I returned to actual endurance training in early 2015 to prepare for professional Speedgolf competition, after ~20 years of fooling around. I limited my heart rate to 145 bpm or below for my training runs, but it was still too high for an old guy and I spiraled into an overtraining condition by May of 2015. I blame this ill advised chronic exercise stint for an alarming health setback that occurred in June of 2015. On the heels of two high intensity sprint workouts over a span of five days, in 100-degree summer heat, I sustained appendicitis and had to have emergency surgery for a ruptured appendix. Complications followed that required three exploratory surgeries on my kidneys for unexplained and sustained hematuria–blood in the urine. I was a mess, man!!!

After a very patient return to physical exercise and eventual resumption of light jogging, I decided to pinpoint my aerobic training heart rate based on the Maffetone formula instead of using the higher limits I’d followed in the first half of the year. Dr. Phil Maffetone, author of the Big Book of Endurance Training and Racing and legendary endurance coach, suggested that his MAF formula for determining the all-important maximum aerobic heart rate would deliver a more accurate value than calculating a percentage of maximum heart rate–especially for me because I have a higher than predicted max heart rate for a 50-year-old due to my athletic background.

Maffetone formula is 180-age, so I started running at 130 bpm. This is extremely slow and pretty frustrating to have to slow to a walk during an already slow run, or walk up hills instead of jog. After months of devoted effort and limiting heart rate however, my energy and general health improved greatly, as did my fitness. I filmed this video because I was particularly pleased to notice running along at a decent pace with a heart rate of only 123!

Many endurance athletes have trouble slowing down the pace of their workouts, especially to the extremely low intensity that 180-age dictates. In my case, the benefits of my aerobic base building have been validated not only by steady improvement on the trails, but in my blood values.

In April, in the midst of my chronic training patterns, my all-important testosterone values were 686 serum and 6.8 free-testosterone. 6.8 drew a low flag as clinically hypotestosteronemia! Not cool! In October, my values were 1,013 serum and 14.7 free-testosterone. For reference, during my professional triathlon career I ranged from 200-300 on serum testosterone. Even during my supposed peak hormonal years of my 20s, the extreme training and transcontinental travel suppressed my testosterone and in turn elevated stress hormones like cortisol that antagonize testosterone. Delivering a ~1,000 serum level is at the top end of the range even for a young man. Now, it’s essential to also test for free testosterone, for this is the bioavailable form that is circulating and acting upon target organs to deliver the desired beneficial effects. In some cases, a subject can deliver a high reading for serum testosterone, but have inferior free testosterone due to elevated levels of sex hormone-binding globulin (SHBG.) This agent binds with most of your serum testosterone, leaving only a small fraction of free T to go to work and activate cell receptors in target organs. For example, women have twice the level of SHBG as men, ensuring they are not over-exposed to testosterone.

Bottom line: SLOWING DOWN will help you improve as an endurance athlete. It will help protect against overtraining and burnout, and it will optimize your hormones so you experience an anti-aging effect instead of accelerated aging that comes from chronic cardio training. When you integrate brief, high-intensity resistance training and sprinting, you can experience the opposite effect of chronic exercise: a spike in testosterone and human growth hormone in response to the appropriate–hormetic–stress of properly conducted high intensity workouts. These topics are some of the central elements of the Primal Endurance training philosophy.

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