The 8 Best Ways to Build an Underdeveloped Core

Have you spent hours doing crunches and sit-ups without achieving a strong, stable core? Do you want to build a sound foundation that improves your posture, stabilizes heavy compound lifts, and gives you a chiseled-looking midsection? 

Popular abdominal exercises often focus on the rectus abdominus, the “six-pack” section of the abs located on the front of your stomach. But these muscles are only one part of your core. Your abdominal training must target all the different core muscles that span from the top of your ribcage to your hips.

We’ve collated the best ways to build underdeveloped or weak core muscles. We’ll cover the best exercises, rep and set ranges, and intensities to strengthen weak core muscles.

The 8 Best Ways to Build an Underdeveloped Core

Underdeveloped core muscles occur when the muscles at the center of your body are smaller or weaker than they should be. 

Your core comprises more than just the muscles on the front of your stomach, known as the rectus abdominus and often referred to as the abs. The core muscles include the pelvis, lower back, and hips, which connect to your glutes.

Your core muscles stabilize your trunk and spine, which is crucial for preventing pain and injury throughout your entire body. 

You may struggle to maintain an upright posture when your core is weak. You will also be at risk of developing an anterior pelvic tilt (arched lower back), lower back pain, difficulty standing up without assistance, and weakness in functional movements like throwing or jumping.

You can strengthen weak core muscles with varied exercises that target the entire core, an upright posture, and heavy compound lifts that work every muscle in your trunk. 

The 8 Best Ways to Strengthen a Weak Core

1. Train the entire core 
2. Challenge yourself with hanging exercises
3. Brace your abs in and out of the gym
4. Don’t arch your back when training your core
5. Prioritize full-body compound exercises 
6. Use anti-core strengthening exercises
7. Don’t forget about your glutes
8. Accept that visible abs are mainly due to genetics

1. Train the entire core

Don’t focus solely on the most visible section of the core – the rectus abdominus. To build a stronger core, target it from every angle and include all the different core muscles. Your core consists of four main muscles, all essential to stabilizing your trunk. 

Image Source: Repke Fitness

The transverse abdominus (TA) is the deepest core layer and wraps around your spine to prevent unwanted movement of the lumbar spine and pelvis. Your TA helps maintain a neutral spine during heavy lifts like squats, stabilize functional movements like jumping and running, and create a flatter, firmer stomach.  Great exercises for the TA include planks, bird dogs, leg raises, and glute bridges.

The rectus abdominus (RA) is the well-known “six” pack located on top of the transverse abdominus. Your RA is in charge of spinal flexion and posterior pelvic tilt (tucking the buttocks). It also controls movement between your pelvis and ribcage when flexed. 

The RA muscles grow outward in rounded “bumps,” poking through the skin to create the appearance of a six-pack. You can target the RA muscles with exercises like weighted machine crunches and V-sit-ups. 

The external obliques are on either side of your rectus abdominus, spanning from the rib cage to the pubic bone. The external obliques pull your chest towards your hip muscles and support horizontal twisting, with your right oblique contracting to twist to the left and the left oblique contracting to rotate to the right.

The internal obliques are directly underneath the external obliques but function oppositely. The right internal obliques help you twist to the right, and the left internal obliques contract to rotate to the left. Exercises like v-sit Russian twists target both layers of your obliques.

Rather than doing thousands of crunches to build a bulkier rectus abdominus, use a combination of these exercises to hit your core from every angle. 

2. Challenge yourself with hanging exercises

If you’re already a pro at planks, crunches, bird dogs, and Russian twists, level up with hanging or weighted exercises. Hanging exercises are an advanced method for building core strength, strengthening your shoulders and lats, and targeting your hips and glutes for an all-around body blaster. 

Start practicing an active “dead hang” from a pull-up bar, bracing your abdominals, tucking your hips slightly, and pulling your shoulder blades and traps down from your ears. Once you can hold this for a few sets of 30 seconds, experiment with knee and leg raises or toes-to-bar to demolish your entire core.

3. Brace your abs in and out of the gym

Strengthening weak core muscles requires more than a few sets of dedicated ab work each week. It often involves changing habitual biomechanical patterns that cause weak core muscles. 

Think about drawing your navel towards your spine when sitting or standing, and squeeze your glutes to avoid a lower back arch.

Good posture is critical both in and out of the gym to improve core stability and address weak core strength.

4. Don’t arch your back when training your core

Most people tend to arch their lumbar spine during supine ab exercises like crunches and leg raises, creating a space between their lower back and the floor. Doing so causes the core muscles to disengage, so you use your hip flexors rather than your core.

Actively press your lower back into the ground when doing lying ab exercises. Tuck your pelvis slightly during standing or hanging core work to engage the pelvic floor and keep the spine in a neutral position.

5. Prioritize full-body compound exercises

You can’t build strong core muscles with endless crunches alone. Heavy compound lifts like deadlifts, squats, and lunges are among the best ways to strengthen your core. 

The Renaissance Periodization suggests you can maintain or build ab strength and muscle mass with no direct abdominal work. However, if you have ambitious abdominal growth goals, you may need around six to nine sets of dedicated abdominal training per week split into two sessions. 

