Monday 2 April 2012

Summary

Aussie Current is a kHz frequency burst modulated alternating current (BMAC) defined by the parameters; 1-kHz AC, 50-Hz bursts of 4ms duration and a 20% duty cycle (Ward, Robertson & Ioannou, 2004). Aussie Current, developed by Australian Dr Alex Ward, is used as a method of muscle strengthening by electrical stimulation.  This neuromuscular electrical stimulation (NMES) modality was based on the principles of Russian Current, a form of NMES which gained interest in the western world during the 1970's (Ward, Oliver & Buccella, 2006).


Waveforms Of Electrophysical Stimulation.

Aussie is a BMAC as seen in waveform C. (Ward, 2009). Click to enlarge image.

 These parameters were developed through research examining the effectiveness of a range of low- and medium range frequencies and duty cycles, investigating torque production against perceived participant discomfort and hypoalgesic effects.  The review of the literature provided evidence that Aussie Current is as effective as true interferential current (Ozcan, Ward & Robertson, 2004) and more effective than Russian Current when providing maximum electrically induced torque (MEIT) in healthy muscle (Ward, Oliver & Buccella, 2006). Aussie Current also proved to create less discomfort than pulsed current (PC), such as transcutaneous nerve stimulation (TENS), during MEIT (Ward, Oliver & Bucella, 2006).  In addition, Aussie Current was found to be equally effective as TENS for pain relief (Ward & Oliver, 2007) and functional electrical stimulation (FES) for muscle rehabilitation (Ward & Robertson, 2000). 

Although we could not find any specific precautions for the application of Aussie Current, it is similar to other forms of electrical stimulation and therefore similar contraindications would apply.  For example: Transthoracic applications, use within 3m of operating short wave diathermy equipment, pregnancy in the vicinity of the uterus, placed in the vicinity of an inbuilt stimulator or pacemaker, an unreliable patient, or undiagnosed pain (Robertson, Chipchase, Laakso, Whelan, & McKenna, 2001).

From the data gathered by the research conducted thus far Aussie Current shows promising applications for muscle strengthening in healthy muscle, injury rehabilitation and pain relief (Ward & Lucas-Toumbourou, 2007).

References

Ozcan, J., Ward, A. R. & Robertston, V. J. (2004). A comparison of true and premodulated interferential currents. Arch Phys Med Rehabil. 85: 409-415.
http://download.journals.elsevierhealth.com/pdfs/journals/0003-9993/PIIS0003999303004787.pdf

Robertson,V.J. Chipchase,L.S. Laakso, E.L. Whelan, K.M & McKenna, L.J. (2001). Guidelines for the clinical use of electrophysical agents. Australian Physiotherapy Association                 
Ward, A. R. (2009). Electrical stimulation using kilohertz-frequency alternating current. Physical Therapy. 89(2): 181-190.
http://search.proquest.com.libraryproxy.griffith.edu.au/docview/223112446/fulltextPDF?accountid=14543
Ward, A. R., & Lucas-Toumbourou, S. (2007). Lowering of sensory, motor, and pain-tolerance thresholds with burst duration using kilohertz-frequency alternating current electric stimulation. Arch Phys Med Rehabil. 88: 1036-1041.
http://download.journals.elsevierhealth.com/pdfs/journals/0003-9993/PIIS0003999307002973.pdf

Ward, A. R. & Oliver, W. G. (2007). Comparison of the hypoalgesic efficacy of low-frequency and burst-modulated kilohertz frequency currents. Physical Therapy. 87(8): 1056-1063.

Special Precautions and Contraindications

We could not find any specific precautions for the application of Aussie Current, however as this is similar to other forms of electrical stimulation the general contraindications indicated for these would also apply.  These are outlined in the APA Guidelines for the use of electrophysical agents.

Contraindications to electrical stimulation include;
  • Transthoracic applications (antero-posterior thorax, arm to arm, leg to arm).
  • Use within 3m of operating short wave diathermy equipment.
  • Pregnancy in the vicinity of the uterus.
  • Placed in the vicinity of an inbuilt stimulator or pacemaker.
  • Unreliable patient.
  • Undiagnosed pain.

APA Guidelines for EPA
To view full guidelines.

 

Precautions should be made with;
  • Circulatory insufficiency.
  • Risk of dissemination.
  • Exacerbation of existing conditions.
  • Unable to communicate.
  • Sensory loss.
  • Avoid applications over broken skin.
  • Repeated uses of self-adhesive electrodes, electrode sponges and covers   can reduce their conductivity and necessitate higher stimulus intensities.
(Robertson, Chipchase, Laakso, Whelan, & McKenna, 2001)

Electrodes

As Aussie Current is a MFAC small electrodes should not be used (Robertson et al, 2001). In the studies conducted by Ward and colleagues on wrist extensor torque conductive rubber electrodes were used measuring 44 x 40mm. The electrodes were place so as to efficiently stimulate the wrist extensors, ensuring that the cathode was the distal electrode (Ward et al, 2006).

