Are children getting weaker?

“A shift away from traditional activities like climbing trees, ropes and wall bars has made modern 10-year-olds physically weaker than their counterparts a decade ago,” reported The Daily Telegraph.

The news report is based on research comparing various measures of strength in about 300 children aged 10 in 1998, with a sample of 10-year-olds in 2008. The 2008 children performed poorer in a handgrip test, which is a test of upper body strength, and could complete less sit-ups in 30 seconds compared to the 1998 samples. However, they were better at standing long jumps - a test of lower body strength.

The researchers say these findings show a decline in many, but not all, measures of muscular fitness in these children between 1998 and 2008.

The newspapers quoted the researchers as suggesting that the decline could be due to children spending less time playing outside climbing trees and participating in other physical activities, and spending more time indoors. However, this is speculation as the research did not look at behaviour trends between 1998 and 2008 or determine whether there was any link between children’s play activities and the observed decline in muscular strength in some tests. It is also unknown if these results apply to the rest of the UK, as the study was only in 300 children from the same area.

These findings should be treated as preliminary and further studies are needed.

Where did the story come from?

The study was carried out by researchers from London Metropolitan University and The University of Essex. This research was funded by Sport Chelmsford. The study was published in the peer-reviewed medical journal Acta Paediatricia .

The newspapers reported the main findings of the study and also speculated on why there may be a decrease in muscle strength in children over the past 10 years. However, the reasons for the trend were not assessed in this research.

None of the newspapers mentioned that not all of the measures of strength had found poorer performance in the 2008 group compared to the 1998 group. There was also no mention of the fact that national trends cannot be determined from this sample of 300 children taken from one area of England.

What kind of research was this?

This was an interrupted time series study that looked at records of muscular fitness in a sample of 10 year olds in 1998 and compared them with those from a sample of children of the same age and from the same area and type of schools in 2008.

The researchers said that poor muscle strength in childhood is associated with a poor metabolism during adolescence and an increased risk of disease in adulthood. They said that studies in children from other European countries have shown a reduction in children’s strength over time, but there has been a lack of studies showing recent trends in muscular fitness in English children. The aim of this study was to investigate changes in muscular fitness in 10 year old children over a 10-year period.

What did the research involve?

In 1998, 309 children aged between 10 and 10.9 were recruited from a random sample of schools in Chelmsford, Essex. Another group of 315 children, who were the same age in 2008, were recruited from five schools and matched for size and socio- economic status to those selected in 1998. In both samples, there were approximately equal numbers of girls and boys.

The researchers measured the children’s mass and stature. The children’s lower body strength was measured using standardised tests (a standing long jump test). Their handgrip strength was taken as a measure of their maximum upper body strength. Upper body strength endurance was measured by how long the children could hang from a bar with bent arms. Hip and trunk muscular endurance was measured by seeing how many sit-ups the children could do in 30 seconds.

What were the basic results?

The researchers found that there was no difference between the 1998 sample and the 2008 sample in stature, mass or BMI.

The 2008 group could jump further on the standing long jump test, jumping on average 7cm further. However, on all of the other tests, the 2008 sample performed poorer than the 1998 group. For example, the 2008 group on average could do seven less sit-ups in 30 seconds, and could do the bent arm hang for 4.6 fewer seconds.

These results retained their statistical significance when the researchers took into account differences between the children in stature, mass and BMI.

How did the researchers interpret the results?

The researchers say their study showed decline over time in most, but not all measures of muscular fitness in English children between 1998 and 2008. They say it is puzzling why the children’s results on the standing long jump were better in 2008 but their handgrip results were worse. They say that both measures are accepted indicators of health in children and it is difficult to assess the overall impact of this anomaly.

Despite this, they say their findings ‘highlight the importance of monitoring components of muscular fitness in youth, and a need to emphasise the development of muscular as well as cardio-respiratory fitness’.

Conclusion

This study compared performance at some tests of strength between 10-year-old children in 1998 with those in 2008. The findings showed a decrease in ability in most of the tests.
 
The samples were relatively small with only 300 children assessed in either period, but may give an indication of trends in England that warrant further follow up. The study had several other limitations that the researchers highlight.

• The children in the two samples had similar BMIs. However, the researchers say that no measurements of composition were taken (how much muscle and how much fat the children had). This means that even though the two groups of children had similar BMI (which reflects weight relative to height) some of the children may have had less muscle mass but more fat, which contributed to their weight and therefore also their BMI.
• No evaluation was made of whether the children had started to go through puberty, and this may have differed between the two samples potentially affecting the results. However, the researchers say that this is unlikely as the children in the two samples had similar statures.
• The samples were relatively small, and in 10-year-old children living in an affluent area of the UK. The researchers say these trends observed here may therefore not be applicable to the population as a whole or to different socioeconomic groups.

The newspapers have tended to focus on reasons why the decline in some aspects of muscle strength may have occurred. They say the decline could be due to children spending less time playing outside climbing trees and spending more time on social networking sites and playing computer games.

However, this is just speculation as the research did not look at behaviour trends between 1998 and 2008 or determine whether there was any link between children’s play activities and the observed decline in muscular strength in some tests. As the study was only in 300 children from the same area, it is also unknown if these results apply to the rest of the UK.

This study’s findings should be treated as preliminary. Further studies are needed to fully understand the trends in muscular strength in young children, why these have occurred and what can be advised to promote children to do activities that help them to develop good muscular strength.