Outcome measures: An observation and a reflection

Sports science and strength & conditioning practice is built on a foundation of identifying a problem, testing the problem, applying an intervention and then re-testing to ensure progression. Athletes will buy into fitness testing, injury prevention and subsequent high performance behaviours if they are given the impression that their coach and medical team know what they are doing and things are done with a purpose (Kristiansen and Larsson, 2017). This begs the question whether coaches can justify and clinically reason their battery of performance tests.

When applying a performance measure, understanding of the underlying kinematics is essential to understand the validity of the test to the desired outcome. The OptoJumptm is a valid tool in assessing a reactive strength via  drop jump (Healy et al., 2016) however what components of the jump is the coach wishing to address? The validity of the tool is the not the same as the validity of the test. For example, reactive strength index (RSI) can be influenced by a reduced contact time (stretch shortening cycle via the musculotendinous unit) or via total jump height (power output throughout the lower limb and nervous system) or a combination of both (Healy et al., 2017). Understanding these mechanisms may influence the instructional bias of technique given by the coach in order to test what is desired.

With complexities over a test like an RSI to something seemingly obvious like a jump, testing for broader components of fitness and multiple movement patterns is much more difficult.

The Yo-Yo intermittent recovery test (IRT) is reported to be a valid measure of fitness and correlates to match performance in football (Krustrup et al., 2003). However, this is an example of a fitness capacity test and in fact correlates to fitness capacity in a match scenario. In field based team sports, there are a large number of variables and complex interactions that all contribute towards “performance” as an outcome (Currell and Jeukendrup, 2008). Krustrup’s conclusion was based on correlated Yo-Yo IRT results to high speed running in a game (>15km.h-1) with a strong correlation (r=0.58). Overlooking the methodological accuracy of this (pre-GPS, using VHS locomotive assessment retrospectively), the correlation is between two differing metrics. Where the high speed running was recorded over 90 minutes of varying intensities and periods of effort (12 players across 18 different games), the Yo-Yo IRT covered 1.7km in a mean time of 14.7mins with incremental increases in pace dictated externally. For a test to be considered a valid indicator of performance, it should meet the same metabolic demands as the sporting activity (Currell and Jeukendrup, 2008). The Krustrup paper does not make this comparison, instead analysing physiological markers from rest to exhaustion during the Yo-Yo IRT, not exhaustion markers in comparison to game data.

Perhaps semantics, but in fact there should be differential terminology to distinguish “fitness performance” from “athletic” or “sporting performance.” It should be considered that sporting performance is influenced by a large number of uncontrollable and non-modifiable factors that would make any comparison of validity and reliability to outcome measures unfair. Essentially, recreating a competitive environment is near impossible. This raises the question whether we are exercising just to improve test scores or, closing the loop and relating exercises to performance? Does raising the envelope of one, consequently improve the other? Something that we should not only be asking ourselves, but a question we could come to expect from coaches and athletes a like.

Oriam

Does the research answer this?

It has been suggested that stronger athletes produce faster sprint time, quicker change of direction speeds and higher vertical jump scores when compared to weaker athletes of the same sport (Thomas et al., 2016). Squat jump (r = -0.70 to -0.71) and counter movement jump (r = -0.60 to -0.71) demonstrate strong correlations to change of direction speed (Thomas et al., 2016). Peak force during isometric mid thigh pull was significantly correlated to 5m sprint time (p <0.05) however this correlation was only moderate (r = -0.49). But again, does this correlation transfer into performance if the testing protocol doesn’t accurately mirror sporting performance?

Sprint times over 40m have been shown to decrease following an acute bout of heavy loaded squats, hypothesised to be due to post activation potentiation (Mcbride et al., 2005). Higher squat strength scores also correlate with sprint times over 0-30m (r= 0.94, p=0.001) and jump height (r = 0.78, p=0.02) (Wisløff et al., 2004). Importantly, we know sprint performance tests have demonstrated construct validity to the physiological requirements of a competitive field based game (soccer) (Rampinini et al., 2007), which is ultimately what we are aiming to do; relating performance testing to physiological and metabolic markers from a given sport.

The addition of a jump squat exercise into a training program may help improve 1RM squat and 1RM power cleans (Hoffman et al., 2005). So perhaps yes, there is a perpetuating loop between exercise, tests and performance but the link between them all may not be tangible or direct.

