Better economy in field running than on the treadmill: Evidence from high-level distance runners

Abstract

Given the ongoing interest in ways to improve the specificity of testing elite athletes in their natural environment, portable metabolic systems provide an opportunity to assess metabolic demand of exercise in sport-specific settings. Running economy (RE) and maximal oxygen uptake ([Formula: see text]O2max) were compared between track and treadmill (1% inclination) conditions in competitive level European distance runners who were fully habituated to treadmill running (n = 13). All runners performed an exercise test on running track and on treadmill. While [Formula: see text]O2max was similar on the track and on the treadmill (68.5 ± 5.3 vs. 71.4 ± 6.4 ml·kg(-1)·min(-1), p = 0.105, respectively), superior RE was found on the track compared to the treadmill (215.4 ± 12.4 vs. 236.8 ± 18.0 O2 ml·kg(-1)·km(-1), p < 0.001). RE on the track was strongly correlated with RE on the treadmill (r = 0.719, p = 0.006). The present findings indicate that high-level distance runners have significantly better RE but not [Formula: see text]O2max on the track compared to treadmill. This difference may be due to biomechanical adjustments. As RE is strongly correlated between the two conditions, it would be reasonable to assume that interventions affecting RE on the treadmill will also affect RE on the track.

Full text

Biology of Sport, Vol. 32 No2, 2015 155
Running economy and VO
2
max on track and treadmill
INTRODUCTION
Treadmill running is widely used to assess maximal oxygen uptake
(
·
V
O
2
max) and to determine aerobic and anaerobic thresholds by
measuring gas exchange during stepwise incremental tests in distance
runners. Furthermore, running economy (RE) has been traditionally
measured by running on a treadmill in standard laboratory settings.
Although running on a treadmill is not the same as running on a track,
it gives an indication of how economical a runner is and how RE can
change over time [1]. In response to the growing interest in ways to
improve the specicity of physiological testing for elite athletes in
their natural environment, portable metabolic systems which enable
the assessment of the metabolic demand of exercise in a sport-spe-
cic eld environment (e.g. running on a track) have been devel-
oped

[2].
Running on a treadmill is inuenced by the lack of air resistance
that results in lower energy cost and therefore better RE compared
with running on an outdoor track at the same velocity [1,3]. In 1996,
Jones and Doust [3] showed that the reason for the difference between
treadmill and outdoor running is the extra work required to move
through the air rather than mechanical factors. They introduced a
1% incline of the treadmill gradient to increase the energy cost in
Better economy in eld running than on the treadmill: evidence from
high-level distance runners
AUTHORS: Mooses M
1,2
, Tippi B
1
, Mooses K
1,2
, Durussel J
2
, Mäestu J
1
1
Faculty of Sport and Exercise Sciences, University of Tartu, Tartu, Estonia
2
Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University
of Glasgow, Glasgow, United Kingdom
ABSTRACT: Given the ongoing interest in ways to improve the specicity of testing elite athletes in their
natural environment, portable metabolic systems provide an opportunity to assess metabolic demand of exercise
in sport-specic settings. Running economy (RE) and maximal oxygen uptake (
·
V
O
2
max) were compared between
track and treadmill (1% inclination) conditions in competitive level European distance runners who were fully
habituated to treadmill running (n = 13). All runners performed an exercise test on running track and on treadmill.
While
·
VO
2
max was similar on the track and on the treadmill (68.5 ± 5.3 vs. 71.4 ± 6.4 ml·kg
-1
·min
-1
, p = 0.105,
respectively), superior RE was found on the track compared to the treadmill (215.4 ± 12.4 vs. 236.8 ±
18.0 O
2
ml·kg
-1
·km
-1
, p < 0.001). RE on the track was strongly correlated with RE on the treadmill (r = 0.719,
p = 0.006). The present ndings indicate that high-level distance runners have signicantly better RE but
not
·
V
O
2
max on the track compared to treadmill. This difference may be due to biomechanical adjustments.
As RE is strongly correlated between the two conditions, it would be reasonable to assume that interventions
affecting RE on the treadmill will also affect RE on the track.
CITATION:
Mooses M, Tippi B, Mooses K, Durussel J, Mäestu J. Better economy in eld running than on the
treadmill: evidence from high-level distance runners Biol Sport. 2015;32(2):155–159.
Received: 2014-04-12; Reviewed: 2014-08-24; Re-submitted: 2014-09-03; Accepted: 2014-11-30; Published: 2015-03-15.
compensation. Other possible reasons for differences between the
two running conditions, such as (i) the runner may gain energy from
the motor-driven treadmill belt and (ii) biomechanical changes in
running technique due to different surfaces or to the instability caused
by visual cues from static rather than moving surroundings, have
been discussed [3,4].
The habituation of running on the treadmill can also signicantly
inuence differences in RE between track and treadmill conditions[5],
except for athletes who are fully habituated to treadmill running [3],
as in the present study. Furthermore, from our personal contact with
recreational up to international level runners, we have observed
lower values on the rating of perceived exertion (RPE) scale in track
running compared to treadmill running at the same velocity. It has
also been shown that higher velocities on the track compared to the
treadmill were attained when athletes were asked to maintain the
same relative effort (RPE score) during both running conditions [6].
The aim of the present study was to compare RE and
·
V
O
2
max values
between running on a treadmill and on a track in high competitive
level habitual treadmill runners using portable metabolic systems. It
was hypothesised that (i) at the speed of 16 km∙h
-1
high-level distance
Original Paper
Biol. Sport 2015;32:155-159
DOI:10.5604/20831862.1144418
Key words:
treadmill test
running track
running economy
maximal oxygen uptake
running performance
Corresponding author:
Martin Mooses
Faculty of Sport and Exercise
Sciences, University of Tartu,
Tartu, Estonia
E-mail: Martin.Mooses@ut.ee

