Essential terminology for data-driven cycling and running training
8 terms
A measure of your current 'form' — the balance between fitness and fatigue.
TSB is calculated as CTL minus ATL. A positive TSB means you're fresh and ready to perform; a negative TSB means accumulated fatigue. Most athletes perform best with TSB between -10 and +15. Too negative risks overtraining; too positive means you're detrained.
Your long-term training load, representing accumulated fitness over approximately 42 days.
CTL is an exponentially weighted average of your daily TSS. It rises slowly with consistent training and decays when you rest. Higher CTL means greater endurance capacity. Building CTL safely requires gradual progression — typically no more than 5-7 points per week.
Your short-term training load, representing recent fatigue over approximately 7 days.
ATL responds quickly to training — a hard week spikes it, rest drops it. High ATL indicates accumulated fatigue that needs recovery. During a taper, you deliberately reduce ATL while maintaining CTL to arrive at race day fresh but fit.
A single number quantifying the training load of a workout based on duration and intensity.
TSS normalizes different workout types to a common scale. A 1-hour ride at FTP equals 100 TSS. An easy 2-hour ride might be 80 TSS; an intense 90-minute race could be 150+ TSS. TSS feeds into CTL and ATL calculations to track your training load over time.
The ratio of your recent training load (7-day) to your longer-term load (28-day), used to flag injury risk.
ACWR compares how hard you have trained recently versus what your body is used to. A ratio between 0.8 and 1.3 is considered the 'sweet spot' — enough stimulus without excessive risk. Above 1.5, injury risk increases significantly because you are doing far more than your body has adapted to. Below 0.8, you may be undertraining and losing fitness. IntervalCoach tracks ACWR automatically and triggers load adjustments when spikes are detected.
The highest power output you can sustain for approximately one hour — your aerobic ceiling.
FTP is the foundation of power-based training. All training zones are calculated as percentages of FTP. It can be measured via a 20-minute test (multiply by 0.95) or a ramp test. FTP improves with consistent training and typically ranges from 150-450 watts depending on fitness level.
An algorithmically calculated FTP based on your recent power data and power curve.
eFTP analyzes your best power outputs across different durations to estimate your threshold without a formal test. It updates automatically as you ride, making it useful for tracking fitness changes between tests. Some athletes prefer eFTP for its convenience; others use manual FTP tests for accuracy.
Your sustainable swimming pace — the swim equivalent of FTP, expressed as a pace per 100m.
CSS estimates the fastest pace you can hold for a long continuous swim. It is typically calculated from a pair of time trials (e.g., 400m and 200m). Training zones for swimming are set as percentages of CSS pace. Intervals below CSS build endurance; intervals at or above CSS develop threshold and VO2max capacity. IntervalCoach uses your CSS to generate distance-based swim workouts with accurate pace targets.
7 terms
The systematic planning of training into distinct phases with specific goals.
Periodization divides your training year into base, build, peak, and recovery phases. Base phase builds aerobic foundation with high volume and low intensity. Build phase adds intensity. Peak phase sharpens fitness for key events. This structured approach prevents plateaus and optimizes performance timing.
A planned reduction in training volume before a key event to maximize performance.
During a taper, you reduce volume by 40-60% while maintaining some intensity. This allows fatigue (ATL) to drop while preserving fitness (CTL), resulting in positive TSB. Typical tapers last 1-3 weeks depending on event importance. Done correctly, a taper can improve performance by 2-6%.
The foundational phase of training focused on aerobic development through steady, moderate efforts.
Base building develops your aerobic engine through consistent Zone 2 training. This phase typically lasts 8-12 weeks and builds the foundation for harder training later. Signs of good base fitness include low heart rate at moderate power and quick recovery between efforts.
High-intensity intervals performed at 106-120% of FTP to maximize oxygen uptake capacity.
VO2max work consists of 3-8 minute intervals at very high intensity with equal or longer recovery. These sessions develop your maximum aerobic power and are crucial during the build phase. They're demanding — most athletes limit VO2max sessions to 1-2 per week with adequate recovery.
Training performed at or near FTP to improve sustainable power output.
Threshold intervals typically last 8-20 minutes at 95-105% FTP. This intensity teaches your body to clear lactate efficiently and raises your sustainable power ceiling. Sweet spot training (88-94% FTP) offers similar benefits with less fatigue, making it popular for time-crunched athletes.
Training at 88-94% of FTP — hard enough to build fitness, sustainable enough to accumulate volume.
Sweet spot sits between tempo and threshold zones. It provides excellent training stimulus with manageable fatigue, offering the best 'bang for your buck' in limited training time. Typical sweet spot workouts include 2-3 intervals of 15-30 minutes with short recovery.
A very easy ride designed to promote active recovery without adding training stress.
Recovery rides should feel almost too easy — typically under 55% FTP. The goal is increased blood flow to aid recovery, not fitness gains. Heart rate should stay low, and you should finish feeling better than when you started. If you're too tired for a recovery ride, rest is better.
5 terms
The variation in time between consecutive heartbeats — a key indicator of recovery and readiness.
Higher HRV generally indicates good recovery and parasympathetic (rest) nervous system dominance. Lower HRV can signal fatigue, stress, or illness. Tracking HRV trends over time helps identify when you're ready to train hard versus when you need more recovery. Morning measurements are most reliable.
Your heart rate when completely at rest — a key indicator of cardiovascular fitness and recovery.
Lower RHR generally indicates better cardiovascular fitness. An elevated RHR compared to your baseline can signal fatigue, stress, illness, or overtraining. Athletes typically have RHR between 40-60 bpm. Track your trend over time rather than individual readings — a sustained increase of 5+ bpm above baseline warrants attention.
A measure of cardiovascular load accumulated throughout the day, typically on a 0-21 scale.
Strain quantifies how hard your cardiovascular system worked during activities and daily life. Higher strain means more stress on the body and greater recovery needs. Wearables like Whoop calculate strain based on heart rate and time in elevated zones. Matching strain to recovery capacity helps prevent overtraining.
A composite metric combining sleep, HRV, and other factors to indicate training readiness.
Recovery scores (like those from Whoop or Garmin) synthesize multiple data points into a single readiness indicator. A high score suggests you're ready for intensity; a low score recommends easier training or rest. While useful, these scores should complement — not replace — how you actually feel.
A measure of how restorative your sleep was, based on duration, stages, and disturbances.
Quality sleep is when adaptation happens. Deep sleep repairs muscles; REM sleep consolidates motor learning. Athletes need 7-9 hours, with sufficient deep and REM stages. Poor sleep quality — even with adequate duration — impairs recovery and performance. Consistency in sleep timing matters as much as duration.
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