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Abstract and Figures

Cycling can be performed on the road or indoors on stationary ergometers. The purpose of this study was to investigate differences in cycling efficiency, muscle activity and pedal forces during cycling on a stationary turbo trainer compared with a treadmill. 19 male cyclists cycled on a stationary turbo trainer and on a treadmill at 150, 200 and 250 W. Cycling efficiency was determined using the Douglas bags, muscle activity patterns were determined using surface electromyography and pedal forces were recorded with instrumented pedals. Treadmill cycling induced a larger muscular contribution from Gastrocnemius Lateralis, Biceps Femoris and Gluteus Maximus of respectively 14%, 19% and 10% compared with turbo trainer cycling (p<0.05). Conversely, Turbo trainer cycling induced larger muscular contribution from Vastus Lateralis, Rectus Femoris and Tibialis Anterior of respectively 7%, 17% and 14% compared with treadmill cycling (p<0.05). The alterations in muscle activity resulted in a better distribution of power during the pedal revolution, as determined by an increased Dead Centre size (p<0.05). Despite the alterations in muscle activity and pedalling technique, no difference in efficiency between treadmill (18.8±0.7%) and turbo trainer (18.5±0.6%) cycling was observed. These results suggest that cycling technique and type of ergometer can be altered without affecting cycling efficiency.
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520 Training & Testing
Arkesteijn M et al. The E ect of Turbo Int J Sports Med 2013; 34: 520–525
accepted after revision
September 04 , 2012
Bibliography
DOI http://dx.doi.org/
10.1055/s-0032-1327658
Published online:
November 23, 2012
Int J Sports Med 2013; 34:
520–525 © Georg Thieme
Verlag KG Stuttgart · New York
ISSN 0172-4622
Correspondence
Dr. James Hopker
School of Sport and Exercise
Sciences
University of Kent
Chatham Maritime
Medway
United Kingdom
me4 4ag
Tel.: + 44/163/4888 814
Fax: + 44/163/4888 809
j.g.hopker@kent.ac.uk
Key words
ergometry
treadmill
electromyography
pedal forces
muscle activity
The E ect of Turbo Trainer Cycling on Pedalling
Technique and Cycling E ciency
eter, Stockholm, Sweden) with road cycling. They
[ 3 ] found that the stationary ergometer caused
an altered distribution of power during the pedal
revolution. In particular, this occurred in the
region of the dead centres (i. e., where the cranks
are positioned vertically), where the power pro-
duced by the cyclists is at its minimum. Further-
more, a comparison between an electromagnetic
turbo trainer and treadmill cycling has shown
that the overall muscle activity is higher when
cycling on the turbo trainer [ 10 ] . This would sug-
gest an increase in muscular work, which could
consequently increase energy expenditure with-
out changes in external work [ 20 , 21 ] . Further-
more, it has recently been shown that muscle
activity patterns are related to mechanical e -
ciency [ 5 ] , and that this is altered with changing
cycling constraints (e. g. gradient, power output)
[ 4 ] . This suggests that cycling e ciency (the ratio
between external work and energy expenditure)
can be decreased when cycling on a turbo trainer
due to changes in muscle coordination.
Leirdal and Ettema [ 22 , 23 ] have presented con-
icting results in 2 studies that investigated the
Introduction
Training is a critical aspect of improving per-
formance during competitive events [ 19 ] . In par-
ticular, training speci city is frequently advo cated
to optimize training adaptation [ 26 ] . Due to the
large volume of training required to achieve an
elite level [ 19 ] , many cyclists continue to train
during the o season, i. e., the winter months.
During this time, outdoor cycling may be limited
by inclement road and weather conditions. Using
an indoor turbo trainer provides an alternative
training solution in these situations. A turbo
trainer applies increased rolling resistance to
replace the absent air resistance experienced
during road cycling, while maintaining a station-
ary position. This allows cyclists to perform
structured indoor training, to complement or
replace a portion of their outdoor training.
