By Scott Daly (@DalyScott), Lead Sports Scientist at Oxford United Football Club.

Firstly, I would like to say that this article is not intended on being an example of ‘best practise’, it is simply how we have tried to keep players fresh and ready to play. I am very open to criticism so long as it is directed in the right way, I have plenty to learn as a practitioner and hopefully this article can spark some interesting conversations. I look forward to the aftermath!!

Football is a sport where athletes are paid vast amount of money to perform to the masses in what is the most popular sport worldwide. The number of games played in a domestic season can range from 40 to 60 games per season dependant on cup runs etc. With players often competing biweekly, the need to monitor workload to optimise training sessions and reduce to likelihood of injury in and between competition is of upmost importance to clubs. Recent research has investigated what is being named the Acute: Chronic ratio (A:C) and how it may be used to optimise training so that players receive appropriate loads on an individual basis. I intend on using this article to highlight how we at Oxford United have been using this research to help with our training loads. Come April 30 the club will have had to contend with a 62 game season, of which, in a 15- week period between January and April, 13 weeks consisted of Saturday Tuesday fixtures.

With regards to the A:C and how it can be implemented to ensure that all payers are receiving adequate load in a week it is important to firstly explain how the A:C is monitored. A rolling 4- week average is calculated and is known as the chronic load, while the acute load refers to training load from a 1- week period (Calvert, Banister, Savage & Bach, 1976). It has been stated that when acute loads exceed chronic loads the likelihood of injury rises (Hulin, Gabbett, Lawson, Caputi & Sampson, 2016). Specifically, when the acute load exceeds 1.5 it has been stated that the likelihood of injury increases three to fivefold (Hulin et al., 2013).

The term optimising load is often viewed as restricting the amount of load players are subjected to in order to reduce overuse injuries. However, as is often the case, players not in the starting team require increased training loads to make up for the lack of playing time. The likelihood of players picking up injuries during a competitive season is likely to be related to the recovery time between competitive games and also the workloads that the players are subjected to between these competitive games (Hulin, Gabbett, Caputi, Lawson & Sampson, 2016). Cormack, Newton, and McGuigan (2008) state that 3-5 days of recovery are required in order for neuromuscular and endocrine functions to return to pre-match status. However, Football players often have to perform on less recovery time than this and so the need to understand how best to cope with this demand is essential. Interestingly it has been recently stated that high workloads act as a protective barrier during periods of heavy congestion and so, the need to ensure that all squad players have a relatively high chronic load becomes apparent (Hulin et al., 2016). Williams, West, Cross and Stokes, (2017) recently published an article stating the need to ‘bin’ the term overuse injury and rename it a training load error and based on recent research, this may be appropriate as underuse injuries are as much of a threat to players as overtraining injuries.

Within a squad, as a season progresses, it is commonplace for managers to limit rotation and to settle on their preferred starting team. This leads to many players missing out on game time at the end of the week which is ultimately the highest daily load in terms of distance as well as high speed running. With unused or partially used players missing out on such a large amount of load it is important to ensure that they receive adequate training or conditioning in the day’s post- game in order to maintain high chronic loads. By ensuring that players maintain high chronic loads in the absence of playing time, if and when they are called upon, the addition of game time should be less of a shock to the system and more importantly will not result in a sudden spike in load. It is important to understand that the A:C is a theory, and as such, it can be applied to multiple measures as the theory is based on simple principles of progression over time. Distance, as well as High Speed Running (HSR), are two variables worth considering when applying this theory in a practical setting. While being accustomed to large relative distances on a weekly basis may act as a protective barrier during periods of high fixture congestion, it is important to remember the role of intensity. HSR has been linked with team success in professional football as well as separating players’ standards of play, with research stating that elite players producing more HSR than sub- elite players. Furthermore, ensuring that players are hitting maximum velocities in training could possibly act as a protective barrier to hamstring injuries in games where players will be expected to perform high amounts of intermittent high speed running. By managing high chronic distances, HSR and Max Velocities in a sensibly periodized programme, theoretically, players should be safer and much better at tolerating the demands of a heavily congested season.

How this could be practically applied to a team sport and in particular, when dealing with a large squad is the skill of the sports scientist/ strength coach.

A:C Ratio

Figure 1. Chronic load for a squad of players. Blue bars are reaching appropriate levels of load while the black bars are in danger zone of undertraining

From figure 1. Which is real world data from a set of players, it is clear to see that overtraining is not the issue as players are all within their chronic load thresholds, however, undertraining within the non-playing group is a concern. While figure 1. illustrates the average chronic load for 4 weeks of data, it is important to understand how this load relates to the acute load. Understanding the interactions between the chronic and the acute load and how much volume is required to truly protect the players from spikes in data is the important consideration when evaluating an athletes’ chronic load. From my experience players tend to fall between 25km and 30km per week of total distance if they are playing biweekly on a regular basis. What this means is that the when the chronic load is being considered, it should be at an appropriate level relative to what the ‘worst case scenario’ is going to be. By ensuring that players are capable of ‘worst case scenario’ figures, we are protecting them from spikes in load as best we can.

