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Resisted sprinting in the form of both sled pushing and pulling is a popular training method to improve speed capability, although research has been biased towards investigating the effects of sled pulling. Practitioners need to understand whether the sled push and pull offer differential training effects, and hence their utility in influencing sprint kinematics and kinetics for targeted adaptation. Furthermore, there are a number of recent developments in loading and assessment that warrant discussion, given the impact of these techniques on understanding the load-velocity relationship and optimizing horizontal power output. Finally, some thoughts regarding load prescription are shared with the reader.
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Sled Pushing and Pulling
to Enhance Speed
´l J. Cahill, MSc,
John B. Cronin, PhD,
Jon L. Oliver, PhD,
Kenneth P. Clark, PhD,
Rhodri S. Lloyd, PhD,
and Matt R. Cross, MSc
Athlete Training and Health, Plano, Texas;
Sports Performance Research Institute New Zealand, Auckland University
of Technology, Auckland, New Zealand;
School of Medical and Health Sciences, Edith Cowan University, Perth,
Cardiff School of Sport and Health Sciences, Wales, United Kingdom;
Department of Kinesiology, West
Chester University, West Chester, Pennsylvania;
Laboratoire Interuniversitaire de Biologie de la Motricite
´, University
Savoie Mont Blanc, Chambe
´ry, France; and
WINTEC, Hamilton, New Zealand
Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided
in the HTML and PDF versions of this article on the journal’s Web site (
Sprinting is a critical factor neces-
sary for individual and team sport
success (5,13,14,37). The success
of a sprint is determined by the ability
to accelerate, the extent to which max-
imal velocity is achieved, and the abil-
ity to maintain that velocity against the
onset of fatigue (14). Team sports how-
ever such as rugby, Gaelic football, and
Australian football have been shown to
exhibit multiple short-distance acceler-
ations upward of over 100 per game,
typically between 10 and 20 m
(9,16,27,50). In professional soccer
players, the mean duration of sprints
completed during a soccer game is re-
ported to be between 2 and 4 seconds
(52). Given the recurrence of short-
distance acceleration in many common
field-based team sports, one could
argue that the development of this
phase outweighs the benefit of time
spent isolating the development of
maximum velocity (e.g., sprint
mechanics) in all but “pure” speed
sporting codes. Horizontal force pro-
duction and the orientation of the force
vector are strong influencers of an ath-
lete’s ability to accelerate (21,35). Iden-
tifying training methods to improve
horizontal force production and the
orientation of the force vector would
seem important for the improvement
of this motor quality.
Most studies that examine training and
improvements in sprint speed use non-
specific forms of training, such as
strength, plyometric, or combined
training methods (7,15,17,19,34,40).
Those methods have been shown to
be effective at improving acceleration
and sprint performance (45), which
may be partly due to resistance training
requiring large amounts of force pro-
duction during triple extension of the
lower limbs, replicating movement
mechanics of sprinting. There are
fewer studies that examine sprint-
specific training, but from the studies
that do exist it has been suggested that
sprint-specific training transfers greater
gains to acceleration and speed than
nonspecific training (45). Sprint-
specific training may include both un-
resisted and resisted forms of sprinting.
Unresisted and light-resisted sprinting
may provide a speed stimulus while
maintaining sprint mechanics (2,25).
Address correspondence to Michea
´l Cahill,
resisted sled sprinting; sled pushing;
sled pulling; acceleration; horizontal
force; horizontal strength training
Copyright ÓNational Strength and Conditioning Association Strength and Conditioning Journal | 1
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Heavy-resisted sprint training will pro-
vide a different stimulus, overloading
force producing capabilities of the ath-
lete (36). Although the lower limbs will
triple extend during vertical resistance
and heavy-resisted sprint training, the
latter will alter the force orientation,
requiring a greater horizontal force
vector that may transfer greater train-
ing gains to free sprinting. However,
until recently, research has focused
more on light-resisted sprint training
and less on heavy-resisted sprint
Sled pulling and sled pushing are 2 of
the most commonly used forms of re-
sisted sprinting. Although they are
both forms of resisted sled sprinting,
differences in terms of size, shape,
force application, and friction will
most likely lead to changes in mechan-
ics, load prescription, and training out-
comes. Therefore, this article aims to
critique the literature regarding the
effect of sled pulling and pushing on
sprint performance, to highlight poten-
tial differences between the conditions,
and to describe how load prescription
can be individualized for specific train-
ing outcomes.
Both pushing and pulling sleds are
training devices that allow for varia-
tions of external load to be applied
during sprinting and sprinting deriva-
tives. Operationally, sled pulling and
pushing differ primarily in how they
provide a posterior and anterior load-
ing stimulus on the athlete. These dif-
ferences have necessitated different
designs, which have resulted in push-
ing sleds typically being larger and
heavier than pulling sleds. Sleds are
relatively inexpensive, readily accessi-
ble, and the resistance can be easily
adjusted from light to very heavy
loads. Consequently, sled pulling has
been a popular method among
coaches of numerous sports to
improve sprint speed and particularly
acceleration performance (42).
Although the use of sled pushing has
been used by sports such as American
football and rugby as a technical
exercise during practice, the use of
the sled push for improving sprint per-
formance is a newer training phenom-
enon. Currently, there is very limited
research available detailing the use of
this form of training, especially as it
pertains to sprint performance (Figures
1 and 2).
An overview of the acute cross-
sectional studies that have investigated
resisted sled pulling and pushing can
be observed as the supplementary
material to this article (see Video, Sup-
plemental Digital Content 1, http:// For
a detailed review on resisted sled sprint
training studies, the reader is directed
to a recent review by Petrakos et al.
(42). There are a number of limitations
that the reader should be cognizant of
when interpreting the results of the re-
viewed research. By understanding
these limitations, the reader will better
appreciate the quality of the research
and its generalizability. This in turn will
allow for coaches, practitioners, and
researchers to determine the signifi-
cance and application of these findings
to their respective fields (see Table 2,
Supplemental Digital Content 2,
The authors have identified 41 studies
that have examined resisted sled
sprinting and its effect on acceleration,
maximal velocity, muscle activity, and
friction coefficients, the majority of
which used sled pulling. To the au-
thors’ knowledge, only 5 studies have
examined the effects of sled pushing;
Seitz et al. (49) found a sled push of
75% body mass (BM) with rest inter-
vals of between 4-12 minutes led to
greater postactivation potentiation
(PAP) in an unresisted sprint over a sled
push of 125% BM. Although Waller
et al. (55) reported sprint times, the
emphasis of the study was in relation
to blood lactate response of repeated
Figure 1. Sled pulling device.
Sled Pushing and Pulling
VOLUME 00 | NUMBER 00 | MONTH 2019
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
sprint ability. Also, Maddigan et al. (26)
studied a comparison of muscle activity
from sled pushing with the back squat
and found higher levels of muscle
activity in gastrocnemius during sled
pushing (26). The remaining published
articles by Tano et al. (53,54) were con-
ducted using handheld stop watches
that have been shown to produce faster
times compared with electronic timing
systems (18,28) and published in an
open access journal that has been
heavily criticized by the British Asso-
ciation of Sport and Exercise Science.
Consequently, the research is not con-
sidered robust and has been excluded
from the supplementary table and will
not be discussed further. A wide range
of participants has been studied from
youth amateur athletes to high-level
sprinters. Most research is in male ath-
letes, with limited research in females
or youth. Therefore, the transferability
of interpretations to wider training
cohorts is limited by the available
research. Most training studies focused
on the early acceleration phase
between 0 and 20 m with some authors
including max velocity splits between
20 and 50 m. Load has been expressed
primarily in terms of absolute load, per-
centage decrement in velocity, and per-
cent BM (%BM) with the latter being
the most common. The load-speed
relationship and kinematic and kinetic
variables have been examined at loads
ranging from 2.5 to 125% of BM across
different populations. Sprinting accel-
eration is determined by the expression
and orientation of ground reaction
forces (GRFs). Resisted sprinting
works by providing resistive stimuli in
the effective direction of the sprint. In
sled sprinting, the magnitude of this
stimulus is determined by the magni-
tude of loading applied to the sled, fric-
tion (sled material, ground, etc.), the
towing/pushing velocity (on some
surfaces), and to a lesser degree the
angle of pull between the athlete and
the sled (3). The application of load
provides an additional resistive vector
for force to be produced against, mean-
ing an athlete can generate and main-
tain conditions of (significantly greater)
net horizontal force in stable and tar-
getable conditions.
