What is the ideal rest time between weight training exercises? As with most questions to trainers, the “answer” to this question is that it depends on your goal. How many days a week you train, how many days between workouts, how much time between sets, etc. all depends on the overall goal that you are working toward. The most common goals usually are something in these three categories; strength, hypertrophy, or endurance. Most any goal will be able to fit somewhere into these categories, especially when it comes to rest during a workout.
Muscles need energy to move, and they need a lot of energy to workout. But different workouts use different types of energy within muscles. Without getting too deep into the science of it all, endurance training is aerobic (with oxygen), while strength or power movements are usually anaerobic (without oxygen). All this really means is that muscles use different energy stores depending on the exercise that you are putting it through. Each of those energy stores take a different amount of time in order to refill and be able to be used again.
Strength training is focused on power. How much weight can you move? One rep max is the most common test to determine strength, and therefor the focus is low reps, high weight, and a lot of rest. Only doing a couple reps of an exercise requires energy extremely fast, and so muscles pull from what’s called the ATP-PC (adenosine triphosphate phosphocreatine) system. Again trying not to get too scientific, but know that your body has a very small reserve of phosphagens that can be used for this system. So after 1-6 reps of an exercise that reserve is gone, and it takes between 2-4 minutes to replenish. Which means, you guessed it, the ideal rest time for strength training is between 2-4 minutes.
Hypertrophy training is trying to get leaner, bigger, “toned”, etc. Long story short; mid reps, mid weight, mid rest. Every type of training adds together, so hypertrophy training also uses the ATP-PC system but also adds the glycolytic system. Adding on this other system means that your rest time can drop to anywhere between 1-3 minutes, because the glycolytic system has a larger reserve to pull from.
Lastly, because endurance training is aerobic, there is the most access to energy in our body. High reps, low weight, low rest. Anywhere from 30seconds to a minute is sufficient for rest during your endurance training.
The trainer in me also has to make sure you know that rest is hugely important in your workout. Take advantage of the rest time, and make sure you get enough of it for your goals. That being said, sitting on your phone for 15 minutes between exercises cannot be called “rest time.”