Shoulder press: muscles worked, seated or standing

The shoulder press is done seated or standing, with a barbell, dumbbells, kettlebells or a machine. The measurements show that the least stable version works the shoulders hardest, and that it is also the one where you lift the least.

The shoulder press, or military press when done with a barbell, means pushing a load from the shoulders to overhead. Eleven studies compare its variations: seated or standing, barbell or dumbbells, kettlebell, machine, bar in front of or behind the neck, and range of motion. They mostly measure the electrical activity of the muscles (EMG) and the heaviest load lifted for one repetition (1RM). Usage data from the Overload exercise library then shows which variations members log.

Which muscles the shoulder press works

The deltoid, the muscle that caps the shoulder, has three heads: front, side and rear. Saeterbakken and Fimland (2013) measured all three in 15 men, along with the biceps and triceps, on four presses at 80% of their 1RM. The activity of each muscle changed with body position and equipment.

Coratella et al. (2022) added the upper trapezius and the pectoralis major, in eight competitive bodybuilders. The pec worked harder when the bar passed in front of the head. The Overload library files all its shoulder presses under the same primary muscle, the shoulders, with the triceps as secondary. It does not separate the three heads of the deltoid.

Seated or standing

Standing, the deltoid works harder. In Saeterbakken and Fimland (2013), rear deltoid activity was about 25% lower seated than standing with a barbell, and 24% lower with dumbbells. Side deltoid activity was 15% lower seated than standing with dumbbells.

The trunk goes the same way. The same team measured the abs and lower back during the dumbbell press (Saeterbakken and Fimland, 2012). Seated, the rectus abdominis worked about 81% less than standing, and the external oblique 58% less. Lower-back activity did not change between the two positions.

Seated, you lift more. The standing dumbbell press 1RM was about 10% lower than the seated dumbbell press 1RM (Saeterbakken and Fimland, 2013). For the authors, the variation that demands the most stability is both the one where the deltoid works hardest and the one with the lowest 1RM.

Barbell or dumbbells

The standing dumbbell 1RM was about 7% lower than the standing barbell 1RM (Saeterbakken and Fimland, 2013). Dumbbells still ask more of the deltoid: front deltoid activity was about 15% lower with a barbell than with dumbbells standing, and 11% lower seated. The triceps worked about 39% harder with a standing barbell than with dumbbells.

Instability has a limit. Kohler et al. (2010) had 30 trained lifters do the seated press with a barbell and dumbbells, on a bench and then on a Swiss ball. The less stable the condition, the lower the load. The triceps worked hardest with the barbell on the bench and least with dumbbells on the ball. For the authors, these results give little support to training lighter with an unstable load or surface.

Kettlebell or dumbbell

During the press, a dumbbell's center of mass stays in line with the shoulder joint, while a kettlebell's sits behind it. Dicus et al. (2018) compared the two in 21 subjects, with technique and pace controlled. The front deltoid reached 63% of its maximal contraction with the dumbbell, against 58% with the kettlebell.

Busch et al. (2024) tested 28 baseball players with the same 11.34 kg (25 lb) load: dumbbell, kettlebell held normally, and kettlebell held bottom-up. The dumbbell produced more side deltoid activity than the bottom-up kettlebell, and more lower trapezius activity than the regular kettlebell. The bottom-up kettlebell won on one muscle only, the serratus anterior, which holds the shoulder blade against the ribs.

At equal load, the kettlebell does not work the deltoid harder than the dumbbell. It remains an option when it is the only equipment available.

Machine or free weights

Coratella et al. (2022) compared the barbell and the shoulder press machine in their eight bodybuilders. The barbell excited the muscles more than the machine, which guides the path of the load.

Over time, the gap does not show. Hernández-Belmonte et al. (2023) trained 38 men for 8 weeks with free weights or machines, on the squat, bench press, prone bench pull and shoulder press. Strength gains were similar, within 1.8%, and the cross-sectional area of the measured muscles grew as much in both groups. Joint discomfort dropped in both. The study measured the quadriceps, the pec and the abs, not the deltoid.

Loads do not carry over from one piece of equipment to another. Lyons et al. (2010) tested 31 trained men on three Hammer Strength machines and three matching free-weight exercises. The 1RM was higher on the machine for every exercise, and the machine shoulder press 1RM could not be predicted from the free-weight press. When moving from the machine to the barbell, start again from a tested load. The 1RM guide explains how to estimate it without going to failure.

Bar in front of or behind the neck

Coratella et al. (2022) measured more side and rear deltoid activity when the bar passed behind the head, and more pectoralis major activity when it passed in front. Upper trapezius activity did not change.

Padovan et al. (2025) repeated the comparison in 14 trained men, with an 8-rep-max load and high-density electrodes. In front of the head, the front deltoid and the pec worked harder. Behind the neck, on the way down, the rear deltoid, upper trapezius and triceps worked harder. The two studies disagree on the front deltoid. For the authors, both versions have a place in a program.

