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Sport scientists and strength and conditioning coaches are showing growing interest in the magnitude, orientation, and application of ground reaction force during acceleration actions in sport, as it can identify the key mechanical determinants of performance. Horizontal force-velocity pro-filing or sprint profiling helps practitioners understand the capacity of the mechanical force production during the acceleration phase of a sprint. This review examines the methods used in the field for deter-mining horizontal force-velocity (sprint)profiles. It also includes recommendations for practical training methods to address individual force-velocity characteristics, mechanical effectiveness, thereby optimizing acceleration performance.
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Improving Mechanical
Effectiveness During
Sprint Acceleration:
Practical
Recommendations and
Guidelines
Dylan Shaun Hicks, MSc,
1
Jake George Schuster, MSc,
2
Pierre Samozino, PhD,
3
and Jean-Benoit Morin, PhD
4
1
Exercise Science Department, Flinders University, Adelaide, South Australia, Australia;
2
Vald Performance and Florida
State University Institute of Sports Science and Sports Medicine;
3
Univ Savoie Mont Blanc, Laboratoire
Interuniversitaire de Biologie de la Motricite
´, Chambe
´ry, France;
4
Universite
´Co
ˆte d’Azur, LAMHESS, Nice, France
ABSTRACT
Sport scientists and strength and
conditioning coaches are showing
growing interest in the magnitude,
orientation, and application of ground
reaction force during acceleration ac-
tions in sport, as it can identify the key
mechanical determinants of perfor-
mance. Horizontal force-velocity pro-
filing or sprint profiling helps
practitioners understand the capacity
of the mechanical force production
during the acceleration phase of
a sprint. This review examines the
methods used in the field for deter-
mining horizontal force-velocity (sprint)
profiles. It also includes recommenda-
tions for practical training methods to
address individual force-velocity char-
acteristics, mechanical effectiveness,
thereby optimizing acceleration per-
formance.
INTRODUCTION
Strength and conditioning coaches
are interested in understanding
the limitations in mechanical per-
formance during activities involving lin-
ear and multidirectional speed. High-
speed running (sprinting) is the funda-
mental component of many team sports
and involves 2 key phases: acceleration
and maximal velocity (7). The ability to
accelerate and reach the highest velocity
possible in the shortest period is under-
pinned by the mechanical components of
the neuromuscular system, force, velocity,
and power, and specifically the force-
velocity (F-v) profile (73). Within the
strength and conditioning literature,
methods to identify these mechanical
components during acceleration have
been limited, making it unclear the most
appropriate training prescription that
should be used to improve these qualities.
Therefore, if a resistance training pro-
gram is designed to enhance sprint accel-
eration, should strength and conditioning
coaches select exercises, which focus on
force, velocity, and power, or prioritize
onevariableovertheother?
During the stance phase of a sprint
action, a ground reaction force (GRF)
is produced, which includes both hor-
izontal and vertical components of the
GRF (referred to as horizontal and
vertical forces for simplicity), along
with the resultant GRF. The stance
or contact phase can be divided into
braking and propulsive phases in the
anteroposterior direction, followed by
a flight phase when the limbs are re-
positioned in the air before contacting
the ground again (58). This ongoing
exchange of kinematic positions de-
fines sprinting as a ballistic action
(58). In comparison with various track
and field events where only linear
speed is required, in team sports such
as Australian rules football and rugby,
jumping actions followed by a sprint
acceleration in multiple directions are
common. These constant changes in
velocity require athletes to accelerate
Address correspondence to Dylan Shaun
Hicks, dylan.hicks@flinders.edu.au.
KEY WORDS:
power; force; velocity; acceleration;
sprinting; resistance training
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Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
or decelerate their body mass (24,72)
and can include rapid changes in direc-
tion to chase down or evade an oppo-
nent. Although achieving maximal
velocity is important in many team
sports (33,39), the ability to accelerate
(and decelerate) can be of far greater
assistance to an athlete’s on-field per-
formance (4,27); therefore, coaches
must place a large emphasis on
improving this quality.
To accelerate in the horizontal direc-
tion in the shortest period, the athlete
has to develop the highest net hori-
zontal force possible, averaged across
each step during the sprint effort. An
individual’s ability to perform this task
are characteristics of both the mechan-
ical and neuromuscular systems (44),
however also influenced by the ath-
lete’s technical ability to apply the
force and the propulsive impulse (force
3time) produced by the athlete. The
constraints of applying force over
increasingly shorter periods of ground
contact as the athlete moves through
the sprint acceleration identify how
impulse can affect performance. Accel-
eration performance will be limited if
the impulse is high due to force pro-
duction occurring over a longer ground
contact time. Therefore, the ability to
achieve a high net external force
applied in the opposite direction to
the center of mass displacement, as
the running velocity increases, and
ground contact decreases, is of primary
concern. In many team sports, rapidly
changing one’s velocity and momen-
tum to evade opponents is crucial
(35); however, applying force in a more
horizontal direction is a major factor in
differentiating between rates of accel-
eration (13,40,60,61,66).
During the acceleration phase, the
ability to apply horizontally oriented
force has been shown to be one of
the key determining factors to per-
formance (61). This is in contrast to
maximal velocity running where
Weyand et al. (91) showed that the
magnitude of GRF production, ori-
ented vertically over the contact
phase, was the limiting factor to per-
formance. Effectively applying lower
limb force in a horizontal direction as
velocity increases has been referred
to as mechanical effectiveness (75).
This mechanical description is under-
pinned by the force applied by the
athlete across the acceleration effort
and describes the ratio of the net hor-
izontal component and resultant
GRF across the acceleration (61).
One “simple” macroscopic method
used to determine mechanical effec-
tiveness across a sprint acceleration is
horizontal F-v profiling, also known
as sprint profiling. Across a sprint
acceleration effort, sprint profiling
models the step-averaged mechanical
outputs (force, velocity, and power)
in the horizontal direction. This inno-
vative method provides a detailed
“roadmap” for understanding the
mechanical components underpin-
ning acceleration. As a means of
accurately assessing the horizontal
force produced by an athlete, sprint
profiling assists coaches to calculate
the degree of horizontally directed
force applied over any distance or
velocity across the sprint effort (62).
It also identifies the athlete’s mechan-
ical strengths and weaknesses when
accelerating, specifically their ability
to apply horizontal force and accel-
erate toward maximal velocity.
Sprint profiling helps coaches and ath-
letes understand the F-v and power-
velocity (P-v) relationships, along with
how horizontal force production
capacity changes across the accelera-
tion, and provides a global view of
the likely morphological and neuro-
muscular properties involved (21). Fur-
thermore, when attempting to
understand the mechanical variables
that contribute to acceleration perfor-
mance, it raises the question of
whether the conventional approach
of manually or electronically timing
a 40-yard sprint should be used in con-
junction with the more in-depth sprint
profiling. Moreover, can this informa-
tion be effectively used to individualize
a resistance training program to target
the mechanical strengths and weaknesses
of the athlete, thereby improving
performance? Additional details provided
by mechanical sprint profiling including
power and force orientation provide prac-
titioners with superior means to objec-
tively evaluate, effect, and monitor sprint
qualities.
Although sprinting is the most spe-
cific and highest velocity training
method used to improve an athlete’s
linear speed, strength and condition-
ing coaches will often look to other
resistance training methods to com-
pliment speed training. These meth-
ods are used to further elicit
adaptations to F-v characteristics
and to address various mechanical
qualities contributing to perfor-
mance. The selection of exercises to
improve physical performance in
a sport should be based on factors
that demonstrate the highest transfer
to that sport. Because horizontal and
vertical components of the GRF are
produced while accelerating, yet in
different magnitudes, there is often
conjecture on where the focus should
be placed from an exercise selection
perspective when producing force: in
the horizontal or vertical direction?
Two concepts, which will be dis-
cussed in this review regarding exer-
cise selection, are dynamic
correspondence (90) and the force-
vector theory. These concepts
describe that the biomechanics, force
production and orientation, and
velocity of training movements
should be similar to those used in
the athlete’s sport. Both concepts
provide a framework for exercise
selection. Yet, when selecting resis-
tance training exercises to improve
acceleration performance, should
strength and conditioning coaches
select exercises based on specificity
to the sprint action or maintain
a broad approach when attempting
to change F-v characteristics?
This review aims to provide back-
ground information on the F-v rela-
tionship, determinants and
biomechanics of acceleration perfor-
mance, and sprint profiling, as well as
discussing exercise selection and train-
ing programs for improving athletes’
mechanical effectiveness during
Mechanical Effectiveness during Sprint Acceleration
VOLUME 00 | NUMBER 00 | NOVEMBER 2019
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Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
acceleration. The practical recommen-
dations in this review could be used to
address F-v characteristics and hori-
zontal force application and devise
individualized training programs for
teams and individual sport athletes.
DETERMINANTS OF FORCE AND
VELOCITY
Mechanical variables such as force
and velocity play a vital role in bal-
listic activities such as sprinting and
determine overall neuromuscular
performance (75). However, these
variables are in a sense limiting given
that the force produced and the
shortening velocity of skeletal muscle
are constrained by morphological
factors such as fiber type, fascicle
length, pennation angle, and neural
mechanisms such as motor unit
recruitment and intramuscular coor-
dination (21). Each of these variables
has a direct effect on the ability of
skeletal muscle to exert maximal
power (P
MAX
). High-power outputs
are considered critical performance
characteristics for success and will
often differentiate between ability
levels in sport (84). Practitioners have
long argued that athletes should be
training at loads, which maximize
power (18,46,83,92); however, other
investigators have suggested that
loads, which are above and below
optimal load, develop P
MAX
to
a greater degree (37,52) warranting
further exploration to determine
whether an “optimal load” exists
and leads to comparatively greater
training-induced improvements. It
has been shown that ballistic activi-
ties are determined by the P
MAX
of
the lower limbs and impulse but are
also strongly influenced by the indi-
vidual’s F-v capabilities, which is also
known as the F-v profile (76). Train-
ing status and relative strength also
influence force expression, and there-
fore, evaluations of F-v profiles
should be highly standardized to
maximize reliability of data (38,43).
