In a previous post, written for Science of Multi-Directional Speed, I highlighted the very high forces that are generated across very short time frames (i.e., impulse) when decelerating rapidly. I also highlighted the necessity to be able to skilfully attenuate and distribute these forces throughout the muscles and connective tissue structures of the lower limbs to help reduce likelihood of tissue damage and neuromuscular fatigue. This could be done by enhancing two key modifiable factors 1) horizontal deceleration skill and 2) horizontal deceleration specific strength qualities (Harper & Kiely, 2018). A notable strength quality that could help to increase the ability to generate braking impulse and mitigate extent of tissue damage and neuromuscular fatigue is eccentric strength (Harper, McBurnie, et al., 2022). The importance of this strength quality for attaining faster reductions in whole-body momentum, whilst maintaining neuromuscular control and stability of the knee joint during the preparatory deceleration phase of a sharp change of direction (COD), has also been highlighted. Therefore, understanding how eccentric strength can be developed is significantly important to a range of athletes involved in multi-directional sports and for sport science and medicine practitioners who are tasked with the responsibility of ensuring optimal preparation of athletes to meet the demands of competition.
What is eccentric strength?
Firstly, from a physiological perspective an eccentric muscle contraction is one that is actively lengthened through external forces, and thus absorbs or produces negative work (Herzog, 2018). It is also important to note that a ‘contraction’ is defined as a muscle that “undergoes activation and generates force”, which can therefore be applicable for muscle contractions that involve both muscle shortening (i.e., concentric) and lengthening (i.e., eccentric) (Faulkner, 2003). It is well known that eccentric muscle contractions are capable of generating much higher forces than concentric muscle contractions (~40%), with this magnitude becoming larger with increasing joint angular velocities (Nuzzo et al., 2023). This maybe explains why quicker changes in velocity across shorter timeframes and distances can be obtained when decelerating compared to accelerating (Gray et al., 2020; Varley et al., 2012).
For the purpose of helping to understand the use of the term ‘eccentric strength’ and avoid potential confusion with the use of this term, it is important to distinguish between an eccentric muscle contraction and an eccentric strengthening exercise, since eccentric strengthening exercises can involve a diverse combination of both shortening and lengthening muscle contractions (i.e., not just an isolated eccentric contraction) resulting in unique physiological adaptations (Tecchio et al., 2024).
Eccentric strength training should not be considered “a single entity”, rather there are a multitude of “different recipes” which are “not the same dish”
For the purposes of this blog, an eccentric strengthening exercise is any exercise that aims to develop the ability to coordinate the generation and attenuation of forces when required to unload and brake (i.e., decelerate) centre of mass downward motion in any movement direction (i.e., eccentric strength). This definition, therefore, also encompasses horizontal deceleration as an important eccentric strengthening exercise. Eccentric strengthening exercises can be performed with a variety of resistance training modalities (Franchi & Maffiuletti, 2019) and executed using a variety of techniques (Handford et al., 2024). Therefore, eccentric strength training should not be considered “a single entity”, rather there are a multitude of “different recipes” which are “not the same dish” (Franchi & Maffiuletti, 2019)! Accordingly, eccentric strength is likely specific to the eccentric strength exercise being performed, due to the varying skills required when performing eccentric strengthening exercises with different training modes, equipment types, execution strategies and movement directions.
So, the key points so far are:
- Eccentric strength development is critical for enhancing horizontal deceleration ability.
- Eccentric muscle contractions may not always occur during an eccentric strengthening exercise.
- Eccentric strength can be defined as the ability to coordinate the generation and attenuation of forces when required to unload and brake (i.e., decelerate) centre of mass downward motion in any movement direction.
- There are a huge variety of eccentric strengthening exercises that practitioners can choose from to develop a range of eccentric strength qualities.
What eccentric strength qualities are required for horizontal deceleration?
Let’s start by taking a closer look at the skill of horizontal deceleration and acknowledge that this is a complex multi-step movement skill with each braking step having unique physiological and biomechanical demands (Figure xx).
