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Sled Pushing and Pulling to Enhance Speed Capability

February 2019
Strength and Conditioning Journal 41(4):1

DOI:10.1519/SSC.0000000000000460

Authors:

Micheál Cahill

Auckland University of Technology

John Cronin

Auckland University of Technology

Jon Oliver

Cardiff Metropolitan University

Kenneth Clark

University of New Haven

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Resisted sprinting in the form of both sled pushing and pulling is a popular training method to improve speed capability, although research has been biased towards investigating the effects of sled pulling. Practitioners need to understand whether the sled push and pull offer differential training effects, and hence their utility in influencing sprint kinematics and kinetics for targeted adaptation. Furthermore, there are a number of recent developments in loading and assessment that warrant discussion, given the impact of these techniques on understanding the load-velocity relationship and optimizing horizontal power output. Finally, some thoughts regarding load prescription are shared with the reader.

Competitive female sprinter pushing and pulling loads at 33, 66, and 99% BM, respectively. (A) Unresisted sprint, (B) 33% BM sled push, (C) 66% BM sled push, (D) 99% BM sled push, (E) 33% BM sled pull, (F) 66% BM sled pull, and (G) 99% BM sled pull. BM 5 body mass.

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Individual load-speed relationships of 2 different athletes' sled pushing expressed as %BM. %BM 5 percent body mass.

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Figures - uploaded by Micheál Cahill

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Sled Pushing and Pulling

to Enhance Speed

Capability

Michea

´l J. Cahill, MSc,

1,2

John B. Cronin, PhD,

2,3

Jon L. Oliver, PhD,

2,4

Kenneth P. Clark, PhD,

Rhodri S. Lloyd, PhD,

2,4,7

and Matt R. Cross, MSc

2,6

Athlete Training and Health, Plano, Texas;

Sports Performance Research Institute New Zealand, Auckland University

of Technology, Auckland, New Zealand;

School of Medical and Health Sciences, Edith Cowan University, Perth,

Australia;

Cardiff School of Sport and Health Sciences, Wales, United Kingdom;

Department of Kinesiology, West

Chester University, West Chester, Pennsylvania;

Laboratoire Interuniversitaire de Biologie de la Motricite

´, University

Savoie Mont Blanc, Chambe

´ry, France; and

WINTEC, Hamilton, New Zealand

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided

in the HTML and PDF versions of this article on the journal’s Web site (http://journals.lww.com/nsca-scj).

ABSTRACT

RESISTED SPRINTING IN THE

FORM OF SLED PUSHING AND

PULLING ARE POPULAR TRAINING

METHODS TO IMPROVE SPEED

CAPABILITY, ALTHOUGH

RESEARCH HAS BEEN BIASED

TOWARD INVESTIGATING THE EF-

FECTS OF SLED PULLING. PRAC-

TITIONERS NEED TO UNDERSTAND

WHETHER THE SLED PUSH AND

PULL OFFER DIFFERENTIAL TRAIN-

ING EFFECTS, AND HENCE THEIR

UTILITY IN INFLUENCING SPRINT

KINEMATICS AND KINETICS FOR

TARGETED ADAPTATION. FUR-

THERMORE, THERE ARE A NUM-

BER OF RECENT DEVELOPMENTS

IN LOADING AND ASSESSMENT

THAT WARRANT DISCUSSION,

GIVEN THE IMPACT OF THESE

TECHNIQUES ON UNDERSTAND-

ING THE LOAD-VELOCITY RELA-

TIONSHIP AND OPTIMIZING

HORIZONTAL POWER OUTPUT.

FINALLY, SOME THOUGHTS

REGARDING LOAD PRESCRIPTION

ARE SHARED WITH THE READER.

INTRODUCTION

Sprinting is a critical factor neces-

sary for individual and team sport

success (5,13,14,37). The success

of a sprint is determined by the ability

to accelerate, the extent to which max-

imal velocity is achieved, and the abil-

ity to maintain that velocity against the

onset of fatigue (14). Team sports how-

ever such as rugby, Gaelic football, and

Australian football have been shown to

exhibit multiple short-distance acceler-

ations upward of over 100 per game,

typically between 10 and 20 m

(9,16,27,50). In professional soccer

players, the mean duration of sprints

completed during a soccer game is re-

ported to be between 2 and 4 seconds

(52). Given the recurrence of short-

distance acceleration in many common

ﬁeld-based team sports, one could

argue that the development of this

phase outweighs the beneﬁt of time

spent isolating the development of

maximum velocity (e.g., sprint

mechanics) in all but “pure” speed

sporting codes. Horizontal force pro-

duction and the orientation of the force

vector are strong inﬂuencers of an ath-

lete’s ability to accelerate (21,35). Iden-

tifying training methods to improve

horizontal force production and the

orientation of the force vector would

seem important for the improvement

of this motor quality.

Most studies that examine training and

improvements in sprint speed use non-

speciﬁc forms of training, such as

strength, plyometric, or combined

training methods (7,15,17,19,34,40).

