In junior skiers 5–10-minute intervals totalling 40–45 minutes improved performance more than 2–4-minute intervals totalling 15–20 minutes
The longer reps came with twice the work time
Key Findings
The long-interval group improved 12-km roller-ski time by 6.8 ± 4.0%, 7-km hill run by 4.8 ± 2.6%, VO2max by 3.7 ± 1.6% and oxygen uptake at the ventilatory threshold by 5.8 ± 3.3%, more than the short-interval and control groups in both performance tests.
21 national-level junior cross-country skiers trained for 8 weeks with two sessions a week of 2–4-minute bouts (15–20 minutes in total) or 5–10-minute bouts (40–45 minutes in total), both at the maximal sustainable intensity.
The short-interval group improved VO2max by 3.5 ± 3.2%.
Practical Application
The longer session won because it held twice the work, at the slightly lower intensity that makes that possible — the same pattern as 4 × 8 beating 4 × 4 REF-150.
Read it as "accumulate more quality minutes", not as "long reps beat short reps".
Limitations
Rep length, total work time and intensity all changed together; seven per group; juniors; randomisation not stated in the abstract (abstract only was read).