Biomedical subjects

Alex R Ward

Publications and source records attributed to Alex R Ward.

7 recordsLinked to original sources

PubMed2006

Wrist extensor torque production and discomfort associated with low-frequency and burst-modulated kilohertz-frequency currents.

BACKGROUND AND PURPOSE: A randomized controlled trial to compare 2 forms of monophasic pulsed currents with 2 forms of burst-modulated, kilohertz-frequency alternating current ("Russian current" and "Aussie current") was conducted to establish whether different amounts of wrist extensor torque were produced and whether discomfort varied with stimulus type. SUBJECTS: The 32 subjects were adults who were healthy and were drawn from a population of staff and students at La Trobe University. METHODS: Each subject received all 4 currents. Maximal electrically induced torque (MEIT) of the wrist extensors was measured for each stimulus type. Relative discomfort of stimulation also was assessed. RESULTS: Russian current elicited lower mean torque than those elicited by Aussie current and monophasic pulsed currents. The Russian and Aussie currents elicited significantly less discomfort than the 2 monophasic pulsed currents. DISCUSSION AND CONCLUSION: When force production and relative discomfort were jointly used as the criteria, Aussie current was found to be more effective than either of the monophasic pulsed currents or Russian current stimulation.

Adult↗

PubMed2005

The effect of heat on tissue extensibility: a comparison of deep and superficial heating.

OBJECTIVE: To compare the effects of deep heating (shortwave diathermy [SWD]) and superficial heating (hydrocollator packs) on tissue extensibility. DESIGN: A double-blind, repeated-measures study. Possible effects of sex and intervention order were controlled. SETTING: A clinical laboratory. PARTICIPANTS: Twenty-four subjects with no neurologic or musculoskeletal pathologies affecting their lower limbs. INTERVENTIONS: Three intervention conditions: deep heating (SWD), superficial heating (hot packs), and no heating were applied in preallocated order to each subject at least 36 hours apart. MAIN OUTCOME MEASURES: Ankle dorsiflexion in weight bearing was measured by using an inclinometer to ascertain changes in the extensibility of the calf muscles and associated soft tissues. RESULTS: Deep heating increased the range of ankle dorsiflexion by 1.8 degrees +/-1.9 degrees . The change in ankle dorsiflexion after superficial and no heating was 0.7 degrees +/-1.5 degrees and -0.1 degrees +/-1.0 degrees , respectively. CONCLUSIONS: Deep heating, in the absence of stretching, increases tissue extensibility more than superficial heating or no heating. Superficial heating is more effective than no heating, but the difference was not statistically significant.

Adult↗

PubMed2004

The effect of duty cycle and frequency on muscle torque production using kilohertz frequency range alternating current.

We investigated the frequency and duty cycle dependence of maximal electrically induced torque (MEIT) of the wrist extensors. Fifty hertz burst modulated sinusoidal alternating current (AC) in the frequency range 0.5-20 kHz was used, with duty cycles ranging from a minimum (one cycle) to maximum (continuous AC). MEITs were similar at low frequencies but decreased markedly above 2.5 kHz. MEITs also decreased markedly above a 20% duty cycle. Subjective reports of discomfort were fewest at 4 kHz and at duty cycles in the range 20-25%. Our conclusion is that for maximum torque production, a frequency of 1 kHz and a duty cycle of 20% are indicated. When comfort is a major consideration, a frequency of 2.5 kHz provides an acceptable trade-off between MEIT and comfort. The findings also suggest that low duty cycle, burst modulated AC stimulation may be more effective than stimulation using conventional low-frequency pulsed current.

Electric Stimulation Therapy↗

PubMed2004

A comparison of true and premodulated interferential currents.

OBJECTIVE: To compare true and premodulated interferential currents (IFCs) in terms of sensory, motor, and pain thresholds; maximum electrically induced torque (MEIT); and comfort. DESIGN: Repeated-measures design. SETTING: Laboratory setting. PARTICIPANTS: University student and staff volunteers. INTERVENTIONS: Participants were exposed to 4 different conditions, chosen to evaluate 2 fundamental differences between true and premodulated IFCs. The conditions were different combinations of (1) premodulated or constant-amplitude currents applied at the skin and (2) crossed or parallel current paths. MAIN OUTCOME MEASURES: Sensory, motor, and pain thresholds; MEIT; and subjective reports of relative discomfort were recorded for each of the 4 conditions. Motor to sensory threshold ratios were subsequently calculated to assess depth efficiency of stimulation. RESULTS: The major findings were that crossed currents (true IFC) had no advantage over parallel currents (premodulated IFC) in terms of motor to sensory threshold ratio, MEIT, or comfort, and that premodulated currents produced higher torque values and less discomfort than constant-amplitude currents (true IFC). These results contradict the claimed superiority of true IFC. CONCLUSIONS: The findings indicate that premodulated IFC, delivered via 2 large electrodes, may be clinically more effective than the traditional true IFC arrangement in terms of depth efficiency, torque production, and patient comfort.

