It is well known that longer, more intense training sessions increase the risk of overtraining when not followed by an adequate recovery period. The main problem for athletes is measurement — it is difficult to assess the effect of training on the body with a high degree of accuracy. However, heart rate variability (HRV) can provide athletes with this information, which can be used for such purposes as to determine how well the body is adapting to training, if more rest is necessary, and if the athlete is receiving the right training effect.*
Traditionally, training zones have been considered the best measure of training intensity. These can be established through heart rate, maximum oxygen uptake (VO2 max), lactate threshold, or a combination of several of the above. However, these training zones do not take into consideration the cumulative effect of exercise over a number of workouts. This means that finding the balance between training intensity/duration and rest/recovery in order to achieve optimal fitness can be difficult.
How it Works
Heart rate is regulated by the autonomic nervous system, which is made up of sympathetic and parasympathetic nerves. The sympathetic nerves excite the heart, causing heart rate to increase, while the parasympathetic nerves cause the heart rate to decrease. Variation in heart beats was discovered in 1966, reports Biocom Technologies, when it was shown that disparities of a few milliseconds between heart beats was normal. The variation in heart rate is due to the attenuation of the parasympathetic activity when a person inhales, meaning heart rate tends to speed up during inhalation and slow down during exhalation.
HRV can help signal whether you are overtraining, and as such hindering any efforts to achieve optimal performance. During exercise, heart rate speeds up and heart rate variability becomes less pronounced, explains Peak Performance. In contrast to this, your heart rate variability is increased when you are more physiologically relaxed and unstressed. Therefore, a reduced HRV after an exercise session suggests an incomplete recovery, reduced hydration, or other external stressors. Your heart rate variability can also be affected by age, gender, genetic makeup, type of exercise and environmental factors, says Peak Performance.
As useful as heart rate variability can be, questions remain regarding its reliability as a metric; lack of measurement standardization and accuracy are the most widely cited concerns. For many, though, these issues are offset by HRV’s accessibility and ease of use.
In the broadest sense, heart rate variability helps reduce the guesswork involved when trying to assess your body’s physiological state of recovery from training. This information can be quite useful in determining when your body is ready for additional effort.
*At rest, the body system is in balance. A workout disturbs this balance by putting the body under adaptative stress. Together the stress and reaction is known as the training effect.