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238
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ORIGINAL INVESTIGATION
International Journal of Sports Physiology and Performance, 2015, 10, 238-247
http://dx.doi.org/10.1123/ijspp.2014-0057
© 2015 Human Kinetics, Inc.
Effects of the Etna Uphill Ultramarathon
on Energy Cost and Mechanics of Running
Stefano Lazzer, Desy Salvadego, Paolo Taboga, Enrico Rejc,
Nicola Giovanelli, and Pietro E. di Prampero
Purpose: To investigate the effects of an extreme uphill marathon on the mechanical parameters that are likely to affect the energy
cost of running (Cr). Methods: Eleven runners (27–59 y) participated in the Etna SuperMarathon (43 km, 0–3063 m above sea
level). Anthropometric characteristics, maximal explosive power of the lower limb (P
max
), and maximal oxygen uptake were
determined before the competition. In addition, before and immediately after the race, Cr, contact (t
c
) and aerial (t
a
) times, step
frequency (f), and running velocity were measured at constant self-selected speed. Then, peak vertical ground-reaction force
(F
max
), vertical downward displacement of the center of mass (Δz), leg-length change (ΔL), and vertical (k
vert
) and leg (k
leg
) stiff-
ness were calculated. Results: A direct relationship between Cr, measured before the race, and race time was shown (r = .61, P
< .001). Cr increased signicantly at the end of the race by 8.7%. Immediately after the race, the subjects showed signicantly
lower t
a
(–58.6%), f (–11.3%), F
max
(–17.6%), k
vert
(–45.6%), and k
leg
(–42.3%) and higher t
c
(+28.6%), Δz (+52.9%), and ΔL
(+44.5%) than before the race. The increase of Cr was associated with a decrement in F
max
(r = –.45), k
vert
(r = –.44), and k
leg
(r = –.51). Finally, an inverse relationship between P
max
measured before the race and ΔCr during race was found (r = –.52).
Conclusions: Lower Cr was related with better performance, and athletes characterized by the greater P
max
showed lower
increases in Cr during the race. This suggests that specic power training of the lower limbs may lead to better performance in
ultraendurance running competition.
Keywords: maximal oxygen uptake, cost of transport, trail, kinematics, stiffness
The energy cost of running (Cr), together with maximal aerobic
power (VO
2max
), its fraction (F) sustained throughout the competi-
tion, and the maximal capacity of the anaerobic stores, represents
the main factor determining running performances.
1
Cr, dened as
the amount of energy spent above resting to transport 1 kg body
mass over 1 m distance (expressed in J · kg
–1
· m
–1
or mL O
2
· kg
–1
· m
–1
), plays a relevant role in determining performance in middle-
and long-distance runners with the same VO
2max
and F.
2
Its average
value is 0.182 ± 0.014 mL O
2
· kg
–1
· m
–1
(3.75 ± 0.29 J · kg
–1
·
m
–1
),
1
with an interindividual variability of about 10%, and with
lower values in endurance runners than in middle-distance runners.
Cr is unaffected by speed from about 2.2 to 5 m/s,
1
where air
resistance plays a minor role—less than 5% of the total energy cost.
3
In long-distance runners, Cr increases with the distance covered
because of fatigue effects. Brueckner et al
4
observed an increment
of Cr of about 0.142%/km of distance during a marathon, with a
total increase greater than 5%. Indeed, Gimenez et al,
5
in subjects
who ran 24 hours on a motorized treadmill, observed a substantial
increase in Cr after 8 hours; in addition, the subjects who main-
tained the highest speed (expressed in percentage of the velocity
attained at VO
2max
) were those having the smallest Cr increase over
the 24 hours. Furthermore, several authors
6,7
have shown that, in
mountain ultramarathons, the changes in Cr are brought about by
changes in the mechanics of running, the principal aim of which
is to minimize damage to lower-limb tissue, muscle fatigue, and
symptoms associated with prolonged running over irregular terrain
with a large positive/negative elevation variation along the race.
8,9
The mechanics of running in different conditions have been
frequently investigated using the spring-mass model,
10
that is,
representing the leg in contact with the ground as a simple linear
spring. In this model, the parameters most frequently studied are
the leg (k
leg
) and vertical (k
vert
) stiffness coefcients associated with
leg-spring deformation (ΔL) and with the vertical displacement (Δz)
of the center of mass, respectively. Thus, whereas k
vert
is a measure
of the resistance of the body to vertical displacement after applica-
tion of ground-reaction forces, k
leg
is the resistance to change in leg
length after application of internal or external forces.
