PERANCANGAN KERJA MANUAL & Gerakan Therblig Pertemuan 4

MAXIMUM MUSCLE STRENGTH (Prinsip Motion Economy 1) 100 50 (% of Maximum) Isometric Force 50 100 150 Complete Contraction Complete Extension Length of Contractile Element (% of Resting Length) Relaxed Posture assumed by People in Weightless Conditions

Hasil Penelitian HUNSICKER Gerakan Menarik dan mendorong merupakan Gerakan Terkuat Kekuatan tersebut tergantung pada Sudut Gerak Menarik mencapai kekuatan maksimum pada sudut 150 Gerak Mendorong mencapai kekuatan Maksimum pada sudut 180

Hasil Penelitian Provins dan Salter (1955) dan Singh dan Kaporvich (1966) Posisi forearm terhadap Sumbu Siku Sudut siku 900 menberikan gaya momenmaksimum pada FLEKSI DAN EKSTENSION

TENSION Tension yang dapat dihasilkan Otot Tergantung pada : Luas penampang Otot Panjang Otot : Panjang Otot pd Complete Contraction (50% dari Panjang Otot Sewaktu Istirahat) sd Complete Extension (SD 180% Panjang Otot sewaktu Istirahat ) Streched : Terentang. Minimal Overlap / ikatan antara Actin dan Myosin. Berkurangnya Gaya Otot Hingga 0. Istirahat Posisi Optimum untuk Tegangan, Posisi Netral, Sekitar Midpoint pada Normal Range dari Gerakan Contracted : Actin dan Myosin membentuk Cross Bridge. Cross Bridge ini Menghasilkan Tegangan Otot . Complete Contracted State : Berkurangnya Gaya Otot, karena gangguan pada Actin, sehingga Ikatan optimum terganggu.

Menghasilkan Gaya Otot yg Menggerakan Bagian Tubuh HUMAN STRENGTH DYNAMIC STRENGTH : Menghasilkan Gaya Otot yg Menggerakan Bagian Tubuh STATIC STRENGTH : Tertahannya Gerakan Bagian Tubuh PSYCHOPHYSICAL STRENGTH : Strength Demands are Required for an Extended Period of Time

ISOTONIC CONTRACTION : ISOMETRIC CONTRACTION : DYNAMIC STRENGTH < STATIC STRENGTH More Efficient Bonding In the Slower Sliding Muscle Filaments GAYA ISOTONIS / ISOTONIC CONTRACTION : Memanjang dan Memendeknya Otot Dengan Menghasilkan Kerja Konsentris : Memendeknya Otot sambil Tetap Menahan suatu Tegangan (Kerja Positif) Eksentris : Memanjang Otot sambil Tegangan (Kerja Negatif) GAYA ISOMETRIS/ ISOMETRIC CONTRACTION : Gaya Otot tanpa Menghasilkan Kerja Diukur oleh : CONSTANT VELOCITY (ISOKINETIC) DYNAMOMETER

MAXIMUM STRENGTH With SLOW MOVEMENT (Prinsip Motion Economy 2) The faster the molecular bonds are formed, broken and reformed, the Less Effective is the bonding and the less muscular force is produced Force – Velocity Relationship Heavy Manual Work 0 50 100 100 50 Velocity (% of Maximum No Load-Velocity) (% maximum) Force Maximum Muscle Force dihasilkan dari : No Externally Measurable Shortening (Velocity 0 or Static Contraction) Minimum Muscle Force dihasilkan dari : Maximum Velocity of Muscle Shortening Force is only sufficient to move the mass of the body

USE MOMENTUM TO ASSIST WORKERS WHEREEVER POSSIBLE : Minimize It if It Counteracted by Muscular Effort (Prinsip Motion Economy 3) Faster Movements Higher Momentum + Higher Impact Forces Downward motions are More Effective than Upward Motions USE LARGE MUSCLES FOR TASKS REQURING STRENGTH (Prinsip Motion Economy 5) Muscle Strength = f ( Size of Muscle) Size of Muscle = Cross Sectional Area = f ( Posture) Ex : Heavy Load Lifting : Leg and Trunk Muscles

DESIGN TASKS TO OPTIMIZE HUMAN STRENGTH CAPABILITY (Prinsip Motion Economy 4) Human Strength Capability depends on : The Type of Strength The Muscle or Joints Motion being Utilized Posture Individual Factors : Gender, (The Largest Effect) Age,’ Handedness Fitmess/Training ARM LIFTING STRENGTH TEST LEG LIFTING STRENGTH TEST STATIC STRENGTH POSITIONS Range of Strength in the Normal, Healthy Adult population = The Strongest = (5 to 8) x The Weakest TORSO LIFTING STRENGTH TEST

