THERE’S A REASON your yoga teachers say things like, “Eccentrically contract your triceps to slowly lower into Chaturanga,” instead of just, “Contract your triceps.” It’s because there are three different ways a muscle can contract, and how you utilise these actions can affect strength and safety in a pose. So, what is really going on inside the muscle tissue when we flex, and why does it matter?
To get a feel for the mechanics in question, bend your elbow. The biceps on the front of your arm contracts to lift your forearm, creating a shortening of muscle fibres, or concentric contraction. If you keep your elbow bent, your biceps stays contracted to resist gravity in a static (nonmoving), or isometric, contraction. These types of contractions probably feel familiar—they’re what you’d do if you wanted to “make a muscle”.
Now slowly lower your forearm. You might assume that the triceps muscle on the back of your arm, which is responsible for straightening your elbow, is working now. However, because gravity pulls your forearm down, your triceps doesn’t need to do anything. Rather, your biceps continues to contract as it lengthens, resisting gravity. If it didn’t, your forearm would simply fall. Such lengthening, or eccentric contractions, are critical to controlling many movements, from folding forward into Uttanasana (Standing Forward Bend) to jumping back to Chaturanga Dandasana (Four-Limbed Staff Pose) to moving into an arm balance like Parsva Bakasana (Side Crane Pose).
Targeting concentric, isometric, and eccentric contractions in your asana practice will work your muscles through their full range of motion, helping you to develop balanced strength and lessening your risk of injury. To understand these contractions, you need to know what happens in your muscles when they’re working. Muscle cells, or fibres, contain many smaller strands called myofibrils, each of which in turn is comprised of a series of contractile units called sarcomeres. Within the sarcomere, two types of protein filaments—thick laments called myosin and thin filaments called actin—overlap like interlaced fingers.
When a muscle like the biceps contracts concentrically, a signal from the central nervous system prompts the thick myosin filaments to catch hold of nearby thinner actin filaments, forming linkages called cross-bridges. If the pull is strong enough to overcome opposing resistance (usually from the force of gravity), the actin strain slide between the myosin filaments and muscle shortens—in this case, pulling up your forearm.
A similar thing happens during an isometric contraction, except the force generated by the myosin cross-bridges exactly matches the opposing resistance, so there is no movement and your arm stays fixed.
And, if the resistance is greater than the force the muscle generates, such as what happens to the biceps when lowering from a pull-up, the biceps muscle will be stretched, producing an eccentric contraction that allows your arm to lengthen with control. Scientists don’t yet fully understand this process, but it appears that during an eccentric contraction, some myosin cross-bridges continue to latch onto actin filaments, while others are pulled apart.
Perhaps surprisingly, muscles generate more force eccentrically than concentrically, meaning you can lower a heavier weight than you can lift. You can use this principle to build strength by focusing on lowering movements. For instance, controlling the descent from Plank Pose to Chaturanga will eccentrically contract and strengthen your triceps, while pushing back up to Plank is a concentric contraction of your triceps.
Because eccentric contractions produce more force than concentric ones, they also put more stress on muscles. If you’re not used to it, eccentric exercise can damage muscle proteins, triggering delayed-onset muscle soreness, or DOMS—usually at
its worst one to two days after a tough workout. While DOMS may be annoying, it is rarely serious. Your muscles adapt by becoming stronger after a bout of DOMS so the next time you do the same routine, you’re less likely to be sore.
Another caveat about eccentric exercise: It may also stress tendons, the connective tissue that binds muscles to bones. Repeatedly overloading your tendons in this way without allowing for recovery increases your risk of tendon damage, or tendinopathy, a painful condition that can interfere with your practice. Due to their slow metabolic rate, tendons recover gradually; once tendinopathy develops, it can take months for full recovery.
Exploring the entry into Side Crane Pose will help you understand how to use eccentric contractions wisely in your yoga practice.
HOW TO – Use eccentric contractions in Parsva Bakasana (Side Crane Pose)
The transition into an arm balance like Side Crane Pose can be scary. There is a very real risk of falling onto your head, given that one arm is supporting most of your weight. Eccentrically engaging your triceps will allow you to come into the pose safely and with control, avoiding a painful face plant.
Squat with your feet and knees together, then twist your upper body to the right, bringing your left upper arm against the outside of your right knee. Place your hands on the floor alongside your right thigh, shoulder-width apart. As you shift your weight forward onto your hands, lift your feet. Imagine that you are pressing the floor away with your hands. This will keep your triceps eccentrically engaged as your elbows bend, controlling how far your head lowers toward the floor.
When you find your balance, your triceps muscles will work isometrically to keep
you there. However, at the sweet spot where your upper and lower body exactly counterweight each other—like the two arms of a scale—your triceps won’t need to do much. If you sense yourself falling forward, lightly press the floor away with your fingers, concentrically contracting your triceps to return to the balance point. Eventually, as you get even stronger, you can work toward straightening your elbows by further concentrically engaging your triceps.
About the author:
An NYC–based yoga teacher and Feldenkrais practitioner, Joe Miller teaches anatomy and physiology trainings for yoga teachers and students around the world. Learn more at joemilleryoga.com.