Friday, June 22, 2012

RSA is overrated? Part 1

RSA is overrated? Part 1

This is going to be an article/research review (rant?)  that could be seen as an addendum to my Troubles with RSA I wrote last year. I suggest you check that one first before proceeding with this one. 

Checked it? Already? Ok, let’s clear some terminology first before we proceed. 

RSS – Repeat Sprint Sequence; a minimum of three consecutive high-intensity actions with a mean recovery duration equal to or less than 20s between efforts.

HIA - High-Intensity Action; runs performed at velocities >19.8 kmh-1 over a minimum duration of 1s. This is a ’tricky’ definition and I will come back to it.

HIB – High-Intensity Bout; same thing as RSS

RSA – Repeat Sprint Ability; The ability to recover and reproduce performance in subsequent sprints. There are different ways to quantify the RSA (mean time, fatigue index, decrement score) and there are a lot of controversies involved (which I covered in Troubles with RSA) along with ecological validity issues with most of the RSA tests.

RST – Repeat Sprint Training; training activity aimed at improving RSA

The questions to be asked are the following:

1.       What kind of RSS and HIA are happening during the game (frequency, duration, number of sprint, duration and activity during the rest, etc) and how important are they to the overall game performance taking into account position played

2.       To what physical qualities are those pattern CORRELATED (there are a lot of cross studies explaining this and I will not go in deep analysis of it)

3.       Do these patterns CHANGE over time under the influence of training and CHANGE in physical qualities we identified to be significantly correlated with them? This is the most important question that might give us some ideas about CAUSALITY between these two things. I am only familiar with Martin Buchheit et al. study that actually motivated me to write this blog entry. 

Let’s deal with question #1. What kind of patterns actually occurs during the game at the current level of understanding, measurement and analysis? 

There are a LOT of studies dealing with time-motion analysis, time spent and distance covered in different zones and I don’t want to repeat them here. What I do want to express here is that although there is a common belief that better (and/or more fit) teams (and players) will cover more ground during the game and spend more time in high-intensity zone. But actually, that is not true. Yes, you read it correctly – THAT IS NOT TRUE. Take a look at the study done by Di Salvo et al. which showed that better teams actually did LESS high-intensity running and sprinting during the game. 

Di Salvo V, Gregson W, Atkinson G, Tordoff P, Drust B.  Analysis of high intensity activity in Premier League soccer. Int J Sports Med. 2009 Mar;30(3):205-12.

The aim of the present investigation was to provide a detailed analysis of the high intensity running activity completed by elite soccer players during match-play. A further aim of the study was to evaluate the importance of high intensity running activity to overall team success. Observations on individual match performance measures were undertaken on 563 outfield players (median of 8 games per player; range=1-57) competing in the English Premier League from 2003/2004 to 2005/2006 using a computerised tracking system (Prozone, Leeds, England). High intensity activities selected for analysis included total high intensity running distance (THIR), total sprint distance (TSD) and the number and type of sprints undertaken. Total high intensity running distance in possession and without possession of the ball was also analysed. The THIR was dependant upon playing position with wide midfield (1,049+/-106 m) and central defenders (681+/-128 m) completing the highest and lowest distance respectively (p<0.001). High intensity activity was also related to team success with teams finishing in the bottom five (919+/-128 m) and middle ten (917+/-143 m) league positions completing significantly more THIR compared with teams in the top five (885+/-113 m) (p=0.003). The THIR and TSD also significantly declined during the 2nd half with the greatest decrements observed in wide midfield and attacking players (p<0.05). Both positional differences in high intensity activity and the observed change in activity throughout the game were also influenced by team success (p<0.05). The results of the present study indicate that high intensity activity in elite soccer match-play is influenced by both playing position and previous activity in the game. These activity patterns are also dependant upon success of the team. This may indicate that overall technical and tactical effectiveness of the team rather than high levels of physical performance per se are more important in determining success in soccer.

What we might miss with total and average scores and data are critical periods in the game and performance during them. For example, with total and average data measured we don’t see any fluctuations and variations/variability that might be more important than total and average scores.

For example, during the last 15-20 minutes of each half of the soccer game (especially in the last 15-20minutes) there is highest frequency of goals scored (click HERE and HERE). Accidentally or not, during that time there is the most decrease in high-intensity activity, whether due fatigue, pacing or strategy (we still don’t know – sad but true).

Edwards and Noakes

Well, we can’t see that from total and mean data analysis and that’s why I have issues with them. What if better teams showed less decrease in HIA during the last minutes compared to worse teams, besides having less HIA on average?  

Besides, we physical preparation coaches are more interested in EXTREMES of that distribution. We want to prepare our players for the most intense parts of the game, not for a game on average. F*ck the average scores. What we need are ranges and relative frequencies to identify most strenuous parts of the game. There is a great statistical saying that goes: if my head is in the oven and my feet in the freezer, on average I am fine. Yet there are still retarded coaches giving players 14km runs because players cover around 14km during the game. I am talking about that level of stupidity when using total and mean scores to created (cough-cough) sport specific practices/conditioning.   

Another problem is the method of how we get those numbers in the first place. Was it hand notation, Amisco, GPS,  Prozone? Another issue I have is with velocity based classification. For example, if HIA is defined as runs above 19.8 kmh-1 then time spent at high effort to accelerate to that velocity will not be classified as HIA. In other ways if you explode from standing to tackle an opponent for 5m you are out of luck – that will not count as HIA even if you POWER output was tremendous. I covered acceleration-power based time-motion analysis in THIS and THIS  post and I will come back to it later. We just need to think twice before we apply results of the studies in out training programs. Skepticism is good. 
 The problems with it is that stupid people are very confident in their opinions and smart ones are always in freakin’ doubt – that’s why people listen to stupid ones. Don’t be that guy – be confident with the players, skeptic with fellow coaches/scientist on the symposiums not in the locker room.

One more interesting thing which I will come back to as well is why HIA zone (or any other zones) set at absolute velocity (above 19.8 kmh-1) instead of relative one (for example above v30-15 for each player)? 
 Both option have pro’s and con’s and I think we need more time-motion analysis reporting both absolute and relative data. 

Stay tuned for part two…

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