Comparisons between stationary and road cycling
(using a freely moving bicycle) suggest that a
turbo trainer changes cycling technique. Ber-
tucci, Grappe and Grosslambert [ 3 ] compared
cycling on a stationary bicycle (Monark ergom-
Authors M. Arkesteijn
1
, J. Hopker
2
, S. A. Jobson
3
, L. Pass eld
4
A liations
1
Department of Sport and Exercise Sciences, Aberystwyth University, Ceredigion, Wales, United Kingdom
2
School of Sport and Exercise Sciences, University of Kent, Medway, United Kingdom
3
Department of Sports Studies, University of Winchester, Winchester, United Kingdom
4
School of Sport and Exercise Sciences, University of Kent, Chatham Maritime, United Kingdom
Abstract
Cycling can be performed on the road or indoors
on stationary ergometers. The purpose of this
study was to investigate di erences in cycling
e ciency, muscle activity and pedal forces dur-
ing cycling on a stationary turbo trainer com-
pared with a treadmill. 19 male cyclists cycled on
a stationary turbo trainer and on a treadmill at
150, 200 and 250 W. Cycling e ciency was deter-
mined using the Douglas bags, muscle activity
patterns were determined using surface electro-
myography and pedal forces were recorded with
instrumented pedals. Treadmill cycling induced
a larger muscular contribution from Gastroc-
nemius Lateralis, Biceps Femoris and Gluteus
Maximus of respectively 14 %, 19 % and 10 %
compared with turbo trainer cycling ( p < 0.05).
Conversely, Turbo trainer cycling induced larger
muscular contribution from Vastus Lateralis,
Rectus Femoris and Tibialis Anterior of respec-
tively 7 %, 17 % and 14 % compared with tread-
mill cycling ( p < 0.05). The alterations in muscle
activity resulted in a better distribution of power
during the pedal revolution, as determined by an
increased Dead Centre size ( p < 0.05). Despite the
alterations in muscle activity and pedalling tech-
nique, no di erence in e ciency between tread-
mill (18.8 ± 0.7 %) and turbo trainer (18.5 ± 0.6 %)
cycling was observed. These results suggest that
cycling technique and type of ergometer can be
altered without a ecting cycling e ciency.
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521Training & Testing
Arkesteijn M et al. The E ect of Turbo Int J Sports Med 2013; 34: 520–525
relation between pedalling technique and cycling e ciency.
Pedalling technique was quanti ed by a novel parameter that
described the distribution of power during the pedal revolution.
The minimum power outputs during the pedal revolution (i. e.,
the dead centres) were expressed relative to the overall power
output and described as ‘dead centre size’ (DC) [ 21 ] . Leirdal and
Ettema [ 22 ] showed a positive correlation between e ciency
and DC and thus pedalling technique. This study was performed
on a normal road bicycle positioned on an electromagnetic roller
(Taxc, I-magic, The Netherlands). However, when a stationary
ergometer with a computer-controlled electromagnetic brake
mechanism (Velotron, Racermate Inc., Washington) was
employed in a later study [ 23 ] , the relation between e ciency
and DC was not con rmed. This suggests that e ciency is in u-
enced by the kind of ergometer employed, an e ect that might
be explained by alterations in cycling technique [ 10 ] . Alterna-
tively, it has been shown that torso stabilisation increases e -
ciency [ 24 ] . A stationary bicycle does not require active
stabilisation of the bicycle and the di erent ergometers
employed could provide an alternative explanation for con ict-
ing ndings of Leirdal and Ettema [ 22 , 23 ] . However, no previous
research has directly compared the combined e ect of di erent
types of ergometers with measures of cycling technique and
exercise e ciency.
The aim of the present study was to determine whether cycling
e ciency and pedalling technique di er between stationary
turbo trainer and treadmill cycling. Participants cycled on a
commercially available turbo trainer and on a treadmill to repli-
cate road cycling within a controlled environment. It was
hypothesized that DC is increased during treadmill cycling com-
pared with turbo trainer cycling, which would be re ected in
muscle activity patterns, but not cycling e ciency. A secondary
aim was to identify whether or not DC is related to cycling e -
ciency and whether or not DC is a ected by work rate.
Methods
19 male cyclists (age: 36 ± 10 years, height: 181 ± 6 cm, mass:
77.4 ± 8.4 kg, V
˙
O
2max
: 4.6 ± 0.5 L · min
1
, Maximal Aerobic Power:
353 ± 45 W) from local cycling clubs participated in the study. All
participants trained for 6 h or more per week and were free of
medical issues that could restrict lower limb movement. All par-
ticipants provided written informed consent to participate in
the study that was approved by the institution’s ethics commit-
tee, in accordance with the Declaration of Helsinki [ 14 ] .
