Osteoporosis And Exercise
What is Osteoporosis?
Osteoporosis, also known as porous bones or fragile bone disease, is a disease of the bones in which there is an accelerated bone loss which results in a reduction in bone mineral density, overall quantity and quality of bone tissue and an increased risk of fractures. The fractures caused by osteoporosis are most common in the hips, spine, ribs and wrists but fractures related to osteoporosis can occur in most skeletal bones.
How osteoporosis occurs
Bones consist of bone cells and the bone extracellular matrix consisting of collagen fibres and mineral deposits (calcium, magnesium, phosphates etc). Bones cells are constantly in a process of removal of old bone (resorption) and formation/synthesis of new bone – Old, worn-out bone is broken down and removed by cells called osteoclasts, whilst new bone is formed by osteoblasts. In normal bone, the rate at which new bone is formed and old bone is resorbed is closely matched. However, in osteoporosis, the rate at which bone is resorbed exceeds the rate at which new bone is formed. This results in a gradual decrease in overall bone mass. As bone mass decreases the bones become more porous (contain more holes) and become weakened. This may eventually lead to bone deformity and an increased risk of bone fractures. Research suggests that as many as 30-50% of women and 15-30% of men will suffer a fracture linked to osteoporosis during their lifetime (US Department of Health and Human Services).
The occurrence of osteoporosis is known to increase with age. In both, men and women, bone mass reaches a peak at around the ages of 25-30. After the age of 30, bone mass slowly starts to decline with age and can eventually lead to significant reductions in bone mass – some women can lose up to half of their cancellous bone density, whereas men can lose up to 25% of cancellous bone density. Although both men and women are susceptible to osteoporosis, it is 2.5 times more common in women.
Osteoporosis in women
The risk of osteoporosis in women is at its greatest following the menopause. This is due to decreased production of the female hormone oestrogen after the menopause. Oestrogen plays an important role in normal bone maintenance by having a stimulatory effect on osteoclast activity. Other causes of osteoporosis in women include: removal of ovaries before the menopause; amenorrhea (lack of menstrual cycle) caused by extreme exercise or dieting; excessive drinking or smoking.
Osteoporosis in men
In men the primary cause of osteoporosis is decreasing testosterone levels. Testosterone levels peak in the twenties and then decline gradually over a period of years (typically around 0.3% per year). However, levels don’t usually drop significantly until the age of 60, hence, the way men tend to develop osteoporosis later in life than women. One of the reasons men are less likely to suffer with osteoporosis is due to males having a denser bone mass to begin with. Because men have a denser bone mass to begin with, a small loss of bone has less of an effect.
Exercise and osteoporosis
An individual’s level of physical activity can have a major impact on bone density and hence the risk of osteoporosis. It’s known that periods of immobilization can lead to significant reductions in bone mass and that increased activity levels can help to reduce the risk of osteoporosis. In particular weight baring exercises are known to play an important role in the maintenance of bone mass.
How exercise benefits bone mass and protects against osteoporosis
Regular weight bearing exercise is believed to increase bone density, bone mass and strength through stimulating an increase in osteoblast activity levels. Researchers (Manske et al., 2009) have identified three characteristics of a weight baring exercise that determine the overall effectiveness of the exercise for improving overall bone health: 1) increased strain magnitudes (the level of force or impact), 2) increased strain rates (the rate at which the force or impact occurs), and 3) increased strain frequency (essentially the number of times the force or impact occurs in a set time).
Increasing the strain magnitude – The strain magnitude is increased when you work against additional resistance such as when weight/resistance training. The strain magnitude can be increased during aerobic exercise by using weighted vests to increase the overall strain of the exercise.
Increasing the strain rates – the strain rate is increased when a force is applied in a short time period such as when jumping, hopping or during plyometric exercise.
Increasing the strain frequency – the strain frequency is higher during exercises in which there are higher rates of force applied per time. Exercises in which there are high rates of strain frequency include jogging, running, aerobics, and circuit training.
Research on osteoporosis and exercise
A large number of research studies have found that regular physical activity can have beneficial effects on bone health including significantly reduce the risk of osteoporosis, delay the loss of bone mineral density and reduce the risk of hip fractures (Andreoli et al., 2012; Humphries et al., 2012; Shenoy et al., 2012; Winters et al., 2012; Roghani et al., 2012; Iwamoto et al., 2010; Nikander et al., 2010; Michaelsson et al., 2007; Todd and robinson, 2003; Ernst, 1998). As such exercise is now widely recommended as one of the key preventative strategies to reduce the risk of osteoporosis, falls and fractures (Nikander et al., 2010).
