May Research Round-Up: Hamstring Strain Injury Prevention Edition
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Interesting data. I’m curious to know how big the test groups were. The bottom line appears to be: get your eccentric nordic hamstring curl strength up to cover your bases.
Maybe youre referring to small numbers being problematic in statistical testing (if you arent, ignore this post)? Thats the most common misunderstanding by laymen in statistics! It probably stems from the caveat for researchers that a large sample size is desirable in order to get robust, significant results.
However, if your results post hoc ALREADY have been shown to be mathematically significant, then sample size simply doesnt matter. And if they are significant with a small sample group that means that the effects are probably pretty strong to have become significant with that small a sample size in the first place. That is the case for the two studies mentioned above, they have huge effect sizes (the magnitude of the difference between control and training group; compare that for example to red meat consumption and cancer, there were talking about odds ratios of 1.1 instead of 2. or 3.something) and are significant (meaning its less likely than 5% that this result is pure chance (of drawing weird samples to the two groups, for example)).
So its the other way round: With huge sample sizes, tiny differences will get statistically significant – with small sample sizes thats very unlikely.
Small sample sizes sometimes have problems in external validity (“Those were white 21yr-olds, but I´m black and 22!”), but not in internal validity once they show significance (which is harder to achieve in the first place).
Spread this to as many friends as possible to bury the most common misunderstanding in statistics in laymen. Thanks! 🙂
N.B.: In the first study, sample size was huge, 600 players. http://bjsm.bmj.com/content/48/7/609.3.abstract
Still large in the second one, N=300. http://www.ncbi.nlm.nih.gov/pubmed/25137368
They apparently had money to spend 🙂 .
I wonder if this also would apply on machine eccentric hamcurles or there is any way to perform the nordic hamcurls without a partner in a gym.
google “Erin Stern Nordic curls” on YouTube…there’s a good vid of her doing it with the help of a bar.
Nordic hamstring curls can be performed alone – you just need support for your feet (to hold feet in place). Many large gyms and athletic training centers have racks for this purpose. You can also use a wide resistance band (the full loop version) to attach to a rack for more assistance in getting “down” and (possibly) a med ball (in case you cannot do a full rep to the floor and back up). Similar contraction can be found on the glute/ham hyper machine as you can stabilize your feet and use the pad to help get your body back up. Just make sure you are contracting your hams and glutes and not doing a hyperextension for back.
Does anyone know of any research on hamstring injuries being prevented by Romanian Deadlifts? I would imagine that, since it’s a strongly eccentric hamstring exercise like the NHC, it may produce similar results.
Hi Mike,
This study did not use the RDL but used “lengthening exercises” in general. Also, it was a rehabilitation from injury study and not an injury prevention study but these concepts are very closely related. See full text, including pictures of the exercises, here:
http://www.rcsi.ie/files/facultyofsportsexercise/20140903021217_Br%20J%20Sports%20Med-2013%20-%20Acute%20H.pdf
There is no study actually exploring RDLs specifically to my knowledge.
Hope this helps,
Chris.
Thanks for the quick reply and the link!