Those methods have been shown to

be effective at improving acceleration

and sprint performance (45), which

may be partly due to resistance training

requiring large amounts of force pro-

duction during triple extension of the

lower limbs, replicating movement

mechanics of sprinting. There are

fewer studies that examine sprint-

speciﬁc training, but from the studies

that do exist it has been suggested that

sprint-speciﬁc training transfers greater

gains to acceleration and speed than

nonspeciﬁc training (45). Sprint-

speciﬁc training may include both un-

resisted and resisted forms of sprinting.

Unresisted and light-resisted sprinting

may provide a speed stimulus while

maintaining sprint mechanics (2,25).

Address correspondence to Michea

´l Cahill,

mcahill@athleteth.com.

KEY WORDS:

resisted sled sprinting; sled pushing;

sled pulling; acceleration; horizontal

force; horizontal strength training

Heavy-resisted sprint training will pro-

vide a different stimulus, overloading

force producing capabilities of the ath-

lete (36). Although the lower limbs will

triple extend during vertical resistance

and heavy-resisted sprint training, the

latter will alter the force orientation,

requiring a greater horizontal force

vector that may transfer greater train-

ing gains to free sprinting. However,

until recently, research has focused

more than postpubertal boys. The

sameauthorsalsoreportedinalater

article that although 6 weeks of sled

training improved the speed, stride

length, stride frequency, force, and

power in pubertal boys, it had no ben-

eﬁt for prepubertal boys (46). It is not

clear whether these different acute

and chronic responses are solely

a result of maturation, differences in

the size, strength or training history of

youth, or most likely a combination of

these factors. What is clear is that the

characteristics of an athlete inﬂuence

both the acute and chronic responses

to sled pulling, and therefore, we

would expect the same for sled push-

ing. The available research suggests

that maturity, sex, and training his-

tory are all likely to inﬂuence the

Strength and Conditioning Journal | www.nsca-scj.com 7

ability of an athlete to sprint against

resistance, and this may be under-

pinned by differences in size, relative

strength, and body composition (29).

Although the practitioner should not

assume that the same load as a %BM

will produce the same stimulus in

a push and pull, it should also not

be assumed that the same %BM load

will produce the same stimulus for

athletes of differing characteristics.

Loadsshouldbeprescribedonthe

extent to which velocity is decreased

rather than a set percentage of BM.

Individual athletes will respond to

loading differently. Reductions in

speed with load will also be inﬂu-

enced by the sled design and friction

with any given surface. Although it is

difﬁcult to understand exactly how

each of these factors inﬂuences per-

formance, an approach that pre-

scribes resisted training based on

a given reduction in speed (e.g., 50%

reduction in speed), rather than a set

percentage of body load, should be

better able to provide a consistent

stimulus between athletes and

conditions.

NEW ASSESSMENT PROCEDURES

IN RESISTED SPRINTING

There are a number of devices that

can be used to time sprints such as

photocell-timing gates, radar/laser,

video, and global positioning units

(39). As with all methods of assess-

ment, each has its own limitations,

including cost, complexity of set-up,

analysis, and reliability. Recent advan-

ces in technology, speciﬁcally high-

quality handheld cameras have paved

the way for mobile applications such

as My Sprint app to assess sprint per-

formance based on the research by

Samozino et al. (48). Recent research

(44)foundtheMySprintapptobe

a valid and reliable method to evalu-

ate sprint performance, although the

time required to analyze each athlete

can prove time-consuming in a team

setting compared with the use of tim-

ing gates or radar gun. Such methods

can also be used to determine the

load‐speed relationship during re-

sisted sprints. Assessing the load-

speed relationship for individual ath-

letes can provide coaches with valu-

able feedback for monitoring

performance changes and assessing

loading parameters over resisted

sprint training blocks, for instance to

ensure the load used during training

decreases velocity by a desired

amount (e.g., 50%). Coaches can also

observe the individual differences cer-

tain loads have on an athlete’s body

angle to ensure the desired training

adaptation.

This form of proﬁling an athlete dur-

ing resisted sprinting for load pre-

scription is less common. Alcaraz

et al. (2) developed a regression equa-

tion to optimize sled load in accor-

dance with keeping the athlete’s

maximal velocity above 90% using

a radar gun to assess instantaneous

velocity. Martinez-Valencia et al. (30)

and Petrakos et al. (43) examined the

maximum resisted sled load where an

athlete can no longer accelerate

between 10–15 m and 15–20 m of

a 20-m linear sprint using photocell-

timing gates. Both studies did not

exceed 30% BM during loading. More

recently, sprint time has been used to

construct force-velocity proﬁles dur-

ing unresisted sprinting (48), and that

process has also been applied to sled

pulling (13). The advantage of this

approach is that it allows for determi-

nation of the load and velocity com-

bination that optimizes power

production. Cross et al. (13) assessed

pulling loads between 20 and 120% of

BM. The authors found that the load

to optimize power for recreational

and elite-level sprinters ranged

between 69 and 96% of BM depen-

dent on the individual, but more

importantly load was optimized at

a decrement in velocity of 48–52%

for all athletes. Although %BM has

its limitations for load prescription,

it can give useful general guidelines

to coaches with time constraints and

limited resources. However, simple

measurement of the load-velocity

relationship can allow coaches to

individualize loading to a speciﬁc

velocity decrement and provide

amoretargetedtrainingstimulus.

