ORIGINAL ARTICLE Estimation of maximal heart rate using the relationship between heart rate variability and exercise intensity in 40–67 years old men Laura Karavirta Æ Mikko P. Tulppo Æ Kai Nyman Æ David E. Laaksonen Æ Teemu Pullinen Æ Raija T. Laukkanen Æ Hannu Kinnunen Æ Arja Ha ¨kkinen Æ Keijo Ha ¨kkinen Accepted: 21 December 2007 / Published online: 11 January 2008 Ó Springer-Verlag 2008 Abstract Large interindividual variation in maximal heart rate (HR max ) may not be accounted for by age alone. In order to evaluate a novel method in the prediction of HR max , this study examined the profile of HR variability (HRV) during exercise in 40–67 years old men (n= 74). R–R intervals were recorded during supine rest and during a graded exercise test by cycle ergometry until exhaustion. A third-degree polynomial function was fitted to the HRV data recorded during exercise to represent the HRV profile of each subject. The instantaneous beat-to-beat R–R interval variability (SD1), high (HF) and low frequency power decreased between all consecutive exercise intensi- ties (P \ 0.033). The relationship between HR max and a variable illustrating the declining rate of HF (HR HF50% ) was stronger (r= 0.50, P \ 0.001) than between HR max and age (r= -0.36, P \ 0.01). The regression analysis showed that a more accurate estimation of HR max was attained when HRV was used in the equation in addition to age: HR max = 160.633–0.603(age) + 0.441(HR HF50% ) (SEE = 9.8 bpm vs. 11.6 bpm in the equation based on age alone). The decline of HRV during incremental exer- cise seems to be useful for accurate estimation of maximal heart rate. Keywords Graded exercise test  Cardiovascular regulation  Cardiac autonomic function  Maximal oxygen uptake Introduction Maximal heart rate (HR max ) is a frequently used parameter in diagnostic and functional exercise testing as well as in exercise prescription. However, a maximal exercise test requires skilled personnel and supervision of a physician in the case of persons with a moderate or high risk for car- diovascular, pulmonary or metabolic diseases (American College of Sports Medicine 2006). Men aged 45, or more, and women aged 55, or more, entail at least a moderate risk (American College of Sports Medicine 2006). Moreover, maximal exercise testing requires high motivation and a maximal effort of the subject. Therefore, several submax- imal exercise tests have been developed, e.g. (Maritz et al. 1961;A ˚ strand and Ryhming 1954) in order to estimate L. Karavirta (&)  T. Pullinen  K. Ha ¨kkinen Department of Biology of Physical Activity, University of Jyva ¨skyla ¨, P.O. Box 35, 40014 Jyva ¨skyla ¨, Finland e-mail: laura.karavirta@sport.jyu.fi M. P. Tulppo Department of Exercise and Medical Physiology, Verve Research, Oulu, Finland K. Nyman  A. Ha ¨kkinen Central Finland Central Hospital, Jyva ¨skyla ¨, Finland D. E. Laaksonen Department of Medicine, Kuopio University Hospital, Kuopio, Finland D. E. Laaksonen Department of Physiology, University of Kuopio, Kuopio, Finland R. T. Laukkanen  H. Kinnunen Polar Electro Oy, Kempele, Finland R. T. Laukkanen Department of Medicine, University of Oulu, Oulu, Finland A. Ha ¨kkinen Department of Health Sciences, University of Jyva ¨skyla ¨, Jyva ¨skyla ¨, Finland 123 Eur J Appl Physiol (2008) 103:25–32 DOI 10.1007/s00421-007-0667-5