hello

to have an exact measurement, try to design a good performance curve and within a logical time table, consider the progression line of athletes. hoping to be effective to you. let me know if you have more help.  

Best Regards

Dear Frenkel:  That I should be so fortunate to have the opportunity to travel to Spain....

Or to Cuba  -  frankly to anywhere warmer than Minnesota...

I agree with your opening thought, that of overtraining - specifically as concerning younger athletes.  Overuse ( over training ) is much easier to tolerate for a younger person - but the loss of power potentiation due to hyper tonus and a shortened muscle can easily affect anyone.  The problem may not be obvious if no pain or stiffness is present that would evidence an overactive muscle spindle cell issue resulting in a reduction of the relaxed length status.  

The reduced stride length of an elderly individual usually is easily noted due to the % of change - the highly trained athlete may suffer a minor reduction in speed/power - or may even offset a stride length reduction.  I would hope to see a measurement to track the status of stride length/muscle tonus.

Your athletes could benefit from a program of high pressure - deep tissue massage to preserve a full length status of the relaxed muscle group which would give the muscle body the best opportunity to gain work capacity and help to avoid tendon injuries.

Some suggestions:

https://www.youtube.com/watch?v=fb6xlI4bkmE   10 minutes in - massage treatment

https://www.ncbi.nlm.nih.gov/pubmed/20086639

https://www.ncbi.nlm.nih.gov/pubmed/20086639

If the muscle tissue is maintained to be relaxed it will be more likely to respond to input and be competent - and be less likely to be overused and suffer collagen degradation.

This seems a safer approach to encourage gains - reduce injury.