Reducing Circulating Sphingolipid Levels to Optimise Cardiometabolic Health - The SphingoFIT Trial

The exercise intervention will consist of a supervised HIIT (two walking- and one indoor cycling-based session weekly), starting with a habituation week at an intensity of 75% of the maximal heart rate (HRmax). In the following seven weeks, the participants will perform a HIIT based on the following protocol and for a total duration of 45 min per session: warm-up for 10 min at 60%-70% HRmax followed by a high-intensity interval consisting of 4×4 min at 80%-95% HRmax with 3 min of active recovery at 60%-70% HRmax and a 10 min cool-down at 60%-70% HRmax. Heart rate will be monitored during training by Garmin HRM-Dual heart rate sensors combined with Garmin Forerunner 45S watches. Exercise scientists motivate the participants during the intervals and will control each participant's heart rate during and after every training session.

Asking physically inactive participants to maintain their inactive habits may not reflect realistic conditions and is no longer considered the best option in a randomised controlled exercise intervention. Indeed, most participants will be aware of the positive effects of PA - or will become aware of them during an exercise intervention study. Further, denying an exercise intervention to participants who would have benefited from it (for instance, participants at risk of cardiometabolic diseases) might be ethically questionable. In accordance with current practices, control group participants will be informed about the World Health Organization physical activity guidelines at the beginning of the study.