Last week, our head of rugby in school invested in some alternate rugby balls, to aid player development. Within the set, there was one heavy ball, one light ball, one “no grip” ball, and one variably weighted ball (to be pumped up with water rather than air). While it might seem odd to train with something that is not used during the competitive environment (i.e. not representative), I believe it can add value, at appropriate times and in appropriate doses. Using alternate rugby balls within rugby training (other alternatives could be footballs, AFL balls, volleyballs, tennis balls, basketballs) could be considered a form of differential learning (DL). DL involves athletes practicing a particular skill in a variety of forms. Every repetition they do is different - the process is always changing, but the outcome remains the same. Athletes will find a movement solution that works best for them, given their own body, and the environmental conditions.
I briefly touched on differential learning during my post on variability. I have mentioned previously, but the whole concept of variability was the most challenging aspect for me to understand and articulate when I started my journey in skill acquisition. I very much had an opinion of progress from remedial to difficult, which is not really the case anymore (see below for clarification), and an athlete needs to master a skill in one context before changing the context. This is obviously quite a complex issue. When dealing with an athlete, I would place them in one of two buckets:
Learning to Coordinate: An athlete learning to coordinate is either a complete novice (thinking about an U6 rugby player, or even an adult player who is looking to change their technique). These athletes exhibit a wide range of movement variability combined outcome variability. Remedial, isolated, decontextualised (pick your term) training is of use for athletes in this bucket.
Learning to Adapt: An athlete who is learning to adapt is beyond the early stages of learning. They exhibit some movement variability, but their outcome variability is more stable. These athletes need variability to ensure they are put in situations where they need to adapt the movement behaviour but still achieve the same outcome.
It is important, therefore, to consider the initial skill level of your athletes (among other things), prior to deciding on a training intervention. DL is a training intervention that is useful only in the learning to adapt phase, in my view. For athletes in the learning to coordinate phase, DL will cause too much noise and potentially lead to a challenge point that far exceeds the athletes’ capabilities, potentially leading to negative consequences, like loss of confidence or drop out (more specifically for youth athletes).
DL can be used to increase variability, which aims to promote adaptability. Adaptability, in essence, is skill. Skill is the ability to adapt. Viewing training through a constraints-led approach, there are three categories we can modify to induce variability in a task: task, environment and individual (for more on CLA, see here). Using this model, Gokeler et al. detailed what changes could be made in each category for a DL approach to a broad jump (Gokeler et al., 2019) (see figure 1). (For further reading on motor learning principles in ACL rehab, see (Gokeler et al., 2023)).
Figure 1. DL applied to a broad jump.
Applying the same process to a SSG in rugby (or any other team invasion sport – Gaelic football, soccer, AFL etc.) we can look at how practitioners can incorporate DL into their practice, see figure 2 below. For more on practice design, see here.
Table 1. Sample variations that could be applied to SSGs.
DL is something that can be useful, provided it is used in the right context, with the right athlete(s), at the right time (day before a game may not be most suitable), and in the right dose (not suitable all of the time, be selective about when DL is implemented). Care must be taken about how and when it is applied. Two such considerations are the concept of representative learning design, and the novelty to promote attention and engagement.
Representative learning design: when using a games-based training format, there are quite literally an unlimited number of variations a coach can make to a game. However, the game that a coach is preparing for has a fixed set of rules, and there are a limited number of changes a coach can make before a task loses it’s representative value. One example is if a coach allows a rugby team to pass in any direction – this will ensure variability with catch and pass skills, but the critical information of a game has changed. Another example is allowing a Gaelic football/AFL team to throw the ball rather than handpass/handball it. Again, it will allow for variability in catching and passing, but the passing in particular will lose its representative value. To continue to add variability, even when the coach has exhausted task variations (or has found a game variation that pinpoints the area they want to work on) then a coach can modify the ball shape and size by using aforementioned alternate balls.
Saliency: I have spoken about how captivating attention is a crucial concept in coaching – where attention goes, learning flows. As Nick Winkleman says in his book “The Language of Coaching”: “..as coaches, one of our greatest tools for capturing attention is to simply change it up." If a coach is running the same game variation repeatedly throughout a season, because it carries a lot of value for their team, the use of DL can be very beneficial to add variability and to induce a novel aspect within the game to stimulate engagement from the players.
When embarking on my skill acquisition journey, the concept of variability, and in particular DL was something that I really struggled to understand.
When skill is clearly defined (i.e. the ability to adapt…), variability makes a lot of sense.
DL, for athletes at an appropriate skill level, in appropriate doses, at the right time, in the right context, can be a very useful strategy to promote variability and thus, adaptability in athletes.
It can be argued, especially when dealing with human beings (complex adaptive systems) that no two reps are the same anyway. And this is true, the same movement process is rarely repeated twice, there are subtle differences each time. But I think they key lies in the initial skill level and thus challenge point of the player. DL is a way to add further variability (and increase the challenge) to a task for skilled athletes, to force them to adapt. Referring to point 2, at the appropriate time and in the appropriate way, it can be useful.
A further question I would have however is in relation to DL and transfer. Early sport diversification is a common recommendation. This means a young kid has to adapt their movement strategy depending on the task, environment and their own body, whatever stage of development they are at. As I have mentioned when discussion transfer, many elite athletes have played multiple sports during their developmental years. Is sport diversification essentially DL in disguise? Perhaps a reader can share their views on this.
Gokeler, A., Neuhaus, D., Benjaminse, A., Grooms, D. R., & Baumeister, J. (2019). Principles of Motor Learning to Support Neuroplasticity After ACL Injury: Implications for Optimizing Performance and Reducing Risk of Second ACL Injury. Sports medicine, 49(6), 853-865. https://doi.org/10.1007/s40279-019-01058-0
Gokeler, A., Nijmeijer, E. M., Heuvelmans, P., Tak, I., Ramponi, C., & Benjaminse, A. (2023). Motor learning principles during rehabilitation after anterior cruciate ligament injury. Arthroskopie. https://doi.org/10.1007/s00142-023-00606-1