How can I keep my horse fit over winter?

need arises.
If you are lucky enough to have access to an all weather or indoor arena
These are a fantastic luxury at any time of the year particularly in winter. They can also be used for turnout if the surface allows. If you can try to arrange sessions with others on the yard so that one of you can set up some jumps or grids that you can both use. Having a course set up in advance will allow you to increase the time you can spend riding or grooming. 
It may also be possible to travel to an arena for some exercise but make sure roads are safe before travelling. Going to a different arena is also good practice for competitions and will help your horse to adapt to strange environments. Depending on your location you could also travel to a nearby beach hills or forest. You and your horse will love it and its a great way of mixing it up and including some fast work.
Dont be afraid to try new things!
If you are confined to an arena try some dressage including some music for variety. Now is also a good time to work on transitions or movements or to introduce polework or gridwork. Take care not to overdo the practice on individual movements as this can lead to boredom or injury. Dont underestimate the value of lungeing or longreining. Even a 20 minute session can help to keep your horse fit if you are running short on time.
People often ask about the use of walkers
Although not everyone has access to one they can be a great way of maintaining fitness with reduced time but be careful horses will need to be trained to use them and over may exacerbate injury.
Always remember if the weather is very icy dont be afraid to avoid exercise on that day
Slips or falls on ice can be extremely serious so best to err on the side of caution and wait until another time. If it is still possible to turn out ensure your horse is well rugged and all water troughs are free from ice. Try to use this down time to spend some quality time with your horse with an extra long grooming session massage carrot stretches or you could even teach them a new trick. Your horse will greatly appreciate any extra time with you.
Grooming
When time is short it is not always