More than half of American children lack cardiorespiratory fitness

By Angela Betsaida B. Laguipo, BSNJul 20 2020

A new study strengthens the claim that children today are not as healthy as those decades ago. In fact, the study by researchers on behalf of the American Heart Association (AHA) has found that nearly 60 percent of American children do not have healthy cardiorespiratory fitness (CRF), a key measure of physical fitness and overall health.

Published in the journal Circulation, the study highlights the declining levels of cardiorespiratory fitness among children and youth, which may be a key predictor of future health outcomes.

Study: Cardiorespiratory Fitness in Youth: An Important Marker of Health: A Scientific Statement From the American Heart Association. Image Credit: Sirtravelalot / Shutterstock

What is cardiorespiratory fitness?

Cardiorespiratory fitness (CRF) defines the ability of the body to deliver oxygen from the atmosphere to the skeletal muscles and to use it to produce the energy needed during physical activity. Put simply, cardiorespiratory fitness shows how aerobically fit a person is and how effectively the circulatory system sends oxygen throughout the body.

Low levels of CRF is a strong predictor of cardiovascular disease (CVD) and all-cause mortality in adults. Further, CRF is a predictor of various indicators, including premature CVD, cardiometabolic health, mental health, and even academic achievement.

In the United States, only 40 percent of children between 12 and 15 years old are believed to have a healthy CRF, and over the past 60 years, CRF levels have dropped worldwide. Some of the reasons for the decline of CRF levels in the United States and internationally, including being sedentary, obesity, social and economic changes, and decreased levels of moderate to vigorous physical activity.

"CRF is a single measure that shows how strong the heart, lungs, and blood circulation are in children. Whereas measuring body weight, blood pressure, cholesterol and blood sugar levels tell us about each of these individual risk factors, measuring CRF provides a comprehensive assessment of a child's overall health," Dr. Geetha Raghuveer,  chair of the writing committee for the new scientific statement, said in a statement.

CRF and children's health

Children and adolescents today do not get the adequate amount of exercise and physical activity needed to live a healthy adult life. The World Health Organization (WHO) reports that childhood obesity is one of the most serious public health challenges today.

In 2016, the number of overweight children under 5 years had increased to 41 million. These children are more likely to stay obese into adulthood and develop a multitude of chronic diseases such as diabetes and cardiovascular disease.

One of the most significant contributors to low CRF in children is the drop in physical activity as fewer children are physically active. Many children today are exercising less and opt to stay indoors with their gadgets, rather than playing outside. Though children are more sedentary now than they were in the past, it is not clear if a sedentary lifestyle or the lack of physical activity is tied to lower CRF in young people.

Some of the diseases in children and youth can be assessed through the CRF, including asthma, congenital heart disease, and cystic fibrosis, among others. CRF is also used as an objective measure of health that can be monitored and tracked over time and compared across populations.

Considered a vital sign

CRF will provide an accurate measure of the overall health status of children and adolescents. In the past, researchers relied on self-reported physical activity levels, which can be unreliable. CRF, on the other hand, provides a more robust measure of cardiovascular health.

The American Heath Association (AHA) suggests that CRF be considered as a vital sign since it can help predict mortality in adults akin to traditionally assessed risk factors, including type 2 diabetes mellitus, hypertension, cigarette smoking, and hypercholesterolemia.

"Cardiorespiratory fitness is crucial for good heart and overall health both in childhood and as children become adults," Raghuveer said.

"We've got to get kids moving and engaged in regular physical activity, such as in any sports they enjoy. The best activity is the activity a child or teen likes, and that is sustained for a longer period. The habits they learn when they're young will directly benefit their health as they become adults," he added.

Challenges in children

There are many problems faced by parents who want their children to be more physically active. For instance, factors such as socioeconomic status, neighborhood characteristics, and social determinants of health can affect why children exercise less. Some of the factors include the lack of a safe place for children to exercise and play sports.

Further, many countries do not include physical education in their curriculum, and some families are below the poverty line, who cannot afford healthier food options.

"Healthy CRF is positively associated with cardiovascular health, academic achievement, and mental well-being in youth. Accurately and reliably measured CRF may identify youth who would benefit from lifestyle interventions but may be missed by subjective physical activity recall, anthropometric measures, or CVD risk factor testing, which are current standards of care," the researchers concluded the study.