Why you shouldn’t do cardio immediately after a strength session!

The number of times I’ve seen people going for a run immediately after a strength session, is countless. They are undoing all the hard work they have just put in. 

During strength training you are stimulating the mammalian target of rapamycin or mTOR intracellular signalling pathway, mTOR being the primary pathway for increased protein synthesis and muscular hypertrophy.  MTOR signalling intensifies the synthesis of the amino acid chain, increasing protein synthesis and promotes muscle growth. In other words,  the chemical signal tells your body to grow and therefore muscles get bigger. 

Doing aerobic exercise immediately after a strength session will deregulate the mTOR signalling pathway. All the hard work you put into your strength session to stimulate the mTOR pathway to tell your body to grow and adapt is suddenly turned off and the stimulus from the training is reduced. 

Diagram: Molecular signalling cascades that are involved in myofibrillar muscle protein synthesis and mitochondrial biogenesis in response to physical exercise and specific amino acids or their derivatives. Many amino acids derived from food protein promote the activation of mTORC1 and increase protein synthesis by signaling through Rag GTPases.

So when can you train?

A recent study in the journal of strength and conditioning research (2016), aimed to determine whether the amount of recovery between a strength and an aerobic workout influenced the response to the training program.  The study concluded that S&C coaches should avoid scheduling two contradictory qualities (like running and weightlifting, or swimming and powerlifting) with less than a six-hour recovery period between them if the goal is to obtain full adaptive responses from each workout.

Avoid scheduling two contradictory activities with less than a six-hour recovery period between them.

If your aim is to get strong, there is some significant detriment that cardio can have on strength development. This is true whether you do the cardio workout in the same workout, or if you simply do cardio less than six hours before your weight training.

The researchers who performed this study also stated that daily training without a recovery period between sessions (or training twice a day) is not optimal for neuromuscular and aerobic improvements. So ideally, if you want to get stronger, you should separate your cardio and strength workouts by more than six hours.

When you are trying to get or stay fit, it can help to do a combination of endurance and resistance training—but that is not always optimal for your fitness goals. Choosing which you should do first is often a matter of determining what your goals are.

If your focus is:

• To build strength-stick to doing your resistance training as a separate workout.

• Training for endurance-focus on a high-quality cardio workout that isn’t interrupted by strength training. 

• For pure fat loss- consider combining your cardio and resistance training in one workout, with cardio first followed by strength training. 

If you don’t have time to do a separate strength and a cardio workout, then do it all in one big workout with cardio first followed by strength training. You’ll see improvements in VO2max, strength and lean body mass but it’s not the optimum way to train. However, it will negate cardio turning off the mTOR pathway. 

If you’re doing a cardio and strength session in the same day, separate them with at least 6 hours between them.