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Heart Rate Monitors Heart

The first wireless heart rate monitor (HRM) was introduced in 1983, and since then many improvements have been made e.g.

  • Coded transmission process (from the chest strap to watch) to reduce interference with other HRMs
  • Ability to capture large amounts of data
  • Functions to aid with training, e.g. high and low ranges for setting training zones
  • Ability to download the captured data onto a computer and then analyse with special software
  • Ability to determine your VO2 max

An HRM's use to set exercise intensity is based on sound physiological principles - as the work increases, oxygen consumption (VO2) and heart rate increases in a linear relationship until near maximal intensities. Heart rate is easier to measure than oxygen consumption, and the relationship between them has been established. However, there is one critical component - knowing yourmaximum heart rate (HRmax).

Factors affecting Heart Rate

Many factors can alter your heart rate:

  • Stress
  • Illness
  • Overtraining
  • Medication
  • Time of day
  • Food and drink (Caffeine)
  • Altitude
  • Temperature
  • Hydration levels
  • Weather conditions
  • Heart rate drift
  • Heart rate variability

Heart rate drift

This is the increase in heart rate seen over time while exercising constantly. Some studies have found that your heart rate can increase by as much as 5 to 20 bpm during exercise lasting 20 to 60 minutes even when the work rate does not change.

Heart rate variability

This describes the variations in the intervals between consecutive heartbeats. Even when the heart rate is stable, the time between successive beats can vary considerably. At rest, heart rate variability is more significant in aerobically trained individuals than in untrained individuals.

Vagal Tone

The nervous system influences the resting heart rate using signals from the Vagus nerve. Resting heart rate will fluctuate with the respiration cycle. Inspiration is accompanied by heart rate elevation and expiration with a drop in heart rate. When there is considerable variability for each respiratory cycle, we say there is a high vagal tone, and when there is low variability, we have weak or poor vagal tone.


The heart rate is a useful parameter for monitoring the athlete's body's reaction to training, and the HRM provides a convenient method for measuring and recording heart rate during exercise.

On its own, heart rate does not allow for an accurate assessment of the training effectiveness over time and cannot tell the coach or athlete which aspects of the training program are having a positive or negative influence on training adaptation.

Page Reference

If you quote information from this page in your work, then the reference for this page is:

  • MACKENZIE, B. (1997) Heart Rate Monitors [WWW] Available from: [Accessed