More young teens now training in gyms, experts urge caution

A growing number of children aged 12–14 in Denmark are using commercial gyms, with over one in ten now engaging in weight training, according to a new report from the University of Southern Denmark (SDU). While experts welcome the trend, they advise parents to monitor their children’s approach to fitness.

The SDU report, mapping physical activity among 3–14-year-olds, shows a sharp increase in gym use among early teens. Only 6% of 9–11-year-olds use commercial fitness facilities, compared to more than 10% of 12–14-year-olds.

Casper Søndenbroe, a postdoctoral researcher in healthy ageing at the University of Copenhagen, and Malene Radmer Johannisson, senior consultant at Anti Doping Denmark, both highlight the benefits of strength training for young people. However, they stress that parents should be aware of potential risks.

Focus on personal progress, not comparisons

Johannisson warns that young gym-goers may feel pressured when surrounded by older, more experienced lifters—or by unrealistic body standards on social media.

“Parents need to help children understand that they shouldn’t compare themselves to adults, whether online or in the gym,” she says. “They should focus on their own development and perhaps compare with peers their own age.”

Proper technique and age-appropriate training

Unlike team sports, gyms rarely provide direct supervision, increasing the risk of improper technique. Søndenbroe emphasises the importance of correct form, gradual progression, and appropriate weight selection.

Johannisson adds that while social media can offer training inspiration, many programs are designed for adults—some even for advanced bodybuilders—and are unsuitable for young beginners.

Set realistic goals

Unlike competitive sports, gym training often revolves around aesthetic or strength goals. Johannisson advises parents to discuss their child’s motivations and ensure expectations align with their age and physical development.

“If the goal is to change their body, are those expectations realistic for their age and starting point? And do they understand the time it takes?” she asks.