Club and Country: Collisions are the Consistent Contrast

The typical narrative in the media is that international rugby is ‘more intense’.

This can be true – but our definition of intensity is important here. If we take a step back and use some data to try to help us support or refute this narrative. What are the differences in physical characteristics at different competition levels in rugby union? 

One of the main challenges that players, coaches & support staff have is preparing for different demands from club competitions and international fixtures. Particularly, the rapid transition between competition types.

The November International period and the 6 Nations are two prime examples of this, where players can transition between club & country environments.

International fixtures have different physical characteristics and tactical considerations compared to club competitions. The seamless transition of players between club & country environments is not only essential to support players to perform at their best level and reduce injury risk, but also to support the changing training & match demands they will face to support success for the team.

Collision detection from microsensor technology

One of the first things to establish is the accuracy & reliability of collision detection from micro-sensor technology. Most practitioners, athletes & coaches are highly familiar with distance & speed derived measures.

Metrics such as total distance, high speed running and top speed are commonly used and discussed across sports, from athletes & practitioners to supporters & commentators. However, familiarity with collisions and other accelerometer-biased metrics are less utilised.  

A lot of published research within rugby union describes the physical characteristics using locomotor metrics derived from microsensor technology, whilst there is less research using the collision metrics of rugby union using microsensor technology.

For some of my PhD work, we explored the relationship between Collision Load (AU) and Collision Count (#) derived from Statsports. The count of collisions and the Collision Load™  derived from STATSports were very strongly-nearly perfectly related (r=0.91 and r=0.89 respectively) to expert-coded count of collisions by performance analysts in rugby union match-play. 

Collision Load can be defined as a single score for the total physical demand of contact. It combines collision loading, how long collisions last, how fast the player enters contact, and how hard the impacts are across multiple directions. A higher score means more demanding contact.

Collision Count can be defined as the total number of detected collisions in a session or drill.

We also noted positional differences in the typical Collision Load per collision event. Collision Load  values were on average higher in Backs compared to Forwards.

Some of these higher averages may arise from Backs entering collisions at higher velocities. Despite this, we still see Forwards have a higher overall Collision Load from training and matches.

This information can be valuable to adjust training loads across the week, but also to plan recovery post-match based on physical output. Players who are involved in more collisions will likely have different recovery timelines, and the strategies they use to accelerate recovery should be different.

Preparing for competition

Getting a better understanding of the physical characteristics & intensity during competition is essential to ensure practitioners & coaches can assess if their training is preparing athletes sufficiently. This training approach will differ based on coaching staff and tactics primarily, but also will depend on what competition level athletes are preparing for. 

To better understand the different competition characteristics, we examined 12 of the most common microsensor technology metrics collected via STATSports: Total Distance (m), high speed running >5m/s (m), very high speed running >6m/s (m), sprint distance >7m/s (m), accelerations >2m/s2, accelerations >3m/s2, decelerations >2m/s2, decelerations >3m/s2, collisions count (#), collision load (AU), high metabolic load distance (m), high metabolic load efforts (#); all reported as per minute.

The 4 competition levels we compared from lowest to highest level were British & Irish Cup (B&I), Pro14, European Rugby Champions Cup (ERCC), and International (INT).

Despite the common narrative, the data we explored actually showed that the international competition is actually less intense, when it comes to distance, high speed running and sprinting.

As competition level increased, running intensity actually decreased. However we did see an increase in collision intensity, both from a count and load perspective. At the highest level , collisions may be the biggest differentiator.

We interestingly also saw a greater density of high metabolic work. High metabolic load distance (HMLD) and high metabolic load efforts (HMLE) are defined as follows:

HML Efforts – The number of times that the player completed a running effort that exceeded both the minimum effort duration and the high metabolic load threshold – default values are 1 second minimum duration and 25.5w/kg high metabolic load threshold.

HML Distance – The distance covered when the player completed a running effort that exceeded both the minimum effort duration and the high metabolic load threshold – default values are 1 second minimum duration and 25.5w/kg high metabolic load threshold.

International rugby has the highest high metabolic load density; defined as the number of HMLE divided by the HMLD.

Players competing at higher competition levels need to produce greater number of efforts, more frequently.

For every 100m of HMLD, the international player on average would have to accumulate that distance with 3 more efforts compared to someone at a B&I cup level.

Transitioning between club & country

The data demonstrates that competition level physical characteristics are different, and thus require not only specific tactical preparation, but also physical preparation. Specifically, players entering into international competition may need to prepare for the higher collision demand and effort density.

Whilst the global rugby calendar is evolving & shifting, players still will have periods of rapid transition from club to country.

In this November period, the United Rugby Championship, English Premiership and French Top 14 all have fixtures the immediate weekend prior to the first round of Autumn Internationals, with the French Top 14 even overlapping one weekend.

The same can be said for the 6 Nations, where the ‘break’ in the competitions fixtures contains a weekend of club fixtures, where players who may have limited game minutes will often return to clubs to play.

These transitions – into country environments, back to club environments, and the varying turnarounds – are challenging for players, coaches & support staff.

How are players’ loads managed when one competition requires significantly more running and high speed running compared to the higher collision intensity & density of efforts in another?

As practitioners, we know that rapid and large changes in physical load can increase fatigue & potentially risk of injury. I’m going to list a few questions to spark thoughts & hopefully some discussion.

• What can we do to reduce the rapid changes when players transition to compete at international level? 
• Do we increase collision loading during training, but risk adding additional fatigue leading into important club competition fixtures?
• How do we prescribe recovery for athletes after fixtures & training that have higher high speed running volumes, compared to higher collision loads? 
• Do our physical prep strategies change week to week?

