This article discusses the importance of exercise for bone health.
About the Author
Dr Weeks is a Physiotherapy Lecturer in the School of Physiotherapy and Exercise Science at Griffith University (Gold Coast) and a Researcher in the Griffith Health Institute. His research focus is on the influence of physical activity on musculoskeletal health with a specific interest in bone strength and osteoporosis.
The facts on bone
When you think of bone, you might be inclined to picture the dry, inert and lifeless image of skeletal remains. Whilst this might be a common portrayal, living bone behaves quite to the contrary. Bone is actually a very dynamic and responsive tissue that is constantly adapting. Our skeleton is continually recycled via a process known as remodelling, whereby old bone is resorbed and replaced with new bone. In addition, a process called modelling makes changes to the size and shape of our bones, particularly during growth. Our skeleton serves a number of very important bodily functions including movement and support, protection of organs, production of blood cells and provides a reservoir for calcium used in many other body functions.
The amount of bone you have changes as you age (Figure 1). Bone mass rises dramatically over the first two decades of life such that by age 20 years you have accrued approximately 80% of your bone mass. Your peak bone mass is achieved around 30 years of age before an inevitable decline throughout the remainder of your years. For women, there is an accelerated period of bone loss at menopause. If bone mass drops too low you may be diagnosed with a condition called osteoporosis; a condition of poor bone strength that greatly increases your risk of suffering a broken bone. The most common sites of broken bones due to osteoporosis include the hip, spine, and forearm. You might be alarmed to hear that of people over 50 years of age, one in three women and one in five men will be affected by osteoporosis worldwide (Melton, Chrischilles et al. 1992; Melton, Atkinson et al. 1998). In 2000, 3.8 million Europeans sustained osteoporotic fractures, with one fracture occurring every 8 seconds (Johnell and Kanis 2006).
|Figure 1: Changes in bone mass across the lifespan
The importance of exercise for bone health Bone strength (i.e. resistance to breaking) is not only determined by the amount of bone you have, but the size and shape of your bones. The good news is that bone responds to mechanical loads (or impacts) to which they are routinely exposed. Just as the shaft of your golf club needs to be stiff enough and strong enough to avoid breaking, so too do the long bones in your arms and legs. But unlike your golf clubs, bones have the capacity to respond to loads and strengthen themselves by getting thicker and wider. Recent advances in bone measurement allow researchers to easily measure these important changes in bone size (Figure 2).
|Figure 2: A peripheral quantitative computed tomography unit (Stratec, Pforsheim, Germany)
Probably the easiest way to load your bones is to engage in exercise or other physical activity. Activities that are weight-bearing (i.e. involve impact with the ground) or require large muscle forces (e.g. weight lifting) have the potential to load your skeleton most effectively. Exercises that impose large weight-bearing loads on the body are particularly beneficial for building and maintaining strong bones, especially if the loads are applied very fast. Gymnastics, for example, applies loads that can be as great as 12 times your bodyweight at very high speeds (i.e. impacts occur within a fraction of a second). It is not surprising then, that gymnasts have very strong bones when compared to athletes in other sports with lighter impacts such as running and swimming (Taaffe, Snow Harter et al. 1995). Furthermore, the duration of exercise required for a bone response is very short as the skeleton tends to lose sensitivity as an activity progresses in time. The bone response is also very site-specific, meaning that only the bones that are loaded will respond. Tennis players, for example, tend to have stronger bones in their racquet arm than their non-racquet arm due to the muscle forces and impacts sustained during tennis strokes (Kannus, Haapasalo et al. 1995).
It is well known that genetic factors are the most important determinant of bone mass, however, other important factors that influence bone health include hormonal status, nutrition and other lifestyle factors (e.g. smoking and alcohol intake). Hormones, such as growth hormone and insulin-like growth factor, exert a powerful influence on bone accrual during growth. During adulthood, however, the sex steroids (i.e. estrogen and testosterone) become important for the maintenance of healthy bones. Estrogen deficiency or menopause, for example, results in an increase in activity of bone resorbing cells, which leads to rapid bone loss. Nutrition including calcium and vitamin D are equally important and deficiencies may compromise bone health. Adequate calcium intake for instance is imperative to provide the building blocks for strengthening bones in response to exercise (i.e. mechanical loading), whilst vitamin D provides for effective absorption of ingested calcium across the gut into the bloodstream.
The importance of golf for bone health! Whilst many of the health benefits of regular golf participation may be intuitive, they are yet to be reported exhaustively in the scientific literature. Most reports that can be found tend to focus on the cardiovascular benefits of the game. For instance, a Finnish study by Parkkari and colleagues (2000) found that middle-aged men who played golf 2-3 times per week for 5 months gained several physiological benefits including reduced body mass index and waist circumference, improved cardiorespiratory fitness, and improved cholesterol levels. High quality research is even more scant for the influence of golf on bone health. As the impact loads in golf are relatively modest, it is unlikely to be an optimal bone-building activity. However, it may have advantages to bone over other very common activities such as walking, swimming, and stretching. For instance, the rotational nature of the golf swing itself demands strong contraction of muscles that attach around the spine. Muscle contractions such as these are potentially beneficial for applying loads to the underlying bones. In fact, one recent study showed that regular golf improved the bone mass and size of lumbar (the low back) vertebrae in a large group of post-menopausal women (Eser, Cook et al. 2008). This effect, however, was only found in those women who were also on hormone replacement therapy. As the golf swing demands powerful contraction of upper limb muscles, its effect on forearm bone strength is worthy of future investigation. Furthermore, the distance and intensity of walking undertaken during a round of golf may in itself be an important consideration when evaluating the skeletal benefits of the sport. For instance, a year-long Japanese study of female caddies found that the distance walked over the golf course terrain was sufficient to produce small bone mass gains at the hip and spine, however when compared to control subjects the effect was not strong enough to reach statistical significance (Goto, Ishima et al. 2001). In conclusion, coaches and players might consider the intensity of their training and perhaps incorporate cross-training as a means to include more potent ‘bone-friendly’ exercise. Whilst there may be numerous physiological benefits of golf participation for healthy individuals, caution should be taken by those who have been diagnosed with bone disease such as osteoporosis, as vertebral fractures sustained during the golf swing have been reported (Ekin and Sinaki 1993). More research is needed, however, to fully establish the effects of golf participation on the skeleton and the risk of osteoporosis.
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