MECHANICAL WORK, ENERGY, AND POWER - Biomechanics and Motor Control of Human Movement - page 169

TABLE 6.2 Power Generation, Transfer, and Absorption Functions

Directions of
Segmental

Description of Type of Angular Muscle Amount, Type, and

Movement Contraction Velocities Function Direction of Power

Both segments rotating
in opposite directions

Concentric Mechanical energy

generation

M ω 1 generated to
segment 1
M ω 2 generated to
segment 2

(a) joint angle
decreasing

(b) joint angle
increasing

Eccentric Mechanical energy

absorption

M ω absorbed from
segment 1
M ω 2 absorbed from
segment 2

Both segments rotating
in some direction

Concentric Mechanical energy

generation and
transfer

M( ω 1 − ω 2 ) generated
to segment 1

(a) joint angle
decreasing (e.g.
ω 1 > ω 2 )

M ω 2 transferred to
segment 1 from 2

(b) joint angle
increasing (e.g.
ω 2 > ω 1 )

Eccentric Mechanical energy

absorption and
transfer

M( ω 2 − ω 1 ) absorbed
from segment 2

M ω 1 transferred to
segment 1 from 2

(c) joint angle constant
( ω 1 = ω 2 )

Isometric
(dynamic)

Mechanical energy
transfer

M ω 2 transferred from
segment 2 to 1

One segment fixed (e g
segment 1)

Concentric Mechanical energy

generation

M ω 2 generated to
segment 2

(a) joint angle
decreasing ( ω 1 = O 1

ω 2 > O)
(b) joint angle
increasing ( ω 1 = O 1
ω 2 > O)

Eccentric Mechanical energy

absorption

M ω 2 absorbed from
segment 2

(c) joint angle constant
( ω 1 = ω 2 =

Isometric (static) No mechanical

energy function

Zero

O)

From Roberston and Winter (1980). (Reproduced by permission from J. Biomechanics .)