As observed in the Table, most studies
published before 2014 used lighter
loads (,32% BM) with kinematic var-
iables assessed that found reductions in
velocity, stride length, stride frequency,
flight time, and increases in contact
time. Changes were also found in angu-
lar kinematics at different loads. Con-
sequentially, researchers previously
recommended loading parameters
should not exceed approximately 13%
BM (25) or cause .10% decrease in
maximum velocity (2,51), as going
beyond this disrupts sprint technique.
More recent studies (8,12,21,57) have
examined kinematic analysis of heavier
loads that may cause deviations from
the unresisted sprint technique but
may provide a disparate physical stim-
ulus. Those studies have included
kinetic data analysis such as theoretical
maximum force (Fo), theoretical max-
imum velocity (Vo), peak power pro-
duction (Pmax), horizontal force,
vertical force, ratio of forces, GRFs,
and rate of force development (see
Video, Supplemental Digital Content
Impulse is the integral of force over
the time in which it is applied; a heavier
load will require greater forces to be
produced over a longer period during
the push-off phase, leading to greater
impulse when compared with lighter
loads. This is shown to be evident in
resisted sled training; researchers have
found heavier loads superior to lighter
loads during resisted sled sprinting to
acutely increase GRF impulses (8,21).
Longitudinal research has also found
heavier loads superior to lighter and
unresisted groups in terms of improv-
ing sprint performance (4,20,36). Ka-
wamori et al. (21) found that the
greater horizontal and propulsive im-
pulses found in the heavier group were
Figure 2. Sled pushing device.
Strength and Conditioning Journal | 3
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mainly due to prolonged contact time
and propulsive duration rather than
force magnitude, as the mean and peak
values of propulsive GRFs were not
significantly different between heavy
and control groups.
Differences between sled pushing
and pulling
Researchers have examined the kine-
matics and kinetics of resisted sled
pulling in some detail (22,24,32,41).
The sled pull is consistently reported
to reduce an athlete’s stride length and
stride frequency as load increases
(25,33,38). For example, stride length
reduced significantly more with
a heavier load of 20% BM (Y11.2%)
in comparison with a lighter load of
15% BM (Y6.8%) (10). Angular kine-
matics have also been studied during
sled pulling, and findings show joint
angles at the hip and trunk increase
compared with unresisted sprinting
(11,33). Furthermore, trunk angle for-
ward lean has been shown to increase
as sled loads increase (1,10). Although
the velocity of the sprint decreases
with increasing load, sled pulling may
cause an increase in forward lean,
which could enhance horizontal force
production. Harness attachment can
also influence sled pull kinetics, and
practitioners typically choose between
attaching the sled to either the waist or
shoulder. Bentley et al. (6) examined
the point of attachment for the harness
during sled pulling and recommended
the waist, stating that it led to greater
net horizontal impulses ([22.5%)
Influence of sled load on spatiotemporal characteristics of sprint performance
Authors Subjects Load Vel SL SF CT FT
Lockie et al. (25) Healthy male field sport athletes
(n523; mean age 23.1 yrs)
12.6% BM
32.2% BM
Murray et al. (38) Male rugby and soccer players
(n533; mean age 21.1 yrs)
10% BM
20% BM
Maulder et al. (33) National and regional
competitive male track
sprinters (n510; mean age
20 yrs)
Alcaraz et al. (1) Competitive sprints and long
jump athletes (n518; mean
age 22 yrs) (11 males and 7
Y8% Y5%
Alcaraz et al. (2) Male competitive track and field
athletes (n526; mean age 20
6% BM
10% BM
15% BM
Rumpf et al. (45) Male children (n535; mean age
13 yrs) (19 pre-PHV and 16
2.5% BM
5% BM
10% BM
Martinez-Valencia et al. (30) Male competitive sprinters
(n57) and team sport athletes
(n514) (n521; mean age
18 yrs)
5% BM
10% BM
15% BM
20% BM
25% BM
30% BM
Kawamori et al. (20) Physically active collegiate team
sport males (n510; mean age
28 yrs)
10% BM
30% BM
BM 5body mass; CT 5contact time; FT 5flight time; PHV 5peak height velocity; SF 5stride frequency; SL 5stride length.
Sled Pushing and Pulling
VOLUME 00 | NUMBER 00 | MONTH 2019
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when compared with a shoulder
attachment ([17.5%). This is likely
linked to different frictional properties
of the sled and in the amount of for-
ward lean and foot placement relative
to the center of mass when attaching
the sled to the waist and shoulder. It
would appear that research is yet to
examine the kinematics and kinetics
of sled pushing; however, pushing with
the arms does appear to further
increase forward lean (Figure 3) and
alter foot placement, which may favor
increased horizontal impulse during
The percentage of BM (%) is the most
commonly used method for load pre-
scription. The major limitation of this
method is that it does not account for
the effects of changing friction coeffi-
cients. Linthorne and Cooper (23)
found substantial differences between
the coefficients of friction between 4
surfaces: synthetic athletic track, natu-
ral grass rugby pitch, 3G football pitch,
and an artificial grass hockey pitch. Sig-
nificant difference between surfaces
also significantly affected the rate of
increase in 30-m sprint time (23). Cross
et al. (12) found a linear relationship
between friction force and addition of
mass, suggesting no effect on the
dynamic friction coefficient, but
instead found towing velocity a deter-
mining factor on overall sled resistance.
These factors must be taken into
account, as they will most likely cause
a practical difference of the loading
experienced by the athlete. When sled
pulling and pushing one could assume
that the application of a given loading
protocol could differ for a number of
reasons. Push sleds are typically bigger
in size and may have a larger surface
area of the sled that interacts with the
ground, increasing the coefficient of
friction and providing a different level
of resistance. Given the likelihood of an
increased forward lean onto the push
sled due to the use of the arms resting
on vertically aligned poles (Figures 3B–
D), increased frictional forces between
the sled and surface underneath could
result. This in turn would reduce the
athlete’s velocity during sprinting. The
use of an athlete’s arms during sled
pulling could assist in the drive phase
of acceleration, thus increasing the ath-
lete’s velocity. Finally, the anterior
position during sled pushing in com-
parison with posterior position during
sled pulling may influence the activa-
tion of certain muscle groups and
sprinting mechanics, and as a result
affect the velocity profile. Depending
on design, both types of training offer
a different training stimulus. Coaches
and practitioners should be aware of
the effects of different friction coeffi-
cients between all sled devices and
the limitations that exist around pre-
scription of loads based on %BM alone;
ultimately, the same %BM load cannot
be assumed to produce the same chal-
lenge in a pull versus a push sled exer-
cise or during resisted sprinting on
different surfaces.
Careful consideration should also be
given to the equipment set-up, with
factors such as tow rope length and
points of attachment to the athlete
(shoulder harness versus waist belt)
during the sled pull, and the length of
the vertical poles and hand position
Figure 3. Competitive female sprinter pushing and pulling loads at 33, 66, and 99% BM, respectively. (A) Unresisted sprint, (B) 33%
BM sled push, (C) 66% BM sled push, (D) 99% BM sled push, (E) 33% BM sled pull, (F) 66% BM sled pull, and (G) 99% BM
sled pull. BM 5body mass.
Strength and Conditioning Journal | 5
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during a sled push. These factors, in
conjunction with load, will determine
force orientation and potentially the
subsequent adaptation. Limited
research is available examining the
effect of the waist belt versus shoulder
harness and different hand position in
sled pushing while sprinting at heavier
loads. The use of the waist belt may
externally cue an athlete to push their
hips into extension; however, at very
heavy loads as observed in
Figure 3G, the load may be too heavy
and cause the athlete to flex at the
waist. The shoulder harness may seem
like the obvious alternative; however,
the nature of the shoulder straps can
cause irritation, pinching, and discom-
fort during sprinting at heavy loads,
and the increased angle of the tow cord
may also negatively influence the kinet-
ics and kinematics of the sprint. It may
be that if waist harnesses are used for
sled pulling at heavier loading, then the
practitioner may consider switching
techniques to a sled push for heavier
loads or loads that cause a greater dec-
rement in maximum velocity.
