---
slug: "lead-iso"
title: Lead / Iso
depth_tier: entry
side: OFFENSE
category: Run Game
source_id: "OFF-0078"
created: 2026-04-13
updated: 2026-04-19
canonical: https://learningfootball.xyz/terms/lead-iso
---
# Lead / Iso

## Short Definition

A run sending the fullback through the hole first to block the linebacker before the ball carrier follows—isolating the run-fit anchor one-on-one.

## Definition

The lead or iso run sends a fullback through the hole first to block a linebacker before the running back follows. The play is designed to create a one-on-one block between the fullback and the Mike linebacker—removing the defensive run-fit anchor before the ball carrier arrives at the same gap.

The iso attacks the linebacker directly rather than trying to scheme him out of his gap. Zone runs move the point of attack to find a crease; the iso brings the play to the linebacker and expects the fullback to win the block. If the fullback wins, the runner has a clean lane through the Mike's vacated gap. If the linebacker defeats the fullback, the runner has to cut.

The play is foundational to two-back and I-Formation run games. The fullback's presence in the backfield is a standing threat to the linebacker—every play the fullback is on the field, the Mike has to account for the possibility that he is his assignment. This awareness shapes linebacker pre-snap positioning and post-snap reads even on plays that don't run iso.

## Example

"Fullback leads through the A-gap, takes on the Mike linebacker one-on-one. Fullback wins the block—Mike is sealed. Running back follows right behind and gains seven yards before a safety makes the tackle. That's iso: remove the linebacker from the equation and run behind where he was."

## Common Confusion

Lead and Iso are sometimes treated as different plays. Iso (isolation) sends the fullback directly at a linebacker in a one-on-one block to isolate him from help. Lead is a broader term for any run where a lead blocker goes through the hole first. Iso is the specific version where the fullback isolates the Mike linebacker; Lead is the concept. In practice the terms are often interchangeable.

## Related

- power
- inside-zone-iz
- i-formation
- fb
- mike
- rb

---
Source: https://learningfootball.xyz/terms/lead-iso