Original:  Lactate served as a metabolic fuel being produced and oxidatively disposed in resting and exercising muscle.
Revised:  However, lactate is continually formed at rest and during all exercise intensities. With the use of stable isotopic tracers URLe Brooks and colleagues, at the University of California, Berkeley, observed that lactate served as a metabolic fuel being produced and oxidatively disposed in resting and exercising muscle.
Edit intent: meaning-changed