Rehabilitation-Muscular Endurance
Jennifer A. Stone, MS, ATC, Column Editor
HE ABILITY to repeatedly contract a
muscle against submaximal loads is
called muscular endurance. It lies at
the opposite end on the continuum
of muscular strength, the ability to lift a maximal load for a specific number of repetitions.
Muscular endurance exercises can, but
need not, develop aerobic capacity. Exercises
for muscular endurancemay have such a low
resistance level that they apply enough muscular stress to increase muscular endurance
but not enough to stress the cardiovascular
system through large muscle activity.
Development of muscular endurance
overlaps that of muscular strength, especially
at the beginning of a rehabilitation program.
Muscular endurance is third on the rehab
continuum simply because post-op or postimmobilization athletes must regain range
of motion and minimal strength in order to
undertake muscular endurance exercise.
Because of differing purposes, some rehab
programs focus more on muscular endurance than strength while others may be the
reverse.
Muscular endurance is most important in
postural muscles and those that maintain
joint stability. Some stability muscles, such
as the rotator cuff, are small and cannot
handle large resistance loads. If larger loads
are applied to these muscles, the recruitment
patterns change, causing larger muscles to
substitute for those the athlete is really trying to exercise.
The athletic therapist must be cognizant
of these substitution patterns in order to determine the appropriate resistance, number
of reps, and number of sets for optimal development of muscular endurance.
Development of muscular endurance in
the lower extremity generally begins with
low weight-bearing or nonimpact exercises
such as stationary bicycling (see photo),
pool walking in chest-deep water, or stairstepping on a pedal machine. The duration
of exercise is gradually increased, as is the
resistance. With bicycles and stair steppers,
the machine resistance is increased. In pool
walking, the water depth is decreased, forcing the legs to handle more body weight.
Additionally, cadence in all exercises can
be increased.
Eventually these exercises for muscular
endurance become strenuous enough to
stress the cardiovascular system. At this
point they become aerobic, cardiovascular
exercises as well as muscular endurance
exercises.
Muscular endurance exercises for the
upper extremity are more diverse and may
be more specific to a joint. The rotator cuff
musculature is critical to stability of the
glenohumeral joint and contracts whenever
O 1998 Human Kinetics
July 1998
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that joint is moved. Obviously
that muscle group requires great
levels of muscular endurance.
Additionally, there are sports
such as swimming, wrestling, and
judo that require extensive, constant use of the upper extremity
in a fashion similar to the way the
lower extremity is used in running-type sports. Upper body
ergometry and rowing, for example, are appropriate muscular
enduranceexercises for conditioning the entire upper extremity.
Just as with the lower extremity, as time and intensity increases,
these exercises also become aerobic and cardiovascular.
Postural exercises for the
trunk promote endurance and
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stability of a very key area. Both
upper and lower extremities
must have a stable base to operate from, in other words, a stable
trunk. This is called core stability.
Of the many components to
core stability, one is adequate
muscular endurance to hold and
maintain low level contractions
without fatiguing. This is the
basis for recommending high
repetitions and modifications of
abdominal and back exercises.
These muscles also need high
levels of muscular strength to
withstand forces that could
move the body out of balance.
With the exception of rotator
cuff and trunk exercises, muscular endurance exercises are large
Aglhieals Thempy Today
muscle exercises which overlap
into the development of aerobic,
cardiovascular conditioning as
conditioning increases. Rotator
cuff exercises are generally prescribed with low resistance, few
sets, perhaps as few as one, and
high repetitions, perhaps as
many as 100.
Trunk exercises, especially
abdominal ones, are performed
in similar fashion. All exercise
regimens are designed to isolate
particular muscles for extensive
rehabilitation and apply enough
stress to develop muscular endurance. Eventually they may go
beyond that to develop aerobic,
cardiovascular endurance.
a&2#
July 1998