REF-240 · Lander et al., 2009 · British Journal of Sports Medicine, Vol. · Paper · PubMed

Self-paced exercise is less physically challenging than enforced constant pace exercise of the same intensity: influence of complex central metabolic control

Blimited evidenceMeasured on trained to highly trained athletesWritten before October 2026, being re-checked

Participants

n=9 healthy well-trained males; 5000 m rowing ergometry.

Protocol

Three 5000 m rowing conditions in an individualised order: (1) SubRPE — self-paced at a constant RPE of 15 ("Hard"); (2) SubEXT — enforced constant pace equal to the mean power output of the SubRPE trial; (3) MaxTT — a maximal trial included to disguise the study's purpose and randomise the sequence. Power, VO2, iEMG, core and skin temperature were sampled every 30 s.

Key Results

Parameter	Self-paced (SubRPE)	Enforced constant (SubEXT)	Δ
Mean power, % of MaxTT	83.83 ± 8.88%	83.40 ± 8.84%	matched
Performance time	—	—	no difference
Post-test blood lactate	5.24 ± 2.18 mmol/L	6.19 ± 2.51 mmol/L	higher in constant, p<0.05
Core temperature	38.46 ± 0.23 °C	38.72 ± 0.36 °C	higher in constant, p<0.01
iEMG	lower	higher	p<0.05
HR and VO2 dynamics	—	—	no difference
Stroke-to-stroke power variability	greater	lower	p<0.01

Core finding: at the same mean intensity and the same finishing time, enforced constant pace produced higher lactate, core temperature and muscle activation than self-paced effort; heart rate and oxygen uptake did not differ.

Mechanism

The authors read the greater stroke-to-stroke power variability in the self-paced trial as the athlete dynamically adjusting effort to homeostatic challenges — part of a complex central regulatory process. Locking the output removes that adjustment. Inference, not tested: which specific "micro-adjustments" matter, and whether they would matter at other intensities, was not examined.

Practical Application

n=9 well-trained males, 5000 m rowing at a matched mean power (about 84% of maximal-trial power) and identical finishing time: enforced constant pace raised post-test lactate (6.19 vs 5.24 mmol/L, p<0.05), core temperature (38.72 vs 38.46 °C, p<0.01) and iEMG (p<0.05) compared with self-pacing at a constant RPE of 15; HR and VO2 did not differ — same watts, same time, more physiological strain when the pace is imposed.

Inference, not tested: ERG mode on a trainer enforces constant power and removes the same natural fluctuation; a steady-state ERG session may therefore carry more metabolic and thermal strain than a self-paced ride at the same average watts. Rowing was the model here and only one intensity was tested.

Inference, not tested: for easy or Z2 sessions, where compliance to a target is not the point, self-pacing to feel may be the lower-cost option; for interval targets ERG buys compliance at a possible extra cost.

If an athlete reports an ERG session felt harder than the watts suggest, this study is the reference: imposed constant pace was measurably more stressful than self-paced at the same mean intensity — though note HR did not differ, so the difference will not show up as a higher heart rate.

Limitations

Rowing, not cycling (different muscle recruitment). Small sample (n=9). Single intensity level. Acute measures only — no long-term training adaptation comparison. HR and VO2 did not differ between conditions, so the extra strain was in lactate, temperature and muscle activation, not in the cardiorespiratory markers most athletes watch.

How this entry was checked and changed

Why this level

regraded 2026-09-27 from B+: crossover, n=9

Content correction 2026-09-27

Level B+ -> B (crossover, n=9 per rubric). Sport line "cycling, rowing" -> rowing (the study was rowing ergometry).

Lead Practical bullet was an ERG inference -> now the study's finding with exact abstract values; ERG bullets labelled as inference.

Added the abstract's results the entry omitted: no difference in performance time, HR or VO2; higher core temperature and iEMG in the constant-pace trial; greater stroke-to-stroke variability when self-paced; mean power 83.8% vs 83.4% of the maximal trial.