They are only aged 9 and 7, but they already have bodies that would put the Incredible Hulk to shame.
Meet the young Stroe brothers - a pair of Romanian brothers dubbed in the media as the 'world's strongest boys'.
Giuliano and Claudiu Stroe have been weightlifting since they were just two-years-old. Their father Iulian Stroe, 35, puts them through a gruelling 2-hour fitness regimen every day, but says that his sons enjoy it.
According to reports, older brother Giuliano has already set world records for number of "air push-ups" - doing push-ups without letting the feet touch the ground - and hand walking - walking on the hands with weights between the legs.
"He has been going to the gym with me ever since he was born. I always took him with me when I went training," his father told an Italian paper.
His father has told the media that his son's workout schedules aren't excessive and the child is never allowed to practice on his own. "If he gets tired, we go out and play," The NY Daily News quoted him as saying.
"They have a natural ability for this, nothing is forced, it is what God intended for them," their mother told The Daily Mail UK.
According to UK publications, the boys' fitness routine involves heavy weights such as 4kg dumbbells to build up their muscles. They have been featured in Romania's version of 'Britain's Got Talent', where Giuliano wowed the audience with feats such as standing on one hand and performing several back flips.
He also took off his shirt to show off his amazingly fit body.
Healthy or harmful?
According to vice.com, the Romanian equivalent of child services expressed concern about the children undergoing such intensive weight training, but released the boys back to their father after a neurologist signed a document declaring Giuliano as being "well developed from a psychomotor point of view."
However, the neurologist clarified to vice.com that the boy not having an mental illnesses does not mean she agrees with the intensive workouts his father pushes them to perform.
According to Mayo Clinic, strength training may provide health benefits to young chlidren, but weightlifting or powerlifting - where participants try to lift the heaviest weight possible - may be too much for young children - whose muscles, tendons and areas of cartilage have not fully developed.
The American Academy of Pediatrics (AAP) recommends that children reach the ages of 7 or 8 before they start strength training, due to the time needed for a child's balance and postural control skills to mature to adult levels.
"Preadolescents and adolescents should avoid power lifting, body building, and maximal lifts until they reach physical and skeletal maturity," AAP said.