The Training Process

The measurement of training load is often described as either internal or external. Internal training load monitoring is usually heart rate (HR) or RPE based and is often calculated with the integration of time, intensity and a weighting factor.  Intensity has been measured objectively using heart rate as it has been shown to have a linear relationship with oxygen consumption (Bot and Hollander, 2000), which is widely regarded as the gold standard measure of exercise intensity (Thompson, 2010). Consequently, the use of HR as a measure of intensity demonstrates validity. In recent years development of automated camera tracking systems, GPS and accelerometers have also brought the measurement of external training to the fore.

Examining the training process is essential to our understanding of why we measure training load. It is important that the correct questions are asked for us to arrive at the correct answers. The most common questions I am asked by coaches and scientists in applied environments (mainly soccer & rugby) are;

  • How much training is enough to maintain fitness?
  • What effect does the training during the week have on performance at the weekend?
  • What effect does a certain session or week of training have on fitness or fatigue?

The answers to these questions would provide very useful information for practitioners. So what do these questions represent?

In my view it represents a desire to understand the training outcome from a given dose (load) of exercise. This has been termed the dose-response relationship and deemed a fundamental principle of training by the American College of Sports Medicine (Thompson, 2010). It has also been suggested (Banister, 1991; Manzi et al., 2009) that a valid measure of “training load” should show a dose-response relationship with the training outcome. The training outcome is usually assessed periodically by measurement using an assortment of fitness tests or performance. This can give us an overview of the effectiveness of training, however daily monitoring of the training process (i.e. measuring training load) would give us deeper insights and help us understand what gives us the response we end up with.

The training process has been conceptualized quite nicely by Franco Impellizerri and colleagues (Impellizzeri et al., 2005). The model below shows how both the prescribed training and the characteristics of the individual (genetics, training status etc) combine to form the internal training load.

Adapted from Impellizzeri et al (2005)

This is best explained by the example of two people of different fitness levels running a 10km race at the same pace, both finishing at the same time. The fitter person would find this less demanding internally and analysis of heart rate data would show it lower than the other person. The model also shows how it is ultimately the internal training load that is the stimulus for training adaptation. . Therefore it is the internal “training load” that should be the measurement of interest if the dose-response relationship is of interest to you according to the above model. The methods employed to measure internal and external training load are reviewed in the training load section .



BANISTER, E. W. 1991. Modeling Elite Athletic Performance. In: MACDOUGALL, J. D., WENGER, H. A. & GREEN, H. J. (eds.) Physiological Testing of Elite Athletes. Champaign, Illinois: Human Kinetics.

BOT, S. D. & HOLLANDER, A. P. 2000. The relationship between heart rate and oxygen uptake during non-steady state exercise. Ergonomics, 43, 1578-92.

DENADAI, B. S., ORTIZ, M. J., GRECO, C. C. & DE MELLO, M. T. 2006. Interval training at 95% and 100% of the velocity at VO2 max: effects on aerobic physiological indexes and running performance. Appl Physiol Nutr Metab, 31, 737-43.

IMPELLIZZERI, F. M., RAMPININI, E. & MARCORA, S. M. 2005. Physiological assessment of aerobic training in soccer. J Sports Sci, 23, 583-592.

MANZI, V., CASTAGNA, C., PADUA, E., LOMBARDO, M., D'OTTAVIO, S., MASSARO, M., VOLTERRANI, M. & IELLAMO, F. 2009. Dose-response relationship of autonomic nervous system responses to individualized training impulse in marathon runners. Am J Physiol Heart Circ Physiol, 296, H1733-40.

THOMPSON, W. R. (ed.) 2010. ACSM's guidelines for exercise testing and prescription, Philidelphia, PA: Lippincott Williams & Wilkins.