A Moderate-Intensity Interval Training Block Improves Endurance Performance in Well-Trained Cyclists

ABSTRACT Purpose This study compared the physiological effects of a moderate-intensity interval training (MIT) microcycle followed by an active recovery period (collectively termed MIT block ) 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 (VO 2max ), 70.5 (4.6) mL·min -1 ·kg -1 ) completed both MIT block and REG. The MIT microcycle involved six interval sessions over seven days with 5-7 × 10-14 min work intervals at a perceived exertion (RPE) of 14-15 on the Borg 6-20 scale. A six-day 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 (PO 15min ), power output at 4 mmol·L -1 [blood lactate] (PO 4mmol ), 1 min peak power output during incremental testing (PO VO2max ), and VO 2max . Results Although the Training Impulse (TRIMP) score was not different between MIT block and REG (1944 (436) vs. 1800 (232), respectively; p = 0.27), MIT block resulted in significantly greater improvements than REG in PO 4mmol (4.0 (4.4)% vs. -1.3 (3.7)%, p < 0.01), PO VO2max (2.5 (4.5)% vs. -0.7 (3.9)%, p < 0.01) and VO 2max (2.0 (3.9)% vs. 0.0 (3.5)%, p = 0.05). Changes in PO 15min were not statistically different between MIT block and REG (3.9 (8.3)% vs. 0.2 (6.8)%, p = 0.14). During MIT intervals, RPE was 14.4 (0.3), corresponding to 66 (5)% of PO VO2max , 85 (3)% of maximal heart rate, and 2.8 (1.1) mmol·L -1 [blood lactate]. Conclusions Six moderate-intensity interval sessions over seven days, followed by a six-day active recovery period, induce improvements in endurance performance indicators compared to a time-matched regular training period in well-trained cyclists.