Trunk strength often gets pushed to the sidelines in many training programmes, with most of the spotlight going to leg strength, speed, and endurance. But here’s something interesting: recent research on collegiate athletes found that trunk muscle mass actually has a stronger link to overall strength than you might expect, sometimes even more so than leg muscles.
If you’re studying a personal trainer course, understanding the role of trunk strength is crucial. It not only enhances client performance but also improves stability during heavy training sessions and reduces the risk of injury. A well-developed trunk supports movement efficiency, making a significant impact on both everyday function and athletic performance.
So, let’s take a closer look at why trunk strength really matters and share some practical tips on how to help your clients build it effectively.
Learning About Trunk Strength in a PT Course?
Trunk strength is about way more than just strong abs; it involves a group of muscles working together to keep clients and athletes balanced, stable, and powerful. If you’re studying a PT course, you’ll know that core training goes beyond just sit-ups. It requires targeting a variety of muscles, each with its own role to play:
- Rectus Abdominis (front abs) – These are the muscles you see in a six-pack. They help flex the spine, like when bending forward or performing crunch-like movements.
- Obliques (side abs) – These muscles help with rotation and side-bending movements, crucial for activities that involve twisting or turning quickly, such as tennis or football.
- Transverse Abdominis (deep stabiliser) – Acting as a natural corset, these deep muscles stabilise the spine and core during movement, providing a solid base for performance.
- Erector Spinae (lower back) – These muscles run along the spine and keep us upright. They’re vital for back extension, especially in activities like weightlifting or sprinting.
- Multifidus (deep spinal stabilisers) – These are small, deep muscles along the spine that provide stability and help prevent injury by supporting spinal alignment during quick, dynamic movements.
- Hip Flexors and Glutes – Although not always considered part of the core, these muscles help control hip movement and support the pelvis, making them essential for power transfer between the lower and upper body.
A solid understanding of these muscles is key to any PT course and will help you design training programmes that build true trunk strength. Now that we’ve covered the basics, let’s look at how you can effectively strengthen these muscles in your clients.
Why Trunk Strength is so Important
Building a strong trunk isn’t just about getting a six-pack and looking good; it’s actually essential for performance, preventing injuries, and boosting overall ability. Here’s why:
Effective Power Transfer
Think of the trunk as the main link between your upper and lower body. When a ball is kicked, a racket is swung, or a punch is thrown, the trunk helps efficiently transfer energy between the legs and the arms. If the trunk is weak, this transfer isn’t smooth, leading to a loss of power and performance well below a client’s potential.
If you’re studying a personal trainer course, understanding this concept is key. A strong trunk ensures that energy moves efficiently through the body, improving movement quality, strength, and overall performance. In simple terms, if the core is shaky, the power doesn’t flow smoothly.
Greater Stability & Better Balance
During many activities, we constantly shift direction, reacting to various things such as opponents in sports, or adjusting balance quickly. A robust trunk helps stay stable during these rapid movements. This improved balance means fewer stumbles, quicker reactions, and ultimately, fewer injuries from awkward movements or sudden changes in direction.
Reduced Risk of Injury
Weak trunk muscles can put extra stress on other areas of the body, especially the lower back, hips, and knees. If the core isn’t strong enough to stabilise the body, these other areas pick up the slack and can get overloaded. This increases the chance of common injuries, from pulled muscles to lower back pain. Strong trunk muscles create a protective barrier, helping clients stay injury-free longer.
Enhanced Performance in Sport-Specific Movements
Every activity has unique demands and surprisingly, the trunk muscles are crucial in most of them. Whether it’s generating rotational power for a powerful tennis serve or golf swing, providing bracing strength in rugby tackles and scrums, or maintaining impeccable balance in gymnastics routines, a strong trunk helps us perform at our absolute best.
If you’re taking a personal trainer course, understanding how to develop trunk strength is essential for designing effective training programmes. By appreciating why trunk strength matters so much, we can better support our clients. So, let’s explore how to effectively train trunk strength and incorporate it into your athletes’ routines.
How to Assess Trunk Strength
If you want to improve trunk strength, first you need to know exactly how strong your already are. But how do you measure something like trunk strength accurately? Here’s a brief look at some practical ways to do exactly that.
Checking Strength with an Isokinetic Dynamometer
First off, there’s the fancy option: an isokinetic dynamometer. These machines are typically found in research labs and sports performance centres and they’re fantastic for accurately measuring how much force athletes can generate during trunk flexion (bending forwards) and extension (straightening up). They provide detailed feedback on muscle performance, helping pinpoint exactly where athletes need improvement.
Core Endurance Tests (No Fancy Machines Required!)
Don’t worry if you haven’t got high-tech equipment, a simple core endurance test can still give you valuable insights. Exercises like plank holds or trunk extension holds (like a “superman” hold) can measure how long athletes maintain correct form, revealing endurance and stability levels. Longer hold times typically suggest better trunk endurance, which is essential in most sports.
Rotational and Anti-Rotation Strength Tests
For activities that involve rotation (like tennis or golf) or resisting external forces (like rugby or martial arts), it’s important to assess these specific types of trunk strength. Medicine ball throws or cable rotational exercises can show you how powerful an client’s rotational movements are. Anti-rotation tests, like the Pallof press hold, show how well an athlete’s trunk muscles can resist unwanted twisting, crucial for injury prevention.
