How HIIT Evaluator Turns Feedback into Training Adjustments

The principle introduced in Make Small Adjustments is that future training decisions should respond to feedback rather than to the assumption that every workout must be harder than the last. HIIT Evaluator supports this process by combining information about long-term progress with information about the quality of individual training sessions.

PCS and SQS work together as this feedback system. PCS provides a long-term perspective. By measuring changes relative to the Day 1 baseline, it helps determine whether training capacity is improving, plateauing, or declining over time. Long-term trends, however, change slowly and cannot by themselves explain the quality of the most recent workout. For that, HIIT Evaluator also uses SQS.

Unlike PCS, which focuses on long-term development, SQS focuses on the quality of a single training session. It is not intended to measure progress. Instead, it evaluates whether a workout achieved its intended training quality. Effective training is influenced not only by intensity, but also by workout rhythm, recovery quality, and whether the overall heart-rate pattern exhibits the characteristics of a well-executed HIIT session.

SQS is therefore not based on a single measurement. It is built from several dimensions. Peak Score, or PS, measures training intensity. It uses the age-adjusted theoretical maximum heart rate as a reference and maps actual training intensity into a standardized scoring framework. Peak Width Score, or PWS, measures workout cycle structure and evaluates whether the training rhythm aligns with the intended HIIT protocol.

In addition to intensity and cycle structure, waveform quality is also evaluated. PS Ratio is primarily designed to identify low-quality heart-rate patterns and penalize workouts that deviate significantly from the intended training model. Examples include insufficient peak intensity, inadequate recovery, or distorted heart-rate curves. PWS Ratio uses a segmented scoring approach to encourage training within an effective range rather than optimizing a single measurement in isolation.

When PCS and SQS are combined, training adjustments can be made with greater confidence. PCS provides information about long-term direction, while SQS reflects the quality of the current session. Together, they offer a more complete picture than either metric alone.

When PCS continues to rise and SQS remains healthy, the current training strategy is generally working as intended and may require little or no adjustment. Increasing the workload simply because another session has been completed could interfere with a process that is already producing progress.

When PCS begins to plateau while SQS remains consistently strong, the body may have adapted to the current training load. In that situation, a modest increase in training stimulus may be appropriate. The change should remain small enough that its effect can be observed without disrupting the comparability of future sessions.

When PCS and SQS both begin to decline, the issue is often not insufficient effort. Accumulated fatigue, inadequate recovery, or deteriorating training quality may be more likely explanations. Increasing intensity in response could make the problem worse, while additional recovery or a temporary reduction in workload may be the more appropriate adjustment.

These examples show why a single score cannot determine the next workout in isolation. The same PCS movement can have different meanings depending on the quality of recent sessions, and one poor workout should not automatically trigger a change in protocol. The decision becomes more reliable when multiple observations form a consistent pattern.

The purpose of the system is not to produce constant changes. It is to distinguish between situations in which the current protocol should be maintained, situations in which a small increase may be justified, and situations in which recovery should take priority. In this way, training feedback becomes a practical input to the next training decision.

Repeating this process over time creates the foundation for Achieve Sustainable Progress.