Looking at the kinogram in Figure 1 we can see that this athlete took six braking steps to decelerate his momentum following a 20m sprint. Notably, we can also see that each braking step had different ground contact times, requiring braking force to be generated across different time periods (i.e., impulse). We can also see in the early braking steps that the athlete is applying the brakes with single limb support and that there is a much greater flight time for muscles to pre-activate in readiness for the next braking step. Lastly, we can also see that the early braking steps, demand for braking to be performed with a more extended limb posture and with less joint flexion range of motion than the later braking steps. So, looking at these unique braking step demands, it is highly likely that different eccentric strength qualities are required for different braking steps. Indeed, a very interesting finding identified in some of my previous research was that drop jump reactive strength index (DJ-RSI) had a much greater association with the early deceleration phase than the later deceleration phase (Harper, Cohen, et al., 2022). This is perhaps not surprising as the early deceleration phase comprises the braking steps that have the shortest ground contract times, most extended limb postures and a preparatory time where the muscles must pre-activate prior to ground contact. These characteristics are similar to those seen during the drop jump task. Therefore, those who can generate greater DJ-RSI may have greater “stretch-load” capacity of the muscle-tendon unit (Young, 1995) and be more capable of counteracting the high eccentric-braking forces associated with braking in the early deceleration phase. Importantly, from a performance perspective these players are also perhaps more likely to be able to brake quickly from higher sprinting speeds, thereby generating quicker reductions in whole body momentum (Harper, Cohen, et al., 2022).
Based on studies that have investigated the influence of various biomechanical and neuromuscular qualities on horizontal deceleration ability a summary of the deterministic factors is illustrated in Figure 2.
From an eccentric strength training perspective, we can see that Figure 2 identifies three different eccentric strength qualities (highlighted in blue) that are important to target for improved horizontal deceleration ability. These include:
- Eccentric peak force
- Eccentric velocity
- Eccentric rate of force development
Selecting Eccentric Strength Training Exercises to Improve Horizontal Deceleration Ability?
So, what eccentric strength training exercises can I select to improve horizontal deceleration ability? This is obviously a very important question to consider, but one which is also influenced by many other factors, such as the equipment you have available, the level and age of athlete you are working with, and of course the specific eccentric strength training adaptations you are targeting. From an equipment perspective there are a range of eccentric strength training modalities that can be used to increase the ability to generate force across a variety of movement speeds when performing eccentric exercises (Figure 3).
Figure 3 illustrates the four main categories of eccentric strength training modalities, and the respective equipment options and training methods that could be selected and implemented with your athletes. These include (1) variable, (2) isokinetic, (3) isoweight and (4) isoinertial eccentric training modalities (Coratella et al., 2019; Franchi & Maffiuletti, 2019). Importantly, horizontal decelerations are included as a variable eccentric strength training method that can be easily implemented in a field-based environment with minimal equipment and time demands. Variable eccentric strength training is unique compared to the other eccentric strength training modalities in that it requires precise and rapid modification of muscle tensions and forces in order to optimise locomotor kinematics and reduce the likelihood of eccentrically induced muscle strains (Coratella et al., 2019). Furthermore, horizontal decelerations can impose very high joint angular velocities that may not be possible to attain with other eccentric strength training modalities. For example, joint angular velocities of around 480 and 470°/s have been reported at the ankle and knee respectively during maximal horizontal decelerations (Jordan et al., 2021), highlighting the fast eccentric strength training potential of this exercise modality.
To further aid in selection of eccentric strength training methods for enhancing horizontal deceleration, practitioners should also consider specificity of exercise selection. The Braking Performance Framework provides a continuum of training methods that move on a continuum from local (i.e., braking elementary exercises) to global (i.e., braking performance exercises) specificity, focusing on either upgrading braking specific tissue structural and functional properties (i.e., local specificity) or coordination skills (i.e., global specificity) (Harper, 2023). For the purpose of this blog, the Braking Performance Framework is presented with just the eccentric strength training methods illustrated (Figure 4). For a full illustration and description of all training methods within the BPF, readers should refer to Chapter 5 in the book ‘Multi-Directional Speed in Sport: Research to Application’.
