What's the deal with how long you should rest between sets?

There is some science to how long you should rest between weightlifting sets and it comes down to what are you trying to accomplish.  If you're goal is to simply build strength, you should rest a minimum of 2 minutes between sets.  This may seem like a lot, but don't rush if gaining more power is the goal.  If endurance is your goal only rest for less than 30 seconds and consider supersets as another option.  Pushing yourself with shorter rest periods will increase your bodies level of endurance, but may not provide the rest needed for optimal strength increase.

This all comes down to ATP, an energy carrying molecule, and creatine phosphate, the main high-energy phosphate-storage molecule of your muscles.  They work together to provide energy to your muscles to do what they do.  As you workout you deplete your stores of creatine phosphate, so you loose the ATP to power your movements, causing you to feel weakened.  A rest period restores this supply which restores ATP levels giving your muscles the energy to continue.  These levels can be depleted in just 10 seconds of intense workout and can take as long as 5 minutes to return to 100%, so a rest period is also necessary if need more muscle energy to power through your workout.  You don't need to return to 100% for these benefits, resting for approximately 2 minutes will get you close enough.

So what is there to do during longer rest periods?

Here's a list of some options of ways to be productive with your time and make the most of those longer rest periods...

1. Read a book or article

2. Listen to a podcast

3. Jam out to some music

4. Meditate

5. Do light cardio working other muscles

6. Spot someone else in the gym

7. Plan the rest of your day

8. Journal and record your progress

9. Interact online offering fitness advice and motivation

10. Share and seek advice and motivation by talking with others at the gym

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