None of the studies read measures the injury risk of the behind-the-neck press. Kolber et al. (2010) reviewed injuries linked to resistance training: up to 36% involve the shoulder, and poor attention to technique is one of the factors that raises that risk. If the bar cannot pass behind your head without forcing, the front version works the same muscles, in different proportions (Coratella et al., 2022).

How far to lower and press

Paoli et al. (2010) had six experienced lifters do the seated military press with three ranges of motion: elbow bent to 90°, to 135°, or arms locked out overhead at 180°. The full range increased the activity of almost every muscle measured, deltoids, trapezius and triceps included.

A partial range isolated the side deltoid from the trapezius only with the heaviest load, 70% of 1RM. Unless you have a specific goal, press all the way to lockout.

How to do the barbell military press

1. Stand with feet hip-width apart, bar resting on the upper chest, hands slightly wider than the shoulders.
2. Brace your glutes and abs, then press the bar straight up, head tilted slightly back to let it pass.
3. Once the bar has passed your forehead, bring your head back under the bar and finish with locked arms.
4. Lower under control to the upper chest, without arching your lower back.

Seated, the backrest replaces the leg and trunk bracing, and the load can go up (Saeterbakken and Fimland, 2013). With dumbbells, the elbows start slightly in front of the body and the dumbbells almost meet overhead.

The shoulder presses in the Overload library

The Overload exercise library holds 878 movements. Twenty-eight of them are strict shoulder presses, with no leg drive: barbell, dumbbells, kettlebell, machine, Smith machine, cable and bands. All have the shoulders as primary muscle and the triceps as secondary.

Variation	Equipment	Secondary muscles	Member uses
Machine Shoulder (Military) Press	Machine	Triceps	1,130
Seated Dumbbell Press	Dumbbells	Triceps	375
Seated Barbell Military Press	Barbell	Triceps	168
Standing Military Press	Barbell	Triceps	128
Smith Machine Overhead Shoulder Press	Smith	Triceps	97
Leverage Shoulder Press	Machine	Triceps	47
Smith Behind Neck Press	Smith	Triceps, traps	11
Kettlebell Arnold Press	Kettlebell	Triceps	7
Standing Barbell Press Behind Neck	Barbell	Triceps	6
Arnold Dumbbell Press	Dumbbells	Triceps	5
Alternating Kettlebell Press	Kettlebell	Triceps	1
Two-Arm Kettlebell Military Press	Kettlebell	Triceps	1
One-Arm Kettlebell Military Press To The Side	Kettlebell	Triceps	1

The other fifteen variations have never been logged, including the standing dumbbell press, the three cable shoulder presses and the band shoulder press. Each use is one logged workout that contains the movement, whatever the number of sets. The count says neither how many members do each variation nor how long it has been in the library.

The 28 presses add up to 1,977 uses, and the machine takes six in ten.

Equipment	Variations	Member uses	Share
Machine	2	1,177	60%
Dumbbells	8	380	19%
Barbell	5	302	15%
Smith	2	108	5%
Kettlebell	7	10	0.5%
Cable	3	0	0%
Bands	1	0	0%

The machine military press alone comes close to the barbell bench press: 1,130 uses against 1,286. Variations named seated add up to 543 uses, those named standing to 134.

Usage runs opposite to the measurements. The variation that worked the deltoid hardest in Saeterbakken and Fimland (2013), standing with dumbbells, has never been logged. The kettlebell, which did worse than the dumbbell in Dicus et al. (2018) and Busch et al. (2024), has only 10 uses. The machine, the one that demands the least stability, takes most of the workouts, and Hernández-Belmonte et al. (2023) measured strength gains over 8 weeks equal to those from free weights.

Practical recommendations

• To work the deltoid hardest on every rep, press standing with dumbbells (Saeterbakken and Fimland, 2013).
• To push the heaviest load, press seated or with a barbell. The 1RM was higher in both cases (Saeterbakken and Fimland, 2013).
• If you prefer the machine, keep it: over 8 weeks, it produced the same strength gains as free weights (Hernández-Belmonte et al., 2023).
• Do not carry a load over from the machine to the barbell. The 1RMs differ and do not predict each other (Lyons et al., 2010).
• Pick the dumbbell over the kettlebell at equal load if the deltoid is the target (Dicus et al., 2018).
• Press to lockout: the full range increased the activity of almost every muscle measured (Paoli et al., 2010).
• For the rotator cuff, see the external rotation guide. For cables, the cables vs free weights guide covers what the cable changes.

Conclusion

Standing with dumbbells, the deltoid works hardest and the load is lowest (Saeterbakken and Fimland, 2013). Seated, with a barbell or on a machine, the load goes up, and 8 weeks of machine work produced as much strength as free weights (Hernández-Belmonte et al., 2023). Overload members have settled on the machine, six shoulder press workouts in ten.

This article presents current scientific evidence. If you have shoulder pain, or for a personalized program, consult a healthcare professional.