Saturday, June 23, 2012

RSA is overrated? Part 2

RSA is overrated?
Part 2

Now when I cleared (or made you more  confused about) some things regarding time-motion analysis and total/mean scores (without ranges, frequencies and zones), let’s deal with those most strenuous parts of the game. 

Defining what is strenuous is also tricky. Sprints, 1500m run, marathon, long jump they are all different in duration but done at maximum ability. They are all strenuous, but differently. The point is that we cannot say what is strenuous based on speed/power alone. Worse yet, we cannot say what is strenuous based on HR or VO2. Think about this like doing bench press for 5reps with 10RM weight and doing bench press for 9 reps with 10RM weight. In both cases we are using same intensity (10RM), yet the strenuousness (exertion would be better word) is way different. Besides, you would be able to do more sets with former example.

My point, if you are still following, is that exertion need to be defined by relative combination of both intensity and volume/duration. Lately, I was reading some papers on the Critical Power concept and it’s calculus for both continuous and intermittent activities (click HERE and HERE and if you have time also click HERE). I really like the concept of it because using simple formula you can predict time trials and average power/speed for activities of certain duration by knowing two factors – Critical Power and Anaerobic Capacity. I highly recommend checking the linked papers. 

Taken from Vanhatalo el atl. Application of Critical Power in Sport. Int J Sports Physiol Perform. 2011 Mar;6(1):128-36
By knowing critical power (CP or CV) and anaerobic capacity (W' or D'), we can estimate how strenuous was certain activity based on its velocity/power and duration.  This is especially interesting for velocities/power above Critical Power, because they dig intro limited anaerobic capacities. After certain action, or burst of intermittent actions we can predict how much of this anaerobic capacity is depleted (or fatiguing factors accumulated) and how much time it takes for recovery. This way we might get some insights on how really strenuous some parts of the game really are for certain player or how much he exhausted himself. Having this data may yield better information for the coaches regarding the individual level of fatigue of certain players during the game. The coaches might use that data to substitute them at the right time. This is why it is important to do time-motion analysis that takes relative zones into account, not only absolute ones.

Anyway, this might give us new ideas for the research. We still need more data on Critical Power concept validity and reliability, especially in regards to intermittent sports, along with finding better time-motion analysis methods that take power and acceleration into account.

To cut the long story short, for the rest of this article I am (along with other researchers) going to assume that the most strenuous part of the game is RSS/HIB or high density of HIA. If we only look at the total and average data for HIA, we might get that players perform HIA every 140sec on average.  That doesn’t look that though on the average, but this is the situation where we have head in the oven and feet in the freezer. We need to take a look at the distribution in time of those HIA. 

Unfortunately, there are not a lot of studies that report this kind of scores. Couple of them tend to find RSS (Repeat Sprint Sequences) in the game, their amount, durations, number, etc. One of the first studies I’ve read that actually reported this was by Gabbett and Mulvey. I am posting the abstract here. 

Gabbett TJ, Mulvey MJ. Time-motion analysis of small-sided training games and competition in elite women soccer players. J Strength Cond Res. 2008 Mar;22(2):543-52.

We investigated the movement patterns of small-sided training games and compared these movement patterns with domestic, national, and international standard competition in elite women soccer players. In addition, we investigated the repeated-sprint demands of women's soccer with respect to the duration of sprints, number of sprint repetitions, recovery duration, and recovery intensity. Thirteen elite women soccer players [age (mean +/- SD) 21 +/- 2 years] participated in this study. Time-motion analysis was completed during training (n = 39) consisting of small-sided (i.e., three versus three and five versus five) training games, domestic matches against male youth teams (n = 10), Australian national-league matches (n = 9), and international matches (n = 12). A repeated-sprint bout was defined as a minimum of three sprints, with recovery of less than 21 seconds between sprints. The overall exercise to rest ratios for small-sided training games (1:13) were similar to or greater than domestic competition against male youth teams (1:15) and national-league (1:16) and international (1:12) competitions. During the international matches analyzed, 4.8 +/- 2.8 repeated-sprint bouts occurred per player, per match. The number of sprints within the repeated-sprint bouts was 3.4 +/- 0.8. The sprint duration was 2.1 +/- 0.7 seconds, and the recovery time between sprints was 5.8 +/- 4.0 seconds. Most recovery between sprints was active in nature (92.6%). In contrast to international competition, repeated-sprint bouts were uncommon in small-sided training games, domestic competition against male youth teams, and national-league competition. These findings demonstrate that small-sided training games simulate the overall movement patterns of women's soccer competition but offer an insufficient training stimulus to simulate the high-intensity, repeated-sprint demands of international competition.

What this paper shows, besides that you cannot solve all the physical preparation needs by playing only small sided games, is one of the first analysis of RSS during the games. It showed that we have 4.8 repeat sprint bouts per player per game on average. The number of the sprints in those RSS is 3.4 on average. This is a great starting point. 

I will leave you with this till next time, when I am going to write about the new study by Christopher Carling et al.

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