biomekanik dr.irfan
TRANSCRIPT
Biomekanik
Irfan Idris
Bagian Faal FK Unhas
Pendahuluan
Apa itu biomekanik ???
Anak usia 10-12 bulan mulai berjalan
Bagaimana pekerja menghindari LBP ?
Mengapa orangtua cenderung mudah jatuh ? Pakai tongkat ?
Ada orang yang dapat melakukan gerakan yang kompleks dengan mudah, tetapi ada yang tidak mampu melakukan gerakan yg sederhana
Definisi Biomekanik
The science involving the study of biological systems from a mechanical perspective
Use the tools of mechanics (branch of physics involving analysis of the action of forces) to study the anatomical and functional aspects of living organisms
Cabang utamanya : Static dan dynamics
Statics is the study of systems that are in a state of constant motion (rest or moving with constant velocity)
Dynamics is the study of systems in which acceleration is present
Kinematics is the description of motion including the pattern and speed of movement sequencing by the body segment that often translates to the degree of coordination an individual display
Kinetics is the study of the force associated with motion
Kinesiology : the study of human movement
Sport medicine : clinical and scientific aspects of sports and exercise The
American College of Sport Medicine
Masalah yang dipelajari
Binatang yang berkaki dua dan berkaki empat menggunakan energi yang sama saat bergerak; economy cost of energy (padahal berat badannya beda & jumlah otot yang terlibat beda)
Pada manusia, terdapat perbedaan individual “energy cost” saat lari dengan kecepatan tinggi
Latihan dan high altitude improve running economy; otot-otot menggunakan energi dan elastisitasnya lebih efisien
NASA : astronout yang hanya beberapa hari di luar angkasa atrofi otot, densitas tulang menurun (osteoporosis) terutama pada tulang kaki exercise (di luar angkasa)
Osteoporosis 40% usia > 50 thn dan 90% pada usia > 60 thn most common : vertebra & hip fracture
Usia tua gangguan keseimbangan : mudah jatuh (sway & fall)
Gait penderita cerebral palsy spastik dan muscle tension modifikasi otot hamstring, rectus femoris dan sartorius gait membaik
Amputasi prostetik yang mirip aslinya dapat digunaka sport/exercise
Occupational biomechanics is a field that focuses on the prevention of the work-related injuries Penelitian LBP akibat benda berat, posisi yg salah,
gerakan yg tiba2 & tdk direncanakan Pekerja harus siap secara fisik & mental pencegahan LBP
Carpal tunnel syndromes : repetitive keyboard use design keyboard yang sehat
Biomekanik penemuan sport equipment yang sehat Klapskate utk skating, aerodynamic helmet-clothes-cycle design utk olahraga bersepeda dsb
Biomekanik memperbaiki performance dan teknik atlit
Analisis biomekanik pada juara olimpiade lempar cakram 4 kali : mendapatkan lemparan yang maksimal bila : Speed of the discus when it is released by the
thrower The projection angle at which the discus is
released The height above the ground at which the discus
released The angle of attack (the orientation of the discus
relative to the prevailing air current)
Why study biomechanical ?
Why is swimming is not the best form of exercise for osteoporosis ?
What is the safest way to lift a heavy object ?
Is it possible to judge what movement are more/less economical from visual observation ?
At what angle should a ball be thrown for maximum distance ?
Why are some individuals unable to float ?
Beberapa aspek biomekanik tulang
Dua fase :
Fase 1 : mineral
Fase 2 : kolagen & substansi dasar
Aspek biomekanik yang terpenting dari tulang : kekuatan (strenght) dan kekakuan (stiffness)
Pembebanan (loading) untuk
mengerti aspek biomekanik pada tulang
B
A
C
D
D’
Ultimate failure
point
Plastic region
Yield
point
Deformation
Load
Load Deformation Curve for
pliable material
Strenght luasnya area dibawah curva
Stiffness makin curamnya slope elastic region
Load-deformation curve berguna
untuk mempelajari : karakter fraktur & repairing; respon tulang pada pembebanan; efek beberapa treatment pada tulang (prostetik implant)
Stress : load/force N/cm2 = Pascal
Strain : ketegangan linier (length
change) & shear (angular change)
A
B
C
B’
B” C”
C’
Strain (ε)
Str
ess (σ
)
E (elastisitas) = σ / ε
Curve stress-strain
E stiffness
Tulang cortical lbh kaku tulang cancellous (trabekular)
Tulang cortical dengan strain 1.5 – 2% fraktur; cancellous bone bisa tahan
strain sampai 50% sebab banyaknya pori-pori ~ banyaknya energi yang tersimpan
50
100
150
200
5 10 15 20 25 30
Strain %
Str
ess (
MP
a)
Cortical
bone
Trabecular bone
Mechanical behaviour of two bone
structures with compression test
metal
glass
bone
strain
str
ess
Beberapa aspek biomekanik pada otot
4 propereties :
Extensibility : increase length
Elasticity : return to the normal length (paralel elastic component/PEC and serial elastic component/SEC)
Irritability : ability to respond to a stimulus
Developed tension : contraction (contractile component)
SEC and PEC
SEC : tendon and contractile fiber
PEC : muscle membranes and muscles
Height of jump increase increased of
SEC lower extremity muscle
Increased muscle force increased
increased of PEC
Tipe otot
Karakteristik Type I (slow-twich oxidative)
Type IIA (Fast twich oxidative glycolytic/FOG)
Type IIB (Fast twich oxidative glycolytic/FG)
Kecepatan kontraksi
lambat cepat Cepat
Fatique lambat intermediate Cepat
Diameter kecil intermediate Besar
Jumlah ATPase rendah tinggi Tinggi
Jumlah mitokondria tinggi rendah Rendah
Jumlah enzim glikolitik
rendah intermediate Tinggi