Training Load Calculator

Training load monitoring is a cornerstone of modern sport science. The session RPE method, developed by Carl Foster and colleagues, offers a simple yet validated approach to quantifying internal training load. Rather than relying on expensive heart rate monitors or lactate testing, athletes rate their overall perceived exertion for each session on a 6–20 or 1–10 scale immediately after completing it. This subjective intensity measure is then multiplied by session duration to produce an arbitrary unit (AU) load value that correlates strongly with objective physiological markers such as heart rate training impulse (TRIMP) and blood lactate accumulation.

The core formula is straightforward: Session Load = RPE × Duration (minutes). From individual session loads, two rolling averages are derived. The Acute Training Load (ATL) is the 7-day rolling average of daily loads, reflecting short-term accumulated fatigue. The Chronic Training Load (CTL) is the 28-day rolling average, representing the athlete's long-term fitness base. The ratio of ATL to CTL yields the ACWR. Research by Gabbett (2016) established that an ACWR between 0.8 and 1.3 is associated with low injury risk — the so-called 'sweet spot.' Values above 1.5 ('danger zone') significantly increase soft tissue injury probability, while values below 0.8 may indicate undertraining or detraining. The Fitness-Fatigue Balance (ATL minus CTL) gives a directional indicator: positive values suggest accumulated fatigue exceeding the fitness base, while negative values suggest a recovery or taper phase.

This calculator is used by strength and conditioning coaches in team sports, endurance athletes managing periodized training plans, rehabilitation clinicians returning athletes to sport, and recreational athletes seeking data-driven self-monitoring. It is particularly valuable during pre-season intensification, competition phases, and injury rehabilitation progressions where workload management is critical to performance and longevity.

The session RPE method relies on subjective self-reporting, which can vary with athlete motivation, mood, and familiarity with the scale. Novice athletes often rate RPE inconsistently, reducing accuracy in the early weeks of monitoring. The 7-day and 28-day windows used for ATL and CTL are population-level approximations; some sport scientists advocate for exponentially weighted moving averages (EWMA) that weight recent sessions more heavily, potentially offering a more responsive and biologically accurate model. The ACWR framework has also faced methodological criticism — notably the 'mathematical coupling' problem identified by Impellizzeri et al. (2019), where ATL and CTL share overlapping data, artificially inflating their correlation with injury. ACWR should therefore be interpreted alongside other metrics such as wellness scores, HRV, and perceived recovery. Furthermore, this calculator assumes all sessions contribute equally to load — it does not distinguish between resistance training, speed work, and aerobic conditioning, which have different recovery demands and injury mechanisms. Athletes with highly varied multi-modal training should consider sport-specific load tracking approaches.