Les Mills has a reputation. To some, it's group fitness for people who can't commit to real training. To others, it's the most consistent cardio they've ever done. So what does the science actually say — and does it matter which type of cardio you choose?
The Calorie Burn Question
Research on Les Mills programs like BodyPump, BODYCOMBAT, and HIIT 55 shows solid energy expenditure numbers — often comparable to or exceeding traditional steady-state cardio of similar duration. BODYCOMBAT, for instance, has been studied showing average heart rates in the 75–85% max range for the full class duration.
The Adherence Factor
Here's the thing that the data almost always overlooks: the best cardio is the cardio you actually do. Adherence rates for group fitness classes are significantly higher than for solo cardio. People show up because there's music, a class time, an instructor, and social accountability.
- Structure reduces decision fatigue — you just show up
- Social environment increases perceived effort tolerance
- Fixed class times create routine
- Instructor-led pacing reduces the temptation to go easy
Where Traditional Cardio Wins
Running, cycling, and rowing still have real advantages. They're infinitely scalable, they can be done anywhere, and they allow for precise intensity control — important if you're training for a specific event or using heart rate zones for a structured plan.
For pure cardiovascular adaptation at the elite level, traditional endurance training has decades of research behind it. Zone 2 training in particular — long, slow, aerobic work — builds mitochondrial density in ways that short-burst group classes don't replicate as efficiently.
The Verdict
They're not competing. Do the cardio that fits your life. If Les Mills keeps you showing up consistently, it's doing its job. If you'd rather lace up and run, do that. The enemy isn't group fitness or solo cardio — it's sitting on the couch arguing about which is better.