I regularly lift 40lbs (each arm) dumbbell curls for 8-10 reps for 6 sets in the gym. I have good form (not swaying/cheating) and do slow and controlled reps. I see guys lifting 20-30lbs with arms 4x bigger than mine, which are 11" unflexed.

How is that possible? I want to get bigger arms, what am I doing wrong?enter image description here

  • Training for strenth and training for hypertrophy is somewhat different. When the goal is hypertrophy, the number of reps is largely irrelevant. Arguably the most important training variable is how close you train to failure. You don't state whether or not those 8-10 curls are to failure or not. The amount of calories and protein you eat is also quite important. So without more information it's hard to help. Commented Jul 7, 2023 at 19:03
  • @leon.fuchsler As long as you’re within four or five reps of failure, proximity to failure is largely irrelevant.
    – Thomas Markov
    Commented Jul 7, 2023 at 21:03
  • @ThomasMarkovisonStrike The majority of studies that compare 1-3 RIR to failure training conclude that it is similar for hypertrophy. I am aware of only 4 studies that directly or indireclty compare >3 RIR to failure training. Martorelli and Karsten conclude 5 RIR is worse than failure. Lasevicius shows 5-6 sets of 5RIR is similar to 3 sets to failure. Commented Jul 7, 2023 at 23:09
  • @ThomasMarkovisonStrike The only study that I know of which supports your point is by Carroll. A potential confounding factor of that study however is that they performed additional sprint training 2x a week, which arguably disfavors the failure group as this makes it harder to recover. If you are aware of any research that I am not, I would much appreciate you pointing me in the right direction, otherwise I strongly disagree. Commented Jul 7, 2023 at 23:15
  • @leon.fuchsler There’s a good overview on the Iron Culture Podcast, see the show notes for the relevant studies.
    – Thomas Markov
    Commented Jul 7, 2023 at 23:35

1 Answer 1


Sometimes it simply comes down to genetics which can't be changed. Some people just have shorter or longer biceps. Shorter biceps contract further making them have a higher peak and look bigger where as longer biceps do not contract as far thus making them peak less and seem smaller. None of this change functionality though, short and long biceps can build strength just as easy.

A good example of this is Arnold's biceps. There are other bodybuilders who are just as big as he was but he had some of the craziest biceps in history because of his short insertions.

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