The effects of long and ultralong races on running mechan-
ics have recently been investigated. Morin et al,
11
considering a
mountain ultramarathon race (166 km, total positive and negative
elevation of 9500 m), showed that athletes signicantly reduced (P
< .001) aerial time (t
a
), peak vertical ground-reaction force (F
max
),
and Δz with an increment in step frequency (f). On the other hand,
the contact time (t
c
) was not different from before the race. Fur-
thermore, there was a nearly signicant (P = .053) change in k
vert
,
which increased by 6% after the race. This study supports previous
ndings
12
where the same behavior of f, brought about by a shorter
t
a
with no changes in t
c
, was reported. Conversely, after 24 hours of
level treadmill running, Morin et al
13
observed a reduction in F
max
,
Δz, and ΔL and an increment in k
vert
and f, but with lower t
c
and
constant t
a
. This discrepancy in changes of t
c
and t
a
compared with
previous studies could be due to the different mechanics of uphill
and downhill mountain running compared with treadmill running.
As evidenced by Fourchet et al,
14
a 5-hour hilly run induces differ-
ent effects on ankle muscles than at running; in particular, only
plantar-exor muscles are affected by neuromuscular alterations,
Lazzer, Salvadego, Taboga, Rejc, and Giovanelli are with the Dept of
Medical and Biological Sciences, and di Prampero, the School of Sport
Sciences, University of Udine, Udine, Italy. Address author correspondence
to Stefano Lazzer at stefano.lazzer@uniud.it.
Energetics and Mechanics of Running 239
likely leading to different running mechanics between mountain
and at runs.
Indeed, interventions to reduce Cr are constantly sought after
by athletes, coaches, and sport scientists. Strength
15
and plyomet-
ric
16
training allow muscles and tendons to use more elastic energy
and to reduce the amount of energy wasted in braking forces, thus
reducing Cr.
Therefore, the purpose of the current study was to investigate
the effects of an extreme uphill marathon on several mechanical
parameters that are likely to affect Cr.
Research Design and Methods
Participants
Sixteen healthy Italian male runners (age range 27–59 y) were
enrolled in this study as participants in the uphill marathon named
the Etna SuperMarathon. The experimental protocol was approved
by the ethics committee of the University of Udine. Before the study
began, the purpose and objectives were carefully explained to each
subject, and written informed consent was obtained from all of
them. Subjects having overt metabolic and/or endocrine diseases
and those taking medications regularly or using drugs known to
inuence energy metabolism were excluded. The participants were
recruited from experienced ultraendurance runners who lled out
questionnaires on physical exercise activity, demographics, medi-
cal history, and lifestyle.
17
All the participants of this study had run
at least 1 ultraendurance race in their career. On average, subjects
had 9.3 ± 5.4 and 5.8 ± 5.6 years of training history and of running
ultraendurance races, respectively. They reported to run on aver-
age 69.2 ± 23.5 km every week. Sixteen athletes who were eligible
for the study began the race, and the 11 who completed the entire
competition were taken into account for data analysis.
Experimental Protocol
One week before the race, the subjects came to the exercise physiol-
ogy laboratory, where anthropometric characteristics, mechanical
power of the lower limbs, and a graded exercise test to exhaustion
on a treadmill were assessed. The subjects were asked to refrain
from any vigorous physical activity during the day preceding the
test and during the preliminary testing session that they performed
to familiarize themselves with all the different equipment.
The Etna SuperMarathon took place in June 2012. The race
started at 8 AM from the beach of Marina di Cottone (Catania,
Italy), at sea level, with temperature and relative humidity of 29°C
and 42%, respectively. Athletes covered about 30 km on the road
to the Etna volcano, while the last part of the race took place on
a path of lava rock. After a total distance of about 43 km, athletes
reached the nish line, covering an altitude difference of 3063
m with a mean slope of about 7% and with peak values reaching
14% (Garmin Forerunner 305 GPS, Kansas City, MO, USA). At
the nish, temperature and relative humidity were 21°C and 52%,
respectively.
