Edwards TRIMP

Edwards (1993) proposed a zone based method for the calculation of TL. The time spent in five pre-defined arbitrary zones is multiplied by arbitrary coefficients to quantify training load. The proposed the zones based on HRmax with 10% zone widths and corresponding coefficients as can be seen in the table below.

HR Zones












This method gained popularity as the default setting on a popular HR system. However the coefficients are void of physiological underpinning and the zone limits remain predefined and void of any metabolic or physiological performance thresholds. Such zones and weightings would imply the training adaptation in zone 5 is five times greater than in zone one and that the relationship between training intensity. However no study to date has proven this to be case. The weightings used by Edwards (1993) are not validated through a relationship with a known physiological response. Neither has a training study looking at the quantification of the TL from this method been conducted to assess the dose-response relationship. The book in which this method is detailed can be bought from Amazon and has often been cited in academic papers. Although it has lots of supposedly useful information for heart rate monitor novices, there is very little in terms of scientific integrity and no reference page. Now take a second to ponder on the number of papers that have used this method as a basis for justfying the use of other methods of training load. This has been done on the basis that heart rate is valid measure of intensity, but where intensity is only one term  in the equation for training load (the others being time and a weighting factor) how can the validity of training load be assumed just because heart rate is a valid indicator of intensity only!

On the other hand there is evidence to support the use generic high intensity thresholds. Castagna et al (2011) showed a dose-response relationship between the time spent above 90% and changes in fitness. Although useful such approaches used in isolation risk ignoring the training load accrued from below the thresholds and the remaining intensity continuum.

Do you use zones? What do you think? Useful? Let us know your thoughts in the training zones forum.


CASTAGNA, C., IMPELLIZZERI, F. M., CHAOUACHI, A., BORDON, C. & MANZI, V. 2011. Effect of training intensity distribution on aerobic fitness variables in elite soccer players: a case study. J Strength Cond Res, 25, 66-71.

EDWARDS, S. 1993. The heart rate monitor book, New York, Polar Electro Oy.