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The use of electrical muscle stimulation to elicit a cardiovascular exercise response without joint loading: A case study

Authors:
Brian Caulfield at University College Dublin
Brian Caulfield
Louis Crowe
Louis Crowe
Conor M Minogue at University College Dublin
Conor M Minogue
Prithwish Banerjee at University Hospitals Coventry and Warwickshire NHS Trust
Prithwish Banerjee
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THE USE OF ELECTRICAL MUSCLE STIMULATION TO ELICIT A CARDIOVASCULAR EXERCISE RESPONSE WITHOUT JOINT LOADING: A CASE STUDY. Brian Caulfield, Louis Crowe, Conor Minogue, Prithwish Banerjee, Andrew Clark. JEPonline 2004;7(3):84-88. To date, electrical muscle stimulation (EMS) has not been used to elicit a cardiovascular exercise effect in healthy adults without joint loading. This case study was carried out to address this issue. We have developed an EMS system capable of eliciting a cardiovascular exercise response with minimal gross movement or loading of the limbs or joints. It is modelled on shivering, the natural process for generating heat when body temperature falls. One untrained male subject (age 31 yr; weight 70 kg) completed 4 treatment sessions using this system during which the stimulus intensity was increased in increments of 10% every 3 min to reach maximum output at each session. The same subject also underwent one single EMS session of 4 hours duration at a stimulation intensity of 40-60% of maximum output. VO2 and HR responses observed during the first 4 sessions were within the zone required for cardiovascular training. At peak stimulation intensity, the subject's workload was 12 METs. VO2 ranged from 20-25 ml/kg/min during the 4-hour session. The subject expended a cumulative total of 1865 Kcal during this session. This data suggests that the benefits of vigorous exercise may now be achieved through the use of electrical stimulation. There are many potential applications for this technology.
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Case Study: Electrical Muscle Stimulation Without Joint Loading
84
JEPonline
Journal of Exercise Physiologyonline
Official Journal of The American
Society of Exercise Physiologists (ASEP)
ISSN 1097-9751
An International Electronic Journal
Volume 7 Number 3 June 2004
Clinical Exercise Physiology
THE USE OF ELECTRICAL MUSCLE STIMULATION TO ELICIT A
CARDIOVASCULAR EXERCISE RESPONSE WITHOUT JOINT LOADING: A CASE
STUDY.
BRIAN CAULFIELD1, LOUIS CROWE2, CONOR MINOGUE2, PRITHWISH BANERJEE3, ANDREW
CLARK3
1University College Dublin School of Physiotherapy, Dublin, Ireland
2Biomedical Research Ltd, Galway, Ireland
3University of Hull, Dept of Academic Cardiology, East Yorkshire, UK
ABSTRACT
THE USE OF ELECTRICAL MUSCLE STIMULATION TO ELICIT A CARDIOVASCULAR
EXERCISE RESPONSE WITHOUT JOINT LOADING: A CASE STUDY. Brian Caulfield, Louis
Crowe, Conor Minogue, Prithwish Banerjee, Andrew Clark. JEPonline 2004;7(3):84-88. To date,
electrical muscle stimulation (EMS) has not been used to elicit a cardiovascular exercise effect in healthy
adults without joint loading. This case study was carried out to address this issue. We have developed an
EMS system capable of eliciting a cardiovascular exercise response with minimal gross movement or
loading of the limbs or joints. It is modelled on shivering, the natural process for generating heat when
body temperature falls. One untrained male subject (age 31 yr; weight 70 kg) completed 4 treatment
sessions using this system during which the stimulus intensity was increased in increments of 10% every 3
min to reach maximum output at each session. The same subject also underwent one single EMS session of
4 hours duration at a stimulation intensity of 40-60% of maximum output. VO2 and HR responses observed
during the first 4 sessions were within the zone required for cardiovascular training. At peak stimulation
intensity, the subject’s workload was 12 METs. VO2 ranged from 20-25 ml/kg/min during the 4-hour
session. The subject expended a cumulative total of 1865 Kcal during this session. This data suggests that
the benefits of vigorous exercise may now be achieved through the use of electrical stimulation. There are
many potential applications for this technology.
Key Words: Electrical Stimulation, Exercise therapy, Oxygen consumption.
