The authors reported that 20 studies were included, though 21 studies appear to have been included in the analysis (n=1,626 approximately).
Two studies scored less than 30 on the validity scale, 14 studies scored between 30 and 40, and 5 studies scored between 40 and 45 points.
Evidence of an increase in BMD was found in 7 studies. A positive outcome was found for bone maintenance in the exercise group compared with a decline of BMD in the control groups (6 studies). Ground reaction forces and joint reaction forces resulted in increases in BMD (1 study), and sites exposed to both improved more than sites stressed by only ground reaction forces (3 studies). A study that allowed HRT and separated users into groups found that the groups using a combination of HRT and exercise produced greater increases in BMD in the exercise group than in the control group. No difference in BMD was found between the exercise group and control group in 3 studies.
Studies with a positive outcome, or that showed an increase in BMD, were over 11 months in duration (9 studies). Interventions lasting 4 to 8 months resulted in less bone loss in the exercise group than in the control group (4 studies). There was an increase in lumbar BMD for a weighted exercise programme lasting 9 months (1 study).
In studies with positive results (11 studies), training intensity was 70 to 90% of 1 RM (maximal load for one repetition with good form) for two to three sets of 8 to 12 repetitions. For these studies, training sessions were performed 3 to 5 times a week and lasted from 45 to 70 minutes each session (8 studies). There was an increase in BMD when weights equalling 80% of maximal back extensor strength were used (1 study).
A site-specific positive effect of exercise on BMD was found in the femoral trochanter (6 studies), and an increase or maintenance in BMD reported at the femoral neck (5 studies). A positive exercise effect was reported at Ward’s triangle (3 studies) and on BMD in the lumbar spine (4 studies). A positive exercise effect on the wrist (ultradistal radial site) was reported in only 1 study.