Clinical Rehabilitation http://cre.sagepub.com/
Effects of neuromuscular electrical stimulation and low-level laser therapy on the muscle architecture and functional capacity in elderly patients with knee osteoarthritis: a randomized controlled trial Mônica de Oliveira Melo, Klauber Dalcero Pompeo, Guilherme Auler Brodt, Bruno Manfredini Baroni, Danton Pereira da Silva Junior and Marco Aurélio Vaz Clin Rehabil published online 26 September 2014 DOI: 10.1177/0269215514552082 The online version of this article can be found at: http://cre.sagepub.com/content/early/2014/09/25/0269215514552082
Published by: http://www.sagepublications.com
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552082
research-article2014
CRE0010.1177/0269215514552082Clinical RehabilitationMelo et al.
CLINICAL REHABILITATION
Article
Effects of neuromuscular electrical stimulation and low-level laser therapy on the muscle architecture and functional capacity in elderly patients with knee osteoarthritis: a randomized controlled trial
Clinical Rehabilitation 1–11 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0269215514552082 cre.sagepub.com
Mônica de Oliveira Melo1,2, Klauber Dalcero Pompeo1, Guilherme Auler Brodt1,2, Bruno Manfredini Baroni1,5, Danton Pereira da Silva Junior3 and Marco Aurélio Vaz1,4
Abstract Objectives: To determine the effects of low-level laser therapy in combination with neuromuscular electrical stimulation on the muscle architecture and functional capacity of elderly patients with knee osteoarthritis. Design: A randomized, evaluator-blinded clinical trial with sequential allocation of patients to three different treatment groups. Setting: Exercise Research Laboratory. Subjects: A total of 45 elderly females with knee osteoarthritis, 2-4 osteoarthritis degrees, aged 66– 75 years. Intervention: Participants were randomized into one of the following three intervention groups: electrical stimulation group (18–32 minutes of pulsed current, stimulation frequency of 80 Hz, pulse duration of 200 μs and stimulation intensity fixed near the maximal tolerated), laser group (low-level laser therapy dose of 4–6 J per point, six points at the knee joint) or combined group (electrical stimulation and low-level laser therapy). All groups underwent a four-week control period (without intervention) followed by an eight-week intervention period. Main measures: The muscle thickness, pennation angle and fascicle length were assessed by ultrasonography, and the functional capacity was assessed using the 6-minute walk test and the Timed Up and Go Test. 1Exercise
Research Laboratory, Federal University of Rio Grande do Sul, Porto Alegre, Brazil 2Núcleo de Pesquisa em Ciências e Arte do Movimento Humano, University of Caxias do Sul, Caxias do Sul, Brazil 3Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil 4Physique Centre of Physical Therapy and Physical Fitness, Porto Alegre, Brazil 5Federal University of Ciências da Saúde de Porto Alegre
Corresponding author: Mônica de Oliveira Melo, Exercise Research Laboratory, School of Physical Education, Federal University of Rio Grande do Sul, Porto Alegre, Ave Willy Eugênio Fleck 1500, casa 1500, casa 187. Porto Alegre, 90150-180, Brazil. Email address: [email protected]
Downloaded from cre.sagepub.com at WRIGHT STATE UNIV on October 3, 2014
2
Clinical Rehabilitation
Results: After intervention, only the electrical stimulation and combined groups exhibited significant increases in the muscle thickness (27%–29%) and pennation angle (24%–34%) values. The three groups exhibited increased performance on the walk test (5%–9%). However, no significant differences in terms of functional improvements were observed between the groups. Conclusions: Neuromuscular electrical stimulation reduced the deleterious effects of osteoarthritis on the quadriceps structure. Low-level laser therapy did not potentiate the effects of electrical stimulation on the evaluated parameters. Keywords Neuromuscular electrical stimulation, low-level laser therapy, knee osteoarthritis, elderly, vastus lateralis muscle architecture, functional capacity Received: 2 November 2013; accepted: 28 August 2014
