Skip to main content
aifithub

Articles · 174 published · 877 citations

Long-form reference for lifters and runners.

Pillar guides go deep on the literature — Schoenfeld, Seiler, Morton, Kouri, Riegel. Standard guides answer a single question, with every specific number traceable to a source. No plans, no protocols, no “transform” language. Just what the evidence supports, with dated caveats.

Long-form canonical references

Pillars 37

13 min · 8 cites

Body Recomposition for Lifters: The Calorie Math

Body recomposition is real for specific populations under specific conditions. The four conditions, protein math scaled to LBM, 12-week example.

Read article →

14 min · 8 cites

The 2026 Evidence-Based Programming Guide

Evidence-based programming for 2026: volume, intensity, frequency, and specificity reviewed through the Schoenfeld meta-analyses, with dated caveats.

Read article →

13 min · 7 cites

Zone 2 Training: What the Literature Actually Says

Zone 2 training: polarised work, Seiler's 80/20, Stöggl & Sperlich 2014, and the San Millán mitochondrial framing — separated from the social-media version.

Read article →

11 min · 6 cites

DOTS vs Wilks vs GL: Scoring Coefficients Compared

Why the IPF moved from Wilks to IPF-GL in 2019 and to DOTS-style scoring for open comps, with coefficient behaviour plotted against bodyweight.

Read article →

12 min · 7 cites

Morton 2018: Protein at 1.6 g/kg for Lifters

Morton 2018 meta-analysis: 1.6 g/kg/day protein (95% CI upper 2.2) maximizes lean mass in lifters. Per-meal distribution, leucine, and cutting math.

Read article →

11 min · 7 cites

VO2 Max Field Tests: Which Derivation to Trust

VO2 max field tests compared: Cooper, Rockport, Bruce, Astrand, and the 12-min run — accuracy, population validity, and which derivation to trust.

Read article →

10 min · 5 cites

Race-Time Prediction: Where Riegel Breaks

Race-time prediction with the Riegel formula — its 1.06 exponent, the distance regimes where it holds, and where it produces unreliable estimates.

Read article →

11 min · 6 cites

TDEE Formulas Compared: Mifflin vs Harris vs Katch

TDEE formulas compared: Mifflin-St Jeor, Harris-Benedict, Katch-McArdle, WHO/FAO. Population, error bands, and when each estimator is appropriate.

Read article →

11 min · 5 cites

FFMI 25 Natural Limit: What Kouri 1995 Showed

Kouri 1995 proposed an FFMI 25 ceiling for natural lifters. Thirty years later, what still holds — and what the replication attempts showed.

Read article →

11 min · 6 cites

Body Composition: Bod Pod vs DEXA vs Calipers

Body composition for athletes: the sport-specific lean-mass and body-fat targets the literature actually supports, and the measurement-method error bands.

Read article →

12 min · 6 cites

FFMI Limits: What the Natty-Boundary Data Shows

The FFMI 25 ceiling is statistically informed but soft. Four confounders flip an honest natty into looks-juicy, and trajectory beats snapshot.

Read article →

13 min · 8 cites

Zone 2 Training: Literature, Methods, Limits

Zone 2 training literature, methods, and limits — heart-rate vs lactate vs RPE, evidence base, and where the popular framing breaks down.

Read article →

13 min · 8 cites

RPE Programming: Why the Math Beats the Coach

When RPE prescription dominates fixed %1RM, when it doesn't, and how to calibrate the scale so the math actually works for an intermediate lifter.

Read article →

11 min · 7 cites

Heart-Rate Zones: Methods Compared

Heart-rate zone methods compared: Karvonen, %HRmax, %HRR, lactate threshold — accuracy by training age, error bands, and which one for which goal.

Read article →

13 min · 6 cites

Race-Time Prediction: VDOT vs Riegel Failure Modes

Race-time prediction failure modes: where VDOT, Riegel, and Cameron break — distance regimes, training-status assumptions, and prediction-error bands.

Read article →

11 min · 6 cites

Block vs DUP Periodization: The Hypertrophy Math

Block periodization concentrates a stimulus. DUP rotates it. The math behind which produces more hypertrophy at a given fatigue cost.

Read article →

10 min · 6 cites

Sleep Debt vs Training Stress: The Interaction

Sleep debt and training stress compound nonlinearly. The TRIMP-adjusted recovery model and what 5 hours of sleep does to next-day output.

Read article →

10 min · 6 cites

Heat Acclimatization: Sodium and Plasma Volume

Heat acclimatization shifts plasma volume up 10-12% in 10-14 days. The sodium math that supports the adaptation and the workouts that drive it.

