Aerobic Intensity Classification (Light / Moderate / Vigorous)

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DefinitionA short reference note, not a full lesson.

Definition

ACSM's master table for translating "moderate" and "vigorous" into numbers across every common metric — %HRR/VO2R, %HRmax, RPE, and METs.

Detail

ACSM classifies aerobic intensity into light, moderate, and vigorous bands, defined across several metrics so any available tool can be used. The relative metrics (%HRR, %VO2R) and the absolute metric (METs) do not map perfectly onto each other, but the bands are:

Intensity	%HRR or %VO2R	%HRmax	RPE (6–20)	RPE (CR10)	METs
Light	30–39%	57–63%	9–11	<5	2.0–2.9
Moderate	40–59%	64–76%	12–13	5–6	3.0–5.9
Vigorous	60–89%	77–95%	14–17	7–8	≥6.0
Near-maximal / maximal	≥90%	≥96%	≥18	≥9	—

Key thresholds to remember:

Moderate intensity: 40–59% HRR/VO2R, 64–76% HRmax, RPE 12–13, 3.0–5.9 METs — "can talk but not sing" on the talk test (see Talk Test).
Vigorous intensity: ≥60% HRR/VO2R, ≥77% HRmax, RPE ≥14, ≥6.0 METs — "can't say more than a few words without a breath."

These bands are the numerical backbone of the weekly volume targets (150–300 min moderate or 75–150 min vigorous; see Weekly Aerobic Volume Targets), and they connect each intensity metric covered separately: %HRmax (Percent of Maximal Heart Rate (%HRmax)), %HRR (Heart-Rate Reserve (Karvonen Method)), VO2 reserve (%VO2max and VO2 Reserve (VO2R)), RPE (RPE and the Borg Scales (6–20 and CR10)), and METs (METs (Metabolic Equivalents)).

Key facts

Moderate: 40–59% HRR/VO2R · 64–76% HRmax · RPE 12–13 (6–20) / 5–6 (CR10) · 3.0–5.9 METs.
Vigorous: ≥60% HRR/VO2R · ≥77% HRmax · RPE ≥14 (6–20) / 7–8 (CR10) · ≥6.0 METs.
Light: 30–39% HRR/VO2R · 57–63% HRmax · <3.0 METs.
Talk test: moderate = "talk not sing"; vigorous = "only a few words."
Relative (%HRR/%VO2R) and absolute (METs) metrics don't align exactly.

Connections

Percent of Maximal Heart Rate (%HRmax), Heart-Rate Reserve (Karvonen Method), %VO2max and VO2 Reserve (VO2R) — the relative metrics.
RPE and the Borg Scales (6–20 and CR10) — the perceived-exertion metric.
METs (Metabolic Equivalents) — the absolute metric.
Talk Test — the simplest field gauge.
Weekly Aerobic Volume Targets — uses these bands for the moderate/vigorous targets.

Sources

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ACSM exercise-intensity classification (ACSM's Guidelines for Exercise Testing and Prescription, 11th ed., 2021): moderate 64–76% HRmax / 40–59% HRR / RPE 12–13; vigorous ≥77% HRmax / ≥60% HRR / RPE ≥14; MET bands per Compendium (light <3, moderate 3–5.9, vigorous ≥6).

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