Introduction Knee osteoarthritis is a chronic degenerative disease that presents clinical symptoms, such as morning stiffness, reduced range of motion, chronic joint pain and muscle weakness.1 Evidence also suggests that muscle weakness is associated with negative changes in the muscle architecture, such as a decrease in the muscle thickness and fascicle length.2,3 These changes in the muscle structure have a negative impact on the patient’s functionality because a reduced fascicle length is related to a serial sarcomere loss and reflects the muscle’s reduced shortening velocity.3–5 Furthermore, reduced muscle thickness is associated with parallel sarcomere loss and ultimately leads to a reduction in the maximum muscle fibre strength capacity.3–6 Neuromuscular electrical stimulation has been recommended for quadriceps strengthening when chronic pain and joint stiffness prevent patients from engaging in a voluntary exercise programme.7–9 Although previous studies found increases in quadriceps strength and knee function,3,9 muscle architecture adaptations from neuromuscular electrical stimulation in patients with knee osteoarthritis have not been completely described in randomized controlled trials. Low-level laser therapy has been considered effective for treating knee osteoarthritis because of its cell bio-stimulating action10 and its regenerative,11,12 analgesic,10 and anti-inflammatory effects.10,11 Because of
its effects on the release of neurotransmitters that are associated with pain modulation and the release of anti-inflammatory agents,10,11 low-level laser therapy might improve the functionality of patients with knee osteoarthritis. The efficacy of low-level laser therapy, in combination with neuromuscular electrical stimulation to treat patients with knee osteoarthritis, has not been previously studied. The aim of the present study was to quantify the effects of neuromuscular electrical stimulation and low-level laser therapy on the muscle architecture parameters, pain and functional capacity. Our main hypothesis was that the combination of low-level laser therapy with neuromuscular electrical stimulation should promote a greater decrease in pain and larger increases in the functional capacity and muscle architecture parameters than each therapy alone.
Methods Trial design This randomized, single-blinded, clinical trial (ClinicalTrials.gov Identifier: NCT02067871) was approved by the University’s Ethics in Research Committee (Protocol number 20160). All patients signed a written consent form prior to data collection.
Downloaded from cre.sagepub.com at WRIGHT STATE UNIV on October 3, 2014
3
Melo et al.
Participants Participants were recruited via advertisements in disclosure media. The inclusion criteria included Grade 2 or 3 knee osteoarthritis, diagnosed by a traumatology–orthopaedics physician according to the criteria proposed by Kellgren and Lawrence13; age between 63 and 75 years; female gender; and one or more episodes of knee pain in the past six months. The following exclusion criteria were observed: body mass index higher than 40 kg/m2; hip, ankle or toe osteoarthritis diagnosis; the use of crutches for locomotion; participation in a strengthtraining programme or physiotherapy treatment for knee osteoarthritis in the past six months; neurological or cognitive disorders; rheumatoid arthritis; electronic implants; previous or upcoming surgery (within three months); or any cardiorespiratory, neuromuscular or metabolic disease that could represent an absolute contraindication or a contraindication to the performance of maximum strength tests.
Randomization and blinding A total of 45 participants who satisfied the inclusion criteria were randomly assigned to one of three study groups: Group 1 – the low-level laser therapy group; Group 2 – the neuromuscular electrical stimulation group; and Group 3 – the combined treatment group (neuromuscular electrical stimulation plus low-level laser therapy). Group allocation was randomized in three blocks of 15 sealed envelopes without external marks, which were mixed and numbered from 1 to 15, containing a piece of paper with the group allocation. As the fifth participant successfully completed the study baseline evaluation, the researcher opened the next envelope in the sequence in the presence of a new patient. All participants received treatment and had their results included in the data analysis. The researchers responsible for data collection and data analysis were blinded to the patients’ diagnosis or intervention.