A competitive female sprinter can be
observed in Figure 3, pushing and pull-
ing loads of 33, 66, and 99% BM,
respectively. As stated previously, com-
parative analysis between both condi-
tions is limited, but general
interpretations can be made across
loads of the same condition expressed
as %BM. Each image is captured at toe
off of the stance leg during the second
step of both unresisted and resisted
sprinting. With regard to the sled pull-
ing, what is noticeable is that the sled
set-up across loads of 33 and 66% (Fig-
ures 3E and F) allows for relatively
similar body positions to the unresisted
sprint (Figure 3A). With the heaviest
load (Figure 3G), however, a noticeable
change in trunk flexion is observed. In
terms of the sled pushing, the equip-
ment set-up resulted in the athlete hav-
ing a greater trunk lean as compared to
the unresisted sprint condition
(Figure 3A), and this posture was main-
tained across all loads (Figures 3B–D).
Given that the resistance is based on
the same %BM rather than the %BM
that caused the same decrement in
velocity (compared with unresisted
sprinting), it is not possible to directly
compare sled pushing and pulling,
other than the position of the swing
leg thigh and foot relative to the
ground is lowered as load increases in
both conditions.
There is enough literature suggesting
that heavier sled loads and the resul-
tant increased forward lean could lead
to an acute increase in horizontal force
application while performing resisted
sprints (8,21,31). It is important to con-
sider however that excessive forward
lean due to increased load could be
detrimental to the transference effect
of training. More longitudinal research
is needed across different populations.
However, this supposition has been
supported in a recent training study
by Morin et al. (36) who reported that
very heavy sled loads of ;80% BM
clearly increased maximal horizontal
force production compared with stan-
dard unloaded sprint training (effect
size [ES] 50.80 versus 0.20 for inter-
vention and controls, respectively) and
mechanical effectiveness that is more
horizontally applied force (ES 50.95
versus 20.11 for controls). One would
expect the same sort of adaptation
given the posture of the body during
sled pushing. The anterior position of
the sled push may cause the exercise to
be viewed as more of a horizontal
strength training exercise given the
arms are in a fixed position. By switch-
ing from a heavy sled pull to a heavy
sled push at loads that cause a greater
reduction in unresisted speed (.65%),
an athlete may increase hip extension
and maintain postural forward lean but
sacrifice the use of the arm drive.
Although there is a trade-off in the
sprint technique, such reduction in un-
resisted speed should be viewed as
a strength-speed exercise. Lighter
loads that cause less of a reduction in
speed (,35%) could be viewed as
speed-strength exercises given the
higher velocities achieved. Practi-
tioners and coaches should prescribe
horizontal strength training loads
based on an individual’s chosen
sporting demands; if arm drive is
thought important, then sled pulling
offers obvious advantages to the ath-
lete. For example, if a track coach has
limited time with a sprinter, they may
be able to use their time more effi-
ciently by incorporating heavy sled
pulling for lower-body force applica-
tion while still working on the athletes’
arm drive as a technical acquisition
practice. More in-depth kinematic
and kinetic analysis is needed to draw
conclusive comparisons between pull-
ing and pushing.
Earlier research investigating resisted
sled pulling used lighter resistances,
quantified by %BM (;13%) or % dec-
rement in max velocity (Vdec) (;10%)
(1,25,46). It was advised to avoid loads
heavier than those recommended in
the research, due to a concern of lon-
gitudinal interference with sprint kine-
matics and kinetics. Nevertheless, this
theory of negative adaptations from
using heavier loading protocols has
never been demonstrated. Intuitively,
it does not make sense to assume the
few minutes a week athletes spend re-
sisted sled pulling will negatively influ-
ence the sprint technique given the
amount of time they will also spend
in unresisted running. Kawamori et al.
(21) and Cottle et al. (8) have found
sled pulls of 30% BM and 20% BM
led to a significant acute increase in
horizontal impulses and propulsive
GRF, respectively, compared with
both unresisted and 10% BM loading.
Newtonian mechanics dictates that
heavier resistive loads will require
greater propulsive impulses (force 3
time) to overcome the additional load.
The increase in propulsive impulses is
largely due to prolonged contact time
and propulsive duration resulting in
increased requirements of force magni-
tude. Resisted sprint training at heavy
loads should be viewed as an exercise
to increase horizontal force production
through overload rather than a techni-
cal sprint exercise. One could assume
that the degradation in acute sprint
technique as a product of loading dur-
ing resisted sprinting at heavy loads
Sled Pushing and Pulling
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Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
may be the stimuli needed to produce
targeted adaptation in horizontal force
production. However, more research is
needed examining the kinematic effects
heavy-resisted sled sprint training has
longitudinally on the technical execu-
tion of sprinting. More recently, PAP
has been studied in both sled pulling
and pushing conditions (49,56,58,59).
Contrasting evidence has been re-
ported between PAP sled pulling stud-
ies, Whelan et al. (56) reported no
significant effect over 10 m, whereas
Wong et al. (59) reported a potentiating
effect over 0–5 m (1.13 60.08 seconds
versus 1.08 60.08 seconds). Both
studies examined the potentiating
effect of 30% BM during the accelera-
tion phase of a sprint at rest intervals
between 1-10 minutes and 2–
12 minutes, respectively. PAP has been
studied at much heavier loads; a recent
study by Seitz et al. (49) found 20-m
sprint performance is potentiated 4–
12 minutes after a sled push of 75%
BM but found it impaired at 125% BM.
As direct comparisons cannot be made
between sled pushing and pulling and
their effects on sprint performance
potentiation, one would assume that
heavier sled pulling loads need to be
Only 2 studies have examined the
kinetic effects of a longitudinal training
intervention with loads greater than
20% BM (20,36). Morin et al. (36)
and Kawamori et al. (20) both found
a larger decrease in sprint times when
using heavier loads (43–80% BM) com-
pared with a lighter load (13% BM) or
unresisted sprinting. Interestingly, Ka-
wamori et al. (20) found no significant
change in horizontal impulses across
loading groups. Improvement in speed
with a heavy load was attributed to the
athletes learning to direct GRF impulse
in a more horizontal direction rather
than expressing larger horizontal
GRF impulses. Conversely, research
by Morin et al. (36) reported increased
horizontal force production after
a heavy sled pull intervention.
In a systematic review of 11 studies,
Petrakos et al. (42) found no evidence
that resisted sprint training with loads
up to 43% BM or 30% Vdec was det-
rimental to sprint acceleration or
maximal velocity. They reported dif-
ferential training effects depending on
training status, with resisted sled
loads of 10–43% BM or 10–30% Vdec
improving acceleration performance
in untrained subjects. However,
whether these benefits were superior
to unresisted sprint training for
improved accelerative ability was
questionable. In strength-trained and
team sport athletes, it was thought
that slightly heavier loads (;20–43%
BM) were beneficial for improved
acceleration; however, once more the
benefits over and above unresisted
sprint training were not clear. The
general recommendation made by
Petrakos et al. (42) was that effective
sled sprint training blocks should last
for $6 weeks and include 2–3 sessions
per week of 5–35 m sprints, totaling
60–340 m per session. Given the
increasingly progressive nature of
loading with resisted sled sprinting
research in recent years, more
research is needed with loads that
exceed the parameters recommended
in the review by Petrakos et al. (42).
An interesting contention of Petrakos
et al. (42) was that acceleration and
maximum velocity adaptation was
a function of sled load. Heavier-type
sled load training likely improved the
initial acceleration phase where high
horizontal forces are required, whereas
light to moderate loading (,20% BM)
will likely improve the maximal veloc-
ity phase due to low horizontal force
and higher velocity requirements. It
was suggested that sled-training load
should be based on the training goal
(acceleration or maximal velocity),
whether the athletes were in
a strength/power phase, and/or the
individual force-velocity requirements
of the athlete. The load an athlete
pushes or pulls during resisted sled
training should vary and be considered
in an annual periodized plan to reflect
specific training goals. Heavier loads
could be used in preseason phases
developing maximum strength capac-
ity and moderate to lighter loads closer
to competition to develop power.
