Why is TRIMP Useful for Endurance Athletes?

1. It’s Objective and Data-Driven
Unlike subjective methods like RPE, which rely on personal perception, TRIMP is based on hard data—heart rate and workout duration. This objectivity allows athletes to see a consistent, accurate measure of how much work they’re doing. Dr. Bannister’s goal was to create a metric that athletes could depend on regardless of how they “felt” about a workout, giving them a clear measure of physical stress.

2. It Accurately Reflects Training Intensity
TRIMP uses different weighting factors for heart rate zones, which means it captures the extra strain that comes with high-intensity exercise. A 30-minute high-intensity interval workout and a 30-minute easy jog may both last the same amount of time, but they impose very different levels of stress on the body. TRIMP adjusts for this by increasing the weight of higher heart rate zones, making it especially valuable for endurance athletes whose workouts vary in intensity.

3. It Helps Athletes Track Progress Over Time
Because TRIMP scores are calculated the same way each time, they offer a consistent way to track your training load over weeks or months. By observing your cumulative TRIMP scores, you can spot patterns, prevent overtraining, and make informed decisions on when to push harder or when to scale back.

How to Calculate TRIMP Using Weighting Factors

Calculating TRIMP involves three main components: duration, heart rate, and intensity weighting. Here’s how to calculate it step-by-step.

1. Measure Workout Duration:
Begin by noting how long your workout lasted in minutes.

2. Calculate Your Average Heart Rate as a Percentage of Your Max Heart Rate:
Dr. Bannister’s model uses the percentage of maximum heart rate, as heart rate gives insight into the intensity of effort.

3. Apply Weighting Factors Based on Heart Rate Zones:
TRIMP uses exponential weighting to reflect the additional strain of higher-intensity exercise. Dr. Bannister’s original research assigned weightings to different heart rate zones, recognizing that intensity impacts training load more significantly at higher levels.

Below is a table of common TRIMP weighting factors by heart rate zone:

Heart Rate Zone Description Weighting Factor

• Zone 1 Light (60-70% max HR) 1.0
• Zone 2 Moderate (70-80% max HR) 1.5
• Zone 3 Hard (80-90% max HR) 2.0
• Zone 4 Very Hard (90-95% max HR) 3.0
• Zone 5 Max Effort (95-100% max HR) 4.0

TRIMP Calculation Formula:

Once you know the duration and weighting factor for your heart rate zone, you can calculate your TRIMP score as follows:

Example Calculation of TRIMP

Let’s say you complete a 45-minute workout where your average heart rate is 85% of your maximum, placing you in Zone 3.

• Duration: 45 minutes
• Heart Rate Zone Weighting: 2.0 (Zone 3)

Using the formula:

In this case, your TRIMP score of 90 reflects the combination of time and intensity, offering a clearer sense of how much stress your body experienced during the workout.

Practical Applications of TRIMP in Training

1. Set Weekly TRIMP Targets
Dr. Bannister’s TRIMP can be especially useful for setting and tracking weekly training goals. By aiming for a specific weekly TRIMP score, you can structure your training cycles effectively:

• Base Period: Focus on gradually building up weekly TRIMP scores with mostly low to moderate intensity.
• Peak Period: Target higher weekly TRIMP scores as you increase intensity leading up to a race or event.
• Tapering: Reduce weekly TRIMP in the lead-up to an event, allowing your body to recover.

2. Monitor Cumulative Training Load

Tracking TRIMP over several weeks gives you insight into cumulative training load. By adding up your weekly TRIMP scores, you can see if your training load is increasing too rapidly, which could lead to overtraining. Ideally, aim for gradual, controlled increases to ensure long-term fitness gains.

3. Adjusting Workouts for Optimal Load

TRIMP’s objective nature makes it a helpful tool for adjusting workouts based on recent scores. For example, if you had a high-TRIMP workout yesterday, you might plan a lower-TRIMP session today to balance load and recovery. TRIMP gives you a clear metric to base these decisions on, allowing you to plan both hard days and easy days effectively.

Limitations of TRIMP

While Dr. Bannister’s TRIMP is widely respected, it has a few limitations:

• Requires a Heart Rate Monitor: Since TRIMP depends on heart rate, you’ll need a reliable heart rate monitor for accurate calculations.
• Doesn’t Reflect Cumulative Fatigue: TRIMP scores measure each workout individually, so they may not fully capture the residual fatigue from previous training sessions. See Training Load Ratio Blog
• Less Suitable for Short, High-Intensity Workouts: TRIMP relies on average heart rate, so it may underestimate the stress of short, very high-intensity efforts where heart rate doesn’t have time to rise fully.

Using TRIMP with Other Metrics

Many endurance athletes find TRIMP to be most effective when combined with other metrics. Here are a few ways you can pair TRIMP with additional measures:

• TRIMP + RPE: Combining TRIMP’s objective score with the subjective Rating of Perceived Exertion (RPE) gives you insight into both how hard the workout was physiologically and how it felt personally.
• TRIMP + Foster Score: Using the Foster Score alongside TRIMP provides both a heart rate-based measure and a time-based subjective score.
• TRIMP + Endurance Training Score (ETS): If you’re a high-volume athlete managing lots of accumulated load, combining TRIMP with the T2 Score (which accounts for different sport modalities) can give you a comprehensive view of both daily and ongoing stress.

Why Dr. Bannister’s TRIMP is Valuable for Endurance Athletes

In summary, TRIMP is a scientifically developed metric that provides an objective way to measure training load based on heart rate and duration. It’s:

• Objective and consistent, making it easy to track across different workouts.
• Useful for setting training goals, adjusting load, and tracking progress over time.
• Ideal for endurance athletes who need an accurate measure of training stress.

By incorporating TRIMP into your training, you can take a more data-driven approach to track your progress, balance effort with recovery, and reach your performance goals more effectively.

Start Tracking Your TRIMP Score

Ready to give TRIMP a try? Use a heart rate monitor in your next workout and calculate your TRIMP score. Track it over a week to see how your training load adds up, and start planning your workouts based on TRIMP to optimise performance and recovery.