Purpose:
Although maximal heart rate (HR_max) is used widely to assess exercise intensity in training, there are limited data with regards to the validity of age-based prediction equations of HR_max in volleyball players. Therefore, the aim of the present study was to compare the measured-HR_max of two prediction equations (Fox-HR_max = 220 − age and Tanaka-HR_max = 208 − 0.7 × age) in young female volleyball players.

Methods:
The study involved 47 volleyball players (age 13.39 ± 2.01 years, body mass 54.0 ± 10.8 kg, height 162.7 ± 10.2 cm) who performed a graded exercise field test (20 m shuttle run endurance test) to assess HR_max. Measured-HR_max values were compared with the Fox and Tanaka prediction equations.

Results:
The results showed that mean scores for HR_max significantly differed between measured and predicted values (p < 0.001, ŋ² = 0.49). Post-hoc tests revealed that Fox-HR_max overestimated measured-HR_max (mean difference 5.7 bpm; 95% CI [3.0, 8.5]), whereas Tanaka-HR_max was similar to measured-HR_max (-2.2 bpm; 95% CI [-4.9, 0.4]). HR_max did not correlate with age (r = 0.16, p = 0.291).

Conclusions:
The results of this study failed to validate the widely used ‘220−age’ formula in volleyball players. Coaches and fitness trainers should take into account that the overestimation of HR_max by the Fox equation might lead to prescribing exercise at a higher intensity than what is targeted. Therefore, the Tanaka equation appears to offer a more accurate prediction equation of HR_max than the Fox equation in young female volleyball players.