Understanding training load: How to learn to listen to your body better with internal and external load

Why do I need monitoring?

Monitoring stress and recovery responses in sport is crucial for the individual design of training interventions (Halson, 2014). During intensive training phases, trainers must find an important balance: on the one hand, promoting optimal adaptation processes, and on the other hand, avoiding overload and exhaustion (Buchheit et al. 2013). The precise interplay of training planning and control makes it possible to recognize training-related reactions at an early stage and adapt both training and recovery accordingly (Ferrauti, 2020). You can find out more about how we implement this at enduco in the blog posts Training planning and fitness, fatigue & form.

What exactly are internal and external parameters?

Ferrauti's book (2020) provides a clear overview of various monitoring parameters on page 167. These selected parameters are particularly suitable for the daily monitoring of external stress and internal stress.

Fig 1: External and internal monitoring (Ferrauti, 2020)

The external parameters mainly consist of objective metrics such as watts, pace and training duration. These metrics are summarized as training load and reflect the intensity of the training. In sports practice, subjective assessments of exercise intensity are also used in addition to objective metrics such as speed or wattage. This assessment is mainly based on the Rating of Perceived Exertion (RPE) scale according to Borg (1998). The training load of a unit is calculated by multiplying the subjectively perceived exertion value (RPE) by the training duration in minutes, which also allows the training load to be determined (Foster 1998).

Fig. 2: RPE scale according to Borg (Ferrauti, 2020, p. 391)

Physiological parameters such as blood markers, heart rate and mental recovery are used to measure internal stress. These parameters show how strenuous the training actually was for the body. The internal parameters are usually invasive and therefore not always practical to measure on a daily basis. For this reason, the focus here is on heart rate (resting HR, HR recovery, heart rate variability (HRV), submaximal heart rate).

Psychometric scales also support the control of the internal load, but require an appropriate selection of methods. They are generally easy to implement, but should be time-saving, as athletes often do not complete long questionnaires regularly. There are various established questionnaires that can reliably record significant changes in stress. At enduco, we use the Hooper Index, which is particularly sensitive to the athlete's stress development.

In summary, Impellizzeri et al. (2019) define the external training load as the prescribed physical work in an athlete's training program (i.e. the volume) and the internal training load as the athlete's psychophysiological response to this external load (i.e. the training dose). It should be noted that, regardless of the parameter selected, an individual baseline determination must always be carried out in order to be able to recognize meaningful changes.

You can find out which training metric - i.e. heart rate, watts, pace or RPE - you should use in the blog post on training metrics.