The basic TRIMP method
First proposed by Bannister et al in 1975, this method is a very simple way of calculating what is termed TRaining IMPulse (TRIMP). TRIMP is defined as training volume x training intensity and is specific to endurance training as it uses heart rates or heart rate zones. Initially the researchers proposed simple methods of calculating the TRIMP of a session, such as the following:
- TRIMP = training time (minutes) x average heart rate (bpm). For example, 30 minutes at 145 bpm. TRIMP = 30 x 145 = 4350.
This method, involving simple maths, makes a great deal of sense in terms of calculating a ‘dose’ of aerobic training, and I would recommend it to the average adult exerciser. For adults looking to improve basic cardiovascular fitness by means of simple training sessions, such as continuous pedalling on an indoor bike, or an aerobics class, this calculation gives them a great monitoring tool to analyse their progress and adherence to training.
A week’s training schedule could be tabulated and calculated in Excel, as shown in table 1 below. Weekly TRIMP totals could be used as targets for general CV fitness goals or to encourage increased activity.
Table 1: a week’s training using the TRIMP method Session Time HR TRIMP Monday X-trainer 25 mins 130 3,250 Wednesday bike 40 mins 120 4,800 Saturday BodyPump class 50 mins 140 7,000 Total 15,050 The disadvantage of this system is that it does not distinguish between different levels of training, which would be a problem for a more advanced exerciser or
elite athlete. For example, 30 minutes at 145 bpm gives a TRIMP score of approximately 4,500, as does 25 minutes at 180 bpm, although clearly these are very different levels of training. Assuming a max heart rate (HR) of 185 bpm, this means that one session takes place at 78% of max HR and the other at 97%. The latter will be very demanding, involving high
lactate levels and a greater training load than the former.
TRIMP training zone method
To overcome this limitation, subsequent researchers refined the basic TRIMP concept, using heart rate zones to weight intensity in the calculation
(2). Foster et al split intensity into five zones, as follows
(3):
- 50-60% max HR
- 60-70%
- 70-80%
- 80-90%
- 90-100%
The zone number is used to quantify training intensity; TRIMP is calculated as the cumulative total of time spent in each training zone.
To express the a similar example to that above in these terms:
- 30 minutes at 140 bpm. Max HR = 185 bpm. %max HR = 140/185 x 100 = 76%. Therefore, training intensity = 3. TRIMP = training volume (time) x training intensity (HR zone). 30 x 3 = 90.
- 25 minutes at 180 bpm. Max HR = 185 bpm. %max HR = 97%. Training intensity = 5. TRIMP = 25 x 5 = 125.
As you can see, this method finds that 25 minutes of working at a very high heart rate results in a higher training load score than 30 minutes at a steady state heart rate.
The zone TRIMP calculation method can distinguish between training levels while remaining mathematically simple and I would recommend its use to serious exercisers and elite endurance athletes, especially as it can be used for quantifying interval sessions with variable heart rates. To calculate the TRIMP for the interval session, simply add up the time spent in each zone, as in the following example:
- 5 x 3 minutes at 95% max HR with 3 minutes easy jog at 70% max HR recovery. TRIMP = 15 x 5 + 15 x 2 = 105.
visto che mi alleno col cardio...
