Is knotting yourself into a pretzel in a hot room better for you than trying the same thing at room temperature? A recent paper (featuring in the Express, Forbes & the Independent) asked that very question. This study was fairly well reported, with all three of the above news outlets choosing headlines that accurately reflected the research – good stuff! So with that in mind let’s take a look at the study.

Yoga comes in many shapes and sizes but this study focused on a style of yoga called Bikram yoga. Bikram, who’s founder has been in the headlines for some fairly unsavory accusations of late, follows the same strict series of 26 yoga poses at the nice and toasty temperature of 40.5ºC.

A previous study by the same group of scientists found that for people aged 40-60, 9 weeks of Bikram yoga improved how well endothelial cells worked (these are the cells that line the inside of your blood vessels, known to be involved in vascular diseases such as atherosclerosis). So this time the team wanted to work out whether these changes were due to the yoga, the heat it was done at or both.

To figure this out, participants were randomly assigned to either practice Bikram yoga 3 times a week for 12 weeks at the usual 40.5ºC, to do the same sequence at a more pleasant 23ºC or to do no yoga at all (the control group).

So how reliable is this research? Let’s check it out using our toolkit.

1. The study was published in the peer-reviewed Experimental Physiology and the news articles above have accurate headlines and summaries of the research (Forbes get extra kudos for getting a quote from an independent researcher).
2. The press release however fails to mention that the study only included 40-60 year olds, and according to the groups’ previous study the same effect just isn’t there for younger participants (sorry folks!)
3. An obvious downside to studies like this is that all participants are obviously well aware of whether they are practicing yoga or not! This means that some measurements could be affected by the placebo effect. Though this is less likely for a study like this where results were drawn from X-ray scans and blood tests, as opposed to questionnaires of perceived pain for example, the researchers doing the measurements weren’t blinded (they knew what group each participant was in) meaning that some bias could have snuck into the data analysis.
   This is why a randomised double blind placebo-controlled trial is considered the ‘gold standard’ (double blind = neither the participant nor the researcher know which treatment or intervention the subject is receiving).
4. It is worth considering that this study has shown an effect in only one type of yoga – in fact a previous study by the same group didn’t see any changes in vascular function when practicing hatha yoga twice a week, so is it that the Bikram yoga was practiced 3 times a week or is it the type of yoga? It’s very difficult to say.

To better understand whether yoga is beneficial or not overall, collecting many different studies together to look at all the available evidence is probably the best indicator. The Cochrane Library review and summarise all of the evidence that has been collected on a given treatment for a particular illness or benefit, from how to get kids to eat more fruit and veg to yoga for improving health and wellbeing.

Overall this study throws some more evidence into the ring that some types of yoga can be good for some people, sometimes.