Practical Science on Movement and Pain
Practical Science on Movement and Pain
Why do athletes wear medical tape on various parts of their body during competition? During the 2012 Olympic games, numerous athletes are sporting interesting formations of “kinesiotape” on their shoulders, knees, and backs. David Beckham and Serena Williams are also fans of the tape. Perhaps this is just because David and Serena are fashionable types – they are bored with tattoos and looking for the latest in alternative body adornment. But wait, Lance Armstrong is also a fan of taping, and he’s a no nonsense Texan all American hero type. Surely he wouldn’t wear it just for its fashionable appearance. Here’s what Lance wrote about the magical effects of the “Tape” in his book:
“Something better than any laser, wrap, or electric massager…The Tape. It is a special hot-pink athletic tape that came from Japan and seemed to have special powers. Every morning before the stage, they would tape us all up, different parts of our bodies . . . Sometimes we’d be so wrapped up in hot-pink tape that we’d look like dolls, a bunch of broken dolls. But the next day the pain disappeared–it was gone.”
C’mon Lance! He makes it sound like the tape wouldn’t have worked if it wasn’t hot pink! But can we trust Lance on whether the tape works, even though we can’t trust his fashion sense? Probably not. Pro athletes have a habit of buying into nonsense, so we shouldn’t place too much stock in their endorsements. However, there are many trainers that swear by the tape, and claim their athletes feel better as soon as its on.
So does the tape help athletes and if so how? And does it need to be pink? As discussed below, there are a few studies showing some minor short term improvements in movement and pain levels as a result of wearing the tape. And the likely mechanism for the efficacy of the tape illustrates one of the main themes of this blog – that the best explanation for why a therapy works is usually its effects on the nervous system. Here’s the deal.
Before getting into the studies, first a bit of background on the skin and its close relationship with the brain. The skin and the brain go way back, all the way to the embryo, as they are both part of the ectoderm. Skin is where we interact with the environment, so it is tasked with the job of detecting even the most minor and subtle changes in pressure and movement. Thus, the skin has a large variety and number of mechanoreceptors, and the brain has a large area devoted to processing the significant sensory information that comes from them. In short, the skin is a sensitive organ that does a lot of talking, and the brain is very interested in what it has it say. For these and other reasons, the skin is sometimes referred to as “the outside of the brain.” What a disgusting image.
One mechanoreceptor in the skin that is particularly relevant to this discussion is the Ruffini corpuscle. Ruffinis fire continuously when the skin is placed under lateral stretch, which is exactly what a proper tape job seeks to do. So, taping will cause ruffinis to send continuous information to the brain the whole time the tape is there. Are there any conceivable benefits to this flood of mechanoreception? Here are two: sensory gating and “movement illusion.”
Sensory gating is the process by which the brain’s response to a stimulus become blunted by a competing stimulus. One example of sensory gating is when mechanoreceptive information distracts the brain from processing pain signaling, called nociception. This is why we instinctively rub an area that gets injured – to create non-threatening sensory signals to compete with the threatening harm signals for the brain’s attention. This process works in reverse as well – if you feel pain in a joint you will probably be less coordinated there because the brain will be too distracted by the pain to fully process the sensory feedback necessary for coordinated movement.
So, tape that stretches the skin over a painful joint will send a flood of mechanoreceptive information to the brain, which distract the brain from focusing on the nociceptive signaling, which might reduce pain a little and maybe improve coordination.
The other possibility is that the novelty of having the skin stretched continuously can fool the brain into thinking that the joints adjacent to the stretched skin have moved (which is the usual reason that skin stretches). In some previous posts I have discussed sensory motor illusions and their capacity to change the body maps and modulate pain. In the context of skin stretch, there is a study showing that stretching of the skin around the fingers created an illusion that the fingers are moving.
Thus, taping near a joint could fool the brain into thinking the joint has moved. And, more importantly, that the joint has moved without pain. Imagine that your shoulder hurts when it goes overhead. Then we place tape on the shoulder to stretch the skin in the same way it would be stretched when the shoulder is overhead. Perhaps the brain will interpret the sensory information from the skin stretch as meaning that the shoulder is now capable of painfree flexion. This reduces threat, which reduces pain.
So there’s two potential ways that tape might help an athlete. Now what do the studies say?
One study of patients with shoulder pain found that the tape improved range of motion but not pain. The control group was given “sham taping” and had no improvements at all. In another study on patients with whiplash, taping yielded pain relief and improvements in range of motion compared to the sham taping group. The effects were instant and continued for a day. In another study, taping was found to be just as effective as cervical thrust manipulation in the management of neck pain.
The most interesting study came out recently. It was known before the study that tape around the ankle could improve postural control, and it was also known that muscular fatigue tends to degrade postural control. So the study was set up to test whether tape could prevent postural degradation resulting from fatigue.
Researchers assessed subjects’ posture with and without tape around the ankle, and before and after fatiguing the muscles around the ankle. The tape had no effect on posture when the muscles were not fatigued, but significantly improved postural control when there was fatigue. The researchers concuded that fatigue impairs posture by interrupting the normal flow of sensory information from the mechanoreceptors in the fatigued area. The tape adds enough new sensory information to correct for this deficit and restore postural control.
Based on the above, taping a sore joint is an interesting idea that might help and certainly won’t hurt. No one seems to agree on the exact way to tape, so you have a good chance for a result just experimenting with what works. By the way, not just any tape will work very well, you need tape specially designed for the job, such as kinesiotape.
I should mention that Diane Jacobs is a great source of information and insight on the effects of skin stretching. She is a physical therapist who makes skin stretching her main mode of treatment, and she and her many disciples claim excellent results in pain relief and function from this technique, which she calls “dermoneuromodulation.” She has a manual describing the details of her technique, including her theory (which I didn’t discuss here) that skin stretches can unkink cutaneous nerves that may be the source of the pain. Diane has a blog and discusses skin extensively at the somasimple forums. So you can get the “skinny” from Diane. Ouch!