Why 43 Minutes of Cardio a Day May Help Keep the Doctor Away

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For people in their 20s, 30s, 40s, and 50s, adhering to the minimum recommended guidelines of 2.5 hours of moderate-intensity physical activity per week may not be enough to offset the onset of hypertension in middle age, a new three-decade study reports.

Notably, the University of California, San Francisco researchers found that, on average, over the course of 30 years, study participants (N = 5,114) needed to do at least twice (5 hours) the "recommended dose" of moderate-intensity cardio per week in order for aerobic exercise to have a protective effect against high blood pressure. "Moderate physical activity levels may need to exceed current minimum guidelines to prevent hypertension onset," the authors note.

These findings (Nagata et al., 2021) on the link between someone's weekly dose of physical activity and his or her odds of developing hypertension between young adulthood and middle age were published on April 15 in the American Journal of Preventive Medicine.

"Results from randomized controlled trials and observational studies have shown that exercise lowers blood pressure, suggesting that it may be important to focus on exercise as a way to lower blood pressure in all adults as they approach middle age," senior author Kirsten Bibbins-Domingo of the UCSF Department of Epidemiology and Biostatistics said in a news release.

"Teenagers and those in their early 20s may be physically active, but these patterns change with age," she added. "Our study suggests that maintaining physical activity during young adulthood—at higher levels than previously recommended—may be particularly important."

Because the optimum physical activity dose needed to prevent hypertension from young adulthood to midlife has been unclear, this study set out to determine "the association between level and change in physical activity through the adult life course and the onset of hypertension."

150 minutes of physical activity per week (2.5 hours) may not protect against hypertension.

The baseline data for this 30-year study were collected from 1985–1986 at four urban sites. In the mid-1980s, study participants were between the ages of 18 and 30. Three decades later (2015–2016), follow-up data were collected. Of the 5,114 participants included in the sample for this study, 51.6 percent were Black women and men; in total, 45.5 percent of study participants were men and 54.5 percent were women.

At baseline, the data showed that nearly half of the study participants had suboptimal physical activity (PA) levels. On average, the data showed that from age 18 to 60 years, "physical activity was lowest among Black women than among other groups. Black men, on average, reported high levels of PA at age 18 years; however, the levels declined considerably from young adulthood to the end of middle age."

On average, physical activity levels for the white men in this study also declined when they were in their 20s and 30s but stabilized at around age 40. For white women, on average, physical activity levels tended to dip slightly in their 30s but remained constant to age 60.

"Although Black male youth may have high engagement in sports, socioeconomic factors, neighborhood environments, and work or family responsibilities may prevent continued engagement in physical activity through adulthood," first author Jason Nagata of the UCSF Division of Adolescent and Young Adult Medicine said in the news release. "Additionally, Black men reported the highest rates of smoking, which may preclude physical activity over time."

5 hours per week (43 minutes daily) of moderate-intensity exercise may reduce hypertension risk as we age.

The researchers found that study participants who had consistently exercised for at least five hours a week (double the recommended minimum) during early adulthood were 18 percent less likely to develop hypertension in midlife than those who exercised for less than five hours a week. "The likelihood was even lower for the 11.7 percent of participants who maintained their exercise habits until age 60," the authors note.

Based on these findings, the researchers conclude:

"The annual reduction of physical activity is more strongly associated with hypertension onset than physical activity level at age 18 years. This suggests the need to emphasize, prioritize, and fund interventions to promote physical activity early in life to prevent the development of hypertension in later adulthood."

"Nearly half of our participants in young adulthood had suboptimal levels of physical activity, which was significantly associated with the onset of hypertension, indicating that we need to raise the minimum standard for physical activity," Nagata concludes. "This might be especially the case after high school when opportunities for physical activity diminish as young adults transition to college, the workforce, and parenthood, and leisure time is eroded."

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Take-Home Advice: Increasing weekly activity may help keep blood pressure low, but cardio workouts aren't a magic bullet.

Although 300 minutes of moderate-intensity physical activity per week is correlated with a lower risk of developing hypertension, aerobic exercise (in and of itself) is not a magic bullet or panacea.

As always, staying healthy across one's lifespan requires taking a multi-pronged approach that includes eating a nutritious diet, not smoking, and adopting other daily habits that promote well-being, such as tackling new challenges with gusto, having a sense of purpose or raison d'être, staying intellectually curious, and maintaining close-knit social bonds.

DISCLAIMER: This blog post is not intended as medical advice. Please use common sense and consult with your doctor before beginning any new exercise regimen—especially if you're an older adult who hasn't stayed consistently physically active since young adulthood.

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