Respiratory muscle training and its effect on cognition during exercise at altitude
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Deficits in exercise endurance and cognitive function have been observed at altitude for hundreds of years. Respiratory muscle training (RMT) has been demonstrated as an effective means of improving exercise performance in divers as well as in sea-level experiments. It has also been shown to decrease the work of breathing and improve the mechanical efficiency of breathing. It is however, unknown if respiratory muscle training is effective during exercise at altitude. Furthermore, the changes in breathing pattern imposed by respiratory muscle training and how they relate to cognitive function during exercise at altitude, have not been elucidated. Cognitive function of five male subjects (21.2 ± 1.3 years) was tested at an altitude of 10,000 feet during exercise at 75% of their VO 2 peak. Three different tests were used: the Digit-Span Forward test, Stroop Color Word test, and Symbol Digit Modalities test (SDMT). Cerebral blood flow velocity and oxygenation were measured with transcranial Doppler and cerebral oximeter, respectively, due to the role of cerebral oxygenation and blood flow in altered cognitive function. Exercise testing at altitude revealed a significant improvement in time to exhaustion in all subjects (Pre-RMT 17.28 ± 4.25 vs. Post-RMT 24.11 ± 2.19; p = 0.01). Measures of cerebral oxygenation and blood flow velocity revealed no significant changes. There was a significant improvement in Stroop Color Word test scores (Pre-RMT 53.4 ± 8.79 vs. Post-RMT 62.6 ± 7.96; p = 0.007). No significant changes were observed in the Digit Span Forward test and SDMT. These results suggest four weeks of RMT may improve cognitive function during exercise at altitude.