Fig. 6. The relationship between muscle blood flow and heart rate over the range of conditions for which these measurements were made. Muscle blood flow is given as a percentage of resting muscle blood flow (%RMBF) prior to submersion. The second-order regression line was drawn using SigmaPlot with mean heart rate and blood flow values for each condition listed (r²=0.999, P<0.05). N, naive; T, trained; S, submerged; R, resting condition before submersion; PS, 1 min period immediately following completion of the submersion. Values are means ± S.D. (N=15).