Phase One

Aerobic Conditioning: 6 weeks – 6 months or more

Miles are Money in the Bank

This initial phase is the foundation of the training and will ultimately determine the quality of the subsequent phases and ultimately the outcome of your races. The less developed your aerobic capacity the more time you need to spend in this phase.

Aerobic conditioning must take place before you move on to the next phases since it provides the groundwork physiologically for you to be able to do the greater intensity of work required later. Without it, you risk illness, injury and poor performances. If we looked upon aerobic conditioning as a savings account, with every aerobic mile equaling a dollar, the bigger amount that we can save up the grander and more wonderful a spend we will be able to have on race day in order to buy a truly worthwhile performance.

Aerobic training conditions our bodies in the following essential ways:

Increases cardiac efficiency. Your heart will quickly respond by increasing in size, consequently able to pump more blood with each beat, and to pump faster when required. Your pulse rate will become stronger and slower when resting. Your lungs will become more efficient able to take in more air with each breath and to extract more oxygen out of that breath. As you rack up the miles so your peripheral blood system will respond by improving and developing new networks of roadways (arteries, capillaries, veins and arterioles) to feed oxygen to your tissues and remove waste products. Your entire body will become increasingly oxygenated giving you more energy and an overall sense of wellbeing.
Develops the efficiency of your fat-burning energy system to conserve your energy resources for the long haul. During slower aerobic metabolism your body derives a portion of its energy from slow-burning free fatty acids, which conserves some of the faster-burning carbohydrates. This way you don't suddenly run out of fuel after 2 hours or so as in the proverbial marathon "wall". As you increase the miles during the build-up at slower paces your body will become increasingly efficient at converting these fats to energy. Firstly you will notice that you are able to sustain longer and longer runs, quickly building up to your target distance. Then you should notice that with no extra effort you are able to do these runs faster.
Develops your aerobic muscle fibers. Your muscles are composed of aerobic (red) and anaerobic (white) muscle fibers. The aerobic fibers are used for endurance activity and are red in color because they house the iron-rich myoglobin within the cellular structures known as mitochondria. It is here that oxygen is converted to energy for your muscles to contract. As you activate these fibers through aerobic training you will develop more mitochondria and myoglobin thus increasing your ability to generate ATP, the chemical currency of movement.
Strengthens your muscular/skeletal system. Muscles, tendon and ligaments need time to strengthen so they can handle increasing workloads. Since they are slower to develop than the cardiovascular system it is common for runners to feel that they can extend themselves only to find that they are subsequently sidelined by a knee or achilles tendon, for example, that was not adequately conditioned for the stress put upon it. Aerobic conditioning prepares the body’s framework systematically and safely, allowing for all body systems to develop synergistically.
Trains your neurological pathways. With repetition the nervous system develops the motor pathways from your brain to your muscle fibers. As these are built upon and strengthened with continuous use you will increase in efficiency and a 'memory' of the activity is created.

Implementing Phase 1

The most important element of this phase is to keep your runs aerobic, where the oxygen that you are able to take in provides your energy needs without your physiology going into oxygen debt. If your runs are of an intensity that requires you go into anaerobic metabolism for more than a few minutes you can quickly defeat the purpose of this phase.

Four Aerobic Checks

Follow the pace guidelines. They are designed to keep you safely within your aerobic limits.
Check your Recovery Indicators daily.
Make sure you can always pass the "talk test". You should be able to engage in conversation easily. If you have to take pause to catch your breath between sentences then chances are you are running too hard. Make aerobic running a social activity. Team up with others your same pace and keep each other honest with some good conversation.
Pace Maintenance. Use an out and back course. Make sure that on the return journey you can maintain at least the pace you started with, or faster. If you have to slow down or feel pushed, you are running too fast.

If you consistently run too hard use a Heart Rate monitor to gauge yourself . You can estimate your Aerobic Threshold (AT) heart-rate with a simple formula: 220 minus your age 65% if you are a beginner, 75% for average runners, and 85% for highly trained athletes. Keep below that.

Guidelines for Aerobic Running

Once your AT Heart Rate is determined, beginning runners and those who tend to overdo it, may find it useful to wear a heart-rate monitor until you have locked in the feeling of where your threshold is. Once established the HR monitor is no longer needed. Do not go above your AT during your runs. As long as you stay within your aerobic zone your program will work for you.
As you progress you will be able to run a faster at the same effort (HR).
Vary your pace and distance from day to day within the ranges set by the schedule. Naturally you will have 'up' days where you run comfortably at your AT followed by 'down' days at a slower pace. Pay attention to your own rhythm and recovery rate.
Generally follow a harder (faster or longer) day with an easier (slower or shorter) one.
All paces count in developing your aerobic capacity as long as you do not get 'stuck' on one pace. Do not be afraid to jog your long run, or to incorporate walk on an easy aerobic day if you are a beginner. All aerobic activity is valid and will afford you all the benefits of strengthening your legs and building your circulatory roadways. There are no junk miles.
Resist timing your miles until you have built up to the minimum distance or time required. The competitor will be invoked later on.
If you are training for a marathon or are a beginning runner your main focus and time commitment will be on this phase of aerobic development.