Nitric Oxide: What is it and why is it important?

Nitric Oxide or NO is a colourless gas found in all of our body’s cells. NO is an important compound for blood vessel health because it helps make sure that the body’s tissues get sufficient oxygen. NO affects two important aspects of the body’s oxygen supply and demand. (Chen et al., 2008) As a vasodilator, NO widens blood vessels by serving to relax vessels’ inner muscles. Secondly, NO controls mitochondrial oxygen consumption by inhibiting cytochrome C oxidase. NO’s overall effect is to increase blood flow and lower blood pressure.


Skeletal muscle relies on blood flow to deliver nutrients and carry away waste products; this process, in turn, relies on adequate NO levels. NO levels can subside with age, which can explain why muscle strength and mass decline over the years, a term known as sarcopenia. Read on to learn more about NO, its role in skeletal muscle function, and how exercise can boost NO levels and help lessen muscle deconditioning.


Strength Training Boosts NO Levels


Skeletal muscle comprises greater than 40% of the human body’s mass, and this muscle requires a constant supply of blood delivered via the circulatory system to help its tissues functioning optimally. Skeletal blood flow is needed for muscle metabolism, endocrine function, and locomotion. This blood flow is controlled by NO as well as other growth factors and mechanisms. (Olfert, et al., 2016)

NO levels decrease with age, but these effects can be partially remedied with exercise. Strength training increases muscle mass by improving NO levels and, therefore, circulation to skeletal muscle. In one study of 35 older women who underwent 12 weeks of resistance training, reductions in both systolic and diastolic blood pressure were observed, and NO levels increased. (Tomeleri, et al., 2017) NO levels were negatively correlated with systolic blood pressure, indicating that levels of this compound may be associated with improved fitness and heart health. A study conducted in Brazil found that low-intensity resistance training improved bioavailability of NO in healthy rats. (Macedo, et al., 2016) A similar study comparing aerobic and low intensity resistance exercise training decreased arterial stiffness in healthy older adults, indicating that NO’s health benefits may reduce heart disease risk. (Otsuki et al., 2020)

How can we exercise to improve the level of muscle-building natural compounds such as NO to reduce the negative effects of aging and improve circulatory and overall health?


Blood Flow Restriction Training Improves NO Levels


A type of training called Blood Flow Restriction Training, or BFRT, may be one way to boost NO levels. BFRT involves using cuffs on the limbs during exercise to maintain blood flow to muscles while preventing blood from traveling back to the heart. In one review of BFRT studies conducted by German researchers, BFRT application led to increased release of anabolic growth factors, stimulation of muscle protein synthesis, higher NO levels, and improvement of arteriogenesis, or the growth of new blood vessels. (Vogel, et al., 2020)


Conclusion


Aging reduces the availability of compounds such as NO and growth factors which can boost musculoskeletal health. Exercise boosts NO levels and promotes healthy blood flow, and BFRT specifically is also associated with many positive benefits, including improved NO levels. The research demonstrates that even low-resistance training, however, can boost NO. BFRT appears to have a synergistic effect on health by improving several different factors including increasing NO levels.


Sources:

Chen K, Pittman RN, Popel AS. (2008). “Nitric Oxide in the Vasculature: Where Does It Come From and Where Does It Go? A Quantitative Perspective.” Antioxid Redox Signal, 10(7):1185-1198.


Olfert M, Baum O, Hellsten Y, and Egginton S. (2016). “Advances and Challenges in Skeletal Muscle Angiogenesis.” Am J Physiol Heart Circ Physiol, 310(3), H326-36.


Macedo FN, et al. (2016). “Increased Nitric Oxide Bioavailability and Decreased Sympathetic Modulation Are Involved in Vascular Adjustments Induced by Low-Intensity Resistance Training.” Front Physiol, doi: 10.3389/fphys.2016.00265.


Otsuki et al. (2020). “Combined aerobic and low-intensity resistance exercise training increases basal nitric oxide production and decreases arterial stiffness in healthy older adults.” Journal of Clinical Biochemistry and Nutrition, 66(1): 62-66.


Tomeleri CM, et al. (2017). “Chronic Blood Pressure Reductions and Increments in Plasma Nitric Oxide Bioavailability.” Int J Sports Med, 38(4):290-299.


Vogel J, et al. (2020). “Exercise-Induced Vascular Adaptations under Artificially Versus Pathologically Reduced Blood Flow: A Focus Review with Special Emphasis on Arteriogenesis.” Cells, 9(2):333.

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