Exercise and Metabolism

Exercise carries many positive effects on a person's metabolic state. Regular exercise helps to lower the oxidative stress in the body, to repair damaged endothelial cells, and to proliferate neural stem cells. Acute exercise plays a role in tissue repair and vasculogenesis, and may play a role in repairing damaged heart tissues.

Aerobic Exercise

Aerobic exercise refers to exercise that generates energy through aerobic processes, such as distance running or calisthenics. Aerobic exercise carries benefits on endothelial function, which is important for the prevention of cardiovascular disease.

Cardiovascular effects

Aerobic exercise helps to prevent decline in endothelial vasodilation as adults age.1

A study in 68 healthy men 22 to 35 or 50 to 76 years of age, showed that forearem blood flow (FBF - a measure of the flow rate of blood; higher rates are better) as well as forced vital capacity (FVC - the maximum amount of air that can be exhaled by the lung after inhalation) decrease with age. However, it was found that individuals who engaged in aerobic exercise in the form of running, for several years (7±2 years for the younger group and 20±2 years for the older group), exhibited lesser declines in FBF and FVC.1

aerobic_exercise_FBF_FVC

Aerobic exercise has been shown to increase forearm blood flow (FBF) as well as forced vital capcity (FVC) in the lungs.

Furthermore, various studies have shown that regular aerobic exercise can carry additional benefits for endothelial function including an increased effect of nitric oxide, which is important for vasodilation.2Increased effects of nitric oxide induced vasodilation have been found in both healthy adults as well as adults with hyperlipidemia.3

Aerobic exercise is beneficial for patients with thrombosis, or narrowing of the arteries due to plaque formation.4In particular, exercise was found to significantly reduce unscheduled hospital visits for worsening angina (20.2% vs. 27.2%, P < 0.0001).5

Diabetes

A meta-analysis of 8,538 patients showed that exercise was effective in lowering hemoglobin A1c levels in diabetic patients. In the analysis, it was found that engagement in over 150 minutes of exercise per week was associated with HbA(1c) reductions of 0.89%, compared with HbA(1C) reductions of 0.36% for those engaging in exercise of less than 150 minutes per week.6

Lipid Levels

Lowering lipid levels is essential for decreasing one's risk of heart attacks, and is also essential for revascularization of tissues after stroke.7A meta-analysis of 788 individuals from 6 studies showed that a combination of diet and exercise was effective in lowering total cholesterol levels, low-density lipoprotein cholesterol (LDL), and triglyceride levels. On the other hand, exercise alone was effective in lowering triglyercide levels only.8

Another meta-analysis has shown that decreasing the levels of LDL cholesterol in an individual, even by as little as 2.5 mmol/L, can lead to 4.6% improvement in the vascular death rate on the population level.

lower_ldl_prevent_vascular_death

Resistance Training

Resistance training refers to weight-bearing forms of exercise. This can take place in many ways including powerlifting, olympic weightlifting, barbell lifts, dumbbell lifts and compound exercises such as CrossFit.

For most optimal effects, resistance training can be done multiple times per week (up to 4-5 separate workouts) but there should be adequate amounts of rest in order for recovery to occur.

Resistance training breaks down muscle fibers, and muscle fibers recover and heal during periods of resting. During the healing phase, the muscle fibers undergo hypertrophy, which refers to an increase in size of the cells.9Muscle fiber breakdown is measured by the marker creatine kinase (CK).

Growth Factors

Resistance training increases levels of important growth factors in the body. Studies have shown correlations between resistance training and levels of brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), and insulin-like growth factor-1 (IGF-1).

A study involving 11 healthy human subjects found that resistance training led to increased levels of insulin-like growth factor-1 (IGF-1), which plays a role in skeletal muscle fiber growth and maintenance. In this particular study, after 3 repetitions of a load-bearing exercise, one group of participants exhibited a 28% increase in serum IGF-1 levels. A separate group exhibited an increase of 16% after a stronger level of resistance exercise was done.10

A study involving 56 young men showed that resistance training induced various hormone responses including acute increases in serum growth hormone (GH), free testosterone, insulin-like growth factor (IGF-1) and cortisol. These rises in hormones were also correlated with rises in lean body mass as well as type 2 muscle fiber cross-sectional area, which are crucial to general health and metabolism.11In this study, participants did a 12-week long resistance training program; they did not engage in regular weightlifting activity for a period of 8 months before starting the study.

In a study involving young healthy females, resistance training was demonstrated to lower the levels of C-reactive protein, which is an inflammatory biomarker associated with oxidative stress.12

A study involving older men with an average of 68, shown that engaging in resistance training consisting of 3 sets of 10 repetitions of the leg press, hack squat and leg extension lifts, resulted in significantly lower levels of myostatin after 24 hours post-exercise.13Myostatin is a negative regulator of muscle growth, and generally it is better to maintain lower levels of myostatin in order to preserve lean muscle tissue for metabolic purpose.

resistance_training_myostatin

Resistance training has been shown to lead to decreased levels of myostatin. This is of particular importance to older individuals in order to preserve lean muscle tissue.

