A male elite KS athlete (age 37, weight 85 kg, height 1.83 m, BMI 25.38 kg/m2) with 5 years training experience, healthy, nonsmoker, normotensive, without musculoskeletal injuries or pains, took part in the study. The subject was asked to (a) refrain from training within 48 h before each trial, (b) maintain his normal dietary habits, stay hydrated and refrain from alcohol intake 24 h before each trial, (c) sleep routine amount of time (8 h) the night before. A written informed consent and a medical history questionnaire were obtained. The study was approved by the Institutional Review Board of CRIAMS-Sport Medicine Centre of the University of Pavia.
In both trials the athlete came to the laboratory at 8:30 a.m. in a fasting condition. After 10 min in sitting position, resting blood lactate (BL) was measured with Lactate Pro 2 (Arkray, Kyoto, Japan) and left arm blood pressure (BP) was measured by a sphygmomanometer. Then a light breakfast of 186 kcal was provided (169 kcal from carbohydrates; 10 kcal from proteins, 7 kcal from fat). This meal was chosen in order to avoid a significant thermogenic response (glucydic meal), due to the short interval of time between its intake and the trial start, as previously demonstrated by Belko et al. . During the first visit, anthropometric data were obtained using a stadiometer (Seca Ltd., Hamburg, Germany). The procedures for both trials are summarized in Fig. 1.
The first trial (KT) was the one hand long cycle half marathon with a 26 kg kettlebell corresponding to 1/3 of bodyweight approximately, for 30 min, without releasing it on the ground and maintaining a constant rhythm (10 repetitions per minute, RPM) paced by a metronome (Fig. 2). After a self-determined mobility warm-up of 10 min, the trial was started. During the trial, BL and BP were assessed at 8, 15 and 30 min during trial and after trial at 4 and 8 min. Post-trial time points for BL determination were previously assessed as optimal for peak BL and 1/2 peak BL measurement after RT routine in the same subject. Metabolic and cardiopulmonary assessments [respiratory exchange ratio (RER), tidal volume (TV), breathing frequency (f), minute ventilation (VE)] were obtained with Quark CPET (COSMED, Rome, Italy); HR was measured with a chest strap HR monitor connected to Quark CPET. Substrate percentage oxidation was assessed from changes in RER along the trial .
At the end of the trial, the rate of perceived exertion was obtained with RPE 6–20 scale [4, 6, 11] (Table 1).
The second trial (TR) consisted of 30 min treadmill running performed at the same average VO2 measured in the first trial (speed 9–10 km/h at 1° uphill inclination). After a self-determined mobility warm-up of 10 min, the trial started and BL, BP, metabolic, cardiopulmonary, and RPE assessments were obtained as previously described for KT.