Browse evidence-based analysis of health-related claims and assertions
If young women do incline bicep curls twice a week for 8 weeks, their upper arm muscles grow more than if they did preacher curls — the type of curl really affects where the muscle grows.
Ultrasound can reliably measure arm muscle size in active women, and the same person can get consistent results when repeating the measurement—making it a trustworthy way to track muscle growth from workouts.
For women who work out regularly, doing preacher curls or incline bicep curls doesn't seem to change where their biceps grow — both exercises lead to similar growth patterns after 9 weeks.
Doing inclined bicep curls 3 times a week for 9 weeks doesn’t seem to make women’s biceps grow more in specific areas, even when they push themselves to the max each time.
Doing preacher curls might help women who work out regularly build more arm muscle, especially toward the lower part of the upper arm, and after about 9 weeks they could see around a 9% increase.
If young guys lift weights all over their body 3 times a week for 9 weeks, they'll get stronger — no matter if they switch up their exercises or stick to the same ones.
If young guys switch up their weightlifting exercises for the same muscles, they’ll get just as strong as if they stuck to the same routine for 9 weeks.
If young guys stick to the same exercises every time they work out for about two months, they get stronger in a specific leg test than if they keep switching up their routine.
If you're a guy who already lifts weights, doing 4 workouts a week for 8 weeks will make you way stronger—adding about 25 pounds to your squat and 10 pounds to your bench, whether you stick to the same routine or mix it up.
If gym guys switch up their workouts randomly every time, they stay more motivated over 8 weeks compared to doing the same routine every time.
If you're a guy who's already lifting weights, doing 4 workouts a week for 8 weeks will noticeably grow your thigh muscles — and it doesn’t matter whether you stick to the same routine or mix it up every time.
If gym guys use an app to switch up their workouts every time, they might enjoy training more — without losing gains in leg strength or muscle size.
If you switch up your leg exercises during a workout routine, you might build more muscle in certain parts of your thigh—like the upper side—compared to sticking with the same moves.
If young guys who used to work out take a break and then do the same strength exercises over and over for about two months, some parts of their muscles might not grow much — especially on the side of the thigh and upper arm — which means doing the same routine might not help all muscles grow equally.
If you mix up your strength workouts for the same muscle, it might help it grow more evenly from top to bottom, especially if you haven’t been training for a while.
Just because a study doesn’t find a clear difference in arm muscle growth between two curl types, it doesn’t mean there isn’t a real difference — the study might just be too small to catch it.
If you stretch your hips back while doing leg extensions, your quad muscle gets longer and grows more—especially in the middle and upper parts—than if you do the exercise with your hips bent.
If you mix up your workouts for the same muscle, you’ll grow that muscle more evenly than if you always do the same exercise.
Doing bicep curls on an incline bench might build your biceps muscle better than doing preacher curls, especially in the middle part of your upper arm.
Small studies might miss real differences just because they don’t have enough people in them — it’s like trying to hear a whisper in a noisy room.
Doing preacher curls might build more muscle in a specific lower part of your upper arm than incline curls do.
Doing bicep curls on an incline bench builds more muscle in the upper part of your biceps than preacher curls do.
If you do leg extensions while leaning back, it might build more muscle in the top part of your front thigh compared to doing them upright.
Working your biceps with your arms stretched back might grow the upper part of the muscle a bit more than doing curls with your arms already in front of you.