Lecture 2- Mechanics of Locomotion

Question 1

Adductor

Answer 1

Towards median plane

Question 2

Abduction

Answer 2

Away from median plane

Question 3

Circumduction

Answer 3

Conical movement

Question 4

Flexion

Answer 4

Reduces the angle between bones

Question 5

Extension

Answer 5

Increases angle between bones

Question 6

How does pronation and supination occur

Answer 6

Rotation of proximal extremity of radius within ligament of ulna while the distal extremity is carried in an arc around the ulna

Question 7

Pronation

Answer 7

Rotates forepaw caudally

Question 8

Supination

Answer 8

Rotates forepaw cranially

Question 9

What bones are elongated in the horse

Answer 9

Radius, ulna, tibia, metacarpal-tarsals, phalanges

Question 10

Why do horses extend distal limb elements out of proportion to proximal

Answer 10

Their limb mass is concentrated close to the trunk. Moving distal elements which have a lower mass requires less muscle force

Question 11

What are some clinical implications to long tendons distally

Answer 11

Limb and joint disorders

Question 12

What is the role of synovial sheaths and retinacula

Answer 12

Act like pulleys for long tendons
Are sites of potential injuryw

Question 13

What is the advantage for elongated tendons

Answer 13

The short muscle belly and especially elongated tendon provides elastic energy storage and savings

Question 14

Describe the position of the distal tendons in a walking horse

Answer 14

Tendons stretch as the body weight falls onto foot and then elastic recoil occurs which shortens tendons to help raise body

Question 15

What muscles are important to maintain standing quadrupedal posture

Answer 15

Limb and back extensors

Question 16

Support phase

Answer 16

During heel strike the extended limb takes on all the weight so the swing limb can move

Question 17

Swing phase

Answer 17

Toe off to heel strike, limb swings from flexion in air to extension on ground

Question 18

Describe the patterns of flexor and extensor muscles during walking (EMG example)

Answer 18

When walking if the left flexor muscle fires then the left extensor is relaxed but the right extensor is contracted to support the weight and vice versa

Question 19

What muscles are recruited during support phase

Answer 19

Gluteals, quadriceps femoris, gastrocnemius

Question 20

What muscles are recruited during swing phase

Answer 20

Sartorius, cranial tibial muscles

Question 21

What muscles are activated during both swing and support phase

Answer 21

Hamstrings, iliopsoas and adductors