The day before the race and immediately after the end of the
race (4 ± 2 min), body mass (BM), Cr, respiratory-exchange ratio
(RER), and running mechanics were measured.
Physiological Measurements Before the Race
BM was measured to the nearest 0.1 kg with a manual weighing
scale (Seca 709, Hamburg, Germany), and height was measured to
the nearest 0.001 m on a standardized wall-mounted board. Body-
mass index (BMI) was calculated as BM: kg/height
2
(m).
Maximal power of the lower limbs during a countermovement
jump was assessed by means of the Bosco et al
18
test (Ergo Jump,
Boscosystem, Italy). VO
2max
and maximal heart rate (HR
max
) were
determined during a graded exercise test on a treadmill (Saturn,
HP Cosmos, Germany) under medical supervision. During the
experiment, ventilatory and gas-exchange responses were mea-
sured continuously with a metabolic unit (Quark-b
2
, Cosmed,
Italy). The volume and gas analyzers were calibrated using a 3-L
calibration syringe and calibration gas (16.00% O
2
, 4.00% CO
2
),
respectively. During the tests, electrocardiogram was continuously
recorded and displayed online for visual monitoring, and HR
was measured with a dedicated device (Polar, Finland). Before
the start of the study, subjects were thoroughly familiarized with
treadmill running.
The tests were performed 1 week before the race and consisted
of a 5-minute rest period followed by running at 10 km/h for 5
minutes (treadmill slope: 1%); the speed was then increased by
0.7 km/h every minute until volitional exhaustion. A leveling off
of VO
2
(dened as an increase of no more than 1 mL · kg
–1
· min
–1
)
was observed in all subjects during the last 1 or 2 minutes of the
exercise test, indicating that VO
2max
had been attained. VO
2max
and
HR
max
were calculated as the average VO
2
and HR of the last 20
seconds of the test.
Cr and Mechanical Measurements
During the Race
The day before and immediately after the race, the subjects ran for
6 minutes at a constant self-selected speed on 2 oval compact rock
paths situated near the start line (at sea level) and near the nish
line (at 3063 m above sea level), respectively. Both compact rock
paths were at and 50 m long.
Cr and RER were measured continuously with a portable
metabolic unit (k4, Cosmed, Italy). The analyzer, calibrated before
each testing session, provided breath-by-breath data recording.
The last minute of sampling was used for further analysis. For all
subjects, real-time plots of VO
2
and RER indicated that metabolic
steady state was achieved after 5 minutes. Net VO
2
, obtained by
subtracting preexercise standing VO
2
(measured for 6 min in rest-
ing condition before the race) from gross VO
2
, was converted to
joules using an energetic equivalent for O
2
based on the RER. This
RER was always below 1.0, conrming that aerobic metabolism
was the main metabolic pathway. Cr was then obtained by dividing
net energy expenditure (J · kg
–1
· s
–1
) by running speed (v, m/s); the
latter was measured by means of 2 photocells placed immediately
before and after the video-recording zone (see below), with a dis-
tance of 10 m between them. In addition, average lap speed was
obtained by dividing the circuit length by the time needed to cover
it. Average lap speed was not signicantly different than running
speed measured in the video-recording zone. All subjects were
also asked to maintain the same self-selected speed during the tests
before and after the race.
The running mechanics were studied using a digital camera
with a sample frequency of 400 Hz (Nikon J1, Japan). The camera
was placed perpendicular to the running direction of the athletes.
For each subject, video was recorded between the fourth and the
sixth minutes of running. Ten subsequent representative steps were
analyzed, taking into account t
c
(s) and t
a
(s).
Step frequency (step/s) was calculated as f = 1/(t
a
+ t
c
). Given t
c
(s), t
a
(s), v (m/s), subject BM (kg), and lower-limb length (distance
240 Lazzer et al
between great trochanter and ground during standing, L in m),
spring-mass parameters were calculated using the computation
method proposed by Morin et al.
19
This method, based on modeling
of the ground-reaction-force signal during the contact phase by a
sine function, allows the computation of k
vert
(kN/m) as the ratio of
the F
max
(N) to the Δz (m). Then, k
leg
(kN/m) was calculated as the
ratio of F
max
to ΔL (m) during contact of the foot on the ground.
