Bone Biomechanics - Aging

8/13/2019 Bone Biomechanics - Aging

1/59

KETCHAMEXERCISE BIOMECHANICS KINE426

Bone Biomechanics:

Aging

November 13, 2006


2/59


Aging and Bones

Bone mass peaks at age 20

Bone mass and density can be maintained between20-40

Bones start to lose mass and density at age 40

some athletes may keep bone mass to age 50

Loss of bone mass is greatest between 50-60


3/59


Aging and Bones

spine


4/59


Aging and Bones

forearm


5/59


Spine BMD with Age

Aging and Bones


6/59


Bone and Aging

1% loss per year, 2-3% in osteoporosis

Why?

Changes in calcium regulating hormones

Decreased perfusion of bone tissue due to

changes in bone blood flow

Changes in the properties of bone mineral

material

Decrease in the number and metabolic

activity of cells that produce bone


7/59


Changes in Bones with Aging

Bonemass

Age (yrs)

80605040302010

Critical bone mass

70

Males

Females


8/59



Up to age 40

osteoblast activity = osteoclast activity (bone is

absorbed and replaced in a steady state fashion)

Ages 40-50

men, women similar in bone mass, density

After age 50

women may lose 50%or more of cancellous bonemass (post-menopause)

men may lose 25%or more of cancellous bone mass


9/59


Bone and Aging


10/59


Bone and Aging


11/59


Bone and Aging

3 Major Factors lead to bone loss:

Changes in bone-related hormones

Estrogen, testostorone, growth hormone

Dietary deficiencies Low intake of calcium and Vitamin D rich foods

Decreased physical activity


12/59


Hormonal Changes

Menopausal related

Withdrawal of estrogenreduces absorptionof Ca2+in intestine

Calcitonin and Vitamin-D metabolitesdecrease

Regulate Ca2+homeostasis

Increase in parathyroid hormone

Favor resorption of bone rather thanformation


13/59


Hormonal Changes - Treatments

Adding 170mg of Ca2+ daily nearly doubles

bone density over 1yr.

Injection of vitamin D and estrogen showpromise for bone restoration (1991)

Combination of Ca2+,

vitamin D and exercisedecrease bone loss


14/59

KETCHAMEXERCISE BIOMECHANICS

KINE426

Diet

Inadequate levels of Ca2+, vitamins and

mineral in diet

Elderly eat less and dont include calcium rich

foods Lose ability to produce vitamin-D metabolites

from exposure to sun

Important in Ca

2+

utilization in bone


15/59

KETCHAMEXERCISE BIOMECHANICS

KINE426

DietTreatments

Meta-analysis (several studies)

Women who didnt take Ca2+supplements

2% bone loss in early menopause per year

Women who did 0.8% bone loss in early menopause per year

Women should ingest min of Ca2+

1000mg/day

Post-menopausal1500mg/day


16/59


17/59


Bone and Aging


18/59



Relative strength after age 40 decreases 4-5%

per 10 years

No change in stiffness with aging Strain to failure after age 40 decreases 8% per 10

years

Energy absorbed to failure decreases 7-8% per10 years


19/59


Aging and Bones

Common sites of fractures

(1) neck of femur (hip)

(2) thoracic vertebrae

(3) distal radius

Cancellous bones

Affected more than

Cortical bone


20/59


Aging and Bone


21/59


Aging and Bones cancellous bone

50 yrs

80 yrs


22/59


Aging and Bones

cortical bone


23/59


Because of the high bone cartilage

content in young bones: lower strength

bones are less stiff

lower energy to failure

large strain to failure


24/59


BONE

Maturation


25/59


Bone Development and Bone Health

Children need regular exercise (especially pre-puberty)

Watch overtraining, high impact sports!

Reduces their risk of osteoporosis

Systemic effect/advantage may be reduced iftraining stopped

ex. soccer: arm vs. leg


26/59


Bone Injuries

Traumatic - single event or lowfrequency

Very Highload(low frequency)

Unusual type of loads One which the skeletal structure isnt

designed to handle.

Combination loads

shear + bending + torsion + compression,etc.


27/59


Bone Injuries

Materials Fatigue - repeated loads

dont give bone chance to recover

Materials fatigue or overuse or "stress fracture"

Very High frequency(moderate to high loads) Nutritional and hormonalfactors increase risk

ex. low Ca2+intake, low estrogen levels


28/59


Bone Injuries

Fractures

avulsion (tensile)Often accompaniestendon and ligament injuries.

spiral (torsion) impacted (compression)

fatigue or stress fracture


29/59


Minimizing Risk of Suffering a Stress

Fracture

Use proper protective equipment (i.e., helmets,footwear, etc.)