6. Use anti-core strengthening exercises

Anti-core exercises strengthen your abdominals by preventing unwanted movement of the hips and spine. Your core muscles’ main job is to stabilize the spine and joints by resisting movement. 

You should include four main types of anti-core stability exercises to build a healthy, stable core.

• Anti-extension exercises keep the spine static during compound lifts like overhead presses. Planks and ab roll-outs are great examples of anti-extension core exercises. See our guide on the muscles worked by planks for additional info.
• Anti-rotation exercises build stability in your hips and torso when twisting the upper body. Anti-rotational strength is crucial for athletes to transfer energy from their lower to upper body safely. Bird dogs and Pallof presses are fantastic for improving anti-rotational core strength.
• Anti-lateral flexion strength prevents unwanted flexion to the sides and promotes lateral core stability. Side planks and single-arm farmers’ carries build strength in your obliques for anti-lateral core strength.
• Anti-flexion core exercises strengthen the core muscles in your posterior chain. They won’t give you a chiseled six-pack, but they are crucial for safely performing deadlifts and squats. Back extensions, glute bridges, and dead bugs help improve your anti-flexion core strength.

7. Don’t forget about your glutes

Your glutes are a large, strong muscle group that connects your legs to your hips and trunk. Modern sedentary lifestyles can cause underdeveloped glutes, which strain the lower back and make it harder to maintain an upright posture. Strengthening your glutes will improve your hip stability and contribute to a stronger core. 

8. Accept that visible abs are mainly due to genetics

Don’t focus so much on getting protruding six-pack abs that you forget that the primary purpose of a strong core is functionality, not aesthetics. Only training the visible section of your abs can exacerbate muscular imbalances and an underdeveloped posterior core. 

The levels of body fat some athletes, especially women, need to achieve to have visible abs are not necessarily healthy and certainly don’t indicate more strength or functional fitness. Some people need to get their body fat below 15% to see their abdominals, which can be a risk factor for hypothalamic amenorrhea (HA) or loss of menstrual period. 

HA can be a severe medical condition that increases the risk of low bone mineral density (BMD), eating disorders, and low energy availability (LEA). Remember that fitness is more about how you feel and perform than your appearance.

The 18 Best Exercises to Improve Core Strength

1. Hanging Knee Raises
2. Machine Crunches
3. Cable Bosu Crunches
4. Ab Rollouts 
5. Planks
6. V Sit Ups
7. Slider Pikes
8. RKC Planks
9. Bird Dog/Quadruped Hip Extensions
10. Reverse Planks
11. Side Plank with Hip Dips
12. Stability Ball Rollouts
13. Glute Bridges
14. Unilateral Farmers Carries (functional carry-over)
15. Half-Kneeling Anti-Rotation Pallof Band Presses
16. Resistance Band Clamshells
17. Wipers
18. Russian Twists

Some of these exercises are advanced, so only choose those you feel confident performing correctly. Be meticulous with your technique, and focus on squeezing your belly button towards your spine during every rep. Incorporate a few of these exercises into your weekly ab training plan to start seeing stronger, fuller abdominals. 

What Is an Underdeveloped Core?

Underdeveloped core muscles occur when your abdominal muscles are weak or inactive. Core muscle weakness can be both a result and cause of poor posture, lower back, pelvis, and hip pain, and instability during compound lifts or activities of daily living.

You can strengthen a weak core by improving your technique during abdominal exercises, including varied core exercises to target all four core muscles and activating your abdominals in and out of the gym.

Core Muscle FAQs

How often should you train your core?

You don’t need any specific core training if your goal is to maintain your core muscle strength. To build bigger abs or address severely weak core muscles, aim for six to nine sets of direct core work per week, split into two separate sessions. 

How much intensity does core training need?

You can do core training with added weight, resistance from gravity, or your body weight. Bodyweight exercises are likely enough if you want to strengthen a weak core and improve poor posture.

However, if you’re chasing visible abdominal muscles, there are two things to consider: how lean you are and the depth and thickness of the rectus abdominus (RA). If you have low body fat but still have poor abdominal muscle definition, adding weighted exercises like machine crunches or cable Bosu crunches will help them show through the skin and fat tissue.

This video from Athlean-X provides a helpful overview of how to dial in your nutrition and training if visible abs are your goal.

What’s the optimal rep range for core muscle exercises?

The core muscles have a higher ratio of slow-twitch to fast-twitch muscle fibers, but you should still train them in a range of rep schemes for optimal results. Aim to do about half of your ab training with higher reps (15-20+) and lower weights and the other half in the 8-12 rep range with higher intensity or added resistance.

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About Emma Lennon

Emma is a Health Science graduate, qualified personal trainer, and writer. She has over ten years of experience in the health, community development, and communications sectors. She is passionate about making reputable information about health, fitness, and resistance training accessible to all.

Emma loves building her own functional strength and fitness outside of work with various training styles, from weightlifting to calisthenics, yoga, and dancing. She advocates for the powerful potential of exercise to improve physical, mental, and emotional health and well-being.