By Andrew Hyde
Last updated: April 20th, 2024
5 min read

Contents

1. Introduction
2. Review of the Research
3. Conclusion
4. About the Author
5. References
6. Comments

Introduction

Limb Symmetry Index (LSI) is a ratio between opposing limbs (e.g. right leg and left leg) that is commonly used within rehabilitation protocols, to compare an affected limb to (what would usually be) its unaffected counterpart (Palmieri-Smith et al., 2015).

It is calculated as follows:
(Affected limb value / un-affected limb value) * 100.

The LSI value is expressed as a percentage – the affected limb value as a percentage of the unaffected limb value. This value could represent numerous qualities such as strength in a particular muscle (e.g. the quadriceps) or performance in a hop test (e.g. single-leg vertical jump).

As it’s an easy-to-calculate, inexpensive and flexible objective measure of limb symmetry that can be used for different tests throughout a rehabilitation protocol, there’s no surprise it’s so commonly used within clinical practice.

The use of LSIs also removes the issue associated with progressing patients through their rehabilitation by being able to complete a certain number of repetitions in a particular exercise, which heavily relies on research in a very specific population.

Although LSIs have many appealing advantages, they don’t come without their limitations. Not only are these limitations crucial to be aware of, but their potential implications require constant consideration and reinforcement within clinical settings.

Therefore, the aims of this Blog Post are to highlight the key considerations from peer-reviewed literature that practitioners should be aware of when using LSI’s in their everyday practice

Review of The Research

It is clear that there is abnormal limb symmetry following procedures such as anterior cruciate ligament reconstruction (ACLR) (5). In uninjured populations, using LSI’s for measures such as knee extension and flexion range of motion, endfeel and effusion have previously demonstrated excellent reliability (3). However, the same study suggests that when LSI’s are used for hip adduction strength, scores can show larger variation.

In patients who have had an ACLR, there is reduced maximum voluntary activation bilaterally in the quadriceps (10, 11). This is further supported by Palmieri-Smith et al., (2008), who suggests that this may also be due to arthrogenic (reflex) muscle inhibition (7). Depending on the measure being assessed and the stage of rehabilitation, LSI ‘pass’ scores can typically vary from 80-95%.

Another study found that even 7-months post ACLR, both male and female participants who scored mean LSIs of 95.4 % across 3 different hop tests, their raw scores (e.g. jump distance) were still much lower when compared to healthy participants (2). This data further supports that there is true bilateral muscle weakness present following ACLR, which is highly neural.

These implications lead us to another study, where pre-operative ACLR participants completed a quadriceps strength test and hop test to gather LSI scores, with the same testing administered 6-months post-op (12). At 6-months post-op:

• 40 participants achieved 90 % LSI scores.
• However, only 20 participants achieved 90 % of their pre-operative scores across all measures.
• Oppositely, 24 of the 40 participants who achieved 90 % LSI 6-months post-op, did not achieve 90 % of their pre-operative scores.

This means that even though participants scored 90 % LSI 6-months post-op, over half still weren’t at 90 % of the level they were at before their operation. So, even though for some clinicians, this criteria may be a pass to progress rehabilitation, patients may not be at an acceptable level. This further supports the notion that there is bilateral quadriceps weakness following ACRL.

It also appears that LSI scores are significantly higher in a Single Hop for Distance and Triple Hop for Distance versus peak knee extension isokinetic torque and a bilateral power leg test (4). This again is likely due to the decline in function of the unaffected limb (9).

Conclusion

This body of research highlights the utmost importance of patients continuing to train their non-affected limb to maintain as much function as possible. This minimises the chance of LSI scores post-op underestimating knee function. It is crucial to encourage and reinforce this with patients, so they are committed to their rehabilitation.

Where possible, pre-operative testing is recommended to set a true benchmark (Davies et al., 2020). However, it’s important to consider when an ACL injury was diagnosed and how long the patient’s level of physical activity has been reduced, as this may have already resulted in a decline in function of the unaffected limb.

