How can training load be measured using external and internal metrics?

• A. Not measurable
• B. External: distance, repetitions, velocity; Internal: heart rate, perceived exertion, hormonal markers; tools include GPS and HR monitors
• C. External: distance only
• D. Internal: only heart rate

Answer: (B)

Training load is best understood as a combination of what was done (external work) and how the body responded (internal stress). External metrics quantify the actual work performed, such as distance, repetitions, and velocity, and are often captured with tools like GPS devices, accelerometers, and sprint timing. Internal metrics describe the body's physiological and perceptual response to that work—heart rate, perceived exertion, and, in some cases, hormonal markers—measured with heart-rate monitors, RPE scales, or laboratory tests.

Using both sides gives a fuller picture. Two workouts might cover the same distance, but one induces a much higher cardiovascular and perceptual effort, indicating a greater internal load. Conversely, a session with high external workload but lower internal stress could reflect good fitness or efficient adaptation. By combining external and internal data, you can quantify training load more accurately, for example through measures like sRPE (session rating of perceived exertion) times duration or HR-based TRIMP calculations.

This approach is why the best answer lists both external metrics (distance, repetitions, velocity) and internal metrics (heart rate, perceived exertion, hormonal markers) and notes the tools (GPS and HR monitors).