CHAPTER 10 • MUSCLE AND TENDON INJURY AND REPAIR 57may delay complete healing of the muscle tissue
(Nikolaou et al, 1987; Obremsky et al, 1994). The
indication for the use of these drugs in muscle strain
injury is unclear.- Cryotherapy provides an analgesic effect but its effect
on inflammation is unclear (Noonan and Garrett, Jr,
1999).
MUSCLESTRENGTHENING
- Muscle strengthening is an important factor in the
recovery of injured muscle and the prevention of rein-
jury. - Basic science research has demonstrated that fatigued
muscle has decreased load to failure and energy
absorption than control muscle tissue (Mair et al,
1996). These data would support the belief that the
athlete with a muscle strain injury should not return to
competition until complete muscle strength and con-
ditioning have returned.
MUSCLESTRETCHING ANDWARM-UP
- Muscle is viscoelastic material, and passive stretching
can reduce stress for a given muscle length (Taylor
et al, 1990). In addition, preconditioned muscle and
muscle that is warm fails at higher loads than control
muscle (Safran et al, 1988). These studies suggest the
importance of stretching and warm-up in the preven-
tion of muscle strain injury.
•A recent review of clinical and basic science literature
questions the above conclusions and states that
stretching prior to exercise does not prevent injury and
may make the muscle more susceptible to injury
(Shrier, 1999). Additional studies are needed before
definitive conclusions can be made.
DELAYED MUSCLE SORENESS
- Delayed muscle soreness is defined as skeletal muscle
pain 24–72 h after unaccustomed physical activity.
The pain lasts approximately 5–7 days and can range
from mild soreness to severe discomfort (Armstrong,
1984). Loss of muscle strength, loss of joint range of
motion, tenderness, and elevated muscle enzymes are
also present. - Strength loss can be explained by both the presence of
pain and a decrease in the inherent force-producing
capacity of the muscle fibers (Armstrong, 1984). - No permanent muscle injury occurs and complete
muscle recovery is seen within 14 days. - Delayed muscle soreness occurs most commonly in
muscles performing eccentric activity and is related to
both the intensity and duration of activity.
PATHOPHYSIOLOGY- High tension over a small cross-sectional area (seen in
eccentric muscular contraction) results in cytoskeletal
disruption. - Sarcolemma (cell membrane) disruption results in an
influx of intracellular Ca2+ that induces proteolytic
enzyme mediated myoprotein degradation (Armstrong,
1984). - Cellular damage results in the activation of inflamma-
tory processes. This stimulates nociceptors within the
muscle resulting in the production of pain
(Armstrong, 1984).
TREATMENT ANDPREVENTION- Further exercise appears to be the most effective
method of diminishing the symptoms of delayed
muscle soreness. This is most likely owing to exer-
cise-induced production of endorphins or other alter-
ations in neural pathways (Armstrong, 1984). - Delayed muscle soreness diminishes with repetition
of exercise. The reasons for this are unclear. There is
still continued muscle tissue damage with repetitive
exercise but to a progressively lesser extent. The dis-
comfort associated with this tissue damage, however,
is greatly diminished. - Nonsteroidal anti-inflammatory drugs demonstrate
similar effects in an exercise-induced muscle injury
model as they do in other muscle injury models. There
is early benefit to the muscle by limiting inflammation
but the later negative effects on maximum muscle
function mitigate this (Mishra et al, 1995).
MUSCLE CONTUSION INJURY- Muscle contusions are common injuries in collision
and contact sports. These injuries most frequently
involve the lower extremity muscle groups, such as
the quadriceps, gastrocnemius, or anterior muscles of
the lower leg (Best, 1997). - The initial clinical presentation includes pain,
swelling, loss of joint range of motion, and the possi-
bility of a palpable muscle defect. This can be fol-
lowed by persistent swelling and warmth, a firm mass,
and continued loss of motion. - Animal studies of muscle contusion injury demonstrate
muscle fiber rupture resulting in hematoma formation,
edema, and inflammation (Walton and Rothwell, 1983).
REPARATIVERESPONSE- Similar to the general process of muscle healing
described above; however, there appears to be less
scar formation with a muscle contusion injury than
with a muscle strain injury.