REF-1791 · Alkhatib, 2026 · Journal of Diabetes Research, · Paper · PubMed · Free full text

The same incremental cycling test at 100 rpm instead of 50 rpm put the maximal-fat-oxidation point (Fatmax) 16 W lower (83.7 vs 99.8 W), with higher oxygen uptake, lactate and carbohydrate use and lower fat use across the submaximal stages (fat use up to 65% of peak power), while maximal fat oxidation itself and peak power did not differ significantly; a randomised crossover of 11 healthy young men not described as cyclists, read in full

Main caveat: Eleven men, single site, single author; no women, no trained cyclists, no patients, although the paper frames its message for people with diabetes.
limited evidenceMeasured on non-athletes to trained athletesRead in full

Alkhatib asked whether pedalling rate during an incremental cycling test changes the fat, carbohydrate and lactate results used to describe someone's metabolism. Eleven healthy young men did the same graded test to exhaustion twice, at 100 and at 50 rpm, in random order.

At every submaximal stage, 100 rpm gave higher oxygen uptake, carbon dioxide output, blood lactate and carbohydrate oxidation and lower fat oxidation than 50 rpm (fat oxidation up to 65% of peak power, carbohydrate and gas exchange up to 80%). Peak power, VO2peak and peak respiratory exchange ratio did not differ; peak lactate was higher at 100 rpm.

Maximal fat oxidation was 0.52 g/min at 100 rpm against 0.58 at 50 rpm (not significant), but it occurred at a lower power (83.7 vs 99.8 W, p = 0.045), and lactate at that point tended to be higher (1.70 vs 1.30 mmol/L, p = 0.061). Expressed as a share of VO2peak, Fatmax moved the other way, higher at 100 rpm (48.9% vs 42.8%).

The author concludes that absolute maximal fat oxidation and lactate are more dependable than the Fatmax intensity when cadence varies, and that Fatmax is better expressed relative to peak power than to VO2peak.

Participants

n = 11 healthy men, university students with varied fitness; age 23.5 ± 3.8 years; 1.8 ± 0.1 m; 76.6 ± 14.3 kg.
Peak values (50 vs 100 rpm): power 295.7 ± 45.6 vs 298.7 ± 55.8 W; VO2peak 4054 ± 561 vs 4131 ± 682 mL/min; peak lactate 9.2 ± 1.9 vs 11.0 ± 2.4 mmol/L (p < 0.05, d = 0.8).
Cycling experience, training volume and sport: not reported. Sample size from a power calculation needing 10.

Protocol

Tests: two incremental tests to exhaustion, 50 and 100 rpm, randomised order within 2 weeks, same time of day (08:00-12:00), 19 ± 0.8 °C; Lode Excalibur Sport ergometer; saddle and bars replicated; familiarisation for those unfamiliar.
Load: start 1 W/kg body mass, +0.5 W/kg every 2 min; exhaustion = cadence not held for more than 15 s, age-predicted maximal heart rate, or a VO2 plateau.
Measures: breath-by-breath gas exchange (Oxycon Pro), last 30 s of each stage; fat oxidation = 1.695 VO2 − 1.701 VCO2 and carbohydrate oxidation = 4.585 VCO2 − 3.226 VO2; earlobe lactate at rest and at the end of each stage; maximal fat oxidation = highest stage value; Fatmax as % of peak power and % of VO2peak.
Before tests: no strenuous exercise or alcohol, habitual diet and activity, no heavy meal within 2 h; adherence confirmed verbally (no food records).
Ethics and funding: approved by the University of Essex ethics committee (approval dated 30 October 2004; when testing took place is not stated); no funding; no conflicts declared.

Key Results

Measure50 rpm100 rpmp, effect size
Maximal fat oxidation, g/min0.58 ± 0.160.52 ± 0.15p = 0.123, d = 0.39
Power at maximal fat oxidation, W99.8 ± 25.883.7 ± 20.3p = 0.045, d = 0.70
Lactate at maximal fat oxidation, mmol/L1.30 ± 0.391.70 ± 0.45p = 0.061, d = 0.90
Fatmax, % of peak power35.3 ± 8.128.4 ± 6.6p = 0.056, d = 0.80
Fatmax, % of VO2peak42.8 ± 7.348.9 ± 8.3p = 0.029, d = 0.90
Submaximal stages, 100 vs 50 rpm: higher VO2 and VCO2 at all stages up to 80% of peak power (p < 0.001; η² 0.682 and 0.697); higher lactate below 80% of peak power (p < 0.001, η² 0.432); higher carbohydrate oxidation up to 80% and lower fat oxidation up to 65% of peak power (both p < 0.001). Stage-by-stage values are in figures only.
Internal inconsistency: the discussion describes the 50-rpm advantage as "16% higher power output at MFO" and later as "8.4% higher"; the table's 99.8 vs 83.7 W is 16.1 W, about 19% (our arithmetic). It also quotes about 10% for maximal fat oxidation and 20% for Fatmax (% of peak power), where the table gives about 12% and about 24% (our arithmetic: 0.58 vs 0.52 g/min; 35.3 vs 28.4%).

Practical Application

The cadence of a lab test moves the result: in 11 healthy young men, Fatmax came 16 W lower at 100 rpm than at 50 rpm, while maximal fat oxidation itself did not differ significantly. When comparing two Fatmax or "fat-burning zone" reports, check that they used the same cadence (and stage length) before reading a change as real.
Higher cadence cost more oxygen and produced more lactate at the same watts in these men, who were not described as cyclists, in line with the base's finding that the most economical cadence sits below the one most riders choose (SYNTH-55). It does not show that a low cadence is better for riding: cadence was imposed, the riders were not described as cyclists, and no performance was measured.
A Fatmax intensity expressed as % of VO2peak can move the opposite way to the same point in watts (higher at 100 rpm as % of VO2peak, lower in W). Inference, not tested here: zones built from a fat-oxidation test transfer best to training at the test's cadence and in the same units.
Agrees with SYNTH-55's testing row (keep cadence consistent across tests; the same watts at a different cadence give a different threshold wattage, REF-202); it adds a fat-oxidation measure to that rule. Fatmax in general sits below the first threshold (REF-1619); this study measured no threshold.

Limitations

Eleven men, single site, single author; no women, no trained cyclists, no patients, although the paper frames its message for people with diabetes.
Two imposed cadences at the extremes of normal riding, not the freely chosen cadence; 2-min stages, which by REF-1619 tend to place Fatmax lower than longer stages do.
Diet and activity before tests were controlled only by instruction and verbal confirmation; no fasting standard beyond no heavy meal for 2 h.
Ethics approval dates from 2004 and the testing date is not stated, so the data may be about two decades old.
Percentages in the discussion do not match the table; no registration; stage values given only in figures.
How this entry was checked and changed
Why this level

a crossover of 11 (the rubric's B row for crossovers under 15); no marker step, because the fat-oxidation and lactate readings are themselves what this testing question is about (rule 3 exception), and oxygen uptake at a set power is an economy outcome