Bone density and physical activity

Abstract

Osteoporosis is currently the major cause of fracture in older people. The most common fractures in the UK are hip fractures (60000 per year), closely followed by wrist (or Colle's) fractures (50000 per year) and vertebral fractures (40000 per year). Many osteoporotic fractures are associated with significant morbidity and mortality, with hip fractures being the most severe consequence. Of hip-fracture victims, 5-20 % will die within 1 year of the fracture and many more experience long-term disability which seriously reduces the quality of life. In 1994 the cost to the National Health Service was approximately 5750 million, and with the growing elderly population this figure is set to rise.The maximal load a bone can withstand without fracture is positively related to its bone mineral density (BMD). Bone mass peaks between the ages of 20 and 40 years, with men achieving a greater peak bone mass. After the age of 40 years, bone mass declines at a rate of 0.5-1 .O % per year, with an accelerated period of loss in women for 5-10 years after the menopause. In total, women lose about 25-30 % of the cortical bone and 35-50 % of the trabecular bone over a lifetime; men lose at about two-thirds this rate (Riggs et al. 1981). This leaves thin cortical bone and thin or interrupted trabecular plates. Once bone mass has declined to a critical threshold, fractures are likely to occur. Physical activity is one of the factors which can influence the attainment of peak bone mass and reduce the age-related loss. For this reason, there is considerable interest in identifying the most effective forms of exercise for increasing BMD with the assumption that, in the longer term, this will reduce fracture incidence. A large number of intervention and crosssectional studies have been conducted to try and identify the optimal form of activity for improving bone density. The present review aims to highlight those studies which have provided evidence that activity is good for bone and point to those forms of exercise which have been shown to improve BMD at the key fracture sites. In addition, attention will be drawn to possible detrimental effects of exercise on BMD and fracture incidence. FALLS AND FRACTURESThe majority of osteoporotic fractures, particularly those of the hip, occur as a result of a fall. It is important, therefore, to consider the factors which predispose the person to fall. These risk factors include: psychoactive drugs and other medications; dementia, depression and cognitive function; poor proprioception; poor gait and muscle strength; poor postural stability; dizziness and vestibular problems; poor functional ability; poor eyesight. Of these, muscle strength, postural stability and functional ability may be improved by the appropriate exercise. In the older person, therefore, exercise regimens should be designed to target these risk factors in addition to improving BMD.

Relationship of skeletal muscle mass, muscle strength and bone mineral density in adults with cystic fibrosis

“…There is increasing recognition that muscle mass and strength are important for bone health, and that increasing muscle strength through an increase in muscle mass may have positive effects on BMD. Weight-bearing activity is important for bone acquisition in children and adolescents, and has also been shown to slow down bone loss in postmenopausal women [17]. The CF population tends to do less physical activity due to decreased aerobic capability.…”

Physical activity, diet and skeletal health

“…Additionally, up to 50% of patients will be disabled, half of them requiring long term nursing home care, while only one third fully recover from hip fracture. This entails a great burden on the health service, that in the UK was estimated to 750 million pound in 1994 3 . The risk of an osteoporotic fracture in the elderly is compounded by the risk of fall and by the risk of fracture as a consequence of the fall.…”

The Effects of a Uniformly Weighted Exercise Suit on Biomarkers of Bone Turnover in Response to Aerobic Exercise in Postmenopausal Women With Low Bone Density

“…There is a large body of research investigating the difference between bone density measures of various athletic groups and matched sedentary controls. In general, results show difference (6-20%) in BMD and BMC between exercisers and controls at different anatomical sites, over a wide range of physical activities (Rutherford, 1997). The type of activity can affect the degree of increase in BMD.…”

“…Although effective, this type of training is associated with increased risk of fracture and decreased quality of life due to injury (Martyn-St James & Carroll, 2006). Recently, aerobic exercise has been indicated as a lower risk alternative method of loading the skeleton when compared with high intensity impact training (Alghadir, Aly, & Gabr, 2014;Block, Genant, & Black, 1986; N. E. Lane et al, 1986;Nilsson, Andersson, Havdrup, & Westlin, 1978;Rutherford, 1997;Talmage, Stinnett, Landwehr, Vincent, & McCartney, 1986), but is not as effective. However, weighted aerobic exercise, utilizing load carriage systems (LCS), increases the gravitational forces impacting the bone creating a higher osteogenic stimulus than standard aerobic exercise.…”

“…Despite our mechanistic understanding of the influence of exercise on BMD, findings have been conflicting regarding the impact of exercise interventions on BMD. Inconsistencies may be attributed to variations in the type, duration, frequency, and intensity of the exercise interventions tested (Gutin & Kasper, 1992;Rutherford, 1997;Stewart et al, 2005).…”