Figure 1. Schematic of the custom ergometer to measure the mechanical outputs of the knee extensors within the 3.0 Tesla scanner bore.
Custom ergometer designed and fabricated to accurately measure the mechanical performance of the knee extensors while simultaneously acquiring 31P-MRS to quantify skeletal muscle bioenergetics (A). The ergometer measured force production via an S-type load cell and displacements and velocities via a string potentiometer. Pneumatic dashpots minimized the eccentric portion of the movement cycle and provided a passive return of the limb to the starting position after each contraction. Representative mechanical signals from the beginning and end of the dynamic fatiguing exercise are depicted for a 76-year-old man (B). Also shown are the changes in intracellular pH and [Pi] from the same 76-year-old man performing the 4 min dynamic knee extension exercise (C).