- Running at a "comfortably hard" effort where your heart rate is between 83 and 92 percent of its maximum
- Breathing is fast, but controlled
- Goal: to push your lactate, anaerobic and ventilatory thresholds to faster paces
- What happens physiologically as you adapt: your lactate threshold will be pushed to a higher pace—you can run faster for longer without suffering from lactic acid overload
- Running hard where your heart rate is 90 percent up to its maximum
- Breathing is labored
- Goal: to run faster and more efficiently for a longer period of time
- What happens physiologically as you adapt: lactic acid buffering capacity improves; greater stimulation of fast-twitch muscle fibers; greater ability to extract oxygen from the blood in the muscles; the enzymes that extract energy from your fuel sources increase
- Running very hard where your heart rate and VO2 max are at maximum capacity
- Breathing at full capacity
- Goal: to develop a powerful "kick" at the end of races, improve running economy, and make it easier for the body to tolerate speed and stamina training with less injury risk
- What happens physiologically as you adapt: improved neuromuscular function and lactic acid buffering; your body becomes efficient and coordinated at turning your legs over quickly
More: How to Run Fast: 3 FAQs
Step two: Once you know how quickly you adapt to workouts performed in the various training zones, you can learn how to tailor a training program to suit your individual needs.
Use your training log to see how you responded over time to workouts that fall into the four training zones—look for trends over several training cycles. If you see that you adapt quickly to stamina-type workouts, then you can deduce that you'll reach your peak fitness pretty quickly with just a few of those types of workouts. But, if you adapt more slowly to speed training, you'll need to schedule more of these types of workouts throughout the training cycle before you reach your peak in that zone.
"The workouts you generally like the most are the ones that you tend to adapt to the quickest," McMillan advises. "You know then that you don't need very may of those, and that you should put those workouts closer to your goal race. For others that you're slower to adapt to, you'll want to sprinkle more of those across the plan and typically earlier rather than later. That way, you can effectively time your peak."