Kirsche Elms, from Tarring, said her 11-year-old son would love to use the facility in Shaftesbury Avenue with his friends after school.
She said: “It’s on our doorstep. It’s perfect, the kids can come out of school and go straight to the leisure centre. They can socialise in the cafe.
“It’s a safe place, it’s not down the park with an aerosol can or antisocial behaviour.
“It’s getting them off their games consoles and getting them fit, giving them confidence, setting themselves goals and boosting them a bit.”
She said it was a ‘no brainer’ that the admission policy should be changed – but said her suggestion had not been implemented by the leisure centre.
“It’s so frustrating,” she said. “There isn’t actually a reason why they can’t offer this to our youngsters.
“I can’t see what the issue is. I think it’s a no brainer.”
The nurse, who works at St Barnabas House, pointed out that Lancing Manor Leisure Centre allows young people aged 11 and above to use the gym in the presence of qualified staff following a one hour induction.
She said: “I think it’s ridiculous, how come they can do it there and can’t do it at our local one?”
While she said she understood young people would not be able to use weights, she said her son would enjoy using the treadmill and cycle machine.
She said she believed the change in policy would benefit both the mental and physical health of young people in the area.
“Knowing that such a large proportion of our youngsters are overweight, they should be doing everything they can to allow kids to use their facilities,” said Mrs Elms, who also has a nine-year-old daughter.
“It’s everyone’s responsibility.”
Duncan Anderson, chief executive of South Downs Leisure which runs Worthing Leisure Centre, said: “We have decided not to allow the use of the gym from the age of 11 after benchmarking across the industry, looking at health advice around under 13’s training with weights and there is also the fact that some of the equipment is just not suitable for children at such a young age.
“It is never going to be an exact science and suppliers will not put a height, weight or age restriction on the kit, as you can have an adult who is 4ft tall and a 10-year-old who is 5ft tall.
“Similarly, weight and physical maturity variations make it impossible to be totally prescriptive.
“We therefore end up with an arbitrary number like 13 which seems pretty standard across the country.
“It would be difficult to say 11 or 12-year-olds can use a treadmill but not a leg press, for example, especially when sessions are mixed.
“The more compelling argument is that you could potentially have, say, a very physically immature 11-year-old who really is at risk of affecting their bone growth if they trained using weights.
“Impulse take 11/12-year-olds and will have risk assessed this, however we have many other courses and lessons which are all part of our Junior membership package.”