Active recovery intervals restore initial performance after repeated sprints in swimming

The purpose of this study was to examine the effects of active recovery (AR) and passive recovery (PR) using short (2-min) and long (4-min) intervals on swimming performance. Twelve male competitive swimmers completed a progressively increasing speed test of 7 × 200-m swimming repetitions to locate the speed before the onset of curvilinear increase in blood lactate concentration (LT₁). Subsequently, performance time of 6 × 50-m sprints was recorded during four different conditions: (i) 2-min PR (PR-2), (ii) 4-min PR (PR-4), (iii) 2-min AR (AR-2) and (iv) 4-min AR (AR-4) intervals. Blood lactate concentration was measured before the first and after the last 50-m repetition. AR was applied at an intensity corresponding to LT₁. Performance as indicated by the time needed to complete 6 × 50-m sprints was impaired after AR-4 compared to PR-4 (AR-4: 28.65 ± 1.04, PR-4: 28.17 ± 0.72 s; mean% difference: MD% ±s; ±90% confidence limits: 90%CL, 1.71 ± 3.01%; ±1.43%, p = .01) but was not different between AR-2 compared to PR-2 conditions (AR-2: 28.68 ± 0.85, PR-2: 28.69 ± 0.82 s; MD%: 0.03 ± 1.61%; 90%CL ± 0.77%, p = .99). Performance in sprint-6 was improved after AR compared to PR independent of interval duration (AR: 28.55 ± 0.81, PR: 29.01 ± 1.03 s; MD%: 1.52 ± 2.61%; 90%CL ± 1.2%; p = .03). Blood lactate concentration was lower after AR-4 compared to PR-4 but did not differ between AR-2 and PR-2 conditions. In conclusion, AR impaired performance after a 4-min but not after a 2-min interval. A better performance during sprint-6 after AR could be attributed to a faster metabolic recovery or anticipatory regulatory mechanisms towards the end of the series especially when adequate 4-min active recovery interval is applied.