Statistical Analyses
Statistical analyses were performed using PASW Statistics 18
(SPSS Inc, Chicago, IL, USA) with signicance set at P < .05. All
results are expressed as mean ± SD. Normal distribution of the data
was tested using the Kolmogorov-Smirnov test. Changes of BM,
Cr, RER, and mechanical parameters during the competition were
studied with the Student paired t test. The relationships between
mechanical variables affecting Cr were investigated using Pearson
product–moment correlation coefcient.
Results
The physical characteristics before the race of the 11 subjects who
completed the race are reported in Table 1, together with their
performance time. Their average VO
2max
, Cr, and P
max
were 49.2
± 8.8 mL O
2
· m
–1
· kg BM
–1
, 0.190 ± 0.023 mL O
2
· m
–1
· kg
–1
,
and 1628 ± 212 W, respectively. As reported in Figure 1, a direct
relationship between Cr and race time was observed before (r = .61,
P < .001), as well as after (r = .48, P < .05), the race. Immediately
after the race, Cr was 8.7% higher (P < .001) than before the race;
on the contrary, BM and self-selected running speed were 5.7%
and 7.3% lower (P < .05), respectively, than before the race (Table
2). In addition, subjects showed signicantly lower t
a
(–58.6%),
f (–11.3%), F
max
(–17.6%), k
vert
(–45.6%), and k
leg
(–42.3%) and
higher t
c
(+28.6%), Δz (+52.9%), and ΔL (+44.5%) than before
the race (Table 2).
Table 1 Physical Characteristics of Subjects (N = 11)
Before the Race
Characteristic Mean ± SD Range
Age (y) 43.2 ± 11.0 27.0–59.0
Body mass (kg) 72.9 ± 10.2 57.0–88.0
Stature (m) 1.77 ± 0.07 1.63–1.85
Body-mass index (kg/m
2
) 23.1 ± 2.4 20.2–27.4
Lower-limb length (m) 0.89 ± 0.04 0.81–0.94
VO
2max
(mL · min
–1
· kg
–1
) 49.2 ± 8.8 37.9–61.5
HR
max
(beats/min) 176.8 ± 11.0 161.0–193.0
Cr (mL O
2
· m
–1
· kg
–1
) 0.190 ± 0.023 0.149–0.224
P
max
(W) 1628 ± 212 1319–1971
Race time (h:min:s) 6:14:01 ± 1:04:29 4:24:12–7:09:36
Abbreviations: VO
2max
, maximal oxygen uptake; HR
max
, heart rate; Cr, energy cost
of running; P
max
, maximal mechanical power of the lower limbs.
Note: 130 runners started the race, 109 completed it. Of the 11 runners of this study,
4 were classied within the 10th place, 2 between the 30th and 40th, 3 between the
50th and 60th, and 2 between the 70th and 80th.
Figure 1 — Race time plotted for all subjects as a function of the energy cost of running (Cr) measured before (closed circles) and immediately after
(open circles) the race.
To identify the main factors affecting Cr during the race, the
mechanical parameters measured before and after the race were
plotted for all subjects as a function of Cr. Pearson correlation
coefcients were then used to analyze the association between
variables entering these equations. This analysis showed inverse
relationships between Cr and F
max
(r = –.45; Figure 2[c]), Cr and
k
vert
(r = –.44; Figure 2[e]), and Cr and k
leg
(r = –.51; Figure 2[f]).
No signicant relationships between Cr and t
c
, t
a
, f, Δz, and ΔL were
found. Finally, an inverse relationship between mechanical power of
the lower limbs measured before the race and changes in Cr during
the race was found (r = –.52; Figure 3).
