Various athletes and coaches have argued that if one trains for endurance and strength simultaneously, progress in performance will be slower than if you train for each one separately. This is known as the ‘concurrent training effect’. However, there are strategies that can be followed in order to maximize using both effectively. There are two enzymes that play a role in the effect of training on muscle, namely the ‘AMP-activated protein kinase’ (AMPK) and the mammalian ‘target of rapamycin complex 1’ (mTORC1). AMPK improves endurance – It is activated by long bouts of endurance exercisemTORC1, on the other hand, improves strength, and is activated by resistance exercise. The question has arisen that if these two enzymes enhance two different aspects of fitness, why is it difficult to increase both simultaneously? The answer could be that AMPK can block the activation of mTORC1, therefore there is a block to improving both endurance and muscle mass and strength at the same time.
Dynamics of Enzyme Activation
AMPK is turned on during exercise, but it is immediately turned off when we refuel. The reason being is because it senses the amount of glycogen in the muscle - as well as the metabolic state of the muscle. When these return to normal, AMPK turns off. Conversely, mTORC1 is not turned on during exercise, but rather during the recovery period resulting from resistance training. The optimum activation of this enzyme occurs between 30 minutes and six hours after a single session of resistance exercise. The correlation between mTORC1 and strength gains occurs do in fact both occur between approximately 30 minutes and six hours after resistance training – hence it is important to have mTORC1 active for a long time in order for it to influence muscle strength.
Training for Endurance and Strength
From this understanding, we can therefore plan to strategize to fully maximize both endurance and strength. The two key aspects to consider – the timing of the exercise, and diet. Additional points to remember are:
1. Perform Endurance Training First and Strength Training Last
AMPK is switched off after exercise; however mTORC1 needs to be high for as long as possible for maximum effect – and AMPK turns off mTORC1. Therefore, if endurance exercise is performed first, then AMPK will be low later in the day (when the strength exercises are performed) and will not interfere with mTORC1. Training for strength at the end of the day will allow mTORC1 to be high for the rest of the evening and also while the athlete is sleeping. When the athlete wakes, they will have at least 12 hours with high mTORC1, promoting muscle growth and improved strength before their next session of endurance exercise turns on AMPK and turns off the strength signal.
2. Increase the Intensity to Your Endurance Training
AMPK responds to metabolic stress - the higher the intensity, the higher the metabolic stress and, therefore, the higher the AMPK activity. The best way to increase high intensity is to follow a long endurance session with some high-intensity intervals. The long, slow exercise depletes muscle glycogen and this makes the high-intensity work even more of a metabolic stress than if the high intensity is performed while the athlete is fresh, due to the fact that AMPK senses muscle glycogen levels. Severely depleting muscle glycogen before high-intensity exercise is optimal for activating AMPK hence optimizing muscle endurance.
3. Refuel After Resistance Training
During both endurance and strength training, diet is a very important aspect to take into account. Consuming a high-carbohydrate meal or snack an hour after endurance training will help to turn off AMPK and replenish muscle glycogen. Also, adding a protein- and carbohydrate-rich meal during the window of opportunity (about 45 minutes to one hour after strength training) will increase insulin and amino acids in the muscle, thereby improving muscle size and strength
4. Keep Resistance Training Short
Resistance training should not last longer than one hour. Keeping the training short and intense will keeps the metabolic stress of the exercise low, minimizing AMPK activity and therefore maximizing mTORC1
5. Emphasise Negative Reps
Muscle is around 1.8 times stronger when lengthening under load than when contracting. Muscle consumes much less ATP during lengthening contractions than it does during shortening contractions. This means that the body needs less ATP to lower a weight than to lift it. The result? More weight and less ATP is used, and this translates into more mTORC1 activity and henceforth stronger muscles.
Strength & Endurance Training
Before it was widely maintained that strength and endurance cannot both be maximised together – it has to either be one or the other. But with the advancement of research and technology over the years, together with the improvement of training methodologies, it has shown that improving both strength and endurance simultaneously can, in fact, be achieved. The trend has spread across to all facets in the field – sportsmen such has rugby players continually adopt new approaches to their training regimen, and we regularly witness how they are in peak condition- even more so than ever. It is also great to know that we as everyday gym goers can now also achieve great results by adopting the same concepts.
1. Eur J Applied Physiology. 2008 102: 145-52
2. Katch, V.L. Katch, F.I., Moffatt, R. Gittleson, M. (1980). Muscular development and lean body weight in body builders and weight lifters. Med Sci Sports Exerc, 12(5), 340-344