Why Your Bicep Curls Might Be Holding You Back

Bicep curls are one of the most common exercises performed in the gym. It looks simple, and all variations of the curl include elbow flexion as that is the primary role of the biceps brachii. This exercise seems simple, and it should be. However, there are many common mistakes that gymgoers or even athletes make.

Hence, we will look at some of the common mistakes and how to address those mistakes to be more efficient in the exercise and grow bigger biceps. The curl looks like it should be foolproof — a weight, an arm, a bend — but the details of how you move through each rep determine whether your biceps actually grow or whether your lower back and forearms do all the work instead.

Before we get to the mistakes, it helps to understand what is happening mechanically. The bicep curl seems to be easy off the start of the rep from the bottom but gets harder and harder as elbow flexion reaches 90 degrees. The rep then gets easy at the top of the curl. Hence, the most difficult part of the curl is actually mid-way through the repetition, and there is a biomechanical explanation for this.

When elbow flexion is at 90 degrees, the weight of the barbell or dumbbell is the furthest away from the elbow, hence, the moment arm is at its highest when the elbow is at 90 degrees. Therefore, it is very common for the body to self-organize and find ways to compensate in order to get the weight up, especially when it begins to fatigue mid-set. Those compensations are exactly where the mistakes below come from.

Mistake 1: Swinging with the Lower Back

We have all seen or done this before in the gym. Guys swinging the weight up and down while performing their curls, trying to move as much weight as possible. However, this increases your risk of injury even though you are able to move more weight. Moreover, the tension is not necessarily going to the biceps since you are using your lower back to facilitate the movement.

You may be doing this subconsciously with a very subtle swing — so subtle that you do not even notice it. Hence, some signs include lower back tightness or pain after the set, or you could try leaning against the wall with the weight you normally use. If the exercise with the same weight against the wall feels significantly harder, you definitely are using your lower back to facilitate the movement during an actual bicep curl exercise.

If this is you, lower the weight and maintain a more upright posture, so as to reduce injury and increase tension in the biceps brachii for more bicep growth. The ego lift of a heavier swinging curl grows your lower back’s tolerance for abuse — not your arms. Keep the movement strict and the weight honest, and your biceps will finally get the stimulus they need.

Mistake 2: Cutting the Range of Motion Short at the Bottom

You have all heard this before, told to you by someone or even seen it yourself. People doing partial reps in the gym cutting the bottom range short to not allow the tension to leave the muscle when the joint is fully lengthened. The logic sounds reasonable — keep constant tension on the muscle — but the research tells a different story.

A study conducted on the preacher curls divided subjects into Group A and B. Group A performed only the bottom half of the rep while Group B performed only the top half of the rep. What they found was that biceps growth was greater for Group A compared to B by a significant amount. Hence, it is important to prevent cutting your range of motion short, especially at the bottom of the rep, for every exercise.

What you can do to ensure that you have fully extended the elbow is to slightly flex the triceps at the bottom of the rep before initiating the next. That will get you in the right ballpark. The lengthened portion of the rep — where the muscle is stretched under load — is where much of the growth stimulus lives, so the full range is not optional, it is essential.

Mistake 3: Curling the Wrist

More often than not, you may feel forearm fatigue faster than your biceps while performing the bicep curls. One of the roles of the forearm is to perform wrist flexion. Hence, people subconsciously perform wrist flexion as they perform the bicep curl, leading to quicker forearm fatigue.

When performing the bicep curls next time, constantly focus on this one cue: maintain a neutral wrist position until it becomes a subconscious behaviour. You do not want to allow the wrist to extend backwards either, as it can put unnecessary strain on the forearm flexors as well. Hence, make sure to maintain a neutral wrist position throughout the lift.

Think of your wrist as simply a hook connecting your forearm to the bar. When it stays neutral — neither flexed nor extended — the biceps do the bending work they are meant to do, and your forearms stop stealing the workout. A little attention to this cue repays you with stronger, bigger biceps and happier elbows.

Put These Fixes Into Practice

To recap: keep your torso still and upright so your biceps do the work, take every rep through the full range — especially the stretched bottom half — and hold a neutral wrist from start to finish. These three fixes will transform your curls from a mediocre movement into a genuine bicep builder.

Start with a lighter weight than you are used to. Strict form with an honest load will produce more bicep growth in eight weeks than a heavy, swinging curl will produce in a year. Master the movement pattern first, then build the weight back up while keeping the quality of every rep.

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