Heart Rate Training Zone (cont.)
Maximum Heart Rate
HRmax is calculated by subtracting age from 220. The equation "220-age" yields an estimate only, since there is variability in maximum heart rates (see "Errors in Predicting Maximum Heart Rate" below). HRmax is biologically determined and declines as you age, and the correlation to age is strong; that is, if a large number of 20-75-year-old individuals walked on a treadmill to exhaustion to reach their HRmax, the distribution of heart rates would range from approximately 200 bpm (beats per minute) for the 20-year-olds down to 145 bpm for the 75-year-olds.
What Range Should I Train At?
Most people train within an aerobic exercise training zone (40% to 85% of HRmax). Aerobic capacity (endurance) will improve faster if you train closer to 85% than if you train at 65%, but some individuals don't have the capacity to start training at 85%, or they simply prefer to start training at lower values and gradually increase the intensity over the time. Some individuals may even need to start at levels as low as 40% or 50%, depending on their age, level of fitness, or body weight. But the level that you start at isn't all that relevant. What matters most is that you get started, and then over time, as your endurance improves, you can gradually increase the intensity.
The body accommodates to both low- and high-intensity workouts by increasing the activity of respiratory enzymes and other biochemical reactions in the muscles. Anaerobic training-like intervals and speed work are helpful if you want to improve your time or perform optimally in an event like a 10K run or a 50-mile bike ride because the training prepares your body for the specific anaerobic demands of the event (like when you have to sprint or climb a hill). This type of training, called "specificity of training," is effective because it mimics the type of exertion experienced during the event.
On the other hand, if health and general levels of fitness are the goal, and not performance in a road race, then there's no need to train anaerobically unless you like to push. Instead, substantial gains in health and fitness can be accrued by aerobic training between 40% and 85% of HRmax. Volumes of research prove this.
A traditional method of aerobic training is to start at the low end of the aerobic training range, say 50% or 60%, and as training continues and the heart and muscles adapt to the challenge, the intensity is progressively increased. For example, a sedentary individual might start at 60% of HRmax and remain at that level for four weeks, and then during the fifth week increase the intensity to 65% (increases of 10% of intensity and/or duration is the standard recommendation). Again, the body accommodates to the work over time, and when higher levels of fitness are desired, the intensity needs to be increased. Training heart rate zones offer a quantifiable method of guiding workouts and determining exercise intensity.