Anaerobic training includes high-intensity training methods in which the energy source is not dependent on the use of oxygen. Sprinting, high-intensity resistance training and a number of sports rely on anaerobic training for top performance. The body undergoes a multitude of adaptations with consistent anaerobic training, with virtually every body system affected. From your cardiovascular system to your endocrine system, anaerobic training can provide adaptations beneficial for good health and high performance.
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Changes in the nervous system happen in both the central and peripheral nervous systems. Activity in the motor cortex of the brain, the area responsible for controlling and executing movement, increases with anaerobic training. The increase in activity leads to increased recruitment of motor unit tracts along the spinal cord, causing the motor units to fire more frequently. The rapid nerve firing of the motor nerves to the muscle fibers leads to muscle hypertrophy and increased spindle sensitivity. Both of these adaptations improve muscular strength and power.
Anaerobic training increases muscle size through hypertrophy. There are two main types of muscle fibers. Type II fibers are called "fast-twitch" fibers and are able to contract at a higher force than type I. With anaerobic training, especially heavy resistance training, all muscle fibers increase in size because all fibers are recruited to produce the high force needed. Type II fibers do, however, have greater increases in size than type I fibers. Other muscular adaptations include improved calcium release and increased buffering capacity. Calcium is the main regulatory and signaling molecule in all muscle fibers. Improved calcium release improves the muscles' ability to use it. An increased buffering capacity helps your body fight muscle fatigue despite lactic acid accumulation.
Connective Tissue Adaptations
Connective tissue includes bones, tendons, ligaments and fascia. The high-force muscle contractions of anaerobic training increase the pull on the bones. This increased pull on the bones may help improve bone mineral density. A study published in "Calcified Tissue International" in 2000 showed that high-intensity resistance training had a greater impact on bone mineral density than moderate-intensity resistance training due to the greater pull of the muscles on the bones. Anaerobic training can also improve the strength of tendons and ligaments, both at the site of attachment and within the body of the tissues, and can improve the strength of the fascia around the muscles.
The release of hormones is critical for performance and for other training adaptations to occur. Insulin increases glucose uptake by the muscles during exercise training. Testosterone increases with training; this hormone is important for muscle hypertrophy. Growth hormone released during exercise promotes connective tissue growth. Epinephrine and norepinephrine prepare the cells to use glucose as fuel and increase the heart rate, blood pressure and respiration rate to meet the physical demands of training. Glucagon and cortisol ensure the body has sufficient energy to continue training by breaking down carbohydrates and fats. Anaerobic training can improve the acute response to exercise, ensuring these hormones are released promptly for the body to perform at a high capacity.
The cardiovascular system responds rapidly to anaerobic exercise, increasing heart rate, stroke volume, cardiac output, blood flow to muscles and systolic blood pressure. These responses help ensure that sufficient oxygen is delivered to the muscles via the blood. With anaerobic training, the cardiovascular response is decreased both at rest and with activity. This means that a higher level of performance can be achieved as the body is using the blood supply more efficiently.