What's The Signal?

If you partake in any type of fitness venture that requires you to go down the endless hole of “how should I train for the best results for my given goals,” then you’ve most likely come across the argument surrounding when you should perform cardio work and strength training.

Well, I’m here to clear up parts of it. Because, to be completely honest, it’s still an ongoing debate between the experienced folks and the science nerds.

Okay, so let’s briefly touch on the two main training buckets responsible for producing ATP and the signals for adaptions. I promise not to overly bore you with a ton of science gibberish, just enough to make sure we’re all on the same page.

-Aerobic respiration uses oxygen and is the dominant system during low-to-moderate intensity, sustained activity; physical activity as in jogging, cycling, daily movement.
It's efficient, and will produce roughly 30-32 ATP per glucose molecule. Primarily running through glycolysis to the Krebs cycle, and then to oxidative phosphorylation.

-Anaerobic respiration doesn't use oxygen and will kick in during high-intensity, short-duration efforts; we’re talking sprinting, heavy lifting, explosive movements.
It's much faster… but inefficient. It will produce about 2-4 ATP per glucose, and generates lactate as a byproduct.

AMPK (AMP-activated protein kinase)

This is your body's energy-sensing rescue switch. When ATP is being burned faster than it's being made (during intense exercise, fasting, or low oxygen) the AMP:ATP ratio rises, which activates AMPK (via kinases: an enzyme that adds phosphate groups to other molecules, such as proteins or sugars, in a process called phosphorylation. This acts as a molecular "on/off" switch, regulating almost all cellular processes including metabolism, cell growth, and division). AMPK then triggers fat oxidation, increases glucose uptake into muscles (even without insulin), and stimulates mitochondrial bio-genesis (creating more). It also shuts down mTOR to prevent energy-expensive anabolic processes. Think of AMPK as the signal that says "energy is low, conserve and adapt."

mTOR (mechanistic target of rapamycin)

This is your body's growth and building signal. When energy is abundant, you’re well fed, rested, and insulin is elevated, the mTOR complex 1 gets switched on.
It then begins phosphorylation of key proteins that kick off protein synthesis, muscle hypertrophy, and cell growth. It also suppresses AMPK and autophagy (cellular "self-cleaning"). Think of mTOR as the signal that says "we have resources, build something."

Let’s answer the real question here… When should you train these systems if you want the best of both? Well, to be quite frank with you, there is no real straightforward answer.

Right now, the most popular protocols are that if you want to focus solely on muscle size and strength, typically the bulk of training focus should be on resistance training, with lower amounts of “fat-burning” type cardio. Whereas for a heavy endurance focus, it should be vice versa.

When it comes to performance, most of the time a combination of speed and distance conditioning should be implemented with a balance of strength and power work from resistance training and plyometrics. The most optimal timing methods will always point to the two systems being trained at separate times during mesocycles focused on full adaptation in all areas. However, when working for capacity or maintaining it, performing your conditioning and plyometric work first, and then your strength/power work second, may be the better protocol.

Keeping in mind that this is all dependent on what is required for your given sport and training population.

MINDSET

At the end of the day, it’s about getting better at the chosen sport of fitness venture you enjoy doing. Build your training around becoming better at that. Structure your mesocycles for building, then for peaking or maintaining, and finally for competition.

Train smart, but never forget to train hard.