Energetics and Mechanics of Running 241
Table 2 Body Mass, Energy Cost of Running, Respiratory-Exchange Ratio, and Mechanical Parameters
Determined Before and Immediately After the Race, Mean ± SD
Before After Changes %
P
a
Body mass (kg) 72.9 ± 10.2 68.7 ± 9.8 –5.7 .001
Energy cost of running (mL O
2
· m
–1
· kg
–1
) 0.190 ± 0.023 0.207 ± 0.019 +8.7 .001
Respiratory-exchange ratio 0.88 ± 0.06 0.82 ± 0.08 –6.6 .123
Self-selected running speed (m/s) 2.89 ± 0.17 2.68 ± 0.39 –7.3 .024
Contact time (s) 0.291 ± 0.021 0.375 ± 0.027 +28.6 .001
Aerial time (s) 0.066 ± 0.028 0.027 ± 0.014 –58.6 .001
Step frequency (steps/s) 2.81 ± 0.18 2.49 ± 0.11 –11.3 .001
Maximal vertical ground-reaction force (N) 1380.0 ± 213.1 1136.4 ± 152.9 –17.6 .001
Downward displacement of center of mass during contact (m) 0.067 ± 0.007 0.102 ± 0.013 +52.9 .001
Displacement of the leg spring (m) 0.175 ± 0.020 0.253 ± 0.034 +44.5 .001
Vertical stiffness (kN/m) 20.72 ± 2.81 11.26 ± 1.97 –45.6 .001
Leg stiffness (kN/m) 7.90 ± 0.96 4.56 ± 0.85 –42.3 .001
a
Signicance by Student paired t test.
Figure 2(a) —Contact time (t
c
) measured before (closed circles) and immediately after (open circles) the race plotted for all subjects as a function of
the measured energy cost of running (C
r
).
Discussion
The main results of the current study showed that Cr is directly
related with the race time; Cr increased signicantly at the end of
this extreme uphill race (~9%); the increase in Cr was associated
with a decrease in F
max
, k
vert
and k
leg
; and the greater the mechanical
power of the lower limbs the lesser the changes in Cr due to the race.
Several authors have shown that Cr is an important part of suc-
cess in athletes with comparable VO
2max
and F, even if conicting
results have also been reported.
2
Millet et al
20
observed, during a
24-hour treadmill run, that Cr was not directly related to perfor-
mance but may nevertheless be important to be able to maintain
a high %VO
2max
. In addition, Gimenez et al
5
have shown that Cr
measured before a 24-hour treadmill run was negatively correlated
with the speed expressed in %VO
2max
. This nding suggests that
a low Cr could be important in determining performance during
“low-intensity” ultraendurance events, and our results support this
view, since Cr was strongly related with race performance (Figure 1).
242
Figure 2(c) — Maximal vertical ground-reaction force (F
max
) measured before (closed circles) and immediately after (open circles) the race plotted
for all subjects as a function of the measured energy cost of running (C
r
).
Figure 2(b) — Aerial time (t
a
) measured before (closed circles) and immediately after (open circles) the race plotted for all subjects as a function of
the measured energy cost of running (C
r
).
243
Figure 2(d) — Downward displacement of center of mass during contact (Δz) measured before (closed circles) and immediately after (open circles)
the race plotted for all subjects as a function of the measured energy cost of running (C
r
).
Figure 2(e) — Vertical stiffness (k
vert
) measured before (closed circles) and immediately after (open circles) the race plotted for all subjects as a func-
tion of the measured energy cost of running (C
r
).
244
Figure 2(f) — Leg stiffness (k
leg
) measured before (closed circles) and immediately after (open circles) the race plotted for all subjects as a function
of the measured energy cost of running (C
r
).
Figure 3 — Maximal mechanical power of the lower limbs (P) measured before the race plotted for all subjects as a function of changes in energy
cost of running caused by the race (ΔCr).
Energetics and Mechanics of Running 245
At the end of this extreme uphill race, Cr was increased by
about 9% compared with before the race, as observed in previous
studies considering ultramarathon events.
5,6
This difference was
greater than those observed during classic at marathons,
4
prob-
ably because of the relevant slope and altitude difference covered
by subjects and because of the type of road surface. As observed
previously,
21
the increase in Cr with the slope is related with the
increase in total work including internal work. Furthermore, in the
last part of the race (~15 km), the subjects ran on a path of lava
rock. This terrain can contribute to increasing Cr compared with
compact terrain and could be attributed to a reduced recovery of
potential and kinetic energy at each stride.
22
Indeed, as suggested
by Millet et al,
6
during long-distance running events greatly exceed-
ing the marathon, maintaining a high F may help reduce damage to
lower-limb tissue, muscle fatigue, and symptoms associated with
prolonged running, even if such a strategy may lead to increased Cr
values, thus, in the end “sacricing economy to improve running
performance.” On the other hand, in agreement with our results,
some authors
23,24
are of the opinion that Cr in ultramarathon run-
ners has an important role in setting performance, suggesting that
the same phenotype and physiological factors, including Cr, that
determine success in marathon running
25
are also likely to determine
success in ultramarathons, and this should be even more evident
when the level of ultraendurance athletes increases.
