High-intensity interval training (HIIT) is all the rage. Exercise of such intensity places huge demands on the anaerobic energy systems and causes lactic acid to accumulate in the blood.
Elevated concentrations of lactic acid can irritate the nerve endings and produce pain, discomfort and distress as well as labored breathing and fatigue. To expedite recovery, it’s important to clear the lactic acid from the bloodstream as quickly as possible.
Researchers assigned 12 males (average age 22.4) who were physically active to run on a treadmill at about 9.32 miles per hour on a 20% incline for two 30-second work intervals with a recovery interval of one minute of walking in between. This was enough “to induce fatigue and raise blood lactate to unsustainable levels.”
Immediately after completing the second work interval, the subjects were randomly assigned to use an active recovery of four different intensities, a self-selected intensity or a passive recovery (complete rest).
The study found that activity recovery of higher intensities cleared lactic acid from the blood much more rapidly than passive recovery. What this means is that after HIIT, jogging a few quick laps would be better than walking a few slow laps or simply standing still.
DEVLIN, J., ET AL. “BLOOD LACTATE CLEARANCE AFTER MAXIMAL EXERCISE DEPENDS ON ACTIVE RECOVERY INTENSITY.” THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS, 54, NO. 3 (JUN 2014): 271-78.
Matt Brzycki is the Assistant Director of Campus Recreation, Fitness at Princeton University. He has more than 30 years of experience at the collegiate level and has authored, co-authored and edited 17 books.