How Exercise Changes Structure And Function Of Heart

How Exercise Changes Structure And Function Of Heart





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.

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"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."
Their study appears in the April Journal of Applied Physiology.
Baggish and senior author Malissa J. Wood, MD, of MGH Cardiology note
that collaboration with the Harvard University Medical 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 Health Services.