Muscle contractions are interesting to take our training to the next level. Knowing each type will help us generate more strength, endurance or hypertrophy.
Some training routines focus on the concentric phase of the exercise to increase muscle gains. Discovering the right type for each movement can help you perform better. And above all, to achieve our goals.
Why do muscles contract?
Muscles serve various purposes in the body. Muscles contract for various reasons, but mainly they do the following:
- They offer stability to the joints and connective tissues: the muscles lengthen and shorten, sometimes involuntarily, as the body needs them.
- They produce heat to maintain body temperature: about 40% of body temperature is converted to muscle work. Shivering is the body’s response to feeling cold, and skeletal muscles are activated to warm the body.
- Maintain posture: Muscles help us maintain a position such as sitting or standing.
Muscles have different types of contractions, depending on the movement and effort required.
Isotonic contractions are those in which the muscle changes length as it contracts, while the load or resistance remains the same. As a result, this causes the movement of a part of the body. There are two types of isotonic contraction: concentric and eccentric.
Concentric contractions are those that cause the muscle to shorten as it contracts. As the muscle shortens, it generates enough force to move an object. This is the most popular type of muscle contraction. An example is bending the elbow from straight to fully flexed, causing a concentric contraction of the biceps brachii. Concentric contractions are the most common type and occur frequently in daily activities and sports.
This type of movement is one of the main ways to strengthen muscles and encourage hypertrophy , an increase in the size of muscles. Although effective, this type of contraction alone will not produce strength or mass results compared to workouts that combine different muscle contractions.
Eccentric contractions are the opposite of concentric contractions and occur when the muscle lengthens while contracting . This occurs when the dumbbell is lowered in a bicep curl exercise. The muscle is still contracting to hold the weight all the way through, but the biceps muscle is lengthening. During this muscular movement, the muscle fibers are stretched under the tension of a force greater than that generated by the muscle. Unlike a concentric contraction, eccentric movements do not pull a joint in the direction of a muscle contraction. Instead, it decelerates a joint at the end of a movement.
Another very common example is the quadriceps muscles in the front of the thigh when landing from a jump. As we land, the thigh muscles, and in particular the quadriceps in the front of the leg, contract strongly but also lengthen at the same time. This type puts a lot of strain through the muscle and is commonly involved in muscle injuries. Plyometric training exercises (jumping) involve a lot of eccentric contractions and can lead to severe muscle soreness if you overdo it too soon.
The combination of eccentric and concentric muscle contractions produces better results in strength training, as it increases strength and muscle mass. However, you may be more prone to exercise-induced injuries during eccentric movements.
Some movements or exercises that exhibit eccentric movements include walking, dumbbell lowering, calf raises, squats, and triceps extensions.
isometric muscle contraction
Isometric contractions occur when there is no change in the length of the contracting muscle . This occurs when we carry an object in front of us, as the weight of the object pulls the arms down but the muscles contract to hold the object at the same level. Another example is when we grab something, like a tennis racket. There is no movement in the joints of the hand, but the muscles contract to provide enough force to hold the racket firmly.
The amount of force a muscle can produce during an isometric contraction depends on the length of the muscle at the point of contraction. Each muscle has an optimal length at which maximal isometric force can be produced.
Isometric movements are muscle contractions that do not cause the joints to move. The muscles are activated, but they do not need to be lengthened or shortened. As a result, isometric contractions generate force and tension without any movement through the joints.
Common movements that demonstrate isometric contractions include planting, bringing an object in front of us in a stable position, holding a dumbbell weight in place midway through a biceps curl, isometric bridge, or wall squat.
Isokinetic contractions are similar to isotonic contractions in that the muscle changes length during contraction , where they differ in that isokinetic contractions produce movements of a constant velocity. To measure this, special equipment known as an isokinetic dynamometer is required. Examples of the use of isokinetic contractions in everyday life and in sports activities are rare. The best is the breaststroke in swimming, where the water provides a constant and uniform resistance to the adduction movement.
Isokinetic exercise is a type of strength training. It uses specialized exercise machines that produce a constant speed no matter how hard we exert ourselves. These machines control the pace of an exercise by fluctuating resistance throughout the range of motion. The speed remains constant despite the force we exert.
We can adjust the exercise speed and range of motion to meet our needs. Different attachments on the machines can isolate and target specific muscle groups. We can use isokinetic exercise to test and improve muscular strength and endurance.