Author(s): OPAZO, E., CESPEDES, C., ACEITUNO, H., TORRES, M., Institution: UNIVERSIDAD DE CÁDIZ, Country: SPAIN, Abstract-ID: 2026

INTRODUCTION:
Recent research reveals varying internal load responses across exercise intensity domains, notably about heart rate (HR). Controversy has emerged in distinguishing the behavior of HR responses between moderate and heavy-intensity domains. This study aims to evaluate the HR response during a constant load test and compare the slope of the HR between below and above ventilatory threshold 1 (VT1) loads.
METHODS:
Five participants (four males) with a mean age of 30.6 years (± 6.5), BMI of 22.8 (± 3.92), and maximal oxygen consumption of 59.8 ml/min/kg (±11.54) were evaluated. Participants completed two assessment sessions on different days: one session consisted of a maximal oxygen consumption test on a cycle ergometer, and the other day included two constant load tests. These constant load tests consisted of two 7-minute stages of a 10% peak power output difference, with one below and the other above VT1. A self-selected cadence was maintained during the test, with a 12-minute rest between evaluations. A cycle ergometer was adjusted according to each participants anthropometry, along with a heart rate band and a gas analyzer were used. The slope of heart rate during minutes 2-7, 3-7, 4-7, and 5-7 was analyzed, comparing below and above VT1 stages with the Wilcoxon test and significance of 95%.
RESULTS:
The HR median (min; max) slope for 2-7 min was 0.291(0.116;0.411) for below and 0.389 (-0.029;0.564) for above, for 3-7 min: 0.157 (0.088;0.500) and 0.350 (-0.215;0.410), for 4-7 min: 0.257 (0.072;0.469) and 0.331 (-0.422;0.478), and for 5-7 min: 0.258 (0.210;0.440) and 0.298 (-0.925;0.514) beats per min/min. There was no significant difference between the below and above VT1 comparisons (p>0.05).
CONCLUSION:
We found no stabilization of the HR response even below VT1 in trained cyclists. Among the cyclists analyzed, one consistently exhibited a negative slope of HR above VT1 during the windows examined. The median HR slope comparison below and above, calculated across various time windows, indicates an increase at 2-7, 3-7, and 4-7 minutes, but not at 5-7 minutes, albeit without significant differences. Additional volunteers are needed, and more complex analyses are required to enhance the reliability of our conclusions.