Physiology, Health & Exercise

Lesson 17 Osteoporosis- cause & effectsPrevention & role of exercise

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Osteoporosis

Includes: Osteoporosis & bone growth Effects of exercise on bone density

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What is osteoporosis?

Long term condition. Bones become progressively more porous

& brittle Literally means “porous bones” Increased risk of fractures Sometimes called the “silent thief”

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What is osteoporosis?

Even minor falls e.g. stepping off a kerb, can cause fractures

Most common sites of fractures: Wrist Spine Hip

Bones tend to break into fragments (rather than a clean break)

Impossible to reassemble, so can require surgical treatment

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What is osteoporosis?

Other effects Loss of height Curvature of the spine Chronic back pain

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Bone density

Bones is living Constantly renewed throughout life Bones grow in size during adolescence &

childhood Can completely renew skeleton in 2 years

at this stage (takes 7-10 years for adults) From late adolescence bones stop

growing in length & instead become stronger- more dense

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Bone density

if adequate calcium intake in diet & are physically active then:

Peak bone density- in late 20s to early 30s At age 35 balance between bone

breakdown & new formation stable bone density

After 35 bone loss increases part of natural aging process

Rate of approx 1% per year for females After menopause rate loss 2-3% a year

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Who gets osteoporosis?

Men Women Children Most common in menopausal women 20-50% of women over 50 are affected 75% of women over 90 are affected 1 in 12 men in UK affected Men at lower risk because tend to have

larger and stronger bones

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Risk factors for osteoporosis

Women Lack of oestrogen caused by

Early menopause (before age of 45) Missing periods for > 6 months (excluding

pregnancy) as a result of over exercising or over-dieting

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Risk factors for osteoporosis

Men Low levels of testosterone

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Risk factors for osteoporosis

Both men & women Diet lacking calcium & Vitamin D Vitamin D required for absorption of

calcium by digestive system Family history Smoking & excessive alcohol

consumption- both increase rate of bone loss

Low body weight Long term immobility Getting old!

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What causes osteoporosis?

99% of body’s calcium is found in skeleton

When diet low in calcium, body draws on reserves in bones to make up deficit

So advantage to “bank” more calcium in bones before reach peak bone density- in late 20s to early 30s

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What causes osteoporosis?

Oestrogen maintains bone tissue by stimulating the formation of new bone

Oestrogen enhances intestinal calcium absorption Limits calcium withdrawal from bone

Low oestrogen levels Reduce the activity of bone cells Increase risk of calcium loss from bones

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Exercise those bones!

Bones require regularweight-bearing exercise E.g. walking, dancing, jogging, tennis Why not swimming or cycling? Exercise:

Puts force through the bone to stimulate growth

Strengthens bones Strengthens tendons, ligaments & point of

attachment at joints

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Exercise those bones!

Resistance exercise also strengthens bones

E.g. weight training Bed-ridden individuals have increased

bone loss as do astronauts in zero gravity

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Treatment of osteoporosis

No cure! Can halt or reverse progress of disease

with: Exercise Oestrogen in form of HRT (hormone

replacement therapy) or calcium supplements

Caution choose exercise carefully if have osteoporosis – need moderate intensity- why?

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Treatment of osteoporosis

Prevention is better than cure: Regular weight bearing exercise Adequate dietary calcium & vitamin D

Both before late 20s

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Female athletes & osteoporosis

Extreme levels of exercise by young athletes can cause osteoporosis

Reason Very intensive training Restricted diet Combined reduce body fat Can cause periods to stop & drop in

oestrogen levels

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Female athletes & osteoporosis

Worrying as at a time of max potential bone growth

Some young athletes have bone density of women in their 70s

These bone losses are irreversible Female athlete’s triad

Intensive training & Restricted diet & Low body fat