Intensity Control During Block-Periodized High-Intensity Training: Heart Rate and Lactate Concentration During Three Annual Seasons in World-Class Cross-Country Skiers.

To describe heart rate (HR) and blood lactate (Bla) responses during high-intensity interval training (HIT) in a long-term block-periodized HIT regimen in world-class cross-country (XC) skiers. Data were collected in 14 world-class female XC skiers (aged 25 ± 5 years; body mass, 60.4 ± 6.5 kg; and maximal HR, 194 ± 8 beats · min) throughout three entire seasons. The HR and Bla values were determined at the end of 572 intervals performed during 63 sessions and 17 HIT blocks utilizing different exercise modes: running, running with poles, and skiing (on-snow and roller ski) with classic and skating techniques. The mean HR was 91 ± 3% of HR with a corresponding Bla of 7.3 ± 2.1 mmol · L. The average HR and Bla values were relatively similar across the different exercise modes, except for a lower HR (~90 vs. 92% of HR) for on-snow and roller ski classical skiing and lower Bla values (5.9 vs. 7.0-7.8 mmol · L) for on-snow classical skiing compared to the other modes, both < 0.05. An increase in HR and Bla was observed from interval working periods 1 to 3 (90-92% of HR and 6.5-7.7 mmol · L) and further from 3 to 5 (92-93% of HR and 7.7-9.0 mmol · L), all < 0.05. We describe long-term use of HIT-block periodization among world-class XC skiers who achieved target HR and Bla levels in all six exercise modes employed. According to athletes and coaches, the key to successful blocks was intensity control to allow for high-quality HIT sessions throughout the entire HIT block.