TRIMP stands for TRaining IMPulse, developed by Dr. Eric Banister. It quantifies the physiological stress of a training session by combining duration with heart rate intensity. Higher TRIMP means more training stress. It's widely used in endurance sports for load monitoring.

Why does TRIMP differ between males and females?

The exponential weighting factor (b) differs because blood lactate response to exercise intensity differs between sexes. Males use b=1.92 and females use b=1.67, reflecting the different physiological responses to higher-intensity exercise.

What is a good TRIMP score for a session?

It depends on the session purpose. Recovery/easy sessions: 30-80 TRIMP. Moderate endurance: 80-150. Tempo/threshold: 150-250. High-intensity intervals: 200-350+. Long endurance (2+ hours easy): 200-400. Context matters more than the absolute number.

What is the ACWR (Acute:Chronic Workload Ratio)?

ACWR compares your recent load (last 7 days) to your average load (last 28 days). An ACWR of 1.0 means your recent training matches your average. Below 0.8 means you're undertraining; above 1.3-1.5 means you're spiking load dangerously. The sweet spot is 0.8-1.3.

How is TRIMP different from Training Stress Score (TSS)?

TRIMP uses heart rate; TSS (from TrainingPeaks) uses power data. Both quantify session stress but from different physiological markers. TSS is preferred in cycling (where power meters are common); TRIMP works for any sport where you can measure heart rate.

Can I use session RPE instead of heart rate?

Yes. Session RPE Load = Duration × RPE (1-10 scale) is a validated alternative. It correlates well with heart rate-based TRIMP (r ≈ 0.75-0.90) and is simpler. Rate the overall session difficulty on a 1-10 scale about 30 minutes after finishing.

Training Load (TRIMP) Calculator

Calculate your TRIMP training load using Banister's model. Track session intensity with heart rate data and monitor acute vs chronic training load ratio.

Session Data

Duration

min

Sex

Avg Heart Rate

bpm

Resting HR

bpm

Max HR

bpm

Session RPE (1-10)

Session TRIMP

133.8

Moderate

TRIMP Score

133.8

Banister method

ΔHR Ratio

0.731

b = 1.92

Session RPE Load

315

45 min × RPE

Intensity

73% HRR

Intensity Classification

RecoveryEasyModerateHardVery Hard

Acute:Chronic Workload Ratio (ACWR)

Enter your total weekly TRIMP (or RPE load) for the last 4 weeks:

Week 1 (oldest)

Week 2

Week 3

Week 4 (current)

ACWR

1.07

Optimal

Acute: 520.00 | Chronic: 488.00

<0.8 Undertraining0.8–1.3 Optimal1.3–1.5 Caution>1.5 Danger

Planning notes, formulas, and examples

About the Training Load (TRIMP) Calculator

Training load quantification is essential for preventing overtraining and optimizing performance. TRIMP (TRaining IMPulse), developed by Dr. Eric Banister in 1991, is one of the most widely validated methods for measuring the physiological stress of a workout using heart rate data.

This calculator computes your TRIMP score for a session based on duration, average heart rate, resting heart rate, and max heart rate. It also provides session RPE-based training load as an alternative when heart rate data isn't available.

By tracking TRIMP over time, you can monitor your acute (7-day) and chronic (28-day) training loads and keep the ACWR (Acute:Chronic Workload Ratio) in the optimal zone to maximize fitness while minimizing injury risk.

When This Page Helps

Training by feel alone can make it harder to compare one session with the next. TRIMP gives you a repeatable load number that combines duration and intensity, which is useful when you want to review weekly totals or compare heart-rate-based sessions.

How to Use the Inputs

Enter your resting and max heart rate.
Enter the session duration in minutes.
Enter your average heart rate during the session.
Select your sex (the TRIMP weighting factor differs).
View your TRIMP score and intensity classification.
Optionally enter recent weekly loads to see your ACWR ratio.

Formula used

Banister TRIMP = Duration(min) × ΔHRratio × e^(b × ΔHRratio)

Where:
• ΔHRratio = (HRavg − HRrest) / (HRmax − HRrest)
• b = 1.92 for males, 1.67 for females

Alternative: Session RPE Load = Duration(min) × RPE (1-10 scale)

ACWR = Acute Load (7-day) / Chronic Load (28-day average)

Example Calculation

Result: TRIMP = 134.2 (Moderate-High)

With a 45-minute session at 155 bpm average HR, the ΔHR ratio is (155−60)/(190−60) = 0.731. Using the male weighting factor (b=1.92), TRIMP = 45 × 0.731 × e^(1.92×0.731) = 45 × 0.731 × 4.08 ≈ 134.2. This represents a moderate-to-hard session.

Tips & Best Practices

TRIMP scores of 50-100 represent easy sessions; 100-200 moderate; 200-300 hard; 300+ very hard.
Keep your ACWR between 0.8 and 1.3 for optimal performance and lowest injury risk.
An ACWR above 1.5 significantly increases injury risk — you're doing too much too fast.
Track TRIMP weekly totals, not just individual sessions, for meaningful load management.
Session RPE method is a valid alternative when you don't have heart rate data.
Combine TRIMP with subjective wellness scores (sleep, mood, fatigue) for comprehensive monitoring.

The Fitness-Fatigue Model

Banister's impulse-response model proposes that every training session produces both fitness and fatigue. Fitness accumulates slowly and dissipates slowly; fatigue accumulates quickly and dissipates quickly. Performance = Fitness − Fatigue. TRIMP quantifies the input to this model, allowing coaches to predict when an athlete will be in peak form.

Monitoring the ACWR

The Acute:Chronic Workload Ratio is one common way to compare recent load with longer-term load. Research across football, rugby, cricket, and athletics often uses ACWR bands such as 0.8 to 1.3 as a practical reference range, while large spikes above that range are generally treated as a warning sign rather than a stand-alone injury predictor.

Practical Application

Track your TRIMP for every session in a spreadsheet or training app. Sum weekly totals and calculate rolling 4-week averages. When planning training blocks, aim to increase weekly TRIMP by no more than 10-15% per week. Include recovery weeks where you reduce TRIMP by 30-50% every 3-4 weeks.

Sources & Methodology

Last updated: March 28, 2026

Methodology

This calculator estimates training load from heart-rate intensity and duration using the Banister-style TRIMP approach, with session RPE as a fallback when heart rate data is unavailable. The acute and chronic load readout is a rough workload check rather than a fixed injury-risk threshold. The goal is to support planning and recovery tracking, not to make hard readiness claims from a single session.

Sources

Banister impulse-response / TRIMP model (Sports science literature) — Foundational framework for training-impulse load modeling.
Session-RPE method for training load monitoring (Sports medicine literature) — Validated alternative load estimate when heart rate data is not available.
Acute:Chronic Workload Ratio: Conceptual issues and fundamental pitfalls (Sports medicine literature) — Used to frame ACWR as a rough monitoring heuristic rather than a hard injury predictor.

Frequently Asked Questions

TRIMP stands for TRaining IMPulse, developed by Dr. Eric Banister. It quantifies the physiological stress of a training session by combining duration with heart rate intensity. Higher TRIMP means more training stress. It's widely used in endurance sports for load monitoring.