Understanding an athlete’s strengths
and weaknesses in terms of their
mechanical output assists a strength
and conditioning coach to devise an
appropriate training program based
on the specific needs of the athlete’s
F-v profile.
BIOMECHANICAL DETERMINANTS
OF SPRINT ACCELERATION
Newtonian laws show that sprint accel-
eration in a forward direction is deter-
mined by the horizontal and vertical
components of the resultant GRF, the
horizontal and vertical impulse, and the
displacement of the center of mass
(CoM) (64). Force and impulse are vec-
tor quantities, which include direction
and magnitude, and depend on the
phase of the sprint action, along with
the position of the athlete’s body. These
vectors are oriented either horizontally
(mainly anteroposterior) or vertically.
When starting from zero velocity, the
impulse will be a combination of force
applied over longer ground contacts, and
as velocity increases, the time in which
force can be applied reduces, therefore
making quality force application at
ground contact critical. Although net
horizontal force determines the rate of
acceleration (70,75), the impulse-
momentum relationship governs the
time in which force is applied; it has been
shown that this factor accounts for slow
or fast rates of acceleration, where
Figure 1. Changes in horizontal force and power as running velocity increases.
Figure 2. Mechanical output across a sprint acceleration effort. These variables
identify the current performance output of the athlete and the mechanical
limits of the neuromuscular system: theoretical maximal force (F
0
), theo-
retical maximal velocity (V
0
), and maximal power (P
MAX
) in the horizontal
direction.
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shorter contact times beget the need for
increased force expression. Hunter et al.
(40) identified in a series of 25-m sprints
that the greatest variance (61%) occurred
with the horizontal impulse measured at
the 16-m mark. Morin et al. (64) sup-
ported this view and the argument that
the fastest sprinters were able to produce
greater net horizontal impulse compared
with their subelite counterparts. Also, of
importance, it was shown that the faster
sprinters maintained this impulse across
the duration of the sprint acceleration as
velocity was increasing and ground con-
tact was decreasing. This was critical to
performance.
The way in which a GRF is oriented is
key to the acceleration performance or
maximal velocity achieved in sprinting
(6). Emphasis must be placed on max-
imizing and orienting horizontal (ante-
roposterior) force application during
acceleration because the speed runners
ultimately attain specifically correlates
with the magnitude of the propulsive
force (and time over which it is
applied) at the start of the effort, along
with the successive strides during
acceleration (12,78,94). It has been
shown that elite sprinters produce
higher net horizontal force and
impulse with each step at any given
velocity, which allows them to attain
higher velocities than their subelite
counterparts (60,61,70). Although the
orientation of force is superior in elite
sprinters, their training history and
kinematics mean that they are also
more effective at transferring force into
the ground. Such technical skills are
also derived from specific neuromuscu-
lar properties including the structural
integrity of the muscle and ten-
don (60,70).
The position of the athlete’s body
when sprinting, whether accelerating
or at maximal velocity, influences
application and orientation of force
(48). Positioning the overall body
(not only the trunk-head segments) in
an inclined position in relation to the
ground makes it possible to achieve
a more propulsive resultant GRF
(8,12,48). Whereas, when an athlete
is sprinting at maximal velocity in an
upright position, a greater reliance is
placed on achieving high GRF with
a vertical orientation to limit time spent
on the ground, thereby reducing decel-
eration (11,91). Directing the resultant
GRF in a more forward or horizontally
oriented direction is more important
during the acceleration phase of a sprint
compared with the overall magnitude
of force applied to the ground, and
therefore, this component is critical
to focus on during training
(13,60,61,70). Colyer et al. (13) showed
that sprinters, compared with soccer
players, exhibit more horizontally
directed force during the late braking
phase and early propulsive phase, al-
lowing them to accelerate to higher
velocities; this was a key difference
between athlete groups. Orientation
of force is also affected by the touch-
down or ground contact distance in
reference to the body CoM on ground
contact (7). During this contact in early
stance phase, maintaining a stiff ankle
increases the resultant GRF and
Figure 3. A representation of lower limb ratio of forces, net positive horizontal (F
H
)
divided by total force (F
TOT
, which includes the vertical component). The
forward orientation of the total GRF vector is represented by the angle a.
GRF 5ground reaction force.
Figure 4. Horizontal force-velocity-power profiles for 2 athletes. Both athletes display
similar maximal horizontal power outputs and sprint times, yet different
theoretical maximal force and velocity values (see slope).
Mechanical Effectiveness during Sprint Acceleration
VOLUME 00 | NUMBER 00 | NOVEMBER 2019
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momentum due to the impulse and
subsequent horizontal velocity
achieved (9). Therefore, assessing and
diagnosing the way in which athletes
apply horizontal force during accelera-
tion has important ramifications for at-
taining the best possible sporting
performance.
HORIZONTAL FORCE-VELOCITY
PROFILING
Horizontal F-v profiling (sprint profil-
ing) is an assessment and diagnostic
tool that examines the key character-
istics of F-v and P-v relationships in
sprint actions; its main focus is on the
acceleration phase (26,62). These rela-
tionships define the changes in
propulsive force and horizontal power
when running velocity increases (Fig-
ure 1) (62). Using a series of timing
gates or a radar device, as well as bio-
mechanical modeling derived from
speed-time data (75), it is possible to
calculate horizontal force, velocity, and
power as the athlete accelerates. This
information describes the current
mechanical output from the athlete,
along with the mechanical limits of
the neuromuscular system while accel-
erating. Limits include theoretical max-
imal horizontal force at null velocity
(F
0
), theoretical maximal horizontal
velocity until which force can be pro-
duced (V
0
), and the maximal power
produced in a horizontal direction
(P
MAX
) (Figure 2) (75). Over the dura-
tion of a sprint acceleration, Morin et al.
(61) use the term ratio of forces (RF)—
which describes the horizontal (ante-
roposterior) component of the GRF
(F
H
) vector as a percentage of the total
GRF (F
TOT
) vector (Figure 3). This
ratio identifies the technical ability an
athlete may or may not possess to ori-
ent force horizontally while accelerat-
ing. Because orientation of the force is
more important than its magnitude,
understanding the force ratio is critical.
From these data, the mechanical effec-
tiveness of applying force (RF% 5F
H
/
F
TOT
) at each step can be determined.
The higher the RF%, the more hori-
zontal orientation of the GRF has been
achieved. Mechanical effectiveness is
important for determining the athlete’s
ratio of decreases in force (D
RF
) with
increasing velocity (62), which de-
scribes how force orientation changes
from more horizontal to vertical. Mor-
in et al. (61) state that even if F
TOT
is
similar in 2 athletes, the RF% can iden-
tify mechanical differences including
weaknesses, which can then be tar-
geted with training interventions.
Quantifying individuals’ mechanical
effectiveness during sprint acceleration
means it is possible to determine differ-
ences between performers but also to
establish a biomechanical link between
profile and sprint performance (74).
Field-based sprint profiling (63,70,75)
using inverse dynamics, a computation
method of calculating forces from kine-
matics of a body, is a highly reliable
process that has been evaluated against
gold standard laboratory-based
(65,67,75) tests using inbuilt force plate
systems. Field-based methods of pro-
filing, referred to by Samozino et al.
(75) as a simple method, are a practical
process needing limited technology
and equipment to determine an indi-
vidual’s mechanical profile and assess
the P
MAX
the neuromuscular system is
able to achieve during the acceleration
phase. Sprint profiling assists coaches
to identify the specific interventions
required to improve acceleration and
determine whether training should be
directed at increasing P
MAX
by
Figure 5. Resistance training categories across the force-velocity (load-velocity)
spectrum used to modify the mechanical variables or individualize the F-v
profile.
Figure 6. A selection of exercises across the force-velocity (load-velocity) spectrum
will be prescribed to each athlete depending on their level of mechanical
effectiveness across the acceleration phase.
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improving the horizontal force pro-
duced at low velocity, (force quality),
horizontal force at high velocity (veloc-
ity quality), or by training at optimal
load (maximal power). Sprint profiling
can provide some unique findings,
given that it is able to distinguish
between athletes independently of
P
MAX
values or sprint times. Although
time is the critical factor in sprint accel-
eration, 2 athletes may achieve similar
acceleration times and P
MAX
values
over a given distance yet with very dif-
ferent slopes and mechanical charac-
teristics to their F-v profiles
(Figure 4). This is connected to an ath-
lete’s ability to have a different combi-
nation (described as balance or
imbalance by Morin and Samozino
(62)) between force and velocity (force
dominant or velocity dominant), which
is also related to their mechanical effec-
tiveness for the duration of sprint
acceleration (62). In comparison to
generic training programs where the
focus is on improving absolute force
and sprint times, sprint profiling pro-
vides a specific guide for identifying
and targeting the athlete’s strengths
or weaknesses to improve their accel-
eration performance. This approach
has been explored with elite female
athletes in Rugby sevens (80) and team
handball players (71), where individual
speed training programs based on data
from sprint profiles showed varying
levels of effectiveness depending on
how the sprint profiles were inter-
preted and how training loads were
implemented. Morin and Samozino
(62) provided a written explanation
about the process of optimizing F-v
profiles, but information about practi-
cal sprint and resistance training inter-
ventions that may have assisted
coaches was limited.
PRACTICAL APPLICATIONS AND
GUIDELINES
The mechanical determinants and var-
iables seen in profiles such as force,
velocity, and power are susceptible to
the demands imposed on the body,
and key neuromuscular adaptations
can occur as a result of prescribing
specific exercises (87). This provides
scope for a strength and conditioning
coach to improve acceleration perfor-
mance by selecting exercises and loads,
which mostly target specific areas on
the theoretical F-v spectrum and prac-
tical load-velocity spectrum: force,
velocity, or power (Figure 5). The resis-
tance training exercises used in most
sports are traditionally prescribed off
characteristics across the F-v spectrum
and the load-velocity (and thus force)
context they induce within the move-
ment. Examples of exercises that span
this spectrum are detailed in Figure 6.
