So you've been lifting for a while and you've seen some great progress. Your training weights have gone up quite a bit and you may even be starting to see the results in the mirror. But something is terribly wrong. Recently, things have started to get hard. Your gains have slowed down or stopped completely and you have no idea why. I'm here to set you straight and show you that there's almost never a complicated answer to this.
Here are the top 6 reasons, in order of likelihood:
1. Your diet sucks
In my experience this is the number one culprit for plateauing. If your body weight hasn't changed at all since beginning training, then this is almost certainly the answer.
Rank novices can get away with poor nutrition for the first few weeks - couple months, but that will end very quickly. It doesn't matter how hard you train, if you don't give your body the nutrients it requires, it can't grow muscle. Generally the issue is not just what you're eating, but how much. If getting stronger and building muscle is a priority for you, you have to eat more calories than you burn. And a significant chunk of those calories need to be protein. For more detail on this, consult the 'Nutrition Part 2' and 'Nutrition for Hardgainers' articles.
2. Your sleep sucks
As mentioned with food, your body can't get stronger if it's not provided the resources to do it. Sleep is the time when your body can grow and recover most. You need to be getting at minimum seven hours.
Eight is better, nine is best (for most people).
For more on sleep, consult the sleep article.
3. You're not following a programme
One of the most important training principles is that of specificity. You get good at what you do. If you want your bench press to go up but you're only training it every 2 weeks, it's no mystery why it's plateaud. However even for more general goals of gaining strength and muscle, it's always better to have a plan than to just go into the gym and do random exercises, sets and reps. Here's how to fix this:
Step 1: Pick a training programme. For beginners I mainly recommend Starting Strength or 5/3/1.
Step 2: Follow the programme to the letter. No changes. ]
Step 3: Log all your workouts in a log. This makes it very easy to tell if you're making progress. Strength and muscle gain is not going to occur without increases in your basic lifts.
4. You're doing too much / (not following the programme)
Even in the unlikely scenario of you having your food and sleep on point, your body can only recover from so much.
Are you trying to get strong and good at running at the same time? Have you taken a time-tested strength programme, but decided to add a bunch of other exercises on top of it? Are you trying to do 5 days a week of heavy gym training combined with 3 days a week of another sport? You can't just keep adding stuff without subtracting something else. The man who chases 2 rabbits catches neither.
5. You're not resting enough between sets
This is strength training, not a spin class. The objective is to lift progressively heavier weights, not to 'get a sweat on'. If you only give yourself a minute or less of rest, you're fatiguing yourself and making this much harder than it needs to be. Conditioning has it's time and place, but under a heavy barbell is not it.
For strength training, you need to be getting a minimum of 2 minutes of rest. As you get stronger and the loads on your body increase, you may well need to rest much more than this. I've personally rested for 5 minutes or longer between heavy deadlifts before.
As you get more experienced, you'll know when you're ready to go again. But for now, just make sure you're getting about 2 - 4 minutes of rest between sets.
6. Your training lacks variety
This is listed last for a very good reason. I have very rarely encountered someone who had plateaued for this reason. For your body to plateau from a lack of variety, you need to have followed a programme extremely consistently for a long period of time. And this is something that 99% of trainees don't do.
So, if you haven't followed a beginner programme for at least a year and drained every bit of gains out of it, then this doesn't apply to you.
If you have genuinely hit a plateau due to the diminishing returns of a programme, there are some very simple changes you can make.
1. Change up the rep schemes. E.g. If you usually do sets of 5 on bench, give some sets of 2-3 a try.
2. Change up the accessory exercises. E.g. Getting sick of dips? Try a different exercise like dumbbell bench, weighted push-ups, etc.
3. Change your training frequency. You may find you respond better to less/more training sessions per week. E.g. Your squat may get stronger if you did 3 days a week instead of 2.
4. Change the main lift. There are lots of variations of the basic lifts you can use to target areas of weakness, or just for the sake of a mental break from doing the same lift over and over. E.g. Safety bar squat, front squat, trap bar deadlift, incline press, close grip bench, deficit deadlift, snatch grip deadlift, etc.