A test for Overtraining?

Quite an interesting paper was released today on glucose metabolism rate and peripheral insulin sensitivity of horses undergoing training. You can take a look by clicking the link here, but basically they too 12 standardbred horses and broke them into two groups. They trained them on a treadmill and with one group they ramped up the intensity to stimulate overtraining in the horse and the other group they left training as normal. The first group saw mean glucose metabolism rate and mean glucose metabolism rate-to-plasma insulin concentration ratio changes that the control group did not have which might lead investigators towards a simple test that would indicate if a horse was overtrained or not.