Cycling tests
In the central phase of the study, two submaximal cycling tests will be carried out with non-invasive monitoring of heart rate, external auditory canal temperature and tympanic temperature. The tests will be spaced from a minimum of 24 hours up to a maximum of 10 days. In female athletes, cycling tests will not be performed during the mid-luteal phase of the menstrual cycle to limit the influence on body temperature and heart rate.24
Before performing the cycling tests, the baseline values of heart rate and external auditory canal temperature will be monitored for 10 min with subjects sitting in a comfortable position and after relaxing for at least 20 min. These baseline values will be obtained by averaging the last 5 min of monitoring. The baseline value of the tympanic temperature will be determined by carrying out a measurement at the end of the monitoring of the other physiological variables to avoid influences on the heart rate.
The first cycling test will consist of incremental exercise up to 80% of the theoretical maximum heart rate (HRmax) estimated with the formula 220 − age.25 This test will be necessary to estimate the subject-specific relationship between heart rate and power output, that will be used to determine the power corresponding to the target intensity of the second cycling test. The choice of this submaximal test instead of a maximal test may limit the estimation of the exercise intensity. However, the use of a maximal incremental test with respiratory gas monitoring would require more resources and adequate clinical care limiting the feasibility of the study in a non-hospital setting.
Incremental cycling test protocol:
Initial intensity of 100 W for males and 50 W for females at 70–90 rpm and increments of 25 W every 3 min until achieving and maintaining 80% HRmax for 3 min.
10 min cool down with intensity of 50–100 W at 70–90 rpm.
The second cycling test will consist of a prolonged steady-state exercise at the upper limit of moderate intensity in a thermally neutral indoor environment, with the purpose of assessing the association between trends in heart rate and in ear temperature.
The moderate exercise intensity of the prolonged steady-state cycling test will be estimated using a percentage of heart rate reserve.1 6 26–28 In cardiorespiratory endurance exercise, a moderate level of intensity is between 40% and 59% of heart rate reserve or oxygen consumption reserve.1 The target heart rate (HRtarget) corresponding to the desired exercise intensity will be calculated using the following equation:
where HRmax is the maximum heart rate, HRrest the resting heart rate and % HRR the percentage of heart rate reserve. The target heart rate will be converted into power using the subject-specific relationship between heart rate and power output, in order to maintain the absolute exercise intensity constant.
Prolonged steady-state cycling test protocol:
10 min warm up with increasing intensity until reaching the target (5 min at 50% of target, 3 min at 80% of target and 2 min at 90% of target) at 70–90 rpm.
120 min exercise with intensity equal to the power corresponding to 59% HRR at 70–90 rpm.
10 min cool down with intensity equal to 50% of target at 70–90 rpm.
The cycling tests will be carried out with one of the bicycles usually used by athletes to maximise comfort during the exercise and wearing a light cycling uniform. Bicycles will be mounted (fixing the rear carriage) on a professional training roller with magnetic brake with 30 certified positions (MagneticDays JARVIS, O.R.F. S.r.l.) equipped with software (MD Training, O.R.F. S.r.l.) to develop training protocols, to acquire and transfer data and to view the working parameters in real time (elapsed time, speed, power output, pedalling cadence and heart rate). This professional training roller used for the cycling tests is capable of automatically adjusting the resistance based on the pedalling rate to maintain the power output constant.
During the cycling tests, heart rate, external auditory canal temperature of the right ear and tympanic temperature (infrared radiation) of the left ear will be monitored. Before carrying out temperature measurements, the external auditory canal of both ears will be visually inspected to verify the absence of obstructions and/or anomalies.
Heart rate will be monitored with a wireless chest strap heart rate monitor (Soft Strap Premium Heart Rate Monitor, Garmin Ltd) positioned under the chest. For data transfer, the heart rate monitor will be associated with the training roller through a short-range wireless connection (ant+).