This also allows practitioners to take advantage of benefits such as cross-education. Providing a high neural training stimulus to an unaffected limb can also help reduce the loss of neural function in the affected limb (Papandreou et al., 2013).

Limb Symmetry Index is an easy-to-calculate, inexpensive and flexible objective measure of limb symmetry that can be used for different tests throughout a rehabilitation protocol. It is also an effective method. However, for this to be true, The above limitations must be considered to ensure that affected limb function is not overestimated and true equal (or close to) function is achieved.

The post Limb Symmetry Index: Chasing Equal Function appeared first on Science for Sport.

Contents

1. Introduction
2. An S&C Graduate – One Year On
3. Lessons Learned
4. Conclusion
5. About the Author
6. References
7. Comments

Introduction

As an S&C graduate in the UK, the reality of industry hit me as I finished my master’s degree in June 2019. I instantly began searching for my first graduate role. Fast forward five months and in October 2019, I was still unemployed. I was unable to source any job statistics for S&C Coaches so the best I can find is below, from the UKSCA 2016 State of the Nation Survey, although this had hopefully and likely somewhat improved between 2016 and pre-COVID-19. Since then, I can only imagine that wherever they were, the statistics have changed in a way that we wouldn’t like them to. It’s certainly changed the way I now coach, behind a mask.

The purpose of this Blog Post is to provide an update on how things can change and improve for young S&C graduates in the UK, despite the uphill circumstances in our way, or the unexpected arrival of something like a global pandemic along the way.

An S&C Graduate – One Year On

After graduation, I was working on my ‘side hustle’ with no income. I had just left a part-time retail job that I could no longer withstand in hopes that it would help me dedicate even more time to securing a graduate S&C job.

• August 2019 – S&C Role 1: I secured a monthly (once per month) role as Research Finder at Science for Sport.
• December 2019 – S&C Role 2: I secured a part-time role as an S&C Coach in the NHS.
• January 2020 – S&C Role 3: I secured a part-time as Content Manager at Science for Sport.
• February 2021 – S&C Role 4: My ‘side-hustle’ Aesthetic Athletes now work in partnership with two different football coaching businesses to develop field skills in football players, a football team, an online youth sports educational platform, 1:1 football players and the general population online only.
• Present – I currently work all 4 of these roles in unison, creating what is a little more than a full-time role.

Luckily, all of these roles have managed to continue and even prosper throughout the COVID-19 pandemic.

Lessons Learned

There are some suggestions I recommended as a fresh S&C graduate to those becoming S&C Coaches, which remain true now.  That isn’t to say my other suggestions in part 1 are not, but more that since writing it, the ones I am going to discuss have been further solidified. The first is that a side hustle does help. It gives you purpose, helps you develop and refine skills that help with employability, helps you find a niche to develop your unique value proposition and brings in some extra income, eventually. My side hustle has managed to adjust and prosper during the COVID-19 pandemic, strengthened my CV and displays unique characteristics in my character that heavily outsell the usual ‘hard worker’, ‘passionate’ and ‘reliable’ candidate.

The second suggestion that remained true is that you can create your own opportunities with ever-growing subsectors in S&C. We ultimately steal so many methods and ideas from other industries. Do you think statistics, reverse engineering or GPS were made for S&C? Of course not. In the same way that S&C wasn’t originally developed to support special populations, Esports or the National Health Service, we’re growing as a field. If you’re struggling to find a role as an S&C graduate, it might be time to think outside the box.

Whether you’re thinking about approaching a unique subsector, applying for a unique role or even just a typical S&C role, it might be worth conducting a needs analysis for the subsector, organisation or role before you worry about conducting one specifically for the athletes, clients or patients themselves. As one of the very few S&C coaches working in the NHS, finding out exactly what that team needs and how I specifically can provide this support is a must. It gives the opportunity you’re trying to create for yourself, your application process and also the work you do once you’re through the door, a true direction and purpose which all align. To continue, the way in which you work can completely change to what we would usually expect. That is job security, set hours and more respectable salaries.

