Contrast Hydrotherapy

Ice packs and heating pads are familiar rehabilitation tools, but many people have never heard of therapeutic contrasting: quickly changing tissue temperature from hot to cold and back again. This is usually achieved with hot and cold water, either dunking a limb or even immersing the whole body. The technique is most familiar to serious athletes, who believe — without much scientific support, I’m afraid — that it helps them get back in the game quicker.

For injury recovery, contrasting is a good, cheap, safe, and simple idea, and I promise that it feels better than it sounds, when it’s done right. The point is to force your tissues to adapt to the sudden changes, which is stimulatory and requires a lot of metabolic activity and circulatory gymnastics. Basically, contrasting constitutes a gentle tissue workout: stimulation without stress, strong sensations without movement, which may be helpful for a body part that badly needs some rest while it heals.

Stay on the contrasting bus if it seems to be taking you where you want to go. 😉 If not, hop off!

• see also:
• Ice vs Heat
• Ice
• Heat
• Depth
• Contrasting
• Ice & Back Pain
• Baths
• Ice Baths

Contrasting is not strong medicine, but it is at least safe, cheap, easy

Contrasting probably has some minor medical benefits, but it’s certainly not going to work any miracles. There is no reason to believe that contrasting would make a large difference in healing. In particular, it will probably not meaningfully “accelerate healing” from tissue traumas like sprains and strains.

What does the science say? Not much, unfortunately — just a handful of studies, mostly about athletic recovery, and mostly notable for failing to turn up anything promising.1 Even icing alone is barely studied!2

If contrasting promotes recovery from exercise, it can’t be much. That fits a general pattern: nothing seems to help with recovery from exercise, I’m afraid.3 This article focusses on contrasting for recovery from injury, which is definitely unproven, but more reasonable and plausible, costs nothing, and almost perfectly risk-free. But …

Safety first! (Things I must say, even though they are pretty dang obvious)

Limb contrasting is extremely safe in general, and what little danger there is can be avoided with an ounce of common sense. Don’t burn yourself.😃

Please avoid contrasting the freshest injuries that are still hot, swollen, and/or red, because the heat may aggravate the inflammation more than the cooling phase can control. You should use just ice on a fresh injury (note an important exception: back pain usually should not be iced, because it is rarely an “injury” per se). Please wait about three days for an injury like an ankle sprain to calm down a bit before you start contrasting it.

With rapid changes in circulation, there is a small risk of getting dizzy or fainting. This is unlikely when you’re working just with limbs, but be aware of the possibility. Full body contrasting is a different matter. See below.

Comparing contrasting to icing and heating: what’s the difference?

The rationales for contrasting, icing and heating are all nearly identical. Normal icing and heating are simply mild forms of contrasting, because you alternate between applying the ice or the heat and then removing it to let the tissues warm up or cool down. Contrasting just exaggerates this — so it is a refinement and/or hybrid of icing and heating.4

Even though contrasting is very closely related to icing and heating, it does have a couple of noteworthy advantages.

First, icing can be irritating to muscles and/or the nervous system. Like heat, contrasting is usually more soothing, but it’s also more “balanced” — it’s pleasant to cool off after heating, and pleasant to warm up after cooling.

Second, it is possible to create a literally bigger effect with contrasting. It is hard to ice your entire forearm or calf. It is quite easy to dunk them. By immersing a much larger section of your body, you can make more of a splash. Literally and figuratively.

And one disadvantage: while icing and heating are useful almost anywhere on the body, contrasting some anatomy is inconvenient or awkward to the point of pointlessness.

What is contrasting particularly good for? (If anything?)

Experimenting with contrasting should be standard part of rehab from many musculoskeletal injuries, but especially repetitive strain injuries in the extremities. Repetitive strain injuries often need far more rest to recover from than people realize, and any technique for stimulating tissue without stressing it is valuable. Contrasting is also much easier and more practical and effective to apply to the limbs, so the best common candidates for contrasting are:

• plantar fasciitis
• shin splints
• carpal tunnel syndrome
• tennis elbow
• Achilles tendinitis

Knees are a little trickier, but still easy enough to contrast with a little creativity, so two more good candidates are the runner’s knee conditions, iliotibial band syndrome and patellofemoral syndrome.

