How Hybrid Athlete Macro Split works

Scope

Computes daily macro targets for athletes who run and lift in the same week, with separate macros for training and rest days. Protein, carbs, and fat each scale to a different training-load anchor.

Formula

Protein per kg by lifting frequency:

• ≤ 2 sessions: 1.8 g/kg
• 3–4 sessions: 2.0 g/kg
• ≥ 5 sessions: 2.2 g/kg

Carbs per kg by weekly run volume:

• < 20 km: 4 (training) / 3 (rest) g/kg
• 20–50 km: 5.5 / 4 g/kg
• 50–80 km: 6.5 / 4.5 g/kg
• > 80 km: 7.5 / 5 g/kg

Fat: 0.9 g/kg training / 1.0 g/kg rest (no upper bound).

Calories balance from the macro grams: protein × 4 + carbs × 4 + fat × 9.

Data sources

1. Burke LM, Hawley JA, Wong SH, Jeukendrup AE. Carbohydrates for training and competition. J Sports Sci. 2011;29(s1):S17-S27. — PMID 21660838. Carb intake bands by training volume.
2. Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr. 2014;11(1):20. — PMID 24864135. Protein intake guidance during caloric deficit and lean-mass preservation.
3. Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016;116(3):501-528. — PMID 26891166. Joint-position protein and carb thresholds for athletes.

Assumptions

• Bodyweight is stable (the tool doesn't add a deficit / surplus). Use it as a maintenance estimate, then layer goal-driven kcal adjustments on top.
• Body fat % is reasonably accurate (DEXA / hydrostatic / consistent caliper). Lean mass drives the protein per-kg target.
• Run volume is the dominant aerobic input. Cycling / rowing volume isn't directly handled — convert to a km-equivalent first.

Approximation range

Protein ±10 g/day vs published bands. Carbs ±0.5 g/kg per band. Calorie total carries the sum of these errors (±150–250 kcal/day).

Limitations

• Doesn't model meal timing or pre/post-session carb periodisation (Burke 2011 details those).
• Doesn't account for fibre, hydration, or micronutrient targets.
• Vegetarian / vegan athletes will need to scale protein up ~15% to account for plant protein bioavailability (ISSN 2017).

Reproducibility

75 kg, 18% bf, 35 km/wk, 3 lifts, 5 training days. Protein = 75 × 2.0 = 150 g. Carbs (training) = 75 × 5.5 = 412 g. Fat (training) = 75 × 0.9 = 67 g. Training-day kcal = 150×4 + 412×4 + 67×9 = 2851 kcal.

Change log

• 2026-05-08: methodology page first published.

Related tools

• Macro Cycling Calculator — Pure lifter-focused training/rest day macros.
• Protein Intake Calculator — Standalone protein target.
• Concurrent Training Interference — Plan how concurrent the block is.

Worked example

Computed by the same engine bundle served at /engines/hybrid-athlete-macro-split.js. Re-runnable: the values below are the literal output of compute(engineInput).

FAQ

What does the Hybrid Athlete Macro Split calculate?

Methodology for the Hybrid Athlete Macro Split: protein scaling by lifting volume, carb scaling by run volume, and training/rest day split.

What inputs does the Hybrid Athlete Macro Split require?

It takes the following inputs: weight kg, body fat pct, run volume km week, lift sessions week, training days.

What does the Hybrid Athlete Macro Split return?

It returns: proteinDailyG, carbsDailyAvgG, fatDailyAvgG, weeklyAverageCalories, leanMassKg, trainingDay, restDay.

Is the Hybrid Athlete Macro Split 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 Hybrid Athlete Macro Split belong to?

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