AMRAP With Friends

15 minute AMRAP

Iron Spine

Core under fatigue · Midline Tension · intensity 3 of 5

The workout

As many rounds as possible in 15 minutes of:

Overview

Iron Spine is 16 alternating bird-dogs, 16 reverse lunges, and 30 mountain climbers. The work moves through the midline and the quads instead of sitting on one muscle.

Muscles worked

Energy systems

These are overlapping contributions. This workout is not assigned to one energy system.

  • Glycolytic: Moderate
  • Oxidative: Moderate
  • Neuromuscular: Moderate

Training effect

Immediate demand

15 minutes, intensity 3 of 5. Today the limiter is the mountain climbers.

Intended stimulus

The style is built so a trunk position has to survive the moving reps. On this workout that is 16 alternating bird-dogs, 16 reverse lunges, and 30 mountain climbers.

Repeated practice

Repeat the same workout and compare the score. What can change over weeks is how long that pace lasts. One time through does not produce that change.

Body-composition context

Body weight changes with the rest of how you eat and train. This workout is one piece of work on one day.

Expected feel

30 mountain climbers is where the round gets hard. The other movements still have to be finished after it.

Pacing

Move with agonizing precision on the bird-dogs. Do not let the hips wobble.

Keep the later rounds moving at the same size as the early ones. Do not drop the mountain climbers to keep the other sets moving.

The movements

Alternating Bird-Dogs

Reach long, not high. Hyperextending the back to get your leg higher defeats the core stabilization purpose entirely.

What not to do. Lifting the arm and leg above the line of the back, which arches the spine.

Reverse Lunges

Keep your torso completely upright. Leaning forward shifts the load to the lower back and robs the quads of the intended tension.

What not to do. Stepping back too short, which forces the front shin to angle over the toe.

Mountain Climbers

Keep your shoulders stacked directly over your wrists. If you drift backward, you lose leverage and the movement slows down completely.

What not to do. Landing the driving foot short, so the knee never gets near the chest.

Why these movements

The work moves through the midline and the quads instead of sitting on one muscle.

Scaling

Keep a brace or a hollow position in every round. Drop the moving reps before you drop the position that makes the trunk work.

Alternating Bird-Dogs

  • Shorter range. Lift only as high as you can hold the position without arching the back.
  • Both legs. Drive through both feet instead of one.

Reverse Lunges

  • Hold a support. One hand on a wall or chair for balance. The legs still do the work.
  • Shorter range. Drop only as far as you can stand back up from without pushing off your hands.

Mountain Climbers

  • Low impact. Keep one foot down throughout — march the pattern instead of running it.
  • Slower cadence. Same movement, fewer beats per minute. Cadence is the dial, not the shape.

Mistakes and who it is for

  • Opening the alternating bird-dogs at a sprint makes the mountain climbers the piece that falls apart.
  • Resting until you feel fresh between movements removes the point of keeping them in one round.
  • Spending the first minutes hard leaves the later rounds as a different, slower workout.

Suited to someone who wants 15 minutes through Alternating Bird-Dogs, Reverse Lunges, Mountain Climbers.

Scoring and progression

Work through the movements in the order listed, then start the next round. Your score is the number of complete rounds plus any reps of the round you were partway through when the clock hit zero — written as rounds plus reps, so seven full rounds and twelve reps is7+12.

Progression is repeating this workout and comparing that score. The page does not promise a change from one time through.

Related workouts

Run it with friends

Iron Spine runs on a shared countdown: share a rally link, everyone gets the same 15-minute clock, and the leaderboard updates as people log rounds.

Start this workoutMore 15 minute AMRAPs