Saffy, surfaces and striding out

Kate (who owns Saffy) sent me this great clip of her schooling. Saffy has been working since she left here last year but not competing, because Kate's just had a baby, but they have their sights firmly set on jumping again this year.

This clip is great because it shows Saffy's powerful trot and big movement  - Kate says she is moving even better now, a few weeks further into her schooling, which is fantastic news.

Looking at the bouncy surface in Kate's school and Saffy boing-ing along I realised this tied in with something I was talking about with Charlotte, Bryan's owner, when she was down to collect him this weekend.  She was commenting that Bryan felt level in our arena but wasn't demonstrating full extension. This was explained when she jumped off Bryan and felt how hard our arena surface is.

Its sea-sand and has some "give" but in wet weather (most of the time!) it packs down to be a relatively tough surface - level and smooth but unforgiving to weak digital cushions.  I find it very useful because it shows up lameness but rehab horses - who normally don't have completely healthy digital cushions - won't typically stride out quite as much as they would on turf or on a rubber surface.

So why would that be?  Its most likely down to proprioception - the same neural input which makes human runners shorten their stride when running on hard surfaces to protect their joints from concussion. Proprioceptors are nerves which are found in joints and in feet - and in both horses and humans proprioception is reduced by shoes.

In a barefoot horse or human proprioception gives awareness of the type of surface and the amount of concussion it is delivering to joints.  Once that horse or human increases speed on a hard surface then proprioceptors warn of increased concussion for joints; at higher speeds the best way to protect joints from this increased concussion is to slightly shorten your stride so there is less impact at each footfall.

If the horse or human moves onto more forgiving ground then they can increase stride length again without any damage - which of course is why dressage is performed on a nice, bouncy, surface rather than on the roads and why racecourses and athletics tracks have perfect surfaces to allow horses and humans to run their fastest.