Be careful exercising when fatigued

Avoid coming back too soon after an injury

Proper off-season or pre-season training (pre-hab) Avoid switching sports or events without proper

training

Take occasional days off

Start slowly when initiating training


30/59


Stages of Rehabilitation after

Bone FractureWhen bone fractures, soft tissue must absorb

released energy exacerbating damage

Immediate Treatment (RICE)Rest

Ice

Compression

Elevation


31/59


Therapeutics after Fracture

GOAL: quick restoration of normalfunction

Set fracture, limitedimmobilization

Reconditioning

Passive, ROM exercises

Active exercises(involves muscle contractions)

Modhigh reps; low mod intensity


32/59


Rehabilitation after Connective

Tissue Injuries Reconditioning

Increase blood flow

increase mechanical action

Protection of joint cartilage from atrophy, loss

of cushioning decrease scar tissue

Some mechanical stress needed to promotehealing


33/59


Immobilization

Reduces mechanical stress around area ofbone which has suffered fracture

However, plaster and fiberglass casts(non-removable) weaken bone overall


34/59


Immobilization - 8 wks

stres

s

strain

immobilization

normal


35/59


Osteoporosis

Critical reduction in bone mass to the point

that fracture vulnerability increases

Affects cancellous bone more than cortical

bone


36/59


Osteoporosis

A disease characterized by low

bone mass and structural

deterioration of bone tissue,

leading to bone fragility and an

increased susceptibility to

fractures of the hip, spine,and wrist.


37/59


38/59


Osteoporosis- Health Implications

55% of the people 50 years of age and older,have low bone mass: risk of developingosteoporosis and related fractures

Often thought of as an older persons disease, itcan strike at any age.

Responsible for more than 1.5 million fracturesannuallyincluding: 300,000 hip fractures 700,000 vertebral fractures 250,000 wrist fractures 300,000 fractures at other sites


39/59


Risk Factors For Osteoporosis

Risk Factor High Risk Low RiskFamily history yes no

Ethnic background Caucasian African-American

Frame size small largeGender female male

Amenorrhea yes no

Menopause early late

Given birth no yesAge over 50 yes no


40/59



Risk Factor High Risk Low RiskWeight underweight overweight

Physical activity sedentary regular

Smoking yes no

Calcium intake low high

Vitamin D intake low adequate

Soft drink intake high low


41/59



Risk Factor High Risk Low RiskFiber intake high moderate

Alcohol intake high low/moderate

Caffeine high low or none

estrogen low normal

parathyroid hormone low normal


42/59


Exercise and Osteoporosis in

Female Athletes??

15 yrs ago: scientist found some young female athleteshad bone loss (osteopenia) in the spine

some had bone mineral content similar to elderly women


43/59


OSTEOPENIA in

Young Female Athletes

Female Athlete Triad (poor nutrition,amenorrhea, bone loss) occurs in small # but significant % of

population of athletes, active instructors

most common in running, gymnastics,aerobics instructors

associated with disturbances in menstrualcycle

Greater reduction in estrogen


44/59

E i d O t i i


45/59


Exercise and Osteoporosis in

Female Athletes

0

20

40

60

80

100

120

140

sedentary

athletes

amenorrheic

athletes

%sedenta

ry


46/59


Intervention for

Female Athlete Triad

If nutrition, low caloric intake, overtraining, andlow % body fat issues are addressed, normal

menstrual cycle usually resumes

Partial recovery of bone mass noted (long-termeffect unknown?)

Intervention for


47/59


Intervention for

Female Athlete Triad

Educationof coaches, athletes to thisproblem while the athletes are teens isabsolutely critical. Improvement - last 10 years - college +

Concern now - teens, youth sports

Luteinizing hormone (LH; pituitary hormone needed forovulation) 6 months before disturbances in menstrualcycle.

Screening/prevention tool???

Blood draws over 24 hours, expensive


48/59


Intervention for Osteoporosis

Prevention - maximize bone growth duringgrowth phase, maintenance phase; some boneloss with age appears inevitable.


49/59



Exercise - both weight bearing and weight

training; however, avoid overtraining


50/59



Calcium supplementation Good overall nutrition

Watch out for: yo-yo diets

rapid weight loss Hormone Replacement Therapy

Estrogen: post-menopausal, amenorrheic women

"designer estrogens" - raloxifene (68% reductionin fractures)

calcitonin (nasal spray)

parathyroid hormone


51/59

Studies have shown that a combination of these


52/59


therapies is more effective than one alone against

osteoporosis!

Notelovitz et al.,

1990

Ch i M h i l St


53/59


Changes in Mechanical Stress-

Bone Adaptations

Wolff's Law - Bone remodels according to functionaldemands

Not tested until the 1960s

Exercise as a health therapeutic agent

Spaceflight


54/59

B l i h S fli h


55/59


Bone loss with Spaceflight

Exposure to the spaceflight causes men and women of allages to lose up to 1% of their bone mass per month due todisuse atrophy. (height increases by 2+ in! - swelling ofvertebral discs)

It is not yet clear whether losses in bone mass will continue as

long as a person remains in the microgravity environment or

level off environment or level off in time.


56/59


Comparing Spaceflight and Inactivity

Changes in Spaceflight rapid - similar initially to immobilization.Slower with inactivity, but progressive.

Decreases in loading, growth factors, decrease in osteoblast activity

(decreased formation), increased osteoclast activity (resorption)

Reduced physical activity is characteristic of aging and could well be a

factor in the loss of bone, but researchers have not yet determined

how much of a role disuse plays on Earth.

E i i S


57/59


In order to exercise on thisergometer, the astronautmust be held down withshoulder pads.

Strategies

Compression - Exercises

Vibration

Electrical Stimulation

Vitamin D

Ca2+

Exercise in Space


58/59


Exercise and Bone Health

Wolff's Law - Bone remodels according to functional

demands

Exercise increases mechanical stress and strain,

growth hormone levels which contribute to increasing

bone mass and density

Stronger, stiffer, and able to store more energy

However, overtraining, especially in children and

older adults is counterproductive.


59/59

Documents

Bone Biomechanics - Aging