A bruise, medically known as a contusion, occurs when small blood vessels beneath the skin rupture. This rupture allows blood to leak into the surrounding tissues, causing visible discoloration on the skin’s surface. The body reabsorbs this trapped blood over time, causing the mark to change color before fading away. Finding these marks after intense physical activity is common, and post-workout bruising is usually a temporary and harmless sign of physical stress.
Understanding Exercise-Induced Capillary Damage
Intense exercise, particularly resistance training or high-impact activities, causes microscopic damage to muscle fibers, known as microtrauma. While microtrauma is a normal part of muscle adaptation and growth, it can also damage the capillaries, the tiny blood vessels woven throughout the muscle tissue. This localized rupture leads to minor bleeding and the resulting bruise.
Heavy lifting can also cause excessive pressure on blood vessels, especially when using poor form or exerting maximum force. Techniques that involve holding the breath, like the Valsalva maneuver during a heavy squat or deadlift, increase internal pressure, which can strain and rupture blood vessels. Additionally, direct impact from equipment, such as bumping a barbell against the shins or chest, or friction from repetitive motions can directly cause small vessels to break under the skin. These types of exercise-related bruises are generally minor, localized to the area of stress or impact, and are not usually a sign of a serious underlying problem.
Medications and Nutritional Factors That Increase Bruising
External factors not directly related to exercise mechanics can significantly increase a person’s susceptibility to bruising. Certain over-the-counter pain relievers, specifically Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) like ibuprofen or naproxen, can interfere with the blood’s ability to clot effectively. By inhibiting platelet function, these medications make it easier for blood to seep out of damaged capillaries, leading to larger or more noticeable bruises after a workout. Prescription blood-thinning medications, known as anticoagulants, reduce the blood’s clotting ability and raise the risk of easy bruising.
Some nutritional supplements and dietary deficiencies also play a role in vascular fragility and clotting ability. Supplements such as high-dose fish oil, ginkgo biloba, and Vitamin E are thought to have a mild blood-thinning effect, which may increase bleeding under the skin. Deficiencies in certain vitamins can compromise the integrity of blood vessels and the body’s clotting cascade. For example, a lack of Vitamin C impairs collagen production, which keeps blood vessel walls strong. Vitamin K is necessary for creating clotting factors, and a deficiency can lead to prolonged bleeding and easy bruising.
When Bruising Requires Medical Attention
While most post-workout bruising is benign, certain signs suggest that the cause may not be related to normal exercise stress. Bruising that occurs frequently, is unusually large, or appears without any clear cause or trauma should prompt a discussion with a healthcare professional. Bruises accompanied by rapid or excessive swelling, especially in the legs, or those that are intensely painful and interfere with movement may signal a more serious underlying injury.
Systemic issues affecting the body’s ability to clot blood can be signaled by unusual bruising patterns. Warning signs include unexplained nosebleeds, bleeding gums, or petechiae—tiny, pinpoint red spots indicating small vessel leakage. Underlying conditions, such as inherited bleeding disorders (like hemophilia or von Willebrand disease) or issues with the liver or bone marrow, can cause an increase in bruising. If a bruise does not fade or worsens after two weeks, or if it is accompanied by other symptoms like joint pain or illness, medical evaluation is recommended.