Hips and shoulders are much more awkward to contrast, and also broader, thicker, and often more padded with fat, so it is harder to change their temperature. The hip joint itself is probably almost completely immune to contrasting, for instance, so there is almost no point in contrasting hip problems. Of course, contrasting is even less convenient or worthwhile for trunk trouble, like back pain.

Ligament sprains are very slow healing, and often become chronically painful, long after it seems like they should have healed. Although it’s doubtful that contrasting will “accelerate healing” from a sprain, it may be worth doing it anyway — after the initial swelling has died down — for the hope of some minor benefits.

How to contrast: delivery systems and procedures

There are many ways to heat up and cool your body parts, and I encourage you to use your imagination and all the tools at your disposal. Bear in mind that immersion is always better than a flow or spray: whenever possible, you want to surround the body part. The major delivery systems for temperature are:

• immersion: in sinks, buckets or tubs
• wrapping: in heating pads, ice packs, or soaked towels
• pouring/spraying: immersion in a stream from a faucet, containers, removable shower head or hose

Contrasting should follow the following basic pattern: three to six alternations between heating and cooling. More is probably getting to be a waste of time. Less than three is probably not worth bothering with either. (More on dosing below.)

1. about 2 minutes of heating: comfortably hot
2. about 1 minute of cooling: cool, not cold (unless you’re tough)
3. about 2 minutes of heating: hotter!
4. about 1 minute of cooling: colder!
5. about 2 minutes of heating: hot as you can handle
6. about 1 minute of cooling: cold as you can handle

Cold sounds nasty to a lot of people, but you’ll be surprised at how tolerable it is when you’re properly pre-warmed.5

A few tips and rules of thumb for contrast bathing

• Stay warm. You generally want to be more thorough with your heat: at least a minute, but as long as five minutes depending on how efficient your heating method is. Heat is more comforting and relaxing than cooling, obviously, and inadequate heating is the most common thing people do wrong with contrasting.
• Finish with cold. You should usually finish a contrast session with cold, particularly if you suspect that you might be a little inflamed. Never finish with heat if you’re concerned about aggravating inflammation. You might choose to finish with heat if your priority is to have a more relaxating experience.
• Stretch when hot. Not that stretching is all that it’s cracked up to be, but if you choose to stretch, do it after or even during the heating. If you have to stop heating to stretch, reheat after stretching before moving on to the cold.
• Dial it up as you go. It is desirable (though not always practical) to increase the intensity of the contrast as you go: that is, the hot gets hotter and the cold gets colder.6

Keep it shallow (because contrasting is unlikely to have much effect on deeper tissues)

Way back in 1998, researchers measured temperatures deep in the gastrocnemius (calf) muscle during a 30-minute warm whirpoool (control group), and a 30-minute contrast therapy group.7 The hot tub did warm deep calf muscle a little bit, a couple degrees on average (with almost as much variation). But the temperature four centimetres under the skin barely budged in the contrast therapy group: the depths of the calf seemed to be largely immune to the treatment. Once the leg was warmed up, dunking it in cold water for a minute did almost nothing.

“It seems unlikely that the physiologic effects attributed to these fluctuations occur,” the authors wrote.

That may have been too sweeping a conclusion, though, based on too little data. There’s probably a more pronounced effect on shallower tissues, which they didn’t measure. Joints and connective tissue may respond quite differently. And just because the temperature doesn’t change doesn’t mean that there isn’t some meaningful stimulation.

But it does suggest that contrasting is more likely to be useful when targeting shallower tissues. And many common sports injuries do affect superficial tissues.