Regular Check-Ins Are Essential
Testing trunk strength isn’t just something to do once and forget. Regular assessments let you track improvements, ensuring your training programmes are working effectively. It also helps clients see their progress, keeping motivation levels high. Regular testing allows you to adapt training programmes, keeping clients on the right track towards better strength, stability, and performance.
In our personal training courses, you’ll learn how to assess trunk strength for designing effective programmes. With these simple assessment methods, you’re well-equipped to understand and boost the trunk strength of any client you train.
Best Training Methods to Build Trunk Strength
Building trunk strength requires a combination of traditional strength training, stability-focused exercises, and sport-specific movements.
1. Strength-Based Trunk Exercises
These exercises build raw strength and support power transfer:
- Deadlifts – Develop posterior chain strength, engaging the core under heavy loads.
- Squats (Front & Back) – Require strong trunk engagement to maintain posture.
- Overhead Presses – Strengthen the core’s ability to stabilise under vertical load.
2. Stability & Anti-Rotation Exercises
These exercises improve the trunk’s ability to resist unwanted movement, crucial for injury prevention:
- Pallof Press & Holds – Builds anti-rotation control.
- Side Planks with Reach-Throughs – Enhances lateral core stability.
- Bird Dogs & Dead Bugs – Develops core control and spinal stability.
3. Dynamic & Sport-Specific Drills
For athletes, training must mimic real-world movement patterns:
- Rotational Medicine Ball Throws – Trains explosive rotational power.
- Cable Woodchoppers – Strengthens diagonal movement patterns.
- Sledgehammer Slams – Develops full-body trunk engagement in high-force actions.
3. Dynamic & Sport-Specific Drills
For athletes, training must mimic real-world movement patterns:
Common Errors when Training the Trunk
Training the trunk properly can make a huge difference in performance, but it’s easy to fall into some common traps that can limit progress. Watch out for these mistakes as they could be the reason their core training isn’t delivering the results they need.
Crunches and Sit-Ups Aren’t Enough
A lot of people still believe that endless crunches and sit-ups are the key to a strong core. But here’s the thing: those exercises mainly focus on spinal flexion, basically bending forwards. This is only one small part of what the trunk actually does. Most activities require the trunk to resist movement, rotate with power, and stabilise under load.
In personal trainer courses, trainers learn that core training should go beyond crunches to include stability, anti-rotation, and functional strength exercises. If training is all about crunches, they’re missing out on essential stability and rotational strength.
Forgetting About the Posterior Chain
It’s easy to focus on the front of the body, especially when clients can see their abs in the mirror. But the lower back, glutes and deep spinal muscles (the posterior chain) play just as big a role in trunk strength. If these muscles are weak, it can create serious imbalances, leading to poor movement mechanics and a higher risk of injury. A well-rounded trunk training plan needs to include exercises that strengthen the back as much as the front.
No Progression = No Gains
You wouldn’t design your clients programme and only train their squats or deadlifts without progressively adding weight or reps, so why treat core training any differently? Too often, people stick to the same old core exercises with the same resistance and expect better results. Just like any other strength work, trunk training needs progressive overload, adding weight, increasing reps, extending time under tension, or making the movements more challenging to keep developing strength.
Training in Only One Direction
The body does not move in just one direction, so core training shouldn’t either. A strong trunk isn’t just about flexing forwards, it’s about resisting movement, rotating powerfully, and stabilising under different forces. Training should include movements in multiple planes: forward and backward (sagittal plane), side-to-side (frontal plane), and rotational (transverse plane). Failing to train across all these movements means missing out on strength that translates to real-world power and performance.
Programming Trunk Strength for Athletes
Here’s some basic trunk programming ideas to consider:
Training Frequency: 2–3 dedicated trunk sessions per week, alongside full-body training.
Periodisation: Adjust training based on competition season (e.g., stability in pre-season, power in peak season).
Exercise Variety: Include strength, stability, and dynamic drills tailored to the athlete’s sport.
Sample Trunk Strength Workout
Warm-up:
- Dead Bug (3×10 each side)
- Pallof Press Hold (3×20 sec)
Strength Work:
- Front Squat (4×6)
- Deadlift (4×6)
Stability & Rotational Work:
- Side Plank with Reach-Through (3×10 each side)
- Cable Woodchopper (3×12 each side)
- Rotational Med Ball Throw (3×8)
This approach includes a balance of development for strength, control, and sport-specific power.
Wrapping it Up
Trunk strength isn’t just about doing a few core exercises at the end of a workout, it’s a fundamental part of training and performance. Whether a client is sprinting, jumping, changing direction, or playing sport and bracing against an opponent, their trunk is working hard to transfer power, maintain stability, and protect against injury.
In our personal training courses, trainers learn that developing trunk strength is essential for improving overall performance and reducing injury risk. Recent research has made it clear: a strong trunk is closely linked to muscle mass and overall strength, making it a key area to focus on in training. Yet, too often, it’s overlooked or trained in a way that doesn’t fully prepare clients for the demands of their training.
Making trunk training a priority in strength and conditioning programmes isn’t just a good idea, it’s an essential part. By incorporating a mix of strength, stability, and rotational exercises, you can help clients build a trunk that supports their movement, enhances their power, and keeps them performing at their best, session after session.
Reference
Cataldi, D., Bennett, J. P., Quon, B. K., Leong, L., Kelly, T. L., Binder, A. M., Evans, W. J., Prado, C. M., Heymsfield, S. B., & Shepherd, J. A. (2025). Association of body composition measures to muscle strength using DXA, D3Cr, and BIA in collegiate athletes. Scientific Reports, 15(5839).
Click here to review the full research article.
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