Why your arms aren’t growing: 5 mistakes you’re probably making

Big, defined arms are the goal for plenty of gym-goers. Yet, despite pumping out rep after rep of bicep curls and tricep pushdowns, you may still be left scratching your head and wondering why your arms just aren’t growing. But, don’t worry.

According to Exercise Scientist, Dr Mike Israetel, you’re not alone, as many people make the same mistakes when it comes to training arms. In his latest YouTube video he breaks down five of the most common arm training errors people make when trying to grow their guns, so you can stop wasting your time and start seeing some real results.

1. You’re being too strict with rep ranges

One of the most common questions people want the answer to is whether high-rep training or low-rep training builds muscle the best. “What that can end up doing is constraining people to one very small rep range, for example 8-12 for biceps and triceps,” says Dr Israetel. In reality, muscle growth can happen across a wide spectrum – anywhere between five to 30 reps. Dr Israetel's advice? Don’t get fixated on specific rep ranges, experiment with what works best for you, and be prepared to switch it up when things get stale.

2. You have a dedicated arm day

Having an ‘arm day’ where you train biceps and triceps together works for many people, but the belief that you have to train them in the same session is a myth, says Dr Israetel. In fact, he points out some potential downsides to doing so: “If your biceps are sufficiently pumped, it actually limits the range of motion on your triceps, which means they’re not getting as much of a high-load stretch,” he says. He also notes that triceps are a larger muscle group and generally take longer to recover than biceps. “So if you’re always trying to train them together, you’ll have to needlessly constrain the amount of effort or volume you do for triceps and needlessly do too much for biceps.”

3. You’re not getting that ‘deep stretch’

Dr Israetel actually says this is a “huge problem” and that “Not nearly enough people are going for a deep enough stretch on their biceps and triceps”. By this, he means that too many lifters aren’t moving their muscles through their full range of motion and, instead, favouring partial reps, which may be hindering muscle and strength gains. He recommends exercises that emphasise the stretch phase of the lift, like lying dumbbell curls for biceps, and skullcrushers for the triceps.

4. Ignoring the forearms

Despite forearms being part of our arms, many of us barely give them a second though, and Dr Israetel says it's a rookie error. “For whatever size your upper arm is, a bigger forearm will almost always make the overall look better,” he says. The good news? You don’t need to go overboard here. Just three to six sets of a forearm exercise, a couple of times a week, is enough to make a noticeable difference.

You’re not training your arms enough

If you’ve only been training your arms once a week consistently for the past few months and haven’t spotted any changes, that might be exactly why – you’re simply not training them enough. “These are small muscles, they do not take one week to recover,” Dr Israetel says. They can handle more frequent sessions than you think. Two times a week minimum is Dr Israetel's recommendation, or three to four times a week – only if you can recover.