Contrasting different body parts

Here are a whole bunch of specific examples and suggestions for using the best delivery systems for different body parts. Obviously, not every possible solution is covered here. I don’t think I’ve ever looked at this list without thinking of something else. Be creative.

• Wrists, forearms, and elbows are generally the easiest body parts to contrast, especially if you have a double sink, which works very well. Just fill one with hot water and one with cold and move back and forth.
• If you only have one sink, a flow of water from the tap is a reasonably good alternative: just switch from a flow of hot water to a flow of cold. It’s easy! However …
• Wrapping forearms with heating pads and ice packs or soaked towels might be better than a faucet. Few people have large enough ice packs on hand for this, but big ones are available at most drug stores, and they’re not expensive. Soaked towels are messy … but easy and kind of fun. 😃
• Feet also go in double kitchen sinks quite nicely, if you’re limber enough to perch on the counter. And if the dishes have been done.
• Lower legs are generally more difficult. A pair of deep buckets is a bit of work to set up — and you need to have just the right kind of buckets handy, which most people don’t — but the best solution.
• Removable shower nozzles are very handy for contrasting, but the effect is not as strong as immersion, of course — especially if it’s low-flow shower head (for water conservation).
• Bathtub faucets usually produce enough water that the stream is almost as good as immersion, particularly for the feet.8
• Knees are difficult but do-able. Giant buckets are probably the premium option, but only for shorter people, and quiet fussy to set up. Pouring water over the knees is probably the best compromise — especially if combined with soaking the feet and lower legs in smaller buckets.
• The thighs and hips are particularly awkward to contrast, but I’ve pulled it off using a combination of hot bath with a large bin of cold water used as a sitz bath. Fussy to set up, but it does feels great!
• As mentioned, contrasting the back is not the greatest use of the method … but it is easy enough to do in the shower. Many people find it difficult to have so much cold water spraying on them, however, so that can be a bit tricky.

Is the shower good enough for contrasting?

You can take a contrast shower. Whole body contrasting is nice and probably healthful in some general ways, but has limited value for rehabilitating from injuries, which require more intense temperatures, more accurately applied. Immersion of the body part is always the best. Intense heating of only the arm by dipping it in hot water, for instance, tends to cause much greater capillary dilation in the arm than the hottest shower.

The hottest and coldest showers are generally just too hot and too cold to tolerate on large areas of your body … or even just from the splashing if your trying to spray just one part of your body.

A detachable shower head, however, allows you to focus the spray enough to achieve a reasonably good effect.

Dosage: how much contrast hydrotherapy is enough?

Precision with dosage of contrasting is not particularly important. Heat and cool in roughly one-minute doses. But if you stick to the idea of “make it good and hot, and then make it good and cold” you’re doing it right.😉

And how many times should you cycle between hot and cold? Just a single time — one dose of hot, one dose of cold — is a minimal help. Three times is much more of a help, and is probably a good number. Six times is just tedious! There are practical considerations.

And how many times per day? Roughly once per day.9 It’s helpful, but it’s not so good that you should be spending half your day doing it!

This may be powerful medicine in some situations: don’t underestimate its usefulness just because it sounds a bit odd! Try it, have fun, enjoy the sensations, and you may find it more effective at helping you heal than medications or therapy.

The thermal workout

Another interesting application of contrasting is the “thermal workout.” Full body contrasting — switching back and forth between hot tub and pool, for instance — can be surprisingly exhausting and physiologically potent.

It can even be dangerous, so for pity’s sake please be careful and use some common sense:

• Steer clear of this if you have virtually any kind of general health problem, especially cardiovascular disease, or even just low blood pressure.
• The older you are, the more careful you should be.
• Don’t be extreme with the temperatures, and do not underestimate how potent full-body contrasting can be even at more modest temperatures.
• And stay hydrated! This is an important to prevent a surprise drop in blood pressure.
• If you get light-headed, get out, get down, and discontinue the exercise.

