Kids’ grip strength is improving, but other measures of muscle fitness are getting worse

Beatrice J. Doty

(The Conversation is an independent and nonprofit source of news, analysis and commentary from academic experts.)

Grant R. Tomkinson, University of North Dakota and Justin J. Lang, L’Université d’Ottawa/University of Ottawa

(THE CONVERSATION) Physical fitness in kids refers to their ability to perform physical activity. Their fitness level is not only important for success in sports and athletics, but also for good health.

Aerobic fitness – the ability to supply oxygen to the body’s big muscles during continuous physical activities, such as running, biking or swimming – has long been known as important to health in kids as well as adults. Muscle fitness refers to the ability of the muscles to produce force maximally, quickly and repeatedly – otherwise known as strength, power and endurance.

Research on the health benefits of muscle fitness for children and adolescents has increased significantly in the past decade. One systematic review of this research found that low muscle fitness was associated with high body fat, poor bone health and low self-esteem, as well as a high risk of developing heart disease in later life.

Findings like these are why both the World Health Organization and U.S. Department of Health and Human Services now recommend that kids aged 5 to 17 years participate in muscle- and bone-strengthening activities at least three days a week.


We are a professor of kinesiology and an epidemiologist who conduct research that focuses on physical fitness and health. In 2019, our research team published a study that compiled more than 30 years of aerobic fitness data on 1 million kids from 19 high- and upper-middle-income countries such as Australia, Canada and the United States. We found that the aerobic fitness of kids in these countries significantly declined from 1981 to about 2000, with little change ever since.

This research got us wondering: Has kids’ muscle fitness also declined? So we decided to take a look at that as well.

The muscle fitness of today’s kids

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