Biome­chan­ics

Telling yo­gis to “en­gage” or “ac­ti­vate” cer­tain mus­cles may be do­ing more harm than good. Teacher and re­searcher Robyn Capo­bianco breaks down the sci­ence.

Yoga Journal - - CONTENTS - By Robyn Capo­bianco, PhD, with Jana Mont­gomery, PhD

WHEN I PRAC­TICE YOGA IN A PUBLIC CLASS, I love the com­bi­na­tion of a good flow and longer holds. The op­por­tu­nity to ex­plore the move­ment of my breath and body while ex­pe­ri­enc­ing stillness helps me leave class feel­ing great.

In a re­cent vinyasa flow class, the in­struc­tor called out Virab­hadrasana II (War­rior Pose II) and said we were go­ing to hold the pose. I was ex­cit­edly about to drop into my breath for the hold when the teacher then called out, “Now, con­tract the mus­cles of your back and outer hips, and en­gage the mus­cles of your in­ner thighs.” As if that weren’t enough to at­tempt at once, she added, “Then, turn on your tri­ceps.” I was bog­gled. How was I sup­posed to con­tract my outer hips and en­gage my in­ner thighs and turn on my tri­ceps? I have a PhD in neu­rome­chan­ics, and I couldn’t fig­ure it out. As a re­sult, that in­ner peace I was go­ing for turned into ut­ter con­fu­sion, and rather than be­ing in the pose, my in­ner teacher piped up (al­beit silently) as I con­structed cues that would bet­ter help all of us stu­dents in the room ac­com­plish the ac­tions our teacher was re­quest­ing.

Sadly, mus­cu­lar cues like “con­tract,” “turn on,” or “re­lax” are be­com­ing in­creas­ingly com­mon in yoga class. But do stu­dents— even ad­vanced prac­ti­tion­ers—re­ally know how to en­gage these mus­cles? When you’re told to “en­gage your ham­strings” in Setu Bandha Sar­van­gasana (Bridge Pose), for ex­am­ple, are you re­ally en­gag­ing your ham­strings to the best of your abil­ity? Or would you be able to more ef­fi­ciently en­gage your ham­strings if the teacher told you to “iso­met­ri­cally drag your heels back to­ward your butt”? And more im­por­tantly, do cues to en­gage spe­cific mus­cles achieve their in­tended goals of help­ing us find bet­ter align­ment and ul­ti­mately feel more em­bod­ied? Sci­en­tific ev­i­dence points to no.

Re­search on mo­tor learn­ing con­sis­tently finds that in­struc­tions that have an in­ter­nal fo­cus (read: cues for mus­cu­lar ac­tions, such as “con­tract your ham­strings”) are much less ef­fec­tive at ac­tu­ally trig­ger­ing con­trac­tion than ones that have an ex­ter­nal fo­cus—mean­ing they are di­rected at the ac­tual move­ment that prompts a mus­cu­lar ac­tion, such as “try to drag your heels to­ward your butt.” Ac­cord­ing to re­search pub­lished in Med­i­cal Ed­u­ca­tion, ex­ter­nal cues au­to­mat­i­cally gen­er­ate the mo­tor com­mands that will ac­ti­vate the mus­cles nec­es­sary for ac­com­plish­ing the task. In fact, the study au­thors found that in con­trast, cues for spe­cific mus­cu­lar ac­tions ac­tu­ally con­strain the nat­u­ral mo­tor con­trol sys­tem in the body and in­ter­fere with nor­mal mo­tor plan­ning and ex­e­cu­tion, po­ten­tially re­sult­ing in poor pose ex­e­cu­tion and mus­cle-ac­ti­va­tion im­bal­ance.

It makes sense: when you’re asked to move, your brain—with the help of the vis­ual, vestibu­lar (re­lat­ing to the in­ner ear and sense of bal­ance), and pro­pri­o­cep­tive (the abil­ity to sense joint po­si­tion and move­ment) sys­tems—gen­er­ates a mo­tor com­mand that au­to­mat­i­cally ac­ti­vates the mus­cles nec­es­sary for ac­com­plish­ing the task. We don’t need to cue spe­cific mus­cles for this to hap­pen.

Of course, there are ex­cep­tions. For ex­am­ple, if you’re re­cov­er­ing af­ter an in­jury or try­ing to cor­rect an ir­reg­u­lar move­ment pat­tern, it may be more help­ful to cue a spe­cific mus­cle. But it’s my opin­ion that these cues are best done in pri­vate set­tings, when the end goal is spe­cific and clear and the teacher can closely ob­serve the re­sults. In group classes, you can’t ac­tu­ally see the re­sults of in­ter­nal (mus­cu­lar) cues, and you may be do­ing more harm than good.

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