Evaluation protocol All participants were assessed at three different time points over a 12-week period. The first four
weeks were used as the control period, when no intervention was performed. The intervention period lasted for eight weeks. The evaluation protocol was performed before the control period (precontrol), before the intervention period (preintervention) and after the intervention period (postintervention). The outcome measures were the vastus lateralis muscle architecture parameters (muscle thickness, fascicle length and pennation angle), functional capacity and pain level, which was measured during the functional tests. The vastus lateralis architecture parameters were assessed by an ultrasound system (SSD 4000, 51 Hz, ALOKA Inc., Japan) with a linear array probe (60 mm, 7.5 mHz). Subjects were evaluated at rest in the supine position with their knees and thigh fully extended.14,15 Three ultrasound images were captured with the probe positioned parallel to the direction of the muscle fibres at a 50% distance between the greater trochanter and the lateral femur condyle.3,14,15 The muscle architecture was analysed with Image-J software (National Institute of Health, USA) by a single researcher who was blinded to the group allocation and data acquisition using procedures previously described and validated in the literature14,15. The fascicle length was normalised by the thigh length. The mean value of each muscle architecture variable obtained from the three recorded ultrasound images was considered for subsequent statistical analysis. The functional capacity was evaluated via the 6-minute walk test and Timed Up and Go Test16. For the Timed Up and Go Test, the subject was instructed to initiate the test at a sitting position, with the trunk in an erect posture, arms crossed over the chest and feet on the floor.16 Each test was performed three times with a one-minute interval between trials. The mean value of the three trials was used for the statistical analysis. Immediately after the end of each test, pain was assessed using a 0 to 10 visual analogue pain scale, with 0 meaning ‘no pain’ and 10 meaning ‘excruciating pain’. After the tests, subjects were instructed to mark their subjective pain sensation on the visual analogue pain scale. The functional and pain outcomes were also analysed by a researcher who was blinded to the group allocation and data acquisition.
Downloaded from cre.sagepub.com at WRIGHT STATE UNIV on October 3, 2014
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Clinical Rehabilitation
Intervention protocols One researcher, experienced in the use of the applied therapies and blinded to the data acquisition and data analysis, applied the three intervention protocols. Low-level laser therapy was administered twice a week, with a minimum of 48 hours between the sessions, over a period of eight weeks. A THOR DD2 Control Unit, consisting of an infrared gallium–aluminium–arsenide (GaAlAs) diode laser probe (λ = 810 nm, continuous wave, 200 mW output power, 0.0364 cm2 spot size area and 0.218 J/ cm2 power density) (THOR®–London, UK) was used for the laser application. The laser was applied while the probe was held stationary and perpendicular to the skin, and light pressure was applied to three anteromedial and three anterolateral points over the intercondylar notch.11,12 The low-level laser therapy programme was based on the World Association for Laser Therapy recommendations17 and on studies that obtained positive results for the relief of osteoarthritic symptoms.11,12 During the first four intervention weeks, laser therapy was administered for 30 seconds per point, with a dose of 6 J per point (totalling 36 J), to optimise the laser’s analgesic18 and anti-inflammatory19 effects. In the remaining four weeks, the treatment focused on cartilage regeneration,20–21 for which an approximately 30% lower energy dose was used, i.e. 20 seconds per point, resulting in a dose of 4 J per point (totalling 24 J). In the neuromuscular electrical stimulation group, participants underwent supervised neuromuscular electrical stimulation sessions twice a week, at 48-hour intervals, over an eight-week period, with a progressive increase in the intensity and volume. Electrical stimulation was administered with portable, constant-voltage electrical stimulation equipment that was developed especially for the present trial. All sessions were performed at the same time of the day with participants seated on a conventional chair, knees flexed to 90° (0° = full extension) and the treated lower-limb strapped to the chair with a band. During electrical stimulation, two electrodes (5 cm × 13 cm) were placed anteriorly on the participants’ thighs. The proximal electrode was positioned over the quadriceps motor point, and the
distal electrode was placed perpendicular to the longitudinal thigh axis just above the patellar border.3 The quadriceps motor point was determined using an electrical stimulator pen (KLD Biosistemas, Brazil) with a faradic current, maximum frequency of 30 Hz and sufficient intensity to produce a tetanic contraction. A pulsed symmetric biphasic rectangular current, with a pulse frequency of 80 Hz, pulse duration of 400 μs and an intensity adjusted to the maximum level that subjects could tolerate, was used during electrical stimulation.22 The individual intensity and treatment volume were recorded by the stimulator during all sessions and stored on a computer following the intervention. Owing to the maximum stimulator current limit (≈127 mV), further treatment volume increases were reached by gradually increasing the total stimulation time and reducing the rest-time between contractions (Table 1, available online). The combined treatment was administered twice a week with at least 48 hours between sessions over an eight-week period. Participants received low-level laser therapy prior to electrical stimulation, using the same parameters that were used for the isolated electrical stimulation and laser therapy groups.
