REF-740 · Carmichael RD, Heikkinen DJ, Mullin EM, McCall NR — 2017 · Sports and Exercise Medicine – Open Journal · Paper
A cyclocross race is ridden almost entirely in the high-lactate zone
93.6% of race time above the heart rate of 4 mmol/L, mean HR 171 bpm against a race maximum of 178, post-race lactate 8.3 mmol/L — with no low-intensity time at all
Protocol
Lab: incremental test defining three HR zones — LOW (HR below the 2 mmol/L point), MODERATE (between 2 and 4 mmol/L) and HIGH (above the 4 mmol/L point).
Field: one cyclocross race per rider, HR recorded throughout and classified into the lab zones; capillary lactate immediately post-race.
Key Findings
| Measure | Value |
|---|---|
| Race time HIGH (above the 4 mmol/L HR) | 93.6 ± 6.7% |
| Race time MODERATE (2–4 mmol/L) | 6.1 ± 6.7% |
| Race time LOW (below 2 mmol/L) | 0.4 ± 0.4% |
| Mean race HR | 170.8 ± 10.1 bpm |
| Maximum HR reached in the race | 177.8 ± 8.4 bpm |
| Post-race blood lactate | 8.3 ± 1.1 mmol/L |
Mean race HR sits at ~96% of the maximum the riders reached during the race: heart rate goes up in the first minute and does not come down.
No difference between laps in lap time (p = 0.17) or HR (p = 0.29): the intensity is flat from start to finish, not a fast start followed by a fade.
Lactate of ~8 mmol/L at the finish says the glycolytic contribution stays high to the end — this is not a steady-state event that happens to be short.
Practical Application
Prepare a cyclocross racer for a whole race at or above threshold with no recovery segments (typical elite races last about an hour — not from this paper): the aerobic floor is threshold power and the race sits on it with surges on top. Heart rate is useless for pacing here — it is near maximum from the first minute regardless of power — so pace by feel, by the wheel and by a power meter where the course allows.
With no easy first ten minutes to settle in, the warm-up and the start decide more than in longer off-road events (REF-745 for keeping the legs warm on the grid, REF-279 for the primed fast start).
Read this with REF-741 for the power side of the picture: this study has heart rate and lactate, no power, so the number and size of the surges are not described here.
Limitations
n = 8, one race each, heart rate and lactate only — no power data and no VO₂ during the race.
Zones are anchored to fixed lactate concentrations (2 and 4 mmol/L), not to individual thresholds; the share above 4 mmol/L is robust, the decimals are not.
Small open-access journal; the publisher no longer serves the full text and the figures above are those of the indexed abstract.
How this entry was checked and changed
Content correction 2026-09-27
Race duration "40–60 min" is not in the abstract → removed or labelled as not from this paper. All other figures match the abstract.