Ontario researchers have found that simple modifications to pushups can be used to make the common exercise far more effective in targeting different muscle groups depending on a person's goals.

Clark Dickerson, a kinesiology professor at the University of Waterloo, and his team looked at the "pushup plus" -- a regular pushup with a move to push the shoulder blades apart at the end -- and variations of that exercise.

"The beauty of it is with fairly simple modifications you can get very targeted results with an exercise that most people can do fairly readily," Dickerson said. "If you are looking to emphasize or de-emphasize muscular training or strengthening using one exercise that can be modified, it's a good one to do that."

Dickerson said the research was triggered when one his students, Andrew Ho, wanted to know what sorts of variations on the classic exercise could help those with shoulder problems.

The pushup plus has long been held to activate the serratus anterior muscle, which starts on the inside of the shoulder blade on the spine and wraps around the rib cage, Dickerson said, but little research exists about the alterations of body posture that could help activate different muscles.

A weak serratus can lead to "winging," he said, where the shoulder blade lifts off the rib cage.

"That's associated with a lot of arm control problems and pain in the shoulder," Dickerson said.

Dickerson's team took 20 healthy, young men -- none with shoulder problems -- and ran them through a gamut of pushup plus alterations while recording electromyography results, which track the electrical activity produced by muscles.

They studied various pushup positions: hands above the head or lower than the head, hands rotated toward the body or away from the body, and on flat palms or on knuckles.

The team found that certain combinations of those moves can be "stacked" on each other and result in greater muscle activation.

For example, Dickerson said, researchers discovered that if someone wants to focus on developing their triceps, they'll get the best muscle activation when doing the pushup plus on their knuckles with hands above their heads and hands pointed toward the body.

The research also suggests the best type of pushup to target biceps involves a person doing the exercise on their knuckles, with fingers away from the body and their hands positioned lower than their head.

One potential follow up study, Dickerson said, is to work with physiotherapists to see how using such pushup variations can help people with shoulder problems.

"Breast cancer survivors is a very big group of patients who have really pronounced decrease in shoulder function," Dickerson said.

He noted the modifications can also help athletes who want to strengthen the muscles involved in proper shoulder rotation, especially tennis serves and golf swings.

Dickerson's research is published in the February issue of the Journal of Electromyography and Kinesiology.