Prof. Peter Fricker OAM
Director – Australian Institute of Sport (AIS)
Director Medical Services
2004 Australian Olympic Team

What is heat retention?

Heat is one of the best modalities employed in the treatment of injuries as a result of exercise or trauma.

Heat retention implies an artificial elevation of surface (skin) temperature and an elevation of the temperature of the deeper soft tissue of the body. At the same time heat retention relies on the prevention of vasoconstriction (or narrowing of the blood vessels) within the skin and deeper tissues, and the promotion of vasodilation (or opening) of the blood vessels within these tissues.

The benefits of such retention include the promotion of increased blood flow to soft tissues that are in the phase of healing in response to injury. Increased blood flow facilitates the clearing of cellular debris and facilitates the deposition of those cells, which need to be introduced to injured tissue to commence rebuilding of this tissue. Similarly, oedema needs to be removed and this relies on an increased perfusion of the injured tissues by the small blood vessels.

Another important benefit of heat retention is the promotion of optimal muscle function at a temperature, which needs to be about 1ºC higher than the normal body’s resting or basal temperature. This concept of improved muscle function at a higher temperature than at rest is best portrayed in the concept of ‘warm up’ prior to exercise.

The benefits of muscle warm up

There is good evidence to suggest that increasing the temperature of muscles in the body to 38ºC increases the reactivity of muscle, increases the elasticity of muscle, and thus promotes optimal muscle function.

The treatment of injury

Acute injuries must be managed by the R.I.C.E. regimen. This acronym stands for ‘Rest, Ice, Compression, and Elevation’. Most sports therapists are familiar with this regimen and it relies on the use of frequent applications of cold together with compression and elevation of injured tissues within the first 48-72 hours of injury. The protocol limits the amount of damage done to tissues by bleeding and oedema and sets the stage for optimal recovery of tissues through the natural healing processes.

Anti-inflammatory medication is useful at this stage and, of course, a correct diagnosis must be made at this stage of management to direct the necessary steps in rehabilitation that follow.

Chronic injury needs management in several ways

Perhaps the most important difference in management of chronic injuries from acute injuries is the use of heat rather than cold. Heat is produced by the various electrotherapy modalities used by physiotherapists. These modalities include ultrasound therapy, short wave diathermy, microwave therapy and hot packs. Heat applications are used for approximately 15 minutes every hour and often precede specific management such as massage, stretches and strength training.

Physiological heat retainers are important at this stage of management. With the concept in mind of improving blood flow through an injured area, heat retainers have an important place in maximizing the effects of heat on the injured soft tissues.

Physiological heat retainers must be worn for as long as possible (day and night) and should be worn until such time as recovery has been seen to be complete. In some cases the recovery process may take 6-12 months and it is not uncommon for an athlete to require a heat retainer for this period of time.

Patients must be counseled on the wearing of heat retainers so they understand that these applications are not being used for stability of a joint or for defense against acute trauma (such as a twisted knee, etc.), rather these appliances are very useful in providing warmth, compression and, to a degree, some assistance in proprioception (which implies perception of body position).

Indications for use of heat retainers

There are a variety of conditions in sports medicine for which heat retainers are an important adjunct of therapy.

Such conditions include hamstring muscle strains, patellar tendinopathy, groin pain syndromes, back pain syndromes, and the range of overuse syndromes of the wrist and elbow (including tenosynovitis and tennis elbow).

Whilst all these conditions will not be cured by the wearing of a heat retainer, there is no doubt that there is good symptomatic relief and, through this, the ability to undertake more training and facilitate recovery.