Chronic Cardio = Low Testosterone

Long-distance endurance training produces an abundant amount of cortisol, which makes us prone to fat storage, muscle loss, and the degeneration that comes with it. One of the reasons it burns up muscle is because cortisol competes with testosterone – when one is secreted, the other is inhibited.

Cortisol is catabolic (muscle death), and testosterone is anabolic (muscle birth).

A more favorable testosterone to cortisol ratio (T:C) promotes muscle growth and tissue repair, while a higher proportion of cortisol promotes muscle and tissue loss.  And since cortisol increases steadily throughout a workout and testosterone peaks at 20-30min, the longer an exercise bout the more unfavorable the T:C ratio.

Whereas, shorter and more intense the workout, the higher the testosterone and lower the cortisol.


No offence to the ladies, but this is usually the part where one stands up and says she’d rather stick to cardio because she doesn’t want more testosterone and big bulky muscles.  As despite the negatives we already discussed regarding cortisol, and the pure and simple fact that cortisol is harder on women, many of them hear ‘testosterone’ and assume it means they’ll turn into a big muscular man.

“I just want to get toned.” is usually the response. 

When realistically, women do not have the natural testosterone levels to put on slabs of muscle without pharmaceutical assistance, and ‘legal’ training will only bring anabolic effects (tissue building), not androgenic effects (masculine characteristics).

Males, have as much as 8 times the blood concentration and 20 times the daily production of testosterone.

But more importantly, “getting toned” requires a combination of muscle building and fat removal – exactly the opposite of what aerobic training produces.

runner vs. athlete

“Which toned body was it you had in mind?”

Your nutrition, training, and lifestyle plan should focus on facilitating a favorable Testosterone-to-Cortisol ratio to support muscle growth and maintenance. This translates to a higher metabolic rate, lower fat storage rate, and decreased risk of degenerative disease (like osteoporosis) and mortality.

When it comes to exercise, this means keeping your workouts short and intense, and focusing on building instead of burning.

Stay Lean!
Coach Mike