Figure 7. A weekly microcycle for a team sport detailing the integration of the technical and tactical sport focus, injury prevention,
recovery, and resistance training program (individualized to athlete sprint profile).
Mechanical Effectiveness during Sprint Acceleration
VOLUME 00 | NUMBER 00 | NOVEMBER 2019
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Resistance such as an athlete’s body-
weight against gravity or external loads
is a way to set the velocity at which the
maximum effort will occur and indicate
the production of force that is possible.
Studies that have used resistance train-
ing (including vertically and horizon-
tally oriented exercises) to improve
sprint performance have included
high-force/low-velocity exercises;
force-dominant (2,37,47), low-force/
high-velocity exercises; velocity-
dominant (2,5,10,23,47,52) and optimal
load exercises; and power-dominant
exercises (27,37), suggesting that the
load, orientation, and mechanical focus
may elicit different adaptations to the
performance.
Categorization of resistance training
exercises is useful to understand how
adaptations to the profile will affect
physical performance. Force-
dominant exercises are aimed at
improving the force applied at very
low velocities. In regard to sprinting,
these exercises focus on the athlete’s
ability to overcome inertia at the start
of the sprint acceleration and effec-
tively apply force in a backward direc-
tion, be it by improving the capacity of
the lower limb force produced or peak
mechanical effectiveness. Velocity-
dominant exercises are aimed at
improving the application of force at
high velocities to enhance the athlete’s
ability to maintain force application as
velocity increases. This can be
achieved by improving the lower limb
force production at high velocities
and/or by improving the orientation
of force and maintaining the highest
possible mechanical effectiveness
despite the increase in velocity.
Power-dominant exercises aim to
improve the force applied at moderate
velocities, that is, at close to half of the
theoretical maximal velocity (28,29).
These exercises stimulate the athlete’s
ability to produce greater P
MAX
output
during the sprint acceleration and,
when prioritized as interventions
within a training program and perio-
dized appropriately, can be effective
in enhancing performance. The aim
of selecting exercises across the F-v
spectrum is to target the variable con-
tributing to the current level of F-v
imbalance, thereby improving the ath-
lete’s overall mechanical effectiveness
across the sprint acceleration.
It is advisable that when selecting resis-
tance training exercises, they demon-
strate transfer to movement task and
enhance various characteristics that con-
tribute to sprint acceleration. Sprinting is
performed on a horizontal training axis
(sagittal plane); therefore, it may seem
intuitive to focus on exercises that
develop force in the same direction
(72,95), known as the “force-vector the-
ory” (14). Using exercises that allow ath-
letes to apply force in the same direction
(vector—magnitude and force) as that
which occurs in the sport task may sug-
gest a greater transference effect (93) or
dynamic correspondence (90) due to
similar overall biomechanical character-
istics. Using these concepts as an exam-
ple, volleyball or basketball players often
express movements vertically and there-
fore should address the F-v spectrum by
prioritizing exercises that have a vertical
force orientation. In comparison, Amer-
ican football players, rugby players, and
sprinters, who predominantly express
movement through linear locomotion,
wouldberecommendedtoprioritize
horizontally oriented exercises (50,93).
Although conjecture surrounds the
application of the force-vector theory
(34) (see the Limitations section), a thor-
ough understanding of the kinetics and
kinematics of the movement task is
essential when designing a resistance
training programs.
When designing and programming
training sessions to improve an athlete’s
horizontal profile, strength and condi-
tioning coaches need to appropriately
periodize resistance training–focused
sessions into the weekly sport training
program. The structure of a training
week in a team sport must primarily
focus on the tactical and technical ele-
ments of the sport and then prioritize
other modalities such as injury pre-
vention, recovery modalities, and resis-
tance training (Figure 7). For optimal F-v
adaptations, resistance training should
occur over the course of several meso-
cycles (30) or until the F-v profile has
been reassessed and adaptations that
contribute to improved P
MAX
and/or
a reduction in F-v imbalance are evident.
Continual assessments of the vertical
profile (jumping) to determine whether
F-v adaptations had occurred were re-
garded as critically important within
a recent study (44). Depending on the
level of F-v imbalance revealed in the
profile, some or all of the exercises
Table 1
Exercises to improve maximal force production
Exercise % 1RM/Load
Back squat .85%
Kettlebell swing .85%
Romanian deadlift .85%
Trap bar deadlift .85%
Hip thrust .85%
Midthigh pull .100% clean
Clean pull from knee .100% clean
Rack pull .100% deadlift
Prowler march Up to 150% BW
Resisted sprinting Up to 100% BW
BW 5bodyweight; 1RM 51 repetition maximum.
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identified in the following sections could
be integrated into a weekly microcycle,
ensuring a minimum 48-hour recovery
period between high-intensity days. This
is necessary to limit the level of residual
fatigue before the athlete embarks on the
next training session. Understanding the
training phase and how this may affect
the general or specific nature of exercise
intensity and selection is also a critical
factor in team sports (30). Schuster
et al. (79) explored these concepts in their
recommendations for physical prepara-
tion with Rugby 7 athletes, where
a weekly combination of high (2 ses-
sions), medium (2 sessions), and low (2
sessions) intensity sessions, including
strength and conditioning, rugby-
specific training, and recovery sessions,
were cycled across a week to optimize
performance during the preparation
block leading into competition.
Recommendations about addressing the
F-v imbalance and mechanical effective-
ness in sprint acceleration through tar-
geted resistance training programs
directed across the F-v spectrum are
detailed in the following sections.
IMPROVING FORCE PRODUCTION
AT LOW VELOCITIES
Athletes with physiological and perhaps
technical qualities that limit their ability
to apply a high amount of horizontal
force at low velocities are at a disadvan-
tage in many on-field competitive situa-
tions. This will be evident early on
during the sprint effort with their inabil-
ity to apply enough horizontal force,
thereby reducing their horizontal
impulse. In turn, this will compromise
the overall velocity that is achieved as
this is determined by the athlete’s ability
to accelerate to this speed. To improve
the force produced at low velocities, the
prescribed sprint and resistance training
needs to include movements that focus
on the right-hand side of the F-v spec-
trum, where force is applied against
a heavy external resistance, .85% 1 rep-
etition maximum (1RM) (86), and tar-
gets maximal strength qualities (Table 1).
Exercises that target maximal or abso-
lute strength and specifically improve
the force applied in a horizontal direc-
tion include heavy sled pulls, resisted
sprinting (Figure 8), and prowler
marches (Figure 9). Horizontally ori-
ented exercises at these loads will
encourage force application in the
same direction as what occurs during
the acceleration phase of a sprint.
Although maximal strength exercises
may only be specific to early accelera-
tion, several studies (3,86,87) that
focused on the right-hand side of the
F-v spectrum noted the crucial role
strength plays in providing the founda-
tion to improving maximal power,
highlighting its importance for poten-
tially improving other aspects of the F-
v spectrum. Table 2 identifies 2 resis-
tance training sessions, which could be
performed across 1 week, including
both horizontally and vertically ori-
ented exercises. These exercises and
the associated sets, repetitions, and
loads are programmed to improve
the maximal force produced at low
velocities.
IMPROVING FORCE PRODUCTION
AT HIGH VELOCITIES
Some athletes are capable of high lev-
els of force at low velocities but cannot
sustain it as their acceleration in-
creases. This often leads to a rapid
decrease in the RF (D
RF
) as the athlete
approaches top speed. Analysis of the
profile shows that it is likely that during
Figure 8. Resisted sprint training using a sled at 85% bodyweight (59).
Figure 9. Resisted sprint training using a prowler sled to march at 140% bodyweight.
Mechanical Effectiveness during Sprint Acceleration
VOLUME 00 | NUMBER 00 | NOVEMBER 2019
8
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
acceleration, the athlete will be losing
their ability to apply and orient hori-
zontal force too early, which during
acceleration corresponds to early
changes in body position from approx-
imately more horizontal to vertical.
Although the production of high
(mostly vertically oriented) force is
vital at maximal velocity (11,12,91),
the speed attained will be limited
because of a rapid decrease in the RF.
This has a direct impact in sporting
activities such as rugby when players
try to outrun their opponents when
making for the try line. Sprinters face
the same problem when they need to
maintain acceleration for a longer
duration and reach higher velocities
in a 100-m sprint. Improving sprint
acceleration performance over longer
distances and maintaining a high ratio
of horizontal-to-resultant force at
increasing velocities require exercises
that focus on characteristics from the
left-hand side of the F-v spectrum,
along with improved inter- and intra-
muscular coordination properties. Ex-
ercises demanding high velocity are
generally those that require high rates
of force (Table 3).
The F-v spectrum suggests that the
smallest load the human body can
work against is the force of gravity
on body mass such as when perform-
ing a vertical jump. However, research
suggests that even this load may be too
great to affect the velocity portion of
the F-v spectrum (51). Assisted vertical
jumps (Figure 10), using elastic bands,
are one method that has been used to
deload or negatively load an athlete’s
body mass by reducing the effects of
gravity on the body (51). Markovic and
Jaric (51) found that countermovement
jumps with zero load maximized mean
power and jump height, yet the veloc-
ity (peak) of the center of mass at take-
off increased by deloading bodyweight
by 30% (51). Horizontally oriented ex-
ercises, including a novel exercise
known as an assisted horizontal squat
jump (Figure 11), have been shown to
be beneficial to improving movement
velocity due to the extremely high
velocity reached by pushing against
almost zero gravity (42,77). This exer-
cise, part of a longitudinal training
intervention aimed at improving F-v
balance in individual profiles (44),
was shown to produce extremely large
changes in the velocity component of
the F-v profile, as well as effecting
increased jump heights.
