Aim  To determine whether the bone mass of young people with Down syndrome may increase, following a 21-week conditioning training programme including plyometric jumps.

Method  Twenty-eight participants with Down syndrome (13 females, 15 males) aged 10 to 19 years were divided into exercise (DS-E; n=14; eight females, six males mean age 13y 8mo, SD 2y 6mo) and non-exercise (DS-NE; n=14; five females, nine males mean age 15y 5mo, SD 2y 6mo) groups. Total and regional (hip and lumbar spine [L1–L4]) bone mineral content (BMC) and total lean mass were assessed by dual energy X-ray absorptiometry at baseline and after a 25-minute training session performed twice a week. Repeated-measures analyses of variation were applied to test differences between pre- and posttraining values for BMC and total lean mass. Differences between increments were studied with the Student’s t-test. Linear regression models were fitted to test independent relationships.

Results  After the intervention, higher increments in total and hip BMC, and total lean mass, were observed in the DS-E group (all p<0.05). A time×exercise interaction was found for total lean mass (p<0.05). The increment in total lean mass, height, and Tanner stage accounted for almost for 60% in the increment in total BMC in the DS-NE group (p<0.05).

Interpretation  Twenty-one weeks of training have a positive effect on the acquisition of bone mass in young people with Down syndrome.