Exercise is healthy. It is common knowledge. But how rigorous should this exercise be to really affect a person’s fitness level? And if you sit at your desk all day but still manage to get out and exercise, does that ruin your six, seven or eight hours of sedentary behavior?
These were the kind of questions Matthew Nayor and his team at Boston University School of Medicine wanted to answer in the largest study to date to understand the relationship between regular physical activity and a person’s physical fitness.
Their results, which appear in the European Heart Journal, come from a study of around 2,000 participants in the Framingham Heart Study. They found that moderate to vigorous exercise – more intense exercise than walking 10,000 steps a day, for example – dramatically improved a person’s fitness compared to milder forms of exercise.
“By making the link between various forms of habitual physical activity and detailed fitness measurements,” says Nayor, “we hope that our study will provide important information that can ultimately be used to improve physical fitness and overall health throughout life.”
Nayor, assistant professor of medicine at the BU School of Medicine, is also a cardiologist specializing in heart failure at Boston Medical Center, the BU’s primary teaching hospital and Boston city safety net hospital. In the following questions and answers, Nayor explains the results of the study and explains what people should know about exercise in relation to fitness.
People may see a study that finds moderate to vigorous activity is the best way to improve their fitness and think, isn’t that obvious? But your research is more specific, so can you tell us what surprised, or perhaps insightful, about your work?
Matthew Nayor: While there is plenty of evidence to support the health benefits of both physical activity and higher fitness levels, the actual links between the two are less well understood, especially in the general population (as opposed to athletes or those with specific medical Problems). Our study was designed to fill this gap, but we were also interested in answering a few specific questions.
At first we asked ourselves how different intensities of physical activity could lead to an improvement in body reactions at the beginning, in the middle and at the peak of the workout. We expected greater levels of moderate to vigorous physical activity, such as less exertion.
We weren’t sure whether the number of steps per day or less sedentary time would really affect peak fitness. We found that they were linked to higher fitness levels in our study group. These results were consistent across all categories of age, gender, and health status and confirmed the relevance of maintaining physical activity [throughout the day] for each.
Second, we asked how different combinations of the three activity measures contribute to peak fitness. Interestingly, we observed that people with above average steps per day or moderate to vigorous physical activity were above average regardless of how much time they spent sitting. So it seems that much of the negative effects of sedentary lifestyle on fitness can be offset by increased levels of activity and exercise.
Our third question was: Are newer physical activity habits more important than previous exercise habits in determining your current fitness level? Interestingly, we found that participants with high activity scores on one assessment and low scores on another assessment, performed eight years apart, had an equivalent fitness level regardless of whether the high score matched the fitness test or not. This suggests that there may be a “memory effect” of previous physical activity on current fitness levels.
Lots of people these days wear Fitbits or their Apple Watch to keep track of their daily steps and they may think, hey, I took 10,000 steps today! But it sounds like your research suggests that while walking is valuable, it’s not the same as exercise?
Well, I think we have to be a little careful with this interpretation. It is important to note that higher steps in our study were associated with higher fitness levels, which is particularly comforting for the elderly or those with conditions that prohibit higher exertion. There is also ample evidence from other studies that higher step counts are linked to a variety of beneficial health outcomes. So I don’t want to stop people from following their step numbers.
However, if your goal is to improve your fitness level or to slow down the inevitable loss of fitness that occurs with aging, then you should at least moderate exertion [through intentional exercise] is more than three times more efficient than just walking with a relatively low cadence.
Where is that line? When does exercise go from moderate to hard for people who are wondering if they are doing enough?
We have used definitions from previous studies that categorize a cadence of 60-99 steps / minute as low effort, while 100-129 steps / minute is generally considered moderate physical activity and more than 130 steps / minute is considered vigorous. These step counts may need to be a little higher for younger people. The physical activity guidelines for Americans recommend 150-300 minutes / week of moderate intensity or 75-150 minutes / week of intense intensity. However, this cap is really a guide to encourage people to exercise. In our study, we could not observe any evidence of a threshold above which higher activity is no longer associated with higher fitness.
Can you explain in more detail how the results of your study were achieved in the participants in the Framingham Heart Study?
Thank you for asking this question and for the opportunity to thank those who participated in the Framingham Heart Study. A course like ours is only possible through your voluntary work over three generations. For our study, we analyzed data from participants in the third generation cohort (in many cases, literally the grandchildren of the original participants) and the multiracial sample. During the last study visit in 2016–2019, we performed cardiopulmonary exercise tests (CPETs) on inpatient cycles for a comprehensive fitness assessment. CPETs are the “gold standard” for assessing fitness and include stress testing with a face mask or mouthpiece to measure inhaled oxygen and exhaled carbon dioxide during exercise. You may have seen professional endurance athletes (e.g. cyclists) perform similar tests during training sessions. Participants also took home accelerometers, which were worn on belts around the waist for eight days after their study visit. Accelerometers were worn on the last study visit and the previous visit eight years ago and the information was compared.
Source:
Journal reference:
Nayor, M., et al. (2021) Physical Activity and Fitness in the Community: The Framingham Heart Study. European heart journal. doi.org/10.1093/eurheartj/ehab580.