Read article →

10 min · 6 cites

Pre-Fatigue Training: When the Math Says It Helps

Pre-fatigue protocols (light isolation before compound) work for some populations. The literature on when they help vs when they reduce total volume.

Read article →

11 min · 6 cites

Carb Periodization for Hybrid Athletes

Hybrid athletes need different carbs on lift days vs run days. The g/kg math, fueling-window logic, and mode-by-mode periodization.

Read article →

12 min · 7 cites

Powerlifting Peaking Math

Powerlifting peaking compared: Smolov, Sheiko, and Texas Method — volume curves, recovery demands, and the meet-prep windows each handles best.

Read article →

11 min · 6 cites

Lean Bulk vs Aggressive Bulk: The Math

Lean bulks (200-300 cal surplus) vs aggressive bulks (500+). The literature on muscle gain rates and the long-term math when fat loss is included.

Read article →

10 min · 5 cites

Mini-Cuts: The 4-Week Math That Resets Body Fat Between Bulks

Mini-cuts (3-5 weeks aggressive deficit) reset body fat between bulk phases. The week-by-week math, recovery-debt cap, and re-feed protocol.

Read article →

11 min · 7 cites

Recovery Math: How HRV, Sleep, and RPE Predict

Recovery math: HRV, sleep, and session-RPE as predictors of next-day readiness. What the literature actually shows and what the consumer apps over-claim.

Read article →

11 min · 7 cites

Marathon Training Tapers

Marathon taper: the volume-reduction curve, intensity preservation, and the taper-week window where most performance benefit is realised.

Read article →

13 min · 12 cites

Velocity-Based Training: 1RM From Bar Speed

A load-velocity profile estimates your 1RM from sub-maximal bar speed, no max attempt needed. How the math works, the research, and a worked example.

Read article →

12 min · 11 cites

Concurrent Training Interference: What the 2026 Evidence Shows

Concurrent training interference, reviewed against the 2026 evidence on strength and endurance: effect size, modality, and programming windows.

Read article →

12 min · 10 cites

Detraining: How Fast You Lose Strength and VO2 Max

Mujika 2003 reviewed every detraining study to date. Strength holds for 4 weeks then drops 7 to 10 percent per week. VO2 max declines 7 percent per week.

Read article →

12 min · 8 cites

Why You Stalled at a 1.5x Bodyweight Squat

Why your squat stalled at 1.5x bodyweight — and the four programming, recovery, and technique levers most lifters should pull before adding volume.

Read article →

13 min · 14 cites

Female Athlete Physiology: Where Formulas Fail

Female-athlete physiology: where standard fitness formulas (TDEE, body-comp, 1RM) under- or over-predict, and the corrections backed by current literature.

Read article →

13 min · 12 cites

Polarized vs Threshold Training: What the Research Shows

Polarized vs threshold training: a 2026 evidence review of intensity distribution in endurance athletes — what wins, where, and at what training age.

Read article →

11 min · 10 cites

Hybrid Athlete Macro Splits

Hybrid athlete macros: the split between strength and endurance days, periodised carbs around hard sessions, and protein scaling for two-stress training.

Read article →

12 min · 9 cites

Junk Volume in Hypertrophy

Junk volume in hypertrophy: how to read your training log for the sets that aren't producing growth, scoped to the 10-20 sets/week meta-window.

Read article →

12 min · 9 cites

Marathon Pace and Elevation Adjustments

Marathon pace and elevation: a validated correction for total climb / descent — Strava grade-adjusted pace, Naismith's rule, where they break.

Read article →

11 min · 11 cites

Travel and Jet Lag for Athletes: The Recovery Math

Travel and jet lag for athletes: the time-zone math, melatonin and light exposure timing, and how performance decay tracks with hours misaligned.

Read article →

16 min · 14 cites

The 2026 Wearable & AI-Coaching Accuracy vs Value Index

The 2026 wearable accuracy vs value index: which Garmin, Oura, WHOOP, Apple Watch and Eight Sleep metrics are validated, and at what price. Sourced.

Read article →

9 min · 5 cites

TDEE Maintenance Calorie Reference: Age and Activity Level 2026

TDEE maintenance calories by Mifflin-St Jeor: age 20–60, five activity levels. Male 80 kg/178 cm and female 65 kg/165 cm reference grids, engine-computed at build time.

Read article →

Focused how-to articles

Standards 51

8 min · 5 cites

How to Build Muscle as a Beginner

Building muscle as a beginner: the first-12-month volume / intensity / nutrition prescription — what the meta-analyses agree on for new lifters.

