gym-load-planner

Use when lifting weights and wondering what load to use — estimates true 1RM from reps@weight (Epley + Brzycki consensus), builds %-1RM loading tables per goal (strength 80-90%, hypertrophy 65-80%, endurance 50-65%), plans progressive-overload blocks with automatic deload weeks, solves barbell plate math for any plate set, and tracks e1RM trend with next-session load suggestions.

Overview

The gym has two universal questions: "how much should I lift?" and "how much did I get stronger?" Most people answer both by guessing — they add weight when it feels easy and stall for months.

This skill answers both with arithmetic instead of vibes:

1. 1RM estimation — Epley (w × (1 + r/30)) and Brzycki (w × 36/(37−r)) formulas, averaged, valid for reps ≤ 12, with a range showing the disagreement between the two models.
2. Loading tables — exact weights and rep targets per goal from the classic %-1RM zones, plus the "rep-max" column (what you could lift for 5, 8, 12 …).
3. Progression planning — a linear-progression block (novice: +2.5 kg on lower-body lifts, +1.25–2.5 kg upper, each session the previous load is completed at target reps) and a double-progression block (intermediate: fix the weight, add reps 8→12, then raise weight and reset reps), each with a deload week every 4th week (−10 %).
4. Plate math — exact per-side plate stacks for a target bar weight, kg or lb, with remainder warnings when the target isn't loadable.
5. Progress log — record sets, watch estimated 1RM trend, and get the next session's working loads according to your progression rule.

When to Use

• "I squatted 100 kg × 8 — what's my 1RM / what weight for 5×5?"
• Starting a program: which loads, how do they progress week to week?
• "Bar + which plates = 92.5 kg per my gym's plate set?"
• Stalled progress: when to switch from linear to double progression?
• Reviewing a training log: is e1RM actually trending up?

Don't use for: 1RMs estimated from reps > 12 (formula error grows fast — treat such estimates as rough), coaching elite athletes (they need individualized periodization), or medical/rehab loading decisions.

Quick Start

bash

# 1RM estimate + full percentage table from a rep max
python3 scripts/gym_load.py one-rm --weight 100 --reps 8

# Training loads for a goal (from known or estimated 1RM)
python3 scripts/gym_load.py table --one-rm 125 --goal strength

# 8-week progressive overload block
python3 scripts/gym_load.py plan --one-rm 125 --goal strength \
    --weeks 8 --increment 2.5 --top-reps 5

# What plates per side for 92.5 kg (20 kg bar)?
python3 scripts/gym_load.py plates --target 92.5 --bar 20
python3 scripts/gym_load.py plates --target 225 --unit lb

# Log sets and get next-session loads
python3 scripts/gym_load.py log add --lift "bench press" --weight 80 --reps 8
python3 scripts/gym_load.py log add --lift "bench press" --weight 80 --reps 10
python3 scripts/gym_load.py log next --lift "bench press" --rule double

The Science in Brief

1RM formulas

Formula	Equation	Best for
Epley	1RM = w × (1 + r/30)	≤ 10 reps, most lifts
Brzycki	1RM = w × 36 / (37 − r)	≤ 10 reps, slightly lower estimates

The tool reports both plus their mean. When the two disagree by > ~5 % your rep count is outside the reliable zone — trust it less.

%-1RM zones by goal

Goal	%1RM	Reps/set	Rest	Sets
Strength	80–90 %	3–6	3–5 min	3–5
Hypertrophy	65–80 %	8–12	1.5–3 min	3–4
Endurance	50–65 %	15–20	60–90 s	2–3

Rep-max conversion (Epley inverse): weight for R reps = 1RM / (1 + R/30).

Progression models

• Linear progression (novice, ~first 6–12 months): add a fixed increment every session you hit all target reps. Squat/deadlift +2.5 kg, bench/row +1.25–2.5 kg. Fails 2–3 sessions in a row → time for the intermediate model.
• Double progression (intermediate): pick a rep range (e.g. 8–12). Work at a fixed weight until you hit the top of the range on ALL sets, then add weight (~2.5–5 %) and return to the bottom of the range.
• Deload: every 4th week drop working loads ~10 % and reps; the plan command schedules this automatically. Deloads are when the adaptation you stimulated gets realized.

Plate math

Greedy largest-plate-first per side; warns if the target is unreachable with your plates (e.g. 93 kg with 2.5 kg granularity and a 20 kg bar → you can do 92.5 or 95, not 93).

Common Pitfalls

1. Estimating 1RM from high-rep sets. A 20-rep max estimate can be off by 10 %+; the tool flags disagreement but honesty starts with the input.
2. Skipping deloads. Fatigue masks fitness; 8 weeks without a down week is how linear progression dies at week 6.
3. Adding weight when reps weren't hit. The rule is progression contingent on completing the target; the log next command encodes it.
4. Jumps too big. +2.5 kg on bench is ~2–3 % — correct. +10 kg is a plateau generator.
5. Testing actual 1RM too often. Estimate it monthly from a 5–8 rep set; true max singles are a skill and a fatigue event, not a metric.

Verification Checklist

• one-rm prints Epley, Brzycki, mean, and flags disagreement > 5 %
• table weights are consistent across zones (strength > hypertrophy > endurance)
• plan inserts a deload every 4th week at −10 % loads
• plate stacks load the target exactly, or a nearest-loadable warning appears
• log next --rule linear adds increment only when top reps were completed

Examples

text

$ python3 scripts/gym_load.py one-rm --weight 100 --reps 8
Epley:    126.7 kg
Brzycki:  123.8 kg
Mean:     125.2 kg   (formulas agree within 2.3% — good)

$ python3 scripts/gym_load.py plates --target 92.5 --bar 20
Per side: 25 + 10 + 1.25 kg  →  total 92.5 kg  ✓

Formulas: Epley (1985), Brzycki (1993) — both established exercise-science 1RM predictors. Zones reflect widely used NSCA-style guidelines. Individual response varies; loads are starting points, not prescriptions.