We've all heard it: to maximize muscle growth, you need to train at long muscle lengths. For biceps, that means prioritizing exercises like incline dumbbell curls, where you get a deep stretch at the bottom. The preacher curl, which challenges the muscle in its shortened position, is often seen as a secondary, "peaking" exercise.
This principle, known as stretch-mediated hypertrophy, is well-supported in traditional strength training. But what happens when we introduce a unique training variable like Blood Flow Restriction (BFR)?
A new 2024 study from the journal Sports Health asks this exact question: when using low-load BFR, does training the biceps at a short vs. long muscle length lead to different growth outcomes?
The answer might surprise you.
The Study: Pitting Short vs. Long Muscle Lengths in BFR Training
Researchers set out to compare regional hypertrophy (growth in different parts of the muscle) in the elbow flexors—your biceps and brachialis—after a period of low-load BFR training.
One group trained the biceps in a shortened position, similar to the top half of a preacher curl. The other group trained in a lengthened position, emphasizing the stretch you'd feel at the bottom of an incline curl.
It's important to note that as the full text of this study is not yet publicly available, our analysis is based on the revealing title published by the researchers.
The Finding: It Was a Tie
The title of the paper says it all: "Similar Regional Hypertrophy of the Elbow Flexor Muscles in Response to Low-Load Training With Vascular Occlusion at Short Versus Long Muscle Lengths."
Let's break that down. When using BFR, both training styles produced similar muscle growth. The group training at a long, stretched position didn't get better results than the group training at a short, contracted position. For the biceps, this means the supposed superiority of the incline curl vanished when BFR was the primary training method.
Why Would BFR Change the Rules?
While the study's discussion isn't available, we can speculate based on what we know about BFR's mechanisms.
Traditional hypertrophy training relies heavily on mechanical tension—lifting heavy weights through a full range of motion. In this model, the stretch at long muscle lengths provides a powerful tension-based signal for growth.
BFR training, on the other hand, operates differently. Its primary driver is immense metabolic stress. By trapping blood in the muscle with a cuff, you create a massive buildup of metabolic byproducts. This metabolic stress is itself a potent anabolic signal, independent of heavy loads or extreme stretch.
It's plausible that the overwhelming metabolic stress created by BFR becomes the dominant signal for hypertrophy, effectively overriding the more subtle benefits of stretch-mediated tension. The "pump" becomes so intense that it doesn't matter as much how you're getting it.
Practical Takeaways for Your Training
This study provides some clear, actionable advice for anyone using BFR for their arms.
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Context is King: This finding applies specifically to low-load BFR training. For your traditional, heavy arm days, the evidence still supports prioritizing exercises that train the biceps at long muscle lengths. Don't throw out your incline curls just yet.
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Freedom of Choice with BFR: When you're doing BFR curls, you can likely choose the variation that feels best for you. If incline curls bother your shoulders, or you simply get a better mind-muscle connection with a standing cable curl or a preacher curl, this study suggests you're not leaving gains on the table.
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Perfect for Pain Management and Volume: BFR is an excellent tool for training around cranky joints or adding extra, low-stress volume. This research gives you the green light to use a variety of curl variations during your BFR sessions without worrying about optimizing muscle length.
The Bottom Line
When it comes to building bigger biceps with BFR, consistency and proper application of the cuffs are likely far more important than your specific exercise selection.
This study by Vendruscolo and colleagues challenges a long-held belief in hypertrophy training, reminding us that the best training method always depends on the context. For heavy lifting, stretch is king. But for BFR, the pump reigns supreme.
Reference:
Vendruscolo, L. da S., Brendon, H., Hevia-Larraín, V., Aihara, A. Y., & de Salles Painelli, V. (2024). Similar Regional Hypertrophy of the Elbow Flexor Muscles in Response to Low-Load Training With Vascular Occlusion at Short Versus Long Muscle Lengths. Sports Health. PMID: 39449136.