Assisted sprinting may provide
another unique approach for overload-
ing the neuromuscular system at
Table 2
Force production at low velocity
Exercise
Week 1 Week 2 Week 3 Week 4
Volume Load Volume Load Volume Load Volume Load
Day 1—
horizontal
orientation
Resisted
sprinting
234
3
10 m
Load that
restricts to
,30% of
maximal
velocity
234
3
20 m
Load that
restricts to
,30% of
maximal
velocity
235
3
20 m
Load that
restricts to
,30% of
maximal
velocity
233
3
20 m
Load that
restricts to
,30% of
maximal
velocity
Prowler
march
2320,
30,
40 m
120% of BW 2 320,
30,
40 m
130% of BW 2 320,
30,
40 m
140% of BW 2 320,
30,
40 m
120% of BW
Hip thrusts 5 35 82.5% 5 35 87.5% 5 35 92.5% 5 35 85%
Day 2—
vertical
orientation
Clean pull 4 32 82.5% 6 32 87.5% 12 31 92.5% 4 32 85%
Back squat 3 35 87.5% 3 33 90% 3 33 92.5% 3 35 85%
Midthigh
pull (%
based off
clean)
335 110% 3 33 120% 3 33 130% 3 33 110%
BW 5bodyweight, % based off 1-repetition maximum in exercise.
Strength and Conditioning Journal | www.nsca-scj.com 9
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
higher than the maximal voluntary
velocities. Using a horizontal towing
mechanism such as the DynaSpeed
(MuscleLab) (Figure 12) or the
1080Sprint
TM
, acute horizontal run-
ning velocities increased, along with
lower limb electromyography activity,
which suggested that higher neural
activity took place with possible trans-
fer to unassisted maximal sprinting
(54–57). However, given that maximal
running velocity is by definition the far
left side of the F-v spectrum, research
should aim to verify whether training
over an individual’s maximal voluntary
running speed (i.e., overspeed training)
benefits unassisted performances. Plyo-
metric activities such as bounding,
drop jumps, and reactive jumps are also
recommended for athletes who want
to improve force produced at high
velocity due to the reliance on the
stretch-shortening cycle (31). Table 4
identifies 2 resistance training sessions
that could be performed across 1 week,
which include both horizontally and
vertically oriented exercises. These ex-
ercises and the associated sets, repeti-
tions, and loads are programmed to
improve the maximal movement
velocity of the athlete.
IMPROVING MAXIMAL POWER
(OPTIMAL LOADING CONDITIONS)
FOR SPRINTING
Training at a load that is associated
with movement velocity at which
maximal mechanical power occurs
has been shown to be the most effec-
tive method for increasing overall
maximal power (36,46). Haff and Nim-
phius (36) define optimal load as that
which maximizes mechanical power
for a specific exercise. Within the
strength and conditioning literature,
the assessment of power is broad, with
technology including force plates, lin-
ear position transducers (LPTs), and
accelerometers, deriving power metrics
that are used to determine optimal
load. Therefore, the context of the vari-
able must be understood and inter-
preted correctly when implementing
into the training program (see the Lim-
itations section). During resistance
training, the optimal load for develop-
ing P
MAX
in a jump squat has been
shown to range from 0% of 1RM
(18–20) to 30–45% of bench press
1RM in the bench press throw
(68,82) and 70–80% of IRM when per-
forming weightlifting exercises such as
the snatch and/or clean (18,22,46).
This approach to training has also been
used in cycling via torque-velocity tests
to determine the optimal pedaling con-
ditions (frequency) over a set distance
(32). The discrepancy in power assess-
ment and 1RM percentages across
a range of exercises demonstrates a lack
of clarity and inconsistency to deter-
mine the load to achieve P
MAX
.
However, improving maximal horizon-
tal power for sprinting requires focusing
on the factors that contribute to this var-
iable: horizontal force and horizontal
Table 3
Exercises to improve maximal movement velocity
Exercise % 1RM/Load
Countermovement jump BW
Assisted jumps Assisting force to deload BW by 30%
Horizontal squat jump ,BW
Assisted horizontal squat jump Assisting force 95–110 N
Squat jumps BW—10% BW
Assisted sprinting 100–106% maximal velocity
Reactive jumps BW
Box jump (bilateral and unilateral) BW
Jump shrug BW + 20–40 kg
Hang high pull BW + 20–40 kg
BW 5bodyweight; 1RM, 1 repetition maximum.
Figure 10. Pre-load contermovement jump with band resistance, B: Toe-off position
with band assistance (increased vertical velocity), C: Flight phase
(increased jump height). Assisted vertical jumps to deload athlete body-
weight against gravity by 30% using an elastic band (51).
Mechanical Effectiveness during Sprint Acceleration
VOLUME 00 | NUMBER 00 | NOVEMBER 2019
10
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
velocity. Depending on the training
phase and needs of the athlete, exercise
prescription should be directed to all
partsoftheF-vspectrumtoensurethat
a strong level of mechanical effectiveness
is maintained and to achieve the highest
ratio of horizontal force during acceler-
ation. In regard to sprinting, this may
entail using specific exercises for produc-
ing maximum power by training at an
optimal load (27). Optimal load training
has previously been shown to be more
effective for improving dynamic athletic
performance compared with other load-
ing conditions (68,92). However, com-
bining different resistance training loads
to improve power and ballistic
performance has also been shown to be
effective in many studies
(17,37,45,52,88,89). With this in mind,
across the F-v spectrum, exercises to
improve maximal power could include
resisted sprinting, sprinting at maxi-
mum speed, jump squats (trap bar)
(Figure 13), plyometrics (horizontal
bounding), and assisted sprinting (Fig-
ure 12). Highlighting exercises from all
aspects of the F-v spectrum should
result in athletes maintaining or raising
their mechanical effectiveness with
limited decline in either contributing
variable. Although all loads across the
F-v spectrum contribute to P
MAX
,
Table 5 identifies 2 resistance training
sessions that could be performed
across 1 week, which include both hor-
izontally and vertically oriented exer-
cises. These exercises and the
associated sets, repetitions, and loads
are programmed to focus on maximiz-
ing power.
LIMITATIONS TO SPRINT
PROFILING
Coaches need to carefully consider the
implications of the training interventions
they select to address characteristics of
the F-v profile. Potential weaknesses
should be addressed but not at the
expense of building on athlete strengths.
It follows that strength and conditioning
coaches need to keep sight of their pri-
mary training goals and use sprint pro-
filing as a monitoring and diagnostic tool,
similar to testing hamstring strength or
force plate analysis of vertical jump ac-
tions to assess benchmarks. Detraining
qualities is a risk if too much time is being
expended on weaknesses. For example,
an athlete who produces maximal power
with lower force values will result in de-
creases in velocity values if training
focuses on those particular movements
for an extended period. This may impact
on an athlete’s ability to produce power
in situations where force is required at
different magnitudes and velocity (36).
Recent research suggests that the selec-
tion of exercises based solely on
dynamic correspondence and the
force-vector theory (34) contains certain
limitations. A thorough understanding of
dynamic correspondence often means
that the selection of specific exercises is
narrow and predetermined. Contreras
et al. (14) and, more recently, Loturco
et al. (49) suggest that the force-vector
theory should be the primary focus when
selecting exercises to improve sprint
acceleration and maximal velocity. The
theory states that the force-vector, which
comes into play when sprinting, occurs
in the anteroposterior direction relative
to the body, and therefore, the exercises
selected must focus on producing hori-
zontal force and provide necessary time
for skill acquisition, which in turn should
improve transfer to the performance to
a greater degree than vertically oriented
exercises (14). Currently, most resistance
Figure 11. A: Loading against box in start position with band resistance, B: Toe-off
position with band assistance (increased horizontal velocity). Assisted
horizontal squat jump using a roller board and elastic band to push
against reduced gravity (1,43,44).
Figure 12. Assisted sprinting using the DynaSpeed (MuscleLab) to allow athletes
sprint at supramaximal speed (54,56,57).
Strength and Conditioning Journal | www.nsca-scj.com 11
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Table 4
Force production at high velocity
Exercise
Week 1 Week 2 Week 3 Week 4
Volume Load Volume Load Volume Load Volume Load
Day 1—horizontal
orientation
Assisted
sprinting
(DynaSpeed)
1320, 30,
40 m
(upright
posture)
101% of training
maximal velocity
(flying run)
1330, 30,
40 m
(upright
posture)
102% of training
maximal velocity
(flying run)
1330, 40,
50 m
(upright
posture)
103% of training
maximal velocity
(flying run)
1320, 30,
40 m
(upright
posture)
101% of training
maximal velocity
(flying run)
Maximal
sprinting
3340 m
(20 m accel
+ 20 m fly)
BW 3 350 m
(20 m accel
+ 30 m fly)
BW 3 360 m
(30 m accel
+ 30 m fly)
BW 2 340 m
(20 m accel
+ 20 m fly)
BW
Horizontal
bounding (8
contacts/set)
338 cts BW 4 38 cts BW 5 38 cts BW 3 38 cts BW
Day 2—vertical
orientation
Reactive hurdle
hops (5
contacts/set)
335 cts BW 4 35 cts BW 5 35 cts BW 3 35 cts BW
Band-assisted
vertical
jumps
235 Deload BW 30% 3 35 Deload BW 30% 4 35 Deload BW 30% 2 35 Deload BW 30%
Double-leg
depth jump
to box
236BW 335BW 336BW 236BW
accel 5acceleration, BW 5bodyweight, cts 5contacts, fly 5flying run.
Mechanical Effectiveness during Sprint Acceleration
VOLUME 00 | NUMBER 00 | NOVEMBER 2019
12
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
exercises are vertically oriented (72), for
example, the back squat, deadlift, or
weightlifting derivatives, therefore
emphasizing vertical force production
(72). However, this serves to negate hor-
izontally oriented force and opposes
dynamic correspondence and the
force-vector theory. Notwithstanding,
Loturco et al. (49) found strong correla-
tions with sprint performance when per-
forming hip extension–focused exercises,
for example, hip thrust, with the initial
phase of the sprint acceleration, whereas
those exercises loaded vertically, for
example, jump squat, showed greater
transfer to the maximal velocity phase.
