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Will cardio make me lose any muscle gains from lifting weights?


We received a question on facebook from Lisa, about something she has noticed at her club. Nathan and Matt provide Lisa with some helpful information to take back to her participants. 


Hi Les Mills

At one of the gyms I teach a lot of the members also train with a PT. I've found over the last few months numbers have dropped in BODYSTEP® / BODYCOMBAT® / BODYATTACK® classes (not just mine) and when we talk to members, a lot of them say they have cut down cardio and are only doing weights as PT's have advised them if they do long cardio sessions they will lose any gains.

Any advise how to approach this issue?

Thanks, Lisa


Dear Lisa

Very often you won't be getting your regular "buff weights room guy/girl coming to those particular group fitness classes".

Traditionally I've seen a little separation between Personal Trainers and Group Fitness Instructors, mostly due to Personal Trainers not understanding what the Les Mills  programs training focus and outcomes are. A good starting point is to get the Personal Trainers to endorse Group Fitness as a supplement to their weekly training regime.

In regards to undoing lean muscle, it would take regular (3 plus classes a week) to strip lean muscle. If anything these Cardio based classes would act as a supplementary fat burning session to aid in building lean muscle.

Getting your training balance is crucial. We only need to look at Steve Cluff and Lisa Osborne. Both have lots of quality lean muscle mass, yet still do the mentioned programs, making them muscly, yet lean and extremely functional.

Hope this helps,


Hi Lisa

Personal Training and Group Fitness are not mutually exclusive. They are both valid training options when delivered by a competent professional.

There is a great deal of science behind the programming of the Les Mills classes that ensure they deliver quality workouts. Classes such as BODYSTEP®, BODYCOMBAT® and BODYATTACK® for example offer the high intensity style training that is proven to deliver fast fat loss, whilst maintaining lean muscle mass. Not to mention the improvements to balance, coordination, and agility through multi dimensional movement patterns. Great muscle loading and an expansive array of multi joint movements ensure improved functionality and strength gains.

I would say that all educated fitness professionals would agree that a mix of strength training and high intensity cardio is the optimal choice, along with flexibility and mobility to ensure a fit and healthy body. Whilst everybody goes to the gym for different reasons, this four stage approach would cover off the general population who just want to get fit, tone up and lose some body fat.

Gains would be lost due to poor diet, lack of rest and recovery and not training at all.

My simple advice would be to ask the members "Do you like doing group fitness classes?" If the answer is yes, then tell them "Great, then keep doing it!” Keep doing Personal Training as well. Just find yourself a good one.

Hope this helps.