“Metabolic Power takes to the field” is part of a series of webinars held by Cristian Osgnach to go deeper on the workload analysis and the concepts of metabolic power and high-intensity through specific examples on the field.
Workload monitoring is one of the main goals for a football fitness coach, keen to use any tracking system. The interest is to evaluate the overall volume or, referring to the energetic approach, to identify the high-intensity volume. The parameters used to estimate the high-intensity are crucial to better understand the characteristics of the proposed exercise: one of the most common is the number of acceleration. Accelerations have some limits, though and we are going to describe them more clearly through the following exercise.
To recap, the main points of the “fast & loose” running exercise are:
- football pitch full length,
- 3 alternated acceleration + deceleration phases (18+18 meters each).
Let’s analyse a single repetition in detail.
The athlete starts from a standstill, after the acceleration phase he reaches a peak speed of 7 m/s, a deceleration phase follows, and then the second acceleration phase starts from a speed of about 3.5 m/s, to reach the same peak speed of 7 m/s again. The same happens in the third acceleration phase, then the last deceleration brings the athlete to the end of the pitch (speed =0).
The best way to understand the link between speed and acceleration is to refer to a maximal sprint (see fig. 2). On the left, the time course of the speed: the athlete starts from a standstill, then the speed increases exponentially until it reaches the top speed after 6/7 seconds. On the right, the time course of the acceleration: the athlete attains a maximum acceleration in the beginning; as the speed increases, the acceleration decreases to zero, once the maximal speed is attained.
Let’s merge speed and acceleration in a single graph: the speed on the X-axes and the acceleration on the Y-axes. The relationship between the two is a straight line which expresses more clearly what previously represented in two separated graphs (ASP = Acceleration Speed Profile).
The most obvious question now is: “how many high-intensity actions are expected in the fast-and-loose exercise?”
Accelerations. As mentioned before, the only acceleration event detected in the single sequence is the first (i.e. the athlete starts from standstill). The other two accelerations do not meet the criteria of acceleration event and are not identified. Any smart solution to fully get the feedback we need?
Power events . By means of the power events, all the high demanding actions are correctly detected (see fig. 3).
At this point, if the goal is to describe the high-intensity actions, we have two options. On one side, we can get 6 accelerations events, while, on the other, we can get 18 power events.
We need to understand what is the most convincing approach according to our way of measuring the performance. Let’s have a look at the following video.
The above should make us think on the choice of the best criteria to describe in detail the high-intensity actions.
Read Part I and Part II of the series.
C. Osgnach, “How to detect the high intensity“
C. Osgnach, “A simple intermittent exercise analysis: gpexe vs traditional metrics“