Read article →

8 min · 5 cites

How to Break a Weight-Loss Plateau

Breaking a weight-loss plateau: adaptive thermogenesis math, refeed protocols, training-volume changes, and the four leverage points before changing tools.

Read article →

7 min · 5 cites

TDEE for Athletes: Why Formulas Understate You

TDEE for athletes: why standard equations under-predict for hybrid and endurance training. Activity-factor adjustments and exercise-energy add-ons.

Read article →

8 min · 5 cites

How to Train for a 5k

A ten-week plan built around polarised training, aerobic base work, and a weekly VO2 max session — with pacing pulled from Riegel.

Read article →

7 min · 4 cites

How to Plan a Deload Week

Deload week planning: when to take one (set/rep stagnation, RPE drift, sleep markers), how to scale volume vs intensity, and what to monitor on return.

Read article →

8 min · 4 cites

How to Structure a Powerlifting Meet Day

Powerlifting meet structure: opener / second / third attempt selection math, warm-up timing, equipment rules, and the day-of decisions that win meets.

Read article →

7 min · 5 cites

How to Eat Enough Protein

Eating enough protein: the daily target by training goal, leucine threshold per meal, distribution across the day, and plant-based bioavailability adjustments.

Read article →

7 min · 4 cites

How to Count Macros

Counting macros: protein, carbs, and fat targets by training goal, meal-by-meal practical splits, and the tracking-app pitfalls that bias intake low.

Read article →

7 min · 4 cites

How to Estimate a 1RM Without Testing for One

Estimate a 1RM without testing: Epley, Brzycki, Lombardi, O'Conner, Wathan, and Mayhew — error bands, rep-range fit, and safety.

Read article →

7 min · 4 cites

How to Use RPE for Training

The 1–10 RPE scale, reps-in-reserve framing, and how to anchor percentages to a moving 1RM instead of a stale one.

Read article →

7 min · 5 cites

How to Use Heart Rate Zones

Heart-rate zones: which method (Karvonen, %HRmax, lactate threshold) for which goal, and how to set zone boundaries when you don't have a lab test.

Read article →

7 min · 5 cites

How to Improve VO2 Max

VO2 max improvement: the four interventions with the largest meta-analytic effect — interval volume, threshold work, training age, and altitude exposure.

Read article →

7 min · 5 cites

How to Improve Sleep for Recovery

Improve sleep for recovery: stage architecture, evening blue-light load, caffeine half-life, sleep-restriction, and what actually moves HRV the next day.

Read article →

7 min · 4 cites

How to Measure Body Fat at Home

Measure body fat at home: skinfold calipers, bioelectrical impedance, Navy method, and DEXA reality-check — accuracy, error bands, and method choice.

Read article →

7 min · 4 cites

How to Run a Mini Cut

Run a mini-cut: the 4-6 week deficit window, weekly weight-loss target, training-volume scaling, and re-feed criteria to avoid muscle loss.

Read article →

10 min · 6 cites

How to Assess and Improve Mobility

Assess flexibility with sit-and-reach: a hamstring and lower-back ROM proxy, not whole-body mobility. The dose-response and a 6-week protocol.

Read article →

7 min · 3 cites

20-Week Recomp: 84kg/24% to Target 18% Body Fat

Body recomp plan for an 84 kg male at 24% body fat, 20-week target 18%: 338 kcal/day deficit, 0.31 kg/week pace, 6.15 kg fat to lose, 140 g protein.

Read article →

6 min · 3 cites

Calorie Deficit: 85 kg to 75 kg in 20 Weeks at 2200 TDEE

Calorie deficit 550 kcal/day: eat 1650 kcal for an 85 kg adult at 2200 TDEE. Loss pace 0.5 kg/week, 25% deficit, 77000 kcal total cut over 20 weeks.

Read article →

7 min · 3 cites

Concurrent Training Interference: 4 Lifts, 35km Running, 1 Rest Day

Concurrent training interference from 4 lifts + 35 km running: strength -16.3%, hypertrophy -21.5%, power -31.5%, plus the split rule that fixes it.

Read article →

6 min · 3 cites

Creatine Loading vs Maintenance for an 82kg Lifter

Creatine loading 24.6 g/day for 7 days then 3 g/day maintenance for an 82 kg lifter. 262 g per month, hydration baseline 2.87 L, math and trade-off.

