With knowledge workers--software engineers, writers, entrepreneurs, and most people with a "white-collar" job--currently outnumbering all other workers in the U.S. four to one, it's clear that the thinkers will inherit the Earth.

Yet with longer days, higher expectations, and the constant pinging of notifications and messages, our ability to focus has dropped to an all-time low. In fact, many reports show that healthy adults aren't able to focus on a task for longer than 20 minutes at a time.

Yet our jobs and careers depend on our ability to think for long periods of time.

Luckily, scientific research has identified some fantastic ways to fight distraction and boost our natural ability to focus for longer periods of time.

These aren't hacks, but rather ways to slowly rebuild your attention muscle and become more focused in your work and your life.

1. Use workday structure to increase your focus slowly

If you've made it this far, congratulations! Your focus isn't as terrible as it could be. However, the path to regaining control of your attention is a long one. Studies have shown that to rebuild your attention muscle it's better to break your workday into manageable chunks, with regular breaks in between them.

After analyzing 5.5 million daily records of how office workers are using their computers (based on what the users self-identified as "productive" work), the team at DeskTime found that the top 10 percent of productive workers worked for an average of 52 minutes before taking a 17-minute break.

If 52 minutes sounds like a marathon for you, start small with 20 minutes on, five minutes off, and work your way up.

2. Create a "not-to-do" list

Distractions are everywhere in our modern working world. Researchers have found it takes up to 25 minutes to regain your focus after being distracted. One easy fix is to create a "not-to-do" list: Whenever you feel the pull to check Facebook or Twitter or follow any other random thought that comes into your head, write it down instead. The act of simply transferring that thought from mind to paper allows you to stay focused on the task at hand.

3. Read long books slowly

According to research from the Pew Research Center, reading of online content has increased nearly 40 percent. Yet 26 percent of Americans didn't read a single book last year. Reading only short content is killing our ability to focus and training our minds to only look for quick answers rather than explore complex concepts. Start by researching proper ways to read a book and then pick up a classic and give it a shot.

4. Try these turn-of-the-century concentration exercises

Don't think declining attention spans are solely a modern-day issue. In the early 1900s, author Theron Q. Dumont published a book called The Power of Concentration that highlighted a number of practices for building your attention span. Here are a few:

  • Sit still in a chair for 15 minutes

  • Concentrate on slowly opening and closing your fists for five minutes

  • Follow the second hand of a clock for five minutes

They might seem a little crazy, but you'd be surprised how hard these exercises are to do.

5. Bring more mindfulness into your day

Mindfulness is having a moment, with everyone from director David Lynch to Huffington Post founder Arianna Huffington practicing daily meditation. And for good reason: Researchers from the University of Washington have shown that just 10 to 20 minutes of meditation a day can help improve your focus and extend your attention span. What's more, you'll even see improvements in your attention after just four days.

6. Add physical exercise to your attention exercise routine

Working out isn't just good for your body. Researchers have found that adding physical exercise to your routine helps build the brain's ability to ignore distractions. In one study, students who engaged in just moderate physical exercise before taking a test that measured their attention spans performed better than those students who didn't exercise.

7. Practice attentive listening

If there's one place our limited attention span is incredibly noticeable, it's when we're talking to others. Instead of grasping at straws during a conversation, practice attentive listening by not interrupting, recapping what the other person has said regularly, and using connecting words like "OK," "I get it," and "Yes" to stay engaged and show that you're listening.

These skills not only help us come across as nicer, more interesting people, they also help train our minds to focus on the person in front of us.