Statistical analysis Using muscle architecture variables as the main outcome and estimating a minimum difference equivalent to a standard deviation of 0.5 cm for muscle thickness, 3° for the pennation angle, and α = 0.05, a sample size of 14 subjects per group achieved a calculated power of 0.80 (WinPepi 1.45 for Windows) and was used in the study. To determine the between-intervention effects, two-factor (group X time) mixed-design analyses of variance (ANOVA) with repeated measures of time were performed. Major effects and significant interactions were also investigated via multiple comparisons using the Bonferroni post hoc test. The per cent variation between pre- and postintervention (the difference between the pre- and postintervention scores, divided by the preintervention score) was compared between the groups using one-way ANOVA followed by a Bonferroni post
Downloaded from cre.sagepub.com at WRIGHT STATE UNIV on October 3, 2014
5
Melo et al. Table 2. Anthropometric and baseline clinical characteristics of the three experimental groups.
Age (years) Height (m) Mass (kg) Thigh length (cm) Systolic pressure (mmHg) Diastolic pressure (mmHg) BMI (kg/m2) (% of Grade 2 OA) (% of Grade 3 OA)
Laser (n = 15)
Neuromuscular electrical stimulation (n = 15)
Combined (n = 14)
67.7 ±4.7 1.59 ±0.10 74.7 ±11.7 40.9 ±2.2 120.0 ±13.2 77.3 ±6.8 30 ±5 46.66 53.44
69.3 ±5.5 1.52 ±0.10 77.5 ±13.7 39.3 ±2.5 136.4 ±15.4 75.0 ±19.2 33 ±6 53.44 46.66
69.6 ±4.7 1.55 ±0.05 70.9 ±8.9 38.2 ±2.9 129.2 ±11.0 70.8 ±18.6 29 ±4 57.14 42.86
BMI: body mass index; OA: osteoarthritis.
hoc test. The effect size (the difference between the pre- and postintervention scores, divided by the standard deviation of the preintervention score) was calculated and interpreted using the following scale, which was proposed by Cohen23: trivial effect (
Effects of neuromuscular electrical stimulation and low-level laser therapy on the muscle architecture and functional capacity in elderly patients with knee osteoarthritis: a randomized controlled trial Mônica de Oliveira Melo, Klauber Dalcero Pompeo, Guilherme Auler Brodt, Bruno Manfredini Baroni, Danton Pereira da Silva Junior and Marco Aurélio Vaz Clin Rehabil published online 26 September 2014 DOI: 10.1177/0269215514552082 The online version of this article can be found at: http://cre.sagepub.com/content/early/2014/09/25/0269215514552082
Published by: http://www.sagepublications.com
Additional services and information for Clinical Rehabilitation can be found at: Email Alerts: http://cre.sagepub.com/cgi/alerts Subscriptions: http://cre.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav
>> OnlineFirst Version of Record - Sep 26, 2014 What is This?
Downloaded from cre.sagepub.com at WRIGHT STATE UNIV on October 3, 2014
552082
research-article2014
CRE0010.1177/0269215514552082Clinical RehabilitationMelo et al.
