What Do We Mean By Robustness In S&C?

The Nordic example..

Years ago I gave a case study presentation on a 400m athlete return to sport (RTP/S). I was asked what I meant by “improving tissue tolerance”. I didn’t really know tbh, just get stronger? I thought my 3x12 listed in the spread sheet covered it. Years on, ‘robustness’ is the new ‘tissue tolerance’ that is often parroted by the S&C community. It is (not always) positioned in the same way we typically looked at tissue tolerance i.e through a strength biased lens. It goes a little something like...

"Make the muscle/tissue stronger so we can tolerate increased demands.“

This is neat, measurable, and intuitively appealing... It also isn’t necessarily wrong. However, it does risk looking at some issues from what you could call a low zoom component level lens, and often conflates mechanism with cause when we think about injury. That is, the stronger the tissue = reduced injury risk = robustness.

I think this is a simplification of the concept and can potentially negatively impact our decision making in practice. Instead if you view this through a systems level lens, robustness emerges not from emphasising a single component, but from the interaction of multiple components. Local tissues contribute to robustness, but also tissues share load, movement solutions emerge, systems continously contribute to minimise disruption, and cognitive / perceptual strategies adapt.

Robustness then is displayed when the ‘system’ finds solutions to maintain performance despite perturbations, through redundancy (backup strategies) and adaptability (new solutions). Just as blood pressure rises trigger heart rate drops to stabilise circulation and function, athletes can display robustness when for example alternative movement solutions emerge without loss of function due to well trained subsystems. The value then for a practitioner lies in weaving across levels, not to disregard reductionist approaches to improve robustness but embedding it inside a multi-layered systems view that improves practice.

Interestingly, and rather ironically, we often only truly appreciate the emergent nature of robustness as a concept in injured athletes. Take an athlete who is returning from an ACL reconstruction. In a SL hop test they may achieve symmetry with their non-injured leg. However, this may be achieved via an altered movement strategy. These compensations allow the athlete to maintain performance despite local tissue limitations, demonstrating robustness i.e. the system’s ability to sustain output under perturbation.

However, the irony is a) we only really pay attention to these compensatory strategies after injury, when the system is vulnerable and b) we fail to then appreciate that similar mechanisms are continuously at work in healthy individuals that likely make us ‘robust’. I think this is where component level thinking meets systems level thinking.

Robustness then emerges when multiple subsystems are well trained across contexts, where we are capable to fill the gaps under perturbation. If these supporting subsystems are underprepared, they may also expose vulnerability. With adequate capacity though, it allows the system to maintain performance (likely why GPP should absolutely always be a thread).

In this sense then, compensation can be both a marker of robustness = the system maintains output through adaptive solutions and redundant pathways OR a potential sign of fragility in another context = if the perturbation increases, these same compensations may expose vulnerable tissues or overload other subsystems that are not prepared in other performance contexts e.g. progressing the ACL-R athlete to small sided games where the knee will be exposed to unpredictable situations where compensatory options are constrained.

***I think this also goes a long way in explaining the conceptual differences between terms like ‘bulletproofing’ and robustness, and some of the nonsense in the rehab world.

Being robust doesn’t equal being invulnerable, where practitioners talk about ‘bulletproofing’ assumes a tissue or athlete can be made immune to injury = nonsense.

No single intervention can eliminate all risk or prepare you for all contexts. Not to be too abstract but the Nordic hamstring curl hyperbole is a good case study. The low zoom component level thinking goes something like;

Sprinting can cause hamstring strains

Eccentric weakness is a risk factor

Eccentric strengthening can reduce risk

Nordics improve eccentric strength

Nordics = robustness bro

This makes sense at the tissue level, and nordic protocols are supported by decent evidence in isolation (depending on how you do your stats that is) but this ignores the broader system and contextual factors.

To reiterate, you don’t throw the baby out with the bathwater, but mindful that if we’re stuck on this level then we assume the hamstring’s eccentric strength proximal to the knee is always the key bottleneck, and that nordics are the best way to remedy that. I don’t think that is the case nor does the data tell us that.

What I find somewhat amusing about this is the bias of the S in S&C when it comes to the popularity of this content. Perhaps because that is often historically the thing that is lacking for many team sports athletes and/or it is the things we can control. But as an example in RTP, we often look at hamstring strength outputs post injury in exit criteria, but don’t often consider the disruption to the normal muscle fibre structure following injury which impacts oxygen utilisation. It’s not just a loss of fascicle length & stiffness in the extracellular matrix but also...

-A shift in fibre type composition (often a selective atrophy of type I fibres and relative preservation or even shift toward type IIx) which reduces oxidative capacity.

-Reduced capillary density around the injured region.

-Loss in mitochondrial density which has a fast degradation.

All contributing to a lower local oxidative support. The return of these qualities require time and are more volume dependent than intensity dependent. And whilst SIT/HIIT work can rebuild these peripheral qualities, those types of activities are often contraindicated in early-mid RTP, and so one can not just assume this is regained with exposure in late stage RTP.