Coaches and practitioners should

take note of the heavier loading pa-

rameters found by researchers to opti-

mize power production when

planning sled pushing and pulling

training.

During sled pulling, the load-speed

relationship has been shown to be

linear with power optimized at

a Vdec of 50% (13). Although no

Figure 4. Individual load-speed relationships of 2 different athletes’ sled pushing

expressed as %BM. %BM 5percent body mass.

Sled Pushing and Pulling

VOLUME 00 | NUMBER 00 | MONTH 2019

one has speciﬁcally examined power

production during sled pushing, the

load-speed relationship has been

shown to be linear (55). Therefore,

it may be assumed that a parabolic

power relationship would also occur

with power optimized during push-

ing at a load that reduces velocity by

50%. Figure 4 illustrates 2 different

athlete load-velocity proﬁles during

resisted sled pushing; from our anec-

dotal evidence, it is apparent that the

same linear relationship exists.

Applying the principles reported by

Cross et al. (13), practitioners can

measure the load-speed relationship

for each athlete across a range of

loads and use this to identify the load

that decreases speed by 50% and op-

timizes power; this zone is illustrated

in yellow in Figure 4. In the example

showninFigure4,theloadthat

causes 50% decrease in velocity is

75% BM for the athlete A and 55%

BM for athlete B. From this informa-

tion, heavier or lighter loads can be

prescribed based on the individual

characteristics (i.e., force or velocity

dominant) and the training goal. It is

important to note that the load that

optimizes power may not necessarily

be the optimal load that leads to in-

creases in sprint performance. Load

prescription may differ dependent on

the individual, for example, force

dominant athletes may beneﬁt from

higher velocity training and vice ver-

sa. A certain baseline level of strength

(both horizontally and vertically)

may need to be established before

an athlete can truly use loads that

optimize power. Heavier loads that

cause a greater reduction in unre-

sisted speed (.65%) could be viewed

as strength-speed exercises; this zone

is illustrated in red in Figure 4. Ligh-

ter loads that cause less of a reduction

in unresisted speed (,35%) could be

viewed as speed-strength exercises;

this zone is illustrated in green. The

load that causes a reduction of 10% in

maximum velocity has been shown

not to effect sprint mechanics; this

zone is illustrated in blue and could

be used by coaches wishing to add

a loading stimulus without effecting

sprint mechanics.

This type of analysis can offer diag-

nostic information that both inform

adaptation and guide programming,

for example, coaches, practitioners,

and researchers can use such an

approach to make informed deci-

sions on loads prescribed during

training to ensure the desired adap-

tation is achieved. After further anal-

ysis of pre- and post-testing, this

approach can provide insight into

how different forms of resisted sled

training at a given load can alter the

force-velocity proﬁle overtime.

PRACTICAL APPLICATIONS

There is renewed interest in the utility

of resisted sled sprinting methods to

improve speed ability, given the evo-

lution of knowledge around load

(heavy sled work), technique (sled

push), and assessment. However, we

have also stressed to the reader that

there are a number of limitations that

the reader should be cognizant of

when making sense of the application

of research to practice. Practitioners

should consider the following when

prescribing resisted sled pulling and

pushing:

Resisted sled sprinting provides

a stimulus for high horizontal force

application, and when incorporated

into a strength training program, it

might prove to be a more effective

way of improving sprint perfor-

mance compared with unresisted

sprinting or traditional resistance

training alone.

Athlete characteristics, type of sled,

and type of surface will all inﬂuence

the amount of resistance experi-

enced. To help account for this, load-

ing should be prescribed on the

percentage reduction in velocity for

each athlete rather than a set per-

centage of BM.

Reductions in velocity of ,10, ,35,

50, and .65% during resisted sprinting

are suggested to reﬂect high-speed

(technical), speed-strength, power,

and strength-speed stimuli.

Conﬂicts of Interest and Source of Funding:

The authors report no conﬂicts of interest

and no source of funding.

Michea

´lJ.

Cahill is a doc-

toral candidate

at Auckland

University of

Technology and

the vice president

of Performance

and Sports Sci-

ence at Athlete Training and Health.

John B. Cronin

is a professor in

Strength and

Conditioning at

AUT University,

Sports Perfor-

mance Research

Institute New

Zealand.

Jon L. Oliver is

a reader in

Applied Paediat-

ric Exercise Sci-

ence and a co-

founder and

research lead of

the Youth

Physical

Development

Centre at Cardiff Metropolitan

University.

Kenneth P.

Clark is an assis-

tant professor in

the Department

of Kinesiology at

West Chester

University of PA.

Strength and Conditioning Journal | www.nsca-scj.com 9

Rhodri S. Lloyd

is a reader in

Paediatric

Strength and

Conditioning and

the chair and co-

founder of the

Youth Physical Development Centre at

Cardiff Metropolitan University.

