Key Points
- To measure the energy balance and changes during isometric contractions of Rana temporaria's sartorius muscles.
- Unpoisoned sartorius muscles were tetanically stimulated for up to 20 seconds at 0 degrees C.
- Observed enthalpy production and chemical changes were measured and compared, particularly with n-phosphoryl creatine dephosphorylation.
- Evolution of unexplained enthalpy was characterized over the duration of contractions.
- Unexplained enthalpy (UE) production was most rapid during the first 750 ms of contraction and fell to zero by the 8th second.
- Total enthalpy after 8 seconds was fully explained by n-phosphoryl creatine dephosphorylation.
- The rate of production of labile enthalpy declined exponentially at approximately 1 s-1.
Structured PICO
PPopulationUnpoisoned sartorius muscles of Rana temporaria
IInterventionTetanic stimulation in isometric contractions lasting up to 20 s at 0 degrees C
OOutcomeTime-course of energy balance (observed enthalpy vs enthalpy explained by chemical changes)surrogate
The study demonstrates that unexplained enthalpy in isometric muscle contraction evolves rapidly initially but ceases after 8 seconds, indicating it is not derived from the same chemical reaction as labile enthalpy.