Boys aged 9-12 years, with a history of facture will be asked to stand on one of two vibrating platforms for 10 minutes on 5 consecutive days. The investigators will take blood samples before and after the vibration to measure changes in the bone cells.

Fractures in children are common, accounting for 10% of attendances in Accident and Emergency Departments. Research into risk factors for fracture has found that children who have narrower bones and a low bone mass are more likely to fracture than children with larger bones. Studies in postmenopausal women, young women with low bone mass and children with disabling conditions such as cerebral palsy, have shown that up to 10 minutes a day stood on a vibrating platform can significantly increase bone mass.

However little is known of the immediate response of bone to whole body vibration (WBV). The investigators previously investigated the acute bone response in healthy pre-pubertal boys to standing on one of two vibrating platforms for 10 minutes on 1, 3 or 5 consecutive days. This showed a platform dependent reduction in the bone resorption marker CTx pre to post vibration, with an increase in the bone formation marker P1NP over the 8 day study. The investigators would like to look at the response of bone to WBV in pre-pubertal boys who have a history of fracture(s). The investigators will compare this to the investigator's previous data to determine if bone in boys who have previously fractured responds in the same way as bone in boys who have not.

The investigators plan to recruit 24 boys aged 9-12 years who have had a previous fracture to stand on one of two vibrating platforms for 10 minutes on 5 consecutive days. Before and after the period of vibration on days 1, 3, 5, and on days 8 and 12 the investigators will take a blood sample to measure changes in the bone cells. The boys will be asked about the amount of exercise they have participated in over the previous seven days. The findings of this study will be used to direct further research.

Inclusion Criteria:

• Caucasian
• Aged 7-13yrs (pre-pubertal)
• First language English
• History of one or more fracture(s)

Exclusion Criteria:

• Pre-existing chronic illness
• Known bone disease
• Current or healing fracture
• Recent (last 12 months) or current treatment likely to affect bone - this does not include inhaled or intermittent oral therapy with steroids for asthma
• Balance problems
• Continuing involvement in more than one other research study