This document discusses the energy sources and thermal changes that occur during muscle contraction. It notes that ATP is the immediate source of energy for muscle contraction, obtained initially from the hydrolysis of phosphocreatine and later through glycolysis and oxidative metabolism. Intense exercise leads to an oxygen deficit that is paid back after as oxygen debt. Muscle contraction results in the production of resting heat, initial heat during contraction, recovery heat after contraction, and relaxation heat. The efficiency of muscle contraction depends on whether it is an isotonic or isometric contraction.

1. DR NILESH KATE
MBBS,MD
PROFESSOR
DEPT. OF PHYSIOLOGY
ENERGY-SOURCE-AND-
THERMAL-CHANGES-
MUSCLE-CONTRACTION.

2. OBJECTIVES.
 ENERGY-SOURCE-FOR-MUSCLE-CONTRACTION.
 Hydrolysis-of-ATP
 Resynthesis-of-ATP
 Oxygen-demand-consumption-and-dept
 THERMAL-CHANGES-IN-MUSCLE-CONTRACTION.
 Resting-Heat.
 Initial-Heat.
 Recovery-heat
 Relaxation-heat

3. ENERGY-SOURCE-FOR-
MUSCLE-CONTRACTION.
 Machine-for-
conerting-chemical-
energy-into-
mechanical-work.
 Source-of-energy-ATP
 From-Metaolism-of-
Carohydrate-&-Lipids.
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4. ENERGY-SOURCE-FOR-
MUSCLE-CONTRACTION.
 Hydrolysis-of-ATP
 Resynthesis-of-ATP
 Oxygen-demand-consumption-and-dept
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5. HYDROLYSIS-OF-ATP
 ATP-initiate-
contractile-actiity-ATP
consumed-after-few-
twitches.
 In about 3 seconds, all
the ATP stored in the
muscle cell is depleted.
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6. RESYNTHESIS-OF-ATP
 Phosphorylation-of-
ADP-By-creatinine-
phosphate.
 Glycolysis
 Oxidatie-metaolism.
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7. Phosphorylation-of-ADP-By-
creatinine-phosphate.
 Dephosphorylation of
creatine phosphate
reserves of the muscle
fibre.
 Creatine phosphate +
ADP ⇔ creatine + ATP.
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8. Glycolysis
 Next energy source is
Glycogen to form ATP &
phosphocreatinine.
 Glycogen - previously
stored in the muscle cell
by the process of glycolysis
 Can sustain muscle
contraction for about 1
min
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9. Oxidative-metabolism.
 Combining of oxygen with various cellular
foodstuffs to liberate ATP
 Contributes more than 95% of all energy
used by the muscles for sustained long-term
contraction
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10. OXYGEN-DEMAND-
CONSUMPTION-AND-DEPT
 Oxygen-demand.
 Oxygen demand
increases with the
intensity of exercise,
i.e. intensity of muscle
contraction
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11. OXYGEN-CONSUMPTION.
 oxygen utilization is the volume of oxygen
which has been actually consumed during
the exercise.
 The maximum amount of oxygen that can be
consumed by a person while performing
severe exercise (irrespective of the demand)
is VO2 max
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12. OXYGEN-DEBT.
 During intense exercise,
 Oxygen consumed < Oxygen demand.
 So Energy requirement is met by the anaerobic
pathway.
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13. OXYGEN-DEBT.
 After exercise, extra O2 is consumed to remove
the excess lactate collected due to anaerobic
glucose breakdown, replenish the ATP &
phosphoryl creatine store & replace oxygen that
have come from the myoglobin
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14. OXYGEN-DEBT.
 This amount of extra oxygen consumed is
called O2 debt
 Proportionate to extent to which energy
demands during exercise exceeded the
capacity of aerobic synthesis of energy store,
i.e. extent to which oxygen deficit occurred
during exercise
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15. MECHANICAL-EFFECIENCY-OF-
MUSCLE.
 mechanical efficiency is equal to
Work done by the muscle (W)
------------------------------------------
Oxygen consumption (VO2)
OR
W (kilopond meter/min/426.7)
-----------------------------------
VO2 (L/min) × 5
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16. MECHANICAL-EFFECIENCY-OF-
MUSCLE.
 During isotonic
contraction
 Mechanical efficiency
is approximately 25%
of the energy
expenditure and rest
75% is degraded as
heat
 During isometric
contraction.
 As no external work is
done, therefore
mechanical efficiency
is nil and 100%
energy expenditure is
disappeared as heat
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17. CHANGES-IN-Ph-during-
muscle-contraction.
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18. THERMAL-CHANGES-IN-
MUSCLE-CONTRACTION.
 Resting-Heat.
 Initial-Heat.
 Recovery-heat
 Relaxation-heat
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19. RESTING-HEAT.
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Heat generated when the
muscle is at rest, i.e. not
contracting.
It is external manifestation
of the basal metabolic
process of the muscle.

20. INITIAL-HEAT.
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 Generated during muscular contraction.
• Generated when the muscle is at rest, i.e. not
contracting.
• Resting heat is the external manifestation of the
basal metabolic process of the muscle
Resting heat.
• Activation heat – before actual contraction of muscle
• Shortening Heat - when the muscle contracts isotonically
• Maintenance heat - no actual shortening of the muscle fibre
takes place.
Initial heat.
• Generated during the isometric contraction,
• When no actual shortening of the muscle fibre takes
place.
Maintenance
heat.

21. RECOVERY-HEAT
Heat produced in excess of resting heat following
muscle contraction.
Continues for about 30 min of the cessation of muscle
contraction.
Generated by the metabolic processes that restore the
muscle to its precontraction state
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22. RELAXATION-HEAT
Recovery heat,
which is
produced
during
relaxation of
the isotonically
contracted
muscle.
Fenn effect:
Fenn effect
states that the
heat produced
is directly
proportional to
the work done.
More work
done
causes
more
expenditur
e of energy.
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23. THANK YOU