EXERCISE AND OSTEOPOROSIS

activity are minimal, provided a sensible approach is followed. As with any exercise prescription it is essential to adhere to all the usual rules of safe exercise.

It is possible to exercise too much In this case more exercise than necessary is not better, too much exercise can be harmful if taken to extremes. Young female endurance athletes, who train by running many miles per week, and who also diet to reduce their body fat stores to very low levels, run the risk of becoming amennorheic. If this happens they may lose substantial amounts of bone mineral just as an older woman going through the menopause does. This particularly affects spinal BMD and may not be fully reversible even after menses return.

Osteoarthritis sufferers Those with symptoms of osteoarthritis should not do high impact exercise. Fortunately it is rare for both diseases to occur together so those at risk of osteo- porosis are unlikely to be vulnerable to osteoarthritis unless they have been treated with oral steroids.

Hazards of inactivity Immobility, bedrest or space flight are all associated with massive loss of bone min- eral and serve as extreme examples of the devastating effects of lack of activity and gravitational loading on the skeleton.

Medication and exercise The effect of an active lifestyle on both improvements in BMD and reduction of fracture risk appears to be independent of drug therapy, so exercise provides addi- tional benefit. Therefore women who are treated with HRT for low BMD should not assume that there is no need to exercise. There is also no reason why individuals on other drug therapies such as bisphospho- nates should not take exercise as well. Indeed as the drug improves their BMD it should become safer for them to be more physically adventurous.

Monitoring the disease Frequent monitoring is pointless because bone changes slowly, an assessment every few years is therefore usually adequate. After starting drug therapy bone turnover changes and there is a phase of at least six months during which the bone gradu- ally comes into a new equilibrium, so the true effects of treatment cannot be

20 SportEX

assessed until this phase is over. Assessment should be made using DEXA because normal values are available and diagnostic levels established. The assess- ment is quick and convenient, with a low radiation dose (less than one fiftieth of a chest x-ray). Ultrasound scans of the heel bone are becoming available in the mar- ket place but are not recommended. They do not yet provide a secure diagnosis and can raise the alarm unnecessarily or pro- vide false re-assurances. Moreover they cannot assess the bone sites of most con- cern, namely, the hip and spine.

Contacts/Resources The National Osteoporosis Society The NOS produce a number of publi- cations for both the public and the medical profession. Recent publica- tions include guidelines for medical professionals on clinical decision making and best practise for patients at risk. There is also a new booklet for the public giving advice on exercise (£3). Tel. 01761 471771

References 1. Frost H. Suggested fundamental concepts in skeletal physiology. Calcified Tissue International 1993;52:1-4 2. Jaglal SB, Kreiger N, Darlington G. Past and recent physical activity and risk of hip fracture. Am J Epid 1993;138:107-118 3. Menkes A, Mazel S, Redmond RA et al., Strength training increases regional bone min- eral density and bone remodeling in middle- aged and older men. J Appl Physiol 1993;74:2478-2484

4. Bassey E, Rothwell M, Littlewood J, Pye D. Pre- and postmenopausal women have different bone mineral density responses to the same high-impact exercise. J Bone & Miner Res 1998;13:1805-1813 5. Snow-harter C, Bouxsein ML, Lewis BT, Carter DR, Marcus R. Effects of resistance and endurance exercise on bone mineral status of

young women: a randomized exercise interven- tion trial. J Bone Miner Res 1992;7:761- 769 6. Welsh L, Rutherford OM. Hip bone mineral density is improved by high-impact aerobic exercise in postmenopausal women and men over 50 years. Eur J Appl Physiol 1996;74:511-7 7. Kohrt W, Snead D, Slatopolsky E, Birge SJ. Additive effects of weight-bearing exercise and estrogen on bone mineral density in older women. J Bone & Miner Res 1995;10:1303- 1311 8. Kerr D, Morton A, Dick I, Prince R. Exercise effects on bone mass are site-specific and load dependent. J Bone & Miner Res 1996;11:218- 225

9. Sinaki M, Mikkelsen BA. Postmenopausal spinal osteoporosis: flexion versus extension exercises.

Arch Phys Med Rehabil 1984;65:593-596