Functional effects of relative preservation of maximal eccentric muscle torque in aging.

Specific forms of maximal voluntary torque of the lower extremity muscles
declines with age by as much as 60%. Curiously, one form of maximal voluntary
torque generated by muscle when it lengthens, declines only about 20-30%
compared with other expressions of maximal voluntary torques generated by
muscle when its length does not change (isometric) or when it shortens
(concentric contraction). The literature refers to this diminished age-related
loss of torque during lengthening or eccentric contraction as *the relative
maintenance of maximal eccentric torque* (RELM).
While it is a key challenge to identify the mechanism of RELM, such work
becomes only relevant if it is possible first to provide experimental evidence
for the functional benefits of RELM in aging. Therefore, this study addresses a
fundamental issue whether or not RELM is of functional significance. Indirect
evidence points toward the tenability of the overall hypothesis of the present
project that RELM does indeed afford functional benefits to old adults. For
example, it is well established that old adults execute several forms of
activities of daily living (ADLs) near their maximal abilities. If one performs
a daily task at a lower fraction of the maximal available capacity, the effort
to complete the target task would be lower and the activity could be maintained
for longer time without fatigue. The prediction is that individuals who exhibit
high levels of RELM would have functional benefits because the high RELM would
allow these individuals to execute the tasks at a lower fraction of the
maximum, ultimately resulting in safer locomotion.
An important area to identify functional benefits of RELM is locomotion tasks
such as level walking, stair ascent, and stair descent because most falls occur
during locomotion tasks. But also during high demanding tasks like chair rise
and lowering into a chair.

The primary aim of this study is to determine the functional effects of RELM in
healthy older males and females. The secondary objective of this study is to
determine if there is a gender effect present in the level of RELM in older
adults.

This observational study consists of one session in which every subject
performs maximal voluntary strength tests of the quadriceps- and ankle muscles
and twice five functional tasks.

The subjects will visit the Center for Human Movement Sciences once. The
subjects will produce maximal muscle strength several times (during concentric,
isometric, and eccentric contractions) of their legs. The risks will be
comparable to those in daily life. The subjects can rest between the maximal
force efforts and the functional tasks if necessary.