Why is heart rate alone not enough to assess the strength and efficiency of the heart?

The heart rate is affected by many other bodily functions including body temperature, body chemicals known as hormones, of which common examples are adrenaline and thyroxin. The physical state of the heart also affects its rate of beating, for example local damage to the heart muscles due to lack of oxygen, or oversized expansion of the heart muscles due excessive training can all slow down the heart rate.

These factors make the heart rate very unreliable as an indicator of fitness and responsiveness to physical training. Cardiac vagal tone at rest responds only to pumping strength and efficiency of the heart making it a more reliable indicator of strength and efficiency of the heart.

The NeuroScope™ can be used for serial measurement of baseline cardiac vagal tone in athletes or in sports/health clubs to quantify the cardiovascular response to the exercise being performed by the individual. This is also useful to cardiac patients who have been prescribed exercise under supervision for their rehabilitation. When the athlete stops training the baseline cardiac vagal tone falls towards the average level in sedentary human population. Again the NeuroScope™ can be used to assess the deterioration of the athlete's cardiovascular reserve during detraining in circumstances such as injuries