Fatigue Recovery Curve Calculator
Free Fatigue recovery curve Calculator for rehabilitation recovery. Enter your stats to get performance metrics and improvement targets.
Fatigue Recovery Curve Calculator
Calculator
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Formula: Fatigue(t) = Peak × 0.5^(t/half-life)
Worked example — Full recovery ~50 hours
Formula
Fatigue(t) = Peak × 0.5^(t/half-life)
Fatigue decays exponentially. Half-life varies: light exercise ~8h, moderate ~12h, heavy/DOMS ~24-48h.
Worked Examples
Example 1: Heavy workout
Problem:80% fatigue, 12h half-life
Solution:6h: 56%, 12h: 40%, 24h: 20%, 48h: 5%
Result:Full recovery ~50 hours
Example 2: Light recovery run
Problem:30% fatigue, 8h half-life
Solution:6h: 20%, 12h: 15%, 24h: 8%
Result:Full recovery ~20 hours
Frequently Asked Questions
What affects recovery speed?
Sleep (7-9h optimal), protein intake (1.6-2.2g/kg), hydration, age, training experience, and stress levels all significantly affect recovery rate.
How is the fatigue recovery curve calculated?
Fatigue(t) = Peak × 0.5^(t / half-life). This exponential decay model mirrors real physiological recovery, where the rate of recovery slows as fatigue decreases. The half-life is the time required for fatigue to drop by exactly 50%.
What is the half-life of fatigue after exercise?
Half-life varies by intensity: light activity about 8 hours, moderate exercise about 12 hours, intense training about 24 hours, and DOMS-inducing eccentric work about 36-48 hours. Individual responses vary based on fitness level and recovery practices.
When would I use Fatigue Recovery Curve Calculator?
Use it to plan training schedules that avoid accumulated fatigue, determine readiness before competition, set rest intervals between heavy sessions, or show athletes why back-to-back intense workouts reduce performance and increase injury risk.
Why is fatigue modeled as an exponential decay rather than a straight line?
Physiological recovery processes such as glycogen resynthesis, inflammatory clearance, and neuromuscular restoration all slow as the body approaches baseline, producing exponential rather than linear decay. In practice the first few hours after a hard session clear a large share of fatigue quickly, while the last portion lingers noticeably longer, matching the common experience of feeling mostly recovered within a day but not fully back to 100 percent for two or three days.
How does this curve differ across training ages and fitness levels?
Trained athletes generally show shorter fatigue half-lives than untrained individuals for a comparable relative workload, thanks to better mitochondrial density, buffering capacity, and repair efficiency built up over years of training. Two athletes performing the same absolute heavy session may start at a similar peak fatigue percentage, but the trained athlete typically reaches a safe training-readiness threshold sooner.
What is the difference between the half-life and the time to full recovery?
The half-life is the interval in which residual fatigue falls by exactly half, and it is constant: the drop from 80 to 40 percent takes as long as the drop from 10 to 5. Full recovery, by contrast, is asymptotic in an exponential model, so fatigue approaches zero without ever formally arriving. What the projection calls full recovery is really the point where the remainder falls below a negligible threshold. Counting half-lives is the quickest mental check: after four of them, 80 percent peak fatigue is down to 5 percent.
How do I estimate the peak fatigue percentage to enter?
Treat 100 percent as the state at which you could not have completed another meaningful set or interval, and scale down from there. A useful anchor is session load, the product of your session rating of perceived exertion and its duration: a 60-minute session at RPE 9 scores 540 and clearly outranks the same hour at RPE 5, which scores 300, while 120 minutes at RPE 7 scores 840 and outranks both. Precision matters less than consistency, because the value of the curve lies in comparing your own sessions on a stable scale.
Why does the model track only fatigue and not the fitness gained from the session?
This is a single-component decay curve, so it describes what is still weighing you down and says nothing about adaptation. Impulse-response models of training split each session into two traces: a fitness effect that is smaller in magnitude but decays slowly, and a fatigue effect that is larger but decays quickly. Readiness is the difference between them, which is why performance can peak days after a hard block rather than immediately. Use this curve to time the next session, not to predict how strong you will be.
How does fatigue from back-to-back sessions accumulate?
Residual fatigue does not reset when you train again, it adds to the new session's peak. If you start a workout carrying 25 percent left over and that workout would produce 60 percent on its own, you begin decaying from roughly 85 percent rather than 60, and the same half-life now needs longer to bring you back under a safe threshold. Repeat that pattern across a week and the floor creeps upward session by session, which is the arithmetic behind accumulated fatigue and the reason planned easy days exist.
References
Reviewed for accuracy by Sher, Sports Science & Nutrition Specialist · Editorial policy
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