Author(s): SINDRE MØLMEN, K., ODDEN, I., SØRENSEN, M., RØNNESTAD, B., Institution: INLAND NORWAY UNIVERSITY OF APPLIED SCIENCES, Country: NORWAY, Abstract-ID: 712

INTRODUCTION:
To organize training into shorter periods of time with specific training focuses has become increasingly common for endurance athletes in recent years. Particularly, organizing high-intensity interval training sessions in microcycles has been well-studied and found to improve endurance performance-related variables [1]. There is, however, little evidence on how efficient similar type of training strategy is when performing moderate-intensity interval training (MIT) in well-trained endurance athletes. Here, we compare the physiological effects of a seven-day MIT microcycle with a time-matched period with usual training (CON) in well-trained cyclists.
METHODS:
Using a randomized crossover design, 30 male cyclists (maximal oxygen consumption (VO2max),70.5 (4.6) mL/min/kg) performed both a MIT microcycle and CON training. Sixteen and 14 of them started with the MIT microcycle and CON training, respectively. The MIT microcycle consisted of six interval sessions distributed over seven days. In consecutive days, except for a rest day on the 4th day, they performed interval sessions with 7x10 min, 6x12 min, 5x14 min, 7x10 min, 5x14 min, and 6x12 min work periods, with the aim of hitting 14-15 on the Borg 6-20 rating of perceived exertion (RPE) during the work intervals (equivalent to a perceived exertion of “somewhat hard” to “hard”). A six-day taper period was carried out before physiological testing. The efficacy of the MIT and CON training was measured as changes in 15-min maximal average power output (PO15min), power output at 4 mmol/L [blood lactate] (PO4mmol), mean power output achieved during the last minute of an incremental test (pVO2max), and VO2max.
RESULTS:
Average RPE during work intervals in the MIT microcycle was 14.4 (0.3), which corresponded to 66.4 (4.8) % of pVO2max, 85.3 (3.3) % of maximal heart rate, and 2.8 (1.1) mmol/L [blood lactate]. The MIT microcycle led to significantly larger improvements than CON on PO4mmol (4.0 (4.4) % vs. -1.3 (3.7) %, respectively; p<0.001) and pVO2max (2.5 (4.5) % vs. -0.7 (3.9) %, respectively; p=0.007), while changes in PO15min were not statistically different between interventions (3.9 (8.3) % vs. 0.2 (6.8) %, respectively; p=0.138). VO2max tended to increase more following MIT than CON (2.0 (3.9) % vs 0.0 (3.5) %, respectively; p=0.055).
CONCLUSION:
Six MIT sessions distributed over seven days followed by a taper period induced larger improvements in measures of endurance performance than a time-matched period of usual training in well-trained cyclists.

Reference: 1. Mølmen KS, Øfsteng SJ, Rønnestad BR. Block periodization of endurance training - a systematic review and meta-analysis. Open access J Sport Med. 2019;10:145–60.