Female Runners LegsThere is plenty of evidence to suggest that weight bearing exercise can have a positive effect on bone density and strength. But when and how much exercise is necessary and what type is the most appropriate?

Whilst exercise while young positively affects peak bone mass, exercise during adulthood can maintain bone mass and can potentially prevent women from osteoporosis.

In particular, impact exercise that induces high strains at high rates in the bone has been found to promote bone strength.

Research published in November’s BMC Musculoskeletal Disorders, studied how bone changes over time during a 12 month course of exercise.

The aim was to evaluate the association between exercise intensity at 3, 6 and 12 month intervals and changes  in the Bone Mineral Density (BMD) of the femur (thigh bone), during high-impact exercise in premenopausal women.


  • The subjects were 35 healthy women (age 35-40 years, average BMI of 25.5). Before the study began they were not participating in impact-type exercises or long-distance running more than three times a week.
  • Accelerometers, (portable, cheap, light-weight machines, worn on the waist) were used to continuously measure daily physical activity.
  • The subjects were supervised during a 60-minute training workout, consisting of a warm-up period, high-impact training and a cool-down period. The progressive high-impact period included versatile movements, such as step aerobic patterns, stamping, jumping, and running, three times a week for 12 months.
  • The programs were modified bimonthly to become progressively more demanding by including higher jumps and drops.
  • The participants were also given a home program (10 min daily), which consisted of patterns of exercise similar to those in the supervised sessions.
  • The BMD of the femur, and the trochanters (the projections from the femur where the hip and thigh muscles attach), were measured using x-ray absorptiometry and activity data was correlated with changes in bone density.

The researchers from Finland found that the average daily number of high impacts during six months of training was significantly associated with 12-month positive BMD changes at the femoral neck and trochanter area.

These results agreed with many previous studies, in which only five to six months of high-impact exercise were needed to increase BMD in the femoral neck and trochanter and the greatest changes were seen on this time period, than during 12 or 18month interventions.

Lead author Riikka Ahola, suggests these results provide new information for designing optimal and feasible training programs that can prevent bone loss in premenopausal women

Because bone cells adapt to regular loading, one important feature that the researchers recommend is for an exercise program to be progressive. ‘A progressive exercise program sustains overload and the bone adaptation process. ‘

‘Loads should be increased with time to produce a sufficient stimulus. An exercise program that maintains the same loading for many years would stimulate bone formation only during the first months of training.’

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