Whether these contentions are the
case and such approaches produce
the desired kinematic and kinetic adap-
tation requires further longitudinal
The acute and chronic responses to
sled training are likely to be depen-
dent on the physical characteristics
of an athlete, and practitioners must
consider how an athlete’s attributes
will influence their ability to perform
a resisted sprint. Slightly heavier rel-
ative loads may be required to
improve the acceleration of athletes
when compared with untrained indi-
viduals (42). When loading sprint and
jump athletes with 16% BM during
a sled pull, Alcaraz et al. (1) reported
that female athletes slowed more than
the male athletes (14 versus 12%);
although the difference was not sta-
tistically tested, the sex differences
can be estimated to be moderate in
magnitude. This difference between
the sexes will partly reflect differences
in body composition; a resistance that
is relative to total BM rather than lean
mass will disadvantage females due to
their greater levels of body fat. Rumpf
et al. (45) reported that for the same
relative loads during a sled pull, pre-
pubertal boys were slowed by 50%
more than postpubertal boys. The
article that although 6 weeks of sled
training improved the speed, stride
length, stride frequency, force, and
power in pubertal boys, it had no ben-
efit for prepubertal boys (46). It is not
clear whether these different acute
and chronic responses are solely
a result of maturation, differences in
the size, strength or training history of
youth, or most likely a combination of
these factors. What is clear is that the
characteristics of an athlete influence
both the acute and chronic responses
to sled pulling, and therefore, we
would expect the same for sled push-
ing. The available research suggests
that maturity, sex, and training his-
tory are all likely to influence the
Strength and Conditioning Journal | 7
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
ability of an athlete to sprint against
resistance, and this may be under-
pinned by differences in size, relative
strength, and body composition (29).
Although the practitioner should not
assume that the same load as a %BM
will produce the same stimulus in
a push and pull, it should also not
be assumed that the same %BM load
will produce the same stimulus for
athletes of differing characteristics.
extent to which velocity is decreased
rather than a set percentage of BM.
Individual athletes will respond to
loading differently. Reductions in
speed with load will also be influ-
enced by the sled design and friction
with any given surface. Although it is
difficult to understand exactly how
each of these factors influences per-
formance, an approach that pre-
scribes resisted training based on
a given reduction in speed (e.g., 50%
reduction in speed), rather than a set
percentage of body load, should be
better able to provide a consistent
stimulus between athletes and
There are a number of devices that
can be used to time sprints such as
photocell-timing gates, radar/laser,
video, and global positioning units
(39). As with all methods of assess-
ment, each has its own limitations,
including cost, complexity of set-up,
analysis, and reliability. Recent advan-
ces in technology, specifically high-
quality handheld cameras have paved
the way for mobile applications such
as My Sprint app to assess sprint per-
formance based on the research by
Samozino et al. (48). Recent research
a valid and reliable method to evalu-
ate sprint performance, although the
time required to analyze each athlete
can prove time-consuming in a team
setting compared with the use of tim-
ing gates or radar gun. Such methods
can also be used to determine the
loadspeed relationship during re-
sisted sprints. Assessing the load-
speed relationship for individual ath-
letes can provide coaches with valu-
able feedback for monitoring
performance changes and assessing
loading parameters over resisted
sprint training blocks, for instance to
ensure the load used during training
decreases velocity by a desired
amount (e.g., 50%). Coaches can also
observe the individual differences cer-
tain loads have on an athlete’s body
angle to ensure the desired training
This form of profiling an athlete dur-
ing resisted sprinting for load pre-
scription is less common. Alcaraz
et al. (2) developed a regression equa-
tion to optimize sled load in accor-
dance with keeping the athlete’s
maximal velocity above 90% using
a radar gun to assess instantaneous
velocity. Martinez-Valencia et al. (30)
and Petrakos et al. (43) examined the
maximum resisted sled load where an
athlete can no longer accelerate
between 10–15 m and 15–20 m of
a 20-m linear sprint using photocell-
timing gates. Both studies did not
exceed 30% BM during loading. More
recently, sprint time has been used to
construct force-velocity profiles dur-
ing unresisted sprinting (48), and that
process has also been applied to sled
pulling (13). The advantage of this
approach is that it allows for determi-
nation of the load and velocity com-
bination that optimizes power
production. Cross et al. (13) assessed
pulling loads between 20 and 120% of
BM. The authors found that the load
to optimize power for recreational
and elite-level sprinters ranged
between 69 and 96% of BM depen-
dent on the individual, but more
importantly load was optimized at
a decrement in velocity of 48–52%
for all athletes. Although %BM has
its limitations for load prescription,
it can give useful general guidelines
to coaches with time constraints and
limited resources. However, simple
measurement of the load-velocity
relationship can allow coaches to
individualize loading to a specific
velocity decrement and provide
Coaches and practitioners should
take note of the heavier loading pa-
rameters found by researchers to opti-
mize power production when
planning sled pushing and pulling
During sled pulling, the load-speed
relationship has been shown to be
linear with power optimized at
a Vdec of 50% (13). Although no
Figure 4. Individual load-speed relationships of 2 different athletes’ sled pushing
expressed as %BM. %BM 5percent body mass.
Sled Pushing and Pulling
VOLUME 00 | NUMBER 00 | MONTH 2019
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
one has specifically examined power
production during sled pushing, the
load-speed relationship has been
shown to be linear (55). Therefore,
it may be assumed that a parabolic
power relationship would also occur
with power optimized during push-
ing at a load that reduces velocity by
50%. Figure 4 illustrates 2 different
athlete load-velocity profiles during
resisted sled pushing; from our anec-
dotal evidence, it is apparent that the
same linear relationship exists.
Applying the principles reported by
Cross et al. (13), practitioners can
measure the load-speed relationship
for each athlete across a range of
loads and use this to identify the load
that decreases speed by 50% and op-
timizes power; this zone is illustrated
in yellow in Figure 4. In the example
causes 50% decrease in velocity is
75% BM for the athlete A and 55%
BM for athlete B. From this informa-
tion, heavier or lighter loads can be
prescribed based on the individual
characteristics (i.e., force or velocity
dominant) and the training goal. It is
important to note that the load that
optimizes power may not necessarily
be the optimal load that leads to in-
creases in sprint performance. Load
prescription may differ dependent on
the individual, for example, force
dominant athletes may benefit from
higher velocity training and vice ver-
sa. A certain baseline level of strength
(both horizontally and vertically)
may need to be established before
an athlete can truly use loads that
optimize power. Heavier loads that
cause a greater reduction in unre-
sisted speed (.65%) could be viewed
as strength-speed exercises; this zone
is illustrated in red in Figure 4. Ligh-
ter loads that cause less of a reduction
in unresisted speed (,35%) could be
viewed as speed-strength exercises;
this zone is illustrated in green. The
load that causes a reduction of 10% in
maximum velocity has been shown
not to effect sprint mechanics; this
zone is illustrated in blue and could
be used by coaches wishing to add
a loading stimulus without effecting
sprint mechanics.
This type of analysis can offer diag-
nostic information that both inform
adaptation and guide programming,
for example, coaches, practitioners,
and researchers can use such an
approach to make informed deci-
sions on loads prescribed during
training to ensure the desired adap-
tation is achieved. After further anal-
ysis of pre- and post-testing, this
approach can provide insight into
how different forms of resisted sled
training at a given load can alter the
force-velocity profile overtime.
There is renewed interest in the utility
of resisted sled sprinting methods to
improve speed ability, given the evo-
lution of knowledge around load
(heavy sled work), technique (sled
push), and assessment. However, we
have also stressed to the reader that
there are a number of limitations that
the reader should be cognizant of
when making sense of the application
of research to practice. Practitioners
should consider the following when
prescribing resisted sled pulling and
Resisted sled sprinting provides
a stimulus for high horizontal force
application, and when incorporated
into a strength training program, it
might prove to be a more effective
way of improving sprint perfor-
mance compared with unresisted
sprinting or traditional resistance
training alone.