In a study involving 25 subjects, it was found that 8 weeks of resistance training led to significant increases in cell signaling in the WNT pathway, which is involved in autocrine and paracrine signaling for prevention of proteolysis (protein breakdown). A group of 10 participants participated in high intensity squats program, which involves squatting the highest load possible (labeled strength training, ST), while 10 participants participated in medium intensity squat program, where they squatted a percentage of their maximum possible load (labeled power training, PT). A separate control group of 5 participants did not engage in resistance training.14

resistance_training_beta_catenin Power training leads to increases in levels of beta catenin, which plays a role in preventing protein breakdown. PT: power training - squatting a percentage of the maximum 1-repetition load, ST: strength training - squatting the maximum 1-repetition load.

resistance_training_cyclin Strength training leads to increases in levels of Cyclin D1, which plays a role in cell cycle regulation for diseases such as cancers. The participant group that engaged in power training (PT - squatting a percentage of the 1-repetition maximum load) exhibited the greatest increase in cyclin levels.

  1. DeSouza, C. A., Shapiro, L. F., Clevenger, C. M., Dinenno, F. A., Monahan, K. D., Tanaka, H., & Seals, D. R. (2000). Regular aerobic exercise prevents and restores age-related declines in endothelium-dependent vasodilation in healthy men. Circulation, 102(12), 1351-1357.

  2. Green, D. J., Maiorana, A., O'Driscoll, G., & Taylor, R. (2004). Effect of exercise training on endothelium‐derived nitric oxide function in humans. The Journal of physiology, 561(1), 1-25.

  3. Walsh, J. H., Yong, G., Cheetham, C., Watts, G. F., O’Driscoll, G. J., Taylor, R. R., & Green, D. J. (2003). Effects of exercise training on conduit and resistance vessel function in treated and untreated hypercholesterolaemic subjects. European heart journal, 24(18), 1681-1689.

  4. Fiuza-Luces, C., Garatachea, N., Berger, N. A., & Lucia, A. (2013). Exercise is the real polypill. Physiology, 28(5), 330-358.

  5. Soga, Y., Yokoi, H., Amemiya, K., Iwabuchi, M., & Nobuyoshi, M. (2011). Safety and efficacy of exercise training after coronary stenting in patients with stable coronary artery disease. Circulation Journal, 75(10), 2379-2386.

  6. Umpierre, D., Ribeiro, P. A., Kramer, C. K., Leitão, C. B., Zucatti, A. T., Azevedo, M. J., ... & Schaan, B. D. (2011). Physical activity advice only or structured exercise training and association with HbA1c levels in type 2 diabetes: a systematic review and meta-analysis. Jama, 305(17), 1790-1799.

  7. Trialists, C. T. (2012). The effects of lowering LDL cholesterol with statin therapy in people at low risk of vascular disease: meta-analysis of individual data from 27 randomised trials. The Lancet, 380(9841), 581-590.

  8. Kelley, G. A., Kelley, K. S., Roberts, S., & Haskell, W. (2012). Comparison of aerobic exercise, diet or both on lipids and lipoproteins in adults: a meta-analysis of randomized controlled trials. Clinical nutrition, 31(2), 156-167.

  9. Flann, K. L., LaStayo, P. C., McClain, D. A., Hazel, M., & Lindstedt, S. L. (2011). Muscle damage and muscle remodeling: no pain, no gain?. The Journal of experimental biology, 214(4), 674-679.

  10. Rojas, V. S., Knicker, A., Hollmann, W., Bloch, W., & Strüder, H. K. (2010). Effect of resistance exercise on serum levels of growth factors in humans. Hormone and metabolic research= Hormon-und Stoffwechselforschung= Hormones et metabolisme, 42(13), 982-986.

  11. West, D. W., & Phillips, S. M. (2012). Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training. European journal of applied physiology, 112(7), 2693-2702.

  12. Daray, L. A., Henagan, T. M., Zanovec, M., Earnest, C. P., Johnson, L. G., Winchester, J., ... & Stewart, L. K. (2011). Endurance and resistance training lowers C-reactive protein in young, healthy females. Applied Physiology, Nutrition, and Metabolism, 36(5), 660-670.

  13. Dalbo, V. J., Roberts, M. D., Sunderland, K. L., Poole, C. N., Stout, J. R., Beck, T. W., ... & Kerksick, C. M. (2011). Acute loading and aging effects on myostatin pathway biomarkers in human skeletal muscle after three sequential bouts of resistance exercise. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 66(8), 855-865.

  14. Leal, M. L., Lamas, L., Aoki, M. S., Ugrinowitsch, C., Ramos, M. S. C., Tricoli, V., & Moriscot, A. S. (2011). Effect of different resistance-training regimens on the WNT-signaling pathway. European journal of applied physiology, 111(10), 2535-2545.

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