Aerobic exercise training improves whole muscle and single myofiber size and function in older women

Matthew P. Harber, Adam R. Konopka, Matthew D. Douglass, Kiril Minchev, Leonard A. Kaminsky,
Todd A. Trappe, and Scott Trappe
Human Performance Laboratory, Ball State University, Muncie Indiana

The benefits of aerobic exercise on cardiovascular and metabolic
health in older adults have been well established (31).
Our findings extend these benefits and provide evidence, for
the first time, that progressive aerobic exercise training can
elicit robust improvements in muscle size and performance in
healthy older women. Although adaptations at the whole muscle
level (size and function) were similar to resistance traininginduced
adaptations in this subject population, it appears that
aerobic training results in qualitative changes in muscle composition,
namely, increases in water content and a reduction in
myofibrillar protein concentration that are not typically observed
with resistance training. Additionally, aerobic training
appears to remodel the contractile characteristics at the cellular
level (i.e., increased contraction velocity and reduced normalized
force) in conjunction with myofiber hypertrophy, mostly
of the slow myofibers, to achieve an enhanced power production.
These data provide novel insights into the regulation of
muscle plasticity by physical activity in older adults. Further,
these findings identify aerobic exercise training as a viable
option for improving muscle mass and function in older adults.

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