Site specificity of regular health club exercise on muscle strength, fitness, and bone density in women aged 29 to 45 years

The effect of exercise intensity on bone in postmenopausal women (part 2): A meta-analysis

BACKGROUND

Previous reviews have concluded that exercise has only modest effects on bone mineral density (BMD) in postmenopausal women. Despite the well-recognized strong positive relationship between load magnitude and bone response observed from animal research, the majority of human trials have examined the effects of only low to moderate intensity exercise on bone. We speculated that meta-analysing according to intensity may reveal a more potent exercise effect at higher intensity.

OBJECTIVES

To determine the effects of low, moderate and high intensity exercise on BMD at the spine and hip in postmenopausal women.

METHODS

Electronic databases and reference lists were searched for RCTs that examined the effect of exercise compared to control on DXA-derived lumbar spine, femoral neck or total hip BMD in healthy postmenopausal women. Interventions were classified as low, moderate or high intensity and pooled based on classification. Mean differences (MD) were calculated using random effects models and a risk of bias analysis was undertaken. To determine the effect of different exercise types (resistance and impact training) on BMD outcomes, subgroup analyses for all intensity categories and outcomes were conducted. Separate meta-analyses were undertaken to examine the influence of adding exercise to a bone medication intervention and to examine exercise effects on fracture risk.

RESULTS

Fifty-three trials, testing 63 interventions (19 low, 40 moderate, 4 high intensity) were included. At the lumbar spine, high intensity exercise yielded greater BMD effects (MD = 0.031 g/cm² 95% CI [0.012, 0.049], p = 0.002) than moderate (MD = 0.012 g/cm² 95% CI [0.008, 0.017], p < 0.001) and low intensity (MD = 0.010 g/cm² 95% CI [0.005, 0.015], p < 0.001). Low and moderate intensity exercise was equally effective at the femoral neck (low: 0.011 g/cm² 95% CI [0.006, 0.016], p < 0.001; moderate: 0.011 g/cm² 95% CI [0.007, 0.015], p < 0.001), but no effect of high-intensity exercise was observed. Moderate intensity exercise increased total hip BMD (0.008 g/cm² 95% CI [0.004, 0.012], p < 0.001), but low intensity did not. There were insufficient data to meta-analyse the effect of high intensity exercise at the total hip. Resistance training, potentially in combination with impact training, appears to be the most effective osteogenic stimulus at the spine and hip. Findings from meta-regression analyses were not informative and no influence of exercise on medication efficacy was observed. Risk of bias was mainly low or unclear due to insufficient information reported.

CONCLUSION

High intensity exercise is a more effective stimulus for lumbar spine BMD than low or moderate intensity, but not femoral neck BMD, however, the latter finding may be due to lack of power. While data from high-intensity exercise interventions are limited, the current comprehensive meta-analysis demonstrates the same positive relationship between load magnitude and bone response in humans that is observed in animal research. Findings have implications for optimal exercise prescription for osteoporosis in postmenopausal women.

STUDY REGISTRATION

Registered on PROSPERO (CRD42018117254).

The effect of exercise intensity on bone in postmenopausal women (part 1): A systematic review

BACKGROUND

Previous systematic reviews and meta-analyses of exercise effects on bone have reported null or modest effect sizes. While animal research has determined that a strong positive relationship exists between load magnitude/intensity and bone adaptation, nevertheless many human exercise interventions have been applied at low intensity. Meta-analytic pooling of exercise interventions irrespective of intensity dilutes the ability to detect efficacy of any one training regimen. Parsing out efficacy of low, moderate and high intensity exercise interventions will assist the determination of optimal exercise prescription for bone.

OBJECTIVES

First, to summarise and critically evaluate existing evidence of exercise effect on bone mass, bone structure and bone turnover markers (BTMs) in healthy postmenopausal women. Second, to examine the influence of intensity on bone response to exercise.

