Should I ice it?

Perhaps the most common question I am asked by a patient following an acute injury or episode of pain is 'should I ice it?' This is a completely fair question as there is a widely held belief that icing can make an injury site feel better and heal quicker. Furthermore, the icing of an acute injury is recommended in several acute injury management guidelines (1,2).

Icing, a form of cryotherapy utilized in various forms for hundreds of years has expanded from topical ice application (ice cubes, crushed ice, and frozen peas) to continuous cold flow devices, cryotherapy chambers, and immersion pools. This post will focus on research from topical applications such as ice and continuous flow devices as these are the most widely utilised and available (Fig1).

Ice cubes

Frozen peas

Continuous flow device

Fig1. Examples of topical cryotherapy modalities

What does icing do?

Cryotherapy results in local physiological changes, namely reduction in blood flow, metabolism, skin and deep tissue temperatures. Reductions in skin and deep tissue temperatures have widely proven to result in an analgesic effect. One reason for this is slowing nerves ability to send signals from the injury to the spinal cord and brain. Indeed, reducing skin temperature to 15 degrees slowed nerve-firing rate by 33% and was associated with a local analgesic effect (3).

Unlike the pain inhibiting effects of cryotherapy, it is less clear as to the impact of reducing superficial and deep tissue temperatures on tissue healing. It is hypothesised reductions in blood flow and metabolism may positively influence tissue healing by reducing ischaemic damage to cells on the periphery of the primary injury (4). As a result, collateral damage to the injury site is reduced, resulting in a less severe injury.

Unfortunately, there are no human physiological trials to support the notion that reducing blood flow or metabolism results in optimal tissue repair. Animal studies have proven paradoxical as on the one hand application of cryotherapy reduced injury site size (5,6) but on the other led to signs of a sub-optimal repair (7,8). The mechanisms underpinning this are unclear but may be due to inhibition of white blood cells, which are responsible for removing dead cells and signalling healthy cells to enter the injury site

Does it work?

Clinical effectiveness of cryotherapy in terms of facilitating early return to function is unconvincing. The majority of research in this space comes from post-surgical populations. Except for pain reduction, the majority of studies show little to no effect on swelling or range of motion following cryotherapy. The limited available evidence examining cryotherapies effect on closed soft tissue injuries such as ankle sprains and muscle tears is equally unconvincing for improving outcomes.

Several experts in the field of cryotherapy cite methodological inconsistencies and inappropriate dosing as possible explanations for cryotherapies lack of evidential clinical effectiveness. The magnitude of physiological changes are dependent on several factors including:

· Cryotherapy modality (ice cubes, frozen peas or continuous flow device)

· Level and frequency of compression

· Duration of cooling

· Depth of tissue

· Quantity of subcutaneous fat

It is beyond the scope of this post to go into detail regarding each factor but it is logical to expect deeper tissues to take longer to reduce in temperature and for their absolute temperature reduction to be less than superficial layers. In fact, reducing intramuscular temperatures to 7 degrees took three times longer in skin folds of 40mm compared to 20mm (9). Further to this, the cold-induced effects of cryotherapy on microcirculation appear to be attenuated at 8mm compared to 2mm (10).

Cryotherapy modality and associated compression may be more important than widely considered at inducing these physiological effects. Ice cubes wrapped to the skin was more effective at reducing deeper tissue temperatures than branded continuous flow devices (11,12). Further to this constant compression as opposed to intermittent or no compression resulted in greater rates and absolute reductions in tissue temperature (11). However, research is on-going in this area and there is currently no consensus on optimal modality choice.

Break it down for me!

Current acute injury management guidelines recommend crushed ice application for between 10-30 minutes repeated within 2 hours dependant on pain and discomfort (1,2). Even in a lean athletic population, it is unlikely that these parameters will result in significant reductions in deep tissue temperatures. As a result, the physiological response is likely to be predominantly one of pain inhibition.

For the practitioner or patient wishing to have, a cooling effect on deeper tissues a bespoke approach is required taking into consideration the depth of the tissue and the quantity of subcutaneous fat. This is likely to require periods of cooling in excessive of the current clinical guidelines and potentially beyond the threshold of the patient to tolerate i.e > 60 minutes. Furthermore, given the lack of human trials and the paradoxical evidence from animal studies, it is questionable as to whether deep tissue cooling following acute injury is appropriate and efficacious.

So, should you ice it?

Well, icing will not directly make much difference to your overall injury outcome i.e better healing or quicker return to function. However, due to its analgesic effect may reduce the intensity of the pain experience. This in turn offers benefits beyond pure tissue healing such as restoring confidence, encouraging muscle activity and movement, which, applied in optimal doses facilitates tissue healing (13). Therefore, if you have an acute injury and it is painful, sure ice it as per the current guidelines. If pain is not a problem then do not worry about it.

Thanks for reading and I would love to hear from patients and practitioners and get their thoughts and experiences of cryotherapy following injury.