Changes In Muscle Structure

During human aging there is a loss of both muscle mass and cross-sectional area that averages 25 to 40% between ages 20 to 80 years (Lexell, 1995). Consistent changes have been seen regardless of technique as measurements of total body potassium, creatinine excretion, CT scans, MRI scans, ultrasound images, and anatomic dissection (see later for details on techniques) have shown consistent and reproducible declines in muscle mass (Lexell, 1995). The loss in muscle mass is due to two factors: the loss of total muscle fiber number and the reduction in the size of specific fibers. Human muscle consists of type I slow-twitch and type II fast-twitch fibers. Type I fibers are involved in endurance activities and generate most of their energy from aerobic metabolism. In contrast, type II fibers provide explosive muscle strength during periods of exercise or intense activity with energy being produced from anaerobic glycolysis. The numbers of both types of fibers in a given muscle decline with age, with losses of up to 60 to 70% of fibers seen (Lexell, 1995). Additionally, selective declines in type II fiber volume also occur during aging (Lexell, 1995). These two changes begin as early as the late 20s and appear to accelerate after age 50 (Lexell, 1995).

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Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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