The Braking Performance Framework in Figure 4 contains three exercise categories: (1) Braking Elementary Exercises, (2) Braking Developmental Exercises and, (3) Braking Performance Exercises. Whilst there a wide range eccentric strength training exercises that could be deployed for each eccentric strength training method, for the purpose of this blog I will provide one example of each.
Braking Elementary Exercises
A key focus of the Braking Elementary Exercises is to target specific adaptations to muscle-tendon neuromechanical structural properties to enable players to produce and tolerate higher horizontal braking forces that must be counteracted and controlled by high internal (i.e., muscle) forces. Eccentric strength training is a potent stimulus for enhancing muscle-tendon neuromechanical function (e.g., strength, power, stiffness, stretch-shortening cycle) and for signalling positive structural adaptations (e.g., muscle and tendon cross-sectional area, type II fast-twitch muscle fibre size) (Douglas et al., 2017). Therefore, eccentric strength training methods are pivotal to the Braking Elementary Exercise category, along with other exercise categories within the Braking Performance Framework. Eccentric strength training methods within this category include: (1) high eccentric loading, (2) pre-planned horizontal decelerations, (3) assisted horizontal braking steps, and (4) eccentric landing control.
High Eccentric Loading
The different eccentric exercise modalities and training methods illustrated in Figure 3 can be used to prescribe high eccentric loading. One example is the use of isoinertial eccentric training through the use of flywheel training devices were inertia generated in the concentric propulsive phase of the movement must be subsequently decelerated with a high braking action during the eccentric phase on every repetition of the set (Raya-González et al., 2021). There is general consensus that the stimulus provided by flywheel training can lead to enhanced braking capabilities and thus better deceleration and change of direction performances. Figure 5 illustrates unilateral flywheel exercises being performed with emphasis on braking in both vertical (Figure 5A) and horizontal (Figure 5B) directions. The use of unilateral braking exercises will help to facilitate deceleration and COD performance from both limbs, which might not be achieved when using bilateral vertical flywheel exercises (Núñez et al., 2018).
Pre-Planned Horizontal Decelerations without a Change of Direction
Pre-planned horizontal decelerations without a COD require the athlete to reduce and/or stop momentum in various body positions (i.e., parallel stance, split stance, quarter turn stance, half turn stance, single leg stance), and can be performed from different movement directions (i.e., forwards, sideways, backward). An advantage of using pre-planned horizontal decelerations is that intensity can be systematically progressed or regressed by manipulating either, or both, the velocity and distance at which the deceleration is commenced, or the intensity at which the subsequent deceleration is performed (Dos’Santos et al., 2018). Higher approach velocities (i.e., greater forward momentum) prior to deceleration are reflected in greater deceleration distances and the necessity for more braking steps to reduce momentum (Graham-Smith et al., 2018; Hader et al., 2016). The deceleration demands can also be manipulated by changing the percentage of maximum sprinting velocity (i.e., momentum) at which the deceleration is performed. Figure 6 illustrates horizontal deceleration ‘runways’ allowing a progressive increase in sprinting speed to be attained prior to commencing deceleration. Deceleration zones can also be manipulated to change the intensity of the subsequent deceleration being performed.
Assisted Horizontal Braking Steps
Assisted horizontal braking steps are performed at slower movement velocities with higher assisted (pulling) forces to prolong the time in which braking forces are applied (Mendiguchia et al., 2013). Assisted horizontal braking steps can be performed across a pre-determined distance or a number of steps with assisted force generated via low-cost equipment (e.g., elastic bands, Figure 7) or more precisely programmed using a motorised resistance device (Eriksrud et al., 2022). It is also important to acknowledge that from a fatigue management perspective assisted horizontal braking steps do not require the athlete to generate the propulsive impulses required to accelerate to a desired velocity to subsequently decelerate from.