INTRODUCTION
The benefits of electrical muscle stimulation (EMS) in medicine and sport are well established from a wide
body of research. The use EMS to elicit contraction of skeletal muscle has been effectively employed for a
wide variety of applications including prevention of muscle atrophy (1), muscle strengthening (2), and
management of incontinence (3), spinal deformities (4) and spasticity (5). Functional electrical stimulation
(FES) of muscle has been used with some degree of success in the spinal cord injured population to facilitate
locomotion (6).
Case Study: Electrical Muscle Stimulation Without Joint Loading
85
In recent years investigators have directed attention to the use of EMS technology to elicit a cardiovascular
response. This has primarily involved the use of EMS to induce leg cycling exercise (EMS-LCE), and
therefore dissipate energy through a cycle ergometer, in spinal cord injured patients. EMS-LCE can result in
VO2 levels of the order of 0.6-0.8 L/min in SCI subjects (7,8). Training with EMS-LCE can also result in
improvements of 10-35% in aerobic capacity in SCI subjects (9,10). Conventional EMS-induced tetanic
muscle contractions have a minimal effect on energy consumption. Eijsbouts and co-workers demonstrated
that bilateral stimulation of quadriceps, hamstrings, gastrocnemius and tibialis anterior muscle groups at
maximally tolerated intensity could produce an increase in oxygen consumption (VO2) of approximately 0.1
L/min in healthy adults at rest and during arm cranking exercise (11). Such levels of VO2, in isolation, are
unlikely to result in therapeutic benefit.
To date, EMS technology has not been used successfully to elicit a vigorous cardiovascular exercise
response without loading the limbs or joints. Such an application would provide many benefits for sport and
medicine. Unloaded EMS induced cardiovascular exercise could provide an attractive alternative to
customary forms of cardiovascular exercise that involve repetitive joint loading (such as running). It could
also be used to induce a cardiovascular exercise response in people who experience barriers to participation
in voluntary weight-bearing exercise, for example those with degenerative joint disease, obesity or spinal
cord injury (12).
We have developed a novel EMS system capable of eliciting a cardiovascular exercise response with
minimal gross movement or loading of limbs or joints. The pattern of EMS used in this investigation was
modelled on shivering, which is the natural process for generating heat when body temperature falls.
Shivering generates heat with no external work through rhythmical muscle contractions, occurring at a rate
of approximately 4-8 Hz (13). We attempted to mimic this pattern of muscle activity by using EMS to elicit
cardiovascular exercise via rapid, short duration, rhythmical contractions in the large lower extremity
muscle groups. The purpose of this case study was to show that this form of EMS is capable of eliciting a
vigorous cardiovascular exercise response in a healthy adult male.
METHODS
One male subject (age 31; weight 70kg), who gave written informed consent prior to participation,
completed 4 EMS sessions using a portable muscle stimulator over a two-week period. Sessions were
performed at the same time each day with the same electrode positioning and food intake. The output
stimulus intensity of the stimulator was increased by intervals of 10% every three minutes to reach
maximum output during each 30-minute session. The same subject also underwent one single EMS session
of 4 hours duration whilst watching television in a seated position. The stimulation intensity was varied
between 40 and 60% of maximum output over the course of this session. The subject’s physiological
response to stimulation was monitored and recorded throughout each session using a Quark B2 (Cosmed,
Italy) open circuit spirometry system.
Figure 1. Location of stimulating electrodes.
A specially designed hand held muscle stimulator
(BioMedical Research Ltd, Galway, Ireland)
powered by a 9 V battery was used in this
investigation. The stimulator current waveform was
designed to produce rhythmical contractions in the
lower extremity muscle groups occurring at a
frequency of 4 Hz. The maximum peak output
pulse current used in the present study was 300 mA.
Impulses were delivered through 5 silicon rubber
electrodes on each leg (area per leg = 600 cm2) as
illustrated in Figure 1. These were applied to the
body via a pair of tight fitting shorts, which
extended to the knee. The quadriceps, hamstrings
Case Study: Electrical Muscle Stimulation Without Joint Loading
86
and gluteal muscles were stimulated while the subjects lay supine for all stimulation sessions.
RESULTS
The subject completed all stimulation sessions without difficulty. The toleration of the stimulus, both in time
and intensity, was principally limited by subject fatigue. Tachypnoea, tachycardia, sweating, and fatigue
were all present at higher stimulation intensities. Average oxygen consumption (VO2) (ml/kg/min) and
heart rate (beats/min) at each stimulation level during each of the four 30-min sessions are illustrated in
Figure 2. These results demonstrate that a repeatable linear dose response relationship exists between
stimulus intensity and physiological responses. In addition physiological responses were consistent with
responses that would be expected in voluntary exercise such as cycling or running. VO2 levels of the order
of 5 and 10 METs were consistently apparent at 40 % and 80 % of maximum stimulus intensity respectively.
