Heart Rate Monitors
The first wireless heart rate monitor (HRM) was introduced in 1983 and since then many improvements have been made e.g.
The use of an HRM to set exercise intensity is based on sound physiological principals - 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 your maximum heart rate.
Many factors can alter your heart rate:
Heart rate drift
This is the increase in heart rate seen over time while exercising at a constant workload. 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 consecutive beats can vary considerably. At rest, heart rate variability is larger in aerobically trained individuals than in untrained individuals.
The nervous system influences the resting heart rate by means of 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 large variability for each respiratory cycle we say there is a high vagal tone and when there is low variability we have low or poor vagal tone.
The heart rate is a useful parameter for monitoring the reaction of the athlete's body to training and the HRM provides a convenient method for measuring and recording heart rate during exercise.
Heart rate, on its own, 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.
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