Kinetic Chain

Question 1

Kinetic Chain

Answer 1

To understand movement we must understand how body segments interact

Question 2

What are the two types of kinetic chain movements?

Answer 2

Open and Closed Kinetic Chain movements.

Question 3

Name the chain: One end of the chain is fixed, the other is free to move

Answer 3

Open Kinetic Chain

Question 4

Name the chain: End of chain can move independently of the other end

Answer 4

Open Kinetic Chain

Question 5

Name the chain: Movement of proximal segment affects other segments, but cant always result in complete movement

Answer 5

Open Kinetic Chain

Question 6

Push-like movement pattern (OKC)

Answer 6

All segments moving simultaneously. Allows high force or high accuracy.

Question 7

Throw-like movement pattern (OKC)

Answer 7

Proximal segments moving prior to distal segments. Allows high movement velocities with less accuracy.

Question 8

Which pattern has simultaneous joint angle changes resulting in a straight path of distal segment?

Answer 8

Push-like movement pattern. Therefore, good for high-accuracy movements (OKC; dart throw, basketball free throw.

Question 9

Describe the movement in an OKC push-like pattern

Answer 9

Depending on orientation of segments, movement of proximal can influence distal. Proximal segments moved by large muscles (eg. gluteals, pectorals). Distal segments working off moving proximal segments allows large forces to be produced (torques at joints sum together - large resulting force)

Question 10

How does a throw-like pattern work to allow high movement speeds?

Answer 10

Two mechanisms:

1. Transfer of angular momentum
2. Storage and release of elastic energy

Question 11

Describe the transfer of angular momentum in an OKC throw-like pattern

Answer 11

Large muscles moving proximal segments can induce large momentum into the chain system (ie. move the large mass at high velocities)

Angular momentum (H) = moment of inertia (I) x angular velocity (w); H = Iw

Inertia = mass (m) x radius of gyration (k2); I = mk2

By suddenly stopping the proximal segment, the momentum is transferred to more distal segments (conservation of angular momentum)

If momentum is transferred along arm during throw, m and k decrease. Since momentum is conserved, w must increase. Therefore, with no muscle activity, velocity of distal segments increase rapidly

Question 12

Radius of gyration is…

Answer 12

• Distribution of mass with respect to a given axis of rotation
• Not same as centre of gravity, it changes as point of rotation changes
• e.g. It is easier to swing a baseball bat held by barrel because k is shorter (mass distributed closer to axis of rotation)

Question 13

OKC: Throw-like pattern (tendon involvement)

Answer 13

High speed movement most likely also results from elastic recoil of distal tendons

Question 14

Throw-like movements

Answer 14

Any movement where proximal segments accelerate distal segments by transfer of momentum are called ‘throw-like’ movements

Example: a kick, rotation of the body and acceleration of the thigh precedes knee extension

Question 15

Throw-like examples

Answer 15

Baseball swing- kinetic chain involves most segments of the body. Rotation of the body precedes the rapid arm swing.

Tennis players learn to ‘throw’ the racquet while still achieving a high level of accuracy

Question 16

Closed Kinetic Chain (CKC)

Answer 16

Both ends of the chain are fixed.

No part of the chain can move independently of the other.

Movement at the most proximal link can theoretically result in a completed movement.

Question 17

CKC: Push-like Pattern

Answer 17

Simultaneous joint angle change leads to a push-like movement pattern

Ideal for high force production because the forces sum

End point of chain limited to moderate and low movement velocities; determined by speed of muscle shortening.

Question 18

Control of chain systems

Answer 18

Both mono and biarticular muscles contribute to forces in limbs

Monoarticular muscles cross one joint and so are activated to directly cause joint motion

Biarticular muscles cross two (or more) joints so contribute to more than one motion

E.g. Rectus femoris flexes hip and extends knee
Gastrocnemius flexes knee and plantarflexes ankle

Question 19

When are biarticular muscles useful?

Answer 19

When two simultaneous movements are performed concurrently, e.g. Hip flexion and knee extension in kicking

They can also redistribute muscle torque, power and mechanical energy through a limb, e.g. Power of hip extension during a VJ can aid knee extension if rectus femoris remains isometric

Question 20

Specificity of chain systems

Answer 20

• controlling open and closed chains requires different muscle activation
• muscle activation can be altered by training, but changes are specific to training (specificity principle)
• therefore need to train movements specifically
• rehab and performance