Background and objectives: Maximal heart rate (HRmax) is an important training and testing tool, especially in the context of evaluating intensity in exercise prescription; however, few studies have examined the validity of prediction equations of HRmax in physically active female adolescents and the role of maturation level. Therefore, the aim of the present study was to examine the differences between measured and predicted HRmax in a sample of physically active female adolescents. Materials and Methods: Seventy-one selected volleyball players (age 13.3 ± 0.7 years, body mass 62.0 ± 7.2 kg, height 1.72 ± 0.06 m) performed a 20 m shuttle run endurance test, and the actual HRmax was compared with Tanaka HRmax ('208 - 0.7 × age') and Fox HRmax ('220 - age'). Results: A large main effect of assessment method on HRmax was found (p < 0.001, η2 = 0.486) with Fox overestimating actual HRmax by 6.8 bpm (95% confidence intervals, CI; 4.2, 9.3) and Tanaka underestimating actual HRmax by -2.6 bpm (95% CI; -5.1, -0.1). The more matured participants had similar actual HRmax (mean difference -2.4 bpm; 95% CI; -6.5, 1.7; p = 0.242, d = -0.28), difference Fox - actual HRmax (1.5 bpm; 95% CI; -2.6, 5.6, p = 0.466, d = 0.17), and difference Tanaka - actual HRmax (1.7 bpm; 95% CI; -2.4, 5.8; p = 0.414, d = 0.19) to the less matured participants. Conclusions: These findings suggest that age-based prediction equations of HRmax developed in adult populations should be applied with caution in physically active female adolescents, and Tanaka should be preferred instead of the Fox equation.
Keywords: cardiac rate; exercise prescription; exercise testing; prediction equations; training zones; volleyball.