The Effects of Cold-Water Immersion on Muscle Growth

The athletic population utilizes a variety of strategies to attenuate the fatigue and discomfort of resistance training or physical competition, or to potentially improve performance-defined measures of recovery.  Strategies utilizing extreme temperatures such as sauna, cold, hot water immersion, cryotherapy, etc. have demonstrated efficacy in reducing the severity of muscle soreness, perceived fatigue, and time to recovery. 

The evidence on the benefits of cold-water immersion is mixed with some studies showing a benefit and some showing no improvements.

The acute use of cold water immersion seems to improve exercise performance⁽¹⁾ but there is no evidence on the chronic adaptions to resistance training, especially muscle hypertrophy.  A systematic review and meta-analysis was conducted of all existing data on the effects of post-exercise cooling together with resistance training on gains in measures of muscle growth.

Major findings

The evidence available to date indicates that cold water immersion likely attenuates muscle growth adaptations compared to resistance training alone.

This finding is consistent with acute study results demonstrating that cold water immersion blunts the anabolic response to resistance training.

For example, research shows that cold water immersion reduced muscle protein synthesis rates for up to 5 hours post-application. In addition, cold water immersion impaired muscle protein synthesis rates during prolonged resistance training⁽²⁾ (see figure 1 below)

Figure 1: Myofibrillar protein FSRs was significantly lower in the cold-water immersion compared to the control leg during 5 h of postexercise recovery with the ingestion of 20 g of intrinsically labelled milk protein with 45 g of carbohydrate in healthy young men⁽²⁾

It’s plausible that cold water immersion attenuates activation of transcription factors involved in ribosome biogenesis and suppresses satellite cell activity⁽³⁾, both of which are alleged to be crucial mediators of muscle growth⁽⁴⁾.  

These alterations persisted for up to 48 hours post-cold-water immersion, suggesting a prolonged negative effect.

Potential Physiological Mechanisms

A hypothesis is that cold water immersion alters the acute inflammatory response to resistance training, which has been implicated in the kinase domain of titan hypertrophy.

A reduced inflammatory response to resistance training could conceivably attenuate reactive oxygen species production and associated activation of the mitogen-activated protein kinase pathway, effectively downregulating muscle protein synthesis and potential anabolism.

It is also possible that cold water immersion negatively affects anabolism by reducing post-exercise blood flow to the muscles.  This should not be overlooked given the established link between blood flow and nutrient-dependent skeletal muscle proteolysis and muscle protein synthesis regulator effects of insulin⁽⁵⁾.

While the post resistance training anabolic window for muscle growth associated with muscle protein synthesis may not be as narrow as one thought, an acute decline in nutrient delivery and an extended period of muscle protein catabolism and diminished maximal muscle protein synthesis capacity via cold water immersion blood flow impairment is conceivable.

These findings may contribute to an acute mechanistic understanding of the attenuated skeletal muscle growth; however, it should be noted that we cannot extrapolate acute responses of resistance training to chronic mechanisms of hypertrophic adaptations.

Study Limitations

There are a few limitations of this analysis that should be acknowledged when attempting to draw evidence-based conclusions:

• - Most of the research included in this review was of relatively short duration (4-8 weeks). Although evidence shows that the combination of cold-water immersion and resistance training modestly impairs muscle growth, it is not clear if the comparison between groups would vary over longer time periods.
• - There were many different modalities utilized to measure changes in muscle size (i.e., biopsy, DXA, circumference, ultrasound, and MRI). Direct imaging seems to be the most accurate measure and is recommended to be utilized in future research. One important note is the fact that a variety of modalities indicate cold water immersion impairs muscle growth and seems to strengthen the confidence of these findings.
• - The resistance training protocols varied greatly between studies, including weekly training volume, frequency, and proximity to failure.
• - Most studies did not track nutritional intake across the respective study periods.  It is well known that both total protein and daily energy intake influence the hypertrophic response to resistance training.  Future research should seek to account for dietary intake to ensure this variable does not confound results.
• - All the included studies conducted cold water immersion following every resistance training session utilizing a similar approach of 10-20 minutes at 10-15°C.
• - There may be alternative approaches to cold water immersion application that might yield different results and future research should attempt to standardize this.
• - These results are specific to cold water immersion and cannot be extrapolated to other cold application strategies such as cryotherapy, which warrant further investigation as to their chronic effects on muscular adaptations.
• - Most of the research to date was conducted on young men. These findings cannot necessarily be generalized to other populations such as females and older adults. 

Summary

The current evidence indicates that the application of cold-water immersion immediately following resistance training sessions may modestly attenuate gains in muscle hypertrophy.

Based on the evidence to date, individuals seeking to maximize muscle growth should avoid using cold water immersion immediately following bouts of resistance training and further consider the frequency and timing of application.

These findings may have practical implications to athletes looking to limit resistance training induced gains in muscle mass (e.g. distance runners). More research is needed to ascertain the effects of different frequencies and timing strategies of cold-water immersion on resistance training induced muscular adaptations.

You can learn more about the health benefits of cold water immersion here!

References:
    1.    Versey NG, Halson SL, Dawson BT: Water immersion recovery for athletes: effect on exercise performance and practical recommendations. Sports Med 43:1101-30, 2013
    2.    Fuchs CJ, Kouw IWK, Churchward-Venne TA, et al: Postexercise cooling impairs muscle protein synthesis rates in recreational athletes. J Physiol 598:755-772, 2020
    3.    Roberts LA, Raastad T, Markworth JF, et al: Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training. J Physiol 593:4285-301, 2015
    4.    Brook MS, Wilkinson DJ, Smith K, et al: It's not just about protein turnover: the role of ribosomal biogenesis and satellite cells in the regulation of skeletal muscle hypertrophy. Eur J Sport Sci 19:952-963, 2019
    5.    Timmerman KL, Lee JL, Dreyer HC, et al: Insulin stimulates human skeletal muscle protein synthesis via an indirect mechanism involving endothelial-dependent vasodilation and mammalian target of rapamycin complex 1 signaling. J Clin Endocrinol Metab 95:3848-57, 2010