Summer’s hottest days have arrived and with that, many folks are interested in exercising to show off their newly fit summer physiques. Across social media, fitness influencers share new workout routines and diets with the goal of encouraging folks to live healthier lifestyles. Recently, many fitness influencers have started to promote the ice bath as a post-workout cure for muscle fatigue. But do ice baths actually help athletic recovery?
Cold therapy isn’t exactly a new concept or revolutionary idea. In fact, the 3rd U.S. President, Thomas Jefferson, was alleged to have taken cold baths daily to “maintain his good health” [1]. When one exercises, the working muscles experience stress and tissue damage, which when repaired typically grow larger, stronger, and more resistant to the same stresses it was previously under.
As indicated by the figure above, Kwiecien et al. eloquently illustrate the general effects of exercise on muscles. Increased metabolic stress (nutrient depletions) and temperature following mechanical stress (exercise) can lead to structural damage within the muscle cells themselves. The idealized benefits of cold therapy are to reduce the damage that the muscles have undergone and expedite recovery by reducing muscle temperature [2].
Yet another main potential role of cold therapy is to reduce pain in the muscles after damage sustained while training and reducing inflammation, theoretically speeding up recovery. One major pitfall of this line of literature is that this has not yet been concretely proven in human models. Dr. Tracy Zaslow, a primary care/sports medicine physician, was quoted “There are a lot of hypotheses, as opposed to data” when discussing the residency of ice baths in exercise recovery [3]. Further evidenced in a 2012 article published in the British Journal of Sports Medicine, cold therapy showed evidence of aiding in muscle injury recovery in animal models, but was not sufficiently proven in humans [4]. This isn’t to say that all cold therapy research is entirely unfounded. As is often the case in scientific research, evidence cannot be extrapolated from animal models to humans one-to-one and as such necessitates further research in the appropriate subject, in this case, humans.
Studies looking into cold water immersion, or ice baths, have been hot and cold when it comes to reaching a conclusion. In a 2021 review article published in the European Journal of Applied Physiology, the authors note that numerous studies evaluating cold water immersion and exercise recovery have not provided unified evidence tipping the balance in favor of ice baths being beneficial or detrimental [2]. Referenced in this review, a 2017 study on cold water immersion plotted the potential beneficial and detrimental effects of ice baths on the human body [1]. Below, is a summarized, bulleted list of some of these proposed benefits.
Decreased muscle tissue temperature => stress hormone release => decreased inflammation
Decreased muscle tissue temperature => less blood flow surrounding muscle => decreased swelling
Increased fluid pressure in muscles => increased removal of waste products
Once plunged into the frigid water, the muscle tissues will begin to cool, eliciting a cold shock response in which cortisol, a “stress” hormone, is released, subsequently providing an anti-inflammatory effect. Additionally, the researchers suggest that the decreased tissue temperature will decrease the muscle’s blood perfusion or blood supply, reducing the edema, or swelling. This on the surface sounds beneficial, though the concern with decreased perfusion could be that there could be insufficient nutrient delivery to the repairing muscle cells, ironically slowing recovery. Cold water immersion could similarly be considered a positive if the hydrostatic or fluid pressure within the damaged muscle cells increases, potentially coinciding with waste products from damage/repair being expeditiously removed from the muscle.
Before a final verdict is delivered on the multiple good things that may come from taking an ice bath after exercise, it’s critical to understand that it should not be done without addressing the potential risks. The detrimental effects of cold water immersion are represented in the bulleted list below.
Detection of cold temperatures => fight or flight response => increased risk of dangerous heart abnormalities
Detection of cold temperatures => increased blood pressure => ruptured blood vessels in the brain
Detection of cold temperatures => hyperventilation => risk of potentially fatal heart rhythm
As Tipton et al. demonstrates, cold water immersion stimulates heat receptors in the skin, called thermoreceptors, acting as a signal to the rest of the body that “Hey, it just got REALLY cold.” Once that signaling pathway has been activated, a couple of outcomes can occur: sympathetic nervous system response and gasp reflexes. The sympathetic nervous system response, more commonly known as the fight or flight response, alerts the body in times of danger or stress so that the body can allocate resources where needed for survival. By artificially doing so with cold water immersion, the body may be at an increased risk for cardiovascular abnormalities like tachycardia (increased heart rate) and arrhythmias (abnormal heart rhythms). If a person jumps in an ice bath and a blood vessel ruptures due to increased blood pressure (thank you, sympathetic nervous system), that person could then be at risk of a potentially fatal ruptured blood vessel in the brain called a hemorrhagic stroke. In the gasp reflex following immersion, the person may find themselves hyperventilating or struggling to breathe. If hyperventilation continues, the person will have too little carbon dioxide in the blood, eventually leading to potentially fatal ventricular fibrillation, or when the lower heart chambers begin to flutter uncontrollably.
Are all these catastrophic things likely to happen? Probably not. Are there potential benefits to plunging into cold water for a minute after a workout? Maybe. The simple answer is that more research needs to be conducted. If you are interested in trying cold water immersion for exercise recovery, it would be wise to consult a healthcare professional to ensure you are not at outrageous risk following the plunge. Stay cool this summer!
Written by Tim McGinley, BS and edited by Aldrin V. Gomes, PhD
References
Tipton, M.J., Collier, N., Massey, H., Corbett, J. and Harper, M. (2017), Cold water immersion: kill or cure? Exp Physiol, 102: 1335-1355.
Kwiecien, S.Y., McHugh, M.P. The cold truth: the role of cryotherapy in the treatment of injury and recovery from exercise. Eur J Appl Physiol 121, 2125–2142 (2021).
Fields, L. (2022, July 20). Taking the plunge: Is cold exposure worthwhile? Cedars-Sinai.
Bleakley CM, Glasgow P, Webb MJ. Cooling an acute muscle injury: can basic scientific theory translate into the clinical setting? British Journal of Sports Medicine 2012;46:296-298.