Horse training up instantly during session?

[Cydonia]

I've had several horses that when starting a training session, seem to gain all of that skill at once and won't gain anymore.

Example, training for agility using trail and Bending on serpentine, horse will gain 3.15 agility after the first click. Will not gain any more points in agility throughout the session. It's also happened when training for speed, the horse will gain 1.32 in speed then won't gain anything else the entire session in that stat. If this a bug or a weird feature I don't know about?
Thank you!

[Nate]

What you're seeing is the effects of fatigue. Your horse makes big gains while he's fresh, but quickly becomes tired and doesn't gain any more athletic ability. Try giving them some time off and see if that improves things.

[Argent]

Once your horses are able to do longer sessions, you're best off only sessioning them once, for the longest time they can handle. Any further sessions simply waste time and energy.

[Nikolaevna]

Makes fat horses lose weight though burning through the energy.

[Argent]

XD fair point