And those who are lazy see their performance in the classroom suffer.
It has long been known that physical fitness in childhood and teenage years is beneficial for both physical and mental well-being throughout life.
But a growing body of evidence suggests it may also play a key role in brain health and academic performance.
In a new study, published in the Journal of Paediatrics, researchers studied the influence of the different components of physical fitness on academic performance.
They looked at the influence of cardio-respiratory capacity, muscular strength, and motor ability.
Cardio-respiratory capacity is aerobic fitness – it reflects the heart and lungs’ capacity to supply the body with fuel and oxygen during exercise.
Motor ability refers to skills involving muscle control such as speed, agility and coordination.
Irene Esteban-Cornejo, of the Autonomous University of Madrid, said: ‘Because these physical fitness components are highly associated with each other, it is important to differentiate which physical fitness components are important in relation to academic performance.’
The study sample included more than 2,000 Spanish children and teenagers, aged from six to 18, with detailed information on physical fitness, body composition, and academic performance.
The researchers found cardio-respiratory capacity and motor ability, both independently and combined, were related to academic performance.
However, the link between academic performance and physical fitness was stronger for speed, agility and coordination.
In contrast, children and teenagers who weren’t as fit or dextrous had lower grades.
Muscular strength was not associated with academic performance.
Dr Esteban-Cornejo added: ‘Having high levels of cardio-respiratory and motor fitness may, to some extent, reduce the risk of school failure.’
As a result, she said efforts should be made to promote physical activities for children and teenagers in a bid to improve their grades.