Both of these findings, however, are in
direct contrast to the findings of Seitz
et al. (81) who found positive accelera-
tion changes, 0–30 m, from studies pri-
marily concerned with the back squat,
and Jarvis et al. (41) who found no sprint
performance transfer from an 8-week
study using the hip thrust exercise. This
suggests that conjecture remains in re-
gard to the training axis, which should
be used to enhance sprint acceleration
performance.
Although the force-vector theory is
intuitive in many respects, Fitzpatrick
et al. (34) proposed that applying the
force-vector theory to training was
a basic misunderstanding of simple
mechanics. Primarily, the issue lies in
understanding the difference between
the direction of force relative to the
global frame, as against the direction
of force determined by the orientation
of the athlete (35). This is evident in
sprinting when the athlete adopts a tri-
ple flexion (front-side mechanics)
position during acceleration and when
reaching maximal velocity; the orien-
tation of the body is at approximately
458while accelerating and at approx-
imately 908when at maximal velocity.
Kugler and Janshen (48) noted the
strong relationship between body lean
and direction of GRF, as leaning for-
ward during acceleration places the
athlete in an advantageous position
for applying propulsive force. How-
ever, although orientation of force
needs to be understood, from a practi-
cal standpoint, a combination of both
vertically and horizontally loaded
resistance training exercises seems to
be the ideal approach when attempt-
ing to improve sprint performance
(14,49,72,95).
Maximal power is a major perfor-
mance indicator and thus frequently
a priority when selecting exercises to
improve dynamic, ballistic
performance
(16,18,19,21,22,25,82,85,87), yet con-
jecture and difficulties exist when
determining load for actions involving
multiple joints. Maximal power and
optimal load is influenced not only
by the technology that derives the vari-
able but also by whether it is specific to
“system power” (external—whole
body), joint power (internal—at a spe-
cific joint), or perhaps more applicable
to the weight room, “bar power” (using
an LPT). Previously, Cormie et al. (15)
have recommended using a combina-
tion of a force plate and an LPT to best
determine power in lower-body exer-
cises. In a resistance training context,
the discrepancies in how optimal load
is reported therefore present a high
level of ambiguity in reference to the
load-power relationship and present is-
sues with how practitioners can make
sense of how to apply exercise pre-
scription to not only improve maximal
power but how optimal load is estab-
lished (15). The use of a range of meth-
odologies to determine power has led
to a broad range of approximate 1RM
percentages for which maximal power
is developed in various exercises such
as the power clean, squat, and jump
squat. Considerations for effectively
understanding and interpreting opti-
mal load must also include the specific
movement pattern(s) used, training his-
tory/status of the athlete, and whether
the exercise uses single or multiple
joints (22).
Cross et al. (29) noted that during un-
resisted sprint acceleration, maximal
power was achieved within the first 2
seconds of the movement, and there-
fore, the remainder of the sprint
occurred at a suboptimal load. To re-
create and extend the conditions in
which athletes move at an optimal
load, resisted sprint training was intro-
duced using a loaded sled that corre-
sponded to approximately 96% of the
athlete’s body mass or equivalent to
a velocity decrement of ;50% of max-
imal velocity. This allowed athletes to
sprint at optimal loads throughout the
acceleration phase. In a later study, fur-
ther changes to sprint acceleration
Figure 13. A: Start position of lift, B: Accelerating load vertically, C: Loaded flight
phase. Jump squat with trap bar at optimal load (approximately 40% BW).
Strength and Conditioning Journal | www.nsca-scj.com 13
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Table 5
Force production at maximal power (optimal load)
Exercise
Week 1 Week 2 Week 3 Week 4
Volume Load Volume Load Volume Load Volume Load
Day 1—horizontal
orientation
Maximal sprinting 3 330 m (20 m
accel + 10 m fly)
BW 4 330 m (20 m
accel + 10 m fly)
BW 3 340 m (20 m
accel + 20 m fly)
BW 2 340 m (20 m
accel + 20 m fly)
BW
Resisted sprinting
(DynaSpeed)
2310, 20, 30 m Individual
P
MAX
3320, 30 m Individual
P
MAX
233330 m Individual
P
MAX
4330 m Individual
P
MAX
Hip thrust 3 35 Individual
P
MAX
335 Individual
P
MAX
435 Individual
P
MAX
335 Individual
P
MAX
Day 2—vertical
orientation
Power snatch 4 33 30–50% 4 33 30–50% 5 32 30–50% 4 32 30–50%
Power clean 4 33 70–80% 4 34 70–80% 4 34 70–80% 5 32 70–80%
Jump squat (trap bar) 5 33 20–50% 5 33 20–50% 6 32 20–50% 5 32 20–50%
accel 5acceleration, BW 5bodyweight, fly 5flying run, P
MAX
5maximal power, % based off 1-repetition maximum in exercise.
Mechanical Effectiveness during Sprint Acceleration
VOLUME 00 | NUMBER 00 | NOVEMBER 2019
14
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
were not evident when athletes per-
formed a resisted sprinting protocol
at optimal load compared with groups
that used lighter or heavier loads (29).
However, the authors acknowledged
that the current state of the individual
F-v profile and the random group
assignment may well have affected
greater adaptations to sprint accelera-
tion, and greater research is required.
One limitation recently noted on sprint
profiling methodology using the “simple
method” (63) is that the power variable
only represents step-averaged external
power produced in the horizontal direc-
tion to accelerate the body center of
mass, neglecting the internal “joint”
power (P
int
) required to move the limbs
around the center of mass (69). Pavei
et al. (69) suggest that other mechanical
components aside from horizontal
power are needed to accelerate in
a sprint such as the body center of mass
and internal power (P
int
). Although the
simple method provides valuable insight
into power in the horizontal direction
across the sprint acceleration, there
must be the understanding that no inter-
nal power variables are measured, and
therefore, the overall power output
computed via the simple method will
be an underestimation of the total
power developed by muscles but will
rather characterize the power capabil-
ities of overall sprint propulsion. Not-
withstanding, the practical application
to coaches using P
int
is limited, consid-
ering the exhaustive technology neces-
sary to obtain the data, and therefore,
the simple method may be a more
appropriate measure in the field. In addi-
tion, it is not known whether P
int
is
a performance indicator, thus a key vari-
able of interest in training.
Therefore, when using optimal load as
a training strategy to improve maximal
power, it is prudent to understand the
context of power being measured,
along with incorporating a variety of
loads across the F-v spectrum to
ensure a balanced approach for force
and velocity adaptations (25,88,89).
FURTHER CONSIDERATIONS
Most literature on sprint profiling dis-
cusses factors that contribute to the
overall mechanical output across the
performance; however, there has been
a growing level of interest in understand-
ing the application of sprint profiling in
the rehabilitation field and return-to-
play (RTP) protocols from hamstring in-
juries (53). Although not the primary
focus of this review, the application of
using mechanical variables of pre-injury
performance and using these in the RTP
protocols with sports medicine staff may
provide further comparative data to
ensure a safe return to performance.
Mendiguchia et al. (53) identified that
sprint profiling highlights the capability
to produce horizontal force at low speed
is a limiting factor to performance when
returning from a hamstring injury; there-
fore, the application of sprint profiling as
a monitoring tool to assess how force
production changes across a competitive
season or in response to an injury could
be useful individual information to sports
medicine staff.
SUMMARY
Sprint profiling using the field methods
briefly outlined in this review offers an
innovative and alternative approach to
understand the mechanical determinants
of sprint acceleration. Although further
research and experimental evidence is
needed, together with applied longitudi-
nal exercise interventions, the field
method is a practical and valid approach
that allows strength and conditioning
coaches to access kinetic data on sprint
acceleration, which previously was only
attainable in a laboratory. These data
allow coaches to design individualized
training programs.
The resistance training program used
to address mechanical effectiveness
should consist of exercises that focus
on both horizontal and vertical force
production, acknowledging the limita-
tions to the force-vector theory; how-
ever, a priority could be placed on one
orientation over the other depending
on the phase of the training cycle or
the needs of the athlete. Sprint profil-
ing can be used for athletes involved in
sports where sprint acceleration is cru-
cial and for identifying and changing
the variables contributing to perfor-
mance. It may allow coaches to devise
individualized training programs to
a greater degree compared with tradi-
tional methods as a means of enhanc-
ing sprint acceleration and improving
the effectiveness of force application.
Guidelines for implementing a training
and/or rehabilitation program that ad-
dresses the mechanical variables of
horizontal force-velocity and power-
velocity include the following:
Assess the capabilities of producing
horizontal force and the mechani-
cal effectiveness of force applica-
tion during sprint acceleration
(sprint profile)
Identify any existing F-v imbalance
across sprint acceleration.
Prescribe appropriate training pro-
grams to address the needs of the
athlete and the slope of the profile.
Reassess the athlete after an appro-
priate period to determine adapta-
tions to mechanical effectiveness
and changes to sprint acceleration.
Conflicts of Interest and Source of Funding:
The authors report no conflicts of interest
and no source of funding.
Dylan Shaun
Hicks is a PhD
candidate and
teaching faculty
member in Exer-
cise Science at
Flinders Univer-
sity, South
Australia.
Jake George
Schuster is
Senior Sports
Scientist at Vald
Performance and
Affiliate
Researcher at
Florida State
University’s
Institute of Sports
Science and Sports Medicine.
Strength and Conditioning Journal | www.nsca-scj.com 15
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
Pierre
Samozino is
Associate Profes-
sor in the Sport
Science depart-
ment and the
Laboratoire In-
teruniversitaire
de Biologie de la
Motricite
´at the
University Savoie Mont Blanc.
Jean-Benoit
Morin is a Full
Professor at the
Universite
´Co
ˆte
d’Azur, Director
of the Masters in
Sports Perfor-
mance & Train-
ing Science and
the Associate
Dean for Research, Faculty of Sport
Science.
