Analyzing the Meta-Analysis
So what was found in this survey? Some key findings to note:- Twenty-one studies with 216 subjects were studied in total. Fourteen of these studies were published in the past two years (since 2011) and had not been included in any previous review. This certainly shows the validity of the topic.
- Overall benefits were very small. There was a documented 2.4-percent overall improvement across all studies, but many of the analyses cross the "zero" line and suggest that there may have been no practical benefit.
- Explosive exercise such as sprinting seems to have the most potential for benefit, with endurance exercise (e.g. cycling) slightly less to no benefit found across studies.
- Actual cold-water immersion, with water temperatures 12 to 15 degrees Celsius, showed more potential benefit than cold packs (e.g. icing). Furthermore, the studies showed that full-body immersion up to the chest is preferred over leg immersion only.
- CWI only had minimal benefit with short recovery bouts of 2 to 3 hours between exercise. The effect sizes became larger after 24 hours, and larger still at up to 96 hours. The caveat is that there are fewer studies that use such long periods between exercise, so one outlier study can really skew the analysis.
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Summary
In my view, meta-analyses are definitely the wave of the present and future when it comes to comprehensively surveying of literature. I've started down this road myself, as I published a meta-analysis on the effects of exercise and training on glucose control in Type 1 Diabetics (Tonoli et al. 2012) and have another upcoming on whether pre-cooling or cooling during exercise is an effective ergogenic aid in the heat (British Journal of Sports Medicine).What I take away from the Poppendieck et al. (Poppendieck et al. 2013) meta-analysis is that CWI, if done with the above guidelines for temperature and depth of exposure, MAY have the potential for slightly improving recovery and subsequent performance. In a worst-case scenario, CWI doesn't appear to harm endurance exercise performance, so it is a good candidate for those with a "marginal gains" philosophy.
For the rest of us, CWI might remain of interest but only after a very, very heavy day or block of training. It is likely that we can get the same or greater recovery benefits by focusing on other easy-to-do post-ride recovery options like nutrition and getting adequate sleep.
Ride fast and have fun!
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