['To elucidate cell free DNA (cfDNA) clearance kinetics following an acute bout of high intensity exercise by measuring circulating DNase activity reduction (AR).', 'Serum cfDNA concentration and DNase-AR were measured prior to and post (immediately post, 7 and 30 min post) an acute bout of rowing exercise until exhaustion.', 'Serum cfDNA concentration was significantly (P ≤ .001) elevated immediately post (2.5-fold) and 7 min post exercise (2.3-fold) with a return close to baseline at 30 min post exercise (1.5-fold). The rise in cfDNA was accompanied by a concomitant, significant (P ≤ .001) decrease in serum DNase-AR from 15.1% prior to exercise to 3.1% AR at cessation of the exercise test and 7 min post exercise (3.9% AR). DNase-AR returned close to baseline at 30 min post exercise (5.2% AR).'] Is exercise a potent stimulus for enhancing circulating DNase activity?