METHODS

Electronic databases (Embase, Scopus, CINAHL Plus, SPORTDiscus), database platforms (PubMed, Cochrane CENTRAL, ProQuest Central, Web of Science) and reference lists of included studies were searched for controlled trials and randomised controlled trials that described the effect of any exercise intervention compared to control on bone mass, bone structure or BTMs in healthy postmenopausal women. Fracture incidence was included as an exploratory endpoint. Data was extracted and weighed against the results of a comprehensive risk of bias analysis.

RESULTS

One hundred trials were included, investigating a total of 120 exercise interventions. Of those, 57 interventions were low intensity, 57 were moderate, and six were high intensity. On balance, low intensity exercise was not an effective stimulus to increase bone mass. Higher quality evidence suggests moderate to high intensity interventions, particularly those that combined high intensity resistance and impact training, were most beneficial for bone mass. Only high intensity exercise appears to improve structural parameters of bone strength, however, data are limited. Only low and moderate intensity interventions have measured BTMs and no notable benefits have been observed. The quality of trials varied greatly, and risk of bias determinations were frequently limited by insufficiently reported detail.

CONCLUSION

Heterogeneity in both study quality and outcomes limits the ability to draw strong conclusions from this comprehensive systematic review of RCT and CT reports. Nevertheless, there is a tendency in the higher quality data to indicate exercise intensity is positively related to the adaptive bone response. Part 2 of this review series reports a meta-analysis of the RCT data in order to draw quantitative conclusions from the higher quality trials.

STUDY REGISTRATION

Registered on PROSPERO (CRD42018117254).

Association of Modifiable Risk Factors with Bone Mineral Density among People with Distal Radius Fracture: A Cross-Sectional Study

Purpose: This study determined the extent to which modifiable risk factors (balance, muscle strength, and physical activity [PA]) explained variability in bone mineral density (BMD) among people with a recent distal radius fracture (DRF). Method: This cross-sectional study included 190 patients, aged 50-80 years, with a DRF. Participants were assessed for balance, muscle strength, PA, fracture-specific pain, and disability. Areal BMD at the femoral neck (BMD-FN) and total hip (BMD-TH) was assessed. Correlation and multiple linear regression was used to determine the contribution of modifiable risk factors to BMD. Results: Balance, handgrip strength, knee extension strength, and plantar-flexion strength had significant bivariate associations with BMD-FN. There was a weak to moderate correlation (r = 0.25-0.40; p < 0.05) of balance and grip strength with BMD. Grip strength independently (p < 0.05) explained 17% and 12% of the variability in BMD-FN (n = 81) and BMD-TH (n = 82), respectively. Stratified by age, balance (R ² = 0.10; p = 0.04) and grip strength (R ² = 0.32; p = 0.003) were independent significant predictors of BMD-FN among women aged 50-64 years and 65-80 years, respectively. Conclusions: Grip strength of the unaffected hand is independently associated with BMD-FN and BMD-TH in people with recent DRF. It may act as a surrogate for general bone health, frailty, or overall muscle strength rather than as a direct target for intervention.

Beneficial effects of conjugated linoleic acid and exercise on bone of middle-aged female mice

Conjugated linoleic acids (CLA) are a group of polyunsaturated fatty acids that has recently been shown to have several beneficial effects on different diseases, including prevention of bone loss. The important feature of CLA is to reduce fat mass, thereby reducing body weight significantly. Although loss of body weight is known to increase bone loss, there is increasing evidence that CLA maybe beneficial to bone. Another factor that can reduce body weight is exercise (EX). It is well established that moderate EX stimulates bone formation. In this study, we analyzed the changes in bone using pQCT densitometry in middle-aged C57Bl/6 mice fed CLA (0.5%) and/or exercised. Twelve-month-old mice were divided into the following groups: group 1, corn oil, sedentary (CO SED); group 2, corn oil, exercise (CO EX); group 3, CLA, sedentary (CLA SED); and group 4, CLA, exercise (CLA EX). Mice were maintained in the respective experimental regimens for 10 weeks, after which mice were scanned using DEXA and killed. The lumbar vertebrae, femur, and tibia were analyzed using pQCT densitometry. CLA, when given alone or in combination with EX, significantly reduced body weight and increased lean mass. CLA treatment also significantly increased bone mass. Further, additional increase in bone mass was observed in mice treated with a combination of CLA and EX in almost all the bone sites analyzed. We conclude that CLA, when consumed as a dietary supplement along with moderate treadmill EX, significantly increases bone mass in middle-aged female mice.

