Is Cardio Good For You? (Part 1: It Helps Rats…) by Joan Kent, PhD

Is Cardio Good For You? (Part 1: It Helps Rats…)
By Joan Kent, PhD

A friend recently forwarded a 2/17/16 NY Times article on how different exercise types affect the brain.

The report was on one study only – on rats – and showed that the neurological benefits of treadmill running outpaced the benefits of resistance work, high-intensity sprinting intervals, or no activity (in sedentary controls).

Brain benefits included the generation of new cells, mainly in the hippocampus. The number of new brain cells was directly related to the distance the rats ran – more distance yielded more new neurons.

So WIIFM: What’s In It For Me?

Assuming the rat brain benefits are eventually shown to benefit humans, let’s look at known physiological benefits of aerobic/endurance/cardio training. We’ll delve into other exercise types next time.

Here’s a list of cardio adaptations that Jim Karanas and I put together a few years ago.

Bigger Tidal Volume
Aerobic conditioning moves more oxygen to the working muscles. The first adaptation is breathing capacity, called tidal volume. The air volume the lungs can move with each breath increases with improved diaphragm strength and breathing technique. Higher tidal volume is also associated with longevity.

Bigger Blood Volume
Blood increases with cardiovascular training. The body produces more red blood cells and blood to increase oxygen-carrying capacity to body tissues. Increased blood volume also improves metabolic waste removal and recovery.

Bigger Stroke Volume
The volume of blood ejected by the heart per beat increases, indicating improved heart function. This adaptation tends to occur at heart rates below 160 bpm. When people talk about “strengthening” the heart, this comes closest to being the underlying mechanism. In pumping more blood per beat, the heart moves a greater workload. The strength-training equivalent would be lifting a heavier weight with slow repetitions, versus pumping light weights quickly.

More Capillaries*
Capillaries are blood vessels with walls one cell thick. They surround muscle cells and deliver oxygen and nutrients. The capillary network becomes denser with aerobic conditioning. This results in greater surface area for transferring oxygen to the mitochondria in the muscle cell.

Size Matters (Density Too)*
Aerobic training increases the size and density of mitochondria. Mitochondria are structures in muscle cells that convert fuel to energy aerobically. They’re the receptor sites for the molecular oxygen that powers the Krebs (or citric acid) cycle and produces ATP. Mitochondria are the only sites in the body that burn fat – except for the heart, which uses whatever it gets, including lactate.

More Type 1 Muscle Fibers*
Aerobic conditioning sensitizes working muscle to insulin, partly by promoting Type 1 fibers. Type 1 fibers are high-endurance and responsive to insulin. (Type 2b are better for explosive power but less sensitive to insulin.) Everyone knows that cardio training can reduce the risk of heart disease, hypertension, stroke, diabetes, cholesterol problems, and more. Insulin sensitivity is significant because insulin resistance underlies those conditions.

More Fat-Burning Enzymes
Hormone-sensitive lipase (HSL) moves fat from storage to bloodstream for utilization. HSL is activated by brain chemicals and hormones when the body needs to mobilize energy stores. It’s inhibited by insulin.

Adaptations marked * are peripheral, specific to the working muscle. So upper-body cardio, such as Kranking®, will increase mitochondria, capillaries and type-1 fibers in the upper body, just as lower-body training affects the lower-body muscles.

Adaptations without * are central and impact the entire body. Central adaptations permit a transfer. So upper body aerobic training (like Kranking®) can improve lower-body aerobic performance.

What About Weight Loss and Aerobic Training?

Aerobic adaptations improve the body’s ability to move oxygen and burn fuel. Aerobic exercise has limited impact on weight loss, partly because of its low intensity and low calorie expenditure. That’s why high-intensity training is also necessary. Besides, training is about much more than weight loss.

A major benefit of aerobic conditioning is that it supports recovery from intense training. Trainers who advocate only high-intensity work often miss this point.

Regardless, when it comes to the sheer pleasure of training, indoors or out, a well-developed aerobic system lets you feel fantastic.

(Part 2 will cover the high- and low-intensity debate and some cool stuff about running.)