Anne Mette Rustaden

The purpose of this study was to compare the effects of a 1‐week block of moderate‐intensity interval training (MIT) and high‐intensity interval training (HIT) in well‐trained cyclists. Cyclists (♀ = 1; ♂ = 21; maximal oxygen uptake (V̇O _2max ) = 69.5 (6.0) mL·min ⁻¹ ·kg ⁻¹ ) performed both a MIT block involving 6 sessions over 7 days (5–7 × 10–14‐min work intervals, rate of perceived exertion (RPE): 14.5 (0.3)) and a HIT block involving 5 sessions over 6 days (5 × 8.75‐min with multiple short intervals, RPE: 17.1 (0.4)). Post‐testing was performed after 6 days of active recovery, and blocks were separated by 2 months. Testing included 15‐min maximal cycling power (PO _15min ), 10 s maximal sprint power (PO _10sec ), and power output at a blood lactate concentration of 4 mmol·L ⁻¹ (PO _4mmol ). Both the MIT and HIT block improved PO _15min (4.9 (8.7)% and 2.8 (5.3)%, respectively), with no difference between blocks ( p = 0.44). MIT displayed greater improvement than HIT in PO _4mmol (4.5 (4.5)% vs. 2.1 (2.7)%, respectively, p = 0.03, moderate effect size (ES)), while HIT had a moderate ES compared to MIT for improvement in PO _10sec (1.5 (3.7)% vs. −1.5 (7.3)%, respectively), that was not significant ( p = 0.08). No differences were observed between blocks in changes in V̇O _2max ( p = 0.43) or measures of gross efficiency ( p range = 0.43–0.79). However, MIT induced a larger increase in % of V̇O _2max at PO _4mmol compared to HIT (1.2 (3.4)%‐points vs. −0.9 (2.5)%‐points, respectively, p = 0.02, moderate ES). In conclusion, both a MIT block (lower work interval intensity but longer work duration) and a HIT block (higher work interval intensity but shorter work duration) can improve endurance performance determinants and PO _15min with some work intensity‐specific adaptations.