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The long-standing debate over cardio and weights seems like yet another wedge to divide us in these polarized times. How can marathoners and muscleheads live together when each is convinced that the other is neglecting a crucial path to health and longevity?

Happily, the latest data suggests that there’s a middle ground. At the American College of Sports Medicine’s annual conference, held earlier this month in Denver, a comparison of the health benefits of aerobic and muscle-strengthening physical activity was selected as one of the top papers of the year. Its conclusions, in brief, are that each form of exercise is good and both is better.

The paper – published in Current Sports Medicine Reports and authored by Angelique Brellenthin and Duck-chul Lee of Iowa State University and Australian researcher Jason Bennie – assessed the long-term impacts of meeting standard exercise guidelines. The Canadian Society for Exercise Physiology’s 24-Hour Movement Guidelines, for example, suggest accumulating at least 150 minutes per week of moderate to vigorous aerobic activity, along with muscle-strengthening activity at least twice a week.

Those who meet just the aerobic guidelines tend to live three to four years longer than those who don’t, Dr. Brellenthin and her colleagues point out.

But there has been far less research on the health-related effects of strength training. We know it makes you stronger – but there’s also evidence that it may provide some of the more general benefits that aerobic exercise provides, like better heart health and lower cancer risk.

Overall, large-scale epidemiological studies suggest that meeting only the aerobic exercise guidelines lowers your risk of premature death from any cause by 15 to 35 per cent. Meeting only the strength training guidelines lowers risk by 10 to 25 per cent. Meeting both benchmarks lowers risk by 30 to 45 per cent.

Other types of evidence, including studies where subjects are randomized to follow different exercise programs, reach broadly similar conclusions. Strength training, even on its own, is good. Aerobic exercise is a little better. Both is best.

On the surface, these findings might seem so blandly obvious that they’re not even worth mentioning. But there’s some history here.

Back in 2012, Dr. Lee presented an analysis of more than 50,000 patients who had undergone fitness testing at Dallas’s famous Cooper Clinic between 1971 and 2002. Those who ran as little as 5 to 10 minutes per day lived longer, as expected. But those who ran more than 32 kilometres a week, Dr. Lee suggested, were no better off than those who didn’t run at all.

Those findings helped kick off a contentious debate about the putative risks of too much aerobic exercise, fuelling headlines like “One Running Shoe in the Grave.” But drawing conclusions from large epidemiological studies like this requires making assumptions about the characteristics of the subjects, and some researchers worried that these statistical manipulations might have skewed the results.

In 2019, Dr. Lee – himself a former bodybuilder and Mr. Korea aspirant – published another analysis of the Cooper Clinic data, this time looking at strength training. As with running, he found that even small amounts of strength training improved longevity. But the apparent sweet spot was just two strength training workouts a week, with the health benefits reversed if you train four times a week. Dr. Lee himself acknowledged that this finding about the dangers of pumping iron more than twice a week seemed implausible, and – perhaps in consequence – he no longer argues that too much aerobic exercise is dangerous either.

The new review, then, can be seen as a sign of détente between the cardio and weights camps. There are still some unanswered questions. For example, the apparent superiority of doing both cardio and weights might simply be a result of the fact that those who do both tend to do more exercise overall.

But that seems unlikely. As Dr. Brellenthin points out, cardio and weights have different health effects. Cardio is better at improving heart health, circulation, and cholesterol levels. Weights have stronger effects on basal metabolism and blood sugar control. The only wrong answer in this debate is picking sides in the first place.

Alex Hutchinson is the author of Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance. Follow him on Twitter @sweatscience.

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