REHIT uses very short, maximal-effort sprints to create a strong training stimulus in a very small amount of time. Although the total workout is brief, these intense efforts trigger cardiovascular and muscular adaptations that can improve aerobic fitness when repeated consistently. Research on REHIT and other low-volume sprint protocols supports meaningful improvements in maximal aerobic capacity despite a low overall training volume.

The principle is not that “shorter is always better,” but that carefully controlled intensity can make a short session highly effective. CAROL personalizes the resistance so the REHIT effort is matched to the individual.

For most people, 2–3 REHIT sessions per week is a practical target. Two sessions per week can be sufficient if your main goal is improving cardiorespiratory fitness, while CAROL generally recommends three sessions per week for a more complete training routine.

A standard CAROL REHIT session can be completed in about 5 minutes, although other CAROL workout formats may take longer. At MobiGym, frequency should be adapted to your fitness level, goals, recovery and the rest of your training program.

Yes, CAROL can be suitable for beginners because the resistance and workout intensity are personalized to the individual, and the platform includes easier REHIT variations such as Energizer with 2×10-second sprints. CAROL describes Energizer as its easiest REHIT variation, with shorter maximal-effort sprints plus warm-up and cooldown. ​

At MobiGym, we introduce CAROL progressively based on your current fitness level, training history and recovery. If you are new to exercise or have relevant health concerns, it is sensible to discuss whether high-intensity training is appropriate before starting. CAROL itself advises people new to exercise or managing health concerns to seek medical guidance before beginning.

CAROL’s REHIT protocol is designed to improve cardiorespiratory fitness with very little training time. In one 8-week study, participants following REHIT improved VO₂max by approximately 12% on average, with greater improvements than traditional moderate-intensity continuous training. Individual responses vary.

Other research on REHIT has also shown improvements in aerobic fitness and selected cardiometabolic markers, although results depend on the individual and the population studied. At MobiGym, we prefer to track your progress objectively over time rather than promise a specific result.

CAROL and Peloton are designed for different training experiences. Peloton focuses largely on instructor-led classes, variety, motivation and community, while CAROL is specifically designed around AI-personalized REHIT and highly time-efficient cardiovascular training.

CAROL automatically adjusts resistance to the individual and uses very short, high-intensity efforts as part of its REHIT protocol. For someone whose priority is improving cardiovascular fitness with minimal training time, CAROL offers a very different approach from a traditional indoor cycling workout.