“I don’t like Cricket, oh no, I…” used it to inspire this blog!

When it comes to television and radio, in my house there’s one rule – if it’s sports related then it can stay on. If not, then strict(ish) time limits are enforced.

This applies to all sport, even less enamoured ones including the recent 5^th Investec Test taking place at The Oval. Test Match Special (TMS), interspersed with classic Boycott/Agnew quotes, was a constant stream of cricketing action over the weekend.

Boycott never fails to bring a chuckle, either from his own disputations or when he is the butt of the joke. As was the case with Geoffrey the pigeon, a lowly Columbidae named so and described by Agnew as “one grumpy-looking Pigeon who’s always by himself” (15:03). Had me chuckling.

Another interesting and topical talking point was Simon Mann’s (or maybe it was Michael Vaughan’s) commentary on a new study claiming a well known practice familiar to many athletes and sportspersons was probably a waste of time.

The practice in question? Ice baths, or cold-water immersion (CWI) to give its more scientific term. The practice of dunking your legs, or in some cases the whole body, into an icy (4C – 15C – the ambiguity here is discussed later) bath is the sports medicine equivalent of loom-bands – everyone’s doing it!

And don’t think it’s just a case of whacking a load of ice into the hot (or in this case cold) tub! A precision science (and big business) it would appear.

So what’s the deal? It’s all about recovery. More specifically, speeding up the recovery of muscles following exercise. High intensity, particularly unaccustomed exercise is associated with microscopic tears in muscle tissue, known as exercise induced muscle damage (EIMD). This often leads to soreness that peaks between 24 to 72 hours after the exercise, a phenomenon known as delayed onset muscle soreness (DOMS).

For the extreme athlete, DOMS is as much a part of daily life as a 6% carbohydrate solution, 5am wake up calls and waxing! The added scourge of EIMD includes increased stiffness, swelling, decreased strength and power and altered proprioception.1,2 Left alone, EIMD and DOMS usually resolve clinically after four to five days and athletes can return to pre-EIMD training levels.

And here in belies the plight of physios, coaches and athletes alike. Anything less than 100% can be the difference between a performance nonpareil or a seasons work undone.

In most sporting events (think Tour de France, Wimbledon [Murray on a good run], Test Match Cricket [ok, so I’m talking key fast bowlers and batsmen not out for <10 runs over two innings!]), a 5-day wait for a full force flexion of the rectus femoris is 3 to 4 days too long.

Strategies to help reduce the effects of DOMS and allow a hastier return to full training or competition are like catnip to the high level sports arena. Massage, nutritional supplements and anti-inflammatory medications have all made the list, ice baths being the latest panacea.

The problem with all these strategies is that the evidence underpinning them is not very good. Here I will focus on ice baths as brought to my attention on TMS. Interested readers I can recommend Paul Ingraham’s latest piece which does as good a job as any in describing proposed mechanisms and the evidence underpinning suggested treatments for DOMS.

So how do ice baths help boost the body’s recovery processes? It helps to think along the lines of the sports injury mantra ‘RICE’ (Rest, Ice, Compression, Elevation).

After sustaining a strain (of muscle or tendon) or sprain (of ligament) the modus operandi is RICE therapy. By no means an exact science, rest is required to reduce the metabolic demands of the injured tissue and avoid increased blood flow. Ice is used for cooling (I know, sorry).

More specifically, ice reduces the temperature of the injured tissue(s) inducing vasoconstriction, limiting internal bleeding, potentially reducing pain, swelling and metabolites from the resulting inflammatory response.3

The proposed mechanism of ice baths is the same vasoconstriction and anti-inflammatory effect, thereby reducing the potential for DOMS. However, we don’t really know the mechanisms behind the use of cryotherapy and the evidence for the effectiveness of RICE is insufficient.

What then for the evidence for ice baths and the TMS study? After consulting Dr Google (where would we be without you?), I tracked down the article of discussion here. A study forming a Master’s thesis from the University of New Hampshire, Crystal et al. conclude, “20 min of cyrotherapy was ineffective in attenuating the strength decrement and soreness seen after muscle damaging exercise…”

Now, I can relate to this article in more ways than one. Firstly it comes from the field of sports and exercise science, one which I graduated, worked and published in for 10 years before the move to clinical science and evidence-based medicine.

Secondly it involves a protocol of downhill running to induce muscle damage and DOMS, something I have direct experience with.

Finally, it encompasses most of the problems associated with research in this scientific field for which I too was guilty as charged.

Before even turning to the methods section, I could envisage the common culprits present: small sample of self-selecting university student volunteers, no sample size justification, insufficient description of the randomisation process, lack of allocation concealment, no blinding (of assessors in this case), statistics based on undergraduate level SPSS and so on.

Unfortunately this was proven to be the case: “…Twenty recreationally active males”; “…recruited to the study via flyers around the university”; …”’randomly’ assigned”; “…and were informed of their group assignment prior to the downhill run”; “Estimates of skewness and kurtosis were used to screen for normality of data”.

And that’s before we even get to the selected cold-water immersion protocol and outcome measures. The irony is the authors highlight some of these issues as flaws with previous studies (citing at least 10) and thus prove rationale for their study.

My gnostic experiences at the Centre of Evidence Based Medicine have provided the necessary understanding of good and bad evidence, where to look for it and the skills to appraise it.

I would not be surprised if most peers in my former field had not heard of the Cochrane Collaboration, as was my experience throughout education and early years of practice. A lack of reference by Crystal et al to any systematic review on the topic does nothing to relay this fear.