Experimental design
Participants visited the laboratory on 2 separate occasions. On
their rst visit, participants were familiarised with the protocol
before completing a ramp test to determine V
˙
O
2max
and maximal
aerobic power (MAP). During familiarisation participants cycled
on standard road bicycle (Specialized Secteur, Specialized, CA,
USA) on a treadmill (Saturn, 200 × 250 cm, HP Cosmos, Nussdorf-
Traunstein, Germany) at a power output below 140 W, using
their preferred cadence until they were comfortable riding on
the treadmill. Subsequently, they completed 6 min of cycling on
a computer controlled electromagnetically braked turbo trainer
(Tacx Fortius, Wassenaar, The Netherlands). The turbo trainer
was positioned on a platform that was placed over the treadmill
belt, to minimize movement of equipment due to the presence
of cables attached to the participant. On their second visit, par-
ticipants cycled on the treadmill and turbo trainer, completing 6
conditions at 3 work rates (150, 200 and 250 W) on both the
treadmill (TR) and turbo trainer (TT) at 90 rev · min
1
. Work rates
were administered in a random, counterbalanced design in
order to minimise possible fatigue e ects due to the length of
testing [ 27 ] . Thus, TR and TT were performed consecutively at
the same work rate. 10 participants started with TR and 9 par-
ticipants started with TT. All participants switched after the
rst, third and fth condition, in order to negate a potential
e ect of condition order. Cycling e ciency, muscle activity pat-
terns and pedal forces were recorded during the second visit for
subsequent analysis. A 10-min warm-up at a work rate of < 150 W
at 90 rev · min
1
preceded the experimental conditions. Prior to
each test, participants were instructed to refrain from exercise
and alcohol for 24 h and from ca eine intake for 4 h.
Cycling tests
An incremental ramp test was performed on a cycle ergometer
(Schöberer Rad Messtechnik, Welldorf, Germany). Prior to the
test, participants completed a 10-min warm-up at 100 W using a
self-selected cadence. The test started at a power output of
100 W for 1 min to allow the participant to reach his preferred
cadence. After the rst minute, the power output was increased
to 150 W. Work rate increased by 20 W · min
1
until volitional
exhaustion. V
˙
O
2max
was calculated as the highest minute average
of V
˙
O
2
recorded during the test using a breath-by-breath gas
analysis system (Metalyzer 3b, Cortex Biophysik, Germany).
MAP was calculated as the highest averaged 1-min power out-
put.
Gross e ciency was measured whilst participants cycled using
a standard road bicycle on either the treadmill or the turbo
trainer. The bicycle was tted with an adjustable stem (Look
ergo stem, Look, Nevers, France) and an adjustable seat post
(I-beam, SDG Components, CA, USA). The participants’ own bicy-
cle geometry was measured and replicated using a bicycle scan-
ner (Radlabor, Freiburg, Germany) and participants used their
own cleats and pedals. Tyres were in ated to 700 kPa prior to
each visit. For safety considerations, cycling speed was kept con-
stant at 17.7 km · h
1
for both TR and TT and thus gearing was
kept constant across conditions. For the TR conditions resistance
was provided by a weighted pulley system [ 8 ] , whereby a basket
containing weights is suspended from the rear of the saddle. The
weights were increased in order to induce 150, 200 and 250 W at
the same cycling speed. Participants rested passively for 3 min
between each condition.
Measurements
Each condition commenced with a 1-min period to allow the
treadmill speed and cadence to reach required values. The par-
ticipant cycled for a further 5-min period in the seated position.
As power output during TT could decrease due to internal
changes in the turbo trainer while cycling [ 28 ] , power output
was monitored continuously using a 30 s average power output
(Edge 500, Garmin, USA), to maintain the target power output.
Muscle activity patterns were recorded using surface electromy-
ography (Bagnoli-8, Delsys, Boston, MA, USA). Pedal forces tan-
gential and radial to the bicycle crank were captured using
instrumented devices that were placed on the right and left
cranks (Powerforce, Radlabor, Freiburg, Germany) [ 31 ] . Both
electromyography and pedal forces recordings were captured at
1 000 Hz and were synchronized using a square wave pulse gen-
erated when the bicycle crank passed the trigger located on the
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522 Training & Testing
Arkesteijn M et al. The E ect of Turbo Int J Sports Med 2013; 34: 520–525
bicycle. These signals were then digitized using Imago software
(Radlabor, Germany). Power output was continuously recorded
at 1 Hz via a rear wheel power measurement device (PowerTap
Elite + , Saris, Madison, USA), which has been shown to be valid
and reliable [ 2 ] , allowing the same device to be used during both
treadmill and turbo trainer cycling. Expired air was collected in
Douglas bags during the nal minute of each 5-min period [ 16 ] .
Participants rested for 3 min between conditions, during which
Douglas bag contents were analysed for oxygen consumption
and carbon dioxide production using a high precision o ine gas
analyser (Servo ex MiniMP, Servomex, UK) and dry gas volume
meter (Harvard Apparatus Ltd., Edenbridge, UK) [ 16 ] .
EMG recordings were made on the right lower leg for the Tibialis
anterior (TA), Soleus (SOL), Gastrocnemius medialis (GM), Gas-
trocnemius lateralis (GL), Biceps Femoris (BF), Vastus lateralis
(VL), Rectus femoris (RF) and Gluteus maximus (Gmax). Single
di erential EMG sensors were placed across the muscle belly
following the recommendations of the Surface Electromyogra-
phy for the Non-Invasive Assessment of Muscle function
(SENIAM) [ 15 ] .