The best exercises for osteoporosis
As discussed above there are a number of different exercise strategies that have been found to be beneficial in the management of osteoporosis including: 1) aerobic exercise (walking, running etc); 2) weight baring impact exercise (skipping, stepping, hopping, jumping, dancing, etc); 3) Resistance exercises (e.g. free-weight exercises); 4) Whole body vibration exercises (vibration plate machines)
1) Aerobic exercise for osteoporosis - Research is clear that aerobic exercise is of benefit for improving bone health and osteoporosis risk (Roghani et al., 2012; Liu et al., 2011; Iwamoto et al., 2010; Michaelsson et al., 2007). Researchers have shown that treadmill walking for just 30 minutes (3 x weekly) was enough to stimulate bone synthesis whilst decreasing bone resorption in postmenopausal women (Roghani et al., 2012). Research looking at the effects of aerobic exercise quantity on the risk of hip fractures in men found that men took part in regular sports activities (minimum of 3hrs/wk) had a decreased risk of hip fracture compared with men leading a sedentary lifestyle or only walking or cycling for pleasure (Michaelsson et al., 2007). It appears that aerobic exercise may be particularly effective for improving the bone health in the spine and walking also improves bone health in the hips (Iwamoto et al., 2010).
2) High impact exercise for osteoporosis - High impact exercise appears to be an effective way to increasing bone mineral density (Winters et al., 2012; Shenoy et al., 2012; Martyn-St James and Carroll 2010; Todd and robinson, 2003), particularly in the hip region (Winters et al., 2012; Martyn-St James and Carroll 2010). Recently researchers have found that high impact exercise (wall push-ups, and jumping exercises performed 5 days/wk) was more effective than calcium supplements for increasing bone mass in young women with low bone mass (Shenoy et al., 2012).
3) Resistance exercise for osteoporosis - Resistance exercise appears to be particularly effective way to increase bone mineral density (Winters et al., 2012; Iwamoto et al., 2010; Nikander et al., 2010; Kukuljan et al., 2009; Todd and Robinson, 2003; Swezey, 1996;), and may be greater than weight baring exercises for improvements in bone health (Swezey, 1996). In one study researchers found that a 12 month progressive resistance training programme significantly increased bone mineral density and was more effective than consuming 400ml milk/day in a group of older men (50-79 years) (Kukuljan et al., 2009;).
4) Whole body vibration exercise for osteoporosis - Whole body vibration therapy has gained increasing popularity as a treatment for osteoporosis in recent years. However, although research suggests that it shows potential as a treatment (Humphries et al., 2012; Liu et al., 2011), the picture is not completely clear, with some studies demonstrating positive effects on bone health (Zha et al., 2012; Verschueren et al., 2011; Beck and Norling, 2010; Verschueren et al., 2004), whereas some studies have failed to find increased bone mineral density following whole body vibration treatment (van der Jagt et al., 2012; Lau et al., 2011; Slatkovska et al., 2011, von Stengel et al., 2009;).
The current research suggests that aerobic, high impact and resistance training appear to all be effective for increasing bone mineral density and bone health. However, it is not yet clear whether vibration training is of particular benefit for the treatment of osteoporosis. It appears likely that the best approach is to incorporate a range of these strategies into any exercise based training strategy.
Osteoporosis and exercise frequency
Most research has generally used three or more weekly training sessions and it appears that multiple weekly sessions are the best approach for improving bone health (Winters et al., 2012 – 3x weekly; Roghani et al., 2012 3x weekly; Shenoy et al., 2012 5x weekly;). Recent research comparing the effects of training frequency on bone mineral density (training 2 or more x weekly vs. <2 weekly training sessions) found that training frequency can significantly impact bone mineral density, with significantly greater bone mineral density occurring when participants completed 2 or more sessions a week (Kemmler and von Stengel, 2012). When researchers looked at the effects of increasing training frequency (0, 2, 4 or 7x weekly) on bone mineral density they observed that bone mineral density improved in a dose dependent manner (Bailey and Brooke-Wavell, 2010). Interestingly the rate of improvement appeared to increase in a fairly linear fashion – after 4 and 7 weekly sessions there was close to a 1% and 2% improvement in bone mineral density respectively. Therefore, although the minimum training frequency for improved bone mineral density is around 2-3/weekly sessions, it appears that greater training frequencies result in further benefits in a dose dependent manner, with increasing frequency resulting in increasing benefit.