Eccentric Landing Control
Eccentric landing control exercises aim to develop the neuromuscular qualities required to safely attenuate the forces emanating from foot-ground impact when landing from various lunging, jumping, hopping and bounding tasks, while reinforcing optimal neuromuscular control and movement quality to reduce risk of injuries such as anterior cruciate ligament rupture. To further augment eccentric-braking forces and impact attenuation demands, additional resistance can be generated using equipment such as dumbbells or elastic bands. For example, significant increases in horizontal braking ground reaction forces, with no accompanying increase in vertical ground reaction forces, have been observed in a horizontal hop and hold exercise with cable pulley-assisted loads progressing from 4, 8, 12 and 16% body mass (Cronin et al., 2016). Figure 8 illustrates horizontal hop and hold performed with elastic band assistance.
Braking Developmental Exercises
The key aim of the braking developmental exercises is to increase the ability to produce high net braking forces in less time (i.e., ‘tall-thin’ braking impulse). Eccentric training methods within the braking developmental exercise category include 1) fast eccentric loading, 2) pre-planned horizontal decelerations with COD, and 3) assisted horizontal decelerations.
Fast Eccentric Loading
Training approaches for fast eccentric loading include 1) plyometrics (i.e., jumping, bounding and hopping with slow (>0.25 s) and fast (<0.25 s) stretch-shortening cycle demands), 2) Olympic lifting derivatives (i.e., drop snatch, clean, jump shrug), and those described by Handford et al. (2024) for increasing eccentric velocities (i.e., deceleration demands) such as 3) plyometric accelerated and accentuated eccentric loading (i.e., bands/weights are used to accelerate/accentuate eccentric phase respectively before being released immediately prior to concentric phase). Figure 9 illustrates an example of an accelerated eccentric loading jump squat, with the goal of accelerating downward motion to increase braking rate of force development prior to performing the concentric phase of the jump.
Pre-Planned Horizontal Decelerations with a Change of Direction
During a pre-planned COD task the deceleration demands are both angle and velocity dependent (Dos’Santos et al., 2018). Greater COD angles and higher approach velocities prior to COD will require a higher magnitude of horizontal braking impulse to decelerate forward momentum, resulting in higher lower limb mechanical loading demands and potential injury risks, particularly at the knee (Dos’Santos et al., 2018). Accordingly, for horizontal deceleration training and improving braking force capabilities, there is a need to focus on COD angles that require significant horizontal deceleration prior to turning. Dos Santos et al. (2018) illustrated this using a traffic light system with COD angles greater than 60° requiring substantial braking (i.e., red light) across a number of braking steps prior to turning and re-accelerating in a new direction. Practitioners should also be aware many sharp CODs (and decelerations) during match play are performed from sub-maximal speeds (Dos’Santos et al., 2022). Therefore, it is recommended that athletes are also exposed to sharp CODs during training from sub-maximal speeds. Furthermore, it is important to note that decelerations and CODs can also be commenced or followed from varying body positions (i.e., sideways, backward or different combinations) (Morgan et al., 2022). Therefore, following a thorough needs analysis of the multi-directional sport, relevant priority should be placed on developing deceleration and COD skills from the various body positions most likely encountered in that sport and playing position.
Assisted Horizontal Decelerations
Assisted horizontal decelerations are performed with assisted pulling loads (i.e., using elastic bands and motorised resistance devices) to increase horizontal deceleration and braking demands. However, unlike assisted horizontal braking steps, assisted horizontal decelerations require braking forces to be generated at faster movement speeds and with shorter ground contact times, thereby challenging the speed of inter-limb coordination and horizontal braking rate of force development. New motorised resistance devices also enable assisted load to be prescribed in the deceleration phase, before changing to a lighter resisted load in the re-acceleration phase of a COD task (Figure 10). This prescription is similar to applications of accentuated eccentric load training in the vertical plane to accentuate the deceleration (eccentric) phase before moving to a lighter resisted load in the re-acceleration (concentric) phase.
