In response to aerobic exercise, many training adaptations take place that increases oxygen delivery to working muscles. These adaptations take place over weeks to months. In response to aerobic training, our heart becomes a more efficient pump, energy-producing organelles called mitochondria increase in number and become more efficient, and the density of tiny blood vessels called capillaries that surround muscle tissue goes up. The increase in capillary density around muscles that occurs in response to exercise training is called angiogenesis. However, a new study shows that after menopause, women may produce fewer of these new capillaries in response to a workout.
What Research Shows about Menopause, Exercise, and Blood Vessels
For the study, researchers asked two groups of women, one group in their 20s and the other between the ages of 59 and 70 to take part in an 8-weeks exercise program. The subjects trained 3 times weekly by taking part in spin classes. In the classes, the exercise intensity varied from moderate to moderately high intensity. Before the study, the researchers did a muscle biopsy on their thigh muscles to measure capillary density and the levels of certain proteins. They repeated the biopsy upon completion of the 8-week program for comparison.
The results? Post-menopausal women who took part in the spin classes for eight weeks didn’t experience the expected increase in capillaries around muscle tissue in response to the aerobic training sessions that younger women and men experienced. They formed fewer of these tiny blood vessels than younger women who were still premenopausal, although their fitness level improved and they experienced other benefits from the workouts.
Why is reduced capillary formation important? The extra capillaries that form in response to aerobic exercise increase oxygen delivery to muscle tissue for better aerobic fitness, but they also play a role in metabolic health. These capillaries transport sugars, fatty acids, and nutrients from the bloodstream to the muscle. Plus, these additional capillaries improve insulin sensitivity since sugar can leave the bloodstream and enter the muscle easier when more capillaries are surrounding the muscle.
Does Estrogen Play a Role in the Blood Vessel Response to Exercise?
Why is it harder for post-menopausal women to form new capillaries around muscles in response to aerobic exercise? The investigators believe lack of estrogen may be a factor. Having more circulating estrogen seems to help these tiny blood vessels form in response to training. Having a higher estrogen level increases the number of cells involved in angiogenesis, the formation of new blood vessels. It may be that women who take hormone replacement therapy have a better response since they’re getting estrogen from an outside source. This would be a good focus for future research.
High-Intensity Exercise and Blood Vessel Health
Despite these findings, another study finds that exercise intensity is a factor in angiogenesis. High-intensity exercise may enhance angiogenesis, the formation of new blood vessels around muscles, even in older women after menopause. How do we know this? A small study of 15 women published in BMJ Open Sport and Medicine found that although high-intensity interval training didn’t boost the total number of cells involved in angiogenesis, it improved the function of ones already in existence. In turn, this makes it easier for new capillaries to form around muscles.
What can we learn from this? Brief bouts of interval exercise may be most beneficial for older women at increased risk of heart-related illness, according to a new University of Leeds research. In this study, high-intensity interval exercise was more beneficial than moderate-intensity workouts for boosting angiogenesis. More intense workouts seem to improve how existing cells involved in angiogenesis function whereas moderate-intensity exercise does not. So, increasing the intensity of a workout may be more effective for forming new capillaries around muscles than a more moderate pace. In turn, this is favorable for metabolic health.
Need more motivation to pick up the pace? Research also shows a link between having more angiogenic cells and a lower risk of developing cardiovascular disease. This partially explains why the risk of cardiovascular disease goes up after menopause. You have fewer angiogenic cells for forming new blood vessels and this contributes to insulin resistance, a risk factor for cardiovascular disease.
How More Angiogenic Cells Reduce the Risk of Cardiovascular Disease
Menopause has several negative effects on cardiovascular health. The decline in estrogen worsens endothelial function, how blood vessels respond to stress. Plus, the number of circulating angiogenic cells falls. There’s another reason the latter is important. Cells involved in angiogenesis do “damage control.” If the inner wall of a blood vessel is damaged, angiogenic cells travel to the area and release factors, like growth factors and cytokines, that help repair the wall of the vessel. Having the ability to repair this damage protects against heart attacks and strokes.
Worsening endothelial function after menopause also increases the risk of cardiovascular disease. If you combine poor endothelial function with other factors such as elevated blood pressure and abnormal blood lipids, the risk goes up even more. Obesity also increases the risk since fat cells produce inflammatory chemicals that damage the inner walls of blood vessels.
How to Lower Your Risk of Cardiovascular Disease after Menopause
Keep your heart healthy after menopause by staying physically active and by adding more interval training to your exercise routine, as it appears to be more effective for preserving angiogenesis. Also, monitor other risk factors that increase your risk of cardiovascular disease by checking your blood pressure regularly and keeping it in a healthy range. It’s important to control your blood sugar and lipids levels through lifestyle and medications when necessary. A combination of a healthy lifestyle and interval exercise will go far toward keeping your heart healthy after menopause.
References:
- com. “Blood vessel growth in muscle is reduced in women after menopause”
- Faculty of Science – University of Copenhagen. “Blood vessel growth in muscle is reduced in women after menopause.” ScienceDaily. ScienceDaily, 22 September 2020.
- com. “Interval workouts for older women may improve health of blood vessels”
- Harris E, Rakobowchuk M, Birch KMInterval exercise increases angiogenic cell function in postmenopausal womenBMJ Open Sport & Exercise Medicine 2017;3:e000248. doi: 10.1136/bmjsem-2017-000248.
- J Clin Endocrinol Metab. 2012 Dec; 97(12): 4692–4700.Published online 2012 Sep 11. doi: 10.1210/jc.2012-2244.
- May-Jun 2007;14(3 Pt 1):373-84. doi: 10.1097/GME.0b013e31803c764d.
- May-Jun 2008;15(3):414-21. doi: 10.1097/gme.0b013e318154b6f5.
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