Matt R. Cross is

a doctoral candi-

date at the Uni-

versite

´Savoie

Mont Blanc with

the Fe

´de

ration

Franc¸aise de Ski

and a research

associate at the Auckland University of

Technology.

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Strength and Conditioning Journal | www.nsca-scj.com 11

The Acute Effects of Heavy Sled Towing on Acceleration Performance and Sprint Mechanical and Kinematic Characteristics

Article

Full-text available

May 2022

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.

The Assessment and Development of Sprint Performance in Junior Male Australian Football

Thesis

Full-text available

Dec 2021

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.

A multifactorial and individualized approach to reduce hamstring muscle injuries in professional football players.

Thesis

Full-text available

Jan 2022

Johan Lahti

Despite efforts to intervene, hamstring muscle injuries (HMI) continue to be one of the largest epidemiological burdens in professional football. The injury mechanism takes place dominantly during sprinting, but also other scenarios have been observed, such as overstretching actions, jumps, and change of directions. The main biomechanical roles of the hamstring muscles are functioning as an accelerator of center-of-mass (i.e., contributing to horizontal force production), and stabilizing the pelvis and knee joint. Multiple extrinsic and intrinsic risk factors have been identified, portraying the multifactorial nature of the HMI. Furthermore, these risk factors can vary substantially between players, portraying the importance of individualized approaches. However, there is a lack of multifactorial and individualized approaches assessed for validity in literature. Thus, the overarching aim of this doctoral thesis was to explore if a specific multifactorial and individualized approach can improve upon the ongoing HMI risk reduction protocols, and thus, further reduce the HMI risk in professional football players. This was done following the Team-sport Injury Prevention model (TIP model), where the target is to evaluate the current injury burden, identify possible solutions, and intervene. The thesis comprised of three themes within professional football, I) evaluating and identifying HMI risk (completed via assessing the current epidemiological HMI situation and the association between HMI injuries and a novel hamstring screening protocol), II) improving horizontal force capacity (completed via testing if maximal theoretical horizontal force (F0) can be improved via heavy resisted sprint training), and III) developing and conducting a multifactorial and individualized training for HMI risk reduction (completed via introducing and conducting a training intervention). The conclusions from theme I were that the HMI burden continues to be high (14.1 days absent per 1000 hours of football exposure), no tests from the screening protocol were associated with an increased HMI risk when including all injuries from the season (n = 17, p > 0.05), and that lower F0 was significantly associated with increased HMI risk when including injuries between test rounds one and two (~90 days, n =14, hazard ratio: 4.02 (CI95% 1.08 to 15.0), p = 0.04). For theme II, the players initial pre-season level of F0 was significantly associated with adaptation potential after 11 weeks of heavy resisted sprint training during the pre-season (r = -0.59, p < 0.05). The heavy resisted sprint load leading to a ~50% velocity loss induced the largest improvements in sprint mechanical output and sprint performance variables. For theme III, no intervention results could be presented within this document due to the Covid-19 pandemic leading to the intervention being postponed. However, a protocol paper was published, describing in detail the intervention approach that will be used outside the scope of the thesis. In future studies, larger sample size studies are needed to support the development of more advanced HMI risk reduction models. Such models may allow practitioners to identify risk on an individual level instead of a group level. Furthermore, constant development of more specific, reliable, and accessible risk assessment tests should be promoted that can be frequently tested throughout the football season. Finally, based on the results of theme II, individualization of a specific training stimulus should be promoted in team settings.

Training to Improve Pro-Agility Performance: A Systematic Review

Article

Full-text available

Dec 2022
J HUM KINET

Effective directional change in sport is imperative to success in key game situations. Change of direction (COD) ability is underpinned by various athletic qualities which can be developed through specific and non-specific training methods. This review examined the effect of specific and non-specific training methods on pro-agility performance, by analysing the intervention type and resulting magnitude of training effects on pro-agility shuttle performance. A total of 20 studies were included for review. Data from 638 subjects and 29 intervention groups involving seven different training methods were extracted and analysed in relation to training method classification and primary outcome measures. Interventions involving sprint training, plyometric training, resistance training, and combined resistance, plyometric, and sprint training were found to produce statistically significant positive change on pro-agility performance per session (p < 0.05). Sprint training (0.108 ES), plyometric training (0.092 ES), resistance training (0.087 ES), and combined resistance, plyometric, and sprint training (0.078 ES) methods were found to have the highest per session training effect. While total time is the typical unit of measure for this test, different types of training may lead to preferential improvements in either acceleration, deceleration, or COD phases of the pro-agility shuttle. Specifically, resisted or inclined sprinting may develop the linear acceleration phases, unilateral resistance training may promote increased strength to overcome the imposed forces during the deceleration and COD phases, multiplanar plyometrics can help enhance stretch-shortening cycle capabilities across different force vectors, and a combination of two or more of these methods may enable simultaneous development of each of these qualities.

Biomechanical and Neuromuscular Performance Requirements of Horizontal Deceleration: A Review with Implications for Random Intermittent Multi-Directional Sports

Article

Full-text available

May 2022
SPORTS MED

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.

