The biome­chan­i­cal break­down of a cue

Yoga Journal - - BIOMECHANICS -

These are the per­cent­ages of max­i­mum vol­un­tary con­trac­tion (MVC) for each of the seven mus­cles ac­ti­vated in Bridge Pose when yoga prac­ti­tion­ers are given cues with a mus­cu­lar fo­cus (such as “en­gage your glutes” or “re­lax your glutes”) ver­sus an ex­ter­nal fo­cus (such as “drive your knees for­ward and drag your heels back”).

to un­der­stand how much she could vol­un­tar­ily ac­ti­vate this mus­cle so we could nor­mal­ize the ac­ti­va­tion in the pose vari­a­tions to this base­line value. We did a vari­a­tion of this for each of the mus­cles we recorded. Then, we cal­cu­lated the per­cent­age of MVC of each mus­cle dur­ing each of the Bridge Pose cue vari­a­tions. (While we col­lected data on just one yogi with no his­tory of pre­vi­ous in­jury, we ex­pect the mus­cle ac­ti­va­tion pat­terns to be sim­i­lar for most healthy adult yo­gis.)

First, we looked at the in­ter­nal cue “en­gage your glutes.” Mus­cle ac­tiv­ity was high­est in the glutes dur­ing this vari­a­tion com­pared with the other vari­a­tions we tested (94 per­cent MVC), and sec­ond high­est in the spinal mus­cles (78 per­cent MVC). (See “The biome­chan­i­cal break­down of a cue” on page 58 for the per­cent­ages of MVC of all seven mus­cles ac­ti­vated when the yogi heard this cue, as well as the other two cue vari­a­tions that fol­low.)

Next, we looked at the in­ter­nal cue “re­lax your glutes.” You’ve prob­a­bly heard that when you re­lax your glutes in Bridge Pose, your ham­strings will ac­ti­vate more to com­pen­sate. How­ever, we found that the op­po­site hap­pens. Ham­string mus­cle ac­tiv­ity dur­ing the “re­lax your glutes” cue was a mere 3 per­cent of MVC com­pared with the 15 per­cent mea­sured dur­ing the “en­gage your glutes” vari­a­tion. In­stead, the back mus­cles and the quadri­ceps picked up the ex­tra slack. Mus­cle ac­tiv­ity in the calves and shins also de­creased con­sid­er­ably com­pared with the “en­gage your glutes” cue.

So, what hap­pened when the yogi heard the ex­ter­nal cue “drive your knees for­ward and drag your heels back” dur­ing Bridge Pose? The glutes ac­ti­vated at 82 per­cent of MVC, and the erec­tor spinae shared the load at 77 per­cent MVC. What’s more, the sup­port­ing mus­cles at work in Bridge Pose—the latis­simus dorsi and the ham­strings— worked equally as hard at 15 per­cent MVC. These find­ings show a syn­er­gis­tic ac­ti­va­tion of the mus­cles through­out the body when an ex­ter­nal, non-mus­cu­lar cue is used. (Read: The mus­cles worked to­gether in­stead of one mus­cle per­form­ing the ma­jor­ity of the work to keep the body in the pose.)

What the data means

These find­ings, along with the ex­ist­ing re­search, demon­strate that giv­ing an ex­ter­nal cue is more likely to lead to bal­anced mus­cu­lar ac­tion in the body dur­ing Bridge Pose than cue­ing mus­cles. This is im­por­tant, be­cause mus­cle im­bal­ances leave us prone to in­jury. By pro­mot­ing bal­anced ac­tion within yoga asana, we can mit­i­gate in­jury risk. When we cued some­one to “re­lax your glutes” in an at­tempt to in­crease load on her ham­strings, we ac­tu­ally in­creased the load on her back. Do­ing so can lead to po­ten­tial for in­jury—par­tic­u­larly for peo­ple with pre-ex­ist­ing back in­juries. Fur­ther­more, when we aren’t con­stantly try­ing to fig­ure out how to “ac­ti­vate” or “re­lax” cer­tain mus­cles (and mi­cro­manag­ing our ner­vous sys­tem as a re­sult), we are able to stop fid­get­ing—and drop into the flow of our breath, al­low­ing the prac­tice to truly be a mov­ing med­i­ta­tion. Based on what I found in the biome­chan­ics lab, here are the ac­tions I say to my­self and the cues I use when I’m prac­tic­ing and teach­ing Bridge Pose:

1 Lie down on your back with your feet on the floor, knees bent and stacked di­rectly above your an­kles.

2 Press the floor away with your feet, and push your hips to­ward the sky.

3 Use your arm vari­a­tion of choice: ei­ther clasp your hands un­der your back, hold onto a strap, or use “ro­bot arms” by bend­ing your el­bows and keep­ing your up­per arm bones on the mat, point­ing your fin­gers to­ward the sky.

4 Drive your knees for­ward as you iso­met­ri­cally drag your heels back (your heels won’t ac­tu­ally move).

OUR PROS Robyn Capo­bianco, PhD, brings more than 20 years of yo­gic study, prac­tice, and teach­ing to her sci­en­tific re­search on the neu­ral con­trol of move­ment. Learn more at dr­robyn­ Jana Mont­gomery, PhD, spe­cial­izes her re­search in un­der­stand­ing how ex­ter­nal forces or equip­ment af­fect the way peo­ple move, specif­i­cally adap­tive equip­ment and tech­nol­ogy. Learn more at ac­tivein­no­va­tion­

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