Over the last few years, there's been a big debate about whether it's possible to have "too much" recovery. As Shona Halson and her colleagues at the Australian Institute of Sport explain in a new study of ice baths:
Training theory suggests that fatigue and/or inflammation post exercise is necessary to promote long-term adaptations to training and subsequent improvements in performance. Based on the improvements in performance observed in acute cold water immersion studies, two adaptation theories have been proposed. The first is that hydrotherapy allows athletes to perform subsequent training sessions with a greater training load or quality, thus resulting in an enhanced stimulus for adaptation. Conversely, the second theory suggests that cold water immersion may decrease adaptations to training due to minimization of fatigue and inflammation occurring following training.
In other words, recovery techniques like ice baths may help you feel better tomorrow, but make you less fit in the long run if they get rid of the inflammation that signals your body to adapt and get stronger after training.
This is an interesting theoretical debate. But the even more interesting question is: does it matter in real life? Of the two possibilities suggested by Halson (ice baths allow you to train harder; ice baths reduce your adaptation to training), which one wins out? To answer that question, Halson and her colleagues understook a truly Herculean study, whose results have just been published in Medicine & Science in Sports & Exercise.
The details: they had 21 national-level cyclists live on-site at the Australian Institute of Sport for a 39-day study period that aimed to simulate conditions in a Grand Tour. They all trained together, doing one week of baseline training, three weeks of very intense training, then 11 days of taper. The cycling was mostly on the roads, but included a series of performance tests in the lab each week, with high-intensity intervals, repeated four-minute trials, and a ten-minute time trial. The cyclists were randomized into two groups based on maximal aerobic power and (this is a great detail) belief on a scale of 0 to 100 about whether the ice baths would help or hurt their training. The ice bath group took ice baths four times a week for 15 minutes at 15 degrees C, immersed up to the neck. Another interesting detail: they weren't allowed to shower immediately after the ice bath, to avoid warming up right away.
Here's a sample graph of one of the results, showing average power in two 4-minute time trials with 42 minutes rest between them:
The filled squares are the ice bath group, and the open circles are the control. The five time points correspond to the baseline week, three intense training weeks, then the taper. (The data points on the far left show the overall average for each group during the study.) You can see that the ice bath group is ahead right from the end of the first week, climbs at roughly the same rate, and then seems to pull ahead further in the taper. Several (but not all) of the performance measures show similar patterns, with a "likely beneficial" edge of a few percent for the ice bath group. The overall conclusion is that the effects of ice bath on performance were "unclear" – but one thing they definitely didn't find was any evidence of the cyclists in the ice bath group not improving as much as the control group.
So where does this leave us? There are still plenty of question you can ask. Does it matter that the experiment was unblinded? They tried to counter those effects by balancing the randomization based on who believed most strongly in ice baths, but perhaps more importantly from a practical perpsective, athletes aren't blinded in the real life either. Was three weeks long enough for any potential adverse effects to accumulate? That's trickier – I don't know the answer.
Probably the most powerful conclusion from this study is that it puts an upper bound on the size of the effect in either direction. Whatever negative effects there might be, they're too small to detect in this setting. And conversely, whatever positive effects ice baths might have, they're barely enough to move the needle in this context. Of course, the challenge in elite sport is that minuscule differences – effects that are impossibly small to measure – may end up being the difference between victory and defeat. But studies like this help to keep the relative importance of these small gains in context. They only matter after you've taken care of the first 99.9% perfectly.