That brings me to my final point from reiterating what remained true. And that is always showing a willingness to develop. When I first accepted my S&C role in the NHS, I switched from the weight room to the wards and worked alongside physios on Major Trauma and COVID-19 wards due to the COVID pandemic, this was before even starting out with my original role in the outpatient’s gym. If you’re applying for a role or trying to create an opportunity for yourself in a new subsector, you may just find that you have to do stuff that isn’t what you may call S&C. Well, if it helps you develop and gain skills in unique ways that other S&C Coaches may not be able to demonstrate to employers and it shows you’re a team player, then do it. Even if it’s a role not relevant to our industry specifically, it may just help you develop generally.

Conclusion

I will conclude this article with the biggest lesson learned, is that it can be done. As an S&C graduate, even if you have no potential prospects in a highly saturated, high barrier-to-entry and low-paying industry, you can gain full-time work in this industry as well as a salary that gives you the start you need to begin your career as an S&C graduate.

The post The Reality of the S&C Industry for Graduates – An Update appeared first on Science for Sport.

How can we ensure our programming is context-driven?

By Andrew Hyde
Last updated: February 29th, 2024
8 min read

Introduction

Improving the competitive performance of athletes in field-based invasion sports such as football (soccer) calls for a needs analysis of the technical/tactical (21), physiological (19) and biomechanical (18) requirements of the sport. Although soccer is an intermittent sport that uses both the anaerobic and aerobic energy systems (3), this Blog Post will focus on the biomechanical and perceptual aspects of field skills in soccer. By field skill, we refer to athletic skills such as deceleration, agility and speed.

Therefore, the aims of this Blog Post are threefold 1) discuss how we can identify and program field skills 2) clearly identify and understand the field skills and 3) describe what they look like in soccer in addition to as a general technical model.

Needs Analysis

To understand what field skills occur in soccer and how these occur, we as coaches need to develop a needs analysis which is specific to the sport (e.g. soccer) and the particular playing positions on the field (e.g. midfielder or winger).

To do this, of course, we should draw on peer-reviewed literature to provide us with evidence-based time-motion data on the demand of the sport. However, to provide more context of how things actually happen, a notational analysis of a game or video clips of gameplay on YouTube can help us figure out exactly how athletic tasks are executed and the stimulus that causes these tasks to be carried out (14).

Reverse Engineering

Once this information is collected and at our disposal, we must begin with the end in mind. S&C coaches have all been guilty of losing sight of the end outcome during the decision-making processes of exercise selection for example.

If sessions support the improvement of a field skill with specificity to how it is used in game situations, it is time well spent. This is not to say general physical preparation shouldn’t be carried out, or general speed mechanics shouldn’t be taught, but that context must be applied eventually with the aim of achieving true transfer.

Once general models of field skills such as acceleration are taught, we must continue to build field skills by ensuring that the drills prescribed are integrated by athletes in sports-specific scenarios (14) and that the gym-based exercises we prescribe support the development of these field skills. It’s also important to note that the quality and context of coaching must align with these concepts too (14).

Understanding Field Skills

Field skills in soccer can be categorised into three main groups:

1. Deceleration
2. Agility & pre-planned change of direction speed
3. Acceleration & top speed

It’s important to note that despite being grouped, agility & pre-planned change of direction are completely independent skills (24), as are acceleration & speed (22).

As proposed by Jefferys (12, 13), skills can be broken down into:

1. Initiation movements – Used to start movement or change motion (e.g. Side-step motion to move laterally whilst watching play).
2. Transition movements – Used to set up a position where subsequent movement can be efficiently executed (e.g. crossover step to assume a position facing forwards).
3. Actualization movements – The final movement that determines success in an athletic task (e.g. following a transition with a sprint to beat an opponent).

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Deceleration

Deceleration is defined as a rapid stop or decrease in the body’s velocity, followed by re-acceleration in a different direction (10). This means that deceleration is a transition movement (14).

Kinematically it can be described by a centre of mass (CoM) posterior to the feet with a full foot heel strike, small steps and a wide base with knee flexion. Kinetically it can be described by high braking forces, long ground contact times, high step frequencies and eccentric muscle actions of the quadriceps and gastrocnemius (5, 1). Gradual progression in deceleration is key as decelerations high a load that is 37 % higher than accelerations per square metre (8).