Data analysis
Gross e ciency was calculated as the ratio of work done to
energy expended during the nal minute of each condition.
Work done was calculated from the power output during the
nal minute of each trial. Energy expenditure was determined
as the V
˙
O
2
multiplied by the caloric equivalent for the measured
RER [ 29 ] . The 250 W conditions elicited an RER > 1.00 for several
participants and thus invalidated the calculation of e ciency in
these cases due to the presence of an anaerobic energy contribu-
tion. To facilitate a greater sample size for data analysis at 250 W,
e ciency was also calculated regardless of whether the RER
> 1.00 (RER = 1.00 was assumed for caloric equivalent). The cal-
culation at 250 W therefore ignored the anaerobic energy contri-
bution; RER was compared across conditions to determine
whether the anaerobic energy contribution was equal between
TR and TT.
EMG data were analysed o ine using custom scripts (MatLab,
The Mathworks Inc., MA, USA). From the EMG recording, a 30-s
time window was selected for analysis. The time window began
at the start of the fth minute to coincide with the expired gas
collection. From the time window, data was recti ed and a lin-
ear envelope was created using a 4
th
order, low pass lter with a
cut o frequency of 15 Hz. Using the square wave pulse, EMG
recordings were linearly interpolated to provide a value for
every degree of crank movement, resulting in 360 samples per
revolution. The crank trigger was positioned on the bicycle. The
top dead centre (TDC) of the pedal revolution was de ned as 0 °,
with the bottom dead centre (BDC) occurring at 180 °. After resa-
mpling, these data were averaged for each degree of crank angle
to create an ensemble average that was representative of the
muscle activity for a complete revolution.
The onset and o set of muscle activity were de ned as the crank
angle where the EMG activity exceeded 20 % of the di erence
between peak and baseline activity [ 9 ] . Negative crank angles
were used to describe muscle onset that could start prior to TDC
(i. e., during the upstroke), but that occurred mainly during the
down stroke (e. g. VM, VL, Gmax and RF). As several muscles can
display a bi-phasic activity pattern [ 7 ] , the rst onset and sec-
ond (i. e., nal) o set was selected for analysis if 2 bursts of mus-
cle activity occurred. To determine muscle activity amplitude,
each muscle's activity level was normalized to the highest value
observed across all conditions for each participant. This pro-
vided an indication of the relative amplitude across conditions
and provided standardization between participants. The average
activity was calculated for the duration of the burst using the
normalized values. The product of the burst duration and aver-
age activity represented the integrated EMG of the burst, calcu-
lated to determine muscle activity level (iEMG) in arbitrary
units. The total muscle activity across muscles (iEMG
total
) was
calculated by summation of the iEMG for the 8 muscles.
Total force (F
r
) was calculated from the e ective force (F
e
) and
ine ective force (F
u
) at each degree of crank angle (Ø) for the
right pedal:
FFFT
ee
() () ()∅=
22
Subsequently, the index of force e ectiveness (IFE) was calcu-
lated according to [ 19 ] :
IFE
F
F
e
U
T
C
=
×
()
()
%
360
360
100
DC was calculated by combining the F
e
of the right and left side
to provide the net power production during each revolution. For
each revolution, this produces a sine wave pattern, with the 2
minima in power (around TDC and BDC) being determined and
averaged to provide minimum power. The ‘dead centre size’ (DC)
was calculated as the ratio between the minimum power and
the average power, as described by Leirdal and Ettema [ 23 ] :
DC
minimum power TDC minimum power BDC
average power
=
+
×
()/
%
2
100
The overall DC, calculated by averaging the DC across revolu-
tions, described the evenness of power production during the
revolution.
Statistical analysis
Changes in gross e ciency, muscle activity onset, o set and
iEMG
burst
and DC were analysed using 3 × 2 factorial ANOVAs
with repeated measures for work rate and ergometry. Pairwise
comparisons using Bonferroni corrections for multiple compari-
sons were used to identify signi cant di erences between con-
ditions. All statistical analyses were performed using SPSS 19.0
statistical analysis software (IBM, New York, USA). Results are
expressed as mean ± standard deviation (SD). Statistical signi -
cance was set at P < 0.05. Pearson’s correlations between e -
ciency and DC were compared at 150 and 200 W for TR and TT.
Pearson’s correlations between economy and DC were compared
at 250 W for TR and TT.