Narrative Review on the Use of Sled Training to Improve Sprint Performance in Team Sport Athletes

Article

May 2022
Strength Condit J

Sprinting is a key component for many individual and team sports. Therefore, to enhance sprint performance, various training methods are widely used by coaches and practitioners, including maximum sprint speed and resisted sprint training. Resisted sprinting with sled towing is a method that has recently received considerable attention from the sport science community. However, to date, no consensus exists regarding its acute and chronic effects in team sport athletes. This narrative review aimed to (a) review and analyze the mechanics of sprinting under unresisted and resisted conditions with a specific focus on team sport disciplines; (b) provide a thorough and applied discussion on the importance of considering acute and chronic effects of sled loading on technique, electromyographic activity, and force production, as well as on the role of muscle architecture and neural factors in sled training; (c) analyze the effects of increasing sled loads during acceleration and maximum velocity phases on contact and flight phases, while concomitantly examining kinetic, kinematic, and neuromuscular aspects, because all these factors affect each other and cannot be properly understood in isolation.

Development, evaluation and application of a novel markerless motion analysis system to understand push-start technique in elite skeleton athletes

Article

Full-text available

Nov 2021
PLOS ONE

This study describes the development, evaluation and application of a computer vision and deep learning system capable of capturing sprinting and skeleton push start step characteristics and mass centre velocities (sled and athlete). Movement data were captured concurrently by a marker-based motion capture system and a custom markerless system. High levels of agreement were found between systems, particularly for spatial based variables (step length error 0.001 ± 0.012 m) while errors for temporal variables (ground contact time and flight time) were on average within ± 1.5 frames of the criterion measures. Comparisons of sprinting and pushing revealed decreased mass centre velocities as a result of pushing the sled but step characteristics were comparable to sprinting when aligned as a function of step velocity. There were large asymmetries between the inside and outside leg during pushing (e.g. 0.22 m mean step length asymmetry) which were not present during sprinting (0.01 m step length asymmetry). The observed asymmetries suggested that force production capabilities during ground contact were compromised for the outside leg. The computer vision based methods tested in this research provide a viable alternative to marker-based motion capture systems. Furthermore, they can be deployed into challenging, real world environments to non-invasively capture data where traditional approaches are infeasible.

Practice to pitch: The relationship between force-velocity profiles and match-day performance of semi-professional rugby union players

Article

Full-text available

Mar 2023

Introduction: This exploratory study aimed to assess the relationship between athlete neuromuscular performance and rugby performance indicators. Specifically, the study looked at the force-velocity profiles (FVPs) derived from four common resistance exercises and their relationship with rugby performance indicators (RPIs). Methods: The study recruited twenty-two semi-professional male rugby players (body mass 102.5 ± 12.6 kg, height 1.85 ± 0.74 m, age 24.4 ± 3.4 years) consisting of ten backs and twelve forwards. Prior to the first game of a Covid-impacted nine-match season, participants performed four common resistance exercises (barbell box squat, jammer push-press, sled pull, and sled push) at incremental loads to establish force-velocity profiles. During the season, rugby performance indicators (post-contact metres, tries, turnovers conceded, tackles, try assists, metres ran, defenders beaten, and tackle breaks) were collated from two trusted sources by a performance analyst. Correlational analyses were used to determine the relationship between the results of FVPs and RPIs. Results: The study found a statistically significant, moderate, positive correlation between tackle-breaks and sled push V0 (r = .35, p = .048). Significant, large, positive correlations were also found between tackles and jammer push-press V0 (r = .53, p = .049) and tackle-breaks and sled pull F0 (r = .53, p = .03). There was a significant, negative relationship between sled pull V0 and tackle-breaks (r = −.49, p = .04). However, the largest, significant correlation reported was between metres ran and sled pull F0 (r = .66, p = .03). Conclusion: The study suggests that a relationship may exist between FVPs of particular exercises and RPIs, but further research is required to confirm this. Specifically, the results suggest that horizontal resistance training may be best to enhance RPIs (tackle-breaks, tackles, and metres ran). The study also found that maximal power was not related to any rugby performance indicator, which suggests that a specified prescription of either force or velocity dominant exercises to enhance RPIs may be warranted.

Sportspiele – Leistungsfaktoren

Chapter

Feb 2023

Leonie Schwertmann, Nike Lorenz, Timo Boll, Joshua Kimmich, Leon Draisaitl, Uwe Gensheimer oder Angelique Kerber gelingt es scheinbar mühelos, ungewöhnliche, aber auch technisch-taktische Bestlösungen auf dem Spielfeld zu generieren, ganz nach dem Motto: „Just do it!“ Nicht allen Sportlern, unabhängig von ihrem Leistungsniveau, gelingt es aber, optimale motorische Entscheidungshandlungen unter höchstem Zeit-, Präzisions-, Variabilitäts- Belastungs- und Gegnerdruck zu treffen. Hier stellt sich für viele Lehrer und Trainer die Aufgabe, Fehlerquellen angemessen zu analysieren, sie vergleichend zu diagnostizieren und sie abschließend effektiv durch Training zu beheben.

