Alan Couzens, MS (Sports Science), CSCS, PES

One of the key physiological adaptations of endurance training for the Ironman athlete (and for the fitness athlete who wants to ‘lose a few pounds’ is improving their ability to generate energy from fat. I wanted to devote a short article to the ‘whys’ of the importance of improving this ability in athletes along with the practical ‘hows’ of doing so from both a training and a nutritional perspective.

In my last article on ‘Exercise Physiology 101: The Basics’, I outlined some of the key critical transitions that occur within the body when faced with an increasing exercise demand. In the name of practical applicability, coaches have used various methods to approximate these critical points and a variety of terms to describe the range that encompasses the transitions between these points.

The mixed use of terms like Zone 2, Compensation Training, Maximal Aerobic Function Training, Reps, Intervals, ½ Paced Efforts, Tempo Training etc etc. can leave 2 relatively intelligent coaches speaking 2 totally separate languages, the equivalent of Swahili and Japanese, if you will. To make things worse, the Swahili definition of ‘Tempo’ is completely different from the Japanese definition, so even those words that are common to both languages or systems can have definitions that are completely distinct and different. No wonder athletes get confused!!

In this article, I will present our own Endurance Corner terminology and will outline how it relates to the concepts outlined in the last exercise physiology article and also to the many and varied terms used by some of the more popular coaching systems.

Let’s begin by defining the terms that you’re likely to hear at Endurance Corner:

Easy Training (AeT-10 to AeT) – Improves your ability to generate energy from fat (especially for Novice athletes), enhances mitochondrial proliferation and capillary density (although less so than steady training). For the advanced athlete, enhances recovery between sessions.

Gordo has asked me to compile a couple of concise, core articles that will give our readers a background in the endurance exercise physiology behind some of the triathlon terminology that we use and the training philosophy that we espouse. Terms such as the aerobic threshold, the fat oxidation threshold, the lactate threshold and the anaerobic or functional threshold are regularly thrown around and unless you have a background in exercise physiology, they may leave your head spinning (even those of us with a background are not immune to the occasional head spin ☺)

So, this first article will present a brief review of those essential physiological concepts that have real, practical significance to you as an endurance athlete and the future direction of your training.

Let’s begin our ex phys 101 class with a brief review of one of the most important concepts, that of muscle fiber type.

Fiber Types

Just as the chicken has both dark meat and white meat, we humans also have muscles (meat) that is white, or dark in concert with it’s purpose. The ‘dark meat’ is made up, primarily, of slowtwitch fibers. Whereas the ‘white meat’ is made up of, more explosive, fast twitch fibers.

A good portion of our leg meat (for example the Soleus muscle of the lower leg) is predominantly ‘dark meat’, full of oxygen processing mitochondria (and the associated red pigmented cytochrome complexes) and myoglobin. Whereas, muscles responsible for more explosive movements, for example the ‘pushing’ muscles of the upper arm (triceps brachii) contain more fast twitch (white) fibers. In a very real sense, form dictates function.