Resumen de Muscle Injury After Low-Intensity Downhill Running Reduces Running Economy

Cory W. Baumann, Michael S. Green, J. Andrew Doyle, Jeffrey C. Rupp, Christopher P. Ingalls, Benjamin T. Corona

• Contraction-induced muscle injury may reduce running economy (RE) by altering motor unit recruitment, lowering contraction economy, and disturbing running mechanics, any of which may have a deleterious effect on endurance performance. The purpose of this study was to determine if RE is reduced 2 days after performing injurious, low-intensity exercise in 11 healthy active men (27.5 ± 5.7 years; 50.05 ± 1.67 V[Combining Dot Above]O2peak). Running economy was determined at treadmill speeds eliciting 65 and 75% of the individual's peak rate of oxygen uptake (V[Combining Dot Above]O2peak) 1 day before and 2 days after injury induction. Lower extremity muscle injury was induced with a 30-minute downhill treadmill run (6 × 5 minutes runs, 2 minutes rest, -12% grade, and 12.9 km·h-1) that elicited 55% V[Combining Dot Above]O2peak. Maximal quadriceps isometric torque was reduced immediately and 2 days after the downhill run by 18 and 10%, and a moderate degree of muscle soreness was present. Two days after the injury, steady-state V[Combining Dot Above]O2 and metabolic work (V[Combining Dot Above]O2 L·km-1) were significantly greater (4�6%) during the 65% V[Combining Dot Above]O2peak run. Additionally, postinjury V[Combining Dot Above]CO2, VE and rating of perceived exertion were greater at 65% but not at 75% V[Combining Dot Above]O2peak, whereas whole blood-lactate concentrations did not change pre-injury to postinjury at either intensity. In conclusion, low-intensity downhill running reduces RE at 65% but not 75% V[Combining Dot Above]O2peak. The results of this study and other studies indicate the magnitude to which RE is altered after downhill running is dependent on the severity of the injury and intensity of the RE test.