The chemoreflex in young boys and girls

In order to determine the influence of the chemoreflex on the cardiovascular system of young children, 35 boys and 35 girls (all 7 - 9 years old) performed three minutes of 30 % maximal voluntary contraction (MVC) static handgrip (SHG) exercise followed by four minutes of blood flow occlusion in the previously exercised arm, and then six minutes of passive recovery. Heart rate (HR) and blood pressure (BP) were measured each minute. Twenty girls performed a second occlusion trial to determine reliability. Reliability coefficients for HR (R = 0.51 - 0.78), diastolic (R = 0.46 - 0.81) and systolic (R = 0.57 - 0.78) BP throughout the occlusion trial were moderately high. There was a similar increase in HR (19 +/- 8 vs. 16 +/- 10 %), diastolic (34 +/- 12 vs. 34 +/- 16 %) and systolic (18 +/- 9 vs. 15 +/- 7 %) BP in boys and girls, respectively, during three minutes 30 % MVC exercise. During the occlusion period, diastolic (43 +/- 31 vs. 47 +/- 26 %) and systolic (51 +/- 25 vs. 54 +/- 32 %) BP dropped similarly during minute one but remained elevated significantly above baseline in both boys and girls the entire four-minute period. During the recovery period, minute one SBP and DBP dropped similarly in boys (23 +/- 37, 20 +/- 37 %) and girls (20 +/- 38, 12 +/- 38 %), respectively. In boys and girls DBP remained significantly above baseline the entire recovery period. HR in boys and girls returned to baseline immediately following SHG exercise and remained there through recovery. In conclusion, as reported in adults, the drop in HR to baseline during post-exercise ischemia with a concomitant maintenance of BP significantly above baseline indicates that at least two separate mechanisms, with varying influence, are responsible for HR and BP control in young children. Further, the chemoreflex operates similarly in young boys and girls.