Neuromuscular Determinants of Horizontal Deceleration Ability in Team Sport Athletes: Performance and Injury Risk Implications

Thesis

Full-text available

Jan 2023

Damian Harper

Horizontal accelerations and decelerations are crucial components underpinning the many fast changes of speed and direction that are performed in team sports competitive match play. Extensive research has been conducted into the assessment of horizontal acceleration and the underpinning neuromuscular performance determinants, leading to evidence-informed guidelines on how to best develop specific components of a team sport players horizontal acceleration capabilities. Unlike horizontal acceleration, little scientific research has been conducted into how to assess horizontal deceleration, meaning the neuromuscular performance determinants underpinning horizontal deceleration are largely based on anecdotal opinion or qualitative observations. Therefore, the overall purpose of this thesis was to investigate the neuromuscular determinants of maximal horizontal deceleration ability in team sport players. Furthermore, since there are no recognised procedures on how to assess maximal horizontal deceleration ability, an important and novel aim of this thesis was to develop a test capable of obtaining reliable and sensitive data on a team sport player’s maximal horizontal deceleration ability. In part one of this thesis (chapter three) a systematic review and meta-analysis identified that high-intensity (< -2.5 m.s-2) decelerations were more frequently performed than equivalently intense accelerations (> 2.5 m.s-2) in most elite team sports competitive match play, signifying the importance of developing maximal horizontal deceleration ability in team sport players. In chapter four, a new test of maximal horizontal deceleration ability (named the acceleration-deceleration ability test – ADA test), measured using radar technology, identified a number of kinematic and kinetic variables that had good intra- and inter-day reliability and were sensitive to detecting small-to-moderate changes in maximal horizontal deceleration ability. The ADA test was used in chapters five to seven to examine associations with isokinetic eccentric and concentric knee strength capacities and countermovement and drop jump kinetic and kinematic variables, respectively. Using the neuromuscular and biomechanical determinants identified to be important for horizontal deceleration ability within this thesis, in addition to other contemporary research findings, the final part of this thesis developed an evidence-based framework that could be used by practitioners to help inform decisions on training solutions for improving horizontal deceleration ability – named the dynamic braking performance framework.

MODERATE RUNNING AND PLYOMETRIC TRAINING DURING OFF-SEASON DID NOT SHOW A SIGNIFICANT DIFFERENCE ON SOCCER-RELATED HIGH-INTENSITY PERFORMANCES COMPARED WITH NO-TRAINING CONTROLS

Article

Full-text available

May 2018

Reliability of the Maximal Resisted Sprint Load Test and Relationships With Performance Measures and Anthropometric Profile in Female Field Sport Athletes

Article

Full-text available

Jun 2019

Resisted sled sprint (RSS) training is an effective modality for the improvement of linear sprint speed. Previous methods of RSS load prescription e.g. an absolute load or as a percentage of body mass (%BM), do not account for inter-individual differences in strength, power or speed characteristics, although the 'maximum resisted sled load' (MRSL) method of RSS load prescription may provide a solution. MRSL is defined as the final RSS load before an athlete can no longer accelerate between two phases (10-15 m and 15-20 m) of a 20 m linear sprint. However, the MRSL test has not been analysed for reliability. Additionally, MRSL performance has not been compared to the outcome of other performance tests. The primary aim of this study was to investigate the reliability of the MRSL testing protocol in female field sport athletes. Participants (age, 20.8 ± 1.9 y; body mass, 64.3 ± 8.4 kg; height, 1.66 ± 0.65 m) tested for anthropometric measurements, strength and power performance testing and twice for MRSL. MRSL values ranged from 20.7 to 58.9%BM. MRSL test-retest reliability intraclass correlation coefficient, confidence intervals and coefficient of variations were 0.95, 0.85-0.98 and 7.6%, respectively. MRSL was 'moderately' and 'strongly' correlated with a number of anthropometric and performance tests (p < 0.05) including % fat free mass, countermovement jump, loaded countermovement jump, rate of force development, horizontal jump and horizontal bound performance. MRSL is a reliable measure for determining the RSS load at which an individual can no longer accelerate during a single RSS effort over 0-20 m. MRSL also accounts for inter-individual variation in body composition, power and speed characteristics of female field sport players.

Sled Towing Acutely Decreases Acceleration Sprint Time

Article

Full-text available

Nov 2017

Sled towing is a common form of overload training in sports to develop muscular strength for sprinting. This type of training leads to acute and chronic outcomes. Acute training potentially leads to postactivation potentiation (PAP), which is when subsequent muscle performance is enhanced following a preload stimulus. The purpose of this study was to determine differences between rest intervals following sled towing on acute sprint speed. Twenty healthy recreationally trained males (age= 22.3 ± 2.4yrs, height= 176.95 ± 5.46 cm, mass= 83.19 ± 11.31 kg) who were currently active in a field sport twice a week for the last six months volunteered to participate. A maximal 30 meter (m) baseline body mass (BM) sprint was performed (with splits at 5, 10, 20 and 30m) followed by 5 visits where participants sprinted 30m towing a sled at 30% BM then rested for 2, 4, 6, 8 or 12min. They were instructed to stand still during rest times. After the rest interval, they performed a maximal 30m post-test BM sprint. ANOVA revealed that post sled tow BM sprint times (4.47±0.21s) were less than baseline times (4.55±0.18s) on an individualized rest interval basis. A follow up 2x4 ANOVA showed that this decrease occurred only in the acceleration phase over the first 5m (BL=1.13±0.08s vs Best= 1.08±0.08s) which may be the result of PAP and the complex relationship between fatigue and potentiation relative to the intensity of the sled tow and the rest interval. Therefore, coaches should test their athletes on an individual basis to determine optimal rest time following a 30m 30% BM sled tow to enhance acute sprint speed.

