L–N

lean muscle mass The amount of body tissue
that is lean MUSCLEin contrast to the percentage
that is body fat. There is an inverse relationship
between lean muscle mass andBODY FAT PERCENT-
AGE, such that when one increases the other
decreases. Lean muscle mass increases with regu-
lar physical exercise that challenges muscle fibers
to expand. Serious illness or injury, such as signifi-
cant BURNSor major trauma, may draw protein
from lean muscle mass to aid in HEALING, resulting
in diminished lean muscle mass. A common
method for estimating lean muscle mass is UPPER
ARM CIRCUMFERENCE, a measurement of the distance
around the middle of the upper arm. It is also pos-
sible, though less accurate, to approximate lean
muscle mass based on body fat percentage deter-
minations. The X-RAYprocedure dual-energy X-
ray absorptiometry (DEXA), a diagnostic test that
measures BONE DENSITY, also provides data for cal-
culating lean muscle mass.
See also BODY MASS INDEX(BMI); RESISTANCE EXER-
CISE; WAIST CIRCUMFERENCE; WAIST TO HIP RATIO.

nicotine replacement Products intended to
wean a person from NICOTINEotherwise acquired
through cigarette smoking. Nicotine is a highly
addictive DRUGthat occurs naturally in tobacco.
Though behavior is an important component of
smoking, the addictive quality of nicotine
accounts for the difficulty people have in quitting.
Nicotine replacement can be fairly effective as an
aid for SMOKING CESSATION. The premise is that the
nicotine in the product, though less than that in a
cigarette, fulfills the body’s desire for nicotine
when the person stops smoking.
Most nicotine replacement products come in
diminishing strength doses so over the course of a
typical smoking cessation program (usually 12

weeks) the person takes decreasing doses to ease

the body’s dependence on the nicotine. Nicotine

replacement products include

• transdermal (SKIN) patches, which a person
  wears for 16 to 24 hours to deliver a steady
  trickle of nicotine absorbed through the skin


• chewing gums, which deliver doses of nicotine
  with timed chewing and holding the gum
  between the gum and cheek for absorption of
  the released nicotine through the tissues of the
  MOUTHand into the BLOODcirculation


• lozenges, which release nicotine as they dissolve
  in the mouth for absorption through the tissues
  of the mouth and into the blood circulation


• nasal sprays, which deliver nicotine to the
  membranes inside the NOSEfor rapid absorption
  into the blood circulation


• inhalers, small plastic mouthpieces that hold
  cartridges containing nicotine a person draws in
  through the mouth similar to smoking a ciga-
  rette; nicotine enters the blood circulation by
  absorption through the tissues of the mouth
  (not the LUNGS)

Taking NICOTINE replacement products

in combination with one another or

while still smoking cigarettes presents a

major risk for nicotine toxicity. Symp-

toms of nicotine overdose include

• PALPITATIONS
  
  
  • rapid or irregular HEART RATE
  
  
  • NAUSEA
  
  
  • DIARRHEA
  
  
  
  

Nasal sprays and inhalers require a doctor’s

prescription. Transdermal patches and chewing

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