Less frequent lifting won for postmenopausal bone density

After menopause, falling oestrogen accelerates bone loss, raising the long-term risk of osteoporosis and fracture. Resistance training is often recommended to protect bone, because loading the skeleton is thought to stimulate it to adapt, but the trials testing this idea have used wildly different programmes. This review set out to do two things: establish whether dynamic resistance exercise genuinely improves bone mineral density in postmenopausal women, and work out which training variables, such as frequency, intensity, volume and equipment, actually drive the effect.

The researchers systematically searched eight databases up to March 2019 for controlled trials of isolated dynamic resistance training lasting at least 6 months in postmenopausal women, with bone density measured at the lumbar spine or proximal femur. Seventeen articles qualified, contributing 20 exercise groups and 18 control groups. They pooled the standardised changes in bone density at the lumbar spine, femoral neck and total hip, then ran subgroup analyses on intervention length, type of training, weekly frequency, exercise intensity and volume.

Resistance training produced significant improvements at all three sites: the effect was moderate at the lumbar spine, small at the femoral neck and moderate at the total hip. In the subgroup analyses, training fewer than 2 sessions a week was associated with significantly greater bone density gains at the spine and total hip than 2 or more sessions, and free weight training beat machine-based training for the total hip. At the femoral neck, no training variable made a detectable difference. The authors concluded the subgroup patterns were not consistent enough to derive meaningful exercise recommendations.

The core finding confirms what earlier evidence suggested: lifting helps postmenopausal bone, though the effect is low to moderate rather than dramatic. The frequency result complicates the intuitive assumption that more training means more bone, but subgroup comparisons across different trials are a weak way to test that, since the low-frequency and high-frequency programmes also differed in other ways. The honest position, which the authors take, is that we still do not know the optimal recipe of frequency, intensity and equipment for building bone.

For postmenopausal women, this is further evidence that resistance training is associated with measurable, if modest, improvements in bone density at the sites where fractures matter most. It also suggests that a heavy weekly schedule is not obviously necessary for bone benefits, since less frequent programmes did at least as well in this dataset. That pattern is intriguing rather than settled, and the review explicitly stops short of turning it into training guidance.