Braking Performance Exercises
An important aim of braking performance exercises is to enhance braking skills under constraints specific to the competitive environment (i.e. game-representative braking) (Woods et al., 2020). Therefore, eccentric training options within the braking performance exercise category are designed to enhance horizontal deceleration ability using tasks and constraints more specific to the competitive performance environment, including 1) unanticipated horizontal decelerations, 2) contextual horizontal decelerations, and 3) game-specific horizontal decelerations.
Un-Anticipated Horizontal Decelerations
Unanticipated horizontal decelerations (i.e., agility) are designed with multi-directional, linear or curvilinear movement challenges, or combinations of these, with either, or both, offensive (i.e., to create space/evade) and defensive (i.e., to close down space/pursue) goals, but without the integration of sport-specific technical skills. These can include agility games (i.e., chase and evade drills), dyad partner training (also known as mirror drills), invasion games (i.e., 1vs1, 2vs2) and COD tasks requiring action to an external stimulus (i.e., visual, tactile, and audible). Practitioners should look to design and progress unanticipated horizontal decelerations by manipulating the key constraints of the practice environment (e.g., rules of the task) to enable the desired type of unanticipated horizontal deceleration to emerge. For example, to progress the intensity of unanticipated horizontal decelerations the practice design could be manipulated to encourage unanticipated horizontal decelerations to be performed from progressively greater movement velocities or COD angles (Figure 11).
Contextual Horizontal Decelerations
Contextual horizontal decelerations aim to re-create movement patterns that incorporate game-specific horizontal decelerations in combination with technical and tactical outcomes encountered when both in and out of possession, also known as the integrated approach (Bradley & Ade, 2018). Contextual horizontal deceleration sessions can be designed using either a position-specific format, or with a combination format where different positions are worked in unison (P. Bradley et al., 2018). Using the common technical and tactical actions performed by wide midfield soccer players while in and out of possession of the ball (Ade et al., 2016), an example contextual position-specific drill is illustrated in Figure 12.
Game-Specific Horizontal Decelerations
Game-specific decelerations are ‘modified’ versions of the formal competitive game, commonly known as sided games (Ometto et al., 2018). In team sports such as soccer these are often further described as small-sided games (SSG; 1vs1 to 4vs4), medium-sided games (MSG; 5vs5 to 8vs8) and large-sided games (LSG; 9vs9 to 11vs11) dependent on player numbers and size of the playing area. The key aim of game-specific horizontal decelerations is to develop a player’s game-specific horizontal deceleration capabilities by utilising tasks highly representative of the competitive environment. Using soccer as an example, SSG and MSGs with a smaller player number and playing area can overload the frequency of high-intensity (> -3 m.s-2) decelerations and associated technical actions in comparison to the average and most demanding passages of play experienced during competitive matches (Martin-Garcia et al., 2019; Martín-García et al., 2020). However, practitioners should be aware that SSGs (i.e., intensive soccer conditioning) might not provide adequate opportunity for players to perform horizontal decelerations from higher running velocities that may have a different neuromuscular and mechanical demand (Harper et al., 2023; Oliva-Lozano et al., 2020). Accordingly, LSGs (i.e., extensive soccer conditioning) with larger playing areas can allow players to attain higher and more frequent maximal deceleration values than SSGs (Abbott et al., 2018; Gaudino et al., 2014). Therefore, practitioners should use a variation of sided games to ensure players are exposed to decelerations from various speeds in order to develop a wide range of braking strategies.
Summary and Implications
The Braking Performance Framework can assist practitioners in selection of training methods and exercises to target the eccentric strength qualities that are important for enhanced horizontal deceleration ability.
During horizontal decelerations, eccentric muscle actions are more likely to occur due to the requirement of muscles to exert a braking action to resist and yield centre of mass forward and downward motion (Franchi et al., 2017).
Eccentric strength training is therefore paramount for enhancing horizontal deceleration and increasing resilience to the high impact forces that are repeatedly encountered during match play and training.
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