Taking a hot shower, or enjoying some time in the sauna or the steam room, were the conventionally accepted ways to keep your muscles from getting sore after exercise. If you could arrange for a nice, hot, vigorous rubdown after your workout, that was even better. It turns out those were the worst things you could do if you wanted to avoid having sore muscles the day after a vigorous workout. Understanding the physiology of muscle soreness makes it easy to see why.
Causes
Pinpointing the precise cause of muscle soreness has eluded science. There are, however, general ideas, including what does not cause soreness: Lactic acid. It used to be thought a buildup of lactic acid from extreme exercise caused muscles to ache. The prevailing theory now is that soreness is caused when muscles suffer micro-tears from exertion. Eccentric exercises --- in which muscles are stretched --- cause more soreness, as do new exercises the muscles have not yet become used to performing.
Effects
Tearing muscle fibers, no matter how microscopically, damages and creates dead tissue in the muscles. The body reacts to having dead and damaged tissue by creating swelling to minimize movement and prevent additional damage. Like it does when you have a toothache or any other injury, swelling also stimulates nerves so they send a pain signal to the brain, alerting it that damage is being done to the body. This process takes time, which is why muscle soreness from exercise typically sets in hours later, or the day after, a tough workout.
Treatment
Applying cold is the typical treatment for swelling because cold causes swelling to contract. Heat, on the other hand expands tissue and will increase soreness. It also helps to apply cold shortly after an intense workout. This constricts blood vessels that have opened to handle increased blood flow during exercise. Clamping off these open vessels slows, or minimizes, swelling in the first place, so soreness doesn't set in as acutely the next day.
Methods
Icing down after a workout, or when your muscles are sore, doesn't mean covering yourself with ice packs. The best way to get your muscles cold to prevent or treat muscle soreness is by taking an ice bath. Fill your bathtub half way and add either a 5-lb. bag of ice, or a few trays of cubes from the freezer. Ease into the water slowly until you're in up to your waist. Try and relax. Stay in the water for 10 to 20 minutes to shrink swelling or constrict open blood vessels to prevent next-day soreness.
