Understanding the different ways our muscles contract to power up our asana practice.
There’s a reason why yoga teachers say , “Eccentrically contract your triceps to slowly lower into Chaturanga,” instead of just, “Contract your triceps.” This is because there are three different ways a muscle can contract, and how we 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?
Three Types of Muscle Contractions
To get a feel for the mechanics in question, we can bend elbow. The biceps on the front of our arm contracts to lift the forearm, creating a shortening of muscle fibers, or concentric contraction. If we keep the elbow bent, our biceps stays contracted to resist gravity in a static, or isometric, contraction.
Now slowly lower our forearm. We may assume that the triceps muscle on the back of our arm, which is responsible for straightening our elbow, is working now. However, because gravity pulls our forearm down, our triceps does not need to do anything. Rather, our biceps continues to contract as it lengthens, resisting gravity. Such lengthening, or eccentric contractions, are critical to controlling many movements, from folding forward into Uttanasana to jumping back to Chaturanga Dandasana to moving into an arm balance like Parsva Bakasana. Use All Three Muscle Contractions in Our Yoga Practice
Targeting concentric, isometric, and eccentric contractions in our yoga practice will work our muscles through their full range of motion, helping us to develop balanced strength. To understand these contractions, we need to know what happens in our muscles when they are working. Muscle cells, or fibers, 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 filaments 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, the actin strands slide between the myosin filaments and the muscle shortens—in this case, pulling up our 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 our arm to lengthen with control.
Perhaps surprisingly, muscles generate more force eccentrically than concentrically, meaning we can lower a heavier weight than you can lift. We can use this principle to build strength by focusing on lowering movements. For instance, controlling the descent from Plank to Chaturanga will eccentrically contract and strengthen our triceps, while pushing back up to Plank is a concentric contraction of our triceps.
Understanding the Skeletal Structure Most of us may think that our skeletal structure is a solid and lifeless part of us, but the truth is that it is alive like any other part of our body. Our skeletal structure constantly breaks down and renews itself in a two-step process called bone remodelling. The rate of bone remodelling depends on the amount of calcium that is stored in the bones and present in our diet, along with three catalysts, vitamin D, hormones and exercise. All of these determine the effectiveness of calcium used by our body to renew the bones and also prevention of bone loss. How Yoga improves Joint and Skeletal Structure The more we learn and understand bone health, the more it seems that yoga along with a green diet, helps create a strong base for healthy bones. Yoga is different from other exercises like walking, jogging, or other sports, as it is a weight-bearing exercise. This means that when we perform the asanas, we are holding the weight of our body up against gravity. However, like other weight-bearing exercises, yoga does not cause damage to cartilage or stress to the bones. Instead, the practice lengthens as well as flexes our muscles, holding them in place, creating tension on the bone. For instance, in yoga poses such as Virabhadrasana 1 and 2, Revolved Anjaneyasana, Revolved Triangle, our legs become the weight-bearing points because they support the entire body weight.
Due to the benefit of stretching and increasing muscle strength, yoga asanas enable us to expand our normal range of motions making us more capable of performing day to day tasks better. Each joint or group of joints in our body has a range of motions which is measured in degrees. For instance, our lower back and lumbar spine, has a range of motion about 30 degrees backwards and about 70 degrees flexion.
Yoga poses which are isometric train the smaller muscles that surround the joints so that they are able to withstand more pressure, and we are able to work them harder to stabilise ourselves. For example, yoga poses like Vrikasana require us to balance our body on one leg and change elevation. Supta Matsyendrasana require us to rotate our supporting muscles to work for stability and balance. These poses help us in improving the functioning of the body parts involved in our daily tasks.
