#### Football data analysis with GPEXE software

##### The data summary provided by the GPEXE system for the single track

The quantitative evaluation of a training session or a fraction thereof yields an in depth analysis. The assessment of total distance and heart rate as a function of time, provide a distorted image of the overall energy expenditure and the average metabolic power. However, thanks to further processes, this information can be rendered more accurate and complete. Let’s see below the description of the information available thanks to GPEXE football analysis software, referring to the example reported in the image below.

#### Distance

It represents the actual distance covered by the athlete during training or a section thereof. In the example, the player has covered 597 meters in 4 minutes and 46 seconds.

#### Av. Speed

It represents the average speed maintained by the athlete during training or a section thereof. In the example, the player has maintained an average speed of 7.51 km/h.

#### Av. HR

It represents the average heart rate (HR) of the athlete during the training or a section thereof. In the example, the player has maintained an average heart rate of 150 b/min. This data is recorded by GPEXE football analysis software when the athlete is wearing a Polar heart rate monitor belt coded T31/H1/H2/H7.

#### Av. Power

It represents the average metabolic power sustained by the athlete during training or a section thereof. In the example, the player has maintained an average power of 10.86 W/kg. The metabolic power is calculated by GPEXE football analysis software every 50 msec according the model proposed by Prampero (2005) and recently perfected. Starting from the instantaneous speed and the energy cost, it is possible to estimate, instant by instant, the istantaneous metabolic power required for the athlete to move at a certain speed and the given accelerations. As pointed out on several occasions, the estimated energy cost due to the acceleration is particularly important for the player because, especially in specific exercises with the ball, there is a continuous variation of speed (and consequently alternation of acceleration/deceleration). Having a tool that can accurately measure the acceleration/deceleration becomes indispensable if we want to identify with precision the cost of these actions; it should be noted that the energy cost for maximum acceleration values can attain values up to 10-12 times greater than that applying for constant speed running.

#### Total Energy

It represents the total energy spent by the athlete during training or a section thereof. This takes into account both the energy required to cover the given distance (as if it were at constant speed), and the energy needed to support variations in speed changes (which require a larger energy expenditure).

#### Equivalent Distance

It represents the distance that the athlete would have covered with the same overall energy expended running at constant speed. As an example consider two players (A and B) who have covered 600 meters during a training exercise; however the energy expenditure of the two players was different: 3.000 J/kg for player A vs 3.150 J/kg for player B. This means that, assuming the energy cost of running at constant speed to be equal to 4.64 J/(kg·m), if the two players had used the amount of energy indicated above to run at constant speed, player A would have covered 647 meters while player B would have covered 679 meters. It is clear that this parameter is a more intuitive way to express the energy spent by the athlete during a training exercise or a fraction thereof; the higher the equivalent distance, the higher the energy expenditure of the athlete! In the example above, the player considered has spent a total of 3,106 J/kg and has covered 597 meters. Had he spent the same energy running at constant speed, he would have covered 669 meters.

#### Equivalent Distance Index (EDI)

The ratio between the equivalent distance and the actual distance, provides us a percentage index (in the example it is reported in parentheses next to the value of the equivalent distance). This percentage indicates how much the equivalent distance is greater than the actual distance covered (in the example above 669 meters are 12% greater than the actual distance of 597 meters). Why is it useful to calculate this ratio? Because the larger the difference between actual and equivalent distance, the greater of high energy expenditure actions (typically accelerations). In this way it is possible to identify players or training modes having different accelerations characteristic.

#### Anaerobic Energy

It represents the energy that the athlete has consumed above its critical power (power corresponding to the anaerobic threshold determined by a specific test). This value indicates substantially the amount of energy of anaerobic origin (alactic and lactic). This parameter allows one to gain personalized information about the involvement of the specific anaerobic mechanisms: the higher this involvement, the more “stressful” have been the exercising or training sessions for the athlete.

#### Anaerobic Energy Index (AI)

The ratio between the anaerobic energy and the overall energy expenditure provides one with a percentage index (shown in the example in parentheses next to the value of anaerobic energy). This indicates the fraction of energy derived form anaerobic energy sources (in the example 669 J/kg represents 22% of the total energy of 3,106 J/kg spent during exercise). Why is it useful to calculate this ratio? Because the larger the fraction of anaerobic energy spent by the athlete, the greater the amount of energy derived form lactic and alactic sources; i.e. above the anaerobic threshold.