Muscles are made up of thousands of fibres, and if they are overstretched or torn the result can be pretty painful. The medical term is muscle strain, and it’s an extremely common sports injury, often occurring during sudden, explosive movements such as sprinting or jumping. The force can cause tissues to tear, partially or completely, and the recovery time depends on the severity of the damage.
Doctors classify muscle strains into three grades, ranging from mild (less than five per cent of fibres affected) to severe strain, which has completely torn the muscle all the way through and usually requires surgery.