But how do we translate all of these statistics and data sets this to a non-scientific population, as a lot of our athletes are? I’ve developed the following analogy to try and help with this.

 

Solar system analogy:

If we consider that “athletic performance” is the main focus of any intervention, much like the sun at the centre of the solar system. This is the bright light that everything revolves around; media, finance, fan base and support and so on. It could be argued that any intervention we have as coaches will never truly replicate “athletic performance” but should be influenced by it. This influence works both ways, positively and negatively. For example, if we maximally test an athlete before a competition, this will likely have a negative impact on “athletic performance”. Conversely, if we were able to collect data that informed a training program to improve athletic performance, despite not actually replicating “athletic performance” it would (hopefully) have a positive impact. For example, a football game is determined by so many uncontrollable variables that can not be replicated in a gym, but we might identify that a player needs to improve their 5m sprint time which in turn, will benefit performance.

Figure 1 solar system
Figure 1: An analogy depicting the relationship between “athletic performance” and controlled interventions / measures. The skill of the coach is identifying which outcome measure or intervention is going to have the greatest influence on athletic performance.

Let’s consider our potential interventions to be orbiting the sun (Figure 1). There is an interaction between the planets and the sun via gravity but they do not have a direct overlap, where the planets do not collide with the sun just as an outcome measure does not truly match sporting performance. We know that larger planets have a greater influence, so as coaches, we are trying to affect the level of positive interaction with “athletic performance”, the gravitational interaction. By influencing links between exercise intervention and outcome measures, we can affect the size of these planets. In turn, this will have a greater interaction with the centre of our solar system, “athletic performance” (Figure 2). Much like the universe, there will be many different solar systems just as there are different sporting codes and contexts, so the skill lies in identifying the most influential planets in your solar system.

figure 2 solar system
Figure 2: The impact of enhancing an intervention or measure on sporting performance, in this case there has been a greater focus and development of the blue “planet” which has changed the interaction with the “athletic performance”

 

A clinical reflection:

For long term injuries, I utilise a continuum to guide return to play (train / play / perform), often these stages are guided by outcome measures linked to goals and aims for stages of rehab. Typically these tests are scheduled in advanced and often follow a planned “de-loading” micro-cycle. This helps with continuity and, as much as you can in sport, standardisation of the test.

A recent case study found me questioning my judgement and to a degree, wondering if my intrigue and curiosity about my rehab plan drove me to test out of sync with the schedule, instead of doing the test for the athletes benefit.

Following a good period of return to train, the proposed testing date previously scheduled clashed with a squad training session. Observational assessment suggested the athlete was coping well with the demands of training and it seemed counter-intuitive to pull them out of training to undertake some tests. A few weeks later, a gap in the daily schedule presented an opportunity to re-test. The test scores were down compared to the previous month, most likely because the athlete had trained in the morning and trained the 4 out of the last 5 days in some capacity. In previous tests, the athlete had come off of a de-load week and tested the day after a day off.

The result:

The athlete began to question their ability and availability to train. They were visibly knocked in their confidence given a drop in scores, despite me being able to rationalise why this could be. Having had the opportunity to feed my own interest and try to prove to myself that a rehab program had worked, the outcome was much worse. I threatened the confidence of a long term injury returning to training, potentially adding doubt and hesitation to their game and I did not get the results I was expecting.

On reflection, given their time out through the season so far, I should have stuck to protocol and tested on the scheduled day (one training session was not going to increase their chances of availability).. or, not tested at all. Instead, i shoe-horned some testing into an already busy schedule. What did I expect given the current level of fatigue?!

Image result for reflection

Previous results had reached a satisfactory level to return to train and I was now chasing the final few percentages available. To give them confidence? Probably not, as they were training and enjoying the return to train. So perhaps it was just to give myself confidence. An interesting lesson learnt, mostly about myself.

 

Yours in sport,

Sam

Viewing balance exercises with eyes closed

For a long time, I have questioned prescribing balance exercises with eyes closed to athletes in sport. Regular readers of the blog will know that I continuously explore the clinical reasoning behind treatments and interventions but have a particular interest in exercise prescription. I have to admit that single leg balance with eyes closed is an example of exercise prescription that just doesn’t make sense to me, how many athletes close their eyes to perform a sport related task? I’m regularly seeing discussions online about “what is functional?” and most of the debates are based around semantics without much weight behind them but provide a good opportunity for people to have a little disagreement about something. To avoid getting into a debate about “functional” I thought it best to better understand the concepts and demands behind “balance” to see if I can answer the “why” behind balance exercise progressions.

