An ergometer to measure muscle bioenergetics with magnetic resonance techniques

Applying magnetic resonance methods to measure the metabolic response in exercise poses a technical challenge because the construction of the ergometer must use non-magnetic components and assess work in the confined space of a magnet bore. The present report details the fabrication of a non-magnetic ergometer for use in a standard Siemens 3 Tesla (T) spectrometer.  Using the ergometer, researchers can measure the 31P NMR signals during leg muscle exercise and exercise recovery. In particular, the phosphocreatine (PCr) kinetics during exercise recovery reflects the mitochondrial oxidative capacity, and the inorganic phosphate (Pi) signal tracks the cellular pH. The ergometer allows for a personalized, and variable load to be lifted leading to total work performed across study participants being similar regardless of their leg strength. The ergometer then enables a standardized magnetic resonance spectroscopy (MRS) comparison of leg muscle bioenergetics between study participants.

Methods
The data detail the construction and application of a non-magnetic ergometer that enables researchers to use magnetic resonance imaging/spectroscopy (MRI/MRS) methods to measure the metabolic changes in exercising human muscle in vivo as a function of work level relative to the maximum voluntary contraction (MVC).  Using the ergometer and MRI/MRS methods allows researchers to measure the 31P NMR signals from muscle and utilize the pH and phosphocreatine (PCr) to assess muscle bioenergetics during and after exercise.  Specifically, the recovery kinetics of the PCr immediately after the cessation of exercise provides a unique perspective on the   contrasting mitochondrial functions in normal and compromised muscle in patients suffering from different diseases, such as chronic kidney disease and on the efficacy of therapeutic intervention.