156
Mooses M. et al.
runners have better RE on the track compared to the treadmill;
(ii)
·
V
O
2
max values on the track are not different from those on the
treadmill.
MATERIALS AND METHODS
Subjects. A total of 13 European distance runners were recruited for
this study. The best performance of the athletes was established
using the International Association of Athletics Federations (IAAF)
Scoring Tables [7,8,9]. These tables assign a denite score to each
performance, enabling comparison between different events [8].
Study procedures and protocols were approved by the Ethics Com-
mittee of the University of Tartu (Tartu, Estonia) and conformed to
the Declaration of Helsinki. All testing procedures and related risks
were described before providing written informed consent to par-
ticipate in the study.
Study design
A cross-sectional analysis of 13 distance runners was performed. On
the rst visit to the laboratory, the main anthropometric parameters
were measured. Runners performed the rst test on an outdoor track
and the second one on a treadmill (see specic protocols below).
Track and treadmill tests were separated by at least 48 h. Athletes
were requested to maintain their usual dietary intake and to refrain
from alcohol throughout the study period [10]. They were also asked
to abstain from hard training and/or competition for at least 24 h
before testing. Athletes wore the same shoes and running clothes for
both of the tests.
Exercise testing
A maximal running test on a 400 m outdoor track was performed.
The athlete ran next to a cyclist who set a speed for each stage using
a speedometer (Cateye Velo 05, Osaka, Japan). The bicycle speed-
ometer was calibrated according to the instructions of the manufac-
turer and checked using the treadmill (HP Cosmos Quasar, Nussdorf-
Traunstein, Germany) speed and 12-channel GPS (Garmin eTrex,
Garmin Ltd, Kansas, USA). Two additional recording GPS devices
(Polar RS800cx G5, Polar Electro Oy, Kempele, Finland and Garmin
Forerunner 405 Garmin Ltd, Kansas, USA) were attached to the
runner to calculate the average running speed of each running stage.
Before commencement of the exercise test, each athlete remained
stationary on the track for three minutes and pre-test cardio-respira-
tory data were collected. Initial running speed was set at 8 km∙h
-1
and then increased by 2 km∙h
-1
every three minutes up to 20 km∙h
-1
.
The speed at 20 and 22 km∙h
-1
was maintained for two minutes.
From that point on, the speed was increased by 1 km∙h
-1
after
every two minutes until voluntary exhaustion.
Following familiarisation with the treadmill, participants performed
an incremental running test on a motorized treadmill (HP Cosmos
Quasar, Nussdorf-Traunstein, Germany) until voluntary exhaustion.
Before commencement of the exercise test, each athlete remained
stationary on the treadmill for three minutes and cardio-respiratory
data were collected. The initial running speed was set at 8 km∙h
-1
with a gradient of 1% [3,11] and then increased by 2km∙h
-1
every
three minutes until 14 km∙h
-1
. The speed of the 16 km∙h
-1
stage on
the treadmill was replaced by the speed measured during the track
test calculated from the average of the values of the two GPS de-
vices rounded to the nearest decimal point (i.e. if the average speed
on the track was 15.7 km∙h
-1
, then the treadmill speed was set to
15.7 km∙h
-1
instead of 16 km∙h
-1
). Following the 3 min 17 km∙h
-1
stage, the speed remained constant and elevation increased 1%
after every one minute until voluntary exhaustion [12].
During track and treadmill tests, expired gases and heart rate(HR)
were measured using the same Metamax 3B device (Cortex Biophysik
GmbH, Leipzig, Germany), which was calibrated before each test
according to instructions of the manufacturer.
·
V
O
2max
was dened as
the highest average
·
V
O
2
during a 30 s period and a failure to increase
·
V
O
2
further despite an increase in work rate [13]. RE was measured
during the last two minutes of the speed during
the 16 km∙h
-1
stage.
RE was expressed as oxygen cost (O
2
ml∙kg
-1
∙km
-1
) and was calcu-
lated as follows:
,
where
·
V
O
2
is steady-state oxygen uptake (ml∙kg
-1
∙min
-1
) and v is
running velocity (m∙min
-1
) [14]. Steady state was dened as an in-
crease of less than 100 ml O
2
over the nal two minutes of the re-
spective running stage [15]. During the treadmill test, ambient tem-
perature and relative humidity in the laboratory were regulated with
an air conditioning device to correspond to conditions on the outdoor
track.
Statistical analysis
Treadmill and track conditions within the group were compared with
the paired t-test or Wilcoxon signed-rank test. Linear relationships
between the two conditions were assessed with Pearson’s correlation
coefcient. Calculations were performed using IBM SPSS v.20 soft-
ware for Windows (SPSS Inc, Chicago, IL, USA). Effect size was
calculated with G*Power v.3.1.7 (University of Düsseldorf, Düsseldorf,
Germany). Cohen’s d [16] was calculated to indicate effect size and
practical meaningfulness. The effect size was evaluated using Lipsey’s
criteria and considered medium when d was between 0.45 and 0.89,
and large when d was higher than 0.90 [17]. The level of signicance
was set at p < 0.05.
RESULTS
The main characteristics of the runners are presented in table 1.
While
·
V
O
2max
was similar between track and treadmill conditions
(68.5 ± 5.3 vs. 71.4 ± 6.4 ml∙kg
-1
∙min
-1
, p = 0.105, d = 0.49
respectively), superior RE was found on the track compared to the
treadmill (215.4 ± 12.4 vs. 236.8 ± 18.0 O
2
ml∙kg
-1
∙km
-1
,
p < 0.001, d = 1.72) (Figure 1). In other words, runners were 8.8%
more economical on the track than on the treadmill. RE on the track
was strongly correlated with RE on the treadmill (r = 0.719,

