MGH study shows how exercise changes
structure and function of heart
Study of Harvard athletes
finds different effect of endurance, strength training
BOSTON - April 22, 2008 - For the first time researchers
are beginning to understand exactly how various forms of exercise
impact the heart. Massachusetts General Hospital (MGH) investigators,
in collaboration with the Harvard
University Health Services, have found that 90 days of vigorous
athletic training produces significant changes in cardiac structure
and function and that the type of change varies with the type of
exercise performed. Their study appears in the April Journal
of Applied Physiology.
"Most of what we know about cardiac changes in athletes and
other physically active people comes from 'snapshots,' taken at
one specific point in time. What we did in this first-of-a-kind
study was to follow athletes over several months to determine how
the training process actually causes change to occur," says
Aaron Baggish, MD, a fellow in the MGH
Cardiology Division and lead author of the study.
To investigate how exercise affects the heart over time, the MGH
researchers enrolled two groups of Harvard University student athletes
at the beginning of the fall 2006 semester. One group was comprised
of endurance athletes - 20 male and 20 female rowers - and the other,
strength athletes - 35 male football players. Student athletes were
studied while participating their normal team training, with emphasis
on how the heart adapts to a typical season of competitive athletics.
Echocardiography studies - ultrasound examination of the heart's
structure and function - were taken at the beginning and end of
the 90-day study period. Participants followed the normal training
regimens developed by their coaches and trainers, and weekly training
activity was recorded. Endurance training included one- to three-hour
sessions of on-water practice or use of indoor rowing equipment.
The strength athletes took part in skill-focused drills, exercises
designed to improve muscle strength and reaction time, and supervised
weight training. Participants also were questioned confidentially
about the use of steroids, and any who reported such use were excluded
from the study.
At the end of the 90-day study period, both groups had significant
overall increases in the size of their hearts. For endurance athletes,
the left and right ventricles - the chambers that send blood into
the aorta and to the lungs, respectively - expanded. In contrast,
the heart muscle of the strength athletes tended to thicken, a phenomenon
that appeared to be confined to the left ventricle. The most significant
functional differences related to the relaxation of the heart muscle
between beats - which increased in the endurance athletes but decreased
in strength athletes, while still remaining within normal ranges.
"We were quite surprised by both the magnitude of changes over
a relatively short period and by how great the differences were
between the two groups of athletes," Baggish says. "The
functional differences raise questions about the potential impact
of long-term training, which should be followed up in future studies."
While this study looks at young athletes with healthy hearts, the
information it provides may someday benefit heart disease patients.
"The take-home message is that, just as not all heart disease
is equal, not all exercise prescriptions are equal," Baggish
explains. "This should start us thinking about whether we should
tailor the type of exercise patients should do to their specific
type of heart disease. The concept will need to be studied in heart
disease patients before we can make any definitive recommendations."
Baggish and senior author Malissa J. Wood, MD, of MGH Cardiology
note that collaboration with the Harvard University Health Services,
led by Francis Wang, MD, was instrumental in the success of this
study. Additional co-authors of the report are Rory Weiner, MD,
Jason Elinoff, Francois Tournoux, Michael Picard, MD, and Adolph
Hutter, MD, MGH Cardiology; and Arthur Boland, MD, Harvard University
Massachusetts General Hospital, established in 1811, is the original
and largest teaching hospital of Harvard Medical School. The MGH
conducts the largest hospital-based research program in the United
States, with an annual research budget of more than $500 million
and major research centers in AIDS, cardiovascular research, cancer,
computational and integrative biology, cutaneous biology, human
genetics, medical imaging, neurodegenerative disorders, regenerative
medicine, systems biology, transplantation biology and photomedicine.
Media Contacts: Sue
McGreevey, MGH Public Affairs
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