You may have noticed that your muscles swell and get larger while you work out. The two primary causes are an increased blood flow to the muscle and general inflammation in the muscle. When your muscles swell, it makes it difficult for you to move the body parts associated with those muscles and limits their range of motion. The duration of this swelling varies, depending on the underlying cause, and can be influenced by several recovery techniques.
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Muscle Damage and Inflammation
One primary cause of muscle swelling when you lift weights is localized muscular damage. As you work out, you are actually damaging the muscular tissue so that it must compensate by making itself stronger upon repair. One of the most damaging types of muscular movement is an eccentric contraction, according to "Muscle Soreness, Swelling, Stiffness and Strength Loss after Intense Eccentric Exercise," published in the British Journal of Sports Medicine. An eccentric muscular contraction, or “negative” in weight room lingo, occurs when a weight is stronger than the force you are trying to generate and causes a lengthening of your muscles. For instance, lowering a barbell slowly to your chest by fighting the resistance is a type of eccentric muscular contraction.
Muscular Blood Flow
Local factors within the muscle control the muscle's volume of blood. As you exercise, blood is diverted to working muscles to provide enough oxygen and energy for contractions. Increased blood flow also allows for waste products removal from the muscle. Muscular-contraction type also dictates how much blood flows into a muscle. An isometric contraction, encountered when a muscle forces against an immovable object, causes the muscle to slow the blood flow away from the muscle by pressing against the veins. This increases the “pump” or amount of blood in the muscle.
Muscular Swelling Duration
Swollen muscles can start during a workout and continue for up to 72 hours after training. The level of swelling will diminish with each day. The largest swelling will be reduced after the first few hours of training as blood is redistributed to normal levels throughout the body. For swollen muscles due to inflammation, the process typically lasts until full recovery and repair of the muscle takes place.
You can use several techniques to speed the recovery process for swollen muscles. After your workout, perform a cooldown with cardiovascular exercise at a low to moderate pace for 10 minutes. This allows dispersal of any blood pooled in a muscle. This also allows for quicker repair by shuttling waste products out of the swollen muscles. Consuming protein before and after workouts also speeds the recovery process. Proteins are the building blocks of muscles; therefore, working out increases the need for protein in your diet for muscle repair.