Strong back muscles can lower future fracture risk

Exercise builds muscle and bone, but the benefits are held to disappear upon exercise cessation — or so it appeared, anyway. A recent exercise study from the Mayo Clinic, however, documented powerful spinal fracture reduction eight years after cessation of a back strengthening program. Eight years after stopping this two-year exercise program, past exercisers had significantly greater bone density, and nearly a 2.7 times lower vertebral compression fracture incidence, than non-exercising controls.

This study found that healthy postmenopausal women can reduce their 10-year risk of vertebral fracture by nearly 300% with one simple back exercise performed 5 days a week. As suggested by this study, back-strengthening exercise is far more effective at reducing spinal fracture than any drug therapy and is totally safe — a true Better Bones, Better Body® Approach. Let’s look at the study in detail.

This Mayo Clinic study involved 50 healthy Caucasian postmenopausal women ages 58–75, with no back pain or injury. The women were divided into 2 groups for a 2-year randomized controlled exercise trial. Twenty-seven women performed progressive, resistive back-strengthening exercises, and twenty-three served as non-exercising controls. Measurements were made of back extensor muscle strength, bone mineral density, and spinal deformity.

At baseline, back extensor muscle strength was similar in both groups (exercisers at 39.4 kg and controls at 36.9 kg) and there was no significant difference in bone mineral density. By the end of the 2-year study period, exercisers had increased back extensor strength by some 70% while controls gained 32% in strength and there was no significant difference in bone mineral density between the two groups. At 10 years, the exercising group had lost 16.5% of their baseline back strength (down to 32.9 kg from 39.4) and the control had lost 27.1% of their baseline strength (down to 26.9 from 36.6 kg). The difference in back strength was still significant at 10 years. Overall, exercisers lost 1.65% back muscle strength per year while controls lost 2.7% a year. Bone density declined in both groups, but at 10 years, exercisers had significantly greater bone density than controls. Most importantly, among past exercisers, spinal compression fractures rates were 2.7 lower even 8 years after cessation of the back-strengthening exercise program.

And what was this effective exercise program? Women were instructed in progressive, resistive weight-lifting exercise for the back extensor muscles. They used a backpack that contained weights equivalent to 30% of the maximal isometric back extensor strength. Lying in a prone position (on their stomachs) they lifted the backpack ten times (see illustration). As their back strength increased, the amount of weight lifted was increased. The maximum weight of the backpack was 50 lbs. Women did the 10 repetitions of this back weight-lifting exercise 5 days a week for 2 years.

 

Reference:

Sinaki, M, et al. 2002. Stronger back muscles reduce the incidence of vertebral fractures: A prospective 10-year follow-up of postmenopausal women. Bone, 30(6):836-841.

 


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