REF-1646 · Heil, 2001 · European Journal of Applied Physiology, Vol. · Paper · PubMed

In 21 male competitive cyclists, frontal area grew with body mass to the 0.762 power (95% CI 0.670-0.854), not in proportion to it

Photographs at three trunk and three seat-tube angles (183 images); combined with published wind-tunnel data, the author estimates that drag area scales with mass^0.312, so a heavier rider carries less drag per kilogram

Main caveat: 21 men (74.4 ± 7.2 kg); the exponent may not hold for much lighter or heavier riders, or for women.
limited evidenceMeasured on trained athletesRead from the abstract only

Heil asked how the projected frontal area of competitive male cyclists scales with body mass once bicycle geometry is allowed for statistically. Twenty-one riders (74.4 ± 7.2 kg, 1.82 ± 0.06 m, 23.6 ± 5.1 y) volunteered to be photographed on a modified cycle ergometer at trunk angles of 5°, 15° and 25° for each of three seat-tube angles (70°, 75° and 80°), 183 images in all.

Multiple log-linear regression gave body frontal area (m²) = 0.00433 × STA^0.172 × TA^0.0965 × mass^0.762 (r² = 0.73, SEE 0.017 m²). The mass exponent, 0.762 (95% CI 0.670-0.854), only just took in the theoretical two-thirds and excluded both the +0.55 reported for frontal area and the +0.32 reported for submaximal metabolic power in outdoor cycling.

Analysing wind-tunnel data from the literature, the author found the drag coefficient falling with mass (∝ mass^−0.45); combined with the present result, drag area would scale with mass^+0.312, in line with the +0.32 exponent for submaximal power.

Participants

n = 21 competitive male cyclists, volunteers; 74.4 ± 7.2 kg, 1.82 ± 0.06 m, 23.6 ± 5.1 y.
Not in the abstract: race category, training volume, VO2max.

Protocol

Projected frontal area from photographs of each rider on a modified cycle ergometer.
Positions: trunk angle 5°, 15° and 25° × seat-tube angle 70°, 75° and 80°; 183 images in total.
Analysis: multiple log-linear regression of frontal area on body mass, seat-tube angle (STA) and trunk angle (TA).
Drag coefficient against mass: from the author's analysis of wind-tunnel data published by others, not measured here.
Not in the abstract: handlebar set-up, helmet and clothing, and whether the bicycle's own area was included.

Key Results

QuantityExponent of body massBasis
Body frontal area+0.762 (95% CI 0.670-0.854)measured here; r² = 0.73, SEE 0.017 m²
Drag coefficient−0.45the author's analysis of published wind-tunnel data
Drag area (drag coefficient × frontal area)+0.312combination of the two
Submaximal metabolic power, outdoor cycling+0.32value from the literature, for comparison
Full equation: body frontal area (m²) = 0.00433 × STA^0.172 × TA^0.0965 × mass^0.762.
The confidence interval for the mass exponent barely included two-thirds and excluded 0.55 and 0.32.
Both angle exponents are positive: larger seat-tube and trunk angles went with a larger frontal area (our reading of the signs; how the trunk angle was defined is not in the abstract).

Practical Application

A heavier rider pushes a bigger frontal area, but less of it per kilogram. Frontal area rose with mass^0.762, and the author's combination with wind-tunnel data puts drag area near mass^0.312, matching the literature exponent for submaximal metabolic power in outdoor cycling. Inference, not tested here: this would explain why body mass costs less on flat roads than on climbs, where mass itself must be lifted (REF-1645).
Position changes frontal area independently of body size: trunk and seat-tube angle each entered the equation; how much drag a position saves for a given rider needs measuring, as the base's wind-tunnel and position studies show (REF-794, REF-793).
Inference, not tested here: for a light rider weighing a gain in mass, the extra drag is small relative to the mass added, so on the flat the question is whether the gain brings more power.
Not settled by this design / not from this paper: any rider's actual drag area, wind-tunnel or field drag of these riders, women, and the effect of helmets, clothing or handlebar set-up.

Limitations

21 men (74.4 ± 7.2 kg); the exponent may not hold for much lighter or heavier riders, or for women.
Frontal area from photographs on an ergometer; drag itself was not measured.
The drag-area exponent rests on wind-tunnel data from other studies and on the assumption that the two relations combine.
Handlebar set-up, helmet and clothing are not in the abstract.
Written from the abstract and the PubMed record; full text not read.
How this entry was checked and changed
Why this level

cross-sectional measurement study, n = 21 (under 100); frontal area measured directly; the drag-area exponent is the author's calculation combining this result with others' wind-tunnel data, not measured here

Content correction 2026-11-07
2026-11-07: added from the abstract and the PubMed record; level B (cross-sectional measurement, n = 21).