Cold water immersion reduces muscle growth during resistance training Original paper

In this meta-analysis of randomized controlled studies, cold water immersion after resistance exercise reduced gains in muscle size compared to resistance training without cold water immersion, though the effects appeared small in magnitude.

The effects of postexercise cold water immersion on gains in muscle size (hypertrophy) during resistance training.

A total of 116 participants (average age of 20–26; only 2 women).

Researchers conducted a meta-analysis of 8 randomized controlled studies.

The studies were 4–12 weeks in duration, and resistance exercise was performed 2–3 times per week: 2 studies used handgrip training, 1 study focused on wrist flexor training, 3 studies used lower-body training, and 2 studies used full-body training programs.

All of the studies used postexercise cold water immersion. Three studies exposed only the upper limbs, two studies exposed only the lower limbs, and three studies employed whole-body cold water immersion. Cold water immersion was applied for 10–20 minutes at a water temperature of 10–15℃ (50–59℉). The participants began cold water immersion between 3 and 15 minutes after finishing the exercise session.

Muscle size was assessed using a variety of techniques, including DEXA, ultrasound/magnetic resonance imaging of various different muscle groups, muscle biopsy, and the circumference of the arms and legs.

Analyses were conducted to determine the influence of intervention duration (i.e., less than 8 weeks or 8 weeks or more), training status (i.e., trained or untrained), and training frequency (i.e., two or three days per week) on the outcome.

Compared to resistance training alone, resistance training combined with cold water immersion led to less hypertrophy with a small effect size.

Intervention duration, the training status of the participants, and the training frequency didn’t appear to influence the results.

Traditionally, cold water immersion has been a tool used by athletes to enhance their recovery from exercise and improve their performance in subsequent exercise sessions or during a competition. When recovering as quickly as possible is the goal, cold temperatures seem to help because cold water immersion seems to improve exercise recovery over a few hours.^[1]

There are a few mechanisms that may explain this benefit. For one, cold water immersion reduces central nervous system (CNS) fatigue by reducing core body temperature and enhancing brain blood flow and oxygenation.

Cold water immersion also reduces cardiovascular strain. When body temperature rises, blood flow is redirected from the active muscles and the core to the skin in order to dissipate heat. This reduces blood flow and oxygen delivery to muscles, increases heart rate, and may impair performance. Cold water immersion redirects blood flow to the central circulation because less of it is going to the skin to facilitate cooling.

It’s also been suggested that cold water immersion can result in an increased clearance of exercise-associated metabolites. Cold water immersion may accelerate the removal of potassium, chloride, blood lactate, and other blood metabolites, though there’s little evidence to support this mechanism.

Finally, cold water immersion may improve autonomic nervous system recovery by inhibiting sympathetic and activating parasympathetic activity.

Regular cold water immersion during exercise training may also enhance longer-term recovery via autonomic nervous system regulation and a reduction in subjective markers of exercise-induced muscle damage, like perceived pain and the sensation of delayed-onset muscle soreness (DOMS), as well as objective markers, like inflammation and swelling.

A recent meta-analysis on the subject of cold water immersion and exercise recovery noted that cold water immersion improves endurance recovery from endurance exercise by reducing cardiovascular and thermal strain, decreasing perceived fatigue, and lowering levels of perceived soreness. It’s most effective within 1 hour of exercise and when the initial bout of endurance exercise was performed in the heat. Endurance recovery was determined by measuring enhanced performance during a second session of endurance exercise performed on the same day.^[2]

Cold water immersion also improves the recovery of muscle strength and power by reducing the extent of muscle damage, decreasing muscle soreness, and enhancing perceived recovery; it’s effective at approximately 24–48 hours after exercise.^[2]

In another meta-analysis, covered in this Examine Study Summary, cold water immersion reduced DOMS at 0–24 hours after exercise, reduced ratings of perceived exertion and improved countermovement jump immediately after exercise, and decreased levels of creatine kinase and lactate at 24–48 hours after exercise.

Cold water immersion and exercise recovery

Despite some of these well-known benefits for acute and chronic recovery, recent data on cold water immersion’s effects on training adaptations have ignited controversy. Could there be a downside to jumping into cold water after a workout?

If the only concern is improving endurance, maybe not. A meta-analysis published in 2021 found that regularly using cold water immersion had no effect on measures of aerobic exercise performance, including average power output, maximal aerobic power during a graded exercise test, or time-trial performance.^[3]

However, if muscle gains are the goal, then the cold might be detrimental. A meta-analysis of 10 randomized controlled trials, including mostly male participants published in 2022, concluded that postexercise cold water immersion attenuated gains in muscle strength. However, this effect was only observed when the trained limb was immersed, but not when whole-body cold water immersion was used.^[4]

The summarized study adds to the literature by suggesting that cold water immersion impairs gain in muscle size in addition to muscle strength. However, it should be noted that cold water immersion doesn’t eliminate the benefits of resistance training, but only diminishes them when compared to a condition in which only resistance exercise is performed.

Athletes should use caution if they’re considering regular use of cold water immersion around resistance training sessions. The use of cold water immersion should be balanced with the primary goals of the exercise, weighed against the benefits and risks associated with using the cold. Because most studies used cold water immersion immediately after exercise, several of the negative effects can be sidestepped by avoiding the use of cold in close proximity to resistance exercise. Timing matters. As a best practice, cold can be used to reduce fatigue and soreness as necessary, ideally at least a few hours after exercise.

This way, athletes can take advantage of the recovery benefits without worrying that they’re impairing muscle growth and strength.

A tool developed by the authors to rate the quality of resistance training studies concluded that none of the studies were “good” quality — 3 were “fair” quality, and 5 were “poor” quality. Thus, more research is needed on the effects of cold water immersion during resistance training before any strong conclusions about its harms or benefits can be drawn.