Training load is a quantified measure of the overall stress placed on the body during a workout session. It combines both the intensity and duration of exercise into a single number that coaches and athletes use to monitor fitness, fatigue, and recovery. By tracking training load over time, you can ensure progressive overload while avoiding overtraining and injury.

Multiple methods exist to quantify training load, each with different data requirements. The simplest is session RPE (sRPE), which only requires a subjective effort rating and session duration. More advanced methods like Training Stress Score (TSS) require a power meter, while TRIMP uses heart rate data to estimate physiological stress.

sRPE (Session RPE) is the most accessible method, developed by Dr. Carl Foster. After each session, you rate the overall difficulty on a 1-10 scale and multiply by duration. It is valid across all sports and requires no equipment, making it ideal for team sports and multi-sport athletes.

TSS (Training Stress Score), created by Dr. Andrew Coggan, is the gold standard for cycling. It uses normalized power from a power meter relative to your Functional Threshold Power (FTP). TRIMP (Training Impulse), developed by Eric Banister, uses heart rate reserve to estimate internal physiological stress and works well for any HR-monitored activity.

The acute-to-chronic workload ratio (ACWR) compares your recent training load (7-day) to your chronic load (28-day rolling average). An ACWR between 0.8 and 1.3 is considered the sweet spot for performance gains while minimizing injury risk. Spikes above 1.5 significantly increase injury probability.

Periodization uses training load to structure training cycles. Build weeks gradually increase load by 10-15% per week, followed by recovery weeks at 50-60% of peak load. This pattern allows systematic fitness development while providing adequate recovery for adaptation.

Training load metrics are estimates and should be interpreted alongside subjective measures like sleep quality, mood, muscle soreness, and appetite. No single number captures the full picture of training stress. Individual responses to the same training load vary significantly based on fitness level, genetics, nutrition, and life stress.

Different methods are not directly comparable. A TSS of 100 does not equal a TRIMP of 100 or an sRPE load of 100. Choose one primary method and use it consistently for meaningful longitudinal tracking. Combining methods for different workout types (e.g., TSS for cycling, sRPE for strength) is common in multisport training.