This was associated with corresponding mean heart rate responses of 93 and 163 beats/min.
Heart Rate
50
70
90
110
130
150
170
190
Heart Rate (BPM)
Oxygen Uptake
0
5
10
15
20
25
30
35
40
45
10 20 30 40 50 60 70 80 90 100
Stimulation Intensity
VO2 (ml/kg/min)
Session 1 Session 2 Session 3 Session 4
Figure 2. Physiological responses to repeated electrical muscle stimulation over 4 sessions.
VO2 (ml/kg/min) and cumulative energy expenditure (Kcal) during the 4-hour session are illustrated in
Figure 3. Breaks in the VO2 graph correspond to breaks in recording due to drinking water and changing
batteries in the stimulator. The subject expended a cumulative total of 1865 Kcal during the 4-hour session.
This level of energy expenditure is equivalent to this subject running 15 miles at a 9 min/mile pace (13).
DISCUSSION
This data suggests that the benefits of vigorous exercise may now be achieved through the use of electrical
stimulation. We have demonstrated that EMS can be used to elicit a physiological response consistent with
that expected with high intensity cardiovascular exercise. In addition, he also exhibited very high
Case Study: Electrical Muscle Stimulation Without Joint Loading
87
cumulative energy expenditure during one prolonged session. Our subject experienced no adverse effects
from the stimulation and reported that his principal limiting factor was fatigue.
It is not clear whether stimulation at high intensities would prove acceptable to all as there is a great deal of
individual variability in terms of reported comfort levels with EMS (14). However, we have previously
observed good tolerance for sub-maximal stimulation (40% of maximal output) using this form of EMS in a
group of 10 healthy adults (15). This sub-maximal stimulation was associated with an average exercise
workload of approximately 4 METs.
0
5
10
15
20
25
30
35
40
00:00:10
00:30:10
01:00:10
01:30:10
02:00:10
02:35:00
03:05:20
03:35:20
04:05:30
Time (hr:min:sec)
VO2 (ml/kg/min)
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Cumulative Energy Expenditure
(Kcal)
VO2 cumulative energy expenditur
e
Figure 3. Physiological response to prolonged electrical muscle stimulation.
There are many potential applications for this form of EMS. Some of the more obvious applications are in
those who possess barriers to participation in more ‘traditional’ forms of voluntary exercise such as walking,
running or cycling. This would include spinal cord injured patients, people suffering from obesity or those
with degenerative joint disease. It could also as an attractive alternative for those in sport who have a high
requirement for cardiovascular exercise training yet wish to minimize the amount of repetitive joint loading
they place upon their body. Further work needs to be done to investigate the mechanism of action of this
form of EMS and to quantify its effects in different populations.
Address for correspondence: Brian Caulfield, University College Dublin School of Physiotherapy, Mater
Hospital, Dublin 7, Ireland. Phone: 011 353 1 8034515; FAX: 011 353 1 8303550; Email:
b.caulfield@ucd.ie
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... A new generation of neuromuscular electrical stimulation (NMES) devices can exercise aerobically at equivalent rates to voluntary exercise [1][2][3][4][5]. As many people with type 2 diabetes cannot or will not exercise sufficiently a case series was undertaken to assess the acceptability and efficacy of treatment with this new exercise modality in a male, type 2 diabetic population. ...
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... 272 Another attraction of modern NMES devices is that they are able to exercise big muscle groups directly without loading any joints, and without the need for extensive back, hip or knee movements -as these joints are often painful or at risk in diabetics.- [272][273][274][275][276][277][278] There is evidence that NMES can play an important role in controlling T2DM. 279 Studies of NMES devices in diabetics have shown improvements in HbA1c equivalent to, or better than, taking real exercise. ...
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... Furthermore, partial twitch fusion may be experienced with frequencies exceeding 6 Hz resulting in greater fatigue and discomfort [41]. As such, emerging evidence now supports the use of 4-5 Hz (30 min -1-h/ day, 5 days/week, 4-8 weeks) at maximum tolerable intensity for elevating the aerobic capabilities of the target muscle and inducing a sustained aerobic exercise response in healthy active and sedentary populations [6,35,41,42] with an increase in aerobic exercise capacity reported in healthy active and sedentary populations and patients with chronic heart failure (CHF) [21,29,43]. These isometric, sub-tetanic contractions generated at 4 Hz may facilitate aerobic energy conversion by allowing more time for muscle fibres (Type I and Type II Fibres) to recover between pulses, whilst sustaining an elevated metabolic cost [27]. ...
