The biomechanical breakdown of a cue
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 drrobyncapo.com. 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 activeinnovationslab.com.