Pediatric Exercise and Genomics Research Center, University of California at Irvine, Irvine, California, USA.
Pediatric Pulmonary Division, Ruth Children's Hospital, Rambam Health Care Center, Haifa, Israel.
Physiol Rep. 2022 Aug;10(15):e15397. doi: 10.14814/phy2.15397.
Natural patterns of physical activity in youth are characterized by brief periods of exercise of varying intensity interspersed with rest. To better understand systemic physiologic response mechanisms in children and adolescents, we examined five responses [heart rate (HR), respiratory rate (RR), oxygen uptake (V̇O ), carbon dioxide production (V̇CO ), and minute ventilation (V̇E), measured breath-by-breath] to multiple brief exercise bouts (MBEB). Two groups of healthy participants (early pubertal: 17 female, 20 male; late-pubertal: 23 female, 21 male) performed five consecutive 2-min bouts of constant work rate cycle-ergometer exercise interspersed with 1-min of rest during separate sessions of low- or high-intensity (~40% or 80% peak work, respectively). For each 2-min on-transient and 1-min off-transient we calculated the average value of each cardiopulmonary exercise testing (CPET) variable (Y̅). There were significant MBEB changes in 67 of 80 on- and off-transients. Y̅ increased bout-to-bout for all CPET variables, and the magnitude of increase was greater in the high-intensity exercise. We measured the metabolic cost of MBEB, scaled to work performed, for the entire 15 min and found significantly higher V̇O , V̇CO , and V̇E costs in the early-pubertal participants for both low- and high-intensity MBEB. To reduce breath-by-breath variability in estimation of CPET variable kinetics, we time-interpolated (second-by-second), superimposed, and averaged responses. Reasonable estimates of τ (<20% coefficient of variation) were found only for on-transients of HR and V̇O . There was a remarkable reduction in τHR following the first exercise bout in all groups. Natural patterns of physical activity shape cardiorespiratory responses in healthy children and adolescents. Protocols that measure the effect of a previous bout on the kinetics of subsequent bouts may aid in the clinical utility of CPET.
自然状态下的青少年体力活动模式表现为短暂的不同强度运动期与休息期相交替。为了更好地理解儿童和青少年的系统性生理反应机制，我们检测了五次短暂运动（MBEB）的五个反应[心率（HR）、呼吸频率（RR）、摄氧量（V̇O）、二氧化碳生成量（V̇CO）和分钟通气量（V̇E），均进行了逐次呼吸测量]。两组健康参与者（早青春期：17 名女性，20 名男性；晚青春期：23 名女性，21 名男性）在低强度（约 40%峰值工作）或高强度（约 80%峰值工作）的运动中分别进行了五组连续 2 分钟的恒功自行车运动，每组运动之间穿插 1 分钟的休息期。对于每个 2 分钟的过渡期和 1 分钟的间歇期，我们计算了每个心肺运动测试（CPET）变量的平均值（Y̅）。在 80 个过渡期中有 67 个出现了显著的 MBEB 变化。所有 CPET 变量的 Y̅在每个周期中都逐渐增加，并且在高强度运动中增加幅度更大。我们测量了 MBEB 的代谢成本，并将其按所完成的工作量进行了标准化，结果发现，在低强度和高强度 MBEB 中，早青春期参与者的 V̇O、V̇CO 和 V̇E 成本均显著更高。为了减少逐次呼吸估计 CPET 变量动力学的变异性，我们对响应进行了时间内插（每秒一次）、叠加和平均。仅对 HR 和 V̇O 的过渡期找到了合理的 τ（<20%的变异系数）估计值。所有组在第一次运动后 HR 的 τHR 显著降低。自然的体力活动模式塑造了健康儿童和青少年的心肺反应。测量前一回合对随后回合动力学影响的方案可能有助于 CPET 的临床应用。
