Even though ice baths are popular between athletes, scientists are still not sure whether they are useful and safe. In a study published in Extreme Physiology & Medicine, Gillian White and Greg Wells reviewed the studies about their immediate effects on recovery. As the long-term and possible negative side-effects have not been properly evaluated, they could not comment on them, even though they might be important.
How does a bout of intense exercise affect your muscles?
A hard workout requires a lot of energy production and creates heat, which lead to an increase in reactive oxygen species (ROS). ROS are highly reactive chemicals that can destroy proteins en lipids. They damage the cell membranes and the coupling between nerve cells and muscle fibres. The latter makes contractions more difficult and less efficient, while the former makes the muscle fibre more permeable to water and leads therefore to oedema of the cell. Oedema compresses capillaries, and makes it more difficult to deliver oxygen correctly and to take waste products away. It also makes you feel sore.
To repair the damaged muscle fibres and to take the debris away, your body starts an inflammatory reaction. Even though you cannot recover without it, it is often too strong and can lead to further damage.
Intense or unaccustomed exercise can also lead to mechanical stress, especially when the muscular contractions are eccentric (contracting while the muscle is lengthening, as for example the quadriceps muscle does when you come down the stairs). This disrupts the membranes, which interferes with contractions, makes the cells more permeable and leads to oedema. Micro trauma can lead to muscle spasm.
Here again, you need an inflammatory reaction to repair the muscles, but it might start off by creating further damage.
How could an ice bath help you?
After exercise, muscles have an increased energy demand as they try to repair themselves and to replace energy stores. Cooling will slow their metabolism down, and therefore generate less ROS. It will decrease the inflammatory reaction and the muscle spasm, and as it reduces the blood flow, it also limits the oedema.
It cannot do anything about the effects of mechanical stress and disruption of the muscle fibres, but as muscle soreness is often due to a combination of mechanical and metabolic stress, it can help. How useful it is will therefore depend on the kind of exercise you have done.
Ice has an analgesic effect, but this can be confusing, since your muscles might not have recovered even though the soreness has disappeared.
Possible long-term effects
ROS are essential to allow your body to increase its anti-oxidant defence mechanism. A stronger defence mechanism will allow you to withstand more ROS production during your next work-out. To destroy all of them is thus harmful. Your body has to learn to regulate them, and this is part of the training effect of a workout.
Without an effective inflammatory reaction you cannot properly repair your muscles. You need it to replace the dead and damaged muscle fibres by stronger ones, and to become a better athlete in the process.
As far as I know, there are no studies examining the long term effects of ice baths, but sport scientists are worried indeed that taking too many of them could reduce the benefits you get from your hard work. The usual advice is therefore only to use an ice bath if you are participating in multi-day events or if you have so many races planned that you cannot recover quickly enough otherwise.
Even if you are a very fit athlete, taking a cold bath is a shock to your body. You could hyperventilate, faint or develop heart rhythm disturbances. As yet, no studies have looked into this problem, and therefore we do not know if it is a real risk. Worse, as it is not clear how helpful ice baths really are, we do not know what the risk/benefit ratio is.
C Bleakley, S McDonough, E Gardner et al. Cold-water immersion (cryotherapy) for preventing and treating muscle soreness after exercise. The Cochrane Library 2012 doi: 10.1002/14651858.CD008262.pub2; accessed on 15/09/2013.
G E White and G Wells. Cold-water immersion and other forms of cryotherapy: physiological changes potentially affecting recovery from high-intensity exercise. Extreme Physiology & Exercise. 2013; 2:26 doi:10.1186/2046-7648-2-26; accessed on 15/09/2013.
Skeletal muscle damage and repair. Ed: P. M Tiidus; Human Kinetics 2007.