The external auditory canal temperature will be monitored in the right ear through continuous measurement with a wearable device (C-Temp, Cosinuss GmbH) consisting of a retro-ear module and an adjustable contact probe. A firmware modification was made by the manufacturer to obtain absolute temperature values without corrections. For data transfer, the auricular device will be associated with a smartphone or tablet through a short-range wireless connection (Bluetooth). The software application (cosinuss° saveXport, Cosinuss GmbH or cosinuss° Lab, Cosinuss GmbH) provided by the manufacturer allows to view the measured temperature in real time and to acquire data for subsequent transfer to a PC. To ensure the best hygienic conditions, both the ear probe and the retro-ear module will be coated with a disposable cover obtained from a low-weight (~3 g) and small size (S) nitrile glove for food use (nyte, walking, Brenta S.r.l. or Reflexx 77, Reflexx S.p.A.).
To avoid the release of the probe from external auditory canal or unwanted movements, a suitably modified antinoise headband (JAZZ-BAND 2, Moldex-Metric AG & Co. KG) will be used. The modification consists in the partial removal of the support of the right earplug and the insertion on the remaining part of a small cylinder in non-toxic plasticised polyvinyl chloride able to accommodate the base of the probe and exert a slight pressure (~1.2 N). The unmodified contralateral earplug will be positioned at the entrance of the left external auditory canal. To ensure the best hygienic conditions, a disposable nitrile cover will be applied to both earplugs, as in the case of the auricular device. In addition, to adjust the length of the probe and redistribute the pressure exerted by the antinoise headband, disposable cotton pads will be inserted between the probe and the entrance of the external auditory canal.
The tympanic temperature will be monitored in the left ear by manual sampling with a professional infrared tympanic thermometer (Genius 2, Covidien llc) by carrying out the otoscopic manoeuver to straighten the external auditory canal and directing the probe towards the tympanic membrane. This manoeuver, which will be carried out by a trained operator, allows for more accurate tympanic temperature measurements and consists of moderate traction posteriorly and superiorly of the auricle carried out in the midpoint between the apex of the helix and the lower end of the lobule.29 The tympanic thermometer will be set in ear mode (EAR) to obtain absolute temperature measurements without corrections for equivalence with other sites. This instrument is equipped with replaceable probe covers (Tympanic Probe Covers, 303030, Covidien llc) to ensure the best hygienic conditions.
During the incremental cycling test, the tympanic temperature will be measured every 3 min, while in the prolonged cycling test every 5 min. Before carrying out these measurements, the left earplug of the antinoise headband will be temporarily moved to allow access to the external auditory canal.
In order to limit dehydration (body weight loss >2%) during prolonged steady-state test, subjects will take every 10 min a dose of mineral water (SANGEMINI, Acque Minerali d’Italia S.p.A.) at room temperature for a total quantity between 0.4 and 0.8 L/hour, based on the initial body weight.30
Hydration based on athletes’ body weight:
50–<60 kg = 0.4 L/hour.
60–<70 kg = 0.5 L/hour.
70–<80 kg = 0.6 L/hour.
80–<90 kg = 0.7 L/hour.
≥90 kg = 0.8 L/hour.
In order to prevent disorders or discomfort due to permanence on the bicycle during prolonged steady-state test, subjects will perform an out of the saddle every 20 min lasting ~5 s.
Body weight of subjects will be measured before and after the cycling tests with a digital scale (RD-953, innerScan DUAL, TANITA Corporation) to assess dehydration. The measurements will be carried out with the body dry in undergarments and possibly after urinating.
Before the cycling tests, study participants should:
Take at least 1.9 L/day of water in the previous 48 hours.
Take an adequate amount of carbohydrates (~60% of kcal/day) in the previous 48 hours.
Refrain from taking caffeine, alcohol, nicotine or other stimulants for at least 4 hours.
Take the last meal 4–6 hours before.
Refrain from moderate physical activity for at least 2 hours and from strenuous exercise for at least 14 hours.
Take 500 mL of mineral water in the previous 60 min.
Rest for ≥20 min before monitoring the baseline values of the physiological variables.
During this phase of the study, subjects will draw up a diary on the diet and exercise for the 48 hours preceding the cycling tests to assess the congruence with the indications provided.
At the end of the cycling tests, participants will receive packaged food and beverages and a self-compiled questionnaire to investigate the perceived level of comfort/discomfort during the experimental procedures. The questionnaire is composed of the following four items, each based on a 5-point Likert scale: the use of the chest strap heart rate monitor, the auricular device supported by the modified antinoise headband, the tympanic thermometer and the training roller.