For quite a while now athletes have been advised to take their morning resting heart rate as a way of determining if they have recovered sufficiently to train hard that day. Elevated MRHR suggested incomplete recovery, illness or even the beginnings of overtraining syndrome.
This made me wonder if more information could be harvested from a more detailed device like an EKG. A quick search led me to this paper where they used heart rate variability (HRV) as a way of prescribing training intensity. Using this system the athletes improved significantly more than the scheduled training control group.
Endurance training guided individually by daily heart rate variability measurements.
We concluded that cardiorespiratory fitness can be improved effectively by using HRV for daily training prescription.
This study used athletes participating in a training camp (overreaching) and concluded that HRV can be used to measure the training state of athletes.
Changes in heart rate variability of athletes during a training camp.
In conclusion, HRV might be used to monitor the training state in athletes.
Here they measured the exercise dose-response relationship using HRV
At this time it is unpractical to do this yourself but it does show you we are near an age where strapping a device to your chest and maybe pricking your finger for blood tests (microfluidics and MEMS anyone) may be all that is needed to come up with a near optimal training system. Gone are the days of scheduled under or overtraining.
Anybody have an extra EKG kicking around they want to lend me? Oh never mind here is how to make one for less than 5 bucks.