Programming Interval Training Based on the HIIT Classification System on Time-Trial Performance v2

Participants will complete a training history and will be characterized with a questionnaire with respect to age, sex and location. Prior to the first testing session, participants will keep a food diary for the day preceeding the testing session to permit replication of diet for other testing weeks. Participants will be provided with a coded TrainerRoad account used to record all testing and training data. Training sessions will be pre-programmed into the TrainerRoad platform. All testing and training will be completed by participants at their residence on their own bicycles with the use of a smart trainer. Participants will complete an incremental exercise test (IET) to determine their maximal power output (Wmax) and two 40-minute Time Trials (TTs). The IET includes a warmup followed by ramp increases in intensity to a voluntary maximum; typically reached after 8 to 12 min.

Testing will be conducted in the 2-weeks prior and the week following the intervention. Once baseline testing is completed, participants will begin the interval training program which will consist of two interval training sessions per week and 2-3 sessions of low-intensity continuous training. There will be assessor blinding since all testing and training will be conducted solely by the participant with guidance from the TrainerRoad software.

MEASUREMENTS Time-Trial Performance The TT test will be performed by each participant on their own bicycle connected to a smart trainer. Following the warmup, participants will complete a 40-minute TT to determine their maximal sustainable power which corresponds to 7-8/10 on the 10 point Borg RPE scale. For the first TT test, participants will set their workload to 65% of the power achieved from the IET. Participants can consume water ad libitum for the duration of the time trial. Heart rate, cadence, mean power output and maximal power output will be recorded using the TrainerRoad platform.

Maximal Power Output (Wmax). The incremental exercise test determines Wmax. The first stage of the assessment will be completed at the same intensity completed during the warmup phase and increased by 12.5 watts every 30-seconds until the participant is unable to maintain a cadence of 70 RPM. All data will be collected using the TrainerRoad platform.

INTERVENTIONS Participants will be randomly allocated to one of four interval training groups via a computer-generated random sequence. Randomization and allocation will be concealed from the investigators. The groups will consist of a long-HIIT, a medium-HIIT matched to long work, a medium-HIIT that is performed at 15% higher intensity (Medium-HIIT-H), and intermittent short-HIIT (Short-HIIT). Each participant will be aware that they will be completing one of four interval exercise programs, however, they will be blinded to the details of the other programs.