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

(INTERVIEW) Children’s physical fitness refers to their ability to engage in physical activity. Their fitness is important for success in sports and athletics, as well as good health.

Aerobic fitness – the ability to supply oxygen to large muscles in the body during ongoing physical activities such as running, cycling or swimming – is well known to be important for the health of both children and adults. Muscle fitness refers to the ability to build muscle strength as quickly as possible, over and over again – otherwise known as strength, power, and endurance.

Research on the benefits of muscle fitness for children and adolescents has increased significantly in the last decade. A systematic review of this study 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 heart disease later in life.

Because of such findings, the World Health Organization and the U.S. Department of Health and Human Services recommend that children ages 5 to 17 participate in muscle and bone strengthening activities at least three days a week.


We are a professor of kinesiology and an epidemiologist who conducts research focusing on physical fitness and health. In 2019, our research team published a study that included data on over 30 years of aerobic fitness from 1 million children in 19 high- and middle-income countries, including Australia, Canada, and the United States. We saw that the aerobic season of children in these countries decreased significantly from 1981 to about 2000, and there have been few changes since then.

This study questioned us: has children’s muscle health also declined? So we decided to take a look at that as well.

The muscle season of today’s children

Our research team has reviewed hundreds of studies. Tens of millions of children between the ages of 9 and 17 had decades of data on muscle fitness, mostly from high- and middle-income countries. Measurements of grip strength, long standing jumps have been based on measurements of leg strength and abdominal endurance measurements, as researchers around the world are the most common ways to measure children’s muscle mass.

We have found that in most of these countries the strength of the flu has been progressively improving since the 60s. We also found that leg strength and abdominal endurance improved by the year 2000 and then decreased.

So it seems that today’s children were stronger than their parents and grandparents when they were younger. Leg strength and abdominal endurance are better than those of grandparents, but the same or worse than their parents.

What is the cause?

To explain these findings, our research team examined several national trends in each country, including muscle fitness, physical activity, body size, and income inequality.

We found no significant link between seasonal muscle trends and tendencies, body size, or income difference. Our research showed that the countries with the greatest decline in physical activity were the ones with the greatest decline in leg strength and abdominal endurance. For example, levels of physical activity and abdominal endurance have recently declined in children in Slovakia, Switzerland and the UK. On the other hand, both have recently grown up with children from Poland, Slovenia and Spain.

This suggests that children’s muscle fitness could be improved by increasing their level of physical activity, as well as by obtaining guidelines for physical activity recommended by the U.S. government. In the case of school-age children and adolescents, it is to perform 60 minutes or more a day of moderate or high-intensity aerobic activity, along with muscle and bone strengthening activities at least three days a week.

This is especially important during the COVID-19 pandemic, as blockades appear to have significantly reduced children’s physical condition. For example, the physical condition of Slovenian children fell by 13% to a 30-year low after only two months of self-isolation.

Children get a number of benefits during the muscle season

According to more and more research, children of all ages can benefit from properly supervised endurance training. Recent research on endurance training among children and adolescents has shown that it improves muscle fitness, body composition, athletic performance, self-confidence, and self-esteem. It takes at least three sessions a week to build muscle mass lasting more than 30 minutes and continuous weight gain.

While there may be fear among parents that these activities are not safe for growing children, research also shows that participating in a properly supervised resistance training program does not hinder children’s growth or damage plaques that are growing.

Improving muscle fitness makes it easier for any child to move and lift things and do sports. Our research suggests that resistance training can especially benefit overweight and obese teens who are reluctant or incapable of doing aerobic activities. In another study we published in 2014, we found that six-month supervised resistance workouts made teenage boys who were overweight and obese stronger and more confident in physical exercise.

What can children do to improve muscle fitness?

Muscles become increasingly strong with weight or “resistance” when doing physical activity. Exercises that cause a muscle or group of muscles to contract against external resistance, such as a barbell, exercise band, or one’s own body weight.

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Although often done in the gym, endurance training can be done anywhere using a variety of activities and equipment. Jumping, climbing on playground equipment, push-ups, squats, weightlifting and yoga are high-weight activities.

As muscle fitness improves, children may try to increase the time or difficulty of their favorite physical activity or do the activities more often.

This article was published under The Creative Commons license under a Creative Commons license. Read the original article here: https://theconversation.com/kids-grip-strength-is-improving-but-other-measures-of-muscle-fitness-are-getting-worse-164295.