Dr Marnee McKay and Prof Joshua Burns at University of Sydney's Faculty of Health Sciences have found that there is no statistical difference in the capabilities of girls and boys until around the age of 12.
As part of wider research to assess people’s physical capabilities across the lifespan, they tested 300 children and adolescents between the ages of 3 and 19.
Each child was tested for over two hours, taking more than 100 measurements. These included measuring the strength of 14 muscle groups, the flexibility of 13 joints and 10 different types of balance, as well as factors such as hand dexterity, reaction times, how far they could walk, how high and how long they could jump, as well as their gait.
Across all measures of physical performance there was one consistent finding, there was no statistical difference in the capabilities of girls and boys until high-school age (commonly age 12).
Using the standing long jump (also known as a broad jump test) as an example, which provides a measure of your legs’ explosive power. It needs minimal equipment and the results compare well with the type of information you get from strength testing using expensive equipment.
There was no difference found between boys and girls before they turn 12. Every physical measure followed this pattern. Before the age of 12, boys and girls do just as well as each other in the standing long jump.
The findings support the push for boys and girls to compete in mixed sporting teams until the end of primary school, after which the hormonal changes of puberty mean boys tend to perform better in sports and tasks requiring strength and speed. [SOURCE]