How Does a Lifetime of Regular Exercise Slow Aging?

Staying physically active across the human lifespan appears to help people defy the aging process on a variety of levels that include keeping the immune system “young,” according to a new study by scientists at King’s College London and the University of Birmingham. The findings of this research were published in two separate papers in the April 2018 issue of Aging Cell. 

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The goal of this research was to identify specific biomarkers that could be used to gauge how a lifetime of regular exercise might slow the aging process. Countless studies have correlated regular physical activity with so-called “superagers,” who have significantly lower rates of morbidity, less dementia, and increased longevity in comparison to the general population. However, until now, few studies have done a deep dive into the nitty-gritty physiology and immunity that makes a lifetime of regular exercise akin to tapping the fountain of youth.

For this study, the researchers recruited 125 amateur cyclists (84 men, 41 women) between the ages of 55-79. All of these “master” cyclists were in good shape and could bicycle upwards of 36 miles at a stretch. They also recruited two “non-exercise” cohorts which consisted of 75 healthy older adults (ages 57 to 80) and 55 healthy younger adults (ages 20 to 36).

Although the non-exercise groups did not perform aerobic exercise on a regular basis, the researchers purposely excluded heavy drinkers, cigarette smokers, those with high blood pressure, and people with other health conditions. Therefore, the only significant lifestyle difference between the various cohorts was those who consistently engaged in aerobic exercise and those who did not.

All study participants underwent a series of laboratory tests to gauge lean muscle mass, muscular strength, percentage body fat, immunity profiles, and cholesterol levels. Male participants had their testosterone levels evaluated. Then, the amateur cyclists’ lab results were compared to the lab results of older and younger adults who had consistently led more sedentary lives and did not exercise regularly.

As would be expected, the master cyclists maintained lean muscle mass and physical strength as they aged. On the flip side, older adults who were less physically active experienced muscular atrophy and were more prone to frailty. The master cyclists also maintained healthier percentages of body fat and good cholesterol levels.

Men who had stayed physically active across their lifespan had higher levels of testosterone in comparison to their more sedentary male counterparts. The researchers speculate that the correlation between higher testosterone levels in older age and a lifetime of physical activity suggests that regular aerobic exercise may help men avoid the equivalent of “male menopause.”

However, other studies have found that overtraining and too much aerobic exercise can prematurely lower testosterone levels. Therefore, we need more studies to help identify the ideal "dose-response" of physical activity intensity and duration at various stages of life as it relates to optimal testosterone levels. 

A Lifetime of Regular Exercise Keeps the Immune System "Youthful" 

Most surprising to the researchers was that a lifetime of regular exercise was linked to robust immunity that mirrored that of younger adults. Typically, a lymphoid organ that creates immunity T-cells called the “thymus” begins to shrink when people are in their early 20s. As the thymus gets smaller, it produces fewer immunity-boosting T cells.

Notably, the researchers found that older adults who had stayed physically active across their lifespans displayed larger thymuses and were still producing as many T cells as much younger study participants.

The authors explain the details of this phenomenon in the study abstract: “Compared with their less active counterparts, the cyclists had significantly higher serum levels of the thymoprotective cytokine IL-7 and lower IL-6, which promotes thymic atrophy. Cyclists also showed additional evidence of reduced immunesenescence, namely lower Th17 polarization and higher B regulatory cell frequency than inactive elders.”

You may be asking yourself: "Are older adults who exercise regularly staying active because they feel younger, or do they feel younger because they exercise regularly and stay active?" 

Senior author, Stephen Harridge, who is a professor of human and applied physiology at King's College London (KCL), addressed this chicken-or-the-egg question in a statement: "The findings emphasize the fact that the cyclists do not exercise because they are healthy, but that they are healthy because they have been exercising for such a large proportion of their lives. Their bodies have been allowed to age optimally, free from the problems usually caused by inactivity. Remove the activity and their health would likely deteriorate."

From a public health perspective, these findings are significant. Most people over the age of 65 do not meet the minimum recommendation of 150 minutes per week of moderate-to-vigorous physical activity (MVPA) and have two or more diseases. 

Despite these grim statistics, the researchers are optimistic that their latest research on the age-defying benefits of regular exercise can serve as a source of motivation for people of all ages and walks of life to start being more physically active. As a public health advocate and exercise aficionado, I ask: "Why not start exercising more right now or first thing tomorrow morning?"

"We hope these findings prevent the danger that, as a society, we accept that old age and disease are normal bedfellows and that the third age of man is something to be endured and not enjoyed,“ Niharika Arora Duggal of the University of Birmingham School of Immunity and Infection said in a statement.

The researchers emphasize that you don’t have to exercise anywhere near the physiological intensity of an elite-level athlete to reap the multiple physiological and immunity benefits of a lifetime of moderate-to-vigorous exercise.

Norman Lazarus and Ross Pollock of KCL offer some practical advice to younger readers in their closing statement, “Nearly everybody can partake in an exercise that is in keeping with their own physiological capabilities. Find an exercise that you enjoy in whatever environment that suits you and make a habit of physical activity. You will reap the rewards in later life by enjoying an independent and productive old age."

Hopefully, the latest research on the power of regular physical activity to slow the aging process will inspire those of you who are less active to start moving more. And, for those of you who consistently make aerobic exercise a part of your daily routine, this new research offers science-based evidence to keep doing what you're doing.