What does the Concurrent Training Interference Estimator calculate?

Methodology for the Concurrent Training Interference Estimator: Wilson 2012 effect sizes, modality scaling, and recovery mitigation.

What inputs does the Concurrent Training Interference Estimator require?

It takes the following inputs: lift sessions per week, run volume km per week, run intensity, recovery days.

What does the Concurrent Training Interference Estimator return?

It returns: strengthGainAttenuationPct, hypertrophyAttenuationPct, powerAttenuationPct, riskBand, recommendedSplit, notes.

Is the Concurrent Training Interference Estimator free to use?

Yes. It runs entirely client-side in your browser with no signup, and is also importable as an ES module engine for AI agents.

What category does the Concurrent Training Interference Estimator belong to?

Planning. See the methodology above for formulas, assumptions, and limitations.

Methodology: Concurrent Training Interference Estimator

Scope

Estimates how much running attenuates strength, hypertrophy, and power gains when stacked alongside a lifting program, based on the Wilson 2012 meta-analysis. Useful for hybrid athletes balancing endurance training with strength goals.

Formula

composite = volume_signal × intensity_factor × recovery_relief

volume_signal = min(1.5, run_km_per_week / 50)
intensity_factor = easy 0.5, moderate 1.0, tempo 1.4, intervals 1.7
recovery_relief = max(0, 1 − recovery_days × 0.25)

Attenuation %s = base × composite where base values come from Wilson 2012 effect-size differences:

Strength base = 31% (effect size diff 0.31)
Hypertrophy base = 41% (effect size diff 0.41)
Power base = 60% (effect size diff 0.96, scaled)

Data sources

Wilson JM, Marin PJ, Rhea MR, Wilson SM, Loenneke JP, Anderson JC. Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. J Strength Cond Res. 2012;26(8):2293-2307. — PMID 22002517. Effect-size differences for strength (0.31), hypertrophy (0.41), and power (0.96).
Plews DJ, Laursen PB. Training adaptation and HRV in elite endurance athletes. Sports Med. 2013;43(9):773-781. — Recovery-time mitigation evidence.

Assumptions

Running is the aerobic modality. Cycling produces ~25% less interference (Wilson 2012); the model under-estimates interference for runners only by definition.
Lift sessions are full-body / lower-body weighted — pure upper-body lifting interferes less.
"Recovery days" means 24-h gaps between conflicting modalities, not full rest days from any training.

Approximation range

The model is heuristic. Wilson 2012 reports group means; individual response variance is wide (±15%). Use as a planning prompt, not a precise prescription.

Limitations

Does not model nutrition, sleep, or genetic responder profile.
Cycling vs running interference differential not exposed in the input.
Cannot account for concurrent training history — first-time concurrent trainees have a steeper learning curve and report larger interference initially.

Reproducibility

4 lift sessions, 50 km/wk easy running, 1 recovery day: composite = (50/50)×0.5×0.75 = 0.375. Strength attenuation = 31×0.375 = 11.6%.

Change log

2026-05-08: methodology page first published.

Hybrid Training Planner — Schedule the split this tool recommends.
Hybrid Athlete Macro Split — Fuel the concurrent block.

Worked example

Computed by the same engine bundle served at /engines/concurrent-training-interference.js. Re-runnable: the values below are the literal output of compute(engineInput).

Input

tool: concurrent_training_interference
lift_sessions_per_week: 4
run_volume_km_per_week: 30
run_intensity: moderate
recovery_days: 1

Output

strengthGainAttenuationPct: 14
hypertrophyAttenuationPct: 18.5
powerAttenuationPct: 27
riskBand: moderate
recommendedSplit: Current load is within manageable concurrent-training territory.
notes: []

FAQ

What does the Concurrent Training Interference Estimator calculate?: Methodology for the Concurrent Training Interference Estimator: Wilson 2012 effect sizes, modality scaling, and recovery mitigation.
What inputs does the Concurrent Training Interference Estimator require?: It takes the following inputs: lift sessions per week, run volume km per week, run intensity, recovery days.
What does the Concurrent Training Interference Estimator return?: It returns: strengthGainAttenuationPct, hypertrophyAttenuationPct, powerAttenuationPct, riskBand, recommendedSplit, notes.
Is the Concurrent Training Interference Estimator free to use?: Yes. It runs entirely client-side in your browser with no signup, and is also importable as an ES module engine for AI agents.
What category does the Concurrent Training Interference Estimator belong to?: Planning. See the methodology above for formulas, assumptions, and limitations.