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.
See also The A-to-Z Guide to Yoga Cues
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.
The Biomechanical Breakdown of a Cue
To illustrate what I’m talking about, my lab partner, Jana Montgomery, PhD, and I decided to look at what happens when yoga practitioners are cued to do the following in Bridge Pose:
• “Engage your glutes” (an internal/muscular cue)
• “Relax your glutes” (another internal/muscular cue)
• “Drive your knees forward and isometrically drag your heels back” (an external/movement cue)
We wanted to look at the differences in practitioners’ bodies when they heard each of these cues, and we chose two different internal (muscular) cues—because engaging or relaxing the glutes in Bridge Pose is fairly controversial, with some teachers instructing students to activate the glute muscles and others urging them to “let your glutes hang like a peach from a tree.” Not only did we want to see how the body responds to these internal and external cues, we also wanted a definitive, biomechanical explanation for what happens when yoga practitioners activate the glutes (or don’t) in Bridge Pose.
So, we hooked one yogi up to wireless electromyography (EMG) to measure activity in seven key muscles: the gluteus maximus (buttocks), biceps femoris (hamstrings), erector spinae (spinal muscles), latissimus dorsi (mid-back muscles), rectus femoris (quadriceps), gastrocnemius (calves), and tibialis anterior (shins).
We compared muscle activation in these areas for all three cue variations. To start, we asked our yogi to perform a maximum voluntary contraction (MVC) for each of the seven muscles—which essentially means we asked her to use each muscle to its max. We did this by having her push against a resistance while performing an action that primarily used the targeted muscle. For example, we asked her to push the ball of her foot against a strap attached to the chair she sat on to activate her calf muscle. We needed 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.)
The Research-Backed Way to Cue Bridge Pose
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).
About Our Pros
Author and model Robyn Capobianco, PhD, is a yogi whose curiosity about the science of yoga led her to a doctoral program in neurophysiology. She brings more than 20 years of yogic study, practice, and teaching to her scientific research on the neural control of movement. Her research aims to fundamentally alter the way yoga teachers teach—and provide the scientific foundation that she feels is missing from the yoga community. Learn more at drrobyncapo.com.
Jana Montgomery, PhD, is a lifelong learner and athlete. Her passion for science and sports led her to pursue her PhD in the biomechanics of human movement. Her research specializes in understanding how external forces or equipment affect the way people move—specifically adaptive equipment and technology. Learn more at activeinnovationslab.com.