The role of physical activity in bone health: a new hypothesis to reduce risk of vertebral fracture

Locomotion has always been a major criterion for human survival. Thus, it is no surprise that science supports the dependence of bone health on weight-bearing physical activities. The effect of physical activity on bone is site-specific. Determining how to perform osteogenic exercises, especially in individuals who have osteopenia or osteoporosis, without exceeding the biomechanical competence of bone always poses a dilemma and must occur under medical advice. This article presents the hypothesis that back exercises performed in a prone position, rather than a vertical position, may have a greater effect on decreasing the risk for vertebral fractures without resulting in compression fracture. The risk for vertebral fractures can be reduced through improvement in the horizontal trabecular connection of vertebral bodies.

Predictive value of grip strength for bone mineral density in males: site specific or systemic?

This study aimed to investigate the predictive role of grip strength on bone mineral density (BMD) of different sites in males. Two hundred thirty-four male patients were included in the study. BMD of lumbar spine, femoral neck, proximal radius-ulna (PRU) and distal radius-ulna (DRU) sites were measured by dual-energy X-ray absorptiometry and grip strength by using a hand dynamometer. Grip strength and BMD values of PRU and DRU at forearms were significantly higher on the dominant sides (P = 0.001, P = 0.001, P = 0.001, respectively). Stepwise linear regression analysis revealed that only the grip strength of the same side was the best predictor of the BMD of the dominant and non-dominant PRU with a ratio of 8.5 and 10.2%, respectively, whereas grip strength of the same side, age and weight were the best predictors of the BMD of the dominant and non-dominant DRU with a ratio of 25 and 24.6%, respectively. There was no predictive value of grip strength for BMD of lumbar spine and femoral neck. In conclusion, grip strength appears to be predictive of site specific rather than systemic BMD.

Falls, fractures, and hip pads

Improvement of balance along with bone-enhancing pharmacotherapy can improve the level of an individual's physical activity and mobility. Balance can be improved with enhancement of postural proprioception and muscular strength. Postural deformities have been shown to impair quality of life of osteoporotic individuals. Kyphotic posture has been demonstrated to contribute to propensity to fall in osteoporotic individuals. Kyphotic posturing and gait disorders can be managed through proprioceptive training, use of a weighted kypho-orthosis, muscle re-education, and safe resistance exercises. Proprioceptive balance training can reduce falls and fracture. Sarcopenia and osteoporotic fractures create musculoskeletal challenges that cannot be met with pharmacotherapy alone. Bone loss, imbalance, and gait disorder along with cognitive concerns can increase with aging. Even in healthy persons, predisposition to falls increases with age-related neuromuscular changes. Muscle strength decreases approximately 50% from age 30 to 80. Furthermore, the amount of body sway increases with reduction of proprioception. Therefore, measures that can decrease imbalance can reduce the risk for falls and fracture. In normal balance, ankle strategies are recruited rather than hip strategies. Strengthening of the lower extremity muscles reduces the risk for falls. Gait aids can also decrease the risk for falls. During a fall, the risk for hip fracture increases 30-fold if there is direct impact to the hip. The use of hip protectors can decrease the risk for hip fracture during a sideways fall. Training in effective safe-landing strategies should be included in fall prevention programs.