Results
N o d i erence between TR and TT was found for power output
(F
1,16
= 1.523; p = 0.235, TR: 201 ± 2 W, TT: 200 ± 2 W) and cadence
(F
1,16
= 2.908; p = 0.107, TR: 90 ± 1 rev · min
1
, TT: 91 ± 2 rev · min
1
).
E ciency
2 of the 19 participants were unable to complete the 250 W con-
ditions and so their data was excluded from the e ciency analy-
sis. There was no di erence in e ciency between TR and TT
(F
1,8
= 2.202; p = 0.176, TR: 18.8 ± 0.7 %, TT: 18.5 ± 0.6 %). RER
was not di erent between TR and TT (F
1,16
= 2.964; p = 0.104,
TR: 0.92 ± 0.04,TT:0.93 ± 0.05. Subsequently, it was considered
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523Training & Testing
Arkesteijn M et al. The E ect of Turbo Int J Sports Med 2013; 34: 520–525
appropriate to include all 17 participants. There was no di er-
ence in e ciency without the RER exclusion criteria (F
1,16
= 0.760;
p = 0.396, TR: 18.9 ± 0.7 %, TT: 18.7 ± 0.6 %).
Muscle activity timing
Onset
Turbo trainer cycling signi cantly a ected the onset of SOL
(F
1,15
= 5.405; p = 0.035) and RF (F
1,16
= 8.374; p = 0.011) compared
with treadmill cycling (
Table 1 ). SOL was recruited earlier dur-
ing the down stroke on the TR, whereas RF was recruited earlier
during the upstroke on the TT. GM showed a signi cant interac-
tion between cycling condition and intensity (F
2,34
= 10.289;
p < 0.001). The onset of GM only di ered between TR and TT at
150 W (TR: 71 ° ± 11 °, TT: 75 ° ± 11 °, p = 0.040), but not at 200 W
and 250 W (p < 0.05). No other muscle activity onsets were
a ected by the ergometry mode ( p > 0.05).
O set
Turbo trainer cycling signi cantly a ected the o set of SOL
(F
1,15
= 6.86; p = 0.019), GL (F
1,17
= 12.933; p = 0.002), BF (F
1,18
=
15.048; p = 0.001) and RF (F
1,16
= 10.299; p = 0.005) compared
with treadmill cycling (
Table 1 ). The o set of SOL, GL and BF
occurred later for TR. The o set of RF occurred later for TT.
Muscle activity level
iEMG
The iEMG for all muscles is shown in
Fig. 1 . TR showed sig-
ni cantly more activity in GL (F
1,17
= 31.054; p < 0.001), BF
(F
1,18
= 45.025; p < 0.001) and Gmax (F
1,10
= 10.152; p = 0.010;)
compared with TT. TT showed signi cantly more activity in TA
(F
1,18
= 7.395; p = 0.014), VL (F
1,18
= 8.333; p = 0.010) and RF
(F
1,16
= 11.284; p = 0.004) compared with TR.
N o d i erences between TT and TR for iEMG
total
were observed
(F
1,9
= 0.108; p = 0.75).
DC size
Work rate did not in uence DC size (F
2,36
= 2.018; p = 0.148). DC
was signi cantly higher in TR than TT (F
1,18
= 41.723; p < 0.001,
TR: 27.9 ± 5.0 %, TT: 23.4 ± 5.8 %) (
Fig. 2 ). A higher minimum
power output was observed for TR compared with TT
(F
1,18
= 51.047; p < 0.001, TR: 60.3 ± 11.6 W, TT: 51.6 ± 13.1 W).
I F E
TR decreased the IFE for the complete revolution (F
1,18
= 24.698;
p < 0.001) compared with TT (
Table 2 ). This was accompanied
by an increased IFE during the down stroke (F
1,18
= 224.905;
p < 0.001) and BDC (F
1,18
= 4.89; p = 0.040) for TR compared with
TT. In contrast, TT induced a larger IFE during the TDC compared
with TR (F
1,18
= 9.509; p = 0.006).
Correlation between e ciency and DC
There was no correlation between e ciency and DC at 150, 200
and 250 W for TR (150 W: p = 0.641; r = 0.122, 200 W: p = 0.303;
r = 0.265, 250 W: p = 0.225; r = 0.310) or TT (150 W: p = 0.582;
r = 0.149, 200 W: p = 0.632; r = 0.125, 250 W: p = 0.998;
r = 0.001).
Table 1 Onset and o set of muscle activity patterns during treadmill and
turbo trainer cycling. Values are mean ± SD averaged across 150, 200 and
250 W. Tibialis anterior (TA), Soleus (SOL), Gastrocnemius medialis (GM),
Gastrocnemius lateralis (GL), Biceps Femoris (BF), Vastus lateralis (VL), Rectus
femoris (RF) and Gluteus maximus (Gmax).* denotes statistically signi cantly
di erent from treadmill cycling.