SLB
Now stay like that for 1 minute or until another player throws a ball at your face
One argument for closing eyes during balance exercises is to remove the visual stimulus and encourage the athlete to challenge vestibular and proprioceptive senses. Remove one thing and make others compensate for this deficit. In a study of track athletes, sway velocity (cm/s) increased two-fold when athletes closed their eyes during a static balance test (here) but the only significant finding in the study was the difference in centre of pressure displacement (cm) between non-dominant and dominant limb across the medial-lateral plane. So, no difference between male and female athletes and no difference between “eyes open” and “eyes closed”.

So how does this explain the increase in sway velocity? The sway velocity is the area covered in both the anterior-posterior and medial-lateral planes of the centre of pressure per second, indicating speed of correction. The fact that the displacement between “eyes open” and “eyes closed” was not meaningful suggests that the demand on the fine motor correction increases. A decent argument to include “eyes closed” in a balance program, if that is the aim.

Static balance in dynamic sports

Compared to dynamic balance tests, static tests do not allow re-positioning of the centre of mass within the base of support, so the athlete becomes more reliant on smaller corrections. Different sporting populations have demonstrated varying abilities in static and dynamic balance skills, with gymnasts outperforming in static balance but soccer players demonstrating better dynamic balance (here).

This may seem obvious given the control on the balance beam vs changing direction to avoid an opponent. But actually, perhaps where the argument becomes more broad and complex.

As with any exercise selection, it needs to be appropriate to the aims of the rehabilitation program and the demands of the sport, taking into consideration open and closed skills and linking these to fixed gaze drills vs dynamic gaze drills.

Have we gazed over “skill”?

In a given skill, experts can recognise which cues are relevant and avoid information overload (Martell & Vickers 2004). Below is a slide from my presentation “3 sets of when?” It explains the concept that following any injury, the athletes ability to perform a given skill returns (temporarily) to novice level.

skill level injury

Take a skill like walking. Immediately after an ankle sprain, your ability to perform that skill at an expert level is decreased. A skill that has taken years to perfect, to become automatic, now becomes a task which requires concentration. Thankfully, the return to expert level doesnt take years (hopefully!) and this is where our exercise selection becomes crucial to optimally load and sufficiently challenge. We can’t presume that the pre-injury skill level is the same post-injury. We should also consider experience of the balance task specifically. I can think of experiences where athletes are standing on one leg on a Bosu throwing a reaction ball at a 45 degree trampoline. “Oh you’re no good at that are you… we need to address your balance”

I’ve digressed slightly from single leg balance with eyes closed… and actually I still haven’t discussed “gaze control”.

off on a tangent

Gaze control links specifically to experience of a task. Comparing those skilled at orienteering to non-skilled (here) demonstrated an increased ability of the orienteering folk (what do you call people that go/do orienteering?!) to employ a wide focus of attention and to shift efficiently within a peripheral field. The test very cleverly measured gaze control to flashing images with varying degrees of relevant and irrelevant information. What is interesting from this study was that the control group where physically active and proficient in other sports, but the “skill” advantage lay with the orienteering-iers. [shrugs and thinks “sounds right”].

I did not know that about balance!…

Elite athletes have heightened spatial awareness and processing capabilities vs their non-elite counterparts, where gaze control is cool and calm, with long duration of fixation of specific locations. This results in better body positioning end efficient limb actions (here). What better example than ballet. When comparing professional dancers to controls walking along a thin taped line, it was observed that experienced dancers focus far into space, delivering effortless and accurate movements where as controls looked down and focused on the line, moving with greater speed and less control (here). Dancers shift their neural control from somatosensory inputs and to an increased use of visual feedback, via peripheral fields and focused gaze control. Interestingly, sub-maximal exercise has been shown to increase visual attentional performance (posh words for reaction time) and a decreased time need to zoom focus of attention (here). This is useful for prescription considerations.

