Common signs of fatigue:

Panting/drooling
Knocking/kicking poles
Tripping/bumping into “anchor” objects
Unable to maintain trotting gait (e.g., jumping over poles when they could trot consistently a few reps before)
Poor form and posture (e.g., head dropping, excessive bouncing, back twisting instead of maintaining straight, limbs swinging out)
Common stress signals (e.g., scratching, yawning, sniffing, head shaking, checking out)

Remember less is more. It is better to end the session sooner than later.

Signs of fatigue