Sports Medicine: Just the Facts

SPECIFIC APPLICATIONS

TRANSCUTANEOUSELECTRICALNERVE
STIMULATORS

• It is clear that transcutaneous electrical nerve stimu-
  lators (TENS) stimulation produces localized analge-
  sia, and research suggests that stimulation at 110 Hz
  (as well as HWT at 2 and 60 Hz) results in a hypoal-
  gesia that persists for up to 5 minutes after stimulation
  is stopped (McDowell et al, 1999)


• Dorsal horn cell activity is reduced following stimula-
  tion (Garrison and Foreman, 1996).


• High frequency, low intensity TENS (barely or not
  perceptible, 10 to 100+Hz) may work more according
  to the gate theory than higher intensity low frequency
  (1 to 4 Hz) stimulation, which may be more depend-
  ent on endorphins.


• Electrodes are usually placed over the painful region,
  but other locations are common.


• TENS units are expensive (often as much as $800) and
  annoying to put on. Benefits may appear to wane with
  time; purchase is not warranted unless its improve-
  ments persist for several months.

TENS INDICATIONS
•Pain reduction

PRECAUTIONS ANDCONTRAINDICATIONS

• Skin irritation and contact dermatitis?


• Cardiac pacemakers may be relatively resistant to
  TENS signals, but there is at least one report that an
  intracardiac defibrillator was triggered by a TENS
  unit (Curwin, Coyne, and Winters, 1999).


• The pregnant uterus should not be treated.

FUNCTIONAL ELECTRIC STIMULATION

MUSCLESTIMULATION

• In summary, electrical muscle stimulation is more
  effective in maintaining muscle mass after an injury
  than it is in reversing atrophy once it is established
  (Baldi et al, 1998).

IONTOPHORESIS

• Iontophoresis uses electrical fields to force charged or
  polarized substances into tissue (Chantraine, Ludy,
  and Berger, 1986; O’Malley and Oester, 1955; Hill,
  Baker, and Jansen, 1981).


• Iontophoretic devices consist basically of a direct-current
  (possibly pulsed) power source and two electrodes. A
  dilute solution of the active substance (which must exist
  in an ionized or polar form) is placed under the electrode
  of the same polarity, and the device is turned on.
  
  
  • Medication is not always required as the electric cur-
    rent alone may have therapeutic benefits.
  
  
  • Despite generalization to materials other than analgesics
    and rather widespread use, including use in tendonitis,
    bursitis, and sprains, research support is limited.
  
  
  • Nonsteroidal anti-inflammatory iontophoresis of lateral
    epicondylitis may be helpful (Demirtas and Oner, 1998).
  
  
  • Direct comparison of iontophoresis with oral medica-
    tion, transdermal patches, or alternative physical ther-
    apy approaches is rare.
  
  
  • Safety:Allergies to the materials (pads, electrodes,
    and medication) used are always possible, and the
    passage of electrical current into the skin can cause
    erythema, rashes, and, if the current intensity is high,
    pain (Berliner, 1997).
  
  
  • Wound healing:Low-frequency microcurrent (e.g.,
    10 to 200 Hz, <10 mA/cm^2 ) electric currents and fields
    designed to accelerate wound healing by neutralizing
    injury currents or reducing free radical concentrations
    have gained some notice (Barron, Jacobson, and Tidd,
    1985).
  
  
  
  

INTERFERENTIAL ANDKILOHERTZ

FREQUENCYCURRENTS

• Skin impedance falls as frequency increases. As a
  result, stimuli that are painful at the low <70-Hz fre-
  quencies of TENS and many muscle simulators are
  well tolerated at a few thousand hertz.


• There are at least two ways to take advantage of this
  fact. One of these arranges two sets of electrodes so
  that two sine waves in the low-kilohertz range differ-
  ing by 20 to 100 Hz cross. The waves thus interfere
  with each other and produce beneath the skin barrier
  a differencefrequency comparable to that of TENS
  units and muscle stimulators.


• Safety:no conclusive and consistent evidence that
  EM field exposure causes a significant increase in the
  risk of cancer, neurobehavioral, or reproductive dys-
  function (Kaiser, 1996; 1998).

COMPLEMENTARY AND ALTERNATIVE

THERAPIES

• Athletes as well as the general population are intrigued
  by the potential use of complementary and alternative
  medicine.

LOW-INTENSITYLASERTHERAPY

•Low-power lasers are widely used to treat muscu-

loskeletal injuries, speed healing, and lessen pain.

• Unfortunately, demonstration of clinical benefits has
  been difficult, and these devices have yet to gain FDA
  approval for clinical use (Basford, 1995).

410 SECTION 5 • PRINCIPLES OF REHABILITATION