Purpose This study compared the physiological effects of a moderate-intensity interval training (MIT) microcycle followed by an active recovery period (collectively termed MITblock) with a time-matched regular training period (REG) during the general preparation phase in well-trained cyclists. Methods Using a randomized crossover design, 30 well-trained male cyclists (maximal oxygen consumption (VO2max), 70.5 (4.6) mL·min-1·kg-1) completed both MITblock and REG. The MIT microcycle involved six interval sessions over 7 d with 5-7 × 10-14-min work intervals at a rating of perceived exertion (RPE) of 14-15 on the Borg 6-20 scale. A 6-d active recovery period followed before physiological testing. During REG, cyclists performed their regular preparatory-phase training routine, which primarily involved low-intensity exercise. Specific guidelines included completing either two MIT sessions or one MIT session and one high-intensity interval session per week. Endurance performance indicators assessed included changes in 15-min maximal average power output (PO15min), power output at 4 mmol·L-1 [blood lactate] (PO4mmol), 1-min peak power output during incremental testing (POVO2max), and VO2max. Results Although the Training Impulse (TRIMP) score was not different between MITblock and REG (1944 (436) vs 1800 (232), respectively; P = 0.27), MITblock resulted in significantly greater improvements than REG in PO4mmol (4.0% (4.4%) vs -1.3% (3.7%), P < 0.01), POVO2max (2.5% (4.5%) vs -0.7% (3.9%), P < 0.01), and VO2max (2.0% (3.9%) vs 0.0% (3.5%), P = 0.05). Changes in PO15min were not statistically different between MITblock and REG (3.9% (8.3%) vs 0.2% (6.8%), P = 0.14). During MIT intervals, rating of perceived exertion was 14.4 (0.3), corresponding to 66% (5%) of POVO2max, 85% (3%) of maximal heart rate, and 2.8 (1.1) mmol·L-1 [blood lactate]. Conclusions Six moderate-intensity interval sessions over 7 d, followed by a 6-d active recovery period, induce improvements in endurance performance indicators compared with a time-matched regular training period in well-trained cyclists.
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