Do I Really Need to Rest That Much In Between Exercises?
TLDR: If you are trying to get stronger or gain muscle, you should rest as long as it takes for your heart rate to come down to normal in between sets so that you can give the best effort for each set
Why do you even need to rest in between sets? For one, everything that is responsible for allowing you to do more simply stops and your body needs time to replenish itself to be able to go again. Your heart will start to race to pump blood to the areas that you are working out and a high heart rate will prevent you from getting very much of a benefit out of the next set. At the very least, it will change the benefit that you do get. When we rest very little in between sets or do a bunch of exercises back to back we limit how heavy you can lift, which will prevent you from getting stronger, adding muscle or having a positive impact on your bone density. Instead, you will get a cardiovascular benefit, but not as good a one as if you just did cardio. With a lot of workouts that involve resting very little you end up not getting as good a strength workout or as good a cardiovascular workout. You get the worst of both worlds.
How much should you rest? There is actually a lot of research on this topic, although much of it is conflicting. While some studies have found 3 minutes or more to be the minimum necessary to maximize the benefits of lifting weights, others have shown 1 minute to be just as effective as 3. While the research is conflicting, I think it's because there is a lack of context in how this research is done. I advise clients of mine to rest as long as it takes for their heart rate to come back to its baseline level, which will depend on whether you are a powerlifter doing sets of 5 squats at 500 pounds or a marathon runner doing sets of 15 on bicep curls. The better your cardiovascular system and the less total amount of muscle you are involving in an exercise will mean the less rest you need. When in doubt I would err on the side of a little bit more rather than less to make sure you get the most out of your strength work.
