Zone 2 Cardio Plan

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name: Zone 2 Cardio Plan
description: Use when someone asks to build a steady-state cardio plan, train an aerobic base or Zone 2, structure easy or endurance weekly cardio, train by heart-rate zones, or improve resting heart rate, VO2, or endurance. Builds a heart-rate-zone aerobic training block with session structure, modality choice, and progression. General fitness guidance, not medical advice. Do NOT use to design a strength or lifting program (use Strength Training Plan), high-intensity interval conditioning, HIIT, or circuits (use Conditioning & HIIT Program), or a mobility/flexibility routine (use Mobility Routine).
---

# Zone 2 Cardio Plan

This skill builds an aerobic-base training block organized around heart-rate zones, with Zone 2 as the foundation. It picks a modality, lays out a weekly structure, and progresses load toward an endurance goal. The default is a 4-week block, repeatable. This is general fitness guidance, not medical advice - anyone with cardiac risk factors, on heart-rate-affecting medication, or returning from illness or injury should clear endurance training with a physician first.

## Establish Zones First

Anchor every prescription to heart rate, not pace or feel alone. Estimate maximum heart rate as 220 minus age as a starting point, and flag it as a rough estimate - a lab or field test is more accurate. Define the zones as percentages of max HR: Zone 1 (50-60%) recovery; Zone 2 (60-70%) aerobic base; Zone 3 (70-80%) tempo; Zone 4 (80-90%) threshold; Zone 5 (90-100%) VO2 max. Give the user their actual beats-per-minute ranges, not just percentages. The Zone 2 test in practice: a pace where the user can hold a conversation in full sentences but would prefer not to. If they can't talk, they're too high; most people drift into Zone 3 and stall their base.

## Choose the Modality

Match the modality to the goal and to joints. Running builds the most specific endurance and the highest impact; cycling and rowing are lower-impact and let beginners hold Zone 2 longer without form breakdown; rucking (loaded walking) suits those building work capacity with minimal equipment. Default to the user's stated goal sport. If they have no specific goal, default to whatever they will do consistently and can sustain for 45+ minutes without joint pain. It is fine to mix modalities across a week to manage impact, but keep the bulk of Zone 2 volume in one primary modality for adaptation.

## Build the Weekly Structure

Most aerobic adaptation comes from time in Zone 2, so the week is mostly easy volume. For a typical 4-day week: three Zone 2 sessions plus one higher-intensity session. Polarize the distribution - roughly 80% of weekly time in Zone 1-2, 20% in Zone 3-5. Do not let the easy days creep into Zone 3; that "moderate-intensity rut" is the most common failure. Place the hard session with at least one easy or rest day on either side. A sample week: Zone 2 (45 min), rest, Zone 2 (45 min), Zone 4/5 intervals (e.g. 5×3 min hard / 3 min easy), rest, Zone 2 long (60-75 min), rest.

## Set Session Duration and the VO2 Stimulus

Zone 2 sessions should be long enough to matter: start at 30-45 minutes and build toward 60-90 for the long session. Below ~30 minutes the aerobic stimulus is thin. For VO2 max and top-end fitness, prescribe one weekly interval session in Zone 4-5: classic formats are 4×4 min hard / 3 min easy, or 30/30s (30 sec hard, 30 sec easy ×10-20). Keep intervals to one session per week during a base block - more high intensity erodes the aerobic emphasis and recovery.