How Can You Improve Your Cardio Without Hindering Your Gains?

The cruel reality of our current understanding of sport adaptation is that muscle building and endurance training seem to interfere with each other. The more you look into it, it becomes apparent that in order to maximise one you must, to some extent, sacrifice the other.

You can’t fulfil your ultimate potential as a weightlifter and a marathon runner at the same time.

However, endurance and strength can be developed simultaneously to some degree. As it’s often the case with life’s most interesting questions, the answer to ‘is it possible to improve endurance without hindering strength?’ boils down to ‘it depends.’

Outside of running very long distances on a flat surface and powerlifting, very few sports require only endurance or only strength, but use some combination of both. In fact, for the vast majority of sporting activities – and day-to-day life – people rely on both muscle strength and endurance capacity to perform optimally.

Why Introduce Cardio in the First Place?

The adaptations that result from aerobic exercise – running, rowing, swimming, etc. – are pretty different from the ones produced by strength training. They include:

• Strengthening your heart
• Stimulating the growth of mitochondria
• Increased number of small arteries that circulate blood

Building strength mostly requires you to increase the size of your muscle fibres and improve your neural pathways to become more efficient.

Both types of exercise are important, but either is good on its own. Besides, whatever sport your practice, studies show you can perform at your best for longer if you’re aerobically fit.

CrossFit workouts, so long as you maintain a consistently high intensity and little breaks, are a great way to keep the heart rate high enough to get both aerobic and muscular benefits.

The Concurrent Training Effect

The development of high-level endurance seems to hinder the development or maintenance of muscle mass and strength. This interaction between the two is known as the concurrent training effect.

Part of the reason it is believed that endurance training hinders muscle growth has to do with slightly complicated molecular pathways.

It is believed that endurance exercise activates a protein called AMPK (monophosphate-activated protein kinase) which, along other processes, produces endurance adaptations. The muscle hypertrophy response to resistance training happens through a protein called mTOR (mechanistic or mammalian target of rapamycin).

Based on rodent experiments, AMPK can inhibit the effects of mTOR, so endurance training can block muscles from growing.

However, the picture in humans looks slightly more complicated, and recent evidence seems to suggest that it is possible that a different molecular-signalling pathway hinders muscle growth, one triggered by metabolic stress, caloric deficit, oxidative stress, and aging.

Moreover, effective training is more complicated than molecular biology, and optimising performance oftentimes goes beyond these molecular pathways.

Which should you do first, strength or cardio?

If you want to maximise your training, science has a few recommendations when it comes to what to train first, strength or cardio.

The answer – of course – depends on your goals. In general however, always make sure you have enough energy to make the most of your second session of the day.

Even if you manage to achieve calorie balance over the course of a day, you might end up doing your second session in a low-energy state. Depending on how much exercise you’ve already done, a banana might not be enough before your second session.

This is especially important because, as mentioned above, new evidence suggests it’s other signalling pathways triggered by low glycogen (AMPK) or caloric restriction (SIRT1) that could hinder muscle growth.

It’s also beneficial to mix things up and train either strength or cardio first, both within a single session and from day to day. The variability challenges your metabolism and body.

Read more: 8 Foods to Optimise Muscle Growth and Recovery After Training

How Can You Improve Your Cardio Without Hindering Your Gains?

The short answer, if your goal is health and longevity, is to do both to some extent.

If you want to prioritise one over the other, science would suggest you do the one that matters most to you first, but ensure you’re sufficiently fuelled for your second session to still reap most benefits.

If you’re training both strength and endurance (and this means you’re doing more overall training as a result), caloric deficit could be one of the drivers of the interference effect, so the timing of your workouts is less important than your energy balance when you exercise.

Ultimately, take your lifestyle, time and other requirements into account. Science can explain your physiology and metabolism, but you still need to put in the work.