Serratus Posterior Inferior: Strengthening, Benefits, and Exercises

How to strengthen the serratus posterior inferior muscle?

Strengthening the serratus posterior inferior muscle is primarily achieved through targeted breathing exercises that emphasize forceful exhalation, combined with core stability movements that demand active rib depression and lumbo-pelvic control.

Understanding the Serratus Posterior Inferior

The serratus posterior inferior (SPI) is a small, deep muscle located in the lower back, often overlooked in conventional strength training programs. Understanding its anatomy and function is crucial for effective engagement.

• Anatomy: The SPI originates from the spinous processes of the T11 to L2 vertebrae and inserts onto the inferior borders of the lower four ribs (ribs 9-12). It lies deep to the latissimus dorsi and is part of the thoracolumbar musculature. Its innervation comes from the lower intercostal nerves.
• Function: While its exact primary role has been debated, the most accepted function of the serratus posterior inferior is to depress the lower ribs, primarily during forced exhalation. This action assists in expelling air from the lungs more completely. It also contributes to the stabilization of the thoracolumbar fascia and may play a minor role in trunk extension and rotation, though its contribution to these movements is less significant than larger, more superficial muscles.
• Importance: Due to its attachments and role in rib depression, the SPI contributes to the stability of the lower thoracic and lumbar spine. Efficient function of this muscle can support proper breathing mechanics, enhance core bracing, and potentially aid in maintaining spinal integrity during various movements.

Why Focus on the Serratus Posterior Inferior?

While not a prime mover for large, powerful actions, the serratus posterior inferior offers several benefits when properly engaged:

• Improved Respiratory Efficiency: By aiding in forceful exhalation, it supports more complete lung emptying, which can be beneficial for athletes or individuals with certain respiratory conditions.
• Enhanced Core Stability: Its role in depressing the lower ribs contributes to a more stable trunk, particularly in conjunction with the diaphragm and abdominal muscles for intra-abdominal pressure regulation. This stability is vital for power transfer and injury prevention.
• Lumbar Spine Support: As part of the deep spinal musculature, it contributes to the overall stability of the lower back, potentially reducing strain during movements that involve trunk extension or rotation.
• Postural Awareness: Conscious engagement of the SPI can improve proprioception around the lower ribs and spine, fostering better postural habits.

Exercises for the Serratus Posterior Inferior

Directly isolating the serratus posterior inferior is challenging due to its deep location and subtle action. The most effective approach is to incorporate exercises that emphasize its primary function: active depression of the lower ribs during controlled, forced exhalation, often integrated with core stability exercises.

1. Diaphragmatic Breathing with Forced Exhalation

   • Execution: Lie on your back with knees bent and feet flat on the floor. Place one hand on your chest and the other on your abdomen. Inhale deeply through your nose, allowing your abdomen to rise. Exhale slowly and completely through pursed lips, actively pressing your lower ribs down and drawing your navel towards your spine, expelling all air. You should feel the muscles around your lower back and sides engage as your ribs depress.
   • Cues: "Squeeze all the air out," "make your exhale longer than your inhale," "feel your lower ribs pull down."

2. Dead Bug (with Exhalation Focus)

   • Execution: Lie on your back with knees bent at 90 degrees directly over your hips, and arms extended towards the ceiling. Ensure your lower back is pressed into the floor throughout the movement. As you slowly lower one arm overhead and the opposite leg towards the floor, simultaneously perform a long, forceful exhalation, actively depressing your lower ribs and maintaining lumbar contact. Inhale as you return to the starting position.
   • Cues: "Breathe out completely as you extend," "keep your low back glued to the floor," "feel your core brace."

3. Bird-Dog (with Rib Depression)

   • Execution: Start on all fours (quadruped position) with hands under shoulders and knees under hips. Maintain a neutral spine. As you extend one arm forward and the opposite leg backward, focus on maintaining a stable torso and actively depressing your lower ribs on the side of the extending leg/arm. Perform a controlled exhale as you extend. Avoid arching your lower back.
   • Cues: "Maintain a flat back," "brace your core," "actively pull your lower ribs down as you exhale."

4. Plank (with Exhalation Focus)

   • Execution: Assume a standard forearm plank position, ensuring your body forms a straight line from head to heels. While holding the plank, focus on deep, controlled inhalations and long, forceful exhalations. During each exhale, actively pull your navel towards your spine and feel your lower ribs depress, enhancing core engagement.
   • Cues: "Keep your body rigid," "breathe deep into your belly," "squeeze all the air out on exhale."

5. Side Plank with Rib Control

   • Execution: Lie on your side, propped up on your forearm with your elbow directly under your shoulder. Stack your feet or place the top foot in front for more stability. Lift your hips off the floor, forming a straight line. Focus on engaging your obliques and actively pulling your lower ribs up and in, preventing them from flaring. Integrate deep, controlled breathing with forceful exhalations.
   • Cues: "Lift your hips high," "don't let your ribs flare out," "breathe into your side."

Integrating SPI Training into Your Routine

Given the subtle nature of the serratus posterior inferior, it's best integrated through mindful practice rather than heavy lifting.

• Warm-up: Incorporate diaphragmatic breathing with forced exhalation as part of your warm-up routine to activate core muscles and improve respiratory mechanics.
• Core Workouts: Include 2-3 of the suggested exercises in your core training sessions, focusing on quality of movement and breath control over quantity. Aim for 2-3 sets of 8-12 repetitions or 30-60 second holds.
• Mindful Movement: Apply the principle of forceful exhalation and rib depression to other compound exercises, such as bracing during squats, deadlifts, or overhead presses. This helps integrate the SPI's function into more complex movements.
• Daily Practice: Breathing exercises can be practiced daily for a few minutes to improve respiratory efficiency and core awareness.

Considerations and Precautions

• Subtlety is Key: The action of the SPI is subtle. Do not expect large, visible muscle contractions. Focus on the feeling of rib depression and lower back stabilization.
• Prioritize Breathing: The primary mechanism for strengthening the SPI is proper breathing mechanics. Ensure you are performing full, forced exhalations.
• Listen to Your Body: If you experience any pain, especially in the lower back, stop the exercise and reassess your form.
• Holistic Approach: SPI strengthening should be part of a balanced fitness routine that includes overall core strength, spinal mobility, and proper breathing patterns. It's not a standalone solution for complex back pain or respiratory issues.
• Professional Guidance: If you have chronic lower back pain, respiratory difficulties, or are unsure about proper technique, consult with a qualified physical therapist, kinesiologist, or certified strength and conditioning specialist.

Conclusion

While often overshadowed by larger, more visible muscles, the serratus posterior inferior plays a valuable, albeit subtle, role in respiratory mechanics, core stability, and lower back support. Direct strengthening is best achieved through specific breathing exercises that emphasize forceful exhalation and core stability movements that demand active rib depression. By mindfully integrating these exercises into your routine, you can enhance your foundational core strength, improve breathing efficiency, and contribute to overall spinal health.