What is Training Load?

Better Workouts uses TRIMP or TRaining IMPulse to calculate training load or effort.

The app specifically calculates a variation called TRIMP exp or Exponential Heart Rate Scaling.

The metric uses Heart Rate Reserve and an exponential scaling factor to account for the fact that higher intensity training as a disproportionately high training impact. The formula for calculating TRIMP exp is:

TRIMP exp = sum(D x HRr x 0.64ey)


  • D is the duration in minutes at a particular Heart Rate
  • HRr is the Heart Rate as a fraction of Heart Rate Reserve
  • y is the HRr multiplied by 1.92 for men and 1.67 for women.
These constants were developed based on the experimentally observed relationship between heart rate and lactate level. For men this will give a TRIMP value of 0 to 4.37 per minute and for women 0 to 3.4.


A worked example would be a male athlete with a HRmax = 200 and HRrest = 40 training for 30 min. at 130 BPM. The TRIMP exp is therefore:

TRIMP exp = 30 x (130-40) / (200-40) x 0.64e ^(1.92 x (130-40) / (200-40))

Which simplifies to:

TRIMP exp = 30 x 0.56 x 0.64e ^(1.92 x 0.56)

Which is a value of 32. This is obviously a simplified example as in reality an athlete heart rate will vary over time.

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