I started running again last Monday.. 2 miles very easy, then 3 on Tuesday and 5 on Wednesday. Rest on Thursday and 5 on Friday and today... I've decided to try and adopt the philosophy of running at MAF for my base building period. MAF stands for Maximum Aerobic Function. Your MAF is a measurement of heart rate and is determined as follows:
1. Take 180 and subtract your age.
2. Take that number and correct it by the amount next to the statement that best describes your level of fitness:
a. Subtract five beats if you are recovering from a major illness or injury that has kept you from training for six months or more.
b. Leave the number where it is if you have been working out about two to three days per week for at least a year.
c. Add five beats if you have been working out more than three days per week for at least a year.
d. Add 10 beats if you have been working out more than five days per week for at least five years without recurring colds, illnesses, injuries or long periods of burnout.
e. If you are older than 55 years old or younger than 25 years old, add an additional five beats to whatever number you have right now.
If you go over your maximum aerobic heart rate you switch off your aerobic development (your fat-burning metabolism) and turn on anaerobic metabolism, which uses your stored, and limited supply, of carbohydrates. During base training this is not a good thing to do consistently.
First, once you turn off your fat-burning system it stays shut off for seven to nine hours, even after your heart rate has dropped back down to resting. If you do this consistently you will limit your ability to efficiently burn fat as your primary fuel.
Second, going over your aerobic maximum heart rate causes you to turn on your adrenal system. This is the system that enables people to deal with stress. A little stress is good because it strengthens your entire body and helps your whole system function better. However, if you turn on your adrenal system consistently—which is what happens when you go over your maximum aerobic heart rate—you end up reducing your ability to respond to stress; you build up fat in your cardiovascular system; you reduce the output of DHEA, which is the hormone that enables you to look at life as a good thing; you can become depressed and lose motivation (not a good thing for being consistent with workouts); you can become unable to sleep deeply in the way that is needed to recover your body; and ultimately you will end up not having the reserve necessary when it comes time to race. In other words, you will get burned out and actually lose fitness with regular anaerobic high heart rate training over time. There is a time for the speed work, but the base period is not that time.
Thanks to Tim Luchinske for all the MAF information from above...
So far everything is going great and I've realized one thing. My aerobic engine is pretty weak right now.. Running at a max HR of 146 (which is my MAF), my average pace for the 2 mile run I ran last Monday was 9:11/m at an AHR of 143 bpm.. OUCH! It's dropping with every run, but it just tells me that I need a lot more base training before I can think about starting up speed work again. My 5 mile run today was done at the same AHR of 143, but my pace was 8:50/m so I've dropped over 20s per mile in less than a week. Still, it's quite a change of pace (no pun intended) from someone who's use to running ~6:30 - 6:50 for a training run's. I'm certain it won't keep dropping at that rate, but it's a start and I plan to keep with it through Boston in April 09'.