If noticeable increases in capillary to fibre ratio can take 6 weeks and similar with increases in mitochondrial density, then it is clear that an athlete returning from injury almost certainly would have not rebuilt peripheral oxidative support of the previously injured tissue.

When you consider that the epidemiology is quite clear in team sports that the majority of hamstring injuries occur when fatigue is accumulated / high speed running for minutes prior the injury, or more likely towards the end of each half, then things like chronic sprint exposure, competitive sprint exposure and repeat sprint ability (RSA) become critical (...along with a load of readiness markers).

The physiological adaptations that underpin these high intensity efforts and recovery between sprints reducing the degradation over the course of a game is a priority. And so cool, the athlete can express outputs in isolation in a gym, but hasn’t reconditioned the tissue to repeat them under fatigue and in game conditions. When training/match demands suddenly reintroduce fatigue, the system lacks sufficient redundancy and breakdown occurs. Could this perhaps contribute to reinjury rates that peak within 2–6 weeks after return? Maybe. Who knows.

And this is kinda the point.... This is also an equally reductionist train of thought in this specific example, it’s just rarely ever discussed in comparison to nordics = hamstring strength = improving robustness, but can be considered somewhat equally ‘logical’ (although harder to quantify) when viewed through a component level lens (I think things like local tissue strength is a smaller piece of the pie in comparison to exposure to sprinting and the ability to recover between efforts. Especially when we scale this chat to amateurs playing 90 mins on a Sunday who are out of puff after the first hard track back, but yeah nordics).

If we zoom out then, injury is an emergent property of interacting constraints. For example, strength of local tissue, fatigue, load distribution, surface conditions, tactical patterns, opponent behavior etc. The “mechanism” may be identical (eccentric contraction at long muscle length) but the ‘causes’ are distributed and numerous. True robustness then would only emerge across well trained subsystems but Identifying the ‘subsystems’ that need the most work are likely different for everyone and context dependent. Additionally, when we look at this research, to zoom out further, tactical and technical choices must be aligned with physiology and not imposed in opposition to it.

What I mean by the ‘technical choices must be aligned with physiology and not imposed in opposition to it’ is probably the biggest missing piece to understanding our limitations in practice. This is where S&C coaches who have incredible knowledge of the sport and it’s demands are gold. For example, to continue with football, despite what appears increased adoption of nordics and enhancements in tech, hamstring injury rates continue to increase at the highest level. I’d argue many team sports (at the highest level where this data maybe more relevant) have outpaced the current preparation models in the low zoom sphere that S&C often operates at.

Football has embraced larger squad rotations and more substitutions in game (since covid) which has increased game intensity (despite total distance running being similar - fig a). The aim to preserve game intensity is because we’ve learnt that you need to create something worth recovering from in the first instance. Meaning, if you win the exchanges e.g. first to the ball, you likely win the game. “Create something worth recovering from” was GB hockey womens gold medal winning mantra. Another example, Rasmus’ bomb squad changed the physical/time demands of a forward in rugby union.

The shift to the more explosive dominant exchange winning team player reflects the broader issue. The solution is not only to attempt to prepare athletes for the increasing demands of the game, but also to make sure we adapt the game to the actual capacities of athletes. It is no longer a starting team game but a contribution of intensity across the squad.

I think the very best sports coaches and interdisciplinary teams are starting to understand this and adapt i.e rotation is a deliberate strategy to spread minutes/work, challenging the ‘starting 11 culture’, and understanding the impact of tactics like a high press... but they can only do so much depending on rule limits e.g. only 6 subs. Ultimately, S&C needs to keep pace and operate within a systems level framework if ‘robustness’ is something we yap about. S&C plays a critical role in bridging the gap between the demands imposed by technical and tactical considerations and help navigate what is realistic given the capacities of individual athletes.

Across populations likely these priorities shift. I’ve said this before about research looking into risk factors, but it doesn’t scale very well across populations and individuals. If we were to generalise tho. For players at the highest level, hamstring strength, RSA, and chronic sprint exposure all matter of course, but currently outpaced IMO in comparison to the demands dictated by tactical decisions and the evolving nature of the game. For youth athletes with high sport specific practice but low strength training age, building foundational strength qualities in the gym is probably a bigger piece of the puzzle. For weekend warriors, where training is an opportunity cost, improving on feet aerobic conditioning may be more beneficial than focusing on hamstring strength in isolation.

Everything matters, nothing matters.

The issue with this sort of conceptual stuff is that it needs to be useable. We still need hierarchies of importance in practice but the point is to challenge the traditional perspectives. I think a lot of the time we’re throwing out words for the sake of it. Are we truly making someone robust?

1. Identify critical components for the athlete’s role/context.

2. Develop redundancy in those systems (multiple tissues, energy systems, movement solutions, cognitive strategies). This is why GPP from an S&C influence should always be a thread IMO (and to actually train qualities appropriately, yes nordics can be a small piece).

3. Train under perturbation, simulate fatigue, game constraints, environmental variability. Research suggests you need the exposure.

4. Integrate tactical and technical constraints with your prep.

5. Monitor adaptation and readiness as robustness isn’t static or exists in a vacuum.