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Original Research Articles

Effect of Pain Education, Cryotherapy, and Transcutaneous Electrical Nerve Stimulation on the Pain, Functional Capacity, and Quality of Life in Patients With Nonspecific Chronic Low Back Pain

A Single-Blind Randomized Controlled Trial

Caldas, Vinicius Vieira de Alencar MS; Maciel, Daniel Germano MS; Cerqueira, Mikhail Santos MS; Barboza, Jean Artur Mendonça MS; Neto, João Batista Viana PT; Dantas, Glauko MS; de Melo, Ronan Romeno Varela MS; de Souza, Rachel Naara Silva PT; Vieira, Wouber Herickson de Brito PhD

Author Information
American Journal of Physical Medicine & Rehabilitation: March 2021 - Volume 100 - Issue 3 - p 243-249
doi: 10.1097/PHM.0000000000001552

Abstract

What Is Known

  • In the literature, some studies are using pain education to show the capacity to improve pain measurement outcomes. In addition, the combination of cryotherapy and transcutaneous electrical nerve stimulation presented better results on the pain when compared with the isolation application of the therapies in healthy individuals.

What Is New

  • No studies have reported the result of this combination in patients with nonspecific chronic low back pain with pain education. Electrophysical agents may be considered as complementary therapies in the treatment but do not increase the analgesic effect and functional capacity when compared with pain education.

Chronic low back pain (CLBP) is defined by a persistent pain occurring on most days and lasting longer than 3 mos.1 Although many pathological conditions may cause the onset of this pain, most CLBP cases do not present anatomopathological or radiological alterations, being denominated nonspecific.2 In addition, CLBP may be associated with the increase the physical or clinical manifestation of central sensitization.3 The economic impact related to CLBP is comparable with other prevalent and costly conditions such as cardiovascular diseases, cancer, mental health, and autoimmune diseases.4

Given the complexity of the associated factors, nonspecific CLBP management involves a broad approach in which the improvement in pain symptomatology is the main objective. Pain education is a cognitive behavioral intervention that provides education in pain neurophysiology to change maladaptive illness beliefs, to alter maladaptive pain cognition, and to reconceptualize beliefs about pain.5 A recent systematic review and meta-analysis showed that pain education has a small to moderate effect on pain for nonspecific CLBP.6

Other nonpharmacological strategies and electrophysical agents have been observed, such as, for example, cryotherapy, which is widely used in clinical practice because of its simplicity of application and low cost and, above all, because it promotes local analgesia because of the reduction in nociceptive nerve conduction, with a consequent increase in the pain threshold.7

Another possible mechanism underlying the analgesic effect of cryotherapy may involve the release of endogenous opioids caused by the contrairritative effect that predominates at the beginning of the application.8 Despite these physiological effects, a Cochrane review of cryotherapy in CLBP has shown that there are no conclusive results about its effectiveness because of the small number of studies involving this strategy and their low methodological quality.9

Another modality used in clinical practice is transcutaneous electrical nerve stimulation (TENS).10 Among the types of low-frequency TENS, burst mode has been used in clinical practice and consists of transcutaneous electrical stimulation characterized by low frequency and intensity enough to provide active muscle contraction.11 The mechanism of action of burst TENS is generated through the activation of receptors (mi-μ-opioids) in the periaqueductal substance, rostral ventral bulb, and spinal cord.10 Some studies have shown the efficacy of this therapeutic modality in patients with nonspecific CLBP in improving pain, functional capacity, decreasing the use of drugs,11 and improving quality of life.12 However, studies present variability in pulse durations, frequency, and amplitudes used, as well as differences in treatment protocol.13–15

Thus, although cryotherapy modalities and TENS in burst mode present results that are still inconclusive when used alone, in clinical practice, it has been observed that the combined use of the two modalities is associated with potentiation of the physiological effects that provide analgesia.16 In this context, it was demonstrated that the combination of cryotherapy and TENS in burst mode presented better results on the pain threshold when compared with the isolated application of the therapies in healthy individuals.17 No studies have been reported in the literature showing the result of this combination in patients with nonspecific CLBP.

