We’ve all seen that guy in the gym who boasts he can crank out 30 pull-ups, but when he tries, his form is anything but perfect. You might have scoffed at his sloppy technique, thinking he’s going nowhere fast with those half-reps. But what if he’s actually onto something? Recent research suggests that focusing on the stretch portion of an exercise—yes, even with bad form—can help build muscle almost twice as fast. This might sound counterintuitive, but the science behind it is pretty compelling.
The information you will see below is based on a video shared by Jeremy Ethier and his research behind how you can improve your strength and fitness with bad form. Jeremy Ethier is a kinesiologist and fitness trainer, co-founder of Built With Science. His YouTube channel has over 6.5 million subscribers and he delivers clear information with sound background research.
So let’s explore why targeting the stretch in your training with bad form can accelerate muscle growth, how traditional training methods might be limiting you, and why even “bad form” can sometimes work to your advantage. We’ll also provide actionable techniques you can apply to your routine today to start seeing faster gains.
Table of Contents
The Science Behind Stretch-Based Training
Dr. Milo Wolf, a leading researcher in this emerging field, has been at the forefront of studies that challenge conventional weightlifting wisdom. His research, supported by approximately 10 to 12 studies, shows that focusing on the stretch portion of an exercise can lead to around double the muscle growth compared to traditional methods. The stretch occurs when a muscle is lengthened under tension, usually at the hardest and most painful part of a lift. For example, in a bench press, this would be when the barbell is closest to your chest; in a squat, it’s when you’re at the bottom of the movement.
But why does the stretch matter so much? When a muscle is lengthened under tension, it experiences higher mechanical stress. This stress stimulates muscle fibres in a way that traditional lifting, which often focuses on the contraction, does not. Moreover, lengthened muscles under load are subject to more microtears, which is a key factor in muscle hypertrophy.
The Surprising Benefits of “Bad Form” for Muscle Growth
We’ve been taught from day one in the gym that proper form is everything. “Don’t cheat,” “Maintain perfect technique,” and “Stick to full range of motion” are often hammered home by trainers and gym-goers alike. But here’s the twist: there’s a growing body of evidence suggesting that bad form—when applied strategically—might actually accelerate muscle growth in certain situations.
Specifically, using partial reps or “bad form” in the stretch position of an exercise could lead to significantly more muscle hypertrophy than performing perfect, full-range reps. This concept flips conventional wisdom on its head, but the research behind it is compelling.
Understanding Good vs. Bad Reps
Let’s break this down. Typically, we think of “bad form” as something that compromises safety and effectiveness. This includes jerky movements, swinging weights, and skipping key phases of an exercise. While these habits can indeed lead to injury or stalled progress when done haphazardly, there’s a unique subset of so-called bad form that can work in your favour.
This subset is partial reps performed in the stretched portion of a movement. Normally, full-range exercises take your muscle through both contraction and extension phases. While full reps are valuable for overall strength and functional fitness, research shows that when it comes to hypertrophy, the stretch phase (the part where the muscle is elongated) plays an outsized role in stimulating growth.
In this context, performing half reps in the stretched position takes advantage of this phase and keeps the muscle under continuous tension where it’s most challenged. Rather than viewing partial reps as a shortcut or a mistake, they can be seen as an opportunity to focus exclusively on the stretch, squeezing more growth out of the hardest part of the movement.
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How Bad Form Works in Practice
A perfect example of beneficial “bad form” can be seen in calf training. Let’s consider the standard standing calf raise. In a full rep, you go from a deep stretch at the bottom of the movement to a full contraction at the top. The bottom portion—where the calves are fully stretched under the weight of your body—creates the most mechanical stress on the muscle fibres. It’s also the most difficult part of the movement.
Studies on calf training have shown that performing only the bottom half of the movement (the stretch phase) resulted in double the growth compared to performing full-range calf raises. The reason? You’re spending more time in the most effective part of the movement for hypertrophy, increasing muscle tension and mechanical stress at a critical point of the rep.
The same logic applies to other muscle groups. For instance, when performing lat pulldowns or rows, the hardest part of the exercise is often the contraction at the top of the movement. However, by focusing solely on the stretch position (the start of the rep when your lats are fully lengthened), you can stimulate more growth by working in that painful, elongated state.
When to Use Bad Form for Better Results
Partial reps in the stretched position are particularly effective for muscle groups and exercises where the end range (the fully contracted position) is the easiest part of the movement. Think about exercises like:
- Lat Pulldowns: Where the hardest part is when your lats are fully stretched at the top.
- Rows: Where the stretch occurs when your arms are fully extended, before you pull the weight towards your body.
- Chest Flies: Where the maximum stretch happens when your arms are out wide, before you bring the weights back to centre.
For these movements, full reps might not provide as much benefit as you think. By skipping the contracted portion and focusing solely on the stretched part of the exercise, you force your muscles to work harder in the area where they are most susceptible to growth.
This technique can also be applied as a finisher to traditional sets. For example, after performing a set of full-range lat pulldowns, you could finish with several partial reps where you only pull the bar halfway down, focusing on the stretch at the top. This allows you to extend the set beyond your normal point of failure, further fatiguing the muscle and promoting more growth.