This efficiency has been demonstrated in other studies also, where the addition of a 4-week balance training program to Physical Education classes in school resulted in increased CMJ, Squat Jump and Leg Extension Strength (here). A time period that can’t be associated with physiological adaptations to muscles (regardless of time, they did balance exercises!) and even when a balance training program has been compared to a plyometric strength program (here). It is thought that improved centre of pressure is linked to spinal and supraspinal adaptations, due to high inter-muscular activation and co-ordination.

My question for any budding researchers out there… if there is a spinal level involvement here, can we utilise the contralateral limb at the very early stages of injury to improve balance on the injured side?

Finally, I get to my argument… balance is the output. Balance and proprioception are different entities, as are gaze strategies and balance. But they may all be interlinked via “skill.”

In researching this blog, I’ve certainly become more accepting of “eyes closed” as an addition to balance programs. But also think I’ve gained more clarity on appropriate prescriptions and the suitable progressions for individuals.

Perhaps “eyes closed” is not a progression, but a starting point!

Immediately post injury, we are looking to internalise feedback (intrinsic) and focus on local, fine movements. There are plenty of regressions within “eyes closed” balance that we can make the athlete safe from secondary injury. Graded progressions from static to dynamic, trying to keep the demands appropriate to the skill required to return the athlete to “expert”.

From here, our progressions should not be the removal of a visual stimulus, but instead optimising and enhancing gaze control:

  • Focus on a stationary target –> moving target
  • Head still –> head moving (repeat stationary and moving target progressions within this)
  • Static balance –> dynamic balance (repeat progressions above)

Essentially, we progress through from intrinsic cues to extrinsic cues, where gradually the athlete is thinking less and less about the mechanics of balance and more about skill execution and performance. We know that gaze control components improve with sub-maximal exercise, so our ordering of our program can reflect this. It is commonplace for balance exercises to be at the beginning of the program, but if balance is our primary aim for rehabilitation, perhaps it should be later in the schedule.

I don’t think this is too dissimilar to how most people prescribe exercises, but for me at least it has given me a better thought process into the “why” which ultimately should make rehabilitation programming more effective and efficient and therefore more elite.

Yours in sport,

Sam

Laboring through a Labral Tear

One skill when working in sport is learning to compromise between your clinical brain (the one that tells you that pathology and injury needs to be managed a certain way) and your performance brain (which tells you that your job is to get athletes back over the “white line” in order to do their job). In an ideal world, we try and appease both of these brains where tissues heal well and performance is optimised with the lowest risk of re-injury. But there are some pathologies that cause these two brains to clash. Ones that can be “managed” until the off season where proper interventions can take place. One such injury that I’ve been trying to learn more about is the mid-season hip labral tear.

labral-tear-img

The purpose of these blogs is to encourage me to read more around certain topics, so in order to help with this I have to say thanks to a few people that have provided me with papers and words of wisdom (Erik Meira, Nigel Tilley & Joe Collins). And thanks to whoever invented Twitter because I probably wouldn’t have this access to knowledge otherwise.

The Problem..

Typically, hip instability injuries are seen in sports with high repetitions of rotational and axial load – football, gymnastics, hockey, tennis, martial arts.. and so on. The hip is widely accepted as being one of the most structurally stable joints in the body, with a deep acetabular socket lined by the labrum, which creates negative pressure within the joint to increase congruency of the femoral head. But what happens when this environment is disrupted? A recent review by Kalisvaart & Safran (here) explain that it takes 60% less force to distract the femoral head from the acetabulum in presence of a labral tear. (This review is great for explaining multiple causes of hip instability, not just labral tears, and also assessment techniques.)

Typically, a lack of stability is replaced by rigidity, where the surrounding soft tissues try to compensate for this increased translation (Shu & safran 2011 here and Boykin et al 2011 here). On assessment of an ongoing labral tear, its quite common to find increased tone or reduced range around adductors and hip flexors. Iliopsoas in particular plays a role to help increase congruency in the hip. (For tips on how to release iliopsoas, please tweet @Adammeakins) – one key thing when managing this condition is not to confuse high tone / over activity with being “too strong”. Chances are its the opposite, it more likely indicates a lack of control. Its not uncommon to see adductor tendinopathies secondary to labral tears as the the load around the joint increases – especially in sports like ice hockey where there is high eccentric load on the adductors (Delmore et al 2014 here).

The Intervention..