Onset ( °) O set ( °)
Treadmill Turbo trainer Treadmill Turbo trainer
TA 196 ± 61 186 ± 56* 362 ± 12 361 ± 15
SOL 21 ± 13 24 ± 12 193 ± 54 172 ± 51*
GM 77 ± 12 77 ± 10 202 ± 26 199 ± 28
GL 72 ± 13 73 ± 11 240 ± 24 231 ± 31*
BF 42 ± 31 43 ± 34 183 ± 23 171 ± 27*
V L 32 ± 9 32 ± 10 98 ± 7 96 ± 8
R F 96 ± 20 103 ± 20* 52 ± 24 58 ± 24*
Gmax 7 ± 14 6 ± 13 110 ± 10 108 ± 10
Fig. 1 Muscle activity level (iEMG) for treadmill
cycling (grey circles) and turbo trainer cycling
(black circles) for the Tibialis anterior (TA), Soleus
(SOL), Gastrocnemius medialis (GM), Gastrocne-
mius lateralis (GL), Biceps Femoris (BF), Vastus
lateralis (VL), Rectus femoris (RF) and Gluteus
maximus (Gmax) at 150 W, 200 W and 250 W.
* denotes signi cantly ( p < 0.05) higher iEMG for
treadmill cycling compared with turbo trainer
cycling. # denotes signi cantly ( p < 0.05) higher
iEMG for turbo trainer cycling compared with
treadmill cycling.
100
50
TA
SOL
GL
VL
Gmax
*
*
#
GM
BF
*
RF
#
#
0
100
50
0
iEMG (a.u.)
100
50
0
100
150 200
Work rate (W)
250 200
Work rate (W)
250
50
0
100
50
0
100
50
0
100
50
0
100
150
50
0
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Discussion
The present study was the rst to compare the e ciency
between treadmill and turbo trainer cycling and showed no dif-
ferences exist. As power output, and therefore the amount of
work done were controlled between treadmill and turbo trainer
conditions, energy expenditure were also similar. Therefore, it is
unlikely that any scaling inaccuracies due to the nature of the
ratio used in the e ciency calculation would have a ected the
results [ 1 ] . However, muscle activity patterns were di erent,
where VL, RF and TA showed increases in muscle activity level of
respectively 7 %, 17 % and 14 % on the turbo trainer compared
with treadmill cycling. In contrast, Gmax, BF and GL were more
active during treadmill cycling by respectively 10 %, 19 % and
14 %. The change in muscle activity was re ected by a 15 % larger
DC in treadmill vs. turbo trainer cycling.
The stabilisation of the bicycle during turbo trainer cycling
induced a limitation in the movement of the bicycle compared
with the free moving bicycle on the treadmill. The additional
level of stabilisation could potentially explain the di erences
in muscle activity and pedalling technique. During treadmill
cycling, a large DC generates less intra-revolution oscillation in
cycling speed. Although speculative, it could be that cyclists
selected a larger DC to maintain a more constant position on the
treadmill. In addition, the requirement of balancing the bicycle
during treadmill cycling can a ect the magnitude of the lateral
sway of the bicycle, with lateral sway being constrained during
turbo trainer cycling. Lateral sway is induced by applying force
lateral to the bicycle contact points with the ground (i. e., the
position of the pedals relative to the wheels). The xation of the
bicycle in the turbo trainer could have allowed the production of
more force (and thus power output) during the down stroke, as
this would not result in an increased lateral sway. However, sub-
jective reports from the participants indicate that the cycling
experience on the turbo trainer was ‘unpleasant’, with the turbo
trainer feeling less ‘smooth’ compared with treadmill cycling.
The mechanical properties of the turbo trainer could thus also
have induced alterations in muscle activity and pedal forces
(discussed in more detail below).
The increased DC during treadmill cycling was caused by an
increased minimum power during the pedal revolution. This
re ects greater power production during the dead centres and
less power production during the down stroke and/or upstroke.