Biology of Sport, Vol. 32 No2, 2015
157
Running economy and VO
2
max on track and treadmill
p = 0.006). Runners presented signicantly lower VE
(102.3 ±
16.6 vs. 115.5 ± 19.2 l∙min
-1
, p < 0.001, d = 2.19) but not HR
(169 ± 10 vs. 171 ± 8 bpm, p = 0.269, d = 0.32) on the track
compared with the treadmill during the 16 km∙h
-1
stage. VE on the
treadmill was 11.2% higher than that on the track.
DISCUSSION
The novel nding of the present study was that high-level distance
runners have signicantly better RE on the track compared to the
treadmill with the widely used 1% inclination. The treadmill is not
only a popular research instrument in studying human locomotion
and exercise capacity, but has also been used for training and con-
ditioning purposes for a long time [18,19]. At the same time, as
there is a growing interest in the use of treadmill running as part of
regular training for high-level distance runners, it has been debated
whether the changes observed in laboratory-based
·
V
O
2max
and RE
tests would automatically translate into actual changes in running
performance in the eld. Coaches are looking for reliable sport-spe-
cic tests, which reect the real status of their athletes. Therefore,
assessment of the differences between treadmill and track running
using a modern, portable metabolic system would give the necessary
insight before generalizing the results of treadmill studies to outdoor
running. This is the rst study to use a modern, portable metabolic
measurement system to compare track and treadmill running in high
competitive level distance runners in their everyday training condi-
tions.
Several studies have concluded that air resistance is the only
cause of the observed differences between track and treadmill loco-
motion [3,4]. However, Pugh [20] designed a wind screen to allevi-
ate air resistance and still observed higher energy cost in track run-
ning than on the treadmill. This indicated that other factors might
be responsible for the differences in RE between the two running
conditions, such as biomechanical adjustments [19]. Running in a
more “natural” environment on a track compared to a more “articial”
environment on a treadmill led to a better RE of 8.8%. This better
RE may be partly explained by the signicantly lower VE on the track
compared to the treadmill. As ventilatory work accounts for 7–8%
of the overall energy cost of exercise [21], a decrease in VE leads to
a decrease in
·
V
O
2
(i.e. better RE) [22,23,24]. The technique of run-
ning on a treadmill is different to that running over ground where the
hamstrings are used to a greater extent to produce propulsive forc-
es[1]. The slightly different muscle recruitment patterns on the
treadmill can then lead to an increase in ventilation, especially at
submaximal stages on a treadmill [25]. The ndings of the present
study are in agreement with the signicantly higher energy expendi-
ture observed during treadmill running at submaximal stages com-
pared to track running [25]. On the other hand, contradictory results
showing no signicant differences or impairment in RE between track
and treadmill conditions have previously been reported [3,20,26,27].
However, these studies were conducted with the Douglas bag meth-
od for eld measurements, which likely interfered with running move-
ments and thus limited the submaximal values [25]. While it seems
that there is a consensus that biomechanical adjustments occur
between treadmill and track conditions and can consequently alter
Europeans (N = 13)
Age (years) 25.4 ± 4.4
Mass (kg) 69.0 ± 5.9
Height (m) 1.81 ± 0.05
BMI (kg∙m
-2
) 21.0 ± 1.2
IAAF (p) 786 ± 111
Regular training (years) 8.3 ± 5.3
Note: BMI – body mass index; IAAF (p) – International Amateur Athletic
Federation scoring table points.
TABLE 1.
Characteristics of participants (mean ± SD).
FIG.
1.
Mean (thick lines with triangles) and individual results for running economy (A), ventilation (B) and heart rate (C).
Note: * – signicant difference between track and treadmill.

