LLLT was applied to the femoral quadriceps muscle using an infrared laser device ( 830 nm ) , 0.0028 cm ( 2 ) beam area , six 60 mW diodes , energy of 0.6 J per diode ( total energy to each limb 25.2 J ( 50.4 J total ) , energy density 214.28 J/cm ( 2 ) , 21.42 W/cm ( 2 ) power density , 70 sec per leg .