For example, a study conducted at Virginia Polytechnic Institute and presented in Psychology Today divided female undergraduate students into two groups and had the students perform as many sit-ups as possible in 90 seconds.

The first group was told only to “Do your best,” while the second group was told to try to increase the actual number of sit-ups done each day by 10%.

After four days:

• “Do your best” group -- averaged 43 sit-ups
• Increase 10% group -- averaged 56 sit-ups 

The conclusion then was that athletes who were given specific goals performed better than those who were not given specific goals.