Being a transition movement which precedes change of direction (CoD) and having a higher occurrence in small-sided games (SSG) (21), sessions entirely dedicated to deceleration are likely unwarranted, especially when decelerations occur 2.9x more frequently than accelerations (8).

Agility & Pre-planned Change of Direction Speed

Sprints that include a CoD precede 6 % of all goal-scoring situations in soccer (6). Even though this may appear low, players cover an average of 217 + 165 m through multidirectional sprints (4), accounting for 3.5 % of their total distance. From a time-motion perspective, players change direction every 3.8 – 4.5 seconds (3).

However, true Change of Direction Speed (CoDS) in invasion sports is rare (12), defined as a pre-planned task where “change of direction” occurs (20). Albeit, closed CoDS drills can be used as general tissue preparation to develop eccentric strength, dynamic balance and concentric rate of force development as a physical foundation to agility without a cognitive component.

This isn’t to say that developing CoDs is useless. Pre-planned side steps result in greater lateral foot placement, greater lateral movement speed, greater forward foot displacement, increased hip abduction, lower knee joint angles and reduced forces through the knee than unplanned side stepping (11). This can help us develop the physical aspects of agility.

On the other hand, agility is defined as a “rapid whole-body movement with a change of velocity or direction in response to a stimulus”. With a change of velocity being agility, deceleration alone could be performed as an offensive agility transition (24).

For example, a winger could be performing a linear sprint with the ball down the line, towards the touchline. As they approach the touchline at a high speed, they stop the ball before it goes out, decelerate past the ball and turn back towards it to cross or pass. The aim of the deceleration was to go from ‘fast to slow’ more suddenly than a defender, to create time and space to execute a pass or cross.

Acceleration & Speed

Linear acceleration and maximum velocity sprinting are soccer-specific actions which can impact the outcome of games (16). Elite soccer players average 17 m per sprint, with ~50 % being shorter than 10 m (8) and only 4 % reaching 30 m (3).

45 % of goal-scoring scenarios are preceded by a linear sprint (6). Although forwards, wingers and full-backs perform more sprints compared to centre-backs and central midfielders, there doesn’t appear to be differences in sprint distances (7). Forwards show superior sprint speed to other positions, with defenders and midfielders showing similar sprint capabilities, followed by goalkeepers (9).

Sprinting bouts are often preceded by players already being in motion (16) and successful acceleration in team sports has been characterised by faster ground contact times and increased stride frequency (17).

Acceleration in soccer can start as an initiation movement in a variety of ways such as shuffling back, moving side on or in stationary facing backwards. This means that acceleration training must go beyond wall drills. Especially when notational analysis shows that defenders may spend much of their time sprinting with their torso and head facing play whilst their legs are forwards, sprinting back towards goal.

It’s also not uncommon for soccer players to sprint in curved lines. Attackers (centre forwards) perform larger angled curved sprints (10-15°+), to run around and in behind defenders who perform smaller angled sprints (7).

Conclusion

The main aims of this Blog Post were threefold 1) discuss how we can identify and program field skills 2) clearly identify and understand the field skills and 3) describe what they look like in soccer, rather than as a general technical model.

To conclude, S&C coaches should ensure they truly understand not only the demands of sports such as soccer and the individual positions, but how movements occur. S&C coaches must reverse engineer their programming process and work backwards from the end outcome to ensure their programming and coaching are context-driven to improve field skills and drive high on-field performance.

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Andrew Hyde

Andrew has a degree in Sport & Exercise Science and a Master’s in Strength and Conditioning from Leeds Beckett University. He is the Director of Aesthetic Athletes where he works with elite soccer players and the general population. Andrew has also worked as a Strength & Conditioning Coach in the NHS, rehabilitating ACL ruptures, and is the Content Manager at Science for Sport, having previously worked as an Intern Strength and Conditioning Coach with Leeds United F.C. Ladies Academy.

More content by Andrew

References

The post Developing Field Skills in Football (Soccer) Players appeared first on Science for Sport.