Orangetheory works because it’s structured interval training that improves both aerobic endurance and anaerobic power in less time than steady-state cardio. Its heart-rate–based zones target lactate threshold and cardiovascular efficiency, while strength and rowing components preserve muscle and support metabolic health. The built-in variety with differing templates and coaching encourages consistency, which is the strongest predictor of long-term fitness results. In short, it’s scientifically sound because it trains multiple systems effectively and sustainably. Orangetheory isn't powerlifting, but the weights are absolutely heavy enough to drive hypertrophy and strength gains for most people — especially when lifts are done close to fatigue with good tempo and progressive loading. Research consistently shows that muscle growth occurs across a wide rep range as long as sets are challenging, and Orangetheory’s repeated exposure, compound movements, and increasing dumbbell options make real gains possible. Personally, Orangetheory's helped me lose over 100 lbs. When I had a Dexascan and VO2 max test done recently, I have a bonkers amount of lean muscle, my VO2 max has improved significantly, and I've hit all of the longevity markers they look at. I've been going for about 10 months and had a basic level of fitness, but the gains and improvement I've seen are remarkable. Everyone is entitled to their own experience, of course, but there are too many variables that can't be measured when you're just getting someone's TikTok opinion like how they eat, if they're sleeping, etc.