Oxygen uptake (VO₂) and heart rate (HR) were measured during submaximal and maximal work in bicycling in air at 25℃ and tethered swimming in water at 20, 25 and 32°C, in order to compare the response of HR-VO₂, relationship in those four conditions. Subject were six boys from 10 to 12 years.
　The plot of HR-VO₂, was linear in all conditions, but shifted significantly to the right in cooler water. At a given submaximal VO₂, HR in 20℃water was lower by 5.9, 14.7 and 20.0 beats/min than in 25℃ water, 32℃ water and 25℃ air, respectively.
　Regression equations for relationships of HR (y) to % VO₂max (x) were as follows:
　water, (20°C) y=1.09x+56.8 (r=0.912)
　　　　 (25°C) y=1.25x+52.7 (r=0.975)
　　　　 (32°C) y=1.21x+66.7 (r=0.963)
　　 air, (25°C) y=1.21x+73.6 (r=0.964)

DESCENTE SPORTS SCIENCE Vol.9/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE