Seung Kim, M.S.
Do you exercise regularly? If so, what benefits do you expect from exercise? Ever wonder whether you’re exercising in appropriate ways? Except for few people who are addicted to exercise, the main reason most people spend time and money for exercise is to maintain/improve their health. In general, the benefits of exercise include health-related risk factor reduction, anti-aging effects, prevention/improvement of disease, etc.
However, there are things to carefully consider regarding advantages from exercise. Is exercise is beneficial for everyone? Are all types of exercise are beneficial? What if there are even potential adverse effects of exercise? Do all people respond to exercise the same way? These questions don’t have simple answers but research has shed some light.
About 20 years ago, a research endeavor called HERITAGE Family Study was initiated to find the genetic contributions to response to exercise training. This study provided a great deal of data supporting the idea that the response to exercise is genetically influenced and that a few individuals do not respond to exercise. Our lab (Exercise Genetics Laboratory, Texas A&M University) also found genetic differences in both intrinsic exercise capacity and response to endurance exercise, using an inbred mouse model. Now there is no doubt that the effect of exercise is regulated by genetic components. So, does genetic background influence the effect of exercise on any or all risk factors in the same manner? Maybe not. It 
seems that the genetic influences differ depending on the risk factor, i.e. the same exercise amount may reduce your body weight, but not that of your friend, and perhaps vice versa for blood pressure.
Among risk factors, impaired endothelial function (IEF) is one of the most common.The endothelium is the thin layer of cells lining the interior surfaces of blood vessels and is mainly responsible for controlling vessel plasticity. It means reduced ability of the vessel to enlarge its diameter and to prevent stickiness, causing high blood pressure and thus subsequent occurrence of several cardiovascular diseases. Thus numerous researchers have examined the effect of exercise on endothelial function and most of them propose that exercise can reverse or improve IEF.
Our lab recently conducted an experiment that aims to characterize the relationship between exercise intensity (moderate intensity constant and high intensity interval running) and genetic background in endothelial response to training in mice. Our results were not simple, i.e., in general, exercise improved or had no effect on IEF, but in some strains high intensity exercise made IEF worse. However, the results clearly demonstrate the interaction between genetic background and exercise intensity on the response to exercise. Our findings are further supported by recent work that assessed the genetic contribution to the effect of exercise on various health risk factors, such as blood pressure, heart rate, blood lipid, etc. Therefore factors besides genetic background such as exercise intensity and duration, diet, sleep habits, 
and so forth regulate the responses to exercise. Although the observations so far do not fully explain the genetic mechanisms regulating the effect of exercise on our health, more hints are arising.
The long-term purpose of research in this area is to provide appropriate and accurate guidance to maximize the beneficial effect of exercise individually. But for now, most people will benefit by following general recommendations. According to the American College of Sports Medicine in 2011, moderate intensity cardiorespiratory exercise training for ≥ 30 min/day on ≥ 5 days/week for a total ≥150 min/week with resistance exercises for each major muscle group and neuromotor exercises is recommended in order to maintain physical fitness for most adults in general. The responses to the exercise training recommended above might be different between you and your friends; but these recommendations seem to have the fewest adverse effects for most adults. Exercise training following these recommendations has been shown repeatedly to be much better than doing nothing. Moreover, there are other important factors, i.e. nutrition, habitual behavior, stress, etc., for maintaining a healthy lifestyle.
For further information related to this topic
- Wilmore JH, Despres JP, Stanforth PR, Mandel S, Rice T, Gagnon J, Leon AS, Rao DC, Skinner JS, Bouchard C. Alterations in body weight and composition consequent to 20 wk of endurance training: the HERITAGE Family Study. Am J Clin Nutr. 1999; 70(3):346-352.
- Courtney SM, Massett MP. Identification of exercise capacity QTL using association mapping in inbred mice. Physiol Genomics. 2012;44(19):948-955.
- Massett MP, Berk BC. Strain-dependent differences in responses to exercise training in inbred and hybrid mice. Am J Physiol Regul Integr Comp Physiol. 2005;288:R1006-R1013.
- Garber CE, Blissmer B, Deschenes MR, Franklin BA, Lamonte MJ, Lee IM, Nieman DC, Swain DP. Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory, Musculoskeletal, and Neuromotor Fitness in Apparently Healthy Adults: Guidance for Prescribing Exercise. Med Sci Sports Exerc. 2011;43(7):1334-1359.