Notice the range of heart rate percentages in the table rather than a set heart rate value for each type of workout. The reason for this is two-fold. First, not all runners will have the same heart rate at a given intensity due to differences in lactate threshold and economy, and second, when running interval workouts, heart rate will drift upward as the number of repetitions increases.
More: How to Burn Calories Fast With Interval Training Workouts
For example, if you run 6 x 800 meters in 2:30, your heart rate can be expected to be somewhat higher during the latter repetitions compared to the earlier repetitions due to the accumulated stress of the workout. The heart rate profile for the workout may look like this: 181, 181, 183, 184, 186, and 188 beats per minute. As you fatigue, the heart must compensate by beating faster to pump enough oxygen to the working muscles.
The heart rate profile during the workout can help you determine when fitness gains have taken place. For example, say you run the same workout—6 x 800 meters—two months later, and the heart rate profile looks like this: 179, 179, 180, 180, 182, and 183 beats per minute. All else being equal (temperature, wind conditions, fatigue level), you could say that you have improved your fitness.
Using the information in the above table, a sample training week during the early competitive phase for a 5K runner could look like this:
Monday
-2 miles warm-up at 70 to 75 percent max HR
-5 x 1,000 meters at 95 to 100 percent max HR with equal time jog recovery
-2-mile cooldown at 70 to 75 percent max HR
Tuesday
-8 miles at 70 to 75 percent max HR
Wednesday
-2 miles warm-up at 70 to 75 percent max HR
-3-mile lactate threshold run at 85 to 90 percent max HR
-2-mile cooldown at 70 to 75 percent max HR
Thursday
-5 miles at 70 to 75 percent max HR
Friday
-Rest
Saturday
-Race
Sunday
-10 miles at 70 to 75 percent max HR
More: How You Can Create Your Own Training Plan
How Environment Affects Heart Rate
Where you run greatly affects your heart rate response to training. For example, running in the heat increases heart rate in order to improve evaporative heat loss from the body while running in the cold decreases heart rate in order to keep the heat in. Thus, running in the winter at 7:00 mile pace may elicit a HR of 130 beats per minute, while running at that same pace in the summer may elicit a HR of 140 beats per minute even if you are in better physical condition during the summer.
More: What Is Cardiac Drift and How It Affects Runners
The hotter the body gets in the heat, the more the heart rate will increase in an attempt to maintain core body temperature at a safe level. Therefore, when running for long periods of time in the heat, heart rate will drift upward as the run continues. When acclimatized to the heat, however, training runs can be performed for longer periods of time before the heart rate changes to the extent observed before acclimatization.
Running at altitude also presents an environmental stress to the distance runner, increasing your heart rate. The higher the altitude, the less oxygen you have available to the muscle cells. The heart has to beat more often to supply oxygen to the muscles.
More: The Effects of High Altitude Training
Once you are acclimatized to the higher elevation, changes in heart rate will diminish compared to that observed before acclimatization, although it may never completely return to sea-level values while at altitude. This acclimatization-induced drop in heart rate at a given intensity at altitude can thus be used as a time marker for acclimatization, and can signal when you have gained the benefit of altitude training and when it is appropriate to return to sea-level for competition.
More: 3 Key Running Techniques to Improve Your Race Performance
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