Therefore, because of the clinical importance of nonspecific CLBP and the use of pain education as a new intervention, associated with the widespread use of this combination of modalities in patients in clinical practice, despite the lack of scientific answers corroborating its use in patients, it is necessary to prove whether there is this potentiation of the analgesic effect in these patients. Therefore, the aim of the present study was to analyze the effects of pain education and the combination of cryotherapy and burst TENS on pain, functional capacity, and quality of life in patients with nonspecific CLBP.

MATERIALS AND METHODS

Design and Participants

This is a single-blind randomized controlled trial, which was accepted by the ethics committee with the following registration number (1.953.896) and registered and accepted in Clinical Trials with the following prospective registry: NCT03111199. The study was carried out from September 2017 to May 2018 at the University Hospital and conforms to all Consolidated Standards Of Reporting Trials guidelines (see Supplemental Checklist, Supplemental Digital Content 1, https://links.lww.com/PHM/B85).

The sample consisted of 44 individuals of both sexes recruited in a nonprobabilistic way through written and electronic dissemination. The all participants provided a written informed consent to be participated in the study. To be eligible for inclusion, participants should be aged between 18 and 60 yrs, body mass index of less than 28 kg/m2, nonspecific pain in the lower back for at least 12 wks, and minimum pain of 3 on the visual analog scale (VAS).

The exclusion criteria adopted were as follows: pain in the lower back for less than 12 wks; previous contact with TENS; presence of alterations in the spine such as the following: fracture, infection, tumor, radicular pain, spondylolisthesis, and stenosis of the vertebral canal; and previous lumbar spine surgery, chronic use of analgesic opioids, skin changes or changes in sensitivity at the site of application, ice allergy, pregnancy, and use of a pacemaker. Figure 1 shows the participants not included and the 12 losses (three in each group).

F1
FIGURE 1:
Flow diagram according to CONSORT recommendations.

Randomization and Intervention

The randomization was performed by participating researcher not involved with the recruitment or evaluation of patients. The allocation in the groups was randomized and concealed and was achieved through the use of random numbering, sealed, and opaque envelopes. This allocation was in the form of blocks according to the following characteristics: sex, age, active menstrual cycle, and climacteric. The evaluator researcher was blind, without any knowledge as to which group each patient was included in and patients were blind to the type of TENS. This researcher involved in data analysis.

In this study, the participants were divided into four groups with secrecy of allocation: control (placebo TENS + educational program), cryotherapy group (cryotherapy + educational program), burst TENS group (burst TENS + educational program), and combination group (cryotherapy + burst TENS + educational program). Participants received the 10 treatment sessions9,10 3 times a week on alternate days, totaling 4 wks of treatment, with 30 mins of intervention with electrophysical resources and 10 mins of education program.

Educational Program

The CLBP education consisted of 10 mins of conversation with each participant in each session on: anatomy of the lumbar spine, nonspecific CLBP epidemiology, risk factors, deficiency of movement or motor control, deficiency in patients with CLBP, fear avoidance beliefs, kinesiophobia, anxiety, catastrophizing, and depression. The education was carried out by an experienced researcher who was previously trained and was performed in all four groups after the intervention.

Cryotherapy

The cryotherapy was performed using ice from the machine (Thermomatic TH3) and a plastic bag, each containing 700 g.17

Burst TENS

Burst TENS and placebo mode were performed using a KLD Sonophasys device with the following parameters: frequency modulation of 4 Hz, pulse duration of 240 μsec,11,17 and maximum intensity to generate visible muscle contraction without generating pain/discomfort due to stimulation. In the control group, the patients received the minimal therapeutic dose.18

In the combination group, burst TENS mode and cryotherapy were applied. First, a channel with a pair of self-adhesive electrodes was used with dimensions 5 cm wide and 10 cm long. After, it was put in the cryotherapy. Both techniques were applied on the points described in the Pressure Pain Threshold (PPT) evaluation with the participant in the ventral decubitus position.

