Medical Compass: Why should we exercise?
Obscenely short intervals of exercise can still generate significant benefit
By David Dunaief, M.D.
What better way to start an article than with a pretest?
1) What minimum amount of exercise will reduce cardiovascular disease risk?
a. 5 to 10 minutes per day b. 30 minutes most days c. 60 minutes most days d. I don’t care — I don’t like pretests
2) How does inactivity affect menopausal symptoms?
a. Increases hot flashes b. Worsens risk of anxiety and depressive moods c. Decreases memory and concentration d. B and C
3) Exercise may have an impact on the following: a. Changing gene expression b. Metabolic aging c. Weight management d. All of the above
With all that’s been written about exercise in the past few years, I’ll bet you did well. The answers to the quiz are: 1) a, 2) d, 3) d. Before we go further, let’s differentiate between physical activity and exercise. Physical activity involves skeletal muscle contraction. It’s an umbrella term that includes exercise, but it also includes housework, yard work, movement on the job, etc. Exercise involves repetitive movements, structure and goal orientation such as walking, running, resistance training or playing sports (1). While you want to be physically active, exercise has more benefit.
We have long-held paradigms in medicine that may or may not be accurate. Medicine is always changing with the evolution of evidence-based research. We know that exercise has benefits for helping to prevent and possibly reverse some chronic diseases, but it also may have benefit for menopausal symptoms, slowing the metabolic aging process and even changing our genes, or at least gene expression.
The Fountain of Youth
Ponce de León sought a physical fountain of youth. While we tend to chuckle at that thought, metaphorically there may be at least some truth to the mythical fountain. Exercise may be a step toward reversing the metabolic clock. Until recently, we thought that when we hit 40 years old, we should expect a decline in physical abilities, with each passing year raising the probability of greater muscle atrophy. This may not actually be the case. Just because a paradigm has been around a long time does not make it correct.
In a small observational study, results showed that the participants, spanning ages 55 to 79, were unable to be differentiated based on age for the majority of tests (2). In other words, those who were in their 70s performed similarly to those in their 50s for many, but not all, parameters. It would be impossible to tell who was what age based purely on the data.
Participants were also compared to standards related to typical aging in each group, such as comparing 70-year-old cyclists versus inactive 70-year-olds. The ones who were cyclists were metabolically much younger. Thus, the researchers concluded that activity, rather than chronological age, may play a more important role in the aging process. The cyclists were not professional athletes, though they were required to pass a cycling endurance test prior to being accepted into the study. To at least some degree, we are more in control of our aging than we had thought. This is good news; we would all like to turn back the physical clock.
Can we really change our genes?
One of the greatest achievements of modern medicine has been mapping the human genome. However, gene therapy mostly has lagged. Well, there is a field called epigenetics. This word literally means “above” or “on” the gene. Epigenetics explores how to alter which of our genes get expressed and how. How can we do this? Methyl groups, one of the most basic groups of atoms in organic chemistry, latch on to genes and help to turn on and off their expression. Lifestyle modifications, like exercise, influence methylation groups to affect genes.
In a small study, results showed greater than 5,000 alterations in the genes of muscle cells such that there were different patterns of methyl groups that occurred in exercised legs compared to inactive legs (3). The genes that were affected are known to be involved in insulin sensitivity and inflammation. Let me explain further.
The researchers had 23 healthy volunteers use a stationary bike for 40 minutes, four times a day, for three months. Here is the catch: Participants only used one leg and did not exercise the other leg, limiting confounding variables. In the same participant, the leg that was exercised had dramatic changes in gene expression, whereas the other leg did not.
How can exercise elongate cell life?
In another study, exercise appeared to prevent or reduce the risk of shortened telomeres. Telomeres are important for protecting the DNA and, ultimately, the cell (4). There were four different categories of exercises surveyed. If respondents said yes to each category, there was an exponentially greater chance that they would not have very short telomeres.
The categories included walking, running, walking/riding a bike to work or school and weight lifting. When a participant was involved in one category in the previous month, there was a 3 percent reduced risk of shorter telomeres, whereas participants who were involved in all four categories had a 59 percent reduced risk of having very short telomeres. This greatest impact was seen in adults between ages 40 and 65.
Although menopause is a rite of passage for women, not a disorder, there are symptoms that may negatively impact quality of life. Exercise may help alleviate menopausal symptoms. In a study, women who exercised regularly (resistance training twice weekly, plus either 150 minutes weekly of moderate activity, like walking, or 75 minutes weekly of intense exercise, like jogging or running) had a better overall sense of well-being and fewer symptoms during menopause compared to their less active counterparts (5). Those who were less active were more likely to be in depressed/anxious moods, have “brain fog,” difficulties with memory and concentration and experience increased vasomotor symptoms. Interestingly though, there was no change in hot flashes between the two groups.
I don’t have time to exercise!
There have been several studies that have shown that you can have obscenely short intervals of exercise and still get significant benefit. In one study, a one-minute intensive interval was broken into 20-second intervals within 10 minutes of exercise three times a week (6). Overweight participants had improved blood pressure and endurance capacity, as well as beneficial gains among other parameters.
In another study, as little as five to 10 minutes of running a day reduced the risk of dying from any cause by 30 percent and dying from heart disease by 45 percent (7). The best part of the results was that there was a significant difference between runners and nonrunners, but not between those who ran at a less-than-six-minute-mile pace and those who ran at a slower-than-10-minute-mile pace.
References: (1) uptodate.com. (2) J Physiol. online Jan. 6, 2015. (3) Epigenetics. Dec. 7, 2014. (4) Med Sci Sports Exerc. 2015;47(11):2347-2352. (5) Maturitas. 2015 Jan;80(1):69-74. (6) PLoS One. 2014;9(11):e111489. (7) J Am Coll Cardiol. 2014;64(5):472-481.
Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, visit www.medicalcompassmd.com or consult your personal physician.