A, Treadmill exercise at 18 m/min initially elevated plasma lactate levels, but over time the exercise intensity needed to boost plasma lactate concentrations increased. Measurements were performed immediately after the completion of an exercise session. *P < 0.05 relative to the lactate levels of the SED mice. B, In LAC mice, plasma lactate levels peaked approximately 15 minutes after an intraperitoneal injection, remained significantly elevated for at least 1 hour, and returned to baseline by 3 hours. *P < 0.05 relative to the lactate levels of the VEH mice.