CLINICAL REHABILITATION
Article
Effects of neuromuscular electrical stimulation and low-level laser therapy on the muscle architecture and functional capacity in elderly patients with knee osteoarthritis: a randomized controlled trial
Clinical Rehabilitation 1–11 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0269215514552082 cre.sagepub.com
Mônica de Oliveira Melo1,2, Klauber Dalcero Pompeo1, Guilherme Auler Brodt1,2, Bruno Manfredini Baroni1,5, Danton Pereira da Silva Junior3 and Marco Aurélio Vaz1,4
Abstract Objectives: To determine the effects of low-level laser therapy in combination with neuromuscular electrical stimulation on the muscle architecture and functional capacity of elderly patients with knee osteoarthritis. Design: A randomized, evaluator-blinded clinical trial with sequential allocation of patients to three different treatment groups. Setting: Exercise Research Laboratory. Subjects: A total of 45 elderly females with knee osteoarthritis, 2-4 osteoarthritis degrees, aged 66– 75 years. Intervention: Participants were randomized into one of the following three intervention groups: electrical stimulation group (18–32 minutes of pulsed current, stimulation frequency of 80 Hz, pulse duration of 200 μs and stimulation intensity fixed near the maximal tolerated), laser group (low-level laser therapy dose of 4–6 J per point, six points at the knee joint) or combined group (electrical stimulation and low-level laser therapy). All groups underwent a four-week control period (without intervention) followed by an eight-week intervention period. Main measures: The muscle thickness, pennation angle and fascicle length were assessed by ultrasonography, and the functional capacity was assessed using the 6-minute walk test and the Timed Up and Go Test. 1Exercise
Research Laboratory, Federal University of Rio Grande do Sul, Porto Alegre, Brazil 2Núcleo de Pesquisa em Ciências e Arte do Movimento Humano, University of Caxias do Sul, Caxias do Sul, Brazil 3Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil 4Physique Centre of Physical Therapy and Physical Fitness, Porto Alegre, Brazil 5Federal University of Ciências da Saúde de Porto Alegre
Corresponding author: Mônica de Oliveira Melo, Exercise Research Laboratory, School of Physical Education, Federal University of Rio Grande do Sul, Porto Alegre, Ave Willy Eugênio Fleck 1500, casa 1500, casa 187. Porto Alegre, 90150-180, Brazil. Email address: [email protected]
Downloaded from cre.sagepub.com at WRIGHT STATE UNIV on October 3, 2014
2
Clinical Rehabilitation
Results: After intervention, only the electrical stimulation and combined groups exhibited significant increases in the muscle thickness (27%–29%) and pennation angle (24%–34%) values. The three groups exhibited increased performance on the walk test (5%–9%). However, no significant differences in terms of functional improvements were observed between the groups. Conclusions: Neuromuscular electrical stimulation reduced the deleterious effects of osteoarthritis on the quadriceps structure. Low-level laser therapy did not potentiate the effects of electrical stimulation on the evaluated parameters. Keywords Neuromuscular electrical stimulation, low-level laser therapy, knee osteoarthritis, elderly, vastus lateralis muscle architecture, functional capacity Received: 2 November 2013; accepted: 28 August 2014
Introduction Knee osteoarthritis is a chronic degenerative disease that presents clinical symptoms, such as morning stiffness, reduced range of motion, chronic joint pain and muscle weakness.1 Evidence also suggests that muscle weakness is associated with negative changes in the muscle architecture, such as a decrease in the muscle thickness and fascicle length.2,3 These changes in the muscle structure have a negative impact on the patient’s functionality because a reduced fascicle length is related to a serial sarcomere loss and reflects the muscle’s reduced shortening velocity.3–5 Furthermore, reduced muscle thickness is associated with parallel sarcomere loss and ultimately leads to a reduction in the maximum muscle fibre strength capacity.3–6 Neuromuscular electrical stimulation has been recommended for quadriceps strengthening when chronic pain and joint stiffness prevent patients from engaging in a voluntary exercise programme.7–9 Although previous studies found increases in quadriceps strength and knee function,3,9 muscle architecture adaptations from neuromuscular electrical stimulation in patients with knee osteoarthritis have not been completely described in randomized controlled trials. Low-level laser therapy has been considered effective for treating knee osteoarthritis because of its cell bio-stimulating action10 and its regenerative,11,12 analgesic,10 and anti-inflammatory effects.10,11 Because of
its effects on the release of neurotransmitters that are associated with pain modulation and the release of anti-inflammatory agents,10,11 low-level laser therapy might improve the functionality of patients with knee osteoarthritis. The efficacy of low-level laser therapy, in combination with neuromuscular electrical stimulation to treat patients with knee osteoarthritis, has not been previously studied. The aim of the present study was to quantify the effects of neuromuscular electrical stimulation and low-level laser therapy on the muscle architecture parameters, pain and functional capacity. Our main hypothesis was that the combination of low-level laser therapy with neuromuscular electrical stimulation should promote a greater decrease in pain and larger increases in the functional capacity and muscle architecture parameters than each therapy alone.
Methods Trial design This randomized, single-blinded, clinical trial (ClinicalTrials.gov Identifier: NCT02067871) was approved by the University’s Ethics in Research Committee (Protocol number 20160). All patients signed a written consent form prior to data collection.
Downloaded from cre.sagepub.com at WRIGHT STATE UNIV on October 3, 2014
3
Melo et al.