This is in agreement with the increased IFE during the bottom
dead centre for treadmill cycling compared with turbo trainer
cycling. In addition, turbo trainer cycling induced a less e ective
down stroke. The exact mechanism behind the alteration in ped-
alling technique is not clear. Gear ratio was held constant
throughout the study to prevent a potential e ect of this varia-
ble on pedalling technique [ 13 ] . Consequently, the average
resistance was comparable between turbo trainer and treadmill
cycling due to the matched work rates in both conditions using
the same gear ratio and cadence. Nevertheless, the turbo trainer
generates a constant resistance, due to the properties of the
magnetic motor brake. In contrast, the resistance during tread-
mill cycling can vary due to intra-revolution variations in cycling
speed. Resistance increases when moving forwards during
phases of high power production (i. e., down stroke) and
decreases when moving backwards during phases of low power
production (i. e., dead centre). Thus, it is anticipated that crank
angular velocity pro le would also di er, with larger variations
occurring during turbo trainer cycling compared with treadmill
cycling. The e ect of varying resistance is not accounted for in
the calculation of crank inertial load [ 13 ] . This provides a poten-
tial reason why varying crank inertial load on a stationary
ergometer does not induce alterations in cycling technique as
encountered during treadmill and turbo trainer cycling.
In contrast to the results of Duc, Bouteille, Bertucci, Pernin and
Grappe [ 10 ] , an increase in total muscle activity was not
observed during turbo trainer cycling in the present study. This
discrepancy might be explained by di erences in the muscles
studied and the type of turbo trainer employed. Nevertheless,
the absence of an increased overall muscle activity does indicate
that the work performed by the 8 main muscles involved in the
cycling action [ 17 ] is not di erent between treadmill and turbo
trainer cycling. This might explain why the present study did not
nd an increased metabolic cost and thus lower e ciency dur-
ing turbo trainer cycling.
Although total muscle activity did not change, a clear di erence
in the activity level of various muscles was observed between
treadmill and turbo trainer cycling. The lower DC during turbo
trainer cycling was accompanied by a greater activation of the
VL, RF and TA. VL and RF produce power predominantly during
the down stroke, via knee extension [ 11 , 18 ] . The increased
activity of RF and VL therefore provide a suitable explanation for
the increased power output observed in this region of the pedal
revolution. The function of TA is complex and it is unclear where
Table 2 Dead Centre size (DC) and index of force e ectiveness (IFE) during
treadmill and turbo trainer cycling. Values are mean ± SD averaged across
150, 200 and 250 W. TDC = Top dead centre, BDC = Bottom dead centre. ).
* denotes statistically signi cantly di erent from treadmill cycling.
Treadmill Turbo trainer
DC ( %) 27.0 ± 4.6 23.1 ± 5.3
IFE ( %)
overall (0 °–360 °) 41.5 ± 4.5 43.0 ± 4.4*
TDC ( 45 °–45 °) 49.9 ± 17.8 54.1 ± 19*
down stroke (45 °–135 °) 89.4 ± 1.6 87.1 ± 1.5*
BDC (135 °–225 °) 31.4 ± 3.6 30.3 ± 4.5*
upstroke (225 °–315 °) 71.7 ± 5.2 70.9 ± 5.1
Fig. 2 Dead Centre size (DC) for treadmill cycling (grey) and turbo
trainer cycling (black) at 150 W, 200 W and 250 W. * denotes signi cantly
( p < 0.05) higher DC for treadmill cycling compared with turbo trainer
cycling.
40
*
35
30
25
20
DC (%)
15
10
5
0
150 200 250
Work rate (W)
Downloaded by: University of Kent. Copyrighted material.
525Training & Testing
Arkesteijn M et al. The E ect of Turbo Int J Sports Med 2013; 34: 520–525
the increase in muscle activity occurred. The present study did
not incorporate localised muscle activity patterns and thus TA
could have increased during the upstroke or around the dead
centres. An increased activity during the upstroke could have led
to an increase in DC. However, TA often shows 2 separate bursts
around the dead centres at low to moderate work rates [ 17 ] . The
possible larger variations in crank angular velocity during turbo
trainer cycling could have increased the ankle extension veloc-
ity. Proprioceptive feedback from the ankle could thus have elic-
ited an increased activity of TA during the bottom dead centre to
limit the speed of extension of the ankle [ 6 , 25 ] .
The higher DC during treadmill cycling was accompanied by a
higher activation of the Gmax, BF and GL. The main period of
activity for BF and GL occurred around the latter stages of the
down stroke and during the dead centre, consistent with previ-
ous literature [ 17 , 30 ] . This matched the increased power pro-
duction around the dead centre for treadmill cycling. Gmax is
mainly active during the down stroke, albeit slightly later than
VM and VL [ 17 ] , and thus increased activity of Gmax in treadmill
cycling compared with turbo trainer cycling appears to be incon-
sistent with the increased DC. Gmax however spans the hip joint
and so its increased activity during treadmill cycling may be
related to stabilisation of the bicycle and upper body and not
power production. Although the overall activity of SOL did not
di er between treadmill and turbo trainer cycling, a prolonged
period of activity, combined with a lower average activity was
apparent, suggestive of a more equally distributed power pro-
duction.
