Cold water immersion therapy is growing in popularity, spurred on by the charisma of eccentric personalities like Wim ‘The Iceman’ Hof and by an ever-expanding body of scientific data. However, though its effects are beginning to be objectively measured, many people still wonder what it could do for them- does it really work, what is it for, and is it appropriate for their circumstances? The full physiological- and psychological- effects of cold water immersion therapy are still being explored and much more scientific data is needed before definitive answers can be given. However, we can knit together the data and theory we have so far along with testimonials from both long-term practitioners and newer converts to get an idea of what goes on when somebody involves themselves with cold water immersion. In so doing, we can see, among other things, the incredible benefits afforded by cold water immersion with regards physical recovery.
Cold water immersion and physical recovery
Whilst further research is needed, and the chronic effects of cold water immersion are still not fully understood, the diminution of inflammatory pathways and the hydrostatic effects of water immersion both represent avenues of interest when looking at the positive effects of cold water therapy for physical recovery. This could be recovery from injury or from the trauma of hard exercise: in each case, the benefits stand. In fact, cold water immersion therapy (and water immersion more broadly, in reference to all forms of water-based recovery) has become a popular recovery method amongst trainers, athletes and sports scientists for its ability to improve recovery time after and reduce the delayed onset of muscle soreness (DOMS) after hard exercise. Depending on the intensity of training, exercise can cause various degrees of fatigue to the musculoskeletal, nervous, and metabolic systems. This kind of muscular trauma also comes hand in hand with necessary microscopic tears in muscle tissue (commonly known as exercise-induced muscle damage, or EIMD), which is believed to be one of the main causes of DOMS. As a recovery method for muscular and soft tissue trauma, such as incidents of DOMS, sprains, strains and inflamed tissue, cold water immersion is notable for its ability to:
- Reduce oedemas
- Decrease the perception of pain associated with muscular soreness
- Decrease the perception of fatigue
- Alter localised blood flow
- Alter localised tissue and core temperature
- Alter heart rate
- Reduce muscle spasms
- Reduce tissue inflammation
- Reduce muscle damage
- Improve range of motion
How does cold water immersion improve recovery?
There are several factors underpinning the measurement of cold water immersion’s effectiveness, including:
- Subjective measures and testimonial
- Ratings of perceived exertion (RPE)
- Objective measures, like:
- Creatine-kinase (CK)
- Blood lactate-levels
- C-reactive protein (CRP)
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.
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.