Postexercise heart rate recovery in children: relationship with power output, blood pH, and lactate Martin Buchheit, Pascale Duche ´ , Paul B. Laursen, and Se ´ bastien Ratel Abstract: The aim of the present study was to determine whether differences in age-related heart rate recovery (HRR) ki- netics were associated with differences in power output, blood lactate concentration ([La] b ), and acidosis among children, adolescents, and adults. Ten prepubertal boys (aged 9.6 ± 0.7 years), 6 pubertal boys (aged 15.2 ± 0.8 years), and 7 men (aged 20.4 ± 1.0 years) performed 10 repeated 10-s all-out cycling sprints, interspersed with 5-min passive recovery inter- vals. Mean power output (MPO) was measured during each sprint, and HRR, [La]b, and acidosis (pHb) were determined immediately after each sprint. Children displayed a shorter time constant of the primary component of HRR than adoles- cents and adults (17.5 ± 4.1 vs. 38.0 ± 5.3 and 36.9 ± 4.9 s, p < 0.001 for both), but no difference was observed between adolescents and adults (p = 1.00). MPO, [La]b, and pHb were also lower in children compared with the other 2 groups (p < 0.001 for both). When data were pooled, HRR was significantly correlated with MPO (r = 0.48, p < 0.001), [La]b (r = 0.58, p < 0.001), and pHb (r = –0.60, p < 0.001). Covarying for MPO, [La]b, or pHb abolished the between-group differ- ences in HRR (p = 0.42, p = 0.19, and p = 0.16, respectively). Anaerobic glycolytic contribution and power output ex- plained a significant portion of the HRR variance following high-intensity intermittent exercise. The faster HRR kinetic observed in children appears to be related, at least in part, to their lower work rate and inherent lack of anaerobic meta- bolic capacity. Key words: parasympathetic activity, intermittent exercise, repeated sprints, maturation, pH. Re ´sume ´: Cette e ´tude se propose de ve ´rifier si les diffe ´rences de cine ´tique de la re ´cupe ´ration du rythme cardiaque selon l’a ˆge (« HRR ») sont associe ´es aux diffe ´rences de production de puissance, de concentration de lactate sanguin et d’acidose chez des enfants, des adolescents et des adultes. Dix garc ¸ons pre ´pube `res (a ˆge ´ 9,6 ± 0,7 ans), 6 garc ¸ons pube `res (a ˆge ´ 15,2 ± 0,8 ans) et 7 hommes (a ˆge ´ 20,4 ± 1,0 ans) participent a ` des se ´ances de sprint re ´pe ´te ´a ` plein re ´gime sur un ve ´lo, d’une dure ´e de 10 s et entrecoupe ´ de pe ´riodes de repos passif d’une dure ´e de 5 min. A ` chaque sprint, on e ´value la production moyenne de puissance (« MPO ») et, apre `s chaque sprint, on e ´value l’HRR, la concentration sanguine de lac- tate ([La] b ) et le degre ´ sanguin d’acidose (pH b ). Chez les enfants, on observe une plus petite constante de temps de la composante primaire de HRR que chez les adolescents et les adultes (17,5 ± 4,1 comparativement a ` 38,0 ± 5,3 et a ` 36,9 ± 4,9 s, p < 0,001 pour les deux), mais on n’observe pas de diffe ´rences entre les adolescents et les adultes (p = 1,00). Com- parativement aux 2 autres groupes, les valeurs de MPO, [La] b et de pH b sont aussi plus faibles chez les enfants (p < 0,001 pour les deux). Apre `s regroupement des donne ´es, on observe une corre ´lation significative entre la MPO (r = 0,48, p < 0,001), la [La] b (r = 0,58, p < 0,001) et le pH b (r = –0,60, p < 0,001). La covariation des valeurs de MPO, de [La] b et de pH b abolit les diffe ´rences de HRR entre les groupes (p = 0,42, p = 0,19 et 0,16, respectivement). La contribution de la gly- colyse anae ´robie et la production de puissance expliquent une part importante de la variance de HRR a ` la suite de l’effort intermittent de haute intensite ´. La cine ´tique plus rapide de re ´cupe ´ration du rythme cardiaque observe ´e chez les enfants est probablement le re ´sultat, du moins en partie, de leur plus faible re ´gime de travail et de leur de ´ficience inhe ´rente en matie `re de capacite ´ anae ´robie du me ´tabolisme. Mots-cle ´s : activite ´ parasympathique, exercice physique intermittent, sprints re ´pe ´te ´s, maturation, pH. [Traduit par la Re ´daction] Introduction After a set bout of exercise, the recovery of physiological functions, including heart rate (HR), ventilation, oxygen up- take, and carbon dioxide production, tends to be faster in children compared with adults (for review, see Ratel et al. Received 24 August 2009. Accepted 8 December 2009. Published on the NRC Research Press Web site at apnm.nrc.ca on . M. Buchheit. 1 Research Laboratory, EA 3300, Exercise physiology and rehabilitation, Faculty of Sport Sciences, University of Picardie, Jules Verne, Amiens, France; Performance Enhancement and Talent Identification Section, Aspire, Academy for Sports Excellence, Doha, Qatar. P. Duche ´ and S. Ratel. Laboratory of Exercise Biology (BAPS), Unite ´ de Formation et de Recherche en Sciences et Techniques des Activite ´s Physiques et Sportives (UFRSTAPS), Blaise Pascal University, Clermont-Ferrand, France. P.B. Laursen. School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia. 1 Corresponding author (e-mail: martin.buchheit@u-picardie.fr). Pagination not final/Pagination non finale 1 Appl. Physiol. Nutr. Metab. 35: 1–9 (2010) doi:10.1139/H09-140 Published by NRC Research Press PROOF/E ´ PREUVE