Seriously, do not even think about trying this without going slow and taking it easy. This is one of those ideas that desperately needs a medical disclaimer! If you get into trouble doing this, it’s not because I didn’t warn you! Those warnings you see around public hot tubs and saunas? They are not for nothing!

Okay, I hope that’s enough ranting about the dangers to fully cover my butt.

Done safely, even a gentle thermal workout is ideal for wearing yourself out and burning some calories without straining anatomy, and that’s can be a handy component of a rehabilitation or general fitness regimen.10

Did you find this article useful? Interesting? Maybe notice how there’s not much content like this on the internet? That’s because it’s crazy hard to make it pay. Please support (very) independent science journalism with a donation. See the donation page for more information & options.

About Paul Ingraham

I am a science writer in Vancouver, Canada. I was a Registered Massage Therapist for a decade and the assistant editor of ScienceBasedMedicine.org for several years. I’ve had many injuries as a runner and ultimate player, and I’ve been a chronic pain patient myself since 2015. Full bio. See you on Facebook or Twitter., or subscribe:

SUBSCRIBE

Get PainSci updates in your inbox, mostly small, 0–2/week depending on coffee dosage. More info.

Notes

1. Hing WA, White SG, Bouaaphone A, Lee P. Contrast therapy—a systematic review. Phys Ther Sport. 2008 Aug;9(3):148–61. PubMed 19083715 ❐

   This review of the science of contrast hydrotherapy concludes that there is no science of contrast hydrotherapy: as of 2008, no research had ever been done that provides useful evidence that it works or does not work. Contrasting remains a popular and plausible but untested form of treatment.

2. Collins NC. Is ice right? Does cryotherapy improve outcome for acute soft tissue injury? Emerg Med J. 2008 Feb;25(2):65–8. PubMed 18212134 ❐

   This is a 2008 review of just 6 studies of therapeutic icing, only two of them any good: one with slightly positive results, the other showing no effect. So that’s two studies that showed little or no benefit, which is leaning towards bad news, but it’s just not enough data to clinch it. (Four animal studies showed reduced swelling, but we can’t take animal studies to the bank.) The bottom line is just that “there is insufficient evidence.”

   (See more detailed commentary on this paper.)

3. Ingraham. A Deep Dive into Delayed-Onset Muscle Soreness: The biology & treatment of “muscle fever,” the deep muscle soreness that surges 24-48 hours after an unfamiliar workout intensity. PainScience.com. 17437 words.
4. For instance, where anatomically practical, you could contrast by switching between ice and hot water, or a heating pack and ice water … and so on.
5. In fact, if you’re hot enough, you can tolerate a great deal of cold — it’s one of the neat things about contrasting. The cold should feel refreshing or “bracing” at the worst. If you think the cold is too intense, tweak the procedure: more time heating, less time cooling, and reduce the contrast.
6. For instance, when I contrast my arms, I start with two sinks of regular hot and cold tap water — but for the second cycle, I dump a little boiling water into the hot, and add a tray of ice cubs or an ice pack to the cold. Thus the 2nd round of contrasting is much more intense.
7. Higgins D, Kaminski TW. Contrast therapy does not cause fluctuations in human gastrocnemius intramuscular temperature. J Athl Train. 1998 Oct;33(4):336–40. PubMed 16558531 ❐
8. So to contrast feet, the best combination of ease and effectiveness is to sit on the edge of the tub and just use the tap. And yet few tub faucets work very well for the whole calf: the position of the tap is usually too awkward, and there’s not quite enough water for so much more area.
9. More would undoubtedly be better — perhaps three times per day, for a few days, for a situation where contrasting is particularly easy and ideal for the injury — but there are usually strict practical limits on how much contrasting people can do, or should do.
10. For instance, I often cluster workouts as close together as I dare. If I play competitive sports on Tuesday night, I may be pretty sore the next day and just barely have time for my body to recover for my next strength training workout on Friday. And yet I don’t want to be a lazy butt for three solid days. A thermal workout is a perfect way to poop myself out a bit without loading my tissues up with more stress than they can adapt to.