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Mechanical Effectiveness during Sprint Acceleration
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... In theory, this parameter can be improved by applying greater absolute force magnitudes to the ground (Haugen et al., 2019) or by applying the same force magnitude in a more horizontal direction (Morin et al., 2011). Improving athletes' acceleration techniques aims at improving the latter aspect, i.e., the effectiveness of force applied to the ground (Hicks et al., 2020). ...
... Consequently, efficient acceleration needs a degree of 'patience' to give the CoM the time to rotate to avoid excessive vertical acceleration (Hicks et al., 2020;Jacobs & van Ingen Schenau, 1992;Kugler & Janshen, 2010;Moir et al., 2018). Nevertheless, this rotational component has subsequently attracted no further research attention even though it is considered as a potential key mechanism to bring the body into a configuration where forces can be applied most effectively to induce forward acceleration. ...
... Derived from sprinting at maximal velocity, athletes are usually taught to powerfully attack the ground by either a pronounced 'pawing action' or an active 'downward drive' (like a 'hammer striking a nail') of the foot (Alt et al., 2021;Clark et al., 2020;Haugen et al., 2018). Subsequently, stance phaserelated instructions intend to 'brake less' and to 'push more' during accelerated sprinting (Hunter et al., 2005; by means of a 'stiff and rigid ankle joint' (Bezodis et al., 2015;Charalambous et al., 2012;Hicks et al., 2020;J. Smith, 2018). ...
Article
Linear acceleration is a key performance determinant and major training component of many sports. Although extensive research about lower limb kinetics and kinematics is available, consistent definitions of distinctive key body positions, the underlying mechanisms and their related movement strategies are lacking. The aim of this 'Method and Theoretical Perspective' article is to introduce a conceptual framework which classifies the sagittal plane 'shin roll' motion during accelerated sprinting. By emphasising the importance of the shin segment's orientation in space, four distinctive key positions are presented ('shin block', 'touchdown', 'heel lock' and 'propulsion pose'), which are linked by a progressive 'shin roll' motion during swing-stance transition. The shin's downward tilt is driven by three different movement strategies ('shin alignment', 'horizontal ankle rocker' and 'shin drop'). The tilt's optimal amount and timing will contribute to a mechanically efficient acceleration via timely staggered proximal-to-distal power output. Empirical data obtained from athletes of different performance levels and sporting backgrounds are required to verify the feasibility of this concept. The framework presented here should facilitate future biomechanical analyses and may enable coaches and practitioners to develop specific training programs and feedback strategies to provide athletes with a more efficient acceleration technique.
... La efectividad mecánica del sprint, describe cómo cambia la orientación del vector de fuerza a medida que se avanza (Hicks et al., 2019 de Hicks, et al., 2019, p. 4) Los datos obtenidos de esta evaluación, proporcionan información importante para la selección de ejercicios, ya sea para mejorar la fuerza horizontal a baja velocidad, a alta velocidad o a potencia máxima (Hicks et al., 2019). De esta forma, se podría realizar un entrenamiento específico de la orientación de fuerza requerida por el deportista para optimizar su rendimiento. ...
... La efectividad mecánica del sprint, describe cómo cambia la orientación del vector de fuerza a medida que se avanza (Hicks et al., 2019 de Hicks, et al., 2019, p. 4) Los datos obtenidos de esta evaluación, proporcionan información importante para la selección de ejercicios, ya sea para mejorar la fuerza horizontal a baja velocidad, a alta velocidad o a potencia máxima (Hicks et al., 2019). De esta forma, se podría realizar un entrenamiento específico de la orientación de fuerza requerida por el deportista para optimizar su rendimiento. ...
... A grandes rasgos, las orientaciones de trabajo que nos puede brindar esta herramienta, según Hicks et al. (2019), son: ...
Thesis
Full-text available
La presente tesis busca demostrar la veracidad de la teoría del vector de fuerza, ¿importa la fuerza neta o con qué dirección la manifestamos? Estudio realizado con 15 deportistas activos, a los cuales se testeó con diferentes saltos (verticales y horizontales) y sprint. Se utilizan los coeficientes de correlación de Pearson y Spearman, observándose mayores fuerzas de correlaciones para los saltos horizontales.
... In theory, this parameter can be improved by applying greater absolute force magnitudes to the ground (Haugen et al., 2019) or by applying the same force magnitude in a more horizontal direction (Morin et al., 2011). Improving athletes' acceleration techniques aims at improving the latter aspect, i.e., the effectiveness of force applied to the ground (Hicks et al., 2020). ...
... Consequently, efficient acceleration needs a degree of 'patience' to give the CoM the time to rotate to avoid excessive vertical acceleration (Hicks et al., 2020;Jacobs & van Ingen Schenau, 1992;Kugler & Janshen, 2010;Moir et al., 2018). Nevertheless, this rotational component has subsequently attracted no further research attention even though it is considered as a potential key mechanism to bring the body into a configuration where forces can be applied most effectively to induce forward acceleration. ...
... Derived from sprinting at maximal velocity, athletes are usually taught to powerfully attack the ground by either a pronounced 'pawing action' or an active 'downward drive' (like a 'hammer striking a nail') of the foot (Alt et al., 2021;Clark et al., 2020;Haugen et al., 2018). Subsequently, stance phaserelated instructions intend to 'brake less' and to 'push more' during accelerated sprinting (Hunter et al., 2005; by means of a 'stiff and rigid ankle joint' (Bezodis et al., 2015;Charalambous et al., 2012;Hicks et al., 2020;J. Smith, 2018). ...
Preprint
Linear acceleration is a key performance determinant and major training component of many sports. Although extensive research about lower limb kinetics and kinematics is available, consistent definitions of distinctive key body positions, the underlying mechanisms and their related movement strategies are lacking. The aim of this ‘Method and Theoretical Perspective’ is to introduce a conceptual framework which classifies the sagittal plane ‘shin roll’ motion during accelerated sprinting. By emphasizing the importance of the shin segment’s orientation in space, four distinctive key positions are presented (‘shin block’, ‘touchdown’, ‘heel lock’ and ‘propulsion pose’) which are linked by a progressive ‘shin roll’ motion during swing-stance transition. The shin’s downward tilt is driven by three different movement strategies (‘shin alignment’, ‘horizontal ankle rocker’ and ‘shin drop’). The tilt’s optimal amount and timing will contribute to a mechanically efficient acceleration via timely staggered proximal-to-distal power output. Empirical data obtained from athletes of different performance levels and sporting backgrounds are required to verify the practicability of this concept. The presented framework may help coaches and practitioners specify their feedback strategies and develop demand-specific training programs to educate and equip athletes with a more efficient acceleration technique. Scientists are encouraged to use it as template for future biomechanical analyses.
... Non-sprint specific methods are known as tertiary methods and represent a broad scope of training modalities including plyometrics and traditional strength and power resistance training [81,83]. These training methods do not simulate the sprint movement pattern; however, they do elicit a targeted neuromuscular stimulus that underpin the biomechanical components of sprint acceleration such as FVP capacities, and the force-velocity profile [59,84,85]. Additionally, a recent systematic review with meta-analysis reported significant moderate improvements in short sprint performance (0 -5m, 0 -10m, and 0 -20m) from non-specific sprint training methods [81]. ...
... The findings have important training considerations for strength and conditioning practitioners working with athletes in the AF participation pathway who should focus on improving force producing capabilities at low velocities. To develop a more force orientated profile and improve force producing capacities the prescribed sprint and resistance training programme needs to include exercises where force is applied against heavy external resistance, >85% of one repetition-maximum to target maximal strength qualities [85]. It is also important to consider the specificity and transference of exercises to sprint performance as the force-velocity profile during maximal sprints does necessarily match the force-velocity profile in other tasks such as vertical jumps [68,124]. ...
... It is also important to consider the specificity and transference of exercises to sprint performance as the force-velocity profile during maximal sprints does necessarily match the force-velocity profile in other tasks such as vertical jumps [68,124]. In this instance, exercises that target maximal strength qualities and specifically improve force producing capacity during sprinting include heavy prowler marches, resisted sprinting, and sled pulls should be used in conjunction with traditional exercises such as heavy back squats [85]. ...
Thesis
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.
... The use of GNSS data to calculate sprint forcevelocity power profiling has recently been explored (66), but more work is needed to validate this process. Sprint forcevelocity-power profiling provides a detailed assessment of sprint capabilities and can facilitate an individualized approach to speed development (48). For example, where horizontal force deficits are observed, programming should focus on horizontal strength work (48). ...
... Sprint forcevelocity-power profiling provides a detailed assessment of sprint capabilities and can facilitate an individualized approach to speed development (48). For example, where horizontal force deficits are observed, programming should focus on horizontal strength work (48). Furthermore, the growth in available normative data for soccer players with respect to F 0 , V 0 , sFV, Pmax, and RF (%) has made this contemporary approach more viable for practitioners. ...
Article
Soccer match play dictates that players possess well-rounded physical capacities. Therefore, player physical development plans must consider developing several fitness components simultaneously. Effective individualization of training is likely facilitated with appropriate player profiling; therefore, developing a time-efficient and informative testing battery is highly relevant for practitioners. Advances in knowledge and technology over the past decade have resulted in refinements of the testing practices used by practitioners working in professional male and female soccer. Consequently, a contemporary approach to test selection and data analysis has progressively been adopted. Furthermore, the traditional approach of using a testing battery in a single day may now be outdated for full-time players, with a flexible approach to the scheduling of testing perhaps more suitable and time efficient. Here, guidance on testing for maximal aerobic, sub-maximal aerobic, linear and change of direction speed, and stretch-shortening cycle performance (i.e., jump testing) are presented for male and female players, with emphasis on time efficient tests, while facilitating effective individualized training prescription. Normative and meaningful change data are presented to aid decision making and provide a reference point for practitioners. Finally, a time-efficient approach to scheduling fitness testing is presented, which complements daily training outcomes of a weekly periodization approach.
... From a practical point of view, athletes with horizontal force deficits, at the begging of the sprint, should prioritize their training by using horizontal resistance training at low velocities, such as pushing or pulling heavy sleds. Whereas athletes with velocity deficits should be prescribed more maximal velocity sprinting by using overspeed training and light sleds (Hicks et al., 2020;. ...
