Monitoring resting heart rate to assess fatigue levels and physiological adaptation to training is not a new concept. When taken first thing in the morning after waking, heart rate values can be compared to baseline. Increases in resting heart rate from baseline generally reflect an increase in fatigue or physical stress, indicating that the athlete is not fully recovered. Decreases in heart rate from baseline may indicate increases in fitness when assessed longitudinally while acute changes may be a reflection of positive recovery. A researcher named Heikki Rusko advanced the basic resting heart rate test by adding a postural change component. Simply by measuring the changes in heart rate in response to postural change (i.e., frome supine to standing), further insight into the adaptability and training status of an athlete can be garnered.
In the supine position the heart does not have to work as hard to pump blood to the brain. As the body rests in a relaxed position, there is a predominance of the parasympathetic branch of the autonomic nervous system. In this instance, heart rate is relatively low. When moving from a supine to a standing position, the body must quickly adapt by adjusting heart rate and blood pressure to transport blood to the brain to avoid fainting (syncope). This is a sympathetic response which results in an immediate increase in heart rate and contractility to accomplish blood distribution requirements in the vertical position.
In a rested and recovered state, and athlete will ideally display a relatively quick stabilization in heart rate following postural change. They will have an appropriate sympathetic response where heart rate increases, but once this task is accomplished, heart rate will fall back down to resting orthostatic (standing) values. However, when fatigued, heart rate tends to remain elevated following postural change. It takes much longer for the heart rate to fall back down to a resting standing value. The figure below demonstrates the heart rate responses typically seen in varying states (fatigued, normal and improved).
Rusko’s heart rate test takes approximately 5 minutes to perform and would ideally be done with a heart rate monitor. This test is performed as follows:
- Record the average heart rate from a 2 minute supine resting period (preceded by a minute or two for stabilization).
- Record the heart rate at approximately 15 seconds after standing
- Record the average heart rate for the last 30 seconds of standing (90-120s).
The Rusko heart rate test provides a simple, non-invasive and objective measure of fatigue and training status in athletes. Once baseline values have been collected, coaches can use the heart rate test to assess how the athlete is coping with training and if individual changes are required.
For more details on the Rusko test: http://www.ilog.ca/help/Rusko_Heart_Rate_Test.htm