If there were something you could add to your car's engine, so that after driving it a hundred miles, you'd end up with more gas in the tank than you started with, wouldn't you use it?
Even if nothing like that exists for your car just yet, there is something you can give your employees that will have the same effect ... interesting work.
Now I know what you're thinking. "Finding your work interesting is nice, but the work has to get done, interesting or not." This is the attitude many managers take when they hear complaints from employees about work being too boring, tedious, or difficult. As if interest is a luxury - something that is pleasant but unnecessary, like little chocolates on your hotel pillow.
Interest in work is not a luxury--it is a powerful motivator. In fact, research shows that finding what you do interesting and believing it has inherent value is probably the single best way to stay motivated despite difficulty, setbacks, and unexpected roadblocks.
But as they say in the infomercials, that's not all. A new set of studies  shows that interest doesn't just keep you going despite fatigue, it actually replenishes your energy.
In their studies, psychologists at CSU gave participants a task to work on that was particularly draining, and then varied whether the next task was difficult-but-interesting or relatively easy-but-dull. They found that people who worked on the interesting task put in more effort and performed much better (despite being tired) than those who worked on the boring task--even though it was actually harder than the boring task. In other words, experiencing interest restored their energy and gave them a tangible advantage.
In another study, the researchers found that experiencing interest resulted in better performance on a subsequent task as well. In other words, you don't just do a better job on Task A because you find Task A interesting--you do a better job on follow-up Task B because you found Task A interesting. The replenished energy flows into whatever you do next.
(Incidentally, each of these studies compared the effects of interest and good mood, and found that while people do get some replenishment of energy from being happy, they get much more from being interested in and engaged by what they do.)
If it's your job to make the most of your employees' potential, you would be wise to make their work more interesting -- or, at least find ways of sprinkling some more interesting work here and there throughout the day. But how can you make work more interesting?
One of the surest ways to do so is to give your employees the experience of choice. Research show that self-chosen pursuits create a special kind of motivation called intrinsic motivation--the desire to do something for its own sake. When people feel that they have a hand in directing what they do and how they do it, they enjoy it far more and find it more interesting.
In order to experience a sense of autonomy, your employees need to understand why the goal or project they've been assigned has value. Too often, managers tell their employees what they need to do, without taking the time to explain why it's important, or how it fits into the bigger picture. No one ever really commits to a goal if they don't see why it's desirable for them to do it in the first place.
Allowing your employees the freedom to decide how they will complete an assignment is another way to create the feeling of choice necessary to be intrinsically motivated. Allowing them to tailor their approach to their preferences and abilities will also give them heightened sense of control over the situation they find themselves in, which can only benefit performance.
If that won't work, it turns out that it isn't so much actual freedom of choice that matters when it comes to creating intrinsic motivation and interest, but the feeling of choice, even when that feeling is coming from a choice that's trivial or illusory. Try inviting your employees to make decisions about more peripheral aspects of the work they do. For instance, if they have to go to weekly team meetings to improve coordination -- meetings they usually find boring to attend - you can increase interest by having team members take turns deciding what the topic of the meeting will be each week, or even what kind of lunch will be ordered in. Studies show that these more peripheral decisions create a feeling of choice, and heighten interest, even when the choices aren't particularly meaningful.
Take time to reflect on how you might be able create a greater sense of choice in your own workplace using these methods. You'll make the work more interesting, and wind up with employees that have a lot more gas in the tank.
To learn more about reaching your career goals, check out Heidi's new book is Succeed: How We Can Reach Our Goals . Follow her on Twitter @hghalvorson . Her website is www.heidigranthalvorson.com .