The multifidus is a deep muscle running along your spine that most people have never heard of — and that is a problem. Weakness here is linked to chronic low back pain, yet standard crunches and planks barely touch it. Strengthening this muscle requires specific, isolated movements that target its unique role in spinal stability. The step-by-step approach starts with finding the muscle through gentle activation, progresses to bird dogs and side-lying lifts, and finishes with loaded carries and anti-rotation drills.
What Is the Multifidus and Why Does It Matter for Back Pain?
The multifidus is a series of small muscles that run from the sacrum up to the second vertebra in your neck. Each segment connects one vertebra to the one below it. Their job is to provide segmental stability — meaning they keep individual vertebrae from shifting out of place during movement.
Research published in Spine found that people with chronic low back pain have significant atrophy and fatty infiltration in the multifidus compared to pain-free controls. The atrophy is specific. It is not general back weakness. The multifidus loses cross-sectional area and fills with fat, which makes it less able to stabilize the spine.
The problem is that most back exercises do not target this muscle effectively. A 2014 study in the Journal of Orthopaedic & Sports Physical Therapy showed that the multifidus activates at only 10-20% of maximum during crunches and leg raises. You need movements that create small, controlled spinal movements — not big range-of-motion exercises.
How To Strengthen The Multifidus Step By Step: The Activation Phase
Before you load the muscle, you need to find it. Many people cannot voluntarily contract their multifidus. The first step is learning to isolate it.
Lie on your stomach with your arms by your sides. Place your fingertips on either side of your spine at the lower back level, about one inch from the midline. Gently tighten the muscles under your fingers as if you are trying to create a small dimple on each side. Do not use your glutes or hamstrings. The movement should be tiny — your pelvis and ribs should not move at all.
Hold this contraction for 3-5 seconds while breathing normally. Repeat 10 times. Do this once daily for the first week before moving to the next step. Some people report feeling a deep, dull ache during activation. That is normal. Sharp pain is not.
What Is the Bird Dog Exercise and How Does It Target the Multifidus?
The bird dog is the foundational strengthening exercise for the multifidus. It combines contralateral limb movement with spinal stabilization, which forces the multifidus to work to prevent rotation and side-bending.
Start on your hands and knees with your hands directly under your shoulders and knees under your hips. Engage your multifidus by performing the activation contraction from step one. Keeping your spine completely still, extend your right arm forward and your left leg backward simultaneously. The movement should come from the shoulder and hip, not the spine.
Hold the extended position for two seconds, then return to start. Repeat on the opposite side. Do 8-10 reps per side. The key is zero spinal movement. If your lower back arches or your hips rotate, you have lost multifidus engagement and are relying on larger muscles. Drop the leg extension and just do the arm until you can maintain spinal neutrality.
A 2016 EMG study in the Journal of Back and Musculoskeletal Rehabilitation found that the bird dog activates the multifidus at 40-60% of maximum voluntary contraction. That is significantly higher than crunches or planks.
Side-Lying Lifts and Prone Extensions: The Next Progression
Once you can perform bird dogs with perfect form, add side-lying multifidus lifts. Lie on your side with your legs stacked and slightly bent. Place your top hand on your hip. Without moving your pelvis or ribs, lift your top knee about 2-3 inches off the bottom knee. The movement comes entirely from the deep spinal muscles on the side of your lifted leg.
Do 12-15 reps per side. You should feel a deep burning sensation on the side of your lower back, not in your glutes or hip flexors. If you feel it in your glutes, you are using the wrong muscles. Lower the range of motion and go slower.
Prone extensions on a stability ball are the next level. Lie face-down on a ball with your hips centered and hands on the floor in front of you. Lift one arm and the opposite leg simultaneously while keeping your spine neutral. This adds instability that forces the multifidus to work harder to maintain segmental control. Do 6-8 reps per side.
The table below compares activation levels across common exercises based on published EMG data:
| Exercise | Multifidus Activation | Primary Muscles Used |
|---|---|---|
| Crunch | 10-20% | Rectus abdominis |
| Plank | 20-30% | Transversus abdominis, obliques |
| Bird dog | 40-60% | Multifidus, erector spinae |
| Side-lying lift | 50-70% | Multifidus (unilateral) |
| Loaded carry | 60-80% | Multifidus, obliques, glutes |
Loaded Carries and Anti-Rotation Drills: Advanced Multifidus Work
When you can do 3 sets of 12 bird dogs and side-lying lifts without spinal movement, move to loaded carries. The farmer’s carry — walking while holding a heavy weight in one hand — forces the multifidus to resist lateral flexion and rotation. The weight pulls you to one side. Your deep spinal muscles must fire to keep you upright.
Start with a weight you can hold for 30 seconds without your spine bending sideways. Walk 20-30 feet, turn, and walk back. Switch hands. Do 3 sets per side. Do not let your shoulder drop toward the weight. Keep your rib cage level.
Anti-rotation presses are the next step. Stand facing a cable machine or resistance band anchored at chest height. Hold the handle with both hands at your sternum. Push straight out in front of you while resisting the pull that wants to rotate your torso. Hold for 3 seconds, then return. Do 8-10 reps per side. The multifidus must fire continuously to prevent rotation at each spinal segment.
Research from the Journal of Strength and Conditioning Research shows that anti-rotation exercises activate the multifidus at 70-85% of maximum. That is approaching the level needed for hypertrophy in this muscle group.
Common Mistakes That Prevent Multifidus Strengthening
Most people fail to strengthen the multifidus because they use too much range of motion. The multifidus works in millimeters, not inches. When you lift your leg too high during a bird dog, your erector spinae and glutes take over. The multifidus shuts off.
Another mistake is holding your breath. The multifidus works in coordination with the diaphragm and pelvic floor. Holding your breath increases intra-abdominal pressure but reduces the ability of the multifidus to contract independently. Breathe normally throughout each exercise.
Rushing through progressions is the third common error. People want to jump to loaded carries before they can do a proper bird dog. This does not strengthen the multifidus. It strengthens compensation patterns. Stay at each level until you can perform the exercise with zero spinal movement for 3 sets of 12-15 reps.
Avoid exercises that involve spinal flexion under load — like crunches or sit-ups — during the early phase of multifidus training. Flexion loading can aggravate disc issues and does not activate the multifidus effectively anyway.
Frequently Asked Questions
How long does it take to strengthen the multifidus?
Most people see measurable improvement in activation within 2-4 weeks of daily practice. Structural changes like increased muscle size take 8-12 weeks of consistent training.
Can I strengthen the multifidus without equipment?
Yes. The activation phase, bird dogs, and side-lying lifts require no equipment. Loaded carries and anti-rotation drills need weights or bands for progression.
Is the multifidus the same as the core?
No. The core includes the multifidus, transversus abdominis, diaphragm, and pelvic floor. The multifidus is the only one that provides segmental spinal stability between vertebrae.
What does a weak multifidus feel like?
It often feels like a deep, dull ache on one side of the lower back, especially after sitting for long periods or during standing activities like washing dishes.