Depending on the target muscle electrode size and placement will vary, but it is important to ensure general safety precautions are adhered to.

References

Robertson,V.J. Chipchase,L.S. Laakso, E.L. Whelan, K.M & McKenna, L.J. (2001). Guidelines for the clinical use of electrophysical agents. Australian Physiotherapy Accociation                 

Ward, A. Oliver, W. Buccella, D. (2006). Wrist Extensor Torque Production and Discomfort Associated With Low-Frequency and Burst-Modulated Kilohertz-Frequency Currents. Physical Therapy, 2006(86). 1360-1367 Doi:10.2522/ptj.20050300
http://search.proquest.com.libraryproxy.griffith.edu.au/docview/223108762/fulltextPDF?accountid=14543

 

The Literature Behind Aussie Current


Aussie Current is a relatively new development compared with its counterpart, Russian Current.  As such, there is limited literature available on the effects of the specific parameters that define Aussie Current.  During our literature search we found only 3 studies, which used Aussie Current explicitly, investigating torque production (Ward, Robertson & Ioannou, 2003; Ward, Oliver & Buccella, 2006) and hypoalgesic efficacy (Ward & Oliver, 2007).  However, from indirect research exploring the analgesic effects (Ward & Lucas-Toumbourou, 2007) and fatigue (Ward & Robertson, 2000) across a range of kHz frequency in conjunction with background information regarding electrical stimulation (Ozcan, Ward & Robertson, 2004; Ward, 2009) it is evident that Aussie Current has been developed with a sound theoretical basis.  This has resulted in current parameters that maximise torque production whilst minimising participant discomfort.

The positive outcomes thus far of the effectiveness of Aussie Current prompts the further exploration comparing it to other electrical stimulation modalities such as TENS and FES in a variety of conditions, such as analgesic and rehabilitation properties respectively.  To further strengthen the validity of the results would be aided by the reproduction of Ward’s research by a third party.  It will be interesting to see how Aussie Current’s journey as a electrophysical agent continues and how it can be used clinically in the future.

References 

Ozcan, J., Ward, A. R. & Robertston, V. J. (2004). A comparison of true and premodulated interferential currents. Arch Phys Med Rehabil. 85: 409-415.
http://download.journals.elsevierhealth.com/pdfs/journals/0003-9993/PIIS0003999303004787.pdf


Ward, A. R. (2009). Electrical stimulation using kilohertz-frequency alternating current. Physical Therapy. 89(2): 181-190.
http://search.proquest.com.libraryproxy.griffith.edu.au/docview/223112446/fulltextPDF?accountid=14543


Ward, A. R., & Lucas-Toumbourou, S. (2007). Lowering of sensory, motor, and pain-tolerance thresholds with burst duration using kilohertz-frequency alternating current electric stimulation. Arch Phys Med Rehabil. 88: 1036-1041.
http://download.journals.elsevierhealth.com/pdfs/journals/0003-9993/PIIS0003999307002973.pdf


Ward, A. R. & Oliver, W. G. (2007). Comparison of the hypoalgesic efficacy of low-frequency and burst-modulated kilohertz frequency currents. Physical Therapy. 87(8): 1056-1063.
http://search.proquest.com.libraryproxy.griffith.edu.au/docview/223117543/fulltextPDF?accountid=14543


Ward, A. R., Oliver, W. G. & Buccella, D. (2006) Wrist extensor torque production and discomfort associated with low-frequency and burst-modulated kilohertz-frequency currents. Physical Therapy. 86(10): 1360-1367.
http://search.proquest.com.libraryproxy.griffith.edu.au/docview/223108762/fulltextPDF?accountid=14543


Ward, A. R. & Robertson, V. (2000). The variation in fatigue rate with frequency using kHz frequency alternating current. Medical Engineering and Physics. 22: 637-646.
http://www.sciencedirect.com.libraryproxy.griffith.edu.au/science/article/pii/S1350453300000850


Ward, A. R., Robertson, V. & Ioannou, H. (2004). The effect of duty cycle and frequency on muscle torque production using kilohertz frequency range alternating current. Medical Engineering and Physics. 26: 569-579.
http://www.sciencedirect.com.libraryproxy.griffith.edu.au/science/article/pii/S1350453304000700

Friday 30 March 2012

Clinically Important Parameters and Dose Ranges

Aussie current is a form of neuromuscular electrical stimulation (NMES) the main purpose being to increase the force generating capacity of a muscle.  This form of electrical stimulation is most commonly used by physiotherapists to help “retrain” the muscles by stimulating nerves of the affected area after injuries such as stroke. However, the use of medium frequency kHz BMAC, such as Aussie and Russian currents, it can be used to increase muscle strength. The experiments conducted by Ward and colleagues examined different ranges of carrier frequencies, burst frequencies and duty cycles which resulted in the creation of Aussie Current.

