How do you know when you have a workout that produces changes that allow you to do more the next time you workout, i.e., run farther or run faster? Understand that when you workout and get a positive training effect, you create changes in the body that allow you to perform even more or better the next time.
In order to achieve this training effect during the workout you must do more than what you did in the previous workout. This is known as the overload principle. It is in effect when you push the body to do more than previously to elicit more changes that allow you to do more or better in future workouts.
Not all workouts produce a training effect. Merely working up a good sweat in your run or being sore the next day is not indicative of a workout that produced beneficial effects. For example, if you experience soreness on the next day it means that you did too much and actually did damage to your body. This in turn will set you back in training, instead of improving you to do better.
To guide you in aerobic training that produces a training effect, use your heart rate (HR). For example, you must have your heart rate sufficiently high during your run to produce beneficial results. For runners who are in their late teens and 20s this is approximately 150 beats per minute (bpm). If you get up to about 180 beats per minute then you are running in the anaerobic range in which you do not directly use the oxygen that you take in with your breathing for more energy. At this time you use the energy stores in the muscles. This is why you cannot last very long at such high speeds.
If you keep your HR between 140 and 160 bpm, you receive the aerobic effect. If you only get the HR up to about 120 bpm you will help the recovery processes which is good the day after very long or intense runs. It will not, however, produce an aerobic effect.
The common formula used to determine the HR zone is 220 minus your age, multiplied by 60 and 80% to determine the lower and upper target heart zone limits. This is a general formula and does not apply to all runners, especially high-level runners. Also, most often you have to determine where the break-off point is between running aerobically and anaerobically. This is known as the anaerobic threshold.
For example, for success in long distance running races, the key is to run as fast as possible as close as possible to the anaerobic threshold without going into the anaerobic range. This range should be saved for the end of the race at which time you should deplete all of the stored energy to finish in a fatigued state.
The faster you run keep the HR as high as possible, but without going into the anaerobic range. This is the key to success in running long distances. When you run at this rate you utilize fat as the primary source for energy.When fat breaks down it releases approximately twice the amount of energy that the breakdown of carbohydrate does.
The more you can use fats as the primary energy source, the more efficient your running becomes. However, the ability to burn fat at this level must be learned and developed over time.You must determine how fast and how long you must go to get this effect. Keep in mind that slow running also utilizes fat as the energy source. But it is not as effective as running as fast as you can while still utilizing fat stores as the primary source.