A:C Ratio

Figure 2. The A:C ratio for players based on the chronic load observed in figure 1. for an individual week

The A:C ratio is the aspect of monitoring where decisions are made on training status, chronic load is important long term, however, understanding how to get players to reach high levels of chronic load safely is where injury risk is minimised. As can be seen from figure 1. And figure 2. the players represented by the second and third bar/ dot have low chronic loads, however interestingly their A:C ratio falls either slightly above or in the sweet spot of training. This is an important consideration when dealing with players training status. At first glance it would appear that the players in question require additional conditioning, however, closer investigation reveals that player 2 is already receiving overload in this weeks’ training while player 3 should possibly have been conditioned further. This is one way in which the A:C monitoring tool may provide benefit in an applied setting, by giving coaches objective data which can be actioned appropriately. This concept of ensuring players are not exceeding a ratio 1.5 or falling under .9 regularly is important in season, however, during pre- season and periods of overload it is important that adaptation is the main focus for training and so, players should be subjected to loads which, will inevitably, force the body to recover and adapt to the imposed demand. It is important to remember the limitations of the A:C monitoring tool, ensuring that a periodized schedule of training is adhered to with peaks and dips in load and intensity is important and is something that the A:C ratio does not take into account. A well- structured plan of training is the task of the strength and conditioning coach and knowledge around energy system development should remain at the forefront of a coaches planning.

The problem around non-used players not receiving adequate loads when not involved in the starting 11 may be solved via the addition of reserve games or indeed conditioning games and/ or additional isolated running based conditioning. The issue around game based conditioning the non-used players is that the number of players for training are limited due to the playing group recovering and so, small sided games are often the go-to modality of training. These small sided games overload acceleration and decelerations as well as increasing the number of actions players perform each minute, however, the problem with players not hitting adequate distances, as well as HSR, remains. For this reason, large blocks of tempo training alongside small sided games may be essential in achieving large distances of running as well as incorporating Football specific training.

Ensuring that players are subjected to intensity as well as volume will go a long way toward limiting the risk of injury when and if they find themselves playing 2 games in a week having been sat on the bench for weeks in advance. It is important to train hard, however, it is essential that players train smart as well.

So what does a week look like for players involved and not involved in games;

A:C Ratio

When setting out conditioning for players not used on a match day clear communication is essential between Sports Science staff and management so as not to overly condition a player on a Monday who will be playing on the Tuesday. The above are example weeks utilised with players who we know are either in or out of the team. Starting players will usually go outside to complete a light training session as part of their recovery unless extenuating circumstances apply such as consecutive weeks playing Saturday, Tuesday, severely low wellbeing and/ or signs of overtraining physical or psychological. It is our philosophy that players should complete outdoor light sessions on an MD+2 wherever possible as a way of increasing their chronic load and also so not to encourage a fragile mentality towards recovery and training. However, as is often the case ‘it depends’ is forever in our thinking and certain players will be kept off feet if and when it is warranted.

Our decision making on whether players receive extra conditioning is driven by the A:C model, this means we can adapt training daily/ weekly and not be dictated to by a pre- determined model of periodisation. To put this into real terms, if a player has featured consistently for a few weeks and is an unused substitute in a game, the mind- set would be to give that player the rest while we have the chance. With games being played Saturday- Tuesday- Saturday regularly the odds are that player will feature again in the coming match. However, if the player has been dropped and does not look to feature in the coming games, our decision may well be to rest them for a week in order to de- load before regular conditioning commences with continued time out of the team. One thing that the A:C ratio does not take into account is periodisation and the concept of super- compensation. Recovery periods have been hard to come by for us this season having played 62 competitive games in a 9- month season and so when the opportunity to give players rest presents itself it would be very foolish if we did not take it. The chronic fatigue accumulated over the course of a season for regular starters is significant and ensuring that they stay mentally and physically fresh is a real challenge. While rest is the prerogative for regular starters, unused subs and squad players who receive very little competitive football are subjected to countless bouts of conditioning and small sided games with the aim of achieving adequate loads on a weekly basis. It would be very easy on paper to say that if the subs do not feature in a game that we should bring them in the next day for training and conditioning. However, when the psychological aspect of not featuring in games is taken into account there is a good chance that players would lose motivation, end up resenting the club and in time develop an ‘us and them’ mentality towards the starting players and staff. This aspect of coaching cannot be overlooked, people first, athletes second is and always will be my mantra. The players know they need to work hard in order to stay fit when called upon, doing it in the right way can make all the difference between having a culture of hard work and enthusiasm and a culture of resentment and ‘bitching’.

While the above examples of training week will undulate and be progressed and regressed throughout a season the layout will remain the same. Anecdotally speaking players have appeared match fit and have not shown signs of being underprepared in games. The only instances where players may have appeared off the pace is if they have not been involved in competitive games for a long period of time, which has been the case for 2 players this season in particular. In each of these cases the chronic load for distance as well as HSR were maintained through our conditioning programme, however, the demands of the game after such a long time without competitive minutes resulted in each player complaining about not feeling ‘sharp’ and that the last 10 minutes of the game were extremely difficult. As a coach I can accept this as I would not expect players to be ready to perform to their maximum in pre- season fixtures so why should players not receiving competitive minutes over a long period be any different? In my view, we maintained levels of fitness and ensured that when the players were called upon they were not at an increased risk of injury as best we could. Game sharpness comes with playing competitive games, it is another aspect of a players’ readiness to perform and very difficult to replicate in a training session with limited numbers of available players.

In summary, the A:C model plays a large role in how we condition players and try to ensure that players are not subjected to spikes in load after long periods without competitive games. The use of SSG, as well as MAS type conditioning, ensures that we are able to cover both large amounts of HSR as well as overload accelerations, change of direction alongside the decision-making component of Football. Maintaining a culture of hard work, togetherness and enthusiasm are paramount and as such decisions on training will be weighed up with the psychological impacts of continued conditioning without the reward of game time.