(33) THE RELATIONSHIP BETWEEN HEART RATE RECOVERY AND MAXIMAL OXYGEN CONSUMPTION ACROSS DIFFERENT GRADED EXERCISE TESTING PROTOCOLS

Purpose: Heart rate recovery (HRR) is a non-invasive marker of cardiac-autonomic control and has been used as an indicator of aerobic fitness. However, limited information exists to determine the relationship between HRR and maximal oxygen consumption (VO₂max) across different graded exercise test (GXT) protocols. The purpose of this study was to determine the relationship between HRR and VO₂max following two different maximal GXT protocols. Methods: Nine adult male participants (age = 22.6 ± 5.4 years, height = 163.8 ± 6.4 cm, weight = 83.8 ± 10.8 kg) completed two randomized GXT protocols separated by 72 hours to one week. The first protocol followed the Astrand method, which maintained a constant speed and increased grade every three minutes until exhaustion. The second protocol was the Bruce protocol, which involved increases in speed and grade every 3 minutes until exhaustion. VO₂max was measured using direct oxygen consumption analysis via a metabolic cart during both protocols. Heart rate was continuously monitored throughout each GXT and during a 3-minute active recovery period. Heart rate during the first minute of the active recovery period was subtracted from maximal heart rate and recorded as HRR. Results: The mean ± SD VO₂max values for the Astrand protocol were 51.0 ± 4.9 ml·kg^-1·min^-1 and for the Bruce protocol 49.9 ± 4.8 ml·kg^-1·min^-1. Following the Astrand and Bruce protocols, HRR1 was 26.9 ± 6.2 beats·min^-1 and 25.5 ± 8.7 beats·min^-1. The correlations between HRR and VO₂max were significant for the Astrand protocol (r = 0.78, p = 0.02) but not for the Bruce protocol (r = 0.39, p = 0.34). Conclusions: This study demonstrates that HRR is significantly correlated with VO₂max following the Astrand protocol but not the Bruce protocol. These findings suggest that the extent to which HRR reflects aerobic fitness may depend on the testing protocol used. Practical Applications: Practitioners can use HRR as a non-invasive, simple tool to assess aerobic fitness, particularly when utilizing graded exercise protocols similar to the Astrand method. However, further research is required with a larger and more diverse sample of participants compared to the current study. Acknowledgements: None