Lifting - Burn vs. failure

Papillon22

Hi!
as I take my first steps into the lifting world, I've noticed that sometimes I have to stop an exercise because of how much my muscles burn (happens with shoulders especially) and sometimes I stop because my muscles fail (as in, I can't do another rep) but there is no burn. I wonder why is it that the muscles respond differently and whether this is due to doing something wrong (I work out at home, btw).
Thanks!

Papillon22

oh, come on! anyone?

guroprincess

The "burn" is due to lactic acid. If you want the sciencey explanation, check out Wikipedia:
http://en.wikipedia.org/wiki/Lactic_acid

If you want the layman's terms, Livestrong has an article about it:
http://www.livestrong.com/article/446321-why-do-you-get-a-burning-sensation-in-your-muscles-during-strenuous-exercise/

MattDustin

Hey there! First of all, congratulations on beginning lifting - hope you keep at it and never stop!

Basically, when you do higher repetition training, the "burn" typically happens. This is due to lactic acid production.

Lower rep (heavier) lifting is not always enough to create lactic acid, since lactic acid typically occurs with lots of time under tension - or how much time your muscles spend under stress.

You aren't doing anything wrong, different repetitions ranges are for different goals!

As a very general guideline,

1-5 repetitions will increase muscular strength
6-12 will increase strength and hypertrophy, or muscular size and growth
13 and up is more endurance - think of the burn. This won't do much at all for strength, but it will burn, and can help you increase muscular size.

So you aren't doing anything wrong as long as you are lifting for your goals! Hope that helps a little

Papillon22

Thank you both for your replies!
Too bad muscle burn =/= fat burn :grumble:
And since my left shoulder is where I usually feel the burn, I guess it means that it is less strong than my right one. Correct?

astronomicals

Thank you both for your replies!
Too bad muscle burn =/= fat burn :grumble:
And since my left shoulder is where I usually feel the burn, I guess it means that it is less strong than my right one. Correct?

Not necessarily... Are you lefty?

doing unilateral exercises is how you'll find an imbalance

Papillon22

Not necessarily... Are you lefty?

doing unilateral exercises is how you'll find an imbalance

I'm not left handed. I find that my left shoulder burns when I'm doing, for example, a shoulder press (both arms at the same time) while my right one doesn't.