A common question when it comes to resistance training is whether or not you should take your sets to failure. Should every set be an all out set where you go until your muscles can't go anymore, or do you stop just before this point? While training all out may seem like the common sense answer to making fast progress, the truth is that going to failure too often is a sure fire way to prevent progress by digging yourself into a recovery rut. When the stress you place on your body from training exceeds your capacity to recover, not only can progress slow down, but it can actually regress until you allow your body to recover.
Recovery is just as important as training itself and is literally one half of the equation for making progress. If you don't fully recover from your training, you risk not only hindering progress, but even potentially regressing. This is why it is very important to understand a concept called Reps in Reserve or RIR for short, which is a tool used to track how many reps you have left in you when you stop a set. Modern research suggests that as long as you leave 4 reps in the tank or less, you will produce an adequate hypertrophic stimulus. This means that most of your working sets should be at least 4 reps or less from failure to make good progress.
When comparing single sets, there is a slight increase in muscle hypertrophy when going to failure versus not going to failure. However, there is also a very large increase in training fatigue. The body becomes better and stronger once it recovers from the training fatigue built up from hard training. By constantly training to failure, you are creating a very large amount of fatigue that is very difficult to recover from on a consistent basis, yet provides little extra benefit. If you’re under recovering between workouts, each time you go into the gym you’re working at a reduced capacity, performance begins to decrease, and the amount of stimulus you're able to achieve suffers. This will continue until you dial it back a bit and allow your body to recover.
By not going to failure, you’re allowing your body to get a quality training stimulus without the large increase in training fatigue. Not only is this better for the simple fact that it’s easier to recover from before you need to train again, but it allows you to also get much more work done in the same workout, as you’re left feeling much less tired out after each set. This style of training is much more productive for being able to progress consistently long term.
Take the graph above as an example. Let's say that your body is able to recover from 15 units of fatigue. This means that you want to cram in as much quality work before you reach those 15 units of fatigue in order to maximize hypertrophy. Using the graph as a reference, we can then see that each set with an RIR of 3 would give us 1 unit of hypertrophy and 1.5 units of fatigue. This allows us to perform 10 sets at an RIR of 3 before we reach our recovery limit, netting us a total of 10 units of hypertrophy. Compare this to taking your sets to failure. If you took only 3 sets to failure, you'd exceed your capacity to recover, meaning you'd have to settle for only 2 sets, netting you only 5 units of hypertrophy.
In my article Understanding Volume & Fatigue, I talk about how the more sets you do, the more muscle and strength you gain (up until a certain point). Because of this, it is much better to train leaving 2-3 reps in the tank on average, instead of going straight to failure from the get go. By going to failure early on in a workout, you make it harder to continue to perform quality working sets due to the intense fatigue generated. Not only will your performance during this workout suffer, but if you continue to take additional sets to failure as well, you will have a hard time recovering from your workout and will be less likely to come back into the gym fully recovered on time to perform another quality workout.
By keeping reps in the tank, not only are you able to perform more total work per session, but it’s far easier to recover from between workouts and thus allows you to train more frequently, helping drive long term progress more efficiently. A person doing 20 sets of chest per week who leaves reps in the tank will make steady progress without risk of recovery issues or injury, while a person attempting to perform 20 sets of chest to failure will dig themselves into a recovery rut within a two week period (probably less) and begin to stall or get injured, requiring valuable time off from the gym in order to recover.
Training to failure can be beneficial and has multiple uses. It can be a great tool for properly managing Reps in Reserve, because by training to failure you know how accurate your RIR estimates are for example. It can also be used as a form of additional training stimulus when you've hit a sticking point and have tried other methods to push through. When increasing volume is no longer an option, you can occasionally push the last set on some of your exercises to failure just to get a slightly stronger training stimulus. It’s important, however, that this is only done occasionally and not on every single exercise.
Many routines also include sets where you will perform as many reps as possible (AMRAP) in order to test and/or build strength at different scheduled periods. One example is in the 5/3/1 program where you will take at least one set near or to failure every workout day.
It may also be a good idea to go to failure more often right before a scheduled deload if your current routine includes them. By doing this you can cause a stronger stimulus and still be able to recover from it when you take your deload, allowing you to take full advantage of the extra recovery potential you have coming up. Normally you would need to be recovered by the next 28-48 hours in preparation for another workout, but because of the deload, you have an entire full week to recover. It only makes sense that if you're going to have extra recovery, you might as well get an increased training stimulus as well to reap the benefits.
Going closer to failure can also be a good way to get in a stronger training stimulus when you are strapped for time and can't perform as many sets as you'd like to. Let's say that you'd typically perform 10 sets for chest, but you won't have the time to finish all of your sets. To make up for the lost stimulus due to having to do less sets, you can take a couple of the sets to failure to make up for doing less overall sets.
The takeaway is that while going to failure has an important place in training, namely to test strength and provide a more powerful training stimulus per set when needed, it should be used sparingly due to the large amount of training fatigued it causes. The majority of your training should be done with sets leaving 2-3 reps left in you when you rack the bar. Sets going to failure need to have a specific purpose, should be scheduled ahead of time and programmed intelligently in order to allow for proper recovery. A failure to properly manage training and recovery is one of the key reasons novices and intermediates (even some advanced trainees) stall and fail to progress.