Detraining Decay Formula
Detraining is asymmetric. Strength is preserved much longer than VO2 max. Mujika 2010: strength drops 5-10% after 4 weeks of rest, 15-20% after 8 weeks. VO2 max drops faster — 7% per week for the first 2-3 weeks. One session per week at high intensity preserves most strength gains.
Formula
Copy the exact expression or work through it step by step below.
strength_remaining_pct = 100 − (5 × weeks_off^0.7)
vo2_max_remaining_pct = 100 − (7 × weeks_off × decay_factor)
decay_factor = 1.0 (weeks 1-3), 0.4 (weeks 4-12), 0.1 (weeks 12+) Variables
weeks_off
Weeks of complete inactivity
Continuous weeks of zero training in that modality. Reduced training (≥1 session/week at ≥70% intensity) extends the timeline 2-3x.
strength_remaining_pct
Strength preservation
% of pre-break 1RM retained. Sublinear decay — first 4 weeks lose ~5-10%, next 4 weeks another 5-10%, then plateau.
vo2_max_remaining_pct
VO2 max preservation
% of pre-break VO2 max retained. Faster early decay (heart-stroke-volume reversal) then slower. Reaches stable ~80% baseline after 8-12 weeks.
decay_factor
Phase-dependent decay rate
Cardiovascular adaptations have fast early decay (acute training adaptations reverse first) followed by slower decline of more stable adaptations.
Step By Step
- 1
Identify your weeks of inactivity (or near-inactivity) since the break started.
Surgery → 6 weeks no training.
- 2
Estimate strength loss: 5 × weeks^0.7.
5 × 6^0.7 = 5 × 3.36 = ~17% strength loss. 200 kg deadlift → ~166 kg current capacity.
- 3
Estimate VO2 max loss: phase-weighted decay.
First 3 weeks: 7 × 3 × 1.0 = 21%. Weeks 4-6: 7 × 3 × 0.4 = 8.4%. Total = ~29% (but capped at 20-25% baseline floor).
- 4
Plan return-to-training: 50% of pre-break volume for 2 weeks, ramp 10% weekly back to baseline.
Pre-break 80 km/week → start at 40 km, ramp +10% to ~70 km by week 5.
- 5
Strength returns faster than VO2 max thanks to muscle memory (nuclear domain theory). Expect to regain ~75% of lost strength in 4 weeks; full restoration in 8-12 weeks.
Lost 17% → regain ~13% in 4 weeks → back to 193 kg, with 200 kg target by week 8.
Worked Example
Lifter takes 6 weeks completely off after injury, planning return
Pre-break deadlift 1RM
200 kg
Pre-break VO2 max
55 ml/kg/min
Weeks off
6
Strength: 200 × (1 − 0.05 × 6^0.7) = 200 × 0.832 = 166 kg current 1RM (−17%) VO2 max: 55 × (1 − 0.07 × (3 × 1.0 + 3 × 0.4)) = 55 × 0.706 = 39 ml/kg/min (−29%)
Current capacity ~166 kg deadlift, ~39 ml/kg/min. Return-to-training: start at 60-65% of new estimated 1RM (~100 kg deadlift), do not test 1RM for 4-6 weeks. Cardio: start with 50% of pre-break volume, low-moderate intensity, build over 8 weeks.
Common Variations
Try These Tools
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One-Rep Max Calculator
Estimate one-rep max with Epley, Brzycki, and Lombardi formulas.
VO2 Max Estimator
Estimate aerobic capacity with Cooper run, Rockport walk, or no-exercise questionnaire methods.
Progressive Overload Planner
Project lifting progression with weekly overload and planned deload cycles.
Sources & References
- Mujika & Padilla (2000). Detraining: loss of training-induced physiological and performance adaptations. — Sports Medicine — two-part review (Parts I + II), foundational reference
- Mujika (2010). Intense training: the key to optimal performance. — Sports Medicine — updated detraining timelines
- Bruusgaard et al. (2010). Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining. — PNAS — original nuclear domain (muscle memory) finding
- Coyle et al. (1984). Time course of loss of adaptations after stopping prolonged intense endurance training. — Journal of Applied Physiology — VO2 max decay timeline