1/10/2013. Musculoskeletal Integration. What forces is a body subjected to on land? What forces is a body subjected to on land?

Transcription

1 Topic : Support & Locomotion on Land What forces is the body subjected to on land? Balance Posture Gait How is the vertebral column involved in locomotion? Support Movement How are the limbs involved in locomotion? Musculoskeletal Integration Muscles act on the skeleton to exert forces on the environment Body Worlds When moving impact from pushing off the ground component F = ma = mg = 9.8 x m component Landing for resisting these forces? for resisting forces an animal is subjected to on land? Photo PJB Liem et al. Fig. - for resisting these forces? GRF at impact is influenced by: Footwear Lieberman et al. 200

2 What forces is a body subjected to on land? GRF at impact is influenced by: Running technique Footwear Shoes Decrease Not impact force In balance COM within triangle of stability Out of balance COM falls outside of triangles Stability is proportional to width of triangles Who is more stable? Sprawling or erect posture? Fore-Foot Strike decreases Lieberman et al. 200 Liem et al. Fig. -9 How do vertebrates move? Sprawling Erect (can be bipedal) What posture does the chameleon have? Differ in orientation of limbs relative to body Vertebral function also differs Photos PJB, S Yamamoto Photos KP Bergmann Components Symmetrical gaits Left & Right limbs are ~50% out of phase Asymetrical gaits Left & Right limbs become in phase Liem et al. Fig. -9 2

3 Gait What do you notice happens as velocity increases? Liem et al. Fig. -20

4 Gaits Gaits are often poorly defined in sprawling vertebrates Suspension of viscera Connecting front & hind limbs Crocodylus johnstoni Can gallop More upright posture Often only two feet on the ground Restriction of Zygapophyses and torsion Centra and bending Neural spines with ligaments and bending A Britton Kardong Fig 8-30; Liem et al. Fig. -9, -8 What is the role of the vertebral column? Movement displacement Spralwers Enhanced stride length Movement displacement Erect posture Also enhances stride length Fast locomotion Gallop Bounding Pough et al. 2004, Fig. 0-2; PJB Vertebrate Life Fig 24-2; Liem et al. Fig. -26 Extreme lateral movement of movement Frogs Evolution of urostyle Reduction in vertebral number Bending only at sacroiliac joint Pough et al. Fig. 0-; PJB Liem et al. Fig. -27

5 What is the role of the limbs? Interface with substrate Minimize contact with substrate Decreased friction with body How do the roles of the front & hind limbs compare? Terrestrial Arboreal Jumping Adaptations for speed Lengthening of distal elements Increase Increase Arc length is the same - Distance travelled is proportional to limb length Photos KP Bergmann, National Geographic Liem et al. Fig. -22 The further distally you go: The longer the distance moved The greater the velocity Trade-off between speed and power What class of lever is this? How do the limbs differ in in-lever and out-lever? Liem et al. Fig. -24 Liem et al. Fig. -2 What is the role of the limbs? Consider the following: Fi x Li = Fo x Lo Fo = (Fi x Li) / Lo How do you increase force morphologically? Vo x Li = Vi x Lo Vo = (Vi x Lo) / Li Ho do you increase velocity morphologically? Gear Ratio = Lo / Li What does a low Lo / Li mean? What does a high Lo / Li mean? Liem et al. Fig. -2 2