Menghasilkan Gaya Otot yg Menggerakan Bagian Tubuh ENERGY SOURCES, STRENGTH AND FATIGUE AEROBIC ANAEROBIC ATP+02 ADP + ENERGI+CO2+H20 ATP ADP + ENERGI+LACTIC ACID Energy for a very Small Period of Time Arterioles + Capillaries : Compressed Blood Flow and O2 Fatigue HUMAN STRENGTH DYNAMIC STRENGTH : Menghasilkan Gaya Otot yg Menggerakan Bagian Tubuh STATIC STRENGTH : Tertahannya Gerakan Bagian Tubuh

Endurance Time = T STAY BELOW 15 % OF MAXIMUM VOLUNTARY FORCE (Prinsip Motion Economy 6) 100 % Maximal Contraction, Endurance Time = 6 Seconds 15 % Maximal Contraction, Endurance Time = Indefinite ! 5 – 10% (Jonsson,1978) The Amount of Rest Needed to Recover from Static Hold = Relaxation Allowances = f ( Force Exerted, Holding Time) Endurance Time (min) Exertion Level ( % Max Muscle Forces) 20 40 60 80 100 15% 10 5 6 sec Indefinite time Endurance Time = T T = 1.2 / (f – 0.15)0.618 – 1.21 f = Required Force, fraction of Maximum Isometric Strength

USE SHORT, FREQUENT, INTERMITTENT WORK-REST CYCLES (Prinsip Motion Economy 7) % of Maximum Strength 0 5 10 15 20 25 30 90 85 80 75 70 65 60 Contraction/min Repeated Static Contraction ( bawa barang dgn siku flexi), or dynamic work (mencangkul), Short time and Frequent cycle A Much Higher Percentage of Maximum Strength can be Maintained if the Strength is Exerted as a Series of Repetitive Contractions rather than One Sustained Static Contraction. Complete muscle fatigue several hour recovery

DESIGN TASKS SO THAT MOST WORKERS CAN DO THEM (Prinsip Motion Economy 8) Muscle Mass Muscle Fiber Strength 0 10 20 30 40 50 60 70 CHANGES IN MAXIMAL ISOMETRIC STRENGTH WITH AGE 0 20 40 60 80 100 Male Female Average Female Strength = (35% to 85%) x Average Male Strength Or 66 % x Average Male Strength % Variation in Muscle Strength Age Years Greatest for Upper Extremity Strength and Smallest for Lower Extremity Strength = = f ( body size or Total Muscle Mass) By a Strength Training Program Increase Strength 30% - 100%, in the First Several Weeks

USE LOW FORCE FOR PRECISE MOVEMENTS OR FINE MOTOR CONTROL (Prinsip Motion Economy 9) CNS CEREBELLUM SPINAL CORD Higher Muscle Forces need Increasing Size of Motor Unit 0 10 20 30 40 50 60 70 80 90 100 Force (% maximum) Electrical Impulse Muscle Contraction Motor Neuron 1 neuron has connection with (<10 for Small and >1000 For the large calf muscle) Muscle Fibers MOTOR UNIT 0 25 50 75 100 Motor Unit Recruited (% of maximum) Initially, Motor Unit Small in size (1 or 2) Produced Low Forces Change in Force is very gradual Fine Precision Motor Control

Lifting Heavy Containers Needs Precise Work : DO NOT ATTEMP PRECISE MOVEMENT OR FINE CONTROL IMMEDIATELY AFTER HEAVY WORK (Prinsip Motion Economy 10) Lifting Heavy Containers Needs Small Motor Unit and Larger one Unload : Some Smaller Motor Unit will fatigue Precise Work : Some small precise Motor Units are not available Larger motor Unit recruited to replace the fatigue one Larger Increments in force, less precise motor Control

USE BALLISTIC MOVEMENT FOR SPEED (Prinsip Motion Economy 11) Agonist : Penggerak Utama Gerakan BICEPS BRACHIORADIALIS TRICEPS Antagonist : Melawan Gerakan Spinal Reflex, Agonist and antagonist always occur In Short ( < 200 Msec), the Agonist is activated, the Antagonist is inhibited Speed

12. Begin and End Motions With Both Hand Simultaneously 13. Move the Hands Symmetrically and Simultaneously to and from the Centre of the Body Both hands should not be idle at the same time Both hands can work at the same time, making symmetrical moves in opposite direction

easier to produce curved motion than straight line 14. Use the Natural Rhythms of the Body Spinal Reflex, Agonist and antagonist always occur Natural rhythms Menyekop 14 – 17 x / menit Hentakan kaki 60 - 72 x / menit Hentakan tangan 35 x / menit 15. Use Continuous Curved Motion Body segment linkage easier to produce curved motion than straight line

16.Use the Lowest Practical Classification of Movement Finger motion Finger and wrist motions Finger, wrist, and lower arm motions Finger, wrist, lower arm and upper arm motions Body motion Longer time 17. Work with Both Hands and feet Simultaneously By feet if both hands are occupied !

