Effect of sprint training on health outcomes in individuals with obesity

Exercise testing The exercise testing was conducted on three different days (D1, D2, and D3) separated by 48h between each testing session. The exercise testing was performed at the beginning of the training program, after 6 weeks and at the end of the 12 weeks. The maximal incremental exercise test On D1, participants underwent an incremental exercise test to exhaustion on a cycle ergometer (Ergoline, ER900, Germany) to determine Maximal Aerobic Power (MAP) and peak oxygen uptake (VO2peak). During the test, respiratory-gas exchange was measured breath-by-breath using a calibrated portable telemetric system (Cosmed K4b2, Rome, Italy) and data was reported as an average of 30-s intervals. Heart rate (HR) was recorded through an ECG Screening. Participants began cycling at 75W for 4 minutes, and then 2 stages of 6 minutes at 90W and 110W and afterward the power output was progressively increased by 20 W every 2 min until exhaustion. The achievement of VO2peak has been based on at least 3 of the following criteria: a plateau in oxygen consumption despite an increase in exercise intensity, a respiratory exchange ratio greater than 1.1, a maximal heart rate above 90% of the predicted maximal theoretical heart rate (220 – age in years), and the apparent exhaustion of the subject. Force–velocity test (F/V) On D2, the F/V test was performed on a cycle ergometer (Monark, Sweden) using a technique adapted from earlier studies. Participants warmed-up for 10 min at 60W. After 5 min of passive recovery, they underwent a succession of supramaximal bouts of approximately 6 s. The braking force administrated at the beginning of the sprint cycling was 2kg and then it was increased by 2 kg after each bout until inability to pursue the test. 5 min of passive recovery was taken after each cycling sprint. Power output was calculated by multiplying the load and speed, and a power curve was then compiled for each bout. The optimal load (Lmax) corresponding to the test was used for the cycling sprint test (CST) on D3 and the maximal power (Ppeak) was used for the training programme. CST On D3, participants arrived at the laboratory after a 12-hour fast. They were provided a standardized breakfast (650 Kcal, 55% carbohydrates, 33% lipids, and 12% proteins) before performing the test. They warmed up for 15 min at 60 W and performed the CST test, which consisted of performing 7 repetitions of 6-s "all out" sprints, on cycle ergometer (Monark, Sweden) interspersed with 90 s of passive recovery. They were asked to cycle as fast as possible during the whole test. The velocity was recorded throughout the trials and served to determine the mean power output (Pmean): the mean of repetitions and the maximal power output (Pmax): the best power outputs developed during the CST. The percent Work decrement (WD%) was calculated according to this formula, since the percentage decrement calculation seems to be the most valid and reliable method of quantifying fatigue : WD% = 100 - (Total work / ideal work × 100) The total work was the sum of all sprint bouts work and the ideal work was the work corresponding the highest bouts performance. Training Program Participants underwent 12 weeks of training supervised sessions. The program was divided into 2 same parts (2 x 6 weeks) between which, mid-training assessment for Force/Velocity test was performed in order to adjust training load. The SIT protocol training consisted of 4 sessions per week. Each session began with 10 min warm-up at 60 W and ended with 5 min cool-down for a total session time of ~ 30 min. Exercise session included 3 sets of repeated 3 × 10s of "all out" sprints. Participants were asked to pedal at maximal velocity against a resistance corresponding to 75%-100% Ppeak separated by 90s of passive recovery between cycling bouts and 5 min of passive recovery between each set. Progressive overload was applied by increasing the number of sprint repetitions and/or 5% Ppeak. The training program was performed in the laboratory and supervised by two sport scientists. Each training session was delivered two-on-two and the adherence was monitored for each participant.