Participants Participants were recruited via advertisements in disclosure media. The inclusion criteria included Grade 2 or 3 knee osteoarthritis, diagnosed by a traumatology–orthopaedics physician according to the criteria proposed by Kellgren and Lawrence13; age between 63 and 75 years; female gender; and one or more episodes of knee pain in the past six months. The following exclusion criteria were observed: body mass index higher than 40 kg/m2; hip, ankle or toe osteoarthritis diagnosis; the use of crutches for locomotion; participation in a strengthtraining programme or physiotherapy treatment for knee osteoarthritis in the past six months; neurological or cognitive disorders; rheumatoid arthritis; electronic implants; previous or upcoming surgery (within three months); or any cardiorespiratory, neuromuscular or metabolic disease that could represent an absolute contraindication or a contraindication to the performance of maximum strength tests.
Randomization and blinding A total of 45 participants who satisfied the inclusion criteria were randomly assigned to one of three study groups: Group 1 – the low-level laser therapy group; Group 2 – the neuromuscular electrical stimulation group; and Group 3 – the combined treatment group (neuromuscular electrical stimulation plus low-level laser therapy). Group allocation was randomized in three blocks of 15 sealed envelopes without external marks, which were mixed and numbered from 1 to 15, containing a piece of paper with the group allocation. As the fifth participant successfully completed the study baseline evaluation, the researcher opened the next envelope in the sequence in the presence of a new patient. All participants received treatment and had their results included in the data analysis. The researchers responsible for data collection and data analysis were blinded to the patients’ diagnosis or intervention.
Evaluation protocol All participants were assessed at three different time points over a 12-week period. The first four
weeks were used as the control period, when no intervention was performed. The intervention period lasted for eight weeks. The evaluation protocol was performed before the control period (precontrol), before the intervention period (preintervention) and after the intervention period (postintervention). The outcome measures were the vastus lateralis muscle architecture parameters (muscle thickness, fascicle length and pennation angle), functional capacity and pain level, which was measured during the functional tests. The vastus lateralis architecture parameters were assessed by an ultrasound system (SSD 4000, 51 Hz, ALOKA Inc., Japan) with a linear array probe (60 mm, 7.5 mHz). Subjects were evaluated at rest in the supine position with their knees and thigh fully extended.14,15 Three ultrasound images were captured with the probe positioned parallel to the direction of the muscle fibres at a 50% distance between the greater trochanter and the lateral femur condyle.3,14,15 The muscle architecture was analysed with Image-J software (National Institute of Health, USA) by a single researcher who was blinded to the group allocation and data acquisition using procedures previously described and validated in the literature14,15. The fascicle length was normalised by the thigh length. The mean value of each muscle architecture variable obtained from the three recorded ultrasound images was considered for subsequent statistical analysis. The functional capacity was evaluated via the 6-minute walk test and Timed Up and Go Test16. For the Timed Up and Go Test, the subject was instructed to initiate the test at a sitting position, with the trunk in an erect posture, arms crossed over the chest and feet on the floor.16 Each test was performed three times with a one-minute interval between trials. The mean value of the three trials was used for the statistical analysis. Immediately after the end of each test, pain was assessed using a 0 to 10 visual analogue pain scale, with 0 meaning ‘no pain’ and 10 meaning ‘excruciating pain’. After the tests, subjects were instructed to mark their subjective pain sensation on the visual analogue pain scale. The functional and pain outcomes were also analysed by a researcher who was blinded to the group allocation and data acquisition.
