Ice baths: “lab fatigue” vs. “real fatigue”
Ice baths after a hard workout are very popular, but the evidence for them has always been a little shaky. A group of British researchers (including a pair from the English Institute of Sport) have just published a major meta-analysis in the British Journal of Sports Medicine that adds a couple of interesting insights. The analysis covers 14 different studies with a total of 239 athletes.
What I found most interesting is the following distinction they decided to make:
For the purpose of this review, exercise will be subdivided into two categories: ‘eccentric exercise’ that refers to the stress caused from exercise incorporating high mechanical stress (eg, eccentric contractions) and ‘high-intensity exercise’ that refers to stress caused from exercise with a high metabolic cost as well as some elements of eccentric muscle contractions (eg, repeat sprint sports).
It’s well known that the best way to induce muscle soreness is with eccentric muscle contractions, particularly unfamiliar ones. So most lab experiments on muscle soreness involve simple things like lowering a dumbbell or stepping off a box over and over — it may not be exhausting, but it sure leaves you sore. The problem is, this isn’t the kind of damage that most athletes are interested in recovering from — they’re interested in recovering from training sessions that feature familiar but intense exercise.
So is there a difference between the two? Yes: the meta-analysis found dramatically stronger effect on recovery from “high intensity exercise” than from “eccentric exercise.” It’s worth noting that only two studies looked at the former, while 12 looked at the latter. Still, it offers a possible explanation for why so many athletes believe ice baths help them in training, while lab studies of eccentric exercise continue to find ambiguous results.
Speaking of results, what were the overall conclusions? I quite like the use of forest plots to give a quick visual sense of the overall data. Here are the results for perceived recovery from muscle soreness, with each dot representing a study result (some studies appear more than once for results at 24, 48, and 72 hours after exercise, which is why there are more than 14 dots). Dots to the right of the thick line mean that the ice bath group recovered more quickly; dots to the left of the line indicate that the control group recovered more quickly:
Looks pretty convincing, eh? Unfortunately, the picture is a bit muddier if you look at an objective measure like creatine kinase in the blood (a marker of muscle damage), though there’s still a statistically significant effect in favour of ice baths:
Same goes for recovery of strength:
In the end, we’re still plagued by the fact that it’s impossible to placebo-control an ice bath study. The perceived soreness results do look encouraging, but it’s hard to rule out the effects of the fact that most of the subjects probably expected to feel better when they had the ice bath. By no means is the science settled here yet.
Which brings us to another point that’s currently being hotly debated in scientific and athlete circles (as commenter Rich pointed out last time I blogged about ice baths): If inflammation is part of the body’s adaption response to stress, and ice baths reduce inflammation, does that mean ice baths reduce your adaption to hard training? Interestingly, the lead author of the current study, Jonathan Leeder of the English Institute of Sport, commented on this question in an EIS press release last year:
“There’s evidence to suggest that if you constantly decrease the stress in training that the body won’t adapt, so long term use of a recovery technique, such as an ice bath, should be reviewed to avoid any detrimental effects on performance and to ensure that these techniques have their biggest impact when needed during competition” [Leeder] adds.
But is there really evidence to back this hypothesis up? Here’s what Leeder and his co-authors say in the peer-reviewed BJSM:
It has, however, been suggested that the inflammatory response is critical for optimal repair of damaged tissue. Although the mechanisms of training adaptation are not fully understood, it may be detrimental to reduce the commonly accepted damage-repair-adaptation model by diminishing the inflammatory response; however, there is a lack of evidence to support this. This raises the question of whether frequent or habitual use of strategies designed to reduce inflammatory responses can be detrimental for elite athlete adaptation to training.
So that’s where we’re at: no one really knows whether repeated ice baths have a practically significant effect on reducing adaption to training. From what I understand, the English Institute of Sport has been advising its athletes to avoid ice baths after routine sessions during heavy training phases, but to incorporate them during tapering and competition. In other words, periodize your recovery protocols so that you maximize adaption during training periods and maximize recovery during competition periods. Does this work? Maybe we’ll find out at next year’s Olympics!