One of the main principles of exercise is this: break your muscles down so that they can build up stronger.

As mentioned in our guide on How To Build Muscle

Your muscles require beyond their usual level of performance in order to break down and then grow, during a workout, micro-cracks form in strained muscles. To break this down further, not only your muscles are affected by the way you train but also your autonomic nervous system which is responsible for your cardiovascular health, your blood pressure as well as your heart rate variability which can also highlight how fit you are.

In a crossover trial researchers compared two exercise protocols performed by 10 physically fit men:

1.) 20 minutes of a high-intensity CrossFit workout


2.) 20 minutes of treadmill running, each performed at the same intensity.

The effects on the subjects nervous systems were taken before and after each with rest days of 3 – 7 days between each testing. Trainin

The results?

The high-intensity training method used was the CrossFit workout “Cindy,” and the treadmill trial was performed at a minimum of 85% maximal heart rate.

ECG and blood draws were performed before and after the exercise bouts.

Although the intensities of the two trials were similar, the high-intensity CrossFit exercise had a greater effect the 10 individual’s nervous systems as opposed to the treadmill running.

Immediately after exercise, the high-intensity trial caused a 2 times greater response in heart rate variability meaning it took way more out of the body. This means greater results. The crazy thing is that despite the greater physiological strain, the high-intensity exercise recovery closely followed that of the treadmill running. Translating into a fitter, healthier you in far less time.