23
Moreover, we do not think that the increasing altitude (from
0 to 3063 m above sea level) had any effect on Cr, although obvi-
ously leading to a fall of about 10% to 15% on VO
2max
. We would
like to point out that at sea level, before the race, VO
2
at the speed
of 173 m/min was on the average 42.7 mL · kg
–1
· min
–1
—about
87% of the corresponding VO
2max
. At altitude, immediately after
the race, VO
2
was reduced to 36 mL · kg
–1
· min
–1
at the speed of
161 m/min—about 80% to 85% of the corresponding VO
2max
esti-
mated at altitude. The O
2
consumption of the respiratory muscles,
as obtained from the expiration ventilation according to Coast et
al,
26
amounted to 188 and 170 mL/min at sea level and at altitude,
respectively. Thus, Cr, when subtracting the O
2
consumption of
the respiratory muscles and the resting VO
2
(4.4 and 4.6 mL · kg
–1
· min
–1
at sea level and at altitude) amounted to 0.171 and 0.183
mL · kg
–1
· min
–1
, respectively. The resultant increase of Cr, about
7%, is therefore essentially equal to that reported above. Then, the
observed increase of Cr is independent of the effects of altitude on
VO
2max
and on ventilation, which, as is well known, are widely dif-
ferent in different subjects and lead to larger decreases in individual
VO
2max
27
the larger its sea level value.
28
In addition, we would like to point out that the RER amounted
to 0.88 and 0.82 at sea level and at altitude, respectively, and that
these values are close to what can be expected for the metabolic
respiratory quotient for these exercise intensities.
At the end of the race, the following changes in running
mechanics were observed: lower t
a
, f, F
max
, k
vert
, and k
leg
and higher
t
c
, Δz, and ΔL (Table 2). Only the decreases of t
a
and F
max
were in
line with previous studies on ultraendurance events.
11,13,29
These
differences could be related to the fact that the subjects ran, before
and after the race, at self-selected speed that represented their real
optimal running speed. At the end of the race, subjects decreased
their self-selected speed during the test by 7.3% on average; this
reduction was related with their degree of fatigue and represents
the real effort that they were able to sustain after the race. However,
the changes in self-selected running speed observed during the test
before and after the race had only a partial effect on changes in
the mechanical parameters considered in the current study. In fact,
as observed previously,
30
k
leg
showed no statistical differences at
speeds of 2.5 to 3.5 m/s; in addition, the speed has no effect on
k
leg
.
19
Indeed, if the speed was reduced from 2.9 to 2.7 m/s, k
vert
decreased from 33 to 32 kN/m (–4%),
30
which was not statistically
signicant. Morin et al
19
did not measure k
vert
at speeds as low as
2.9 and 2.7 m/s; even so, we tted the data points reported in their
study with a second-order polynomial, obtaining the equation k
vert
= 1.512s
2
– 6.906s + 34.022, where k
vert
is expressed in kN/m and
the speed (s) in m/s (N = 5 data points, r
2
= .997). According to
this equation, at 2.9 and 2.7 m/s, k
vert
would be 27 and 26 kN/m
1
,
respectively (–1%). In the current study k
leg
decreased by 42.3% and
k
vert
by 45.6%, thus suggesting that the changes in these mechanical
parameters observed in the current study were largely affected by
fatigue, and only marginally by speed.
In addition, at the end of the race t
c
increased (by ~29%) and
t
a
decreased (by ~59%), leading to a signicant decrease in f (by
~11%). In turn, the observed increase of t
c
led to a signicant
increase in Δz (by ~53%) and ΔL (by ~45%). Furthermore, k
vert
and k
leg
decreases were strongly related to a reduction in F
max
and
to the increase in Δz, which can be interpreted as a safer running
style, as discussed following.
The differences in the changes in the mechanical para-
meters between the current study and the previous ones on ultra-
marathon
11,13,29
can be explained as follows.
• We considered self-selected speed as representative of subjects’
fatigue level, which induced different mechanical adaptations,
particularly increasing t
c
and consequently reducing t
a
and f.
Dutto and Smith
31
reported decreases in f accompanied by a
decrease of k
vert
in long running trials, suggesting that it is the
inability of the system to maintain an optimal stiffness that
leads to exhaustion. Furthermore, the decrease in f observed
at the end of the race was probably related to the fact that this
ultramarathon was characterized by continuous positive work.