Osteoporosis and exercise duration
Significant benefits in bone health appear to occur with modest duration sessions. Research has generally observed positive results with session durations of just 10-45minutes (Roghani et al., 2012; Nikander et al., 2010; Bailey and Brooke-Wavell, 2010; Vainionpaa et al., 2010; Macdonald et al., 2007;).
Based on current research it appears that the best approach to reduce the risk of/mange osteoporosis is to complete 3, or more, weekly sessions of 20-40 minutes duration. The best types of exercise appear to be aerobic weight baring exercises, resistance exercises and high impact exercises.
Osteoporosis and lifestyle factors
In addition to regular exercise there are a number of life style changes that may be of benefit to reduce the loss of bone mineral density:
Dietary factors – An adequate intake of calcium, Vitamin C, Vitamin D and Magnesium may be beneficial in the management of osteoporosis. Adults should consume 800-1000mg of calcium, 400mg of magnesium, 400IU of Vitamin D, and 60mg of vitamin C per day. Of these vitamins and minerals, calcium is the most important. Adults who are at risk of osteoporosis can increase their intake of calcium to 1000-1500mg per day. Calcium rich foods include: dairy products (particularly milk), leafy vegetables (brocholli, kale, cabbage etc.), and many fish (tuna, salmon, sardines and haddock)
Bodyweight – Maintaining an adequate bodyweight is an important factor for bone health. Obviously diet is a key factor for maintaining bodyweight and as such excessive dieting can lead to significantly reductions in bodyweight and negatively impact bone health - particularly when body mass index (BMI) drops below the healthy range (e.g. 19 or less). For those who naturally have a low BMI resistance training can be particularly effective in protecting against the negative effects of low BMI on bone health.
Smoking – smoking can affect bone health by damaging bones and the bone forming osteoblast cells. It causes this damage on a number of levels including: 1) damage to bones and bone forming cells by nicotine and the free-radical toxins released through cigarette smoke; 2) reducing estrogen levels – a key hormone for bone health; and 3) increasing levels of cortisol which can increase the breakdown of bone.
Excessive alcohol consumption – like smoking, excessive alcohol consumption can affect bone health on multiple levels: 1) Excessive alcohol consumption interferes with calcium and vitamin d absorption – 2 key nutrients for bone health; 2) it can interfere with oestrogen levels; 3) Increased cortisol levels; 4) may reduce the activity of osteoblasts (bone forming cells).
Excessive consumption of fizzy/carbonated drinks – Intake of Fizzy (carbonated) drinks should be minimized as this may have negative effects on calcium levels in the body. The carbon dioxide in the fizzy drinks is acidic. The body tries to neutralize this with calcium, thereby wasting valuable calcium.
Excessive caffeine intake – there is some evidence that excessive caffeine intake is a risk factor for elderly women with low calcium intake.
Osteoporosis and exercise summary:
- Osteoporosis is a disease of the bones characterized by increased bone loss and risk of bone fractures.
- It occurs when there are increased rates of bone resorption than bone formation.
- The incidence of osteoporosis is greater in women, particularly after the menopause.
- Osteoporosis also occurs in men where low testosterone levels are a key factor.
- Regular weight baring exercise can help to maintain bone health and reduce the risk of osteoporosis.
- The best exercises for osteoporosis appears to be aerobic weight baring exercise (walking, jogging, running, aerobics etc), high impact exercise (skipping, stepping, hopping, jumping, dancing, etc), and resistance exercise (free weight exercises).
- There is some evidence that whole body vibration exercise may be beneficial for osteoporosis, although results have been mixed.
- The optimum frequency and duration of exercise for osteoporosis appears to 3 or more weekly sessions of 20-40 minutes duration.
- A number of lifestyle factors may influence the osteoporosis risk including poor diet, smoking, excessive alcohol, caffeine, and carbonated drink consumption along with having a low bodyweight (a BMI of 19 or less).
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