There is an old adage in bodybuilding, whatever builds muscle, keeps muscle. As we all know, lifting weights at the correct levels of intensity is the best way to build muscle, but we also have to acknowledge that it is possible to still develop muscle whilst performing cardio. Various types of circuit training and high intensity functional cardio have the potential to tax both the cardiovascular system and stimulate muscle growth simultaneously.
If we consider that we view our training stimulus on a continuum, starting with the highest possible intensity (by intensity we mean the load we are trying to lift), this targets muscular strength. As we lower the intensity, this then moves to those repetition ranges that stimulate muscle growth optimally, then lowering the intensity again, we move into muscular endurance and then onto cardiovascular exercise.
It may seem then that cardiovascular exercise at low or moderate intensities, the type of steady-state cardio performed by bodybuilders and physique athletes trying to get ‘shredded’, should be the last thing that they should be doing to retain muscle when dieting. Instead they should be focusing on high intensity interval training and high intensity functional training (using strongman carries, kettlebells, battle ropes etc. in high intensity intervals) which sits more closely on our continuum to the stimulus of muscle growth, thus promoting the retention of more muscle.
However, we need to consider another important factor in this equation, what other training is that person doing? It certainly holds true that if we are only doing cardio, then higher intensity training is the way to go to protect muscle, but depending on how long this phase lasts and in the population, we might get some muscle loss. For a beginner, this type of training can help grow muscle and improve fitness at the same time, hence its popularity with personal trainer to ‘get the best of both worlds’ out of new clients, stimulating muscle growth and a high energy output in a short period of time to lower body fat. But if we are talking about a seasoned bodybuilder, with a ton of muscle, by reducing the effective stimulus they may indeed lose some muscle, as this type of training cannot replicate the same stimulus required to grow muscle; therefore, the body will adapt to the new demands and reduce muscle tissue.
It is for this reason that for those looking to maintain muscle when dieting still need to lift weights and try to maintain the same intensity and training volume in their sessions, with cardio added in for its energy output increasing effects. In this situation, where weight training is still a big focus in training, the type of cardio performed is going to be less of an issue in terms of muscle loss, simply because we are still generating the stimulus to keep muscle on a daily basis – any muscle loss at this point is then likely to be caused by ‘over-dieting’, not providing the right amount of nutrients and energy to protect muscle tissue.
It really does just come down to two things in this situation: Firstly, how much time do you have? HIIT is a short, sharp and is of high-energy demand, so suits people on a ‘time budget’ who still want to get in a full weights session. For those with more time, they may choose to do longer periods of less demanding, lower-intensity cardio. Secondly, it’s what people enjoy. Some people prefer the variety high-intensity training can offer, using different bits of cardio and resistance training equipment, whereas steady state cardio can be boring for some, but others use it as an opportunity to watch films, listen to podcast and read – something that you definitely could not do if working in high intensity intervals!
In conclusion, high intensity interval training and especially functional training best replicated the conditions for muscle growth and therefore is best for muscle retention when performed as a standalone activity. However, if we consider cardio as an add on to resistance training, the differences between low intensity and high intensity cardio are likely to be small, as we are providing the correct stimulus to retain muscle in other aspects of our training.
Paul Rimmer (BSc, MSc, PhD).