Assessments

Initially, anthropometric and social information were collected. The functional capacity and quality-of-life questionnaires were then applied: Roland-Morris and Short Form - 36 health survey (SF-36), respectively. Next, the sit-to-stand test was performed, and finally, pain was measured by the VAS and PPT. This process was by the same evaluator, all in the same sequence, and in a room with a standard temperature.

Eligible women with regular and active cycles were all evaluated at the same stage, the follicular phase of the menstrual cycle, following the calendar method to confirm regularity by previous menstrual cycles.

Functional Capacity

The Roland-Morris questionnaire assesses the functional capacity of patients with nonspecific CLBP. The score varies from 0 to 24, through the summation of affirmative answers.19 In the sit-to-stand test, the participants were instructed to stand up and sit down 5 times on a reclining chair, keeping their arms crossed over the trunk. The participants were instructed to perform the movements as quickly as possible and time of execution of the five repetitions was measured.20

Quality of Life

The quality of life was assessed by the SF-36 questionnaire, which consists of 36 items, encompassed in 8 domains. The score of this instrument varies from 0 to 100, where 0 represents the worst general health condition and 100 the best.21 Both functional capacity (questionnaire and functional test) and quality of life were measured before and after the treatment protocol.

Pain

The VAS consists of a straight line of 10 cm, which represents a pain scale, anchored at the limbs by the words “without pain” and “worst pain.”22 The participant was asked at the end of the sit-to-stand test to mark the point representing the intensity of their pain during the movement. The value was obtained by measuring the distance between the beginning and the point marked by the participant.12

The PPT was also used to assess the participants’ pain. The apparatus used was the Wagner Force Ten, Model FDX, with a rubber tip 1 cm in diameter to measure the pain threshold at four points marked at two lumbar levels. The first two points were located 5 cm to the right and to the left of the fifth lumbar vertebra, L5R and L5L,23 respectively. The other two points were located 5 cm to the right and left of the third lumbar vertebra, respectively, L3R and L3L.23 Identification of the previously mentioned points followed the procedures used by Harlick et al.24

To assess segmental sensitization, a third point was marked on the anterior tibialis muscle (AT) of the right lower limb 5 cm from the tibial tuberosity. The algometer was positioned perpendicular to the point to be evaluated and a rate of 0.5 kgf/sec was performed. Two measurements in kilogram-force were collected for each point with an interval of 30 secs between measurements and was considered a mean value.20

The pain assessment by the algometer was performed in a dark room and the evaluator used dark glasses (IBM brand). The participant was in a prone position and verbally indicated the initial moment of pain. The pain was evaluated before and after the first session, as well as after the first, second, and third weeks and after the protocol.

A pilot study was performed before this study to testing intraexaminer reliability for PPT measurement with 15 participants with nonspecific CLBP; two measures were performed with a 30-min interval. The reliability obtained by the intraclass correlation coefficient was almost perfect for the points of the lumbar (0.86–0.98) and of the anterior tibialis (0.88) and the minimal detectable change (MDC) values for the pain threshold points are as follows: 0.82 for L5R; 1.04 for L5L; 0.46 for L3R; 0.66 for L3L; and 1.02 for AT.

Statistical Analysis

The sample was estimated at 11 participants per group according to the Miot formula,25 assuming a standard deviation of 1.8 cm on the VAS, a minimum detectable difference of 2 cm on the VAS, value of error α, usually 1.96 (5%), and value of error β, usually 0.84 (20%).

The results are presented as means, standard deviation, and the confidence interval (95%), with the significance level of P ≤ 0.05 and according to SPSS 20.0. The effect size was calculated using Cohen f in G Power 3.1. Normality of data distribution and homoscedasticity were verified using Kolmogorov-Smirnov and Levene tests, respectively. All variables showed normal distribution and homoscedasticity. We used a two-way analysis of variance (F) among the four groups studied in the preintervention and postintervention measures for painful sensation, functional capacity, and quality of life.

RESULTS

The sample characterization values and initial values of the dependent variables are found in Table 1. The values of functional capacity, sit-to-stand test, and quality of life are shown in Table 2. In the analysis between groups, functional capacity, there was no statistical difference for the Roland-Morris questionnaire (P = 0.744 and small effect size = 0.13) and the functional sit-to-stand test (P = 0.064 and large effect size = 0.46).