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Don’t Forget: Bad Form with Caution
Of course, this strategy doesn’t mean you should abandon proper form altogether. Safety and long-term joint health should still be priorities. When applying bad form (in this case, partial reps in the stretch position), make sure you’re doing so with control. It’s crucial not to let your ego push you to use excessive weight that compromises technique entirely. Instead, focus on maintaining control and tension in the target muscle during the stretch.
It’s also important to note that this method is best used for specific exercises where the stretch is key to muscle hypertrophy. In movements like deadlifts, squats, or overhead presses, where full range of motion is essential for joint health and overall strength, partial reps can lead to imbalances and increased risk of injury. Save the bad form for exercises where you know the stretch is the primary driver of growth.
Key Exercises for Stretch-Focused Partial Reps
Here are some exercises that benefit the most from using this stretch-based “bad form” technique:
- Calf Raises: Focus on the bottom half of the movement, staying in the stretched position for as long as possible.
- Lat Pulldowns: Perform partial reps in the top half of the movement, focusing on the stretched lats.
- Rows: Work with half-reps at the beginning of the movement, maintaining tension in the stretched back muscles.
- Chest Flies: Perform partial reps in the bottom, fully stretched position to target the chest muscles more effectively.
By incorporating these “bad form” techniques into your training, you can exploit the muscle-building potential of the stretch phase, leading to faster hypertrophy and improved muscle development.
Common Mistakes That Limit Your Growth
Despite the benefits of focusing on the stretch, many lifters—particularly more advanced athletes—tend to neglect this crucial aspect. Why? It often boils down to two things: ego and pain avoidance.
One of the most common mistakes is stopping short of full depth in exercises like squats or bench presses. Think about it—how many times have you seen someone load up the bar for a squat, only to stop halfway down? Or, how often do you see lifters bench pressing heavy weight but never letting the bar fully reach their chest? These partial reps are often a way to lift heavier loads without fully engaging the muscle in the most challenging part of the movement. But in doing so, they sacrifice the stretch, and in turn, limit their muscle growth.
Another common error is speeding through the stretch portion of a movement. For example, in a bench press, many lifters will pause at the top of the rep to reset but quickly rush through the bottom (stretch) portion where the real growth potential lies. Instead of hurrying through the discomfort, Dr. Wolf suggests doing the opposite: slow down, control the weight in the stretched position, and even pause there briefly before exploding out of it.
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How to Maximise the Stretch for Faster Gains
To really capitalise on the stretch, you need to do two things: (1) lower the weight to allow for full depth and control, and (2) select exercises that place a greater emphasis on the stretch.
For example, in a standard barbell bench press, the depth of your stretch is limited by the bar touching your chest. Switching to dumbbells allows you to move deeper into the stretch, giving your pecs more room to lengthen. If you want to take it even further, a deficit push-up, where you perform the movement on two elevated platforms, will allow you to stretch your chest muscles more than ever before.
Another exercise that highlights the importance of the stretch is the preacher curl for biceps. When compared to an incline curl, the preacher curl places more tension on the biceps in the stretch position at the bottom of the movement. A 2023 study revealed that preacher curls actually resulted in more muscle growth than incline curls, particularly in the lower portion of the biceps.
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Key Stretch-Focused Exercises to Try
Now that you know why the stretch is important, let’s dive into some exercises that are great for targeting this phase:
- Chest: Dumbbell flies, deficit push-ups, and deep dumbbell bench presses.
- Triceps: Overhead extensions and skull crushers.
- Shoulders: Behind-the-body lateral raises with a cable set at wrist height.
- Rear Delts: Reverse cable flies.
- Biceps: Preacher curls and incline curls.
These exercises are designed to challenge your muscles in their stretched position, making them more effective for hypertrophy than exercises that primarily focus on the contraction phase.
Putting It All Together
The stretch-focused training approach is a game changer for muscle growth. By emphasising the stretch portion of your lifts and challenging your muscles in these positions, you can see nearly double the gains compared to traditional lifting methods. It’s not just about how heavy you lift—it’s about how deeply you can stretch your muscles under tension.
What was once dismissed as poor technique is now proving to be an effective strategy for muscle growth when used correctly. By strategically applying partial reps in the stretched position, you can target muscles more effectively, promote faster hypertrophy, and bring lagging areas up to par. This isn’t an excuse to get lazy with your form across the board, but a powerful tool to be added to your muscle-building arsenal. The key is to apply it wisely and in the right context to see real gains from what we used to call “bad form.”
As with any new training technique, it’s important to apply this method with intention. Start by incorporating stretch-focused exercises into your routine, lower the weight to ensure full range of motion, and don’t be afraid to use partial reps when appropriate. By making these small adjustments, you can unlock faster muscle growth and finally bring those stubborn muscles up to par.
Key Takeaways
| Key Insight | Actionable Tip |
|---|---|
| Stretch-focused training leads to faster growth | Emphasise the stretch position in your exercises. |
| Common mistake: avoiding the full stretch | Lower the weight and focus on full range of motion. |
| Bad form can be good when used properly | Use stretch-position half-reps to push past failure. |
| Best exercises for stretch | Choose exercises like dumbbell flies, preacher curls. |
