If you have ever taken a few weeks off from exercise and then completed a strenuous workout, you may know what I'm about to say.
That first workout back from a long break can be tough, but it's usually the soreness that follows a few days later that is really brutal. For example, if you do a squat workout after a few weeks off, it can hurt to simply sit in a chair or climb the stairs later that week. 
One of the quickest ways to resolve this soreness is very counterintuitive:
Squat again.
If I'm feeling sore a few days after a squat workout, then doing some light reps is often the quickest way to recover from the soreness. I'll usually opt for three sets of ten bodyweight squats. The first few are uncomfortable, but then my muscles limber up and I feel significantly better by the end of it.
How could this be? If squatting caused the pain, then why would more squatting resolve it? It's sort of like saying, “I spent too much money, so my solution is to spend a little more money.”
On the surface, this makes little sense. But, as you may expect, there is something deeper going on here. It's called the Repeated Bout Effect and it applies to much more than just exercise.

The Repeated Bout Effect

Here’s the Repeated Bout Effect in plain language:
The more you repeat a behavior, the less it impacts you because you become accustomed to it.
The Repeated Bout Effect comes from exercise science research, so let's return to our previous squat example.
When you perform a new squat workout your body will experience a new stimulus that stresses your muscles and, eventually, results in muscle soreness. However, the way you respond to this new stimulus is not constant. Researchers have found that “a repeated bout results in reduced symptoms.”  Generally speaking, the more consistently you squat, the less soreness you will experience.
This is what is known as the Repeated Bout Effect. Your body's response to a stimulus decreases with each repeated bout.
There are hundreds of research studies confirming the Repeated Bout Effect. The exact mechanism by which it occurs isn't totally understood, but the fact that it does occur has been well-established. 

The Repeated Bout Effect in Your Life

The Repeated Bout Effect tells us that the more we do something, the less of an impact it makes on us. There are many ways to think about this effect throughout life.
  • When you haven't done much strength training, doing thirty pushups will make you stronger. After a few months of that, however, an extra thirty pushups isn't really building new muscle.
  • When you drink coffee for the first time, you will notice an immediate caffeine spike. After years of consumption, however, one cup of coffee seems to make less of a difference.
  • When you start eating smaller portions, you'll lose weight. After the first ten or fifteen pounds fall off, however, your smaller portion slowly becomes your normal portion and weight loss stalls.
  • Making ten sales calls on your first day in business may lead to a big jump in overall revenue. Making ten sales calls for the 300th day in a row, however, is unlikely to have a large impact on overall revenue.
These examples make sense when you see them neatly lined up in an article, but out in the real world we often curse ourselves for a lack of progress.
Let’s say you want to lose weight and you weren’t working out previously. You start running twice per week and pretty soon you've lost ten pounds. At some point, the Repeated Bout Effect kicks in, your body adapts, and the weight loss slows. Suddenly, you're still running twice per week but the scale is no longer moving.
It can be very easy to interpret these diminishing results as some kind of failure.
  • “This always happens. I make a little bit of progress and then I hit a plateau.”
  • “Ugh, I'm working out every week and nothing is happening.”
  • “I've tried it all. Exercise doesn't work for me.”
Except, it did work. In fact, your initial exercise worked exactly as it was supposed to because it delivered a new result and then your body adapted and became better. Now, your body has a new baseline and if you want to achieve a higher level of success, then you need to add something new to the mix.

3 Lessons On Improvement

The Repeated Bout Effect can teach us three lessons on improvement.
First, doing a light amount of work is a great way to reduce the pain of difficult sessions. Imagine that you do an easy 1-minute pushup workout on Monday and a difficult 10-minute pushup session on Friday. The Repeated Bout Effect says that your soreness after Friday's workout will be reduced simply because you did an easy session earlier in the week. Easy work can make a difference.
Second, the amount of work that you need to do to reach your maximum level of output is higher than what you are doing now. Unless you are already performing at 100 percent of your potential, you have room to grow. And the Repeated Bout Effect tells us that you have probably adapted to all of the normal stimuli in your life. If you want to reach a new level of success then you need to put in a new level of work. This does not mean you should start by doing as much work as possible, but it does mean that when you start small you can't expect one small change to work forever. You have to continually graduate to the next level.
Third, deliberate practice is critical to long-term success. Doing the same type of work over and over again is a strange form of laziness. You can’t go to the gym, run the same three miles each week, and expect to enjoy ever-improving results. After a few months of repetitive workouts, you’ve seen all the results that three-mile runs can deliver and your body has adapted to that stimulus. This is why deliberately practicing new skills that you can master in one to three practice sessions is important for long-term improvement. Making deliberate practice a habit can help you avoid carelessly practicing things that no longer deliver any benefit.
The key takeaway here is that things will work for a little while and then we will get used to them.
As Marshall Goldsmith says in his best-selling book, “What got you here won’t get you there.” Doing the same thing over and over again, even if it worked for a long time, will eventually lead to a plateau. If nothing changes, nothing is going to change