Concurrent training can be explained simply as resistance training while also training aerobic qualities. This is relevant because most field-based sports rely heavily upon both qualities- Can you produce force? Can you last all four quarters? Also, there are some other interesting implications for aesthetics and the competitive bodybuilders. This article does a great job laying out evidence-based recommendations from a molecular biology standpoint.
Strength and endurance training have inherently opposing agendas. We can observe this power-struggle when we consider a few key compounds:
AMPK (adenosine monophosphate-activated protein kinase) is stimulated during aerobic training. This compound is involved in the increase in fat oxidation during exercise and long-term regulation of mitochondria.
SIRT1 (NAD+-dependent deacetylase family of sirtuins) works similarly to AMPK, SIRT1 is activated by metabolic stress; seen from increases in lactate and NAD+. SIRT1 plays a role in metabolic function, insulin sensitivity, and mitochondrial regulation.
mTOR (mammalian target of rapamycin) is the key signaling molecule for skeletal muscle hypertrophy. Following resistance exercise, there is a sustained increase in mTOR activity which drives exercise-induced muscle protein synthesis.
Our objective is achieved by increasing the mitochondrial adaption from an endurance standpoint, while also increasing muscle mass and force production from a strength standpoint. This is the battle between AMPK/SIRT1 and mTOR (plus numerous other compounds). This can be maximized with the following recommendations.
Science-Based Recommendations for Training to Maximize Concurrent Training:
- Any high-intensity endurance training sessions should be performed early in the day.
Then, a period of recovery of at least 3 hours should be given, so that AMPK and SIRT1 activity can return to baseline levels, before resistance exercise is performed. This suggestion is based on the fact that AMPK activity increases rapidly and then returns to baseline levels within the first 3 hours after high-intensity exercise, whereas mTORC1 activity can be maintained for at least 18 hours after resistance exercise.
- Resistance exercise should be supported by readily digestible, leucine-rich protein as soon as possible after training to maximize leucine uptake, mTOR recruitment to the lysosome, and protein synthesis.
Since, in this scenario, resistance exercise is performed later in the day, it becomes even more important to also consume protein immediately prior to sleep to maximize the synthetic response overnight.
- Fully refuel between the morning high-intensity endurance training session and the afternoon strength session since AMPK can be activated by low glycogen, and SIRT1 is activated by caloric restriction.
If it is not possible to refuel completely because of the training volume and intensity, it might be best to reserve a portion of the off-season (and short periods in season) exclusively for increasing muscle size and strength and then use higher dietary protein intakes to maintain that muscle mass as the aerobic load increases through the season.
- To improve the endurance response to lower-intensity endurance training sessions and provide a strong strength stimulus, consider performing strength training immediately after low-intensity, non-depleting, endurance sessions.
Performing a strength session immediately after a low-intensity endurance session results in a greater stimulus for endurance adaptation than the low-intensity endurance session alone and the low-intensity session will not affect signaling pathways regulating strength gain.
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