158
Mooses M. et al.
energy expenditure, the conclusion on whether these biomechanical
adjustments are advantageous on the treadmill or on the track may
differ due to the characteristics of the group studied (e.g. sprinters
vs. endurance runners) [19]. The slightly higher RE values at the
speed of 16 km∙h
-1
reported in the present study compared to previ-
ously published data [11,28,29,30] are most likely due to the por-
table device MetaMax 3B used to measure
·
V
O
2
. However, and im-
portantly, although the MetaMax 3B has been shown to overestimate
·
V
O
2
by up to 10% when compared to the primary criterion Douglas
bag method [2,31] and secondary criterion Jaeger Oxycon Pro sys-
tem[31], it has excellent reproducibility, with a typical error of 2–3%
for
·
V
O
2
,
·
VC
O
2
and VE
[2].
Using a modern portable metabolic system, the present study also
conrmed that identical
·
V
O
2max
results are obtained during tests
conducted in both treadmill and track running conditions. This indi-
cates that
·
V
O
2max
in running is independent of the execution of the
test whether on the track or on the treadmill, if an equal amount of
effort is spent [25]. Finally, the practical implications of the ndings
of the present study give condence for running coaches that training
methods resulting in an improvement in RE and
·
V
O
2max
in treadmill
tests would lead to a similar improvement in running on the track in
high-level distance runners. However, the 1% inclination on the tread-
mill is likely to be too high to reproduce similar efforts to those in
track running.
CONCLUSIONS
In the present study we demonstrated in high-level distance runners
that (i) RE is signicantly better on the track compared to the tread-
mill, and (ii)
·
V
O
2max
values do not depend on whether the test was
conducted on a treadmill or on a track. Finally, as RE was strongly
correlated between conditions, it is reasonable to assume that inter-
ventions affecting RE on the treadmill will also affect RE on the track.
Acknowledgements
The authors wish to specially thank the subjects for their participation
and cooperation. We would also like to thank the Prof. Toivo Jürimäe,
Prof. Jaak Jürimäe, Prof. Priit Kaasik, Dr. Priit Purge, Dr. Evelin Lätt
and Dr. Helena Liiv who helped with some aspects of data collection,
technical assistance and logistic support during the study. The study
was funded by grant from the Estonian Ministry of Education and
Science Institutional Grant TKKSP 14058I.
Conict of interests: the authors declared no conict of interests
regarding the publication of this manuscript.
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