Hardest muscles to build: calves, forearms, abs… what to do?

All muscles follow the same logic: enough mechanical tension, repeated often, with decent recovery. Yet two people training identically will not have the same weak points. Genetics affects tendon insertions (a high calf insertion looks less full), muscle belly length, the mix of slow and fast fibers and how easily you can « feel » a muscle working.

There are also far more fixable causes. Calves, forearms and abs already work every day through walking, gripping and posture: they are built for endurance and need higher volume or heavier loads to leave their comfort zone. Other muscles, like the rear delts, get stolen by bigger groups: your back takes over as soon as you pull too heavy.

Before blaming your genes, check four things: the range of motion of your reps, how close you train to failure (keep 0 to 3 reps in reserve), the number of real sets per week and consistency over at least 8 to 12 weeks. A weak point is most often an under-stimulated muscle, not an impossible one.

Calves are the textbook case. The gastrocnemius and soleus absorb your body weight with every step, so a set of 10 reps with a light load teaches them nothing. On top of that, muscle belly length and insertion height vary a lot between people, which is why some seem to have « natural » calves.

What works: full range of motion, with a one-second pause at the bottom (stretch) and a clear contraction at the top. The gastrocnemius is targeted with straight legs (standing calf raises, calf press), the soleus with bent knees (seated calf raises). Aim for 8 to 15 sets per week in total, over 3 sessions if possible, in a 6 to 15 rep range with a load that brings you close to failure.

Avoid the bouncing trap: a controlled tempo, about 2 seconds on the way down, protects the Achilles tendon and makes the set more effective. If you progress in load or reps over 6 to 8 weeks, the muscle is being stimulated, even if the visual change takes time to show.

The forearms include several muscles: the wrist and finger flexors (inner side), the extensors (outer side) and the brachioradialis, clearly visible on top. They work on every pulling movement, but since their job is mostly isometric (holding the bar), they get little stimulation through a full range of motion.

To make them grow, combine three types of work. Wrist curls, with a barbell or dumbbells and forearms resting on a bench, target the flexors. Wrist extensions train the extensors, with lighter loads. Hammer curls and reverse curls hit the brachioradialis and the visible thickness of the arm. Add heavy carries (farmer walks) or dead hangs for grip strength.

Count 6 to 10 direct sets per week over 2 sessions, in 8 to 15 reps for the wrists. Avoid straps on your main pulling sets if grip is your limiter: it will improve along with everything else. Keep straps for your heaviest deadlift sets if you want your back to work at full capacity.

Rear and side delts give shoulder width, but pressing movements mostly load the front head. The result is often well-developed front delts and a flat rear. The rear delt is small, and your back (rhomboids, lats) overpowers it as soon as the load goes up.

For the rear delt, pick light, precise movements: bent-over dumbbell reverse flyes, cable crossover flyes with arms at shoulder height, the reverse pec deck machine, face pulls with the hands spread apart. Think about pushing the elbows outward rather than pulling with your back. For the side delt, favor low-cable lateral raises, which keep tension at the bottom of the movement.

Count 8 to 16 sets per week for each head, in sets of 10 to 20 reps, over 2 to 3 sessions. These muscles recover quickly: you can train them often, as long as you log your loads and do not just swing the dumbbells.

Visible abs depend on two things: muscle size and body fat level. You cannot burn belly fat by doing crunches: fat loss is global and its distribution is genetic. For most people, abs start to show clearly when body fat is low enough, often under 15% in men and around 22% in women, with wide individual variation.

On the training side, treat abs like any other muscle: 6 to 12 sets per week over 2 to 3 sessions. Progressively loaded movements work better than hundreds of reps: high-cable crunches, hanging leg raises with a pelvic tilt, ab wheel rollouts, weighted planks. End each rep by curling the pelvis, otherwise the hip flexors do the work.

For the rest, the key is a mild calorie deficit maintained over time, enough protein and complete leg and back training. Squats, deadlifts and pull-ups already load the abdominal wall heavily: they count toward your volume.

The long head of the triceps makes up the biggest share of its mass. It crosses the shoulder joint, so it is truly stretched when the arm is overhead. Most people under-train it with pushdowns or dips where the arm stays beside the body.

To target it, favor overhead extensions: overhead cable extensions, incline skull crushers, two-handed overhead dumbbell extensions. These put the muscle in a lengthened position, where tension is most effective for growth. Keep 6 to 12 sets per week, in 8 to 15 reps.

For the long head of the biceps, think shoulder stretch: incline bench curls at 45 to 60 degrees, curls with the arm behind the body, or low-cable curls with the arm behind. Add brachialis work (hammer curls, pronated-grip curls), which thickens the arm. As with any small muscle, 8 to 14 sets per week over 2 sessions are enough for many lifters.

The hamstrings are often neglected in favor of the quads. Yet they work at two places: the hip (extension) and the knee (flexion). A single exercise therefore never covers them fully. Combine a hinge movement like the Romanian deadlift or good morning, and a knee flexion like the lying or seated leg curl. The seated leg curl, which puts the muscle in a stretched position, often gives good results. Aim for 8 to 14 sets per week.

The traps have three areas. The upper part responds well to heavy shrugs, with a pause at the top. The middle and lower parts are trained with horizontal pulls, cable rows and Y raises. The upper traps already get a lot of indirect work from your pulling, so 4 to 8 direct sets are usually enough.

The neck is a special case: it is trained with very gentle movements, for example flexions and extensions with light resistance or a band. Stay careful, progress in small steps and stop at the slightest sign of pain. If you have ever had a neck problem, seek professional advice before starting.

A specialization means temporarily raising the volume of a lagging muscle for 6 to 12 weeks, without neglecting the rest. Choose only one or two muscles: aiming for five means specializing in none. Add 3 to 6 sets per week to your current volume, then climb gradually up to roughly 12 to 20 sets, as long as you recover and your performance improves.

Raise frequency before you lengthen sessions: 3 small sets spread over 3 days beat one big session. Place the weak point early in the session, when you are fresh, and keep other muscles at maintenance volume (about 6 to 8 sets per week) so you do not regress.

Also measure what can be measured: loads, reps, arm or calf circumference every 4 weeks, photos under the same conditions. If nothing moves after 8 weeks, change the exercise, range of motion or tempo rather than piling on more volume. Here is a summary to guide you.

A hard-to-build muscle is almost always an under-stimulated muscle: shortened range of motion, too far from failure, too few sets or too little consistency. Genetics sets a ceiling and a pace, not an absence of progress.

Remember four reflexes: pick the exercise that stretches the muscle, train through a full range of motion, aim for 10 to 20 sets per week over 2 to 3 sessions for the weak point, and give it 8 to 12 weeks before judging. Also keep a maintenance volume for the rest of the body.

GymProgress helps you stick to this plan without overselling it: you log weight, reps and RPE for each set, the volume per muscle shows how many sets you really do on your weak point, the rest timer keeps your breaks consistent and records flag each progression. The app is free on Android and on the web, in French, English and Arabic.