In this study we will investigate the effects of a high-impact exercise program involving
jumping on bone mass (the amount of bone) of the hip and backbone in the growing skeleton.
We will also look at the effects of gradually stopping the jumping program on bone mass in
the growing skeleton. A high-impact exercise program may build more bone during childhood,
while the skeleton is still growing. This may help prevent broken bones due to loss of bone
mass later in life.
We will recruit 200 children aged 5-10 to participate in the study. For 6 months we will
train the children in either a jumping or stretching program. We will then gradually reduce
the amount of exercise over 6 months. We will measure bone mass in the hip and backbone at
the start of the study, after jumping, and 6 months after the jumping program is stopped. We
will compare the results in the jumping and stretching groups.
Osteoporotic fractures are increasing at an alarming rate in this country and result in over
13 billion dollars in health costs annually. Peak bone mass, that is, an individual's
maximum bone mass at the completion of skeletal acquisition, is an important determinant of
fracture risk. Thus, maximizing peak bone mass may provide an effective strategy for
preventing osteopenia and osteoporosis.
Various investigators have postulated that increasing bone mass by 3-5 percent would reduce
fracture risk by 20-30 percent. Our data in collegiate female gymnasts demonstrate hip and
spine bone mineral density values of up to 40 percent above values in normal age-matched
controls and elite runners, despite menstrual irregularities. Further, we have observed the
dynamic response of bone to high-impact forces in gymnasts over the training season as bone
increases of 2-5 percent.
This is a randomized, controlled exercise intervention designed to evaluate the effect of
high-impact loading as a means to increase bone mass during development. It will determine
bone mass accrual and bone geometry at the lumbar spine and proximal femur in prepubescent
girls and boys. Further, this study will evaluate the bone response from withdrawal of the
stimulus over 6 months.
We will recruit 200 pre-pubescent children during two separate years and randomly assign
them to a jumping or a stretching group. The jumping group will perform double leg jumps and
the stretching group will act as a control. Outcome variables include bone mineral density
(BMD) at the spine and hip, estimated bone volumetric density at the spine, and
cross-sectional geometry of the femoral neck and diaphysis.
Implementing a specific bone-loading program during childhood will potentially allow the
bone to increase both its mass and mineralization at an earlier age and therefore provide a
larger foundation of mineralization for further growth throughout adolescence until skeletal
maturity is reached. We expect our findings to provide a basis for the design of strategies
to build bone during growth and thereby reduce osteoporotic fractures.
- Apparently healthy boys and girls
- BMI < 30kg/m2
- BMI < 30kg/m2
- Orthopedic problems that would limit physical participation
- Metabolic diseases that would influence bone metabolism