As discussed in our previous post the specific parameters of Aussie Current include;
  • 1-kHz alternating current (AC).
  • 50-Hz bursts of 4ms duration.
  • 20% duty cycle. 
(Ward, Oliver & Buccella, 2006)

In 2004 Ward, Robertson and Iannou examined the effect of different ranges of frequency and duty cycle on muscle torque production and patient discomfort.  With a range of frequencies from 0.5 kHz to 20 kHz it was determined that the greatest torque was produced at a frequency of 1 kHz.  They also found that with increasing duty cycle torque decreased.  The least discomfort was reported with a 20 – 25% duty cycle.  A duty cycle of 20% also produced the lowest voltage / torque ratio and hence the best stimulation efficacy (Ward, Robertson & Iannou, 2004).  An important discovery from Ward’s research is the effectiveness of using a lower duty cycle.  This increases the safety of using medium frequency AC as only a fifth of electrical stimulation compared to continuous interferential AC is being used, greatly decreasing the likelihood of tissue damage when using these higher frequencies.

As Aussie current is defined by the above parameters any deviation from this prescription will mean that Aussie Current is no longer being used.  As such, no adjustments to amplitude or pulse duration to compensate for change of frequency are made for the accommodation of patient comfort.  However, patient comfort was discovered to improve with a lower duty cycle which has been included in the dosage parameters as 20 % duty cycle (Ward, Oliver & Buccella, 2006). Amplitude was not specified in the literature, which may be due to the highly individulised tolerance and muscle activation levels of the participants.

    This clip outlines the use of EPA for muscle strengthening
 and endurance.  The parameters are not Aussie Current
      however there are similarities as burst modualtion is used. 
    Notice the Russian Current setting under Electrotherapy.

Our research did not identify any information on specific dosage for strength program using Aussie Current.  However during the Ward, Oliver and Buccella 2006 study 15 minute test sessions were used.  As this type of stimulation is used for muscle strengthening an individual’s fatigue would likely be a limiting factor to session duration.  This would also be highly variable between patients, dependent on initial strength and extent of injury if being used as a rehabilitation tool.  Variations of fatigue rate using kHz frequency AC has also been investigated by Ward with Robertson in 2000.  This study identified the increased recruitment of fatigue-resistant fibers contributing to torque with frequencies between 1-10 kHz, compared with the low frequency (1-150 Hz), short duration pulsed current used with functional electrical stimulation (FES) often used in rehabilitation (Ward & Robertson, 2000).  This provides evidence to implement Aussie Current as a clinical application in rehabilitation and not solely as a mode to create muscle hypertrophy.  Delaying a patient’s fatigue will increase the level of treatment session length.  As neuroplasticity is greatly improved by high repetition the use of Aussie Current over FES may increase muscle response and decrease rehabilitation time.

References

Ward, A., Oliver, W. & Buccella, D. (2006). Wrist Extensor Torque Production and Discomfort Associated With Low-Frequency and Burst-Modulated Kilohertz-Frequency Currents. Physical Therapy, 86. 1360-1367 Doi:10.2522/ptj.20050300
http://physther.org/content/86/10/1360.full.pdf

Ward, A. & Robertson, V. (2000). The variation in fatigue rate with frequency using kHz frequency alternating current. Medical Engineering and Physics, 22: 637-646.
http://www.sciencedirect.com.libraryproxy.griffith.edu.au/science/article/pii/S1350453300000850

Ward, A., Robertson, V. & Iannou, H. (2004). The effect of duty cycle and frequency on muscle torque production using kilohertz frequency range alternating current. Medical Engineering & Physics, 26. 569 – 579. Doi: 10.1016/j.medengphy.2004.04.007.
http://www.sciencedirect.com.libraryproxy.griffith.edu.au/science/article/pii/S1350453304000700

Monday 26 March 2012

Aussie Current Dose Parameters

Aussie Current is a burst modulated alternating current (BMAC) used for muscle stimulation to elicit torque production.  Other electrophyscial agents (EPA) that are commonly used for muscle strengthening are Russian Current and Pulsed Current (PC), via interferential and transcutaneous electrical nerve stimulation (TENS) modalities respectively.  However each of the modes have differing dosage parameters. 