Athlete characteristics, type of sled,
and type of surface will all influence
the amount of resistance experi-
enced. To help account for this, load-
ing should be prescribed on the
percentage reduction in velocity for
each athlete rather than a set per-
centage of BM.
Reductions in velocity of ,10, ,35,
50, and .65% during resisted sprinting
are suggested to reflect high-speed
(technical), speed-strength, power,
and strength-speed stimuli.
Conflicts of Interest and Source of Funding:
The authors report no conflicts of interest
and no source of funding.
Cahill is a doc-
toral candidate
at Auckland
University of
Technology and
the vice president
of Performance
and Sports Sci-
ence at Athlete Training and Health.
John B. Cronin
is a professor in
Strength and
Conditioning at
AUT University,
Sports Perfor-
mance Research
Institute New
Jon L. Oliver is
a reader in
Applied Paediat-
ric Exercise Sci-
ence and a co-
founder and
research lead of
the Youth
Centre at Cardiff Metropolitan
Kenneth P.
Clark is an assis-
tant professor in
the Department
of Kinesiology at
West Chester
University of PA.
Strength and Conditioning Journal | 9
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
Rhodri S. Lloyd
is a reader in
Strength and
Conditioning and
the chair and co-
founder of the
Youth Physical Development Centre at
Cardiff Metropolitan University.
Matt R. Cross is
a doctoral candi-
date at the Uni-
Mont Blanc with
the Fe
Franc¸aise de Ski
and a research
associate at the Auckland University of
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Strength and Conditioning Journal | 11
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... Resisted sprints using weighted sleds is a sprint-specific training method to improve performance during the acceleration phase [19,20]. It is reported that during sled towing, an acute improvement in force application occurs, and mechanical effectiveness is enhanced as the load increases [21]. ...
... Sprint kinematics, including the step length and frequency and the flight and contact time, determine the development of the velocity during sprinting [10]. Studies indicated that during sled towing, velocity is impaired due to the reduction of step length, step frequency and flight time and the increase of contact time [19,31]. Nevertheless, sled towing training for 6 weeks enhanced sprint velocity, mainly by increasing the step length [10]. ...
... In testing sessions, 5 min after performing a standardized warm-up [33], participants performed a baseline 30 m sprint from a three-point crouching position followed by the execution of an intervention condition. In EXP, 5 min after the baseline trial, 2 repetitions of 20 m resisted sprints with individualized load were completed with 2 min of recovery between the sprints [19,27,29]. A sled sprint distance of 20 m for the EXP condition was used to standardize the time under a tension of~5 s in order to maintain the maximum horizontal power [32]. ...
Full-text available
The aim of this study was to investigate the effects of heavy sled towing using a load corresponding to a 50% reduction of the individual theoretical maximal velocity (ranged 57–73% body mass) on subsequent 30 m sprint performance, velocity, mechanical variables (theoretical maximal horizontal force, theoretical maximal horizontal velocity, maximal mechanical power output, slope of the linear force–velocity relationship, maximal ratio of horizontal to total force and decrease in the ratio of horizontal to total force) and kinematics (step length and rate, contact and flight time). Twelve (n = 5 males and n = 7 females) junior running sprinters performed an exercise under two intervention conditions in random order. The experimental condition (EXP) consisted of two repetitions of 20 m resisted sprints, while in the control condition (CON), an active recovery was performed. Before (baseline) and after (post) the interventions, the 30 m sprint tests were analyzed. Participants showed faster 30 m sprint times following sled towing (p = 0.005). Running velocity was significantly higher in EXP at 5–10 m (p = 0.032), 10–15 m (p = 0.006), 15–20 m (p = 0.004), 20–25 m (p = 0.015) and 25–30 m (p = 0.014). No significant changes in sprint mechanical variables and kinematics were observed. Heavy sled towing appeared to be an effective post-activation potentiation stimulus to acutely enhance sprint acceleration performance with no effect on the athlete’s running technique.
... However, the adaptations from resisted sprint training interventions are likely to be a function of the load of the sled [101]. Traditionally, most resisted sprint training research has studied lighter loads of < 43% BM [94], though more recent research has begun to study heavier sled loads in excess of 80 % BM [20]. ...
... Research investigating sprint performance is often divided into acceleration and maximal velocity phases as they have distinct biomechanical determinants [33,71] which subsequently require different training methods to improve performance [84,95,101,111]. However, the traditional assessment of sprint performance in AF only assesses the acceleration phase of sprinting over 20 m and ignores the maximum velocity capacities of athletes [17]. ...
... Further, changes in sprint performance (sprint time) after a heavy sled pushing and pulling training intervention were reflected in changes in sprint FVP profiles suggesting the adaptations are specific to the training stimulus employed [101]. These exercises may be particularly suitable for youth athletes as they are less complex than traditional barbell exercises and can be performed with heavier load. ...
Full-text available
This thesis is based on a series of publications that were conducted with the aim of improving the assessment and development of sprint performance in junior AF players. Specifically, the objectives of the thesis were to examine the underlying FVP characteristics of maximum sprint performance through cross-sectional analysis across competition levels, maturation status, and draft outcome. Additionally, a longitudinal analysis explored the natural development of sprint performance and the influence of biological maturation. Finally, a longitudinal training intervention examined the effect of a sprint-specific training mesocycle on sprint performance and FVP characteristics. The specific aims of the thesis were to: 1. To establish the diagnostic ability of sprint times and sprint kinetic and kinematic characteristics in junior AF players. 2. Cross-sectionally explore the differences in sprint performance and sprint kinetics and kinematics in junior AF players through competition levels within the AFL player development pathway. 3. Longitudinally examine the natural development and influence of biological maturation on sprint performance and sprint kinetics and kinematics in junior AF players. 4. To assess the effectiveness of a sprint-specific training mesocycle on sprint performance and sprint kinetics and kinematics in junior AF players.
... From a kinematic perspective, a traditional definition might lend itself towards a loads that create a perceivable change in acute running form when compared to unresisted sprinting (e.g., increased leaning due to the sled harness, or stepping more behind center of mass etc.). While the conceptual comparison between resisted and unresisted sprinting, and associated underlying methodology, are debated in in recent literature (Cahill, Cronin, et al., 2019), the threshold delineating heavy and light loads arguably exists around a velocity loss (VL) of more than 10% (Alcaraz et al., 2008(Alcaraz et al., , 2019Alcaraz, Elvira and Palao, 2014). Contrastingly, from a mechanical perspective, loads of up to 50% VL exist toward the 'velocity' end of the horizontal FV , and accordingly could be classified as 'light' or velocity dominant loads relationship (i.e., target force production at high velocities, and late acceleration phases) (Cahill, Cronin, et al., 2019). ...
... While the conceptual comparison between resisted and unresisted sprinting, and associated underlying methodology, are debated in in recent literature (Cahill, Cronin, et al., 2019), the threshold delineating heavy and light loads arguably exists around a velocity loss (VL) of more than 10% (Alcaraz et al., 2008(Alcaraz et al., , 2019Alcaraz, Elvira and Palao, 2014). Contrastingly, from a mechanical perspective, loads of up to 50% VL exist toward the 'velocity' end of the horizontal FV , and accordingly could be classified as 'light' or velocity dominant loads relationship (i.e., target force production at high velocities, and late acceleration phases) (Cahill, Cronin, et al., 2019). ...
