1% Grade on Treadmill = Outdoor Running
Some chatter on the board about this. Thought I would post some research. Having run quite a bit on the road and treadmill, this fits with what I have anecdotally found. See study below:
J Sports Sci. 1996 Aug;14(4):321-7.
A 1% treadmill grade most accurately reflects the energetic cost of outdoor
Jones AM, Doust JH.
Chelsea School Research Centre, University of Brighton, Eastbourne, UK.
When running indoors on a treadmill, the lack of air resistance results in a
lower energy cost compared with running outdoors at the same velocity. A slight
incline of the treadmill gradient can be used to increase the energy cost in
compensation. The aim of this study was to determine the treadmill gradient that
most accurately reflects the energy cost of outdoor running. Nine trained male
runners, thoroughly habituated to treadmill running, ran for 6 min at six
different velocities (2.92, 3.33, 3.75, 4.17, 4.58 and 5.0 m s-1) with 6 min
recovery between runs. This routine was repeated six times, five times on a
treadmill set at different grades (0%, 0%, 1%, 2%, 3%) and once outdoors along a
level road. Duplicate collections of expired air were taken during the final 2
min of each run to determine oxygen consumption. The repeatability of the
methodology was confirmed by high correlations (r = 0.99) and non-significant
differences between the duplicate expired air collections and between the
repeated runs at 0% grade. The relationship between oxygen uptake (VO2) and
velocity for each grade was highly linear (r > 0.99). At the two lowest
velocities, VO2 during road running was not significantly different from
treadmill running at 0% or 1% grade, but was significantly less than 2% and 3%
grade. For 3.75 m s-1, the VO2 during road running was significantly different
from treadmill running at 0%, 2% and 3% grades but not from 1% grade. For 4.17
and 4.58 m s-1, the VO2 during road running was not significantly different from
that at 1% or 2% grade but was significantly greater than 0% grade and
significantly less than 3% grade. At 5.0 m s-1, the VO2 for road running fell
between the VO2 value for 1% and 2% grade treadmill running but was not
significantly different from any of the treadmill grade conditions. This study
demonstrates equality of the energetic cost of treadmill and outdoor running
with the use of a 1% treadmill grade over a duration of approximately 5 min and
at velocities between 2.92 and 5.0 m s-1.