Some Muscles Respond To Weight Training In Just Two Weeks

July 27, 1998

ATHENS, Ohio -- If you've just begun a weight training program and are discouraged by the lack of a bulging biceps, take heart: Even though changes aren't visible in a mirror, researchers at Ohio University and Pennsylvania State University have found the changes are visible under a microscope.

Exercise physiologists at the two institutions have found that molecular changes in the muscle begin within two to four weeks of initiating resistance training, far earlier than previously thought. What's more, the muscles appear to respond to even limited weight training. Scientists found significant changes in the thigh muscles after just four workouts

"When most people begin a training program, they want to see immediate changes," said Robert Staron, associate professor of anatomy at Ohio University and co-author of this new study. "Our study suggests there are changes happening within the muscle which take place within a relatively short amount of time, even if they're not outwardly visible."

The activities the researchers monitored -- changes in hormone production and protein expression -- precede the increase in muscle mass longed for by beginning exercise enthusiasts.

"In the early phase of weight training, the body is adjusting its various systems to prepare you to become a stronger and more capable organism and it's these changes that we've found are happening at a much faster pace than anyone thought," said William Kraemer, professor of applied physiology at Pennsylvania State University and co-author of the study.

Thirty-three Ohio University students were recruited for the study. None were involved in a resistance training program at the onset of the project. Participants met with researchers five times every two weeks; four sessions were spent on weight training for the lower body and one was spent on strength testing for the lower body.

Resistance training focused on the quadriceps. Although the sessions lasted about two hours each week, the muscles actually were working only about 30 minutes a week, Staron said.

When they compared blood and tissue samples taken before training with those taken every two weeks during the eight-week program, researchers saw changes in production of testosterone, growth hormone and other chemicals as well as changes in the expression of myosin, the most common protein in muscles.

"There's a hormonal milieu that's bathing the muscle and it has a dramatic effect on the growth of the muscle," Staron said.

Women produce more growth hormone than men and the exercise program didn't seem to change that, Staron said. But the researchers did see startling differences between the testosterone response to exercise in men and women. Researchers suspect testosterone plays a role in muscle growth, but determining this is difficult. In this study, resistance training caused testosterone levels to increase significantly in both men and women when measured before, immediately following and five minutes after a workout.

However, the testosterone changes in the women were more dramatic compared to the men: Female participants saw a doubling in their testosterone levels. What's more, researchers recorded significant changes in the production of sex-hormone binding globulin (SHBG), a protein that binds with testosterone, helping transport it though the blood to the muscle cell.

"One possibility is that, in the women, SHBG is more active to protect what little bit of testosterone is produced during exercise," Kraemer said. "But it's likely that all of these hormones are involved with the repair process for the muscles, which are under stress at the beginning of a resistance training program."

This repair process makes the muscles more resistant to further injury and more responsive to the benefits of resistance training, Staron said.

"The muscle is a very adaptable tissue," he said. "The fact that we see these responses so early in training that only focused on one muscle group suggests that a whole-body workout might produce an even greater hormonal response."

The study is one of several resulting from a longtime collaboration between exercise physiologists at Ohio University and Kraemer, who in August will start a new position as professor and director of the Human Performance Laboratory at Ball State University.

The research was published in the June issue of the European Journal of Applied Physiology and was funded in part by the Ohio Board of Regents Research Challenge Program, Ohio University's College of Osteopathic Medicine and the Robert F. and Sandra M. Leitzinger Research Fund in Sports Medicine at Pennsylvania State University.

In addition to Staron, Ohio University co-authors include Fredrick Hagerman, professor of physiology, and Robert Hikida, professor of anatomy, all in the College of Osteopathic Medicine. Other authors were Andrew Fry, Scott Gordon, Bradley Nindl, Lincoln Gothshalk, Jeff Volek and James Marx, all from Pennsylvania State University; Robert Newton from Southern Cross University in Australia; and Keijo Hakkinen from the University of Jyvaskyla in Finland.

Written by Kelli Whitlock

Ohio University

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