Anyone who takes the recommended standing day for a horse literally is not doing the horse any favours. For a horse that has a natural, pronounced urge to move, a standing day where it has to stand in the box all day is torture.

 

If the horse suffers from a lack of exercise, its muscles become stiff and it can develop stall vices.

A day of standing is particularly bad after a physically strenuous previous day. The horse urgently needs exercise to loosen its muscles and break down the accumulated lactic acid.

It makes more sense not to force the horse to spend a day in the box, but to give it a rest day on which it remains free of the saddle but still gets exercise. A relaxed walk with a halter or a free run in the arena give the horse the opportunity to stretch out and release accumulated energy.