Pace Calculator

Training Through Pace and Heart Rate

Pace is a rate of activity or movement, while heart rate is measured as the number of times a person's heart contracts per minute. Pace and heart rate have a positive correlation — higher pace corresponds to higher heart rate. Using both in training can help improve performance, avoid over-training, and track progress and fitness over time.

Measuring and Estimating Heart Rate and Heart Rate Zones

Heart rate can be measured in different ways, from devices such as heart rate monitors to simply looking at a watch while measuring pulse at a peripheral point such as the wrist or neck. Typical adult resting heart rates (RHR) commonly range from 60–100 beats per minute (bpm), though some sources cite 50–90 bpm as the normal range. Generally, a lower RHR indicates more efficient heart function, though RHRs below 50 bpm can be a sign of an underlying heart condition or disease — as can RHRs above 90 bpm.

Maximum heart rate (MHR) is most accurately measured using a cardiac stress test, which involves measuring heart function at progressively increasing exercise intensity, typically lasting 10 to 20 minutes. Since this is often inconvenient, MHR is frequently estimated using the widely-cited formula:

While commonly used to define training zones, this formula lacks a standard deviation and is not considered a precise predictor of MHR by health and fitness professionals. MHRs also vary significantly between individuals — even among athletes of similar age within the same sport. Nevertheless, it serves as a useful reference. An exercise intensity of 60–70% MHR is generally considered ideal for fat burning. Refer to the exercise zones chart below for further detail.

Aerobic vs. Anaerobic Exercise

Aerobic and anaerobic exercise mainly differ in the duration and intensity of muscular contractions, and how energy is generated within the muscle. Generally, anaerobic exercise (~80–90% MHR) involves short, intense bursts of activity, while aerobic exercise (~70–80% MHR) involves sustained light-to-moderate activity. An exercise intensity of 55–85% MHR for 20–30 minutes is generally recommended to achieve the best results from aerobic training.

In aerobic exercise, sufficient oxygen allows muscles to produce all necessary energy. In anaerobic exercise, the cardiovascular system cannot supply oxygen fast enough, so muscles break down glucose — producing excess lactate, which causes the characteristic burning sensation and eventually makes continuation impossible if not cleared from the bloodstream. In aerobic conditions, lactate is used almost as quickly as it forms at low intensities, and only trace amounts leak into the bloodstream from the muscles.

For marathon training, maintaining an aerobic threshold pace — a low-intensity, sustainable pace that balances fat and carbohydrate utilization — is key. This pace can typically be held for several hours, and increasing it is a central goal of most marathon programs.

The anaerobic threshold pace marks the point where glycogen, rather than oxygen, becomes the body's primary energy source. While anaerobic training improves overall fitness, it is not sustainable for long distances. However, training at or slightly above the anaerobic threshold — the level at which lactic acid accumulates faster than it can be removed — can also be beneficial.

According to a 2005 study, the most accurate field method for estimating anaerobic threshold is a 30-minute solo time trial at maximum effort, averaging heart rate over the final 20 minutes. This gives an estimate of lactate threshold heart rate (LTHR). If performed in a group setting, the duration must be extended to 60 minutes. Aerobic threshold heart rate can be estimated by subtracting 30 bpm from LTHR.

Threshold training aims to postpone the point at which lactate builds up in the bloodstream — effectively delaying fatigue and allowing a person to run farther and faster.