While flowing through poses you work your muscles in a variety of ways. While exercising the muscles, force is exerted on the muscle fibers. This happens when the muscles become shortened, lengthened, or remain at the same length. During this process three contractions occur; concentric, isometric, and eccentric.
Muscle shortening is known as concentric contraction. This means that the decrease in a joint angle occurs through the bending of the knee or elbow. Muscle lengthening is known as eccentric contraction, which increases a joint angle causing a straightening of the bent knee or elbow. Whenever a joint moment occurs it causes isotonic muscle contraction. This kind of muscle contraction occurs during the lifting or lowering of an object.
When pressure is exerted, tension develops, but there is no movement or change in length. The muscle is said to be in an isometric position and the contraction of the muscle is static. This occurs when you stretch your hands out and a heavy object is placed in them. When you are not lowering your arm to place the object down, there is no movement in your body. this is when your muscles provide support to the weight.
As muscles main function is to stabilize the spine, isometric exercises help to make the muscles stronger. These exercises are useful when you intend to build strength around the injurious part of your body. The use of muscle contractions help muscles move and build your capacity to maintain balance in poses and reduce the chances of injury.
In muscle cells or fibers there are many small strands known as myofibrils, which constitute series of contractile units known as sarcomeres. Sarcomeres contain two types of protein filaments known as myosin and actin. Myosin is thick filament while actin is thin filaments.
When the muscles of biceps contracts concentrically, linkages called cross bridges are formed because of the myosin filaments that comes in contact with the thinner actin filaments. If you’re pulling up your forearm, trying to oppose any kind of resistance, the actin strands slip between the myosin filaments causing the muscle to shorten.
A similar thing occurs during an isometric contraction except the force exerted by the myosin conjures to any resistance, so that there’s no movement in your arms. If resistance is more than the force that muscles are producing, the bicep muscles will be stretched to generate an eccentric contraction that lengthens your arms. This happens because during the eccentric contraction, some myosin cross bridges continue to latch on with actin filaments while others are stretched apart.
Through this, you can assume that muscles produce more force eccentrically rather than concentrically. Meaning it’s easier to lower the heavy object instead of lifting it up. This principle can be used to strengthen the muscles by concentrating on lower movements.
For example, if you control the descent position from Plank pose to Four-Limbed Staff pose that would cause eccentrically contract. This would make your triceps stronger, and if you push yourself to Plank pose, it’s a concentric contraction of your triceps.
Eccentric contractions generate more force rather than concentric ones, so they put more stress on your body. If you’re not a habitual performer of eccentric exercise, there might be a loss of muscle proteins, causing muscle soreness.
In medical terms, this condition is known as DOMS which generally gets worst after one or two days of tough workouts. However, it doesn’t mean eccentric exercises should be avoided, as these poses make the muscles strong and more resilient.