Force, shortening, and work in muscular contraction: relative contributions to overall energy utilization

The amounts of energy used during muscular contraction under different loads have been compared by measurement of the total amount of disturbance of the concentration of reduced nicotinamide-adenine dinucleotide during the period of oxidative recovery. The results are in quantitative agreement with the concept that three parameters determine the energy utilization: namely the time-integral of the force development, the time-integral of the shortening process, and the mechanical work.