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Hooker S P, Figoni S F, Rodgers M M et alPhysiologic effects of electrical stimulation leg cycle exercise training in spinal cord injured persons. Arch Phys Med Rehabil 73: 470-476
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Full-text available
The purpose of this study was to assess the physiologic training effects of functional electrical stimulation leg cycle ergometer (FES-LCE) exercise in persons with spinal cord injury (SCI) who were previously untrained in this activity. Ten persons with quadriplegia (C5 to C7) and eight with paraplegia (T4 to T11) performed FES-LCE training on an ERGYS I ergometer 10 to 30 minutes per day, 2 or 3 days per week for 12 to 16 weeks (36 total sessions). Training session power output (PO) ranged from 0.0W (no external resistance) to 30.6W. Each subject completed discontinuous graded FES-LCE and arm crank ergometer (ACE) tests before and after training for determinations of peak lower and upper extremity metabolic, pulmonary, and hemodynamic responses. Compared with pretraining, this SCI group exhibited significantly (p less than or equal to .05) higher posttraining peak PO (+45%), oxygen uptake ([O2], + 23%), pulmonary ventilation (+27%), heart rate (+11%), cardiac output ([Qt], + 13%) and significantly lower total peripheral resistance ([TPR], - 14%) during FES-LCE posttests. There were no significant changes in peak stroke volume (+6%), mean arterial pressure ([MAP], - 5%), or arteriovenous oxygen difference ([a-vO2diff], + 10%) during posttraining FES-LCE tests. In addition, no significant differences were noted for the peak level of any monitored variable during ACE posttests after FES-LCE training. The rise in total vascular conductance, implied by the significant decrease in posttraining TPR during FES-LCE tests, denotes that a peripheral circulatory adaptation developed in the persons with SCI during FES-LCE exercise training.(ABSTRACT TRUNCATED AT 250 WORDS)
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A study of discomfort with electrical stimulation
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  • Jul 1992
The primary purpose of this study was to investigate the influence of personality variables and contractile forces on magnitude estimates of pain unpleasantness and pain intensity during varying levels of neuromuscular electrical stimulation (NMES). Thirty volunteers, according to their scores on a preferred coping-style questionnaire, were assigned to one of two groups, one designated "monitors" (information seekers) and the other designated "blunters" (information avoiders). All subjects were administered varying levels of two types of NMES, one causing both afferent stimulation and muscle contraction and one causing only afferent stimulation. Subjects judged the intensity and unpleasantness of each current type using magnitude estimation. Data were analyzed using a 2 x 2 x 2 x 3 (coping style x current type x pain descriptor x current level) analysis of variance. The results indicated that the rate of increase of magnitude estimates for unpleasantness and pain intensity that corresponded to increases in current were dependent on (1) the preferred coping style of the subject, (2) whether the stimulus caused a muscle contraction, and (3) whether the subject was judging the intensity or the unpleasantness of the applied stimulus. Behavioral styles appear to affect how subjects characterize the discomfort associated with NMES, and involuntary muscle contractions contribute to the discomfort felt from NMES. These results suggest that interventions tailored to a preferred coping style may increase a subject's level of tolerance to NMES and thus provide a more beneficial treatment.
