Figure 4

Synchronization time T (s) changed with the simulated altitude. The value was 60 ± 26 s, 80 ± 41 s and 113 ± 48 s at sea level (SL), 3000 m and 4000 m, respectively. The T at 4000 m was significantly longer than the value at SL (asterisk indicates P = 0.003) and 3000 m (plus indicates P = 0.040), but there was non-significantly change between at 3000 m and at SL (P = 0.214). The error bars indicated the standard deviation.