Lift heavy to build muscle: Thats advice youve probably seen in a million places, whether you're aiming to get stronger, get "toned," or simply reap the health benefits of putting on a little muscle. But how heavy is heavy, and how do you know if your workout qualifies? Theres no specific number of pounds that will constitute heavy for everyone. Whats heavy for a teenage girl picking up a dumbbell for the first time will be a lot less than whats heavy for a pro strongman. (If you do want to compare your lifts to other people's, sites like Symmetric Strength can show where you standbut please consider these comps as just for fun.) In basic terms, training heavy is shorthand for resistance training that is in a low-rep range and gets heavier over time. This is the type of training that delivers the biggest gains in terms of strength and muscle size. Training heavy is not the only way to build muscle, but its an effective one. Here are the questions you should ask yourself when trying to figure out whether you're training heavy enough.How many reps are you doing?Training for strength usually has you doing 1-5 reps in each set. Training for hypertrophy (bigger muscles) is often in the 8-12 range. The truth is, there isnt much difference in results between the two methods; getting stronger gives you bigger muscles and getting bigger muscles makes you stronger. Id say that as long as youre doing 12 reps or fewer, youre in an appropriate range to say you are training heavy. Once youre doing much more than that15, 20, 50 repsyoure training your muscular endurance more than strength. You can build some strength this way, but it's not what you're going for when you're trying to train heavy. How hard does the set feel?Lets say youre doing squats in sets of eight. That could count as heavy training, but only if youre loading the squats enough that its hard to do all eightof them. For some exercises and some goals, you might be aiming to train "to failure"literally, going until you cant do another rep. An example would be if youre doing eight bicep curls and cant manage a ninth. But you can also get close to failure without quite going there. For example, if youre doing squats, a set of eight might be done at a weight that you could manage for 10 or 11 reps if you really pushed yourself. That still counts as heavy training. What doesnt count is if youre doing eight reps of goblet squats with a light dumbbell because its the only dumbbell you have, or because youre intimidated about going up in weight. Heavy lifting is when youre doing the appropriate rep range with a weight that is challenging within that range.Are you increasing the weight over time?The only way to keep the lift challenging as you get stronger is to keep increasing the weight. This doesn't mean you need to go heavier every time, but it does mean that you pick up a heavier weight once you've gotten a bit stronger. To use that goblet squat example, maybe squatting with a 20-pound dumbbell was challenging the first time you tried it. But a week or two later, you can probably do the same eight reps with a 25-pound dumbbell. Before long, it may make more sense to do front squats with a barbell, to make it easier to add more weight. OK, now youre lifting heavy.But if you kept doing the same sets of eight squats with the same 20-pound dumbbell, youre not efficiently challenging yourself to build muscle or strengthyoure just doing an exercise that keeps getting easier. Thats still good for you, because its still exercise, but it no longer fits the description of lifting heavy.How long are you resting between sets?This is where a lot of people go wrong, especially if theyre doing home workouts or are focused on calorie burn. You shouldn't lift heavy for the calorie burn (or heart rate zones) during the workout; you should lift heavy to build muscle, and save the cardio for another day. If youre constantly working to keep your heart rate up, with little to no time to rest between exercises, you arent going to be able to train heavy. More likely youre doing a strength/cardio hybrid such as circuit training. Crossfit metcon WODs (workouts of the day) often fall into this category, as do many home workout videos that bill themselves as high-intensity interval training (HIIT). Theyre usually not really HIIT, but thats a rant for another time.If you arent resting, that means you arent approaching each set of lifts with fresh, rested muscles. Reducing rest times makes the workouts feel harder, but it also means youll be working with less weight. That means these exercises are usually too light fit the definition of working heavy. They might still help you build strength or muscle size, but not nearly as efficiently. If you take a few minutes rest between exercises, then youre lifting heavy. A typical range would be 2-4 minutes between exercises that work smaller or fewer muscles (like curls or presses) and 3-5 minutes or more between sets of big compound lifts (like squats or deadlifts). With an appropriate rest time, youll be able to properly lift heavy.