A player’s journey for this November could look like:

Weekend of 30th October – club fixture

Weekend of 6th November – international fixture

Weekend of 13th November – international fixture

Weekend of 20th November – international fixture

Weekend of 27th November – international fixture

Weekend of 4th December – club fixture

A player’s journey for the 6 Nations could look like:

Weekend of 16th January – club fixture – European Champions cup

Weekend of 23rd January – club fixture

Weekend of 30th January – club fixture

Weekend of 5th February – international fixture

Weekend of 13th February – international fixture

Weekend of 20th February – international fixture

Weekend of 27th February – club fixture

Weekend of 5th March – international fixture

What does a higher collision intensity cost?

Given what we have described in terms of the different physical characteristics at different competition levels, and also some of the challenging performance questions we as practitioners have to face – we also need to look at the cost associated with these different loading exposures. 

The higher collision demand at higher competition level will not only impact training preparation, but also recovery too. Specifically regarding nutritional strategies. We know that collisions massively increase energy expenditure – some research has shown the inclusion of 20 collisions increased energy demand by on average 1200 kcal.

When you consider that increase of energy expenditure not only from the match day, but also from the potential increase in contact during training to prepare for competition – this could have a significant impact on caloric balance for players. 

I’d also expect to see different preparation & recovery strategies to support the different characteristics.

For example, international teams may bias more intensive drills (higher density) and more contract preparation, to acutely prepare for matches. This may differ from club teams who may bias more extensive drills (larger spaces) to allow & expose players to the greater high speed running demand they need to prepare for. 

In the below chart, there is data for one front-row forward competing across 3 different competitions. It is clear to see for this player, his Collision Load is much higher at International level, compared to club competitions.

Based on this data, we know that the fatigue & cost of matches at international level will be much greater, and his recovery strategies & timeline will be different. This may look like additional nutritional intake after international games, and targeted recovery strategies to accelerate the repair from impact-induced muscle damage & soreness.

Incorporating collisions into preparation, management and research

If we actually consider what a week of preparation & management might look like, the above image is a visual representation of the collision Load across a match week. 

Given the higher contact loading during match-play, it may take a little longer to recover. Many teams will target higher volume training on either MD+3 or MD+4, depending on turnaround times. MD+2 and MD-1 are typically non-contact sessions, but will still have elements of running, technical and tactical training.

There is a fine balance between allowing extra time to recover from the increased collision load from match play at international level, but also exposing & preparing players for the increased intensity with more contact training during the week.

Another example of planning training within the week would be mapping out your high volume / intensity days for both running and contact. In this example above – I’ve used Total Distance and Collision Load. Our match day is the highest load exposure for players from both a running and collision point of view.

Below is an example of how this might look at an amaetur level, where athletes train only twice per week, and typically play on the weekend.

Whatever your training week, frequency or structure – the ability to measure and plan collision loading alongside running volumes is valuable. Especially with planning additional conditioning top-ups to address any gaps in training compared to match, and preparing and reintegrating athletes through rehab from injury.

For example, if a weekly distance load is around 25 km and collision load is around 500AU, gradually returning athletes closer to these loads in a structured way may help reduce risk of injury and preparedness following injury.

From a research perspective, there has been plenty of data examining the relationship and effect of different locomotor demands related to injury risk.

Concepts such as acute:chronic workload ratio, week-to-week changes in load, and normal ranges have all been established for total distance, high speed running, sprint exposures, and accelerations & decelerations. Yet despite our understanding of the increased fatigue & energetic cost of collisions, we are yet to have such a base of research exploring & linking this collision loading combined with locomotor outputs to better explain injury risk.

The count of collisions and the Collision Load™  from STATSports could be used in addition to GPS-derived metrics to model players’ injury risk, and be used to enhance how practitioners design and prescribe position specific conditioning and rehab sessions. 

Key take-aways

1. Higher level competition is more intense – but our definition of ‘intensity’ is important. In Rugby Union, it seems that higher competition levels are characterised by higher collision loads and high metabolic load efforts, as opposed to higher running and high-speed running demand.
2. Collision Load™ (AU) and Collision Count (#) derived from Statsports demonstrate very strong-nearly perfectly correlations (r=0.91 and r=0.89 respectively) to expert-coded count of collisions in rugby union. These measures can be used to measure the contact loading of rugby players alongside locomotor demands.
3. Whilst Forwards accumulate greater collision loads during match-play, Backs’ collisions are typically more intense (per contact0. 
4. HML density (calculated as HMLE divided by HMLD) shows a linear increase with increasing competition level. The international game could be described as more “dense” than club competition.
5. Collisions are highly fagituing and come at a high cost. Practitioners & athletes should consider accounting for collisions in recovery, with regards to nutrition & specific strategies.
6. We need more data to understand and model injury risk combining running load and collision load

References

1. Tierney P, Blake C, Delahunt E. Physical characteristics of different professional rugby union competition levels. J Sci Med Sport. 2021 Dec;24(12):1267-1271. doi: 10.1016/j.jsams.2021.05.009. Epub 2021 May 23. PMID: 34144858.
2. Tierney P, Blake C, Delahunt E. The relationship between collision metrics from micro-sensor technology and video-coded events in rugby union. Scand J Med Sci Sports. 2020 Nov;30(11):2193-2204. doi: 10.1111/sms.13779. Epub 2020 Aug 11. PMID: 32713044.
3. Costello N, Deighton K, Preston T, Matu J, Rowe J, Sawczuk T, Halkier M, Read DB, Weaving D, Jones B. Collision activity during training increases total energy expenditure measured via doubly labelled water. Eur J Appl Physiol. 2018 Jun;118(6):1169-1177. doi: 10.1007/s00421-018-3846-7. Epub 2018 Mar 22. PMID: 29569055; PMCID: PMC5966477.