Article
Full-text available
The aim of this study was to explore the sprint mechanical and kinematic characteristics of sub-elite and recreational male sprinters during the acceleration phase of a linear sprint running section. Eighteen sprinters (nine sub-elite, nine recreational) performed two all-out 30-m sprints. Three high speed panning cameras were used to record the entire sprint distance continuously. The sprint velocity-time data of each camera were determined by temporal analysis of the video recording. These values were used to determine the variables of the horizontal F-v profile (theoretical maximal values of horizontal force [F0], velocity [v0], power [Pmax], the maximal ratio of horizontal to resultant force [RFmax], the decline in the ratio of horizontal force production as the running speed increases [DRF]) and key kinematic characteristics. Significantdifferences were observed between the groups for v0 (0.79 ± 0.24 m∙s-1, p = 0.005), Pmax (3 ± 1.17 W∙kg-1, p = 0.020) and RFmax (3.1 ± 1.2 %, p = 0.021). No statistical differences were found for F0 (0.55 ± 0.46 N∙kg-1, p = 0.25) and DRF (0.2 ± 0.5 %∙s∙m, p = 0.67). The mean running velocity and mean step rate were higher, whereas mean ground contact time was shorter in sub-elite sprinters. There were no differences in mean step length and mean flight time. The sub-elite sprinters in our study demonstrated the capacity to generate higher amounts of horizontal forces at higher running speeds, apply horizontal force to the ground more efficiently and achieve higher step rates during sprint acceleration than recreational sprinters.
... 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.
... The sprint acceleration phase is characterized by the capacity to produce high levels of force and power in order to reach the maximum running velocity [1]. Acceleration performance depends on sprint kinetics, such as the magnitude and the orientation of the ground reaction force vector [2]. Mechanical effectiveness, i.e., the effective application of lower limb force in a horizontal direction as velocity increases, is significantly related to sprint performance [3][4][5]. ...
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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.
... A notable example of this in sprint running is the 'ratio of forces' (i.e., horizontal force/total force) (Morin et al., 2011), which provides a metric of the technical capability to apply force in such a way that accelerates the athlete. In practice, this ratio can subsequently be measured (Morin, Samozino, Murata, Cross, & Nagahara, 2019) and targeted for specific development (Hicks, Schuster, Samozino, & Morin, 2019). The same concept applies in alpine skiing, although there is considerably less research dictating the importance of force output in general, nor on the balance between specific force capacities and their technical derivatives on the field. ...
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The literature characterizing force production during skiing, and the associated capacities of skiers, is complicated to synthesize due to ageing results or relatively unspecific assessments. The overarching aim of this doctoral thesis was to clarify the importance of force-output for skiing and of specific force-production capacities for different disciplines. The thesis comprised two themes: 1) characterizing the force-output of skiers (N=15) on a giant-slalom course using kinematic and kinetic data from a global positioning system and boot-mounted force-platforms, respectively; and 2) measurement of dynamic and isometric force, the effect of countermovement on force production at different velocities, and specific strength-endurance across disciplines, and performance levels, in national skiers (N=31) and sprinters (N=30, for comparisons). The conclusions from Theme 1 were that radial force-output applied to turn the skis was linked with performance (R2=0.31–0.68, p<.032), and depended on both total magnitude and the ability to apply the force effectively (β=0.63–1.00, p<.001). A high total force magnitude was associated to high force production by both the outside and inside limbs (β=0.92–1.00 and 0.631–0.811, respectively, p<.001). For Theme 2, athletes from speed and technical disciplines displayed different dynamic and isometric force qualities, with the former showing superior dynamic force at low velocities (ω2=0.17, p<.001) and in isometric conditions (ω2=0.16–0.22, p<.003). Overall, performance was linked with a more force-dominant profile (ω2=0.34; r=-0.60– -0.67, p<.001) and increased rate of force development characteristics (r=-0.50– -0.82, p<.048). Robust associations existed between maximum isometric force and speed discipline performance (r=-0.88, p<.001), but tended to be for technical athletes (r=-0.49, p=.052). Force production at moderate velocities did not separate disciplines, nor was it associated with performance. Variability in the shift of mechanical characteristics and inverse correlations between force augmentation at different velocities (rs=-0.74, p<.001) indicated countermovement effect depended on extension velocity. Skiers exhibited a smaller countermovement effect at low velocities (rrb=-0.68, p<.001), with the opposite observation for sprinters (rrb=0.43, p=.008). ‘Moderate’ velocities failed to differentiate groups. Better skiers produced greater force at low speeds with a smaller countermovement effect, which supports the existence of velocity-specific strength qualities. The ski-specific strength-endurance assessment yielded some discriminative results, but, due to interactions between the test settings and real athlete capacities, the principal value of this section was to direct future protocol design. This thesis generally supports the assertion that force output during skiing is partly limited by force production capacities. On snow, both high force-output capacity and effectiveness of application were associated with performance. Off snow, better-ranked athletes possessed the highest capacity for specific force-production capabilities. High-level skiers appear to display a dominance of force-production at low speeds and in isometric conditions compared to other sports.
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This study assessed the effect of heavy resisted sled-pull training on sprint times, and force, velocity, and power characteristics in junior Australian football players. Twenty-six athletes completed a six-week resisted sled-pull training intervention which included 10 training sessions and 1-week taper. Instantaneous velocity during two maximal 30 m sprints was recorded 1 week prior and 1 week after the intervention with a radar gun. Velocity-time data was used to derive sprint performance and force, velocity, and power characteristics. A paired t-test assessed the within-group differences between pre- and post-intervention testing. Statistical significance was accepted at p≤0.05. Hedges' G effect sizes (ES) were used to determine the magnitude of change in dependent variables. Maximum velocity (ES=1.33) and sprint times at all distances (ES range 0.80-1.41) significantly improved post heavy resisted sled-pull training. This was reflected in sprint force, velocity, and power characteristics with significant improvements in relative theoretical force (ES=0.63), theoretical velocity (ES=0.99), relative maximum power (ES=1.04), and ratio of horizontal to vertical force (ES=0.99). Despite the multi-factorial nature of training and competing physical demands associated with pre-season training, these findings imply that a short, resisted sled-pull training mesocycle may improve sprint performance and underlying force, velocity, and power characteristics in junior athletes.
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Measuring the ground reaction forces (GRF) underlying sprint acceleration is important to understanding the performance of such a common task. Until recently direct measurements of GRF during sprinting were limited to a few steps per trial, but a simple method (SM) was developed to estimate GRF across an entire acceleration. The SM utilizes displacement- or velocity-time data and basic computations applied to the runner's center of mass and was validated against compiled force plate (FP) measurements; however, this validation used multiple-trials to generate a single acceleration profile, and consequently fatigue and error may have introduced noise into the analyses. In this study, we replicated the original validation by comparing the main sprint kinetics and force-velocity-power variables (e.g. GRF and its horizontal and vertical components, mechanical power output, ratio of horizontal component to resultant GRF) between synchronized FP data from a single sprinting acceleration and SM data derived from running velocity measured with a 100 Hz laser. These analyses were made possible thanks to a newly developed 50-m FP system providing seamless GRF data during a single sprint acceleration. Sixteen trained male sprinters performed two all-out 60-m sprints. We observed good agreement between the two methods for kinetic variables (e.g. grand average bias of 4.71%, range 0.696 ± 0.540-8.26 ± 5.51%), and high inter-trial reliability (grand average standard error of measurement of 2.50% for FP and 2.36% for the SM). This replication study clearly shows that when implemented correctly, this method accurately estimates sprint acceleration kinetics.
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Sprint running is a common feature of many sport activities. The ability of an athlete to cover a distance in the shortest time relies on his/her power production. The aim of this study was to provide an exhaustive description of the mechanical determinants of power output in sprint running acceleration and to check whether a predictive equation for internal power designed for steady locomotion is applicable to sprint running acceleration. Eighteen subjects performed two 20 m sprints in a gym. A 35‐camera motion capture system recorded the 3D motion of the body segments and the body center of mass (BCoM) trajectory was computed. The mechanical power to accelerate and rise BCoM (external power, Pext) and to accelerate the segments with respect to BCoM (internal power, Pint) were calculated. In a 20 m sprint, the power to accelerate the body forward accounts for 50% of total power; Pint accounts for 41% and the power to rise BCoM accounts for 9% of total power. All the components of total mechanical power increase linearly with mean sprint velocity. A published equation for Pint prediction in steady locomotion has been adapted (the compound factor q accounting for the limbs' inertia decreases as a function of the distance within the sprint, differently from steady locomotion) and is still able to predict experimental Pint in a 20 m sprint with a bias of 0.70±0.93 W·kg−1. This equation can be used to include Pint also in other methods that estimate external horizontal power only. This article is protected by copyright. All rights reserved.
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Aims: We analysed the changes in force-velocity-power variables and jump performance in response to an individualized training program based on the force-velocity imbalance (FVimb). In particular, we investigated (i) the individual adaptation kinetics to reach the optimal profile and (ii) de-training kinetics over the three weeks following the end of the training program. Methods: Sixty subjects were assigned to four sub-groups according to their initial FVimb: high or low force-deficit (FD) and high or low velocity-deficit (VD). The duration of training intervention was set so that each individual reached their "Optimal force-velocity (F-v) profile". Mechanical and performance variables were measured every 3 weeks during the program, and every week after the end of the individualized program. Results: All subjects in the FD sub-groups showed extremely large increases in maximal theoretical force output (+30±16.6% Mean±SD; ES = 2.23±0.28), FVimb reduction (-74.3±54.7%; ES = 2.17±0.27) and large increases in jump height (+12.4±7.6%; ES = 1.45±0.23). For the VD sub-groups, we observed moderate to extremely large increases in maximal theoretical velocity (+15.8±5.1%; ES = 2.72±0.29), FVimb reduction (-19.2±6.9%; ES = 2.36±0.35) and increases in jump height (+10.1±2.7%; ES = 0.93±0.09). The number of weeks needed to reach the optimal F-v profile (12.6 ± 4.6) was correlated to the magnitude of initial FVimb (r = 0.82, p<0.01) for all participants regardless of their initial subgroup. No significant change in mechanical variables or jump performance was observed over the 3-week de-training period. Conclusions: Collectively, these results provide useful insights into a more specific, individualized (i.e. based on the type and magnitude of FVimb) and accurate training prescription for jumping performance. Considering both training content and training duration together with FVimb may enable more individualized, specific and effective training monitoring and periodization.
