[Maximal cardiac rate during treadmill exertion test in 1853 healthy subjects. Its relation with age and under the atmospheric conditions of Mexico City].

Introduction: The relation between heart rate and age during the exercise test is dependent on the altitude over the sea level in which the test is made.

Objective: To observe the behavior of the heart rate during a maximal exercise test and its relation to age and to the altitude of Mexico City.

Method: Observational, non randomized study of 1,853 healthy subjects who underwent maximal exercise test done with Bruce's protocol, in the Department of Cardiology of the Spanish Hospital of Mexico City.

Results: The distribution by age groups showed a normal curve. They were divided by gender (67% males and 33% females) with a mean age of 47.6 +/- vs 49.6 +/- 13.7 years respectively (p = 0.003). Maximal heart rate according to gender (167.9 +/- 17.4 vs 160 +/- 18.2 bpm, p = 0.001). Trained vs sedentary (85.7% vs 14.3%). Maximal heart rate by grade of training (169.1 +/- 16.4 vs 167.6 +/- 17.8 bpm, p > 0.05) and the lineal correlation of maximal heart rate dependent on age of the subject (r-0.61, Y = 204.37 + (-0.810*X), p = 0.001).

Conclusions: The maximal heart rate during maximal exercise test at the altitude of Mexico City is lower than those reported in the literature. This is statistically significant and depends on age and it does not bear any relationship to the degree of training, at least in our subgroup of subjects studied. The same is true for females and the dependence on age remains the same too.