Over 40% of human body mass is made up of skeletal muscle. Maintaining muscle mass is vital to allow physical activity, maintain metabolism, and plays an important role in blood circulation and brain cognition. Losing muscle mass and strength is a common occurrence during the ageing process. This loss of muscle mass as we age is termed sarcopenia. One reason we lose mass and strength is a lack of high resistance exercise. Another reason for this decline is our body becomes less efficient at providing oxygenated blood to muscles and removing waste products such as metabolites from the muscles.
Large amounts of blood is carried from the heart via arteries and returned to the heart thru veins. Skeletal blood flow is important for muscle metabolism, endocrine function, and locomotion, and is regulated by growth factors as well as other mechanisms. (Olfert, et al., 2016)
Microcirculation is the circulation of the blood in the smallest blood vessels, the microvessels of the microvasculature present within muscle and organ tissue. The microvessels include terminal arterioles, metarterioles, capillaries, and venules.
Our bodies are amazing at adaptation and microcirculation can be improved by a complex process called angiogenesis. Angiogenesis means the building of new blood vessels. Angiogenesis is influenced by many factors, but one important factor is Vascular Endothelial Growth Factor or VEGF. VEGF influences how much blood is able to reach muscles to help them function optimally. If VEGF levels decrease, muscle mass and strength with diminish as well.
VEGF Levels Decrease As We Age
VEGF is a growth factor found in the body that is known to promote angiogenesis. (Melincovici et al. 2018) VEGF levels decrease as we age, which may contribute to the de-conditioning and loss of muscle mass and strength we experience. (Ambrose, 2017) However, increasing VEGF levels in adult muscles can improve muscle vasculature and support skeletal muscle function.
So what can we do to improve the level of growth factors such as VEGF to reduce the negative effects of ageing? By creating a hypoxic environment (lack of oxygen), VEGF signalling can be increased thus increasing capillary growth. (Hunt, 2013)
Blood Flow Restriction Training Improves VEGF Levels
Skeletal muscle is capable of regenerating quickly and undergoes significant modification in tissue mass (in terms of atrophy and hypertrophy) in response to global metabolic changes (Smythe, 2016). This modification can occur due to improved VEGF levels.
Blood flow restriction training or BFRT may be one way to boost VEGF levels. BFRT is an exercise and training strategy in which cuffs or wraps are placed on the arms or legs during exercise. The purpose of BFRT is to reduce the inflow of oxygenated blood to the muscles while trapping blood in the limb to prevent the venous return back to the heart. By reducing the amount of oxygenated blood, one creates a hypoxic environment thus stimulating angiogenesis.
BFRT has been shown in scientific studies to boost VEGF levels. Takano et al. demonstrated a significant increase in VEGF (as well as lactate) using BFR and exercise. Increased lactate levels indicates exercising in a hypoxic environment. (Takano 2005)
Shimizu demonstrated improved vascular endothelial function as well as peripheral blood circulation in elderly volunteers who underwent low-intensity resistance training using BFRT for 4-weeks. (Shimizu, 2016)
The benefits of BFRT include improved musculoskeletal function. One-way BFR stimulates strength and muscle size gains are improved VEGF levels thus microcirculation. BFR may help musculoskeletal function in those wanting to improve strength and size to help perform activities of daily living and keep function high.
Ambrose CT. (2017). “Pro-Angiogenesis Therapy and Aging: A Mini-Review.” Gerontology, 63: 393-400.
Apte RS, Chen DS, Ferrara N, VEGF in Signaling and Disease: Beyond Discovery and Development. Cell. 2019 Mar 7;176(6):1248-1264. doi: 10.1016/j.cell.2019.01.021.
Melincovici CS, Boşca AB, Şuşman S, Mărginean M, Mihu C, Istrate M, Moldovan IM, Roman AL, and Mihu CM. (2018). “Vascular Endothelial Growth Factor (VEGF) – Key Factor in Normal and Pathological Angiogenesis.” Rom J Morphol Embryol, 59(2), 455-67.
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.
Hunt, J. E. A., Galea, D., Tufft, G., Bunce, D., & Ferguson, R. A. (2013). “Time course of regional vascular adaptations to low load resistance training with blood flow restriction.” Journal of Applied Physiology, 115(3), 403–411.
Shimizu R, Hotta K, Yamamoto T, Kamiya K, Kato M, Hamazaki N, Kamekawa D, Akiyama A, Kamada Y, Tanaka S, Masuda T. (2016). “Low-intensity Resistance Training With Blood Flow Restriction Improves Vascular Endothelial Function and Peripheral Blood Circulation in Healthy Elderly People.” Eur J Appl Physiol, 116(4), 749-57.
Smythe G. (2016). “Role of Growth Factors in Modulation of the Microvasculature in Adult Skeletal Muscle.” Adv Exp Med Biol, 900, 161-83. Springer ML, Chen AS, Kraft PE, Bednarski M, Blau HM. (1998). “VEGF Gene Delivery to Muscle: Potential Role for Vasculogenesis in Adults.” Molecular Cell, 2(5): 549-558.
Takano, Haruhito, “Hemodynamic and hormonal responses to a short-term low-intensity resistance exercise with the reduction of muscle blood flow. European journal of applied physiology 95, 1(2005 SRC – BaiduScholar), 65-73