Walk–run transition in young and older adults: with special reference to the cardio-respiratory responses

Cardio-respiratory responses of young and older subjects performing walking and running protocols at the walk–run transition speed (WRT) were compared. A total of 26 volunteers assigned to younger (YG, 24 ± 3 years) and older (OG, 64 ± 6 years) groups underwent a protocol to determine the WRT used in 6-min walking and running protocols. Oxygen uptake ( V O 2 ), ventilation ( V E ), expired carbon dioxide ( V CO 2 ), heart rate (HR) and perceived exertion (RPE) were assessed. Oxygen pulse (O 2 pulse) and respiratory exchange ratio (RER) were calculated. The WRT was not different between groups (OG: 6.84 ± 0.69 km h −1 vs. YG: 7.04 ± 0.77 km h −1 , P = 0.62). No between-group differences were found within a given gait pattern for V O 2 ( P = 0.061) and V CO 2 ( P = 0.076). However, V O 2 ( P = 0.0022) and V CO 2 ( P = 0.0041) increased in OG when running, remaining stable in YG ( V O 2 : P = 0.622; V CO 2 : P = 0.412). The VE was higher in OG compared to YG in walking ( P = 0.030) and running ( P = 0.004) protocols. No age-related ( P = 0.180) or locomotion ( P = 0.407) effects were found for RER. The HR increased in OG and between-group difference was detected while running ( P = 0.003). No within- ( P = 0.447) or between-group ( P = 0.851) difference was found for O 2 pulse. The net V O 2 increased from walking to running in OG ( P