eating other foods is impractical. It is important to
read product labels carefully.
See also DIET AND HEALTH.
stinger An injury to the brachial plexus, the
large NERVEcluster that branches from the SPINAL
CORDto innervate the shoulder, arm, and hand.
An injury that causes numbness on
both sides of the body suggests SPINAL
CORD damage and requires immediate
medical attention. Only medical per-
sonnel should attempt to move a per-
son who has a possible SPINAL CORD
INJURY.A stinger, also called a burner, is a common
injury in contact sports and occurs when a blow
or intense pressure displaces the neck and the
compresses the cervical nerve roots between the
cervical vertebrae (spinal bones in the neck). The
compression causes symptoms that include sharp
burning or stinging and numbness. Though the
discomfort can be severe, it generally goes away
within minutes. Occasionally symptoms may con-
tinue for up to several weeks. An isolated stinger
leaves no residual damage, though repeated
stingers can cause permanent damage to the
nerves. The injury at the neck affects the shoulder
and arm on the opposite (contralateral) side.
See also ATHLETIC INJURIES; NEURITIS; NEUROPATHY.
strength The ability of a MUSCLEto engage in
physical activity, particularly resistance activity.
Common measures of strength are the abilities to
move weight (such as in weightlifting) or to exert
force against pressure (such as in bicycling or row-
ing). Strength improves through repetitious
actions that generate force against muscle fibers as
they contract and relax, which causes them to
enlarge as well as become more efficient in their
use of oxygen. Muscles exposed to consistent
exercise develop denser networks of capillaries,
facilitating rapid oxygen exchange, and larger
mitochondria capable of expanded functions.
Mitochondria are the “engines” of the cell, per-
forming multiple metabolic tasks that allow cells
to generate and use energy. As muscles become
stronger and larger, they require more challenge
in the form of increased weight or resistance to
maintain their strength.PAIN is a signal that the body has
reached its limit or is injured. Stop a
strengthening activity at the first indi-
cation of pain. Rest five minutes and try
the activity again. If the pain persists,
stop the session and implement relief
measures such as rest and ice to the
area.When exercising with weights it is important to
start at an appropriate level for both the amount of
weight and number of repetitions and work up to
the desired level. Excessive weight can cause injury
and inadequate weight does not challenge the mus-
cles. In general, a person should be able to perform
8 repetitions with a particular weight, feeling some
resistance though no PAINwith each repetition.
When it becomes easy to do 12 to 15 repetitions,
the muscle group is ready for an increase in weight.
At the new weight, start again with 8 repetitions
and increase as the repetitions become easier to
perform. Fewer repetitions with heavier weight
builds muscle mass and increases strength faster
than more repetitions with lighter weight, though
the latter builds ENDURANCE. Specific weight TRAIN-
INGregimens may have different guidelines.
The body itself can become the source of
weight and resistance. Exercises such as curls,
pushups, pullups, and squats use the body’s
weight to generate resistance against movement.
The drawback to these exercises is that body
weight is inflexible as the source of resistance; one
cannot built up to or increase the effect.
Physical activities that use large muscle groups
in repetitious activity also use the body’s weight as
resistance against gravity (such as with walking
and running) or against equipment and gravity
(such as with cycling and rowing). Aerobic activi-
ties such as swimming further tone muscles and
improve AEROBIC CAPACITYthough are not as effec-
tive for strengthening. A person can expect to see
a 20 percent increase in strength after two months
and a 40 percent increase in strength after four to
six months of consistent strength training.
Many factors influence how strong muscles can
become, key among them being regular participa-232 Fitness: Exercise and Health