to examine the behavioral cognitive and neurophysiological effects of acute exposure to simulated moderate and high altitudes at rest and during exercise in an effort to delineate whether there is a level of simulated altitude beyond which executive cognitive functions are impaired and whether exercise improves or worsens cognitive function during exposure to simulated altitude. METHODS: Fourteen recreationally active college students (M=9, F=5) aged 18-35 participated in this study, which consisted of six experimental days, with three simulated altitude conditions: sea level (SL), simulated moderate altitude (MA; 15.4% FIO2, ~2400 m) or simulated high altitude (HA; 12.8% FIO2, ~3900 m); and two exercise conditions: rest or moderate intensity cycling exercise at 60% altitude-specific peak power output, in a randomized-order, crossover design. Dependent variables included accuracy and reaction time on two executive cognitive function tasks (a modified Flanker task and a Stroop task), and the amplitude and latency of their associated event-related potentials. RESULTS: For the Flanker task, both MA and HA slowed down reaction time (p=0.04), while exercise improved reaction time (p=0.01). Similarly, for the Stroop task, HA (though not MA) slowed reaction time (p=0.02), while exercise improved reaction time (p=0.04). Accuracy was preserved under all conditions. These effects were partially explained by alterations in associated event-related potential amplitudes and latencies, such as slower N200 latencies with altitude (p=0.04) but faster latencies with exercise (p<0.01), as well as reduced P300 amplitude and slower latency with altitude (p<0.01), and reduced amplitude but faster latency with exercise (p=0.03). CONCLUSIONS: Acute exposure to simulated altitudes slows behavioral cognitive reaction time on executive function tasks while preserving task accuracy. An acute bout of moderate intensity cycling exercise improves reaction times so that they are comparable to those achieved without exercise or simulated altitude exposure, at least in instances where exercise does not exacerbate the peripheral oxygen saturation drops seen with simulated altitude.