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A question from a very intelligent and motivated reader:

“…we started using the advice in your book as far as meals and exercising.  The first 4 or 5 days I couldn’t do more than 2 mph on the treadmill (30 min. miles).  After the 6th day I could do 3mph (20 min. miles) without a problem.  Exactly what happens to the cardio-vascular system to cause this?  Granted, I’m not quite ready for the Door County Triathlon, but I’m heading in the right direction. Weight 10 days ago, [censored] {6 pound loss}; height is still the same.”

Source material for the below is Exercise Physiology, Sixth Edition; McArdle Katch, and Katch.

It is absolutely amazing, the capacities our bodies have to adapt. One of the quickest adaptations is in the metabolic machinery in the cell—within 5-10 days of training there is an increased mitochondrial capacity to generate ATP aerobically (ATP is the energy currency of our bodies–it is to the human body as gas is to a car). The enzyme changes result from increases in total mitochondria, which are those little things in the cellular cytoplasm that look like little ovals with a “maze” inside of them. With this change, a person has an increased aerobic capacity within a number of days of starting a training program.

Another fairly immediate change is in the plasma volume (the fluid that comprises the vascular volume within which are all the red blood cells, white blood cells, and lots of other stuff)—after 3-6 aerobic sessions there is a 12-20% increase in the plasma volume; in fact, there is a measurable change within 24 hours of the first exercise episode. This effect enhances the stroke volume and oxygen transport during exercise. Unfortunately, the expanded plasma volume returns to normal levels after one week of no exercise.

The most significant adaptation in cardiovascular function with aerobic training is an increase in the cardiac output, which is the amount of blood that the heart can pump throughout your body, measured in liters/minute (Max Cardiac Output for Sedentary Adult is 20.0 L/min: for Athlete it is 30.4 L/min). Aerobic training also increases the amount of oxygen that can be extracted from the circulating blood. This is because there is an improved cardiac output distribution to the active muscles, and those muscles becoming better at extracting and processing the available oxygen.

There are many other benefits, both immediate and long term. For instance, after two years there is nearly a 50% increase in the capillaries (tiny blood vessels) in the muscles, which allows for more oxygen delivery to the tissues (20% after 2 mo.). In my book I discuss at length the underappreciated benefits of exercise; increase in metabolic rate, anti-depressant effect, and anti-inflammatory effect.

You would think that if more people knew of this, there’d be a lot more exercising going on. The truth is, most of our health ills today are largely self inflicted; smoking, drinking excessively, and obesity. If folks would not smoke, drink in moderation, maintain an appropriate caloric intake and exercise regularly, there would be much less of a need for doctors.

Ssshhh…don’t tell anybody–I still have to put beer in my cooler.