Does running surface affect your pace?
Yes. Grass costs roughly 5% more oxygen than asphalt at matched speed, and trail more again — though the trail and track figures in most models are estimates rather than measurements.
The measured comparison with the best support is grass against asphalt: Sassi and colleagues found a cost of running about 5% higher on natural grass at matched speeds. That is a meaningful penalty and explains why a cross-country pace feels harder than the same number on the road.
Track and trail are murkier, and this site is explicit about it. There is no published certified-track-versus-road oxygen-cost comparison at matched speed; the small advantage often assumed for track comes from surface-compliance work using platforms far more compliant than any real track. The trail figure is bracketed by studies of uneven treadmill surfaces at one end and rough paths at the other, a range spanning roughly 5% to 18%.
Practically, the implication is to stop comparing paces across surfaces. A tempo run on grass at the same effort will be slower on the watch than the same session on asphalt, and treating that as a fitness signal is a mistake. Effort-based pacing, or grade-and-surface adjustment, is the honest way to compare.
The counterweight is that softer surfaces reduce impact loading, which has value for injury management even at a metabolic cost. Running everything on asphalt because it is faster is optimising the wrong variable.
Key numbers
| Grass | +5% | measured, vs asphalt |
|---|---|---|
| Trail | +10% assumed | bracketed by +5% to +18% studies |
| Track | −2% assumed | no direct measurement exists |
Work it out for yourself
Running economy calculator — Compare surfaces, shoes and gradients on the same cost-of-running model.
Frequently asked questions
Is it harder to run on sand or grass?
Sand, by a wide margin — dry soft sand can raise the energy cost dramatically because so much of each push-off is absorbed by the surface deforming. Grass sits much closer to asphalt, at roughly a 5% penalty.
Should I do my long runs on trails?
Trails reduce impact loading and add terrain variety, both of which have value. They also make pace comparisons meaningless and, if your race is on the road, they miss some of the specific loading you are preparing for. A mix suits most marathon builds.
Sources
- Sassi et al. (2011). Effects of gradient and speed on freely chosen cadence. Journal of Strength and Conditioning Research.
- Voloshina & Ferris (2015). Biomechanics and energetics of running on uneven terrain. Journal of Experimental Biology.
Related explainers
Glossary: Cr (Cost of Running)