抄録
Sudden cardiac death is a common cause of death during hiking activities. Since the exaggerated blood pressure (BP) response to physical activity is known to increase the risk for the development of cardiovascular events, hiking might also induce an excessive BP response and such events. The purpose of this study was to investigate the effects of hiking at around 1,200 m on the circulatory responses to isometric handgrip (IHG) exercise. Five healthy women volunteered to hike and stay at Mt. Ibuki (altitude, 1,377 m; Shiga, Japan) for 2 consecutive days. On the first day, the participants ascended to 1,220 m (Hiking study), and on the second day, they drove to an altitude of 1,260 m where they remained for about 5.5 h (Staying study). The participants performed IHG exercise before (altitude, 220 m), during (altitude, 990 m), and after (altitude, 220 m) hiking in the Hiking study, and before driving (altitude, 160 m), after staying for 5 h (altitude, 1,260 m), and after driving back from an altitude of 1,260 m (altitude, 122 m) in the Staying study. The participants performed IHG exercise at 30% maximum voluntary contraction for 2 min after seated rest. We measured systolic and diastolic BP (SBP and DBP), and pulse rate during the test, and then calculated the double product (DP) from the product of the SBP and pulse rate. In the Hiking study, SBP and DP responses to IHG exercise during hiking were significantly augmented (P < 0.05). Importantly, these responses to IHG exercise during hiking were significantly higher than those before hiking (P < 0.05). On the other hand, in the Staying study, staying at an altitude of 1,260 m for about 5.5 h did not significantly change circulatory responses to IHG exercise. In conclusion, we demonstrated that SBP and DP during IHG exercise were significantly augmented during hiking at an elevation difference of about 1,000 m. This finding suggests that transient increases in BP due to physical activity, which might trigger cardiovascular events, could be enhanced during hiking at a moderate altitude.
