My 5 exercises to activate the equine core And If interspersed with daily routine can help prevent injury, and encourage strengthening and flexibility within the core & potentially improving performance.
carrot stretches, position against a wall if necessary, and ensure they're on a non-slip surface, using a favourite treat encourage them to reach down towards the outside of the fetlock and holding that stretch for 10 seconds if possible then repeating 3 times on each side. The horse will have to lift its ribcage & core muscles to be able to stretch down and keep its balance.
Abdominal lifts, standing behind the shoulder place your hand on the ventral mid line (just behind the girth) and apply firm consistent pressure watching your horse lift through the withers and back, holding this for a few seconds and repeating 3 times (introduce this exercise slowly and cautiously as some sensitive types may object, consult your vet of physio if aggressive behaviour continues)
Tail pull exercises, also great for activating pelvic stabilizer muscles! Taking hold of the tail stand in a safe position on the side of the hind quarters and gently lean away from the horse allowing them time to resist and balance, watching for the muscles around the hind quarters to contract. this can be done 3 times each way building up to holding for up to 30 seconds.
Irregular poles, a mental and physical challenge, encourage your horse to walk over irregularly places poles keeping a consistent active walk on a longer rein. Do not help them, this will be tricky at first so keep it simple, give them time and expect the poles to be kicked! keep it varied, maybe don't always walk straight at the poles! This is great as a warm up or cool down for a session and can be built up to using raised poles as well!
Back it up!! asking your horse to step backwards under saddle or from the ground causes the hind leg to come underneath them and the core to engage. Starting form a square halt ask them to step backwards, trying to encourage their head to stay low and relaxed. starting with two or three steps, then increase the number as the confidence builds.
It is stressed that you consult your vet before carrying out any exercises if currently being treated for any pre-existing conditions. All these exercises should be carried out with care, if there is any continuous objection by your horse then consult your vet or physio.