Stima dell’intensità di esercizio e deriva cardiovascolare: una nuova variabile per i modelli di previsione basati sulla frequenza cardiaca

Regularly practicing physical activity and exercise of adequate intensity and duration improves health and fitness. The intensity of aerobic exercise is commonly estimated using heart rate, but in endurance performance the relationship between heart rate and oxygen consumption may be compromised by cardiovascular drift. This physiological phenomenon mainly consists of a time-dependent increase in heart rate and decrease in systolic volume and may lead to overestimation of absolute metabolic intensity in prediction models based on heart rate. Previous research has established that cardiovascular drift is correlated to the increase in core body temperature during prolonged exercise. Therefore, monitoring body temperature during exercise may allow to quantify the increase in heart rate attributable to cardiovascular drift and consequently improve the estimate of muscular work and energy expenditure. Core body temperature measurement is invasive and may be inappropriate, skin temperature is unreliable, oral cavity temperature is influenced by breathing and ingestion of liquids or food, while the external auditory canal is easily accessible and may be suitable for monitoring body temperature during physical activity and exercise. Based on these premises, an experimental protocol was designed to verify whether the increase in heart rate due to cardiovascular drift is associated with the increase in body temperature measured in the external auditory canal. This experimental protocol is composed of a preliminary phase and two submaximal cycling tests and provides monitoring both the tympanic temperature with a professional infrared tympanic thermometer and ear temperature with a wearable device equipped with contact probe. The preliminary phase includes the collection of baseline data for the classification of subjects and the comparison of the tympanic temperature between right and left ear and between closed and open external auditory canal. The first cycling test consists of an incremental exercise followed by a cool down stage and is used to assess the degree of agreement between the two methods of measuring body temperature, while the second cycling test consists of a prolonged exercise in steady state to moderate intensity in a neutral environment and is used to verify the search hypothesis. Due to the SARS-CoV-2 pandemic and the difficulties encountered in recruiting highly trained athletes, a downsized pilot study was carried out which provided encouraging results overall and allowed the optimization of the experimental protocol.