Read article →

7 min · 3 cites

Cycling FTP Zones: 250W at 75kg, 3.33 W/kg Walkthrough

Cycling power zones for a 250W FTP / 75kg rider: 3.33 W/kg trained category, Z2 endurance 140-188W, Z4 threshold 228-263W, Z5 VO2max 265-300W.

Read article →

7 min · 3 cites

Detraining Decay: 4 Weeks Off for a 3-Year Trained Lifter

Detraining math: 150 kg 1RM after 4 weeks off for a 3-year trained lifter loses 2.9% to 145.7 kg. Retraining 2 weeks to peak, the decay curve, and gaps.

Read article →

7 min · 3 cites

DOTS, Wilks, GL: An 83kg/510kg Male Lifter Scored Three Ways

DOTS 344.3, Wilks 340.7, IPF GL 70.6 for an 83 kg raw male lifter with a 510 kg total. The classification splits, why DOTS replaced Wilks, and what shifts.

Read article →

7 min · 4 cites

Female Athlete Formula Suite: A 30-Year-Old in Regular Cycle

Female athlete formulas for 65 kg, 168 cm, 24% body fat, regular cycle. The luteal-versus-follicular caloric drift and where male equations fail.

Read article →

7 min · 3 cites

FFMI for the Intermediate Female Lifter: A 60kg/165cm/22% Walkthrough

FFMI for a 60kg, 165cm, 22% body-fat female intermediate lifter: adjusted 18.10 walkthrough, percentile context, and why the Kouri 25 cap was male-only.

Read article →

7 min · 3 cites

HRV Deload Trigger: A 7-Day Decline from Baseline 56 to Mean 50

HRV trend 55, 57, 52, 48, 46, 47, 45 against baseline 56 (SD 4.2). Rolling deviation -10.7%, five days below SWC, deload recommendation: yes. The math.

Read article →

7 min · 3 cites

Hybrid Training Plan: 30km Running, 70/20/10 Intensity, Three Lifts

Hybrid training math for 30 km/week running (70% easy, 20% tempo, 10% interval) plus three lifts. Session map, recovery debt, realistic goal window.

Read article →

6 min · 4 cites

16:8 Intermittent Fasting Starting at Noon: A Realistic Schedule

Intermittent 16:8 with a noon first meal: the eating window, training-window timing, and where protein distribution math creates a real problem.

Read article →

7 min · 3 cites

Junk Volume Detector: A 3-Week Stalling Squat Log

Junk volume read of a 3-week squat log progressing from 100 to 103 kg: 0% junk sets, all 9 sets effective. Volume load delta drops from 2.5% to 0.5%.

Read article →

7 min · 3 cites

Macro Cycling for an 80kg Male Recomp at 2500 kcal TDEE

Macro cycling for an 80 kg male recomp: 2600 kcal training days, 2200 kcal rest. Protein 131 g flat, carbs 239-375 g, fats 64-80 g counter-cycle.

Read article →

7 min · 3 cites

Marathon Pace on a Net-Downhill Course: A Boston-Style Walkthrough

Marathon pace math for a Boston-style profile: 145m gain, 290m loss, 200-minute target. The 4:44/km flat-equivalent split and where the model breaks.

Read article →

7 min · 3 cites

Meet-Day Attempt Selection for a 300kg-Total Lifter at Moderate Confidence

Meet-day attempt math for 140 squat, 100 bench, 180 deadlift at moderate confidence. The opener spread, third-attempt risk, and day-of revision rule.

Read article →

7 min · 3 cites

Muscle Gain Potential: A 178cm Narrow-Frame Male Case

Muscle gain ceiling 80.3 kg for a 178 cm, 17.5 wrist / 22 ankle male. 16.3 kg remaining, 79.7% of potential reached, ~3 years to ceiling. Casey Butt math.

Read article →

6 min · 3 cites

From a 40-Minute 10K to a Half Marathon: A Riegel Walkthrough

Forty-minute 10K via Riegel predicts 1:28:15 for the half marathon and 3:04:00 for the marathon. The 1.06 exponent, where it holds, where it lies.

Read article →

6 min · 3 cites

Marathon Taper from 90 km Peak: A 2-Week Volume Reduction Plan

Marathon taper from 90 km peak volume: week minus 2 holds 90 km (40.5 km long), week minus 1 drops 60% to 36 km. Intensity 90%, frequency cut 20%.

Read article →

6 min · 3 cites

Bench Press RPE 8 for 5 Reps: The Percentage Walkthrough

Bench press RPE 8 for 5 reps maps to 81.1% of 1RM on the RTS table. For a 140 kg bench 1RM that is 113.5 kg. The math and the velocity cross-check.