Downloaded from cre.sagepub.com at WRIGHT STATE UNIV on October 3, 2014
4
Clinical Rehabilitation
Intervention protocols One researcher, experienced in the use of the applied therapies and blinded to the data acquisition and data analysis, applied the three intervention protocols. Low-level laser therapy was administered twice a week, with a minimum of 48 hours between the sessions, over a period of eight weeks. A THOR DD2 Control Unit, consisting of an infrared gallium–aluminium–arsenide (GaAlAs) diode laser probe (λ = 810 nm, continuous wave, 200 mW output power, 0.0364 cm2 spot size area and 0.218 J/ cm2 power density) (THOR®–London, UK) was used for the laser application. The laser was applied while the probe was held stationary and perpendicular to the skin, and light pressure was applied to three anteromedial and three anterolateral points over the intercondylar notch.11,12 The low-level laser therapy programme was based on the World Association for Laser Therapy recommendations17 and on studies that obtained positive results for the relief of osteoarthritic symptoms.11,12 During the first four intervention weeks, laser therapy was administered for 30 seconds per point, with a dose of 6 J per point (totalling 36 J), to optimise the laser’s analgesic18 and anti-inflammatory19 effects. In the remaining four weeks, the treatment focused on cartilage regeneration,20–21 for which an approximately 30% lower energy dose was used, i.e. 20 seconds per point, resulting in a dose of 4 J per point (totalling 24 J). In the neuromuscular electrical stimulation group, participants underwent supervised neuromuscular electrical stimulation sessions twice a week, at 48-hour intervals, over an eight-week period, with a progressive increase in the intensity and volume. Electrical stimulation was administered with portable, constant-voltage electrical stimulation equipment that was developed especially for the present trial. All sessions were performed at the same time of the day with participants seated on a conventional chair, knees flexed to 90° (0° = full extension) and the treated lower-limb strapped to the chair with a band. During electrical stimulation, two electrodes (5 cm × 13 cm) were placed anteriorly on the participants’ thighs. The proximal electrode was positioned over the quadriceps motor point, and the
distal electrode was placed perpendicular to the longitudinal thigh axis just above the patellar border.3 The quadriceps motor point was determined using an electrical stimulator pen (KLD Biosistemas, Brazil) with a faradic current, maximum frequency of 30 Hz and sufficient intensity to produce a tetanic contraction. A pulsed symmetric biphasic rectangular current, with a pulse frequency of 80 Hz, pulse duration of 400 μs and an intensity adjusted to the maximum level that subjects could tolerate, was used during electrical stimulation.22 The individual intensity and treatment volume were recorded by the stimulator during all sessions and stored on a computer following the intervention. Owing to the maximum stimulator current limit (≈127 mV), further treatment volume increases were reached by gradually increasing the total stimulation time and reducing the rest-time between contractions (Table 1, available online). The combined treatment was administered twice a week with at least 48 hours between sessions over an eight-week period. Participants received low-level laser therapy prior to electrical stimulation, using the same parameters that were used for the isolated electrical stimulation and laser therapy groups.
Statistical analysis Using muscle architecture variables as the main outcome and estimating a minimum difference equivalent to a standard deviation of 0.5 cm for muscle thickness, 3° for the pennation angle, and α = 0.05, a sample size of 14 subjects per group achieved a calculated power of 0.80 (WinPepi 1.45 for Windows) and was used in the study. To determine the between-intervention effects, two-factor (group X time) mixed-design analyses of variance (ANOVA) with repeated measures of time were performed. Major effects and significant interactions were also investigated via multiple comparisons using the Bonferroni post hoc test. The per cent variation between pre- and postintervention (the difference between the pre- and postintervention scores, divided by the preintervention score) was compared between the groups using one-way ANOVA followed by a Bonferroni post
Downloaded from cre.sagepub.com at WRIGHT STATE UNIV on October 3, 2014
5
Melo et al. Table 2. Anthropometric and baseline clinical characteristics of the three experimental groups.
Age (years) Height (m) Mass (kg) Thigh length (cm) Systolic pressure (mmHg) Diastolic pressure (mmHg) BMI (kg/m2) (% of Grade 2 OA) (% of Grade 3 OA)
Laser (n = 15)
Neuromuscular electrical stimulation (n = 15)
Combined (n = 14)
67.7 ±4.7 1.59 ±0.10 74.7 ±11.7 40.9 ±2.2 120.0 ±13.2 77.3 ±6.8 30 ±5 46.66 53.44
69.3 ±5.5 1.52 ±0.10 77.5 ±13.7 39.3 ±2.5 136.4 ±15.4 75.0 ±19.2 33 ±6 53.44 46.66
69.6 ±4.7 1.55 ±0.05 70.9 ±8.9 38.2 ±2.9 129.2 ±11.0 70.8 ±18.6 29 ±4 57.14 42.86
BMI: body mass index; OA: osteoarthritis.
hoc test. The effect size (the difference between the pre- and postintervention scores, divided by the standard deviation of the preintervention score) was calculated and interpreted using the following scale, which was proposed by Cohen23: trivial effect (