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Physiologic responses to prolonged electrically stimulated leg-cycle exercise in the spinal cord injured
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This study determined the physiologic responses to prolonged functional neuromuscular stimulation (FNS) leg-cycle exercise in seven quadriplegic and seven paraplegic subjects. Each subject completed 30 minutes of continuous FNS leg cycling during which open-circuit spirometry, impedance cardiography, auscultation, and fingertip capillary blood sampling were used to assess metabolic and hemodynamic responses. Compared with resting values, oxygen uptake, carbon dioxide production, respiratory exchange ratio (RER), pulmonary ventilation, heart rate (HR), left ventricular stroke volume (SV), cardiac output (Qt), and blood lactate (La) concentration were significantly (p less than .05) elevated, whereas plasma volume, bicarbonate concentration, and pH were significantly decreased in both groups during prolonged FNS leg-cycle exercise. Mean arterial pressure remained unchanged in quadriplegic and paraplegic subjects during the prolonged FNS leg-cycle exercise bout. Persons with quadriplegia elicited significantly lower MAP and tended to have lower SV and Qt responses than persons with paraplegia, probably due to a higher degree of sympathetic dysfunction and circulatory hypokinesis during FNS leg-cycle exercise. All other physiologic variables responded similarly between groups. We speculate that the relative increases observed for HR (33% to 60%), SV (45% to 69%), and Qt (113% to 142%) during prolonged FNS leg-cycle exercise create a sufficient cardiac-volume load to promote central cardiovascular conditioning in persons with both quadriplegia and paraplegia. The La accumulation (4.7 to 5.2 mmol.L-1) in the spinal cord injured during prolonged FNS leg cycling is unusually high for the power output attained (5.2W and 6.1W for quadriplegia and paraplegia, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
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Treatment of spinal spasticity by electrical stimulation
Article
We present the results and the methodology of trials using transcutaneous electrical stimulation. The aim of our work was to decrease spasticity in 44 patients with traumatic damage to the spinal cord; 35 non-electrically stimulated spastics were used as controls. Both groups were randomly selected from inpatients in the Paraplegic Department at the Hospital Rehabilitation Centre. This electrical stimulation procedure leads to a long-lasting reduction in spasticity, an increased range of passive and active movements, the facilitation of lost functions, an improvement in breathing, an increase in pulmonary capacity, the reappearance of some neurological reflexes, and a diminution of supersensitivity to skin irritation. Blood pressure and neurogenic bladder functions were restored to normal. In addition to clinical observations, we investigated muscle force and the electromyogram; other measurements used in the trials involved the use of a specially adapted neurological hammer, a pendulum test, spirometry, cystometry, sphincterometry and biochemical estimations.
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High Intensity Electrical Stimulation Effect on Thigh Musculature During Immobilization for Knee Sprain A Case Report
Article
  • Mar 1987
We conducted high intensity electrical stimulation of the quadriceps femoris and hamstring muscle groups daily during a three-week period of lower extremity cast immobilization for an athlete who sustained Grade II medial collateral and anterior cruciate ligament sprains. Thigh muscle hypertrophy of the injured (stimulated) leg was suggested by an increase in girth measurement on the day of cast removal. Three weeks after cast removal, single-leg, vertical-leap height was 92% of that accomplished by the dominant, uninjured leg, and the patient was able to return to athletic competition. This case report documents the usefulness of high intensity electrical stimulation for maintaining limb motor function during cast immobilization. Limb stabilization during stimulation and simultaneous excitation of agonist-antagonist muscle pairs also are discussed.
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Lateral Electrical Surface Stimulation as an Alternative To Bracing in the Treatment of Idiopathic Scoliosis: Treatment Protocol and Patient Acceptance
Article
  • May 1984
The purpose of this article is twofold. The first is to describe the management by physical therapists of patients using lateral electrical surface stimulation (LESS) for the treatment of progressive idiopathic scoliosis. In this treatment, electrodes are placed on the convex side of the curve in the region of the posterior to midaxillary line to produce a corrective force. Stimulation is applied nightly as the patient sleeps. Treatment is monitored by regular checkups and is stopped at achievement of skeletal maturity. No other treatment or exercises are necessary. The second purpose is to present the results of a questionnaire given to patients who had used LESS for at least six months. Fifty-seven patients and their parents responded to questions on scoliosis, acceptance of LESS treatment, and comparison of LESS treatment with previous brace treatment, if appropriate. Results indicated that many of the brace-associated problems were eliminated, and patient acceptance was high.
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Muscular Strength Development by Electrical Stimulation in Healthy Individuals
Article
  • Jul 1983
The effects of electrical stimulation and its comparison with various resistance training modes were investigated in 34 subjects who trained their dominant leg isometrically three times a week for five weeks. Group E (n = 8) used maximum voluntary isometric contractions only, Group S (n = 8) received only electrical stimulation, and Group ES (n = 9) trained using a concurrent combination of isometric exercise and electrical stimulation. In addition, Group C (n = 9), a control group, did no experimental training. The expected gain in torque was shown in the isometric strength scores of the three experimental groups; however, there was little change in the isometric strength of the control group and in the isokinetic (100, 200, and 300 degrees/sec) results of any of the four groups. After adjustments were made for pretest strength results, a one-way analysis of covariance indicated that the posttest isometric strength scores of the three experimental groups differed significantly from those of the control group. No other posttest differences were found among any of the other training modes.
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