Novel, user-friendly, home-based electrostimulation-induced muscle activation in people with a spinal cord injury*

Pressure ulcers are the most prevalent secondary complication in individuals
with a spinal cord injury. 80% of people with a spinal cord injury suffer from
a pressure ulcer, and 91% of those are at risk of developing a recurrent
pressure ulcer. Pressure ulcers lead to radical consequences such as decreased
mobility and independence, delayed rehabilitation, rehospitalisation, and
exclusion from social activities. Furthermore, pressure ulcers have a
tremendous impact on the individual*s physical ability to participate in daily
life activities. Therefore, pressure ulcers place an enormous
physical/emotional/financial burden on the individual, their caregivers and
society. This highlights the need for interventions to prevent pressure ulcers.

Entrapment of soft tissue between bony prominences and an external surface
(such as a wheelchair) represents the primary cause of pressure ulcers.
Consequently, this leads to mechanical deformation, increased peak sitting
pressures and prolonged periods of relative hypoxia (reduced oxygen supply to
the tissue). The marked leg muscle loss in individuals with spinal cord injury
contributes importantly to the increase in mechanical deformation and increased
sitting pressures, whilst the impaired blood flow after a spinal cord injury
contributes to a local tissue oxygen deficiency. Consequently, these changes in
muscle size, sitting pressure and blood flow importantly contribute to the
increased risk for developing pressure ulcers in individuals with a spinal cord
injury.

Regular electrical stimulation induced muscle activation increases muscle mass
and volume and augments muscle, subcutaneous and skin blood flow in individuals
with a spinal cord injury. Moreover, electrical stimulation applied to the
ischial tuberosity area (sitting bone) improves sitting pressure distribution.
Long term electrical stimulation of the gluteal muscles improves blood flow and
even increases gluteal muscle thickness. Although electrical stimulation is
potent in improving these key components in pressure ulcer development, current
electrical stimulation methods are limited by their laboratory based nature,
the need for trained personnel and expensive machinery; this importantly limits
the practicality of electrical stimulation. Therefore the proposed research
project is significant in that it involves the use of a home-based electrical
stimulation garment (shorts) with built in electrodes that overcomes these
limitations and can be used at home and in the community.

The aim of this study is to explore whether 3 months, daily use of electrical
stimulation in a home-based setting in individuals with SCI improves sitting
pressure distribution, muscle mass, skin circulation and dermatology quality of
life.

Twenty individuals with a spinal cord injury will receive an electrical
stimulation garment for 3 months.
Stimulation causes effective, comfortable levels of electrical stimulation with
visible muscle contractions, without significant limb movement
(checked/adjusted weekly if necessary). Participants will undergo daily
electrical stimulation..

The ES garment (Axiobionics, Ann Arbor, MI, USA) will be custom-developed lycra
shorts which house wires and surface electrodes. Two built-in surface
electrodes are placed over the upper part of the gluteal muscles above the
sitting area and 1 over halfway of the hamstring muscles, on both sides. The
surface electrodes (with conductive gel) are connected to elastic conductors,
guided through the side of the shorts to the front, ensuring the participant
does not sit on the wires. An eight-channel electrical stimulator connected to
the shorts will be used. Stimulation will be delivered biphasically at 50Hz to
induce a (visible) tetanic contraction. This amplitude will be applied with a
duty cycle of 1 s stimulation and 4 s rest for 3min with 16 min between each
block of stimulation. The average current amplitude using this stimulation
protocol has been 94±12.5mA, ranging from 70 to 115mA in our previous studies.
The current amplitude will be adjusted for each subject by increasing the
current amplitude in steps of 5mA to a point that doesn*t cause discomfort or
excessive muscle contractions that may disturb normal sitting. Weekly
telephone/skype questionnaires will also provide the opportunity to adjust the
intervention/stimulation.

The stimulation protocol will be delivered for 8 hours each day (during waking
hours). In the initial 2 weeks we will use an incremental 'dosage' protocol
whereby in the first week participants will undergo 4 hours of stimulation and
then 6 hours of stimulation in the 2nd week with 8 hours of stimulation
starting in week 3.

The paralyzed gluteal and hamstring muscles of the participants will be
activated. This will cause no pain and will not be uncomfortable. A small risk
of skin irritation under the electrodes exists, but this irritation will
disappear quickly after removal of the electrode.