TOO much exercise each week could be as bad for teenagers as too little, research has suggested.
A study found the maximum benefit from taking part in sport seemed to be gained from about 14 hours each week – double the recommended level of seven hours for teenagers.
But the researchers, writing in the medical journal Archives of Disease in Childhood, found that doing more than 17 hours a week could be detrimental to young people’s wellbeing.
Physical exercise is widely linked to creating positive effects such as reducing the risk of depression, stress and anxiety and improving self-esteem and mental function in children and teenagers.
In contrast, inactivity has been linked to an increased risk of psychological disorders.
While exercising for more than seven hours is supposed to improve health and wellbeing, exercising for prolonged periods is said to increase the risk of depression, irritability and anxiety.
The researchers, from Switzerland’s Institute of Social and Preventive Medicine in Lausanne, questioned more than 1,200 people aged 16 to 20 in Switzerland about how much sport they did.
Their mental and physical wellbeing was assessed using criteria used by the World Health Organisation, with each participant given a score from 0 to 25. A score below 13 indicates poor wellbeing.
The team said: “These results are all the more relevant when facing adolescents struggling with poor wellbeing and who have limited sport practice.
“Conversely, athletes suffering from poor wellbeing should be made aware that practising more than twice the recommended sport duration is actually an independent risk factor of their poorer physical and mental health.”
Half the participants were male, with an average age of 18. Some 9 per cent were classed as overweight or obese. The average wellbeing score for the whole group was 17.
The findings showed 35 per cent of the group had low sports participation at 0 to 3.5 hours a week, while 41.5 per cent were rated average with activity of between 3.6 and 10.5 hours a week.
There were 18.5 per cent with high levels of activity – between 10.6 and 17.5 hours – and 5 per cent were very high in the ratings with more than 17.5 hours of weekly activity.
The researchers found compared with the teenagers in the average group, those in the low and very high groups were more than twice as likely to score below 13 on the WHO wellbeing scale.
Those in the high group, however, were around 50 per cent less likely to score below 13 on the scale.
Tam Fry, from the Child Growth Foundation and National Obesity Forum, said the biggest problem was children and young people not getting enough exercise rather than having too much.
“Those who are getting more than 17 hours a week are probably body builders and muscle-bound men,” he said.
“The bigger issue is that many younger people are not getting much exercise at all.”
Mr Fry said that sedentary activities such as playing computer games and watching TV were often behind the lack of exercise young people were taking.