INTRODUCTION:
Currently, for prescribing physical exercise, heart rate can be used as a parameter, using methods such as the Karvonen® and Tanaka® formulas, and cardiopulmonary exercise testing. With this in mind, the present study aims to verify the relevance of heart rate variability indicators in prescribing physical exercise for people living with HIV.

METHODS:
This is a clinical trial with a sample of 18 individuals of both sexes living with HIV, analyzing resting heart rate and the RMSSD index in the supine position for 15 minutes. After data collection, the values were analyzed, and calculations were performed using the Karvonen® and Tanaka® formulas.

RESULTS:
The differences between measured maximum heart rate and age-estimated maximum heart rate showed a normal distribution (Shapiro–Wilk, p = 0.99). Paired t-test showed no statistically significant difference between the methods (p = 0.39). A similar result was observed in the comparison between exercise heart rate estimation methods using the Karvonen formula with measured maximum heart rate and age-estimated maximum heart rate (p = 0.39). No significant association was observed between maximum VO₂ and RMSSD (ρ = 0.16; p = 0.54). In contrast, maximum heart rate showed a strong positive correlation with maximum VO₂ (ρ = 0.69; p = 0.001). Literature has shown that variability is a parameter to be considered in cardiovascular risk analysis.

CONCLUSIONS:
Prescription formulas are suitable for exercise prescription; however, parasympathetic modulation characteristics obtained through heart rate variability are crucial for interpreting cardioprotection, which is essential for determining training heart rate, given that even with autonomic alterations, the formulas do not analyze these parameters.