Adult↗

PubMed2002

Optimal frequencies for electric stimulation using medium-frequency alternating current.

OBJECTIVE: To determine the effect of single cycles of alternating current of various frequencies on sensory and motor thresholds and on relative thresholds (motor threshold/sensory threshold). DESIGN: Repeated-measures design. SETTING: Laboratory setting. PARTICIPANTS: University student and staff volunteers (N=16; mean age, 34y). INTERVENTIONS: Single cycles of sinewave frequencies between 1 and 35kHz were delivered at 50Hz. The frequencies were applied in a random order. MAIN OUTCOME MEASURES: The motor and sensory thresholds were recorded at each applied frequency. RESULTS: Both sensory and motor thresholds showed a smooth decrease to a minimum at approximately 3kHz. The relative threshold reached a minimum close to 9kHz. Comparison with previous studies showed that although absolute thresholds reach a minimum at a frequency that depends on electrode size, the frequency at which the relative threshold is a minimum was independent of electrode size and independent of whether the stimulus was applied as single pulses or in burst mode. CONCLUSIONS: The optimal frequency for transcutaneous stimulation using medium-frequency alternating current depends on the outcome measure used. It would therefore be desirable for clinical stimulators to provide a selection of carrier frequencies.

Adult↗

PubMed2002

Vastus medialis electrical stimulation to improve lower extremity function following a lateral patellar retinacular release.

STUDY DESIGN: A single-case study design. OBJECTIVES: To examine the effect of electrical stimulation of the vastus medialis muscle on stiffness, pain and function for a patient with delayed functional progress following a lateral patellar retinacular release. BACKGROUND: Five months after an arthroscopic lateral patellar retinacular release, the patient, although highly motivated, had made little progress using routine exercises and taping. METHODS AND MEASURES: An electrical stimulation program producing approximately 300 contractions daily of the vastus medialis muscle was implemented. The electrical stimulation applied for 33 of the 36 days was a rectangular and balanced biphasic pulse of 625-micros duration, 70-Hz frequency, 8-second peak on-time, 3-second off-time, 1-second ramp-up, and 0.5-second ramp-down. Objective measures of stair climbing and hopping, together with the subjective measure of therapist-palpated superomedial patella displacement force, were recorded for each treatment visit. Other subjective measures were the patient's daily recordings of knee pain and stiffness. RESULTS: Patient-reported stiffness reduced rapidly as the actual and cumulative number of daily contractions of the vastus medialis muscle increased. After 8 days of electrical stimulation, the patient was able to ascend stairs unassisted and after another 21 days to hop unsupported. CONCLUSIONS: Stiffness rapidly reduced and function started to improve once the electrical stimulation program was implemented. Recovery during the 36 days of treatment with electrical stimulation was greater than during the previous 5 months using other methods. Compliance was not an issue, nor was muscle soreness.

Arthroscopy↗

PubMed2002

Russian electrical stimulation: the early experiments.

Russian forms of electrical stimulation became popular to a large extent as a result of the activities of Kots, who claimed force gains of up to 40% in elite athletes as a result of what was then a new form of stimulation. He did not provide details of his published work, nor did he give references. Russian electrical stimulation became popular despite the lack of research in the English-language literature. No studies published in English examined whether the "10/50/10" treatment regimen (10 seconds of stimulation followed by 50 seconds rest, repeated for 10 minutes) advocated by Kots is optimal, and only one study addressed whether maximum muscle torque was produced at an alternating current frequency of 2.5 kHz. The few studies that compared low-frequency monophasic pulsed current and Russian electrical stimulation are inconclusive. This article reviews and provides details of the original studies by Kots and co-workers. The authors contend that these studies laid the foundations for the use of Russian forms of electrical stimulation in physical therapy. The authors conclude that there are data in the Russian-language literature that support the use of Russian electrical stimulation but that some questions remain unanswered.

Electric Stimulation Therapy↗