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  1. Ratings of perceived exertion (RPE)
  2. Objective measures, like:
  • Creatine-kinase (CK)
  • Blood lactate-levels
  • Interleukines
  • C-reactive protein (CRP)

Cold water immersion therapy has been shown to reduce the effects of DOMS and RPE. In fact, a recent meta-analysis of current scientific data concluded that it is an effective protocol for reducing the effects of DOMS 24 hours, 48 hours, and 96 hours after training, as well as reducing symptoms of RPE 24 hours after exercise. These results are also supported by an extensive review conducted in 2012. It must be noted that measures such as DOMS and RPE are subjective- they are measured based on a client’s perceptions and feedback, as are any changes and improvements. There is less data supporting cold water immersion’s effectiveness on more objective measures. However, there are several strong current theories as to how cold water immersion aids recovery as accounted for by objective measures, including:

1. Vasoconstriction

Immersion in cold water is thought to cause vasoconstriction- the constriction of the blood vessels. This would lead to lower localised blood pressure. The sudden onset of colder temperatures would activate the nociceptors- thermal nerve cells- leading to a change in sympathetic nerve activity, which would be responsible for decreased blood flow. This reduction in blood flow would be important around tissue damaged by hard exercise as it could reduce inflammation and oedemas.

2. Analgesic effects of the cold water

Another possible explanation revolves around analgesia (pain relief). The cold water has an analgesic effect on the participant by leading to decreased nerve conduction speeds and excitability. This reduces nociceptor communication with the sympathetic nervous system, leading to a reduction in pain perception.

3. Reducing inflammatory pathways

The tackling of inflammation is central to cold water immersion therapy’s efficacy. It may be a key reason that cold water immersion is so effective in aiding recovery from injury, as the decrease in the perception of pain is related to reduced inflammatory pathways. This means reduced nociceptor sensitisation, reduced exercise-induced oedema, and reduced white blood cell access, thus citing a combination of effects all revolving around the single root cause.

4. Hydrostatic pressure

Hydrostatic pressure may also play a part. When a participant is immersed into water, they are subject to the effects of hydrostatic pressure. For every 1-metre of immersion, the pressure gradient rises by 74mm Hg (mm Hg = millimetres of mercury), which is almost equal to typical diastolic blood pressure. This increase in hydrostatic pressure causes an inward and upward squeezing action on the body. In essence, this is the mechanism behind buoyancy. Buoyancy reduces the gravitational load placed on the body, which is why the body weighs less when in water. During immersion up to hip level, as is common with immersion therapy, hydrostatic pressure causes the displacement of fluids from the body’s lower extremities towards the thoracic region. The theory runs that this may be the principal component for enhanced recovery: it may reduce exercise-induced oedemas, increase the transfer of extracellular fluid into the bloodstream and increase cardiac output. Increasing cardiac output will additionally mean increased blood flow and metabolism of waste products that accumulate during exercise.

Placebo effect

It’s quite common to dismiss placebo effects as being ‘just your imagination’. Whilst this may be true, it’s also simplistic and perhaps unnecessarily pejorative. If pain and fatigue perception both decrease, this is by-and-large a positive. We need to bear in mind a placebo effect alongside the above theories for cold water immersion therapy’s efficacy. Psychology is powerful: a participant may simply feel more ‘awake’ during and immediately after the immersion into the cold water. This will cause a decrease in their sensitivity to pain. Whatever reason, or mixture of reasons, may lay behind the efficacy of cold water immersion therapy for improved recovery after injury and hard exercise, there is little doubt in practitioners’ minds that there are benefits. They feel fitter and better, with decreased pain and fatigue levels, for taking part in cold water immersion.