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Why rowers have bigger hearts

08/08/2008

Scientists believe they have discovered why elite rowers have bigger, stronger hearts.

The Italian researchers believe the clue lies in naturally-occurring hormone levels that strengthen the heart muscle.

In their study they found that professional rowers have higher levels of insulin-like growth factor 1 (IGF-1) compared to healthy, inactive volunteers.

Writing in the journal Clinical Endocrinology the researchers argue that the higher IGF-1 levels are linked with enlargement and strengthening of heart muscle cells.

They studied circulating IGF-1 levels in blood samples from 19 top-level male rowers and 19 age-matched healthy sedentary controls.

Each subject also had their cardiac structure and function measured.

As well as the higher IGF-1 levels, the study revealed that the rowers' hearts were also much larger, showing increased cavity dimensions, increased wall thickness, and enhanced muscle function, in both the left and right sides of the heart, compared to controls.

The researchers claim their findings provide clues as to how the body responds and adapts to prolonged physical exercise.

"These results highlight a possible biochemical mechanism for cardiac hypertrophy [growth] in elite rowers and suggest a potentially beneficial role for IGF-1 in the remodelling of the heart muscle," said researcher Dr Giovanni Vitale from the University of Milan.

"This could mean that naturally increased production of IGF-1, occurring as an adaptation to prolonged training, influences biochemical processes that control contraction of the heart muscle in rowers.

"Further research is now needed to determine the exact relationship between higher production of IGF-1 and cardiac output in elite rowers."