The utilization of cold temperatures whether in the form of air temperature, water immersion, or ice baths after exercise is not new, but participation in this intervention is on the rise. As the popularity of cold water immersion increases it continues to outpace the available research supporting its’ utilization. Overall the research has significant methodological weaknesses including small sample sizes, lack of randomization, and most importantly significant differences in cold water protocols. This makes it very difficulty to compare one study to another or draw conclusions on the already limited literature on the topic. Previous authors have reported consistent, cold water immersion after strength training reduces long term gains in both strength and hypertrophy (Peake et al. J Physiol. 2020). The reasons for this attenuation in our muscles is multifactorial involving multiple circulatory, cellular, and neurological pathways. A recent article highlights some of the molecular factors influencing why cold water immersion after intense exercise may attenuate gains in strength and muscle hypertrophy.
Peake and colleagues studied the effects of cold water immersion after strength training (Frontiers. 2020). Authors used a small sample of 9 young, trained men (average age 22) with at least 1 year of strength training experience. They used a randomized, cross over design with 2 intervention days for each participant. Each participant completed a series of lower quarter exercises including leg press, single leg squat, knee extensions, and a walking lunge. They performed these exercises while supervised at 3 sets of each exercise at a 8, 10, and then 12 repetition maximum. Participants were then randomized, before the cross over, to either 10 minutes of low intensity cycling exercise or 10 minutes of cold immersion. Water in the bath was 10 degrees celsius and continuously circulated. After the bath, participants were not allowed to use a warm shower or bath for at least 2 hours.
After both interventions participants under a muscular biopsy of their quadricep at 2, 24, and 48 hours to determine molecular and genetic pathways at play. The authors found no differences in myogenesis, proteolysis, or remodelling markers between groups. Authors believe cold water immersion may reduce muscle strength and hypertrophy by suppressing the effects of genes and proteins using other pathways not found in this study. Reductions in muscle strength and hypertrophy found with with cooling after training are likely due to negative changes in protein synthesis.