Warning: Endurance training, when pursued even at a seemingly sensible level, can be unhealthy and depleting to your body, mind and spirit. Fitness and supplement guru Mark Sisson argues that endurance training is counter to our basic caveman physiology. This is where we are programmed to produce shorts bursts of life or death energy to avoid a predator or feed our families with a kill, which is balanced by the downtime of a simple, hunter/gatherer primitive life. It's clear that endurance training causes a steady reduction in testosterone levels, along with a corresponding increase in levels of the stress hormone cortisol.
High cortisol (low testosterone) causes a very distressing chain reaction of negative events. The immune system is suppressed and the body stays in a catabolic state. Taken to the extreme in the classic over-training state (which seems commonplace among triathletes and distance runners of all ability levels), an athlete's muscle will literally waste away. This is identical to the "dying of old age" scenario, Sisson explains.
Sisson, inspired by a lifelong fascination with evolutionary biology, argues that you should align your dietary choices and training methods with the nature of human lifestyle over the course of thousands of years. Eat healthy, natural whole foods; conduct regular sustained exercise at moderate heart rates (the Gatherer); and, once in a while, conduct extremely intense, short duration workouts to get and stay fit (the Hunter).
Sisson, my coach during my professional career and a former 2:18 marathoner and fourth place Hawaii Ironman triathlete, and I have experienced outstanding results from turning our backs on the "mileage/consistency" endurance cornerstones in favor of a more varied routine that eliminates excessive duration workouts and features the occasional very intense "caveman" session. I feel healthier today than I have been since I was 13.
"I believe that training for more than an hour a day destroys your immune system and the more hours you train, the worse it gets," Sisson reports.
This kind of talk may not sit well if you are currently pondering a season with marathons or long-distance triathlons. It's obvious that the way to succeed in endurance sports is to approximate the challenge of your race in your training. However, the old-school philosophy of racking up weeks upon weeks of consistent mileage is inferior to pursuing competitive goals--even extreme endurance goals--with a balance of stress, rest and a constant respect for your health. Your schedule should be centered on the occasional key workout, that approximates your competitive goals and is difficult and challenging enough to stimulate a fitness improvement.
Feel free to experiment with your training methods so that they align with your lifestyle, intuition and caveman physiology, built for occasional heavy stress balanced by down time. Understand that an obsessive-compulsive tendency to accumulate measurable results day in and day out sabotages your ultimate athletic potential and compromises your health. If you feel like resting or backing away from ambitious training plans, give yourself the freedom to do so. Try pushing yourself really hard once in a while to stimulate breakthroughs in fitness, body composition, general health and well being.