Effect of strength-to-weight ratio on the time taken to perform a sled-towing exercise

Article

Full-text available

Jun 2017

Sled-towing exercisesare effective at developing sprint acceleration in sports. In a sled-towingexercise the time taken by an athlete to tow the sled over a given distance isaffected by the weight of the sled, the frictional properties of the runningsurface, and the physiological capacities of the athlete. To accurately set thetraining intensity for an athlete, the coach needs a detailed understanding ofthe relationships between these factors. Our study investigated therelationship between the athlete's strength-to-weight ratioand the rate of increase in sled-towing time with increasing sled weight. Twenty-two male athletes performed aone-repetition maximum (1RM) half-squat and sled-towing exercises over 20 mwith sleds of various weights. The strength of the correlation between 1RM half-squat performance (normalized to bodyweight)and the rate of increase in sled-towing time with increasing sled weight was interpreted using the Pearson product-moment correlationcoefficient. As expected, we found substantialinter-athlete differences in the rate of increase in time with increasing sledweight, with a coefficient of variation of about 21% and 17% for sled-towingtimes over 10 and 20 m, respectively. However, the rate of increase in sled-towing time showed nocorrelation with normalized 1RM half-squat performance (r = -0.11, 90% confidence interval = -0.45 to 0.26; and r = -0.02, 90% confidence interval =-0.38 to 0.34, for sled-towing times over 10 and 20 m, respectively). Theseresults indicate thatinter-athlete differences in the rate of increase in sled-towingtime with increasing sled weight are not likely to be due to differences instrength-to-weight ratio. Instead,we recommend the weight of the sled be scaled according to the athlete'spower-to-weight ratio.

Optimal Loading for Maximizing Power During Sled-Resisted Sprinting

Article

Full-text available

Dec 2016
Int J Sports Physiol Perform

Purpose: To ascertain whether force-velocity-power relationships could be compiled from a battery of sled-resisted overground sprints and to clarify and compare the optimal loading conditions for maximizing power production for different athlete cohorts. Methods: Recreational mixed-sport athletes (n = 12) and sprinters (n = 15) performed multiple trials of maximal sprints unloaded and towing a selection of sled masses (20-120% body mass [BM]). Velocity data were collected by sports radar, and kinetics at peak velocity were quantified using friction coefficients and aerodynamic drag. Individual force-velocity and power-velocity relationships were generated using linear and quadratic relationships, respectively. Mechanical and optimal loading variables were subsequently calculated and test-retest reliability assessed. Results: Individual force-velocity and power-velocity relationships were accurately fitted with regression models (R2> .977, P < .001) and were reliable (ES = 0.05-0.50, ICC = .73-.97, CV = 1.0-5.4%). The normal loading that maximized peak power was 78% ± 6% and 82% ± 8% of BM, representing a resistance of 3.37 and 3.62 N/kg at 4.19 ± 0.19 and 4.90 ± 0.18 m/s (recreational athletes and sprinters, respectively). Optimal force and normal load did not clearly differentiate between cohorts, although sprinters developed greater maximal power (17.2-26.5%, ES = 0.97-2.13, P < .02) at much greater velocities (16.9%, ES = 3.73, P < .001). Conclusions: Mechanical relationships can be accurately profiled using common sled-training equipment. Notably, the optimal loading conditions determined in this study (69-96% of BM, dependent on friction conditions) represent much greater resistance than current guidelines (~7-20% of BM). This method has potential value in quantifying individualized training parameters for optimized development of horizontal power.

Determining friction and effective loading for sled sprinting

Article

Full-text available

Nov 2016

Understanding the impact of friction in sled sprinting allows the quantification of kinetic outputs and the effective loading experienced by the athlete. This study assessed changes in the coefficient of friction (µk) of a sled sprint-training device with changing mass and speed to provide a means of quantifying effective loading for athletes. A common sled equipped with a load cell was towed across an athletics track using a motorised winch under variable sled mass (33.1–99.6 kg) with constant speeds (0.1 and 0.3 m · s−1), and with constant sled mass (55.6 kg) and varying speeds (0.1–6.0 m · s−1). Mean force data were analysed, with five trials performed for each condition to assess the reliability of measures. Variables were determined as reliable (ICC > 0.99, CV < 4.3%), with normal-force/friction-force and speed/coefficient of friction relationships well fitted with linear (R2 = 0.994–0.995) and quadratic regressions (R2 = 0.999), respectively (P < 0.001). The linearity of composite friction values determined at two speeds, and the range in values from the quadratic fit (µk = 0.35–0.47) suggested µk and effective loading were dependent on instantaneous speed on athletics track surfaces. This research provides a proof-of-concept for the assessment of friction characteristics during sled towing, with a practical example of its application in determining effective loading and sled-sprinting kinetics. The results clarify effects of friction during sled sprinting and improve the accuracy of loading applications in practice and transparency of reporting in research.