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The force-vector theory contends that horizontal exercises are more specific to horizontal sports skills. In this context, the focus is on horizontal force production relative to the global coordinate frame. However, according to the principle of dynamic correspondence, the direction of force relative to the athlete is more important, and thus the basis for the force-vector theory is flawed. The purpose of this study was therefore to test the force-vector theory. According to the force-vector theory, hip thrust is a horizontally loaded exercise, and so hip thrust training would be expected to create greater improvements in horizontal jump performance than vertical jump performance. Eleven collegiate female athletes aged 18–24 years completed a 14-week hip thrust training programme. Pre and post testing was used to measure the following: vertical squat jump, vertical countermovement jump, horizontal squat jump, horizontal countermovement jump and hip thrust 3 repetition maximum (3RM). Subjects improved their 3 repetition maximum hip thrust performance by 33.0% (d = 1.399, p < 0.001, η2 = 0.784) and their vertical and horizontal jump performance (improvements ranged from 5.4–7.7%; d = 0.371–0.477, p = 0.004, η2 = 0.585). However, there were no differences in the magnitude of the improvement between horizontal and vertical jumping (p = 0.561, η2 = 0.035). The results of this study are contrary to the predictions of the force-vector theory. Furthermore, this paper concludes with an analysis of the force-vector theory, presenting the mechanical inconsistencies in the theory. Coaches should use the well established principle of dynamic correspondence in order to assess the mechanical similarity of exercises to sports skills.
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This study aimed (i) to explore the relationship between vertical (jumping) and horizontal (sprinting) force–velocity–power (FVP) mechanical profiles in a large range of sports and levels of practice, and (ii) to provide a large database to serve as a reference of the FVP profile for all sports and levels tested. A total of 553 participants (333 men, 220 women) from 14 sport disciplines and all levels of practice participated in this study. Participants performed squat jumps (SJ) against multiple external loads (vertical) and linear 30–40 m sprints (horizontal). The vertical and horizontal FVP profile (i.e., theoretical maximal values of force ( F0 ), velocity ( v0 ), and power ( Pmax )) as well as main performance variables (unloaded SJ height in jumping and 20-m sprint time) were measured. Correlations coefficient between the same mechanical variables obtained from the vertical and horizontal modalities ranged from −0.12 to 0.58 for F0 , −0.31 to 0.71 for v0 , −0.10 to 0.67 for Pmax , and −0.92 to −0.23 for the performance variables (i.e, SJ height and sprint time). Overall, results showed a decrease in the magnitude of the correlations for higher-level athletes. The low correlations generally observed between jumping and sprinting mechanical outputs suggest that both tasks provide distinctive information regarding the FVP profile of lower-body muscles. Therefore, we recommend the assessment of the FVP profile both in jumping and sprinting to gain a deeper insight into the maximal mechanical capacities of lower-body muscles, especially at high and elite levels.
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Sprinting is a key action in team sports such as Rugby Sevens, a new Olympic sport. Recent research has shown at length the importance of technical or mechanical proficiency for sprinting performance. Simple methods of profiling mechanical characteristics of athletes have been developed utilizing three sprints reaching maximal velocities and demonstrated in a number of elite cohorts. These methods were applied with 16 athletes (age = 23 ± 7 years; height = 1.73 ± 0.82 m; body mass = 69.9 ± 7.2 kg) from the New Zealand Women’s Rugby Sevens team. Mechanical proficiency in the form of horizontal-to-vertical force application ratio (RF) showed strong Pearson’s correlations (r=-0.60 p=0.001, r=-0.61 p=0.002) between 10 m and 40 m sprinting performances, respectively. Further r values (r=>-0.71) were observed for relationships between peak relative horizontal power expression and sprinting performances. This study expands, via a newly observed population, the body of knowledge contending the relationship between mechanical proficiency and sprinting performance and supports the usage of profiling methods to individualizing training for speed and power. Profiling can identify among a cohort whom is “force dominant” and “velocity dominant” as well as simply which athletes are more and less proficient at applying forces efficiently to propel themselves in sprinting actions.
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The aim of this study was to investigate the impact of timing gate setup on mechanical outputs in sprinting athletes. Twenty-five male and female team sport athletes (mean ± SD: 23 ± 4 y, 185 ± 11 cm, 85 ± 13 kg) performed two 40-m sprints with maximal effort. Dual-beamed timing gates covered the entire running course with 5-m intervals. Maximal horizontal force (F0), theoretical maximal velocity (v0), maximal horizontal power (Pmax), force-velocity slope (SFV), maximal ratio of force (RFmax) and index of force application technique (DRF) were computed using a validated biomechanical model and based on twelve varying split time combinations, ranging from three to eight timing checkpoints. When no timing gates were located after the 20-m mark, F0 was overestimated (mean difference, ±90%CL: 0.16, ±0.25 to 0.33, ±0.28 N•kg-1 ; possibly to likely; small), in turn affecting SFV and DRF by small to moderate effects. Timing setups covering only the first 15 m displayed lower v0 than setups covering the first 30-40 m of the sprints (0.21 ±0.34 to 0.25 ±0.34 m•s-1 ; likely; small). Moreover, poorer reliability values were observed for timing setups covering the first 15-20 m vs. the first 25-40 m of the sprints. In conclusion, the present findings showed that the entire acceleration phase should be covered by timing gates to ensure acceptably valid and reliable sprint mechanical outputs. However, only three timing checkpoints (i.e., 10, 20 and 30 m) are required to ensure valid and reliable outputs for team sport athletes.
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The capacity to rapidly generate and apply a great amount of force seems to play a key role in sprint running. However, it has recently been shown that, for sprinters, the technical ability to effectively orient the force onto the ground is more important than its total amount. The force-vector theory has been proposed to guide coaches in selecting the most adequate exercises to comprehensively develop the neuromechanical qualities related to the distinct phases of sprinting. This study aimed to compare the relationships between vertically-directed (loaded and unloaded vertical jumps, and half-squat) and horizontally-directed (hip-thrust) exercises and the sprint performance of top-level track and field athletes. Sixteen sprinters and jumpers (including three Olympic athletes) executed vertical jumps, loaded jump squats and hip-thrusts, and sprinting speed tests at 10-, 20-, 40-, 60-, 100-, and 150-m. Results indicated that the hip-thrust is more associated with the maximum acceleration phase (i.e., from zero to 10-m; r = 0.93), whereas the loaded and unloaded vertical jumps seem to be more related to top-speed phases (i.e., distances superior to 40-m; r varying from 0.88 to 0.96). These findings reinforce the mechanical concepts supporting the force-vector theory, and provide coaches and sport scientists with valuable information about the potential use and benefits of using vertically- or horizontally-based training exercises.
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This study aimed to evaluate whether an individualised sprint-training program was more effective in improving sprint performance in elite team-sport players compared to a generalised sprint-training program. Seventeen elite female handball players (23 +/- 3 y, 177 +/- 7 cm, 73 +/- 6 kg) performed two weekly sprint training sessions over eight weeks in addition to their regular handball practice. An individualised training group (ITG, n = 9) performed a targeted sprint-training program based on their horizontal force-velocity profile from the pre-training test. Within ITG, players displaying the lowest, highest and mid-level force-velocity slope values relative to body mass were assigned to a resisted, an assisted or a mixed sprint-training program (resisted sprinting in the first half and assisted sprinting in the second half of the intervention period), respectively. A control group (CG, n = 8) performed a generalised sprint-training program. Both groups improved 30-m sprint performance by ~ 1% (small effect) and maximal velocity sprinting by ~ 2% (moderate effect). Trivial or small effect magnitudes were observed for mechanical outputs related to horizontal force-or power production. All between-group differences were trivial. In conclusion, individualised sprint-training was no more effective in improving sprint performance than a generalised sprint-training program.
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Forces applied to the ground during sprinting are vital to performance. This study aimed to understand how specific aspects of ground reaction force waveforms allow some individuals to continue to accelerate beyond the velocity plateau of others. Twenty‐eight male sprint specialists and 24 male soccer players performed maximal‐effort 60‐m sprints. A 54‐force‐plate system captured ground reaction forces, which were used to calculate horizontal velocity profiles. Touchdown velocities of steps were matched (8.00, 8.25 and 8.50 m·s⁻¹) and the subsequent ground contact forces were analysed. Mean forces were compared across groups and statistical parametric mapping (t‐tests) assessed for differences between entire force waveforms. When individuals contacted the ground with matched horizontal velocity, ground contact durations were similar. Despite this, sprinters produced higher average horizontal power (15.7‐17.9 W·kg⁻¹) than the soccer players (7.9‐11.9 W·kg⁻¹). Force waveforms did not differ in the initial braking phase (0‐~20% of stance). However, sprinters attenuated eccentric force more in the late braking phase and produced a higher anteroposterior component of force across the majority of the propulsive phase, for example from 31‐82% and 92‐100% of stance at 8.5 m·s⁻¹. At this velocity, resultant forces were also higher (33‐83% and 86‐100% of stance) and the force vector was more horizontally orientated (30‐60% and 95‐98% of stance) in the sprinters. These findings illustrate the mechanisms which allowed the sprinters to continue accelerating beyond the soccer players’ velocity plateau. Moreover, these force production demands provide new insight regarding athletes’ strength and technique training requirements to improve acceleration at high velocity. This article is protected by copyright. All rights reserved.