Recently, con icting results regarding the relation between DC
and e ciency have been reported [ 22 , 23 ] . The present study did
not show a relation between DC size and e ciency for either
treadmill or turbo trainer cycling. In addition, exercise intensity
did not in uence DC size. The original positive relation found by
Leirdal and Ettema [ 22 ] is, therefore, not explained by a variation
in intensity with respect to DC. An alternative explanation might
be the positive relation between e ciency and intensity [ 12 ] . In
the present study a signi cant positive correlation between DC
and V
˙
O
2max
(LO
2
· min
1
) and MAP (W) (respectively r = 0.497 and
r = 0.463, p < 0.05) was found. The results of Leirdal and Ettema
[ 22 ] might, therefore, be explained by cyclists with a higher MAP
were cycling at higher power output, and thus were more e -
cient [ 12 ] . Rather than a correlation between e ciency and DC,
Leirdal and Ettema [ 22 ] might have been describing a relation
between MAP and DC. Future research is required to determine
whether or not there is a relation between MAP and DC.
In conclusion, cycling on a turbo trainer altered technique com-
pared with cycling on a treadmill. However, despite this change
in technique, cycling e ciency did not di er between treadmill
and turbo trainer cycling. The absence of a correlation between
e ciency and pedalling technique con rmed that pedalling
technique can be altered without a ecting cycling e ciency.
Acknowledgements
The authors gratefully acknowledge the cooperation of the
cyclists who took part in this study. No nancial support was
obtained for this study.
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... The majority of studies to date were limited to laboratorial assessments of forces involved in cycling motion due to the electronics involved in recording force signals into computers [46]. In order to measure power output, commercial power meters have been largely used in training and racing [47]. ...
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... The SRM cycle ergometer is widely used for testing and research (Arkesteijn et al. 2013;Bentley et al. 2001;Ferrer-Roca et al. 2014;Hansen et al. 2006). The cycle ergometer is computer-controlled and electromagnetically braked, which means that the cyclist can alter the cadence, while the cycle ergometer functions at a pre-programmed power output. ...
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Cycling is a repetitive activity using coordinated muscle recruitment patterns to apply force to the pedals. With more muscles available for activation than required, some patterns produce high power, whereas some are more efficient. The purpose of this study was to identify relationships between muscle coordination and factors affecting muscle coordination to explain changes in overall mechanical efficiency (ηO). Surface EMG, kinematics, and pedal forces were measured at 25%, 40%, 55%, 60%, 75%, and 90% V˙O(2max). Principal component analysis was used to establish muscle coordination, kinematic, and pedal force patterns associated with high and low ηO. At 55%-60% V˙O(2max), ηO was maximized and was highly related to the muscle coordination patterns. At high ηO, there was more medial and lateral gastrocnemii and soleus; less gluteus maximus, rectus femoris, and tibialis anterior; later medial and lateral vastii and biceps femoris; and earlier semitendinosus muscle activity resulting in an even distribution and synchronization of peak activity. Also, the ankle was more plantar flexed through the top and downstroke of the pedal cycle and more dorsiflexed during the upstroke for high ηO. The ηO was independent of the pedal force application. The results indicate that increased ηO is achieved through the coordination of muscles crossing the same joint, sequential peak activation from knee to hip to ankle, and reliance on multiple muscles for large joint torques. Also, muscle activity variability across the top and bottom of the cycle indicates that left and right leg muscle coordination may play a significant role in efficient cycling. These findings imply that cycling at 55%-60% V˙O(2max) will maximize the rider's exposure to high efficient muscle coordination and kinematics.
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The aim of this study was to establish the reliability of gross efficiency (GE) measurement (the ratio of mechanical power input to metabolic power output, expressed as a percentage) using the Douglas bag method. The experiment was conducted in two parts. Part 1 examined the potential for errors in the Douglas bag method arising from gas concentration analysis, bag residual volume, and bag leakage or gas diffusion rates. Part 2 of this study examined the within-subject day-to-day variability of GE in 10 trained male cyclists using the Douglas bag method. Participants completed three measurements of GE on separate days at work rates of 150, 180, 210, 240, 270, and 300 W. The results demonstrate that the reliability of gas sampling is high with a coefficient of variation (CV) <0.5% for both O2 and CO2. The bag residual volume CV was ∼15%, which amounts to +0.4 L. This could cause the largest error, but this can be minimized by collecting large gas sample volumes. For part 2, a mean CV of 1.5% with limits of agreement of +0.6% in GE units, around a mean GE of 20.0%, was found. The Douglas bag method of measuring expired gases and GE was found to have very high reliability and could be considered the gold-standard approach for evaluating changes in GE. Collecting larger expired gas samples minimizes potential sources of error.