StriveKit’s performance management tools utilize proven, peer-reviewed sports science methodologies to help you quantify your training, balance your workload, and peak at the right time.
Our charts are built upon the foundational impulse-response model originally conceptualized by Dr. Eric Banister in 1975, which was later adapted for power, pace, and swimming data by modern sports scientists like Dr. Andrew Coggan.
1. Fitness / Chronic Training Load (CTL)
- What it means: A rolling exponential moving average of your daily Training Stress Score (TSS) over the last 42 days.
- The Science: CTL represents long-term training load. It quantifies the physiological adaptations your body has built up over weeks of consistent training.
- How to use it: Look for a gradual, steady upward trend. Raising your CTL too quickly can signal overtraining, while a steep decline shows a loss of base aerobic fitness.
2. Fatigue / Acute Training Load (ATL)
- What it means: A rolling exponential moving average of your daily TSS over the last 7 days.
- The Science: ATL tracks short-term training stress. Because it weights your most recent workouts heavily, it models the immediate fatigue and metabolic damage carried by your body.
- How to use it: This number spikes quickly after heavy training blocks or long sessions. It serves as an objective indicator of how tired your body is right now.
3. Form / Training Stress Balance (TSB)
- What it means: Calculated daily as Fitness minus Fatigue (CTL – ATL).
- The Science: Form models your overall readiness to perform. It balances the positive adaptations of fitness against the negative impacts of immediate fatigue.
- The Training Zones:
- +5 to +20 (Fresh / Optimal): Fatigue has cleared, leaving your built-up fitness intact. Ideal for race days or key performance tests.
- -10 to +5 (Neutral / Maintenance): A balanced state typically seen during transitional training weeks.
- -10 to -30 (Productively Tired): The optimal zone for building fitness. Your body is under stress, triggering adaptation.
- Below -30 (Danger Zone): High risk of overtraining, chronic fatigue, or injury.
Industry Standard: TSS Calculation
Training Stress Score (TSS) gives every workout a single numerical value representing its total physiological cost by factoring in both duration and intensity. To make this accurate across multiple sports, StriveKit calculates stress relative to your personal performance thresholds:
- Cycling: Calculated using Normalized Power (NP) relative to your Functional Threshold Power (FTP).
- Running: Calculated using Normalized Graded Pace (NGP)—which adjusts for elevation changes—relative to your Threshold Running Pace.
- Swimming: Calculated using your Swim Speed relative to your Critical Swim Speed (CSS).
Scientific References
- Banister, E. W., Calvert, T. W., Savage, M. V., & Bach, T. (1975). A systems model of training for athletic performance.
- Allen, H., & Coggan, A. (2010). Training and racing with a power meter. (The implementation of the modern CTL, ATL, TSB, and TSS algorithm structure used across endurance platforms).
- Gabbett, T. J. (2016). The training-injury prevention paradox: should athletes be training smarter and harder? British Journal of Sports Medicine, 50(5), 273-281. (Supporting data regarding the management of acute-to-chronic workloads to mitigate injury risks).