l Evidence of energy exchange between PE(vertical height) and KE (horizontal velocity)
l Perfect exchanges of the PE and KE
l No energy exchange à totally in-phase energy components
: change in the total segment energy
max min Delta Es 29.30 13.14 16.16 Ep 15.18 13.02 2.16 Ekt 13.63 0.09 13.54 Ekr 0.95 0 0.95
=
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à
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e.g. ideal pendulum
- Eb = total body energy
- Considerations in interpretation of changes in Eb -
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t1~t2 : à counter clockwise, normal pendulum
t2~t3: à counter clockwise, m2 à activation, Ek ↑, Ep ↑, ∴Es ↑ t3~t4: pendulum
t4~t5: à counter clockwise, m1 à activation, Ek ↓, ∴Es ↓
- muscle power à decomposition into internal and external work
- external work: force measured at the interface between human and external load is required
l If the two segments are rotating in the same direction à energy transfer from one segment to the other
1. energy flow
A. negative à
à energy absorption by muscle from segment 1
B. à
à energy generation by muscle to segment 2
2. energy flow and transfer
A. à isometric contraction the same energy rate occurs
transfer of energy from segment1 to segment 2 via muscle
B. à muscle lengthening à energy absorption + energy transfer M(w2-w1) generated à M(w1 -w2) absorbed from segment 1 to muscle Only Mw2 transferred to segment 2 from segment 1
C. à muscle shortening à energy generation + energy transfer M(w2-w1) generated to segment 2 by muscle (energy generation)
Whole Mw1 transferred to segment 2 from segment 1 (energy transfer) Total power of segment2: Mw1 + M(w2-w1) = Mw2
- modified equation for the muscle mechanical (generated) power
à this equation and table 5.2 assumes that w1 and M are in the same direction à so that, in the above example, the equation must be Pm=M (w2-w1)
- Energy can enter or leave a segment at muscle and across joints - Transfer of energy
1. active: through muscle 2. passive: through joint
- Es (segment energy) from the law of conservation of energy
Kinematic data
,
, ,
Kinetic data
Energy data