Very-Heavy Sled Training for Improving Horizontal Force Output in Soccer Players

Article

Full-text available

Nov 2016

Background: Sprint running acceleration is a key feature of physical performance in team sports, and recent literature shows that the ability to generate large magnitudes of horizontal ground-reaction force and mechanical effectiveness of force application are paramount. The authors tested the hypothesis that very-heavy loaded sled sprint training would induce an improvement in horizontal-force production, via an increased effectiveness of application. Methods: Training-induced changes in sprint performance and mechanical outputs were computed using a field method based on velocity-time data, before and after an 8-wk protocol (16 sessions of 10- × 20-m sprints). Sixteen male amateur soccer players were assigned to either a very-heavy sled (80% body mass sled load) or a control group (unresisted sprints). Results: The main outcome of this pilot study is that very-heavy sled-resisted sprint training, using much greater loads than traditionally recommended, clearly increased maximal horizontal-force production compared with standard unloaded sprint training (effect size of 0.80 vs 0.20 for controls, unclear between-groups difference) and mechanical effectiveness (ie, more horizontally applied force; effect size of 0.95 vs -0.11, moderate between-groups difference). In addition, 5-m and 20-m sprint performance improvements were moderate and small for the very-heavy sled group and small and trivial for the control group, respectively. Practical Applications: This brief report highlights the usefulness of very-heavy sled (80% body mass) training, which may suggest value for practical improvement of mechanical effectiveness and maximal horizontal-force capabilities in soccer players and other team-sport athletes. Results: This study may encourage further research to confirm the usefulness of very-heavy sled in this context.

Sprint performance and mechanical outputs computed with an iPhone app: Comparison with existing reference methods

Article

Full-text available

Nov 2016
EUR J SPORT SCI

The purpose of this study was to assess validity and reliability of sprint performance outcomes measured with an iPhone application (named: MySprint) and existing field methods (i.e. timing photocells and radar gun). To do this, 12 highly trained male sprinters performed 6 maximal 40-m sprints during a single session which were simultaneously timed using 7 pairs of timing photocells, a radar gun and a newly developed iPhone app based on high-speed video recording. Several split times as well as mechanical outputs computed from the model proposed by Samozino et al. [(2015). A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running. Scandinavian Journal of Medicine & Science in Sports. https://doi.org/10.1111/sms.12490] were then measured by each system, and values were compared for validity and reliability purposes. First, there was an almost perfect correlation between the values of time for each split of the 40-m sprint measured with MySprint and the timing photocells (r=0.989–0.999, standard error of estimate=0.007–0.015 s, intraclass correlation coefficient (ICC)=1.0). Second, almost perfect associations were observed for the maximal theoretical horizontal force (F0), the maximal theoretical velocity (V0), the maximal power (Pmax) and the mechanical effectiveness (DRF – decrease in the ratio of force over acceleration) measured with the app and the radar gun (r= 0.974–0.999, ICC=0.987–1.00). Finally, when analysing the performance outputs of the six different sprints of each athlete, almost identical levels of reliability were observed as revealed by the coefficient of variation (MySprint: CV=0.027–0.14%; reference systems: CV=0.028–0.11%). Results on the present study showed that sprint performance can be evaluated in a valid and reliable way using a novel iPhone app.

A sled push stimulus potentiates subsequent 20-m sprint performance

Article

Jan 2017

Objectives: The objective of this study was to examine the potentiating effects of performing a single sprint-style sled push on subsequent unresisted 20m sprint performance. Design: Randomized crossover design. Methods: Following a familiarization session, twenty rugby league players performed maximal unresisted 20m sprints before and 15s, 4, 8 and 12min after a single sled push stimulus loaded with either 75 or 125% body mass. The two sled push conditions were performed in a randomized order over a one-week period. The fastest sprint time recorded before each sled push was compared to that recorded at each time point after to determine the post-activation potentiation (PAP) effect. Results: After the 75% body mass sled push, sprint time was 0.26±1.03% slower at the 15s time point (effect size [ES]=0.07) but faster at the 4 (-0.95±2.00%; ES=-0.22), 8 (-1.80±1.43%; ES=-0.42) and 12 (-1.54±1.54%; ES=-0.36)min time points. Sprint time was slower at all the time points after the 125% body mass sled (1.36±2.36%-2.59±2.90%; ESs=0.34-0.64). Conclusions: Twenty-meter sprint performance is potentiated 4-12min following a sled push loaded with 75% body mass while it is impaired after a 125% body mass sled. These results are of great importance for coaches seeking to potentiate sprint performance with the sled push exercise.

Post Activation Potentiation in North American High School Football Players

Article

Dec 2016

Sled Pushing and Pulling to Enhance Speed Capability

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