Practitioners frequently get asked whether to use heat or cold for soft-tissue pain and injury problems. Of course, the correct answer is always that it depends on the nature of the client’s condition. But what are the key factors upon which heat or cold therapy depends? New research indicates the standard guidelines for hot/cold therapy may need to be reconsidered. In this post we’ll take an in-depth look at cryotherapy and some of the recent controversies around its use.
Cold applications, most commonly known as cryotherapy, involve the application of cold directly to the body for therapeutic purposes. Most frequently, cryotherapy involves applying ice after an acute injury. Ice applications are used to manage and reduce inflammation and reduce pain. However, that long held belief has recently come under scrutiny as a number of authors are suggesting that icing an acute injury may not have the beneficial effects we once thought. Let’s take a look at the key physiological effects of ice applications to better understand their use and if it’s time to reconsider them.
Decreased nerve conduction velocity and pain: Cryotherapy slows the rate at which nerve impulses are propagated along a peripheral nerve. The slowing of this impulse affects both sensory and motor signals in the nerve. One of the most effective uses of cryotherapy, and the reason for its implementation, is the effect it has on reducing pain sensations through decreased nerve conduction velocity. Relieving pain is a good thing, but should be weighed against the other effects produced by the cryotherapy application.
One way that reduced nerve conduction velocity is used in a therapeutic setting is reducing the stretch reflex, also called the myotatic reflex. The stretch reflex is activated by the muscle spindles when they are stretched either too far or too fast (such as in an acute whiplash). Overstretching a hypertonic muscle can also activate the muscle spindles, causing increased muscle tension.
Cryotherapy can decrease the activation of the muscle spindles, which is a benefit for stretching. However, it also decreased the pliability of connective tissue, which is detrimental for stretching. There are times when the neuromuscular resistance to stretching is the key obstacle, such as in an acute muscle spasm. In this case, the neurological benefits of ice outweigh its detriments. One must weigh the benefits of decreased neurological activity vs decreased connective tissue pliability.
Decreased Cellular Metabolism: Cold applications slow down the cellular metabolic activity in the region where the cold is applied. This cellular metabolic reduction has long been hailed as a primary benefit of cold applications, especially in acute injuries. The theory was that it shortens the recovery period from the injury. However, this effect is the factor that clinicians and researchers suggest prolongs the healing process.
The argument goes something like this… Humans have been evolving for millions of years. As part of that evolutionary survival process our bodies have developed an injury response process that involves inflammation following an acute injury. However, in the last several decades we have decided that we need to stop that process because it is detrimental to the healing response of tissues.
It is good to question this stance of whether or not it is beneficial in the healing process to impair the body’s natural healing response. Like all good clinical questions, it should be followed up with research to test the hypothesis. Some initial studies have questioned the therapeutic benefit of reducing inflammation. In one study, treatment comparisons of patients who received ice applications immediately post injury in order to reduce inflammation were compared with those that did not receive ice applications. The ones that did not get ice applications actually fared better. We still need more well-designed studies to investigate this idea, but it does look like it may be time for a paradigm shift.
Decreased Circulation: In response to cold sensations, the smooth muscle cells in the walls of the superficial blood vessels contract and vasoconstrict. Vasoconstriction with cold applications is more pronounced in some regions of the body, such as the distal extremities. The effect of reducing circulation is a physiological effect of ice that may not be desirable.
In addition, tissue healing is enhanced by chemical mediators carried through the blood stream and reducing their movement may interfere with the tissue healing response. Again, this is a physiological response that has developed in the human and mammalian bodies over millions of years, so it seems likely that there would be physiological benefits to these chemical’s circulation and detriments to their limitation.
Edema: Another argument against decreasing circulation is the effect ice has on lymphatic drainage. Edema occurs in the region of a soft-tissue injury after it has occurred. Current thought suggests that excess edema is not beneficial and should be reduced; hence, the use of ice.
However, edema also limits movement in the region and reduces the likelihood of further injury. Edema also increases our sensitivity to pain from pressure on the pain receptors. We generally consider this a bad thing because it hurts, but there is actually a benefit to the increased pain because it helps us limit further movement that could produce greater tissue damage.
Reducing circulation through cold applications also slows down lymphatic drainage and may actually have another detrimental effect on the tissue repair process as a result. Damaged tissue byproducts must be removed from the body and they are removed through the lymphatic system. It may be that cryotherapy for reducing edema could be detrimental in a number of ways.
In Sum: Most therapeutic interventions have positive and negative effects. In each client case we must weigh the potential positive effects against the potential negative effects to evaluate whether it makes physiological sense to pursue a particular approach. These studies may not be enough to alter the way we currently use ice in treatment. However, they should spur us on to pursue additional research in order to find if ice should continue being used like it has or if it is time for a paradigm shift.