HIIT has a reputation as a fat-burning workout, and it earns it. But a lot of people assume that's all it does, and that if you want muscle you have to go and lift in a traditional gym. So, does HIIT build muscle? Yes, it can, particularly if you're newer to training and the classes include proper resistance work. There are limits, though, and it helps to know where they are.

At HIIT West Hampstead, we believe HIIT is the most time-efficient way to exercise because it improves fitness and strengthens muscle at the same time. Here's how that works in practice, and when it's worth adding something more strength-focused. For the wider picture, see how HIIT supercharges strength, stamina and metabolism.

Does HIIT build muscle? How it works

Muscles grow when you give them a challenge they aren't used to, then let them recover. Squats, lunges, presses, rows and kettlebell swings under fatigue all do that, especially for beginners and people coming back to exercise. In the first few months, most members notice firmer legs, a stronger core and more shape in their shoulders and arms.

What HIIT does less well is heavy, progressive loading. When the goal is to keep moving and keep your heart rate up, you usually can't lift your heaviest weights with long rests. Over time, if you want significant strength or size, you need sessions built around adding load week by week.

Which classes build the most muscle

Not all HIIT is equal when it comes to strength. Here's how our classes compare.

If muscle is your main goal, prioritise HIIT Strength and TRX, and consider adding Small Group Personal Training. SGPT uses heavier weights, follows a structured progression and gives you close technique coaching, which is exactly what muscle growth needs once the beginner gains slow down.

Two myths worth clearing up

The first is that lifting weights will make you bulky. It won't, at least not by accident. Building a lot of size takes years of focused training and eating, and what most people get from HIIT and SGPT is a firmer, stronger version of their current shape. The second myth is that cardio-heavy classes 'eat' your muscle. As long as you eat enough and include resistance work each week, HIIT supports muscle rather than taking it away.

Why muscle matters even if fat loss is your goal

Even if all you want is to lose fat, building some muscle helps. It changes your shape so you look leaner at the same weight, it supports your metabolism and it makes everyday life easier. Carrying shopping up the stairs, lifting a child and getting off the floor are all functional movements, and functional training is what all our HIIT classes are based around. We explain more in our guide to functional fitness workouts.

How to get more muscle from HIIT

• Choose the heaviest weight you can move with good form, not the one you picked last month.
• Book strength-based classes at least twice a week.
• Eat enough protein and don't train on an empty tank. Our guide to pre-workout nutrition covers the basics.
• Sleep properly. Muscle is built during recovery, not during the class.
• Train your core with purpose. Our core strengthening guide has exercises to start with.

For the best of both, we recommend combining SGPT for strength with HIIT classes for fitness. Many of our members do exactly that, and our coaches can build a combo membership around your goals. Have a look at the prices page or get in touch to talk it through.