Greater Trunk Muscle Torque Reduces Postmenopausal Bone Loss at the Spine Independently of Age, Body Size, and Vitamin D Receptor Genotype in Japanese Women

Abstract

Bone mineral density (BMD) is affected by muscle strength. Recently, vitamin D receptor (VDR) genotype was reported to affect muscle strength as well as BMD in Caucasian women. The aim of this study was to evaluate independent effects of muscle strength of the trunk on BMD at the spine and its change over time in Japanese women. We followed 119 healthy postmenopausal women for 4 years and determined the change in BMD at the spine by dual energy X-ray absorptiometry. Isometric peak torque and isokinetic concentric and eccentric peak torque of the trunk flexors and extensors were measured. The VDR genotype was determined by the PCR-RFLP method based on Apa I and Taq I endonuclease digestions defining the absence/existence of the restriction sites as A/a and T/t, respectively. The subjects were 60.1 +/- 6.6 years old, had 0.808 +/- 0.159 g/cm2 of BMD at baseline. The mean annual change in BMD (delta BMD) was -5.6 +/- 10.4 mg/cm2 during the follow-up period. The VDR genotype, defined by Taq I enzyme, significantly related to BMD at baseline and delta BMD showing that the subjects with genotype TT had the lowest BMD at baseline and lost bone most rapidly. However, its effect on muscle strength was not significant. All the trunk muscle strength indices showed significant positive effects on delta BMD, that is, the effects in increasing the gain and reducing the loss of BMD, after controlling for the effects of age, body size and the VDR genotype. The eccentric trunk extensor torque had a significant positive effect on delta BMD in a dose-dependent manner. The effect of this torque was the greatest among all the muscle indices. The net effect of the trunk extensor torque on delta BMD was greater than that of the VDR genotype. The trunk muscle strength was suggested to affect BMD change independently of age, body size, and the VDR genotype. Exercise programs to increase the strength of the trunk muscles would be beneficial for the prevention of osteoporosis regardless of the VDR genotypes.

Trunk muscle strength, but not trunk rigidity, is independently associated with bone mineral density of the lumbar spine in patients with Parkinson's disease

“…[37][38][39] Now, for the first time, we show that trunk muscle strength is independently associated with lumbar spine BMD in PD patients. The positive association between trunk muscle strength and lumbar spine BMD could be explained by the local biomechanical effects exerted by the muscles on bone tissue.…”

Muscle Mass Is More Strongly Related to Hip Bone Mineral Density Than Is Quadriceps Strength or Lower Activity Level in Adults Over Age 50Year

“…Studies have demonstrated that spine extensor muscle weakness is associated with low spine bone mineral density (BMD), (1,2) and spine deformity. (3) However, there are differing results regarding whether knee extensor strength is an independent predictor of BMD.…”

Effects of exercise therapy on bone mineral density in early postmenopausal women: a controlled trial

“…Most experts agree that there are two types of exercises that provide the most bone benefits: weightbearing exercises and strength-training (or resistance) exercises. Iki found a relationship between the trunk muscle strength and BMD exists independent of age, body size, dietary calcium intake, and the vitamin D receptor (VDR) genotype in postmenopausal Japanese women [30]. Also, Dixon found that in elderly women low grip strength was a marker of low BMD at both the spine and hip; low grip strength in women was associated with an increased risk of incident vertebral fracture [31].…”