Read article →

7 min · 3 cites

Daniels VDOT Paces for a 3:15 Marathon PR: Full Zone Breakdown

Daniels VDOT paces for a 3:15 marathon PR (4:37/km, VDOT 48.7). Easy 5:25/km, Marathon 4:45, Threshold 4:26, Interval 4:00, predicted 5K 20:24.

Read article →

8 min · 3 cites

Smolov Base Cycle for a 150 kg Squat: 4-Week Walkthrough

Smolov Base mesocycle for a 150 kg squat: weekly volume 136 reps, 4 sessions per week, weights from 105 kg to 135 kg. Week-by-week loading and the cap.

Read article →

6 min · 4 cites

Where a 140kg Squat Puts an 80kg Male in the Strength Distribution

Engine output for an 80kg male squatting 140kg single. The percentile rank, the StrengthLevel dataset context, and where age curves take over.

Read article →

7 min · 3 cites

Marathon Sweat Rate: 70kg Runner, 2% Body Mass Loss in Warm Conditions

Marathon sweat rate 0.57 L/h, total loss 2.3 L over a 4-hour temperate race. Body mass loss 2.1%, 460 ml/h fluid plan, 529 mg/h sodium target.

Read article →

6 min · 3 cites

1500m Freestyle in 30 Minutes: Pace and SWOLF Walkthrough

1500m freestyle in 30:00 means 2:00/100m, 1:49.7/100yd, SWOLF 50, Tempo effort. The pace breakdown, stroke efficiency, and follow-on training plan.

Read article →

7 min · 3 cites

TDEE for a Sedentary Office Worker vs a Warehouse Picker

TDEE gap for two 32-year-old 80kg/180cm men: same BMR 1770, different activity multipliers, and the roughly 700 kcal occupational difference.

Read article →

7 min · 3 cites

Velocity-Based 1RM: 180 kg Squat at 0.50 m/s in Practice

Velocity-based 1RM math: 180 kg squat at 0.50 m/s estimates 233.2 kg (95% CI 221.5-244.8). The strength-speed zone read and where bar speed lies.

Read article →

6 min · 3 cites

Cooper 12-Minute Test: 2400m for a 30-Year-Old Male

Cooper test 2400 m in 12 min for a 30-year-old, 75 kg male: VO2max 42.4 ml/kg/min, classification Good. The formula, calibration, and protocol notes.

Read article →

8 min · 3 cites

Wendler 5/3/1 at TM 90%: A Cycle Walkthrough for a 420kg Total Lifter

Wendler 5/3/1 at 90% training max: squat 140, bench 100, deadlift 180, OHP 60. Week 1 to deload weights, AMRAP targets, and progression logic.

Read article →

7 min · 3 cites

Zone 2 Heart Rate for a 30-Year-Old, RHR 50: Four Methods Compared

Zone 2 HR for a 30-year-old endurance athlete with resting heart rate 50 bpm: Karvonen 134-148, Maffetone 140-150, percentage 114-133, lactate 125-141.

Read article →

7 min · 5 cites

Is MyFitnessPal's TDEE Accurate in 2026?

MyFitnessPal's TDEE in 2026 isn't a true TDEE: it returns a Mifflin-St Jeor goal, accurate within 10% for 70-82% of people. What that means for you.

Read article →

8 min · 7 cites

Best Macro Tracking Apps 2026: MacroFactor vs Cronometer vs MyFitnessPal

Best macro tracking apps 2026: MacroFactor vs Cronometer vs MyFitnessPal on price, database accuracy, and adaptive TDEE, with studies cited.

Read article →

8 min · 7 cites

Garmin vs COROS vs Polar Running Watch 2026: Marathon Pick

Garmin vs COROS vs Polar running watch 2026 for marathon and half training: verified battery, GPS accuracy, training metrics, and price compared.

Read article →

8 min · 6 cites

Smart Scale Body-Fat Accuracy 2026: Withings vs Renpho vs Eufy

Smart scale body-fat accuracy 2026: Withings vs Renpho vs Eufy, and how close BIA really gets to DEXA, with peer-reviewed validation studies cited.

Read article →

9 min · 6 cites

Whoop vs Oura vs Garmin 2026: HRV & Recovery Accuracy

Whoop vs Oura vs Garmin 2026: HRV, recovery, and sleep tracking accuracy compared against ECG and polysomnography in independent peer-reviewed studies.

Read article →

General fitness estimates — not medical advice. Consult a healthcare professional for medical decisions.