Thieme Castrillón CIM et al. High-Intensity Intermittent Exercise and … Int J Sports Med 2017; 38: 468–472 Training & Testing Introduction Heart rate variability (HRV) has become an accepted method for measuring cardiovascular autonomic modulation [25, 3, 14, 24], and the evaluation of HRV recovery has been presented as an important method to analyze autonomic behavior related to diferent modes of exercise [13, 29, 11]. Moreover, delayed HRV recovery is consid- ered a predictor of mortality and risk of sudden death [17, 25]. Diferent studies have proposed to investigate HRV recovery after exercises with diferent intensity and volume [12, 20, 21], sim- ilar volumes [8], and similar energy expenditure [31] among trained or physically active subjects [8, 33, 30]. These studies have shown that higher exercise intensity leads to slower HRV recovery among physically active subjects, which is an important fnding for exer- cise prescription. Our group recently found that 5 kilometers (km) of high-inten- sity intermittent exercise (HIIE) delays HRV recovery (during 60 min of recovery, root mean square of successive diferences [RMSSD] stayed lower) when compared to a session of moderate-intensity exercise with the same volume [8]. When compared to moderate intensity, HIIE seems to be more efcient to improve body compo- sition and physical ftness [5, 6, 15]; in addition, subjects reach their goals faster with HIIE when compared to moderate-intensity exer- cise (time efciency). Studies that investigated the efect of HIIE usually use 10 bouts of 1-min exercise at maximal aerobic speed (MAS) [34, 32], and physically active subjects would run approxi- mately 2.5 km when performing this training. Nevertheless, the HRV recovery after a 2.5-km HIIE (HIIE 2.5 ) has not been investigat- ed yet; moreover, it is not known whether HRV recovery changes when performing half-distance HIIE (HIIE 1.25 ). Thus, the aim of the present study was to compare HRV recov- ery after an HIIE of 2.5 and 1.25 km. Our hypothesis was that HIIE 2.5 would cause slower HRV recovery than HIIE 1.25 . High-Intensity Intermittent Exercise and Autonomic Modulation: Efects of Diferent Volume Sessions Authors Carlos Iván Mesa Castrillón 1 , Rodolfo Augusto Travagin Miranda 1 , Carolina Cabral-Santos 2 , Lais Manata Vanzella 1 , Bruno Rodrigues 3 , Luiz Carlos Marques Vanderlei 1 , Fábio Santos Lira 2 , Eduardo Zapaterra Campos 4 Afliations 1 Physiotherapy, Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Presidente Prudente, Brazil 2 Exercise and Immunometabolism Research Group, Department of Physical Education, Universidade Estadual Paulista (UNESP) – Presidente Prudente, São Paulo, Brazil 3 Faculty of Physical Education, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil 4 Universidade Federal de Pernambuco, Physical Education Department, Recife, Brazil Key words High-intensity intermittent exercise, recovery, autonomic modulation, heart rate variability accepted after revision November. 10. 2016 Bibliography DOI http://dx.doi.org/10.1055/s-0042-121898 Published online: 7.4.2017 Int J Sports Med 2017; 38: 468–472 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0172-4622 Correspondence Dr. Fábio S. Lira Department of Physical Education, Unesp Rua Roberto Simonsen, 305 19060-900 Presidente Prudente Brazil Tel.: + 55/183/2295 724, Fax: + 55/183/2295 724 fabiolira@fct.unesp.br ABSTRACT The aim of this study was to compare heart rate variability (HRV) recov- ery after 2 sessions of high-intensity intermittent exercise at diferent volumes (1.25 km [HIIE 1.25 ] and 2.5 km [HIIE 2.5 ]). 13 participants deter- mined their maximal aerobic speed (MAS) and completed 2 HIIE (1:1 at 100 % MAS) trials. The heart rate was recorded before and after each session. HRV indicators were calculated according to time (RMSSD and SDNN) and frequency (LF, HF and LF/HF ratio) domains. SDNN and RMSSD presented effect of test (F = 20.97; p < 0.01 and F = 21.00; p < 0.01, respectively) and moment (F = 6.76; p < 0.01 and F = 12.30; p < 0.01, respectively), without interaction. Even though we did not fnd an interaction efect for any HRV variables, the HIIE 2.5 presented a delay of only 5 min in HRV recovery, when compared to HIIE 1.25 . However, the efects of the test (SDNN, RMSSD, LF-log, and HF-log) indicate higher autonomic stress during the entire recovery period. These fndings may indicate that exercise volume interferes with HRV recovery. If so, physi- cally active subjects may choose a lower volume exercise (i. e., HIIE 1.25 ) in order to promote similar physical ftness adaptations with lower load- ing on autonomic modulation. 468 Downloaded by: Dot. Lib Information. Copyrighted material.