REF-045 · Rønnestad et al., 2020 · Scandinavian Journal of Medicine & Science in Sports, Vol. · Paper
Superior performance improvements in elite cyclists following short-interval vs effort-matched long-interval training
Participants
n=18 elite cyclists, VO2max 73 ± 4 mL·min⁻¹·kg⁻¹:
SI group (n=9): short intervals
LI group (n=9): long intervals, effort-matched (by rating of perceived effort)
Protocol (3 weeks, 3 sessions/week = 9 sessions)
Short Intervals (SI): 3 series × 13 × 30-s work / 15-s recovery; 3 min recovery between series (~19.5 min of work per session — arithmetic)
Long Intervals (LI): 4 × 5-min work / 2.5-min recovery (~20 min of work per session — arithmetic)
Effort-matched: LI intensity set by rating of perceived effort to match SI; no differences between groups in total training volume or intensity distribution during the intervention
Tests: 20-min cycling test (mean power), peak aerobic power output, VO2max, power and fractional utilization of VO2max at 4 mmol·L⁻¹ lactate
Key Findings
| Measure | Short (SI) | Long (LI) | Between groups |
|---|---|---|---|
| 20-min mean power | +4.7 ± 4.4% | −1.4 ± 2.2% | P < .01 |
| Peak aerobic power output | +3.7 ± 4.3% | −0.3 ± 2.8% | P < .05 |
| Fractional utilization of VO2max at 4 mmol·L⁻¹ | +3.0 ± 5.8 %-points | −3.5 ± 2.7 %-points | P < .05 |
| Power at 4 mmol·L⁻¹ | +2.0 ± 6.7% | −2.8 ± 3.4% | P < .05 |
| VO2max | — | — | no group difference in change |
SI improved 20-min power (+4.7%) and peak aerobic power (+3.7%) in 3 weeks; LI did not (−1.4% and −0.3%)
The change in VO2max did not differ between groups — the SI advantage showed up in power and lactate-threshold measures, not in VO2max
Effect sizes of the SI advantage were small to large across the variables above
Authors' conclusion: this SI protocol induced superior adaptations compared with this LI protocol in elite cyclists
Mechanisms
Inference, not tested in this paper: the 30/15 format keeps VO2 from falling far during the 15-s recoveries, so more of each session is spent near VO2max than in 5-min efforts at a matched effort; REF-046 measured this directly for the 30/15 format.
Inference, not tested: with effort matched by RPE, the elite riders' 5-min intervals may have sat below the intensity needed for a VO2max stimulus, which would fit the LI group's flat-to-negative changes.
Practical Application
In 18 elite cyclists (VO2max 73 ± 4), 9 sessions over 3 weeks of 3 × 13 × 30/15-s short intervals raised 20-min power +4.7% and peak aerobic power +3.7%, while effort-matched 4 × 5-min long intervals changed them −1.4% and −0.3% (both differences significant); VO2max change did not differ — at this level, 30/15 short intervals are the more productive HIT format for a 3-week block.
Not from this paper; the base's own practice: run the SI session as 3 × 13 × 30/15 s with 3 min between series, work intervals at roughly 120% of FTP; alternate it with a longer-interval session (e.g. the 4 × 8-min format of REF-150) rather than using only one format.
Inference, not tested: below the elite level of this sample the SI format is likely to remain at least as effective, since slower VO2 kinetics in less-trained riders make the 30/15 pattern no less demanding; the study did not test this.
Limitations
n=18, two groups of 9; elite cyclists only; 3 weeks; randomization is not stated in the abstract.
LI intensity was set by RPE, so the comparison is "short vs long at equal effort", not at equal power.
How this entry was checked and changed
Why this level
regraded 2026-09-27 from A: parallel trial, n=18 (9 + 9)
Content correction 2026-09-27
VO2max of the sample: "~65 mL/kg/min" -> 73 ± 4 mL·min⁻¹·kg⁻¹ (abstract).
Added the 4 mmol·L⁻¹ lactate results and the null group difference for VO2max change; "identical total work (kJ)" -> "no difference in training volume and intensity distribution; effort matched by RPE" (abstract wording).
Mechanisms relabelled as inference; "~120% FTP" labelled as the base's own practice; Level A -> B (parallel trial, n=18, randomization not stated).