I did hammer curls every day for a week — here are the results

Man doing hammer curls
(Image credit: Shutterstock)

If you’re new to the fitness section of Tom’s Guide, you’ll be thrilled to hear we love nothing more than embracing a fitness challenge, no matter how weird or wonderful it may sound. From doing 100 kettlebell swings a day for a week to 100 dead bugs a day, we really enjoy focusing on taking a deep dive into one particular exercise.

On the agenda this week — hammer curls. 

Similar to a bicep curl, a hammer curl works the bicep muscles. The main difference between a hammer curl and a bicep curl is that the former works the muscles in the upper and lower arm — the biceps and the forearm. Both can be used to build stronger bicep muscles, but people often find they can lift slightly heavier with hammer curls, as more muscles are activated. Read on to find out how to do a hammer curl, and what happened when I did 100 of them a day for a week. 

Remember that what works for me might not be right for you and your body, and if you’re returning to exercise following an injury, or you’re completely new to hammer curls, doing 100 a day isn’t recommended. It’s also a good idea to check your form with a personal trainer before adding weight or reps to the move. Looking for more workout inspiration? Here are the best bicep exercises for increasing muscle in your arms, plus, the exact arm workout Chris Hemsworth used to get in shape to play Thor. 

How to do a hammer curl 

To do a hammer curl, grab a set of dumbbells (check out the best adjustable dumbbells for weightlifting at home here) and stand with your legs hip width apart. Don’t lock your legs out — keep a soft bend in the knee. Hold a dumbbell in each hand with your palms facing in towards your body and your thumbs facing forward. Bend at the elbow and lift the lower arms to pull the weights up to your shoulders. Pause here, then lower the weights back down to your starting position. 

Be sure to keep your abdominal muscles engaged throughout the movement to protect your lower back. 

an illo of a man doing a hammer curl

(Image credit: Shutterstock)

I did 100 hammer curls a day for a week — here’s what happened 

My biceps really felt it

Hammer curls target the biceps brachii, which is responsible for flexing the elbow. As a runner, I don’t tend to spend an awful lot of time in the gym strength training, and when I do, I tend to focus on my lower body. On day one of this challenge, I grabbed a set of 15-pound dumbbells and started curling, doing four sets of 25 reps. After my first set, I really felt this one, and the next day it was a struggle to wash my hair. 

Slow and steady really does win the race

It’s very tempting to rush through this exercise, but keeping the movement slow and controlled is essential. I asked a personal trainer in my local gym to take a look at my form and he reminded me that the move should come from the bicep, and that as I got tired, I was swinging my arms, using the momentum to lift the weight. He recommended I decreased the weight and worked on perfecting my form. 

Taking your time on the curl, and then straightening the arm keeps the muscle engaged for longer, so if in doubt, slow down. 

I had to get my floating elbows under control

Another form mistake the personal trainer pointed out was my ‘floating elbows’. The elbows should stay tucked into the body during this exercise — let them float out to the side, and you’ll be working your shoulders, not your biceps. The personal trainer told me to keep my arms tucked in, and think about moving from the elbow.  

I enjoyed the variety

Like all of my fitness challenges, after a few days, I was bored of the move. Luckily, the hammer curls can be mixed up — on some days I opted to do alternating hammer curls, focusing on one arm at a time. On the last day I did 100 hammer curl power squats for more of a full body workout — after lifting the weights to your shoulders, drop down into a squat. When you stand back up, complete the second half of the curl.  

I’ll be doing more in future

700 hammer curls later, I definitely feel like I got this move down. My hands ached as much as my biceps (a sign I need to work on my grip strength), but I definitely feel more confident hammer curling in future. Of course, my arms look no different — sadly building visible muscle takes longer than a week, but I felt stronger, and that I’d really worked my triceps hard. 

Jane McGuire
Fitness editor

Jane McGuire is Tom's Guide's Fitness editor, which means she looks after everything fitness related - from running gear to yoga mats. An avid runner, Jane has tested and reviewed fitness products for the past five years, so knows what to look for when finding a good running watch or a pair of shorts with pockets big enough for your smartphone. When she's not pounding the pavements, you'll find Jane striding round the Surrey Hills, taking far too many photos of her puppy.