Zone 2 training: finding the heart rate that builds endurance

What a zone is, and why there are several systems

Training zones divide the range between rest and maximum effort into bands, so that an intensity can be prescribed and repeated. The difficulty is that there is no single standard. Some systems use five zones of maximum heart rate, others use heart rate reserve, others lactate or ventilatory thresholds measured in a laboratory. A "zone 2" on one watch is not the same as on another.

What all the systems agree on is the sensation. Zone 2 is the highest intensity at which you can still breathe through a conversation. Above it, sentences shorten. In a laboratory it corresponds roughly to the effort just below the first lactate threshold, where the body still clears lactate as fast as it produces it.

Calculating your own range

Two numbers are needed.

1. Your resting heart rate. Measure it on waking, lying down, on three mornings, and take the average. See resting heart rate.
2. Your maximum heart rate. The old formula of 220 minus age is still printed on gym machines. A study of more than 18,000 subjects by Tanaka and colleagues found that 208 minus 0.7 times age predicts it better in adults, particularly past 40, where the old formula underestimates.

The Karvonen method then works on the reserve, the difference between the two, because it adjusts for fitness: a low resting pulse shifts the whole range. The calculator above applies it.

An estimated maximum can be off by ten beats in either direction for an individual. Treat the result as a starting point and check it against the talk test. If you cannot finish a sentence at the top of your calculated range, lower it by five beats.

Why this intensity matters

Most adults who exercise train in a narrow middle band: too hard to be easy, too easy to be hard. The sessions feel productive and leave them tired, without building either end.

Steady work at moderate intensity does three things well.

• It can be repeated. You recover from a zone 2 session within hours, so it can be done the day after a hard one, or after a short night.
• It accumulates. The health benefit of aerobic activity depends on the weekly total, and this is the intensity at which a large total is sustainable.
• It supports the hard work. Intervals raise the ceiling; steady work raises the floor. Endurance athletes do the large majority of their training at low intensity for this reason, though the exact proportion that suits a person who trains four hours a week has not been established by trials.

Claims that zone 2 alone is the best training for longevity go beyond the evidence. What studies show is that higher cardiorespiratory fitness is associated with lower mortality, and that both moderate and vigorous activity raise it. See VO2 max and short, hard workouts.

How much, and in what form

Two to three sessions of 40 to 60 minutes a week is a solid base for someone who also does strength work. Any rhythmic activity serves: cycling, rowing, swimming, an incline walk, an easy run.

The choice depends on what keeps your heart rate steady without strain on the joints.

• Indoor cycling is the easiest to hold at a fixed rate and the simplest to combine with a call you only need to listen to.
• Incline walking suits heavier or older beginners, for whom running pushes the pulse straight past the range.
• Running works once you are fit enough to run slowly. Many people have to walk the hills to stay in the zone, and should.

Reading the session afterwards

A useful check costs nothing. On a steady session, note your pace or power in the first ten minutes and in the last ten at the same heart rate. If the pace drops by more than a few per cent, the session was too long or too hard for your current fitness. As you improve, the same heart rate will carry you further and faster: that is the progress to look for, not a higher number on the watch.

Heat distorts the reading. In a Dubai summer, heart rate at a given pace rises by ten to twenty beats outdoors. Train by heart rate rather than pace, and slow down. See training in the heat.

Medication and exceptions

Beta-blockers and some other medicines lower the maximum heart rate, which makes any formula wrong. If you take one, use the talk test or ask your physician for a supervised exercise test. The same applies if your pulse behaves irregularly during exercise.

A coach can set your zones from a simple field test rather than a formula. It takes one session, and it is one of the first things the coaches of the Club do: how entry works.