18. Minimize Eye Fixations Location of visual target !! Normal line sight = 150 below the horizontal Primary visual field = the cone ± 150 in arc centered on the line of sight

EFFECTIVE THERBLIG Menjangkau (Reach) NO THERBLIG DESKRIPSI 1 Menjangkau (Reach) Gerakan tangan berpindah tempat tanpa beban Release Reach Grasp 2 Membawa (Move) Perpindahan tangan dgn membawa beban. Grasp Move Release / Position 3 Memegang (Grasp) Gerakan tangan dengan menutup objek dgn jari2 tangan Reach Grasp Move 4 Melepas (Release) Melepas objek yang dipegang sebelumnya

EFFECTIVE THERBLIG 5 Mengarahkan Awal (Pre-Position) 6 Memakai (Use) 7 NO THERBLIG DESKRIPSI 5 Mengarahkan Awal (Pre-Position) Mengarahkan Objek pada suatu tempat sementara, Tujuannya adalah untuk memudahkan pemegangan apabila objek akan dipakai kembali. Bersamaan dengan memakai, membawa atau melepas 6 Memakai (Use) Tangan dipergunakan untuk memakai/Mengontrol alat/objek dgn tujuan tertentu 7 Merakit (Assemble) Menggabungkan satu objek dengan yang lainnya. Move/Position  Assy  Release 8 Melepas Rakit (Disassemble) Objek dipisahkan dari rakitan Grasp  Disassemble  Move/Release

INEFFECTIVE THERBLIG NO THERBLIG DESKRIPSI 1 Mencari 2 Memilih (Search) Menemukan lokasi objek. (Mata atau tangan. 2 Memilih (Select) Menemukan/memilih objek diantara 2 atau lebih objek yang sama lainnya. Search Select 3 Mengarahkan (Position) Menempatkan objek pada lokasi yang dituju secara tepat Move Position Assy/ Release 4 Memeriksa (Inspect) Membandingkan objek dengan standar, dgn penglihatan atau indra lainnya 5 Merencana (Plan) Berhenti sejenak bekerja dan memikirkan untuk menentukan tindakan-tindakan selanjutnya.

INEFFECTIVE THERBLIG NO THERBLIG DESKRIPSI Kelambatan Tak Terhindarkan 6 Kelambatan Tak Terhindarkan (Unavoidable Delay) : Diluar kendali operator. 7 Kelambatan yg dapat di hindarkan (AvoidableDelay) 8 Rest to Overcome fatigue 9 Memegang untuk Memakai (Hold) Satu tangan memegang objek, yang lain bekerja

UPAYA PERBAIKAN DENGAN MENGHINDARI : NO GERAKAN UPAYA PERBAIKAN DENGAN MENGHINDARI : 1 Mencari Ciri ? Tata Letak? Pencahayaan? Tempat Penyimpan Tembus Pandang ? 2 Memilih Objek =, tempat =?, Interchangeability? Tempat Penyimpanan? 3 Memegang Dipegang Sekaligus? Hanya Kontak? Memudahkan? Peralatan pembantu ? 4 Menjangkau Perpendek? 5 Membawa Perpendek? Efektif?Pemakaian Anggota Tubuh? Sekaligus? Perubahan Arah GErak? Gravitasi? 6 Melepas +membawa?Penampung?Delay setelahnya? Melepas Sekaligus? 7 Mengarahkan Alat Penuntun? Apakah Diperlukan?

UPAYA PERBAIKAN DENGAN MENGHINDARI : NO GERAKAN UPAYA PERBAIKAN DENGAN MENGHINDARI : 8 Mengarahkan Awal 9 Merencanakan 10 Memeriksa Digabungkan dengan gerakan lain? Dihilangkan?Alat Inspeksi? Waktu? 11 Merakit 12 Mengurai Rakit 13 Memakai Peralatan pembantu? Sekaligus? Efisien? 14 Kelambatan Tak Terhindarkan 15 Kelambatan Terhindarkan 16 Merencanakan 17 Istirahat Untuk Melepas Lelah