The Motor Unit Biweekly

This is a follow-up newsletter article to my previous one on “Does cardio kill your gains?”. To briefly review it, the best way to prevent your cardio training from interfering with your strength gains is to have it as a separate session with training, ideally, focused on keeping your heart rate at Zone 2 for at least 30 minutes 2 to 3 times a week.

This one is on how and why Zone 2 training (typically called cardio) can help you make better gains in strength, muscular endurance, recovery, and overall work capacity. There’s a bit of biology here that we need to understand first and I’ll try to keep it simple. Your circulatory system consists of veins and arteries with a heart in between. For the most part, when your heart pumps out blood your arteries deliver blood carrying oxygen and nutrients to your muscles and organs and then, your veins take away blood carrying carbon dioxide and wastes formed from physical exertion and from processing nutrients. Once the blood is cleared of the wastes, it’s refilled with oxygen and nutrients and pumped from the heart to help you continue training or go about doing your daily activities.

When these arteries deliver oxygenated blood carrying nutrients, they deliver it through capillaries. Think of these capillaries as a network of roads or pipelines. The more roads or pipelines you’ve got, the more traffic you’ve got coming in and out.

So, when you include Zone 2 training, your body adapts by increasing the number of capillaries that deliver this oxygenated blood with nutrients to your muscles and organs. These nutrients get converted to fuel that your body needs in the presence of oxygen. You also increase the number of pathways through which deoxygenated blood with metabolic waste is carried away. These metabolic wastes have an acidic component to them that feels like localized or full-body burn when you do intense exercise and it can prevent you from pushing further.

When there are more capillaries to shuttle away these acidic byproducts and bring in fuel, you essentially buffer your muscles against this acidic burn and increase your work capacity and recovery between bouts of high intensity bursts of energy (think sprinting or throwing a flurry of punches and kicks as a combat athlete or HIIT training with weights or just traditional weight training). With the right programming, you can incorporate Zone 2 training both within a highly intense workout session as a method of active recovery and as an overarching mechanism to help you improve your work capacity, as mentioned above.

Here’s three other effects that I think need to be bought in here -

• It increases your cardiac output. Cardiac output is the volume of oxygenated blood pumped out (stroke volume) per heartbeat. Zone 2 training adapts the heart ventricle that pumps out oxygenated blood to stretch out and fill up a bit more over time to pump out more blood. This adapts your heart to beat fewer times to get the blood flowing towards your extremities through stronger contractions with higher blood volume. The bottom line is that your heart simply gets stronger and works better.

• Your body’s oxygen uptake increases. Oxygen uptake is your body’s ability to take oxygen, deliver it to your muscles, organs, and other tissues, and the subsequent ability of said muscles, organs, and tissues to make use of it. The better your oxygen uptake, the better your cardiovascular fitness and chances of living longer. It is such an important variable that maximal oxygen uptake is used both in athletics and the health industry as a measure of both athletic fitness and as a major indicator of health.

• Your aerobic energy system is one of three energy systems that run your body depending on the intensity and duration of physical demands placed on you (more on training the other two systems in upcoming newsletters). Training this system through Zone 2 primarily relies on producing energy through the mitochondria by using your body’s fat reserves over a long period (think on the durations of several minutes to a day). With this comes the adaptation of increasing your body’s mitochondria count, which also boosts the recovery aspect discussed earlier, and the added benefit of using up excess fat stores hindering any weight loss goals you may have provided there’s a caloric deficit in your food intake.

Now, I know that this Zone 2 training is not all that sexy, especially when you do it with the likes of steady-state jogging, but you can’t argue with the benefits above. Having said that, I’ve gone into how you could spice up Zone 2 training in my previous newsletter and you can go through it here if you’re interested.

Until next time!

References:

Strasser B, Burtscher M. Survival of the fittest: VO₂max, a key predictor of longevity? Front Biosci (Landmark Ed). 2018 Mar 1;23(8):1505-1516. doi: 10.2741/4657. PMID: 29293447.

Jamieson, J. (2009). Ultimate MMA Conditioning. Performance Sports Incorporated.