So, you’ve diagnosed the tear (clinically and / or radiographically) but other than being irritable, it isn’t affecting the athlete. (Note, not all tears can be managed conservatively, due to pain & some require mid-season surgical intervention – Philippon et al 2010 here). The key premise to your ongoing rehab should be to make the hip joint as robust as possible. Remember, “Stability – not rigidity”. Whats the difference? Can the athlete control the hip or pelvis while performing another task? Or do they lock into a position and rely on passive structures like ligaments and joints.

Consider the demands of the sport. Don’t just fall into the trap of working through what I’d call the “action man ranges” – true anatomical flexion, extension, abduction and adduction. Watch training and competitions of nearly all sports and you’ll rarely see these truly sagittal or coronal movements. They tend to be combinations accompanied by transverse movements of the body in relation to the limb. Make sure this is replicated in your rehab.

Using the three examples above, consider the role of the hip musculature throughout these movements. We don’t always have to replicate abduction in an open chain movement, sometimes its necessary for it to be closed chain and for the body to move relative to the limb. Note how none of these tasks fit the “action man ranges” but all involve some degree of traverse rotation, combined flexion and abduction or extension and adduction etc etc.

man4
No I can’t bench press, but my squats are awful.
Delmore et al (here) and Serner et al 2013 (here) describe some excellent exercise interventions for the adductors here. These include some good low-load isometrics for those early stage reactive tendons – with isometrics appearing to down-regulate pain associated with this acute pathology (Koltyn et al 2007 here; Rio et al 2015 here to name just two resources) . Moving forward through rehab, I’ve discussed exercise progression at length before (here), I’m not dismissing exercises that involve pure flexion, extension etc but as part of a progression, its important to combine these movements. For example, start with a single leg dead lift – can the athlete control their trunk through hip flexion and through extension back to neutral? No? Then here’s a range to work on, using regressions to help improve technique and control. Yes? Then add a rotational component at different ranges of flexion – rotation away from the standing leg will increase the demand on the adductors to control the pelvis in outer ranges. The leg itself hasn’t abducted, but relative to the trunk it is hip abduction.

Remember the bigger picture

Its important not to just focus on the affected structures. For those interested in groin pain, a summary of the 1st world conference on groin pain is here – one key message from that conference was that anatomical attachments are not as discrete as text books make them. Consider what else contributes to the hip and pelvis control. We have mentioned iliopsoas control, but also rectus abdominus. Its not just a beach muscle. Eccentric sit ups can help improve control of the hip flexors, along with some lower load exercises like dead bug regressions – a little imagination or some quick youtube research can turn this one concept into hundreds of different exercises.

We have addressed the issue of controlling abduction through range with the adductors, but also remember to maintain that abduction-adduction ratio with some external rotator & abductor muscle exercises (queue Clam rant here – clams to me are like psoas release to Meakins). Possibly the best piece of advice I was given when doing this research was from Joe Collins, who told me to consider hip joint pathologies like you would a rotator cuff injury in the shoulder. Don’t neglect those smaller, intrinsic muscles around the hip. The exercise below is an anti-rotation exercise working through ranges of hip abduction-adduction.

The athlete is tasked to resist the rotation of the femur into external rotation while slowly moving through hip abduction and back to adduction. (This example is done with a shorter lever to improve control and the bench provides feedback to keep the hips in neutral or extension, rather than the favored flexion). Anti-rotation exercises can also be incorporated into trunk / core control exercises (for any instagrammers – follow ETPI who post some great videos and snaps of golfers working on rotational control). Progress from anti-rotation into control through rotation. Some examples here:

anti-rotation plank with sagittal control

Anti-rotation plank with traverse control. Encourage the athlete to keep the pelvis still when moving the upper limb.

photo 4

Single leg bridge with arm fall outs. Can be regressed to a normal bridge if the athlete lacks lumbo-pelvic control.

Side plank with arm tucks – an example of controlled trunk rotation while isolating the lower body to stay stable. Can be combined with the adductor bridge mentioned in Serners paper to increase load through proximal adductors.

 

These are just some ideas of how to manage a labral tear mid-season; working on rotational control, analgesia via isometrics, improving congruency in the hip joint and overall hip stability via strengthening – Stability, not rigidity! The exercises mentioned here are by no means an exclusive list and I love learning about new drills and ideas, so please share any that you find useful.

 

Your in Sport,

Sam