It turns out there is a Cochrane systematic review by Bleakley et al. on this very topic. Published in 2012 (before the start of the study by Crystal et al.), it includes 17 randomised controlled trials totalling 366 participants with an age range 16 to 29 years. The largest study had 54 participants but 72% used 20 or less. Ten studies used untrained participants.

The exercise used to inflict EIMD varied by type, duration and intensity across studies, the most common being resistance exercise followed by running and cycling. The majority (90%) of studies were conducted under laboratory-controlled conditions. Interestingly, only 2 studies were performed in a competitive sport environment.

The most common water temperature used was between 10C and 15C (75%), one study using 5C. Ten studies used continuous immersion for 5 to 24 minutes, the average being 12.6 minutes, the remainder using intermittent immersions of two to five sets of 1 to 15 minute immersions.

Comparison groups included passive intervention (no CWI or rest), contrast immersion (alternate cold and warm-water), warm-water immersion, active recovery, compression garments and different dosages of CWI.

So what did the review find? When reported as muscle soreness, there was no significant effect of CWI when compared with passive intervention at immediate follow up but lower reported pain at all time points from 24 hours onwards (up to 96 hours). There was no effect on pain when reported as tenderness.

Subjective feelings of physical recovery and fatigue were improved immediately after CWI but not at 24 hours. There was no effect on mental recovery.

When measured in absolute terms (Nm), the decrease in strength associated with EIMD was attenuated immediately following CWI but there was no effect at 24 hours or beyond. There was no effect of CWI on strength when measured as a percentage of baseline strength.

CWI resulted in a better retention of power (measured as jumping performance) at 24 hours when measured as a percentage increment but not when measured in centimetres or as Watts on a cycle ergometer.

There was no effect of CWI on functional capacity (measured by performing specific tasks such as time to complete an exercise test), range of motion, swelling or biomarkers considered reflective of muscle damage or the inflammatory response.

Of the results favouring CWI above, studies employing a cross-over design (the same participants receive both the treatment and control intervention, separated by a pre-defined washout period – a flawed design due to something called the repeated bout affect) or running exercise showed the largest effects.

For all other comparators there were no significant differences for most of the outcome measures, with one or two minor differences for selected outcomes. None of the studies reported adverse events and none identified they would assess potential adverse events a priori (Paula Radcliffe provides potential examples).

A requirement of all Cochrane reviews is the assessment of quality and provision of the risk of bias for data from studies included in the review. Key elements associated with bias in RCTs are assessed and risk is assigned as high, low or unsure according to the methods described for each study. High or unsure risk raises questions about the internal validity (or usefulness) of the data.

The results of the quality assessment in Bleakley et al. are perhaps unsurprising; “The study quality in this review was low. The majority of studies had a high risk of bias…” Examples included adequate sequence generation reported in only half of studies and only one study concealing group allocation, blinding outcome assessors and performing intention-to-treat analysis. Consistently small sample sizes also raised questions as to the power of individual trials.

The review authors concluded “This review provides some evidence that CWI reduces DOMS after exercise when compared with passive interventions involving rest or no intervention. However, it is not possible to draw definitive conclusions on pain or recovery because of the poor methodological quality, and small sample sizes.”

The authors go on to stress that high quality research is required that accounts for the high risk of bias associated with methodologies used in previous studies and incorporates assessment of pre-defined adverse events.

Another requirement of Cochrane reviews is at some point authors must provide an update of their review, usually within 3 to 4 years following publication. An updated search is conducted and any new eligible studies are added to the review. Such an update for Bleakley et al. would likely include data from Crystal et al., data however that adds little to the evidence base and will not change the review’s conclusions.

There are certain times when performing an RCT are not needed, not possible, or not ethical; defibrillation for cardiac arrest, the effect of government policy on health outcomes, harmful effects of radiation for example. Sometimes things just obviously work (e.g. parachute [when it works!] vs. arm flapping).

Maybe this is the case with ice baths? Despite a lack of evidence of effectiveness athletes and their mentors swear by them, the likes of Andy Murray and Paula Radcliffe keen advocates (the Radcliffe exert also makes for a great and worrying exemplar of the ‘science’ behind elite training but that’s another blog).

When I was looking for other examples of embedded non-evidence based practices, BBC online published the headline ‘Resuscitation drug adrenaline questioned in cardiac arrest’. The story highlights how the 50 year-old practice of giving adrenaline after cardiac arrest may actually cause harm rather than help save lives. It also highlights a new trial to definitively test this hypothesis (you can read the protocol here).

The point to illustrate is that when a question is important enough, even it seems difficult to perform (participants in the adrenaline study will not be able to consent immediately and the estimated sample size is 8000); an RCT can and should be done!

Has the case for the definitive ice bath RCT been made? I hope the field finds the question important enough and the moment opportune to produce some high level evidence. A quick check on clinicaltrials.gov and controlled-trials.com suggests not yet. Come on folks! Please.

In the meantime, if ice baths make some athletes “feel” more recovered then this is an important outcome in itself and there’s no problem quoting them for saying so. However, claims of other benefits not based on evidence are disingenuous and misleading. On the flip side, stories of no effect and harm (à la TMS) are equally unjust.

The totality of evidence should be presented to enable fully informed decisions, discussion and debate. Consider this a start.

Note – you may have noticed a number of italicised words throughout this piece. In much of my reading I come across unfamiliar, ‘fancy’ words that give the impression of scholarliness and some how make me feel less so for it. So I bought this book and tried it out here. Now wasn’t that sagacious!?