Covering, Support, and Movement of the Body
Mr. Ahmadi, an out-of-shape 45-year-old man, was advised by
his physician to lose weight and to exercise on a regular basis.
He followed his diet faithfully and began to jog daily. One day,
while on his morning jog, he heard a snapping sound that was
immediately followed by a severe pain in his right lower calf.
When his leg was examined, a gap was seen between his swollen
upper calf region and his heel, and he was unable to plantar ﬂex
that ankle. What do you think happened? Why was the upper
part of his calf swollen?
As Peter watched Sue walk down the runway at the fashion
show, he contracted his right orbicularis oculi muscle, raised his
arm, and contracted his opponens pollicis. Was he pleased or
displeased with her performance? How do you know?
What type of lever system do the following activities describe? (a)
Te soleus muscle plantar ﬂexes the foot. (b) Te deltoid abducts
the arm. (c) Te triceps brachii is strained while doing pushups.
(e) muscles of mastication, (f) third muscle layer of the foot,
(g) posterior compartment of leg, (h) medial compartment of
thigh, (i) posterior compartment of thigh.
and Clinical Application
Assume you have a 10-lb weight in your right hand. Explain why
it is easier to ﬂex the right elbow when your forearm is supinated
than when it is pronated.
When Mrs. O’Brien returned to her doctor for a follow-up visit
aFer childbirth, she complained that she was having problems
controlling her urine ﬂow (incontinent) when she sneezed. Te
physician asked his nurse to give Mrs. O’Brien instructions on
how to perform exercises to strengthen the muscles of the pelvic
ﬂoor. ±o which muscles was he referring?
Related Clinical Terms
A muscle contusion, i.e., tearing of muscle followed by
bleeding into the tissues (hematoma) and severe, prolonged pain.
A common contact sports injury; football players frequently
suﬀer a charley horse of the quadriceps muscle of the thigh.
Recording and interpretation of graphic records
of the electrical activity of contracting muscles. Electrodes
inserted into the muscles record the impulses that pass over
muscle-cell membranes to stimulate contraction. Te best and
most important technique for determining the functions of
muscles and muscle groups.
An abnormal protrusion of abdominal contents (typically
coils of the small intestine) through a weak point in the muscles
of the abdominal wall. Most oFen caused by increased intra-
abdominal pressure during liFing or straining. Te hernia
penetrates the muscle wall but not the skin and so appears as a
visible bulge in the body surface. Common abdominal hernias
include the inguinal and umbilical hernias.
Quadriceps and hamstring strains
Also called quad and hamstring
pulls, these conditions involve tearing these muscles or their
tendons; happen mainly in athletes who do not warm up
properly and then fully extend their hip (quad pull) or knee
(hamstring pull) quickly or forcefully (e.g., sprinters, tennis
players). Not painful at ﬁrst, but pain intensiﬁes within three to
six hours (30 minutes if the tearing is severe). AFer a week of
rest, stretching is the best therapy.
Ruptured calcaneal tendon
Although the calcaneal (Achilles)
tendon is the largest, strongest tendon in the body, its rupture
is surprisingly common, particularly in older people as a
result of stumbling and in young sprinters when the tendon is
traumatized during takeoﬀ. Te rupture is followed by abrupt
pain; a gap is seen just above the heel, and the calf bulges as the
triceps surae are released from their insertion. Plantar ﬂexion
is weak or impossible, but dorsiﬂexion is exaggerated. Usually
Common term for pain in the anterior compartment
of the leg caused by irritation of the tibialis anterior muscle as
might follow extreme or unusual exercise without adequate
prior conditioning. Because it is tightly wrapped by fascia, the
inﬂamed tibialis anterior cuts oﬀ its own circulation as it swells
and presses painfully on its own nerves.
±enderness due to trauma or overuse of the tendon of
origin of the forearm extensor muscles at the lateral epicondyle
of the humerus. Caused and aggravated when these muscles
contract forcefully to extend the hand at the wrist—as in
executing a tennis backhand or liFing a loaded snow shovel.
Despite its name, tennis elbow does not involve the elbow joint;
most cases caused by work activities.
twisted) A twisting of the neck in
which there is a chronic rotation and tilting of the head to one
side, due to injury of the sternocleidomastoid muscle on one
side; also called wryneck. Sometimes present at birth when the
muscle ﬁbers are torn during diﬃcult delivery. Exercise that
stretches the aﬀected muscle is the usual treatment.
AT T H E C L I N I C