A seven-year physical activity intervention for children increased gains in bone mass and muscle strength.
OBJECTIVE
This study evaluated the musculoskeletal effects of increased physical activity on children, starting at six to nine years of age.


METHODS
In one school we increased the physical education of 72 girls and 100 boys to 200 minutes per week over seven years. In three other schools, 45 girls and 47 boys continued to receive 60 minutes per week. We measured areal bone mineral density (aBMD) with dual energy X-ray absorptiometry and muscle strength with computerised dynamometer at baseline and after seven years and tibial cortical thickness with peripheral quantitative computed tomography after seven years.


RESULTS
Girls in the intervention group gained 0.04 g/cm(2) (0.01-0.08) more total spine aBMD (p < 0.05) and 6.2Nm (1.6, 10.7) more knee flexion strength (p < 0.01) than control group girls and had a 0.1 mm (0.0, 0.3) higher tibial cortical thickness at follow-up (p < 0.05). Boys in the intervention group gained 7.3Nm (0.4, 14.2) more knee extension strength (p < 0.05) and 7.4Nm (2.3, 12.4) more knee flexion strength (p < 0.01) than the control group boys, but their aBMD was no higher than the control group.


CONCLUSIONS
A seven-year, population-based moderately intense exercise intervention enhanced gains in spine bone mass in girls and knee muscle strength in both genders.
Clinical and Molecular Osteoporosis Research Unit, Department of Orthopedics and Clinical Sciences, Lund University, Skåne University Hospital, Malmö, Sweden. jesper.fritz@med.lu.se.
Jesper
J
Fritz
Clinical and Molecular Osteoporosis Research Unit, Department of Orthopedics and Clinical Sciences, Lund University, Skåne University Hospital, Malmö, Sweden.
Björn E
BE
Rosengren
Clinical and Molecular Osteoporosis Research Unit, Department of Orthopedics and Clinical Sciences, Lund University, Skåne University Hospital, Malmö, Sweden.
Magnus
M
Dencker
Clinical and Molecular Osteoporosis Research Unit, Department of Orthopedics and Clinical Sciences, Lund University, Skåne University Hospital, Malmö, Sweden.
Caroline
C
Karlsson
Clinical and Molecular Osteoporosis Research Unit, Department of Orthopedics and Clinical Sciences, Lund University, Skåne University Hospital, Malmö, Sweden.
Magnus K
MK
Karlsson
D015519:Bone Density; D002648:Child; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D053580:Muscle Strength; D010024:Osteoporosis / Q000517:prevention & control*; D064797:Physical Conditioning, Human / Q000502:physiology*
Bone mineral content; Bone mineral density; Children; Muscle strength; Physical activity