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Despite efforts to intervene, hamstring muscle injuries (HMI) continue to be one of the largest epidemiological burdens in professional football. The injury mechanism takes place dominantly during sprinting, but also other scenarios have been observed, such as overstretching actions, jumps, and change of directions. The main biomechanical roles of the hamstring muscles are functioning as an accelerator of center-of-mass (i.e., contributing to horizontal force production), and stabilizing the pelvis and knee joint. Multiple extrinsic and intrinsic risk factors have been identified, portraying the multifactorial nature of the HMI. Furthermore, these risk factors can vary substantially between players, portraying the importance of individualized approaches. However, there is a lack of multifactorial and individualized approaches assessed for validity in literature. Thus, the overarching aim of this doctoral thesis was to explore if a specific multifactorial and individualized approach can improve upon the ongoing HMI risk reduction protocols, and thus, further reduce the HMI risk in professional football players. This was done following the Team-sport Injury Prevention model (TIP model), where the target is to evaluate the current injury burden, identify possible solutions, and intervene. The thesis comprised of three themes within professional football, I) evaluating and identifying HMI risk (completed via assessing the current epidemiological HMI situation and the association between HMI injuries and a novel hamstring screening protocol), II) improving horizontal force capacity (completed via testing if maximal theoretical horizontal force (F0) can be improved via heavy resisted sprint training), and III) developing and conducting a multifactorial and individualized training for HMI risk reduction (completed via introducing and conducting a training intervention). The conclusions from theme I were that the HMI burden continues to be high (14.1 days absent per 1000 hours of football exposure), no tests from the screening protocol were associated with an increased HMI risk when including all injuries from the season (n = 17, p > 0.05), and that lower F0 was significantly associated with increased HMI risk when including injuries between test rounds one and two (~90 days, n =14, hazard ratio: 4.02 (CI95% 1.08 to 15.0), p = 0.04). For theme II, the players initial pre-season level of F0 was significantly associated with adaptation potential after 11 weeks of heavy resisted sprint training during the pre-season (r = -0.59, p < 0.05). The heavy resisted sprint load leading to a ~50% velocity loss induced the largest improvements in sprint mechanical output and sprint performance variables. For theme III, no intervention results could be presented within this document due to the Covid-19 pandemic leading to the intervention being postponed. However, a protocol paper was published, describing in detail the intervention approach that will be used outside the scope of the thesis. In future studies, larger sample size studies are needed to support the development of more advanced HMI risk reduction models. Such models may allow practitioners to identify risk on an individual level instead of a group level. Furthermore, constant development of more specific, reliable, and accessible risk assessment tests should be promoted that can be frequently tested throughout the football season. Finally, based on the results of theme II, individualization of a specific training stimulus should be promoted in team settings.
... Sprint training, specifically inclined sprint training, was found to have the largest per session training effect. This could be attributed to the fact that inclined or resisted sprint training methods have been found to be particularly effective for enhancing accelerative capability (Cahill et al., 2019;Okudaira et al., 2021). Given the large linear sprinting component and the limited number of changes of direction associated with the proagility shuttle, this makes sense since athletes are required to accelerate between each COD (Brughelli et al., 2008). ...
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Effective directional change in sport is imperative to success in key game situations. Change of direction (COD) ability is underpinned by various athletic qualities which can be developed through specific and non-specific training methods. This review examined the effect of specific and non-specific training methods on pro-agility performance, by analysing the intervention type and resulting magnitude of training effects on pro-agility shuttle performance. A total of 20 studies were included for review. Data from 638 subjects and 29 intervention groups involving seven different training methods were extracted and analysed in relation to training method classification and primary outcome measures. Interventions involving sprint training, plyometric training, resistance training, and combined resistance, plyometric, and sprint training were found to produce statistically significant positive change on pro-agility performance per session (p < 0.05). Sprint training (0.108 ES), plyometric training (0.092 ES), resistance training (0.087 ES), and combined resistance, plyometric, and sprint training (0.078 ES) methods were found to have the highest per session training effect. While total time is the typical unit of measure for this test, different types of training may lead to preferential improvements in either acceleration, deceleration, or COD phases of the pro-agility shuttle. Specifically, resisted or inclined sprinting may develop the linear acceleration phases, unilateral resistance training may promote increased strength to overcome the imposed forces during the deceleration and COD phases, multiplanar plyometrics can help enhance stretch-shortening cycle capabilities across different force vectors, and a combination of two or more of these methods may enable simultaneous development of each of these qualities.
... As players perform frequent short-distance sprints during match play, horizontal acceleration ability is often regarded as the most critical skill for RIMD sport athletes [3,4]. Accordingly, prior research has extensively examined the biomechanical and neuromuscular qualities underpinning superior horizontal acceleration ability in RIMD sport athletes [5][6][7][8][9][10][11][12][13], culminating in numerous evidence-informed guidelines on how to best monitor, train and coach this skill [4,[14][15][16][17][18][19]. ...
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Rapid horizontal accelerations and decelerations are crucial events enabling the changes of velocity and direction integral to sports involving random intermittent multi-directional movements. However, relative to horizontal acceleration, there have been considerably fewer scientific investigations into the biomechanical and neuromuscular demands of horizontal deceleration and the qualities underpinning horizontal deceleration performance. Accordingly, the aims of this review article are to: (1) conduct an evidence-based review of the biomechanical demands of horizontal deceleration and (2) identify biomechanical and neuromuscular performance determinants of horizontal deceleration, with the aim of outlining relevant performance implications for random intermittent multi-directional sports. We highlight that horizontal decelerations have a unique ground reaction force profile, characterised by high-impact peak forces and loading rates. The highest magnitude of these forces occurs during the early stance phase (< 50 ms) and is shown to be up to 2.7 times greater than those seen during the first steps of a maximal horizontal acceleration. As such, inability for either limb to tolerate these forces may result in a diminished ability to brake, subsequently reducing deceleration capacity, and increasing vulnerability to excessive forces that could heighten injury risk and severity of muscle damage. Two factors are highlighted as especially important for enhancing horizontal deceleration ability: (1) braking force control and (2) braking force attenuation. Whilst various eccentric strength qualities have been reported to be important for achieving these purposes, the potential importance of concentric, isometric and reactive strength, in addition to an enhanced technical ability to apply braking force is also highlighted. Last, the review provides recommended research directions to enhance future understanding of horizontal deceleration ability.
... Regarding the methods commonly used to prescribe ST loads to enhance sprint performance, a brief summary is provided in Table 2. Concerning loading conditions, some conflicting classifications can be found in the literature. For example, sled loads reducing sprint velocity by 25 and 75% have recently been suggested to represent light and heavy loads that target speed-strength and strength-speed qualities within the force-velocity spectrum, respectively (15). A recent study described loads of 45, 90, and 135% of BM as light, moderate, and heavy sled loads, with progressive V dec of 25, 50, and 75%, respectively (16). ...
Sprinting is a key component for many individual and team sports. Therefore, to enhance sprint performance, various training methods are widely used by coaches and practitioners, including maximum sprint speed and resisted sprint training. Resisted sprinting with sled towing is a method that has recently received considerable attention from the sport science community. However, to date, no consensus exists regarding its acute and chronic effects in team sport athletes. This narrative review aimed to (a) review and analyze the mechanics of sprinting under unresisted and resisted conditions with a specific focus on team sport disciplines; (b) provide a thorough and applied discussion on the importance of considering acute and chronic effects of sled loading on technique, electromyographic activity, and force production, as well as on the role of muscle architecture and neural factors in sled training; (c) analyze the effects of increasing sled loads during acceleration and maximum velocity phases on contact and flight phases, while concomitantly examining kinetic, kinematic, and neuromuscular aspects, because all these factors affect each other and cannot be properly understood in isolation.
... Sled pushing step characteristics as a function of distance demonstrated a decrease in SL, SF and FT, and increase in GCT as a result of the external load created by the sled and the bent over postures required to push the sled. These findings align with other studies examining the effects of external resistance (15-30% of body weight) on sprinting performance [28,[30][31][32] but such studies only considered the overall differences between sprinting with and without external resistance and did not examine how step characteristics between the two activities align as a function of step velocity. Comparison of GCT and FT as a function of step velocity revealed similar results between pushing and sprinting (Fig 2) despite the clear differences in the constraints of these movements. ...
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This study describes the development, evaluation and application of a computer vision and deep learning system capable of capturing sprinting and skeleton push start step characteristics and mass centre velocities (sled and athlete). Movement data were captured concurrently by a marker-based motion capture system and a custom markerless system. High levels of agreement were found between systems, particularly for spatial based variables (step length error 0.001 ± 0.012 m) while errors for temporal variables (ground contact time and flight time) were on average within ± 1.5 frames of the criterion measures. Comparisons of sprinting and pushing revealed decreased mass centre velocities as a result of pushing the sled but step characteristics were comparable to sprinting when aligned as a function of step velocity. There were large asymmetries between the inside and outside leg during pushing (e.g. 0.22 m mean step length asymmetry) which were not present during sprinting (0.01 m step length asymmetry). The observed asymmetries suggested that force production capabilities during ground contact were compromised for the outside leg. The computer vision based methods tested in this research provide a viable alternative to marker-based motion capture systems. Furthermore, they can be deployed into challenging, real world environments to non-invasively capture data where traditional approaches are infeasible.