Aussie Current is similar to Russian Current as both are delivered to the muscles by a medium frequency current, but it is defined by the application of 1-kHz alternating current (AC), in 50-Hz bursts of 4ms duration, with a 20% duty cycle.  Russian current, on the other hand, uses a higher frequency of 2.5-kHz, and longer durations of 50-Hz bursts of 10ms duration, with a 50% duty cycle (Ward, Oliver & Buccella, 2006).  Alternatively, PC differs from Aussie and Russian Currents as it is a low frequency monophasic direct current (DC) stimulus.  No one dosage parameter defines PC, however a pulse frequency of 50 Hz and phase durations of both 200 us and 500 us were investigated in the Ward, Oliver and Buccella’s 2006 study of torque production and associated discomfort and thus will be referred to in this blog.



Comparison of the 4 waveform parameters investigated in Ward, A. Oliver, W. Buccella, D. (2006). Wrist Extensor Torque Production and Discomfort Associated With Low-Frequency and Burst-Modulated Kilohertz-Frequency Currents.


Traditionally muscle strengthening programs by electrical stimulation were performed by using Russian Current, which gained interest in western countries in the late 1970’s.  Russian Current also investigated by Ward and Robertson in a 1998 study of “Variation in torque production with frequency using medium frequency alternating current” found that the lower 1-kHz frequency was optimal for torque production and that a lower duty cycle provide greater comfort, parameters which now define Aussie Current.  Further investigation of torque production and patient perceived discomfort it was discovered that higher frequency (4kHz) and lower duty cycles (20% duty cycle) minimized participant discomfort (Ward et al, 2006).   



Reported level of discomfort between the 4 different stimuli.

Maximal electrically induced torque (MEIT) examined.

 Whilst there was no significant difference in maximal electrically induced torque (MEIT) produced across the four test parameters, Aussie Current produced the highest and Russian Current the lowest.  There was however a significant difference in the level of discomfort observed by the patient. The level of discomfort was far greater with the PC stimulus decreasing significantly as frequency increases. Aussie current recorded the second lowest level of discomfort with Russian Current providing the lowest ratings of discomfort (Ward et al, 2006).   

From the literature it can be inferred that Aussie Current aims to maximise torque production by the use of 1-kHz frequency and the lower duty cycle of 20% to increase comfort.  Thereby utilising the benefits of both parameters, which would be expected to increase subject compliance. 

References

Ward, A. Oliver, W. Buccella, D. (2006). Wrist Extensor Torque Production and Discomfort Associated With Low-Frequency and Burst-Modulated Kilohertz-Frequency Currents. Physical Therapy, 2006(86). 1360-1367 Doi:10.2522/ptj.20050300
http://physther.org/content/86/10/1360.full.pdf

Ward, A. Robertson, V. (1998). Variation in torque production with frequency using medium frequency alternating current. Arch Phys Med Rehabil, 1998 (79). 1399-1404 http://download.journals.elsevierhealth.com/pdfs/journals/0003-9993/PIIS0003999398902349.pdf

Monday 12 March 2012

Choosing Our Topic


Based on the recommendation of our course convenor, Cath Young, our group chose the topic of Aussie Current, an electrophysical modality invented by an Australian, Alex Ward. Although we had very little idea about what Aussie Current actually was, we were interested when Cath told us that if we could understand the main article, we would have a good handle on our Bioinstrumentation subject. This gave us pause. Would it be beyond our understanding? We decided it was a good way to multi-task, research and study at the same time. 

Topic in hand we started where most students do – we consulted “Dr Google”.  When we entered Aussie Current into the search engine it was less than productive, resulting in pages for Aussie Home Loans, credit cards and stories from A Current Affair.  To our surprise, the very first search result was Aussie Current Blogspot – an assignment from last year’s cohort.  Resisting temptation we avoided looking at this web page lest we were biased in our own exploration of the topic.

inventor of Aussie Current and 
Senior Lecturer at  La Trobe University,
 Victoria, Australia.

With little result from searching the term “Aussie Current”, we decided to search for the inventor, Alex Ward, instead.  This returned more promising results and we were able to access his La Trobe University staff profile, complete with email address and list of published journal articles and books. It made sense then to contact Alex directly, with the hope that he could point us in the right direction to start our research. Alex was not surprised to hear that we had been experiencing difficulty finding articles. He was very helpful and suggested we search Pubmed by keywords, using ‘Burst Modulated Alternating Current’ and ‘kHz Frequency Alternating Current’. He also recommended searching for another researcher, Yocheved Laufer who has also done some work with Aussie Current.


Armed with Alex’s text book, which we borrowed from the library, and relevant journal articles we prepared to start understanding Aussie Current and the content of our Bioinstrumentation course. 




Alex Ward's textbook.

References

Robertson, V.R. Ward, A. Low, J. & Reed, A. (2006). Electrotherapy Explained Principles and Practice (4th ed). London, United Kindom: Elsiver.