The equipment, made by Hong Kong company Torpedo Sport, includes an exercise bike, a treadmill and a cross-trainer walking machine called an 'air walker'. Each item is priced at 80.

Concerned experts told the Sunday Tribune that exercising with what is essentially scaleddown adult gym equipment could be damaging to both the social and physical development of the child.

Nuala Collins, a leading dietitian and nutrition consultant, said: "There is absolutely no need for special equipment. Children should be out in the fresh air. A skipping rope or a 1.99 hula hoop is enough. . .

"It is totally unnecessary for parents to be considering buying these things for children."

"Exercise should be had through play, outdoors, " agreed child psychotherapist Colman Noctor. "Children need to learn the social rules of play, and providing exercise in isolation at home loses that."

The equipment, which is made in China, claims to offer "hyperactive solutions", and is currently on sale in Dunnes Stores outlets. The treadmill includes a computer monitor which oversees speed, time and distance run, as well as a 'calories scan'. It "offers simulation of uphill running" and, according to the makers, is "built to satisfy children's choice of home exercise equipment."

Parenting author Dr John Sharry said that the use of such equipment could lead to children having issues with their body image at a very young age: "[there is a] danger of being over-attentive to children. Calorie counters could make children worried about their weight. Children should naturally get their exercise through playing outside and walking to school. . . You don't want them to be hyped up and worried about it. Young girls at younger and younger ages are getting worried about their image to an obsessive amount."

Noctor said that the existence of such equipment could encourage parents to counteract bad dietary practices by buying a gym for their young child, "If parents don't have time to invest in playing with their children, buying equipment for your child is playing to one's own conscience, " he said. "If you invest in your child's diet in the first place, that mightn't be necessary.

"Regarding the physical development of toddlers, lots carry puppy fat which remedies itself.

Parents seem to be over-anxious about the weight issue, but children at that age don't complain about their weight, it's a parental issue.

Even adults find treadmills boring . . . I would imagine a child would find it incredibly frustrating. . . it encourages children to 'play adults'.

If mummy is on the treadmill at night in front of the plasma TV, they want to get up beside her."

Chartered physiotherapist and personal trainer Philip Phelan said that although advances in technology offer alternative and sometimes useful methods of exercising, such equipment may not be appropriate for infants. "With younger exercisers, the concern would be that it would be putting strain on young bodies that aren't developed, " he said. "Four years of age is too young for that. Psychologically and otherwise, general play is what they need.

"You don't want to produce children who are insular, working on their own in a quiet room. It is too young, there are other things they should be exploring first."

"I'm just surprised, " said dietitian Collins of the Dunnes equipment, adding that there was "no justification" for the sale of such items. "I'm really surprised you can actually get them in Dunnes. If you told me you could get them in America, I would think 'what's next?', but I'm very surprised they are for sale in Ireland."

The Sunday Tribunemade every effort to contact Dunnes Stores this weekend, but received no response.