Effects of physical exercise on bone mass, balance skill and aerobic capacity in women and men with low bone mineral density, after one year of training--a prospective study

Abstract

Vadstena is a small community in the county of Ostergötland, Sweden, where a project began in 1989 to prevent osteoporosis and to lower the expected incidence of osteoporotic fractures. Persons aged 40-70 years who had a low bone mineral density (BMD) value at screening of the distal radius by single-photon absorptiometry (SPA) were invited to participate in a training study during one year. The definition of low BMD was a densitometry value below -1 SD (standard deviation) from a sex- and age-specific reference value (z-score). Fifteen persons wanted to exercise in a group and 15 persons wanted to become a control group. All participants answered a questionnaire about lifestyle, occupation, diseases, medication and heredity. Clinical tests were made regarding mobility of the joints and muscles, balance and physical fitness. BMD for the hip and the lumbar spine were assessed by dual-energy X-ray absorptiometry (DXA) before and after the investigation period. The training programme was carried out for 60 min twice a week during one year and had the intention to improve bone mass, muscle strength and flexibility, balance skill and aerobic capacity. After the training period there was a significant increase in BMD at the greater trochanter (P < 0.01), in balance skill (standing on one leg with closed eyes and "ski step"-test) (P < 0.05) and in oxygen uptake capacity (P < 0.05) in the exercise group. In the control group, there was a significant increase in BMD at the lumbar spine (P < 0.05). However, these results should be judged with caution because several participants were over the age of 60, and at that age degenerative changes in the lumbar spine may increase to a greater or lesser extent. Regular weight-bearing exercises during one year seem to influence BMD at the greater trochanter in a training group comprising both women and men. However, our study was small in number and further training studies are needed to assess the effect of weight-bearing training on bone mass in different sex- and age-specific groups.