Exercise reigns supreme when it comes to safeguarding mental and physical health. Moving on a frequent basis can ignite a cascade of positive physiological and psychological benefits, like relieving stress, building muscle, burning calories, and staving off disease.
Until now, researchers hypothesized that many of those benefits leveled off with high amounts of physical activity. However, in a recent study, which tracked over 90,000 people for five years, researchers discovered the limits of exercise's positive effects don't exist – at least when it comes to heart health. Study participants who exercised the most had no upper threshold of cardiovascular benefit.
While you can generally overdo it on the treadmill or overextend yourself in the gym, this study suggests more exercise is better. These sweeping findings were published Tuesday in the journal PLOS Medicine
The science of workouts — In typical exercise studies, researchers rely on participants to recall their levels of physical activity in surveys or apps. This self-reporting method is notoriously inaccurate.
In this new study, scientists took a more fine-grained approach, recruiting 90,211 people through the UK Biobank to wear an accelerometer for one week to measure their physical activity. The UK Biobank is a large-scale biomedical database and population-based study.
Accelerometers are small lightweight motion sensors worn on the wrist designed to accurately capture physical activity from charging up the stairs to taking a spin class. The researchers analyzed exercise by intensity, frequency, and duration. The exact exercise participants engaged in wasn't specified — just that there were working up a sweat.
After wearing the accelerometers for the designated period, researchers tracked the group's cardiovascular health for an average of 5.2 years. They also collected data on their eating, drinking, and smoking habits, body mass indices, cholesterol, and other biometrics. At the start of the study, the group had no history of cardiovascular diseases like heart attacks or stroke.
What was discovered — Over five years, 3,617 cases of cardiovascular disease were diagnosed in the group.
But across the board, the higher someone's physical activity, the better their cardiovascular health. People in every increasing quartile of physical activity, for moderate-intensity activity, vigorous-intensity activity, and total physical activity, were less likely to have cardiovascular disease.
"Increasing the amount of physical activity up to quite high levels provides an increasing benefit in terms of cardiovascular disease prevention."
Compared to those who exercised the least, those who engaged in moderate-intensity exercise were 71 percent as likely to be diagnosed with cardiovascular disease. Those one quartile up were 59 percent as likely while those who exercised most intensely were 46 percent as likely to be diagnosed with cardiovascular disease.
"Increasing the amount of physical activity up to quite high levels provides an increasing benefit in terms of cardiovascular disease prevention," study co-author Terence Dwyer tells Inverse. Dwyer is a non-communicable disease epidemiologist at the University of Oxford.
The results are "not surprising in concept," Dwyer explains. What is surprising is how this result differs from past research: Other studies, especially those that rely on questionnaires, suggest there are limited benefits associated with very high levels of exercise.
Importantly, the team found high levels of exercise were not associated with a higher risk of having a heart attack or stroke.
Participants in the lowest category of physical activity also smoked more, had higher body mass index and C-reactive protein, and were most often diagnosed with hypertension — factors that could have also jeopardized their cardiovascular health.
The big picture — Exercise enhances cardiovascular health more than previously thought, suggests this study.
The findings add weight to the recently updated World Health Organization physical activity guidelines recommending at least 150 to 300 minutes of moderate to vigorous aerobic activity per week for all adults.
During the global pandemic that has many of us sitting, getting enough exercise may be more important than ever.
"Because of lockdowns or self-imposed isolation, people have not been getting as much ‘incidental’ activity, particularly in relation to travel or movement around an office," Dwyer explains. They aren't commuting to work or hopping out for dinner as frequently.
This means people need to take "more purposeful activity" to reach their activity goals, Dwyer says.
"Our findings should give them more confidence that this is something they really should pay attention to," Dwyer says.
"It also should provide confidence in increasing their physical activity beyond levels they might have regularly taken prior to the pandemic, if they would like to do that."
Background: Higher levels of physical activity (PA) are associated with a lower risk of cardiovascular disease (CVD). However, uncertainty exists on whether the inverse relationship between PA and incidence of CVD is greater at the highest levels of PA. Past studies have mostly relied on self-reported evidence from questionnaire-based PA, which is crude and cannot capture all PA undertaken. We investigated the association between accelerometer-measured moderate, vigorous, and total PA and incident CVD.
Methods and findings: We obtained accelerometer-measured moderate-intensity and vigorous-intensity physical activities and total volume of PA, over a 7-day period in 2013–2015, for 90,211 participants without prior or concurrent CVD in the UK Biobank cohort. Participants in the lowest category of total PA smoked more, had higher body mass index and C-reactive protein, and were diagnosed with hypertension. PA was associated with 3,617 incident CVD cases during 440,004 person-years of follow-up (median (interquartile range [IQR]): 5.2 (1.2) years) using Cox regression models. We found a linear dose-response relationship for PA, whether measured as moderate-intensity, vigorous-intensity, or as total volume, with risk of incident of CVD. Hazard ratios (HRs) and 95% confidence intervals for increasing quarters of the PA distribution relative to the lowest fourth were for moderate-intensity PA: 0.71 (0.65, 0.77), 0.59 (0.54, 0.65), and 0.46 (0.41, 0.51); for vigorous-intensity PA: 0.70 (0.64, 0.77), 0.54 (0.49,0.59), and 0.41 (0.37,0.46); and for total volume of PA: 0.73 (0.67, 0.79), 0.63 (0.57, 0.69), and 0.47 (0.43, 0.52). We took account of potential confounders but unmeasured confounding remains a possibility, and while removal of early deaths did not affect the estimated HRs, we cannot completely dismiss the likelihood that reverse causality has contributed to the findings. Another possible limitation of this work is the quantification of PA intensity-levels based on methods validated in relatively small studies.
Conclusions: In this study, we found no evidence of a threshold for the inverse association between objectively measured moderate, vigorous, and total PA with CVD. Our findings suggest that PA is not only associated with lower risk for of CVD, but the greatest benefit is seen for those who are active at the highest level.