Journal of Gerontology:
2000, V ol. 55A , No. 3, B152–B157
BIOL OGICAL SCIENCESCopyright 2000 by The Gerontological Society of America
Effects of Strength Training and Detraining on Muscle
Quality: A ge and Gender Comparisons
F. M. Ivey,
B. L. Tracy,
J. T. Lemmer,
M. NessA iver,
E. J. Metter,
J. L. Fozard,
and B. F. Hurley
Department of Kinesiology, University of Maryland, College Park.
University of Maryland School of Medicine, Baltimore V A Medical Center, Baltimore.
Department of Kinesiology and A pplied Physiology, University of Colorado, Boulder.
The Jean Mayer USDA Human Nutrition Research Center on A ging at Tufts University, Medford, Massachusetts.
National Institute on A ging, Gerontology Research Center, Baltimore, Maryland.
Florida Geriatric Research Program, Morton Plant Mease Health Care, Clearwater.
Maximal force production per unit of muscle mass (muscle quality, or MQ) has been used to describe the relative
contribution of non-muscle-mass components to the changes in strength with age and strength training (ST). To
compare the influence of age and gender on MQ response to ST and detraining, 11 young men (20–30 years), nine
young women (20–30 years), 11 older men (65–75 years), and 11 older women (65–75 years), were assessed for
quadriceps MQ at baseline, after 9 weeks of ST, and after 31 weeks of detraining. MQ was calculated by dividing
quadriceps one repetition maximum (1RM) strength by quadriceps muscle volume determined by magnetic resonance
imaging. All groups demonstrated significant increases in 1RM strength and muscle volume after training (all
.05). All groups also increased their MQ with training (all
greater in young women than in the other three groups (
mained significantly elevated above baseline levels in all groups (
indicate that factors other than muscle mass contribute to strength gains with ST in young and older men and
women, but those other factors may account for a higher portion of the strength gains in young women. These fac-
tors continue to maintain strength levels above baseline for up to 31 weeks after cessation of training in young men
and women, and in older men.
.01), but the gain in MQ was significantly
.05). After 31 weeks of detraining, MQ values re-
.05), except the older women. These results
secondary to declines in muscle mass (1,2), neuromus-
cular function (1,2), and mechanical and contractile proper-
ties of muscle (3). In addition, changes in architectural com-
ponents such as increases in connective tissue (4) and
decreases in muscle fiber pennation angles are associated
with aging, and therefore likely contribute to strength loss
with age. Many of these non-muscle-mass components of
strength loss are reversed with strength training (ST) (5–7).
Thus, although muscle mass is an important determinant of
strength loss with age and strength gain with ST, it is clearly
not the only factor involved. Alterations in the neuromuscu-
lar, mechanical, contractile, and architectural components
can affect the quality of skeletal muscle. The importance of
studying muscle quality (MQ) with age was emphasized by
a panel of experts at the 1996 National Institute on Aging
workshop “Sarcopenia and Physical Performance in Old
Age,” during which it was concluded that there is a need for
“more comprehensive evaluations of muscle quality using
noninvasive methods” (8). In this regard, we recently re-
ported age-related losses in MQ (9), and gains in MQ with
ST (10) in older men and women. However, we are aware
of only one investigation that has attempted to study the ef-
fects of age on the MQ response to ST (11). Furthermore,
no previous study has reported age and gender comparisons
of the MQ response to the same ST and detraining program.
Although the effects of ST on MQ have previously been
studied (11–14), the measurement of the total volume of the
in muscular strength with age are thought to be
entire trained musculature to determine MQ responses had
not been utilized prior to our recent report (10). This is an
important methodological consideration for the assessment
of MQ because previous estimates of hypertrophy based on
a single cross-sectional image (12,15–18) may not be repre-
sentative of hypertrophy at other locations along the length
of the muscle (14,19,20).
Regardless of methodology, we are unaware of any re-
ports that have assessed MQ changes following the cessa-
tion of a training stimulus (detraining). Exploring the ques-
tion of whether age or gender affect the rate at which MQ
adaptations are lost after detraining addresses the important
issue of how a decline in muscular activity contributes to
the age-related loss of MQ.
Hence, the purpose of this study was to make direct age
and gender comparisons of the MQ response to ST and de-
training, using identical protocols for all groups. This infor-
mation will help to clarify the extent to which factors other
than muscle mass influence strength gains and losses in
young and older men and women.
Eleven young men (20–30 years), nine young women
(20–30 years), 11 older men (65–75 years), and 11 older
women (65–75 years) volunteered to participate in a 9-week
unilateral ST program followed by a 31-week detraining
by guest on December 28, 2015
STRENGTH TRAINING AND MUSCL E QUAL ITY B157
ruptions in regularly performed ST exercise may not result
in complete loss of ST-induced improvements in muscle
function. Furthermore, these losses do not appear to be af-
fected by age or gender, whether expressed in absolute or
Although mechanical and architectural factors cannot be
completely ruled out, it is more plausible that neuromuscu-
lar factors may account for the MQ increases with ST in all
groups (25–28). Young and colleagues (25) acknowledged
that the mechanism for training-induced increases in MQ is
unknown, but that increases in motor unit recruitment are
likely to be involved. Hakkinen and colleagues (26) made
similar conclusions with reference to the strength gains that
are independent of hypertrophy during the first few weeks
of ST. However, they also observed significant decreases in
the coactivation of the antagonist muscle groups following
training in the elderly, which could also explain increases in
MQ. Moreover, a ST-induced transformation of type II
muscle fiber subtypes (from type IIb to IIa) has been re-
ported in young and older men (27). To what extent, if any,
this latter adaptation explains MQ increases is unclear, but
there appears to be substantial support for the involvement
of some type of neuromuscular adaptation that enhances
contractile properties in the explanation of increased MQ
with ST (25–28). Nevertheless, we were unable to find any
potential mechanisms that would explain why women, par-
ticularly young women, might increase their MQ to a
greater extent than men in response ST.
In summary, ST increases MQ regardless of age or gen-
der, indicating that strength gains were beyond that which
can be explained by muscle mass gains. Young women ex-
perienced a larger gain in MQ with ST than did the other
three age and gender groups. Finally, all groups, except
older women, retained ST-induced increases in MQ for at
least 31 weeks after the cessation of training.
A cknowl edgm ents
The authors thank Dr. Barbara Albert, Dan Barlow, Diane Hurlbut, Greg
Martel, Steve Roth, Mary Lott, Dorothy O’Donell, Gerianne Tobak, and
Margie Cohen for their contributions to this research project. This study
was supported by research contract 1-AG-4-2148 from the National Insti-
tute on Aging.
Address correspondence to Ben Hurley, PhD, Department of Kinesiol-
ogy, University of Maryland, College Park, MD 20742. E-mail: bh24@
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Received January 15, 1999
Accepted August 10, 1999
Decision Editor: Jay Roberts, PhD
by guest on December 28, 2015