Post-exertion muscle soreness/strain can happen to any horse, but the high demands placed on the muscles of a Quarter Horse can easily lead to some soreness. Add to that the fact that they're also prone to some breed-related muscle problems, and you know you need to pay attention to their muscles.
Slow, careful conditioning is the best preventative. Training improves both strength and flexibility of muscle groups and the tendons attached to them. Practicing movements in a controlled training setting will fine tune the reflexes the horse needs for quick changes of direction or fast starts. Training also improves levels of stored carbohydrate, glycogen, within the muscle, the only fuel that can support speed.
Feeding
There's some evidence to support fat supplementation (up to 8%) of the grain portion of the diet in the hard-working Quarter Horse, despite our overall concerns about feeding fat to horses. Studies have found both improved sprint times and higher lactate production during sprints (an indicator of glycogen use) when grain was supplemented with fat.
The likely explanation for this is that the muscle learns to make better use of fat for maintenance energy requirements and during low level, slow work, allowing for better preservation of glycogen stores which are then available for the high speed work. It's important to note, though, that this only works when fat is supplemented in addition to grain, not as a substitute for it as is done to treat Equine polysaccharide storage myopathy EPSSM. The horse still needs grain to build glycogen stores.
To benefit the most from training, and recover glycogen stores quickly after exercise, the muscle needs glucose. Studies in multiple breeds have shown that horses are slow to replenish their glycogen stores, taking up to three days to do so after a major effort. However, some recent studies have found that both intravenous and oral supplementation of simple carbohydrate can hasten this process. This trick has been practiced by human athletes for many years.
Details of how much, and when, for maximal benefit have yet to be worked out and confirmed by studies, but muscle in other species is most "hungry" for glucose in the first hour or two after exercise stops, with increased uptake by muscle continuing over the next 24 hours but dropping rapidly during that time. Providing the horse with 2 to 4 oz. of a glycogen-loading product such as those in our story on page 7, as a paste shortly after heavy training or competition, and again in a grain meal about two hours after the exertion, should give him a good head start on repair and replenishment of hard-working muscle.
Antioxidants are also important to hard-working muscles. They won't boost performance per se, or prevent injuries, but they're extremely important in mopping up the free radicals produced during exercise and preventing injury to cell structures. Vitamin E and selenium should always be supplemented, according to the type of diet and selenium levels in your area.
Tying-Up
Isolated episodes of tying up can also happen to any horse and don't necessarily indicate an underlying muscle disease. Severe overexertion may cause it, and electrolyte abnormalities may contribute to muscle cramping and pain. The precise cause of isolated episodes of tying-up often goes undiagnosed.