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Introduction: This exploratory study aimed to assess the relationship between athlete neuromuscular performance and rugby performance indicators. Specifically, the study looked at the force-velocity profiles (FVPs) derived from four common resistance exercises and their relationship with rugby performance indicators (RPIs). Methods: The study recruited twenty-two semi-professional male rugby players (body mass 102.5 ± 12.6 kg, height 1.85 ± 0.74 m, age 24.4 ± 3.4 years) consisting of ten backs and twelve forwards. Prior to the first game of a Covid-impacted nine-match season, participants performed four common resistance exercises (barbell box squat, jammer push-press, sled pull, and sled push) at incremental loads to establish force-velocity profiles. During the season, rugby performance indicators (post-contact metres, tries, turnovers conceded, tackles, try assists, metres ran, defenders beaten, and tackle breaks) were collated from two trusted sources by a performance analyst. Correlational analyses were used to determine the relationship between the results of FVPs and RPIs. Results: The study found a statistically significant, moderate, positive correlation between tackle-breaks and sled push V0 (r = .35, p = .048). Significant, large, positive correlations were also found between tackles and jammer push-press V0 (r = .53, p = .049) and tackle-breaks and sled pull F0 (r = .53, p = .03). There was a significant, negative relationship between sled pull V0 and tackle-breaks (r = −.49, p = .04). However, the largest, significant correlation reported was between metres ran and sled pull F0 (r = .66, p = .03). Conclusion: The study suggests that a relationship may exist between FVPs of particular exercises and RPIs, but further research is required to confirm this. Specifically, the results suggest that horizontal resistance training may be best to enhance RPIs (tackle-breaks, tackles, and metres ran). The study also found that maximal power was not related to any rugby performance indicator, which suggests that a specified prescription of either force or velocity dominant exercises to enhance RPIs may be warranted.
Leonie Schwertmann, Nike Lorenz, Timo Boll, Joshua Kimmich, Leon Draisaitl, Uwe Gensheimer oder Angelique Kerber gelingt es scheinbar mühelos, ungewöhnliche, aber auch technisch-taktische Bestlösungen auf dem Spielfeld zu generieren, ganz nach dem Motto: „Just do it!“ Nicht allen Sportlern, unabhängig von ihrem Leistungsniveau, gelingt es aber, optimale motorische Entscheidungshandlungen unter höchstem Zeit-, Präzisions-, Variabilitäts- Belastungs- und Gegnerdruck zu treffen. Hier stellt sich für viele Lehrer und Trainer die Aufgabe, Fehlerquellen angemessen zu analysieren, sie vergleichend zu diagnostizieren und sie abschließend effektiv durch Training zu beheben.
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Horizontal accelerations and decelerations are crucial components underpinning the many fast changes of speed and direction that are performed in team sports competitive match play. Extensive research has been conducted into the assessment of horizontal acceleration and the underpinning neuromuscular performance determinants, leading to evidence-informed guidelines on how to best develop specific components of a team sport players horizontal acceleration capabilities. Unlike horizontal acceleration, little scientific research has been conducted into how to assess horizontal deceleration, meaning the neuromuscular performance determinants underpinning horizontal deceleration are largely based on anecdotal opinion or qualitative observations. Therefore, the overall purpose of this thesis was to investigate the neuromuscular determinants of maximal horizontal deceleration ability in team sport players. Furthermore, since there are no recognised procedures on how to assess maximal horizontal deceleration ability, an important and novel aim of this thesis was to develop a test capable of obtaining reliable and sensitive data on a team sport player’s maximal horizontal deceleration ability. In part one of this thesis (chapter three) a systematic review and meta-analysis identified that high-intensity (< -2.5 m.s-2) decelerations were more frequently performed than equivalently intense accelerations (> 2.5 m.s-2) in most elite team sports competitive match play, signifying the importance of developing maximal horizontal deceleration ability in team sport players. In chapter four, a new test of maximal horizontal deceleration ability (named the acceleration-deceleration ability test – ADA test), measured using radar technology, identified a number of kinematic and kinetic variables that had good intra- and inter-day reliability and were sensitive to detecting small-to-moderate changes in maximal horizontal deceleration ability. The ADA test was used in chapters five to seven to examine associations with isokinetic eccentric and concentric knee strength capacities and countermovement and drop jump kinetic and kinematic variables, respectively. Using the neuromuscular and biomechanical determinants identified to be important for horizontal deceleration ability within this thesis, in addition to other contemporary research findings, the final part of this thesis developed an evidence-based framework that could be used by practitioners to help inform decisions on training solutions for improving horizontal deceleration ability – named the dynamic braking performance framework.
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Resisted sled sprint (RSS) training is an effective modality for the improvement of linear sprint speed. Previous methods of RSS load prescription e.g. an absolute load or as a percentage of body mass (%BM), do not account for inter-individual differences in strength, power or speed characteristics, although the 'maximum resisted sled load' (MRSL) method of RSS load prescription may provide a solution. MRSL is defined as the final RSS load before an athlete can no longer accelerate between two phases (10-15 m and 15-20 m) of a 20 m linear sprint. However, the MRSL test has not been analysed for reliability. Additionally, MRSL performance has not been compared to the outcome of other performance tests. The primary aim of this study was to investigate the reliability of the MRSL testing protocol in female field sport athletes. Participants (age, 20.8 ± 1.9 y; body mass, 64.3 ± 8.4 kg; height, 1.66 ± 0.65 m) tested for anthropometric measurements, strength and power performance testing and twice for MRSL. MRSL values ranged from 20.7 to 58.9%BM. MRSL test-retest reliability intraclass correlation coefficient, confidence intervals and coefficient of variations were 0.95, 0.85-0.98 and 7.6%, respectively. MRSL was 'moderately' and 'strongly' correlated with a number of anthropometric and performance tests (p < 0.05) including % fat free mass, countermovement jump, loaded countermovement jump, rate of force development, horizontal jump and horizontal bound performance. MRSL is a reliable measure for determining the RSS load at which an individual can no longer accelerate during a single RSS effort over 0-20 m. MRSL also accounts for inter-individual variation in body composition, power and speed characteristics of female field sport players.
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Sled towing is a common form of overload training in sports to develop muscular strength for sprinting. This type of training leads to acute and chronic outcomes. Acute training potentially leads to postactivation potentiation (PAP), which is when subsequent muscle performance is enhanced following a preload stimulus. The purpose of this study was to determine differences between rest intervals following sled towing on acute sprint speed. Twenty healthy recreationally trained males (age= 22.3 ± 2.4yrs, height= 176.95 ± 5.46 cm, mass= 83.19 ± 11.31 kg) who were currently active in a field sport twice a week for the last six months volunteered to participate. A maximal 30 meter (m) baseline body mass (BM) sprint was performed (with splits at 5, 10, 20 and 30m) followed by 5 visits where participants sprinted 30m towing a sled at 30% BM then rested for 2, 4, 6, 8 or 12min. They were instructed to stand still during rest times. After the rest interval, they performed a maximal 30m post-test BM sprint. ANOVA revealed that post sled tow BM sprint times (4.47±0.21s) were less than baseline times (4.55±0.18s) on an individualized rest interval basis. A follow up 2x4 ANOVA showed that this decrease occurred only in the acceleration phase over the first 5m (BL=1.13±0.08s vs Best= 1.08±0.08s) which may be the result of PAP and the complex relationship between fatigue and potentiation relative to the intensity of the sled tow and the rest interval. Therefore, coaches should test their athletes on an individual basis to determine optimal rest time following a 30m 30% BM sled tow to enhance acute sprint speed.
