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David and Goliath: What Determines Strength?

Posted Dec 20 2008 6:38pm

Teri asks:

I have larger hip muscles than Joanne.  So why is it that she can lift more than I can in lower body exercises?

It may surprise you to discover that there are lots of factors that determine strength (or, more accurately, expression of strength).  Here’s a quick and dirty list compiled off the top of my head, and you can almost bet that it isn’t exhaustive:

  • Cross-sectional diameter
  • Neurological efficiency
  • Tendon length
  • Tendon attachment point
  • Limb (bone) length
  • Technique*

* I hasten to add that “technique” is more a factor that influences expression of strength, as opposed to “strength” proper.  So why is it listed?  Because you can’t really quantify strength without expressing it (i.e., you can’t test strength without lifting something).

It might be due to one or more of the listed factors (and perhaps, all of them) that a person with smaller muscles can outlift a person with larger muscles (in Joanne and Teri’s case, it’s probably 2, 3, and 5).

You’ll note that of the factors listed, only two are factors you can change: Cross-sectional diameter (aka muscle size) and technique.  So it’s not worth worrying about the others, nor is it worth fretting over how much you can lift vs. how much someone else can lift (unless, of course, you’re facing them in a powerlifting meet).  Instead, place a high emphasis on progression:

  • How much can you lift today?
  • How does it compare to what you lifted last week?  Last year?
  • How much (more, I hope) will you be lifting next month?

It’s fun to see how you stack up against others - the entire human race would wither away if we didn’t have that primal urge to be king or queen of the pack - but ultimately, physical fitness (and everything that term means to you) is a solitary affair.  The only person you’re racing with is yourself.

Edit (12/17/08): Samantha adds two more changable factors that influence strength: Fat levels (more fat = more leverage ) and recruitment (note: This is different from neural efficiency.  I’ll explain in the next post).

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