This condition implies mainly concentric muscle contractions,
which induce less muscle damage in knee-extensor and plantar-
exor muscles than the eccentric contractions characterizing
downhill running generally included in ultramarathon.
8,9
This
condition may lead to lesser changes in running mechanics
(aiming at decreasing the load on the muscles) than observed
in previous extreme ultramarathons.
11,13,29
In addition, the
decrease in f observed in the current condition is likely associ-
ated with a decrease in internal work performance and thus in
the corresponding cardiorespiratory responses, which in turn
may be particularly relevant when running uphill at 3000 m
above sea level.
• There was a greater continuous positive work performance
than observed in previous studies,
11,29
which did not allow any
recovery periods for the athletes during the race.
• The potential differences between ultra-long-distance running
on a treadmill and over ground
13,20
may have induced different
adaptations of t
c
.
• The postrace tests were done immediately after the subjects
crossed the nish line, which allowed us to examine the real
effects of total fatigue on metabolic and mechanical parameters.
To identify the main factors affecting Cr during the ultraendur-
ance running race, the effects of changes on mechanical parameters
before and after the race were plotted for all subjects as a function
of the corresponding changes on Cr (Figures 2[a–f]). In particular,
the increases in t
c
with decreases in t
a
imply a decrease in F
max
,
which was related with the increase in Cr during the race (Figure
2[c]). These changes in running mechanics can be interpreted as a
246 Lazzer et al
safer running style associated with an overall lower impact, espe-
cially during the eccentric phase of each step, to the detriment of
an increase of Cr.
6
The decrease of k
vert
and k
leg
, brought about by fatigue, induced
each runner to sink farther during contact, that is, increasing t
c
and
Δz. Furthermore, the decreased f likely led runners to a less efcient
elastic energy utilization,
32
and therefore lower velocity, at the end
of the stance phase, resulting in a decreased t
a
. Finally, a shorter
t
a
implies that the runner landed with less downward momentum,
thus requiring less upward impulse during the subsequent stance
phase, so F
max
was also lower. In addition, decreased F
max
can
also be due to reduced force capacity because of fatigue during
the race. Our results are in accordance with those of Morin et al
13
and Degache et al,
29
who evidenced a decreased F
max
at the end
of long running trials; however, the question of whether this is a
strategy intentionally adopted by runners or the result of fatigue
remains unsolved.
Indeed, the most powerful athletes showed lower changes in
Cr (Figure 3). These results are in agreement with previous studies
in athletes
15,16
that emphasize the importance of the muscle–tendon
system and strength training to reduce Cr. In addition, force reduc-
tion during the race can lead to ankle instability,
33
thus leading to
a reduction of the foot’s capacity to use all the mechanical energy
transmitted by the muscle-tendon complex for forward displacement.
Practical Applications
Cr represents one of the main factors determining performance
in ultraendurance runners, and its increase during competition is
related to mechanics of running deterioration and lower P
max
. These
data show the importance of the lower-limb muscle’s characteristics,
which maximize efciency and reduce Cr during running. This sug-
gests that coaches and ultraendurance runners need to strengthen
specic lower-limb power training in their preparation.
Conclusion
The increased Cr during the Etna uphill marathon was related to
changes in the mechanics of running, such as increases in t
c
, Δz,
and ΔL and decreases in t
a
, f, F
max
, k
vert
, and k
leg
. In addition, lower
Cr was related with better performance, and athletes characterized
by the greater P
max
showed lower increases in Cr during the race.
This suggests that specic power training of the lower limbs may
lead to better performance in ultraendurance running.
Acknowledgments
We are grateful to the athletes for their kind collaboration and to Mr M.
Maltana, Mr E. Bertolissi, and the Unione Sportiva M. Tosi, Tarvisio
(Italy), for their valuable contribution in carrying out measurement during
the race. We are grateful to Prof G. Antonutto, Prof B. Grassi, and Dr A.
Da Ponte for the assistance during the study. The nancial support of the
Unione Sportiva M. Tosi, Tarvisio (Italy), and Lions Club, Udine-Duomo
(Italy), are gratefully acknowledged.
No conicts of interest, nancial or otherwise, are declared by the
author(s).
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