Understanding TRIMP: A Guide to Heart Rate Training Impulse
- Jo Clubb
- Mar 5
- 3 min read
This post explains how heart rate training impulse (TRIMP) is calculated and why it matters in athlete monitoring.
What is TRIMP?
TRIMP, or Training Impulse, is a method designed to measure internal load, pioneered by Eric Banister in the 1970s. At its core, TRIMP combines heart rate intensity and duration to provide a nuanced understanding of an athlete's internal load during exercise.
Why Internal Load Matters
While much attention has shifted towards external load—metrics captured by tracking technology such as distance, acceleration, and speed—measuring internal load provides a glimpse into the body's physiological cost to these external demands. Internal load is crucial for determining training outcomes and adaptations, as noted by Franco Impellizzeri and colleagues in this 2019 IJSPP review: Internal and External Load 15 Years On. It is the internal load that drives the adaptations to training. Understanding this response helps coaches fine-tune training programs, ensuring athletes achieve desired physiological adaptations.
Calculating TRIMP
Banister's original model used average heart rate data to calculate TRIMP. However, using the average HR might not accurately represent the fluctuation in HR that occurs during intermittent exercise. Firstbeat Sports therefore use beat-to-beat heart rate data to better capture variations in intensity, which is especially important in intermittent team sports.
Using Firstbeat Sports' methodology, TRIMP is accumulated through an exponential relationship with exercise intensity. This means higher heart rates receive greater weighting, allowing for a comprehensive TRIMP score for a session. Additionally, calculating TRIMP per minute helps compare different sessions or drills, taking into consideration both the intensity and duration of activities.
Collecting accurate TRIMP data begins with determining each athlete’s maximum heart rate. TRIMP’s value also hinges on precise time period selections during data collection—whether analysing full sessions or specific drills.
Implications for Training
Understanding TRIMP helps establish benchmarks for easy, moderate, or hard training sessions. While Firstbeat Sports have provided benchmarks (below), it's also essential to comprehend these metrics in your own sport's context to understand session demands.
In practice, TRIMP data can be used to strategise athlete training load and recovery needs. Measuring internal load provides insights into an athlete's physiological journey, allowing for tailored training plans based on individual trends and norms. In the video on the Global Performance Insights YouTube channel, Minnesota Wild's Matt Harder exemplifies this by using TRIMP data to objectively communicate with coaches and players in ice hockey.
An innovative application of TRIMP involves integrating submaximal tests with heart rate monitoring. By fixing external load and observing internal response, coaches can non-intrusively track fitness progression. We've previously talked about such submaximal tests within the invisible monitoring approach to assessing the fitness-fatigue relationship.
Final Thoughts
Heart Rate Training Impulse (TRIMP) is a validated means to assess internal load and understand the physiological cost of training sessions. The training process is about more than just the distance covered and speeds hit. When trying to manage the balance between stimulus and recovery, such heart rate data provides insight into the physiological demand of training, which can assist with our training planning and adjustments. Acknowledging the insights that heart rate TRIMP provides allows for a more comprehensive approach to sports science and athlete development.
FAQs on Heart Rate TRIMP
Q: What is the primary function of TRIMP?
A: TRIMP serves to measure the internal load on an athlete - the physiological cost associated with the work completed - helping guide training intensity and load management decisions.
Q: How is TRIMP calculated?
A: TRIMP is calculated using heart rate and duration, with higher heart rates receiving greater weighting to reflect exercise intensity.
Q: Why is measuring internal load important?
A: It reveals the body's psychophysiological responses, ensuring training programs effectively target desired adaptations. By analysing TRIMP trends, coaches can customise training loads to enhance performance while avoiding overtraining.
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This article is supported by Firstbeat Sports. Learn more with their free training load guide! Download here â–º https://content.firstbeat.com/firstbeat-guide-to-understanding-the-athlete-training-load
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