Two‐pedal ergometer for in vivo MRS studies of human calf muscles

Abstract

This article describes an ergometer that enables human subjects to exercise one or both limbs while 31 P NMR spectra are obtained. Two independent pedals, equipped with position and force transducers, were mounted on the ergometer in order to calculate mechanical work performance. First, the effect of the magnetic field upon the signal coming from the transducers was investigated. Then the ergometer was tested by performing a series of steady-state exercises of increasing intensity. Experimental data showed that actual mechanical power ranged from 1.5 ؎ 0.2 W to 11.0 ؎ 1.6 W, while the corresponding oxygen consumption increased from 0.28 ؎ 0.04 l/min at rest to 0.48 ؎ 0.10 l/min at the highest load, and the PCr/(PCr؉P i ) ratio, as calculated from the 31 P spectra, decreased from 0.94 ؎ 0.01 at rest to 0.73 ؎ 0.04. These results are consistent with the values reported in the literature and show that this ergometer, which is easy to use, is suitable for in vivo spectroscopy research when metabolic steady-state conditions are required.

Influence of phosphagen concentration on phosphocreatine breakdown kinetics. Data from human gastrocnemius muscle

“…Indeed, during high-intensity exercise, muscle energy requirement is partially covered by lactate production, leading to the sparing of a certain amount of PCr at work onset, which is reflected by a slower PCr breakdown kinetics (28,54). In the present investigation, the ergometer used allowed the subjects to control accurately the frequency and amplitude of the ankle flexions thanks to the LED bar fixed at eye level (17). This helped the volunteers to attain the target exercise work rate, which was set below the intracellular lactate threshold (38).…”

“…Lying supine on a specially designed nonferromagnetic calf ergometer (17), each subject performed consecutively three exercise trials, separated by at least 10 min rest. Each trial consisted of 2.5 min rest followed by 6 min of rhythmic plantar flexion.…”

“…The exercise, of moderate intensity, consisted of synchronous plantar flexions of ϳ30°w ith both feet against the same force, provided by a given number and type of rubber band and at the same frequency of 0.83 Hz (imposed by a metronome), with the knee extended. The parameters determining actual mechanical power (i.e., number and type of rubber bands, frequency and amplitude of the flexions) were the same for all the volunteers and were chosen on the basis of our previous experience (17,18) to obtain an exercise intensity below the intracellular lactate threshold (38). Subjects were asked to carefully control the frequency and amplitude of the flexions; this last could be monitored on a light-emitting diode (LED) bar fixed at eye level.…”

Hybrid diffuse optical techniques for continuous hemodynamic measurement in gastrocnemius during plantar flexion exercise

“…PET is still reliant on the use of radioactive elements, and both require confinement to measurement tubes and limit the modalities of exercise that may be employed. 21,[23][24][25] The use of near-infrared (NIR) diffuse optical methods allows continuous, rapid, and noninvasive acquisition of local deep tissue hemodynamics. The optical window of tissue (600 to 950 nm) allows NIR source light to illuminate tissue several centimeters beneath the skin.…”

Mitochondrial coupling in humans: assessment of the P/O2 ratio at the onset of calf exercise

“…Subjects were asked to undergo, in random order, two experimental sessions during which they performed three times the same exercise trial, separated by at least 5 min rest, while lying supine on a variable resistance calf ergometer (Francescato and Cettolo 2001) built to perform exercises into a total-body NMR tomograph.…”