Internal and external load: The power of integration
In the last blog, we have discussed how benchmarks can help you plan your training program ahead. Furthermore, in previous blogs, we have also discussed the added value of using both GPS-data and subjective data to monitor your team. However, we have not discussed how you can check whether your program resulted in improvements in fitness. In today’s blog, we will discuss how the integration of internal load and external load (the GPS variables with measures of perceived training load) results in new insights.
Combining internal and external load
Assume you’re analyzing the GPS-data of the last week, and suddenly you notice that all players performed substantially less workload than in the weeks before. Or the heart rate of your players is substantially higher than usual. Does this mean that your players are less fit than previously? Or was it the training schedule that caused these differences? Based on the GPS-data or heart rate data solely, it is hard to tell what caused the differences. However, by collecting data on both GPS-data and how the players perceive the load, we are able to determine what caused the difference.
In sports science literature, the distinction between internal and external load is made. The external load refers to the load the players have actually performed (total distance, sprinting distance), whereas the internal load refers to the way the players perceive this load (heart rate and Rating of Perceived Exertion (RPE))1. By seeing the external and internal variables in relation to each other, we get insights into the fitness of the players.
If your players perform less external load than they usually do, but they also perceive the training as easier (i.e. lower heart rate or lower RPE values), this likely means that the training schedule was the cause of the decline in load (see figure 1). Try to increase the training load in the coming week to avoid detraining effects. In contrast, if your players perform substantially less load than usual, but they perceive the training the same way as usual or even as ‘harder’ (higher heart rate scores or higher RPE values), this should signal you that the fitness of your players is deteriorating. The other way around is also true: do your players perform the same load as usual, but do they perceive the load as ‘easier’ (lower heart rate or RPE), this means that their fitness has improved.
RPE or Heart Rate?
Even though in most cases heart rate and RPE can both be used to track the internal load of the player, there is one exception to this. In case your training session focuses on explosiveness, heart rate is not the best measure of internal load. Since heart rate is a measure of oxygen consumption by the body and the fact that the energy for short explosive actions is mainly produced without oxygen, heart rate is not the right indicator of the internal load for these sessions. Rather, the load that is placed on the muscles and tendons is of importance: the muscles need to deliver a high power output, whereas the tendons need to handle high forces. Fortunately, these aspects of load are included in the RPE score. Therefore, RPE is a better representative of the internal load in these cases.
In previous blogs, we have discussed that internal and external load provide valuable information apart from each other. In today’s blog, we have shown that the integration of both variables leads to even more powerful insights. Furthermore, we have seen that when the training focuses on explosiveness, heart rate cannot be used as an indication of internal load. In that case, RPE should be used as an internal load measure.
Start monitoring your team from several perspectives to get the most comprehensive picture of their physical status!
Impellizeri, F.M., Rampini, E. & Marcora, S.M. (2005) Physiological assessment of aerobic training in soccer. Journal of Sports Sciences. 23(6); 583-592.
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