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Sled-towing exercisesare effective at developing sprint acceleration in sports. In a sled-towingexercise the time taken by an athlete to tow the sled over a given distance isaffected by the weight of the sled, the frictional properties of the runningsurface, and the physiological capacities of the athlete. To accurately set thetraining intensity for an athlete, the coach needs a detailed understanding ofthe relationships between these factors. Our study investigated therelationship between the athlete's strength-to-weight ratioand the rate of increase in sled-towing time with increasing sled weight. Twenty-two male athletes performed aone-repetition maximum (1RM) half-squat and sled-towing exercises over 20 mwith sleds of various weights. The strength of the correlation between 1RM half-squat performance (normalized to bodyweight)and the rate of increase in sled-towing time with increasing sled weight was interpreted using the Pearson product-moment correlationcoefficient. As expected, we found substantialinter-athlete differences in the rate of increase in time with increasing sledweight, with a coefficient of variation of about 21% and 17% for sled-towingtimes over 10 and 20 m, respectively. However, the rate of increase in sled-towing time showed nocorrelation with normalized 1RM half-squat performance (r = -0.11, 90% confidence interval = -0.45 to 0.26; and r = -0.02, 90% confidence interval =-0.38 to 0.34, for sled-towing times over 10 and 20 m, respectively). Theseresults indicate thatinter-athlete differences in the rate of increase in sled-towingtime with increasing sled weight are not likely to be due to differences instrength-to-weight ratio. Instead,we recommend the weight of the sled be scaled according to the athlete'spower-to-weight ratio.
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Purpose: To ascertain whether force-velocity-power relationships could be compiled from a battery of sled-resisted overground sprints and to clarify and compare the optimal loading conditions for maximizing power production for different athlete cohorts. Methods: Recreational mixed-sport athletes (n = 12) and sprinters (n = 15) performed multiple trials of maximal sprints unloaded and towing a selection of sled masses (20-120% body mass [BM]). Velocity data were collected by sports radar, and kinetics at peak velocity were quantified using friction coefficients and aerodynamic drag. Individual force-velocity and power-velocity relationships were generated using linear and quadratic relationships, respectively. Mechanical and optimal loading variables were subsequently calculated and test-retest reliability assessed. Results: Individual force-velocity and power-velocity relationships were accurately fitted with regression models (R2> .977, P < .001) and were reliable (ES = 0.05-0.50, ICC = .73-.97, CV = 1.0-5.4%). The normal loading that maximized peak power was 78% ± 6% and 82% ± 8% of BM, representing a resistance of 3.37 and 3.62 N/kg at 4.19 ± 0.19 and 4.90 ± 0.18 m/s (recreational athletes and sprinters, respectively). Optimal force and normal load did not clearly differentiate between cohorts, although sprinters developed greater maximal power (17.2-26.5%, ES = 0.97-2.13, P < .02) at much greater velocities (16.9%, ES = 3.73, P < .001). Conclusions: Mechanical relationships can be accurately profiled using common sled-training equipment. Notably, the optimal loading conditions determined in this study (69-96% of BM, dependent on friction conditions) represent much greater resistance than current guidelines (~7-20% of BM). This method has potential value in quantifying individualized training parameters for optimized development of horizontal power.
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Understanding the impact of friction in sled sprinting allows the quantification of kinetic outputs and the effective loading experienced by the athlete. This study assessed changes in the coefficient of friction (µk) of a sled sprint-training device with changing mass and speed to provide a means of quantifying effective loading for athletes. A common sled equipped with a load cell was towed across an athletics track using a motorised winch under variable sled mass (33.1–99.6 kg) with constant speeds (0.1 and 0.3 m · s−1), and with constant sled mass (55.6 kg) and varying speeds (0.1–6.0 m · s−1). Mean force data were analysed, with five trials performed for each condition to assess the reliability of measures. Variables were determined as reliable (ICC > 0.99, CV < 4.3%), with normal-force/friction-force and speed/coefficient of friction relationships well fitted with linear (R2 = 0.994–0.995) and quadratic regressions (R2 = 0.999), respectively (P < 0.001). The linearity of composite friction values determined at two speeds, and the range in values from the quadratic fit (µk = 0.35–0.47) suggested µk and effective loading were dependent on instantaneous speed on athletics track surfaces. This research provides a proof-of-concept for the assessment of friction characteristics during sled towing, with a practical example of its application in determining effective loading and sled-sprinting kinetics. The results clarify effects of friction during sled sprinting and improve the accuracy of loading applications in practice and transparency of reporting in research.
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Background: Sprint running acceleration is a key feature of physical performance in team sports, and recent literature shows that the ability to generate large magnitudes of horizontal ground-reaction force and mechanical effectiveness of force application are paramount. The authors tested the hypothesis that very-heavy loaded sled sprint training would induce an improvement in horizontal-force production, via an increased effectiveness of application. Methods: Training-induced changes in sprint performance and mechanical outputs were computed using a field method based on velocity-time data, before and after an 8-wk protocol (16 sessions of 10- × 20-m sprints). Sixteen male amateur soccer players were assigned to either a very-heavy sled (80% body mass sled load) or a control group (unresisted sprints). Results: The main outcome of this pilot study is that very-heavy sled-resisted sprint training, using much greater loads than traditionally recommended, clearly increased maximal horizontal-force production compared with standard unloaded sprint training (effect size of 0.80 vs 0.20 for controls, unclear between-groups difference) and mechanical effectiveness (ie, more horizontally applied force; effect size of 0.95 vs -0.11, moderate between-groups difference). In addition, 5-m and 20-m sprint performance improvements were moderate and small for the very-heavy sled group and small and trivial for the control group, respectively. Practical Applications: This brief report highlights the usefulness of very-heavy sled (80% body mass) training, which may suggest value for practical improvement of mechanical effectiveness and maximal horizontal-force capabilities in soccer players and other team-sport athletes. Results: This study may encourage further research to confirm the usefulness of very-heavy sled in this context.
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The purpose of this study was to assess validity and reliability of sprint performance outcomes measured with an iPhone application (named: MySprint) and existing field methods (i.e. timing photocells and radar gun). To do this, 12 highly trained male sprinters performed 6 maximal 40-m sprints during a single session which were simultaneously timed using 7 pairs of timing photocells, a radar gun and a newly developed iPhone app based on high-speed video recording. Several split times as well as mechanical outputs computed from the model proposed by Samozino et al. [(2015). A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running. Scandinavian Journal of Medicine & Science in Sports.] were then measured by each system, and values were compared for validity and reliability purposes. First, there was an almost perfect correlation between the values of time for each split of the 40-m sprint measured with MySprint and the timing photocells (r=0.989–0.999, standard error of estimate=0.007–0.015 s, intraclass correlation coefficient (ICC)=1.0). Second, almost perfect associations were observed for the maximal theoretical horizontal force (F0), the maximal theoretical velocity (V0), the maximal power (Pmax) and the mechanical effectiveness (DRF – decrease in the ratio of force over acceleration) measured with the app and the radar gun (r= 0.974–0.999, ICC=0.987–1.00). Finally, when analysing the performance outputs of the six different sprints of each athlete, almost identical levels of reliability were observed as revealed by the coefficient of variation (MySprint: CV=0.027–0.14%; reference systems: CV=0.028–0.11%). Results on the present study showed that sprint performance can be evaluated in a valid and reliable way using a novel iPhone app.
Objectives: The objective of this study was to examine the potentiating effects of performing a single sprint-style sled push on subsequent unresisted 20m sprint performance. Design: Randomized crossover design. Methods: Following a familiarization session, twenty rugby league players performed maximal unresisted 20m sprints before and 15s, 4, 8 and 12min after a single sled push stimulus loaded with either 75 or 125% body mass. The two sled push conditions were performed in a randomized order over a one-week period. The fastest sprint time recorded before each sled push was compared to that recorded at each time point after to determine the post-activation potentiation (PAP) effect. Results: After the 75% body mass sled push, sprint time was 0.26±1.03% slower at the 15s time point (effect size [ES]=0.07) but faster at the 4 (-0.95±2.00%; ES=-0.22), 8 (-1.80±1.43%; ES=-0.42) and 12 (-1.54±1.54%; ES=-0.36)min time points. Sprint time was slower at all the time points after the 125% body mass sled (1.36±2.36%-2.59±2.90%; ESs=0.34-0.64). Conclusions: Twenty-meter sprint performance is potentiated 4-12min following a sled push loaded with 75% body mass while it is impaired after a 125% body mass sled. These results are of great importance for coaches seeking to potentiate sprint performance with the sled push exercise.