TABLE 1 - Values of mean, standard deviation, and relative frequency referring to the characterization of the sample and baseline
Variable Control (n = 11) Cryotherapy (n = 11) Burst TENS (n = 11) Combination (n = 11) P
Age, yr 28.36 ± 9.62 29.00 ± 8.09 29.63 ± 9.54 28.54 ± 8.69 0.981
Weight, kg 65.54 ± 8.59 71.30 ± 11.21 70.00 ± 14.22 62.09 ± 7.32 0.178
Height, m 1.65 ± 0.06 1.66 ± 0.08 1.67 ± 0.11 1.66 ± 0.07 0.991
BMI, kg/m2 23.91 ± 3.59 25.77 ± 3.52 24.85 ± 2.50 22.30 ± 2.29 0.067
Sex, n (%)
 Male 5 (45.5) 5 (45.5) 5 (45.5) 5 (45.5)
 Female 6 (54.5) 6 (54.5) 6 (54.5) 6 (54.5)
Marital status, n (%)
 Single 9 (81.8) 10 (90.9) 8 (72.7) 7 (63.6)
 Married 2 (18.2) 1 (9.1) 3 (27.3) 4 (36.4)
Education level, n (%)
 High school 4 (36.4) 1 (9.1) 1 (9.1) 1 (9.1)
 Superior education incomplete 5 (45.4) 5 (45.45) 4 (36.4) 5 (45.45)
 Superior education 2 (18.2) 5 (45.45) 6 (54.5) 5 (45.45)
Functional capacity
 Roland-Morris 8.72 ± 4.33 8.63 ± 3.52 10.00 ± 3.87 8.27 ± 2.53 0.702
 Sit-to-stand, sec 14.88 ± 2.55 14.70 ± 2.48 13.13 ± 2.41 12.64 ± 1.58 0.064
Quality of life SF-36
 FC 73.63 ± 13.80 70.00 ± 16.58 69.09 ± 17.14 75.90 ± 11.36 0.684
 LPA 22.72 ± 34.27 11.36 ± 23.35 11.36 ± 20.50 13.63 ± 13.05 0.647
 Pain 42.45 ± 17.86 46.00 ± 14.34 40.54 ± 9.28 40.27 ± 9.37 0.727
 GHS 58.90 ± 21.37 56.45 ± 16.15 61.00 ± 20.17 60.27 ± 18.52 0.948
 Vitality 43.18 ± 22.72 55.00 ± 15.49 41.81 ± 13.65 40.00 ± 23.55 0.270
 SA 69.09 ± 33.25 71.36 ± 27.43 63.45 ± 21.98 62.18 ± 23.61 0.829
 LEA 48.36 ± 47.94 31.00 ± 41.51 36.18 ± 43.20 27.27 ± 46.70 0.711
 Mental health 73.81 ± 18.70 72.36 ± 13.44 72.36 ± 17.74 60.36 ± 19.63 0.254
Pain
 VAS 4.65 ± 1.31 4.23 ± 1.20 4.74 ± 0.83 4.13 ± 1.62 0.684
 L5R 3.37 ± 1.45 3.65 ± 1.33 4.02 ± 2.23 3.73 ± 1.55 0.842
 L5L 3.27 ± 1.51 3.94 ± 1.23 3.86 ± 2.42 3.64 ± 1.58 0.811
 L3R 3.35 ± 1.23 3.95 ± 1.39 3.75 ± 2.11 3.48 ± 1.27 0.803
 L3L 3.59 ± 1.94 4.07 ± 1.13 3.86 ± 2.13 3.51 ± 2.13 0.863
 AT 5.41 ± 1.89 6.36 ± 2.60 5.59 ± 2.42 5.59 ± 2.35 0.780
AT, threshold at anterior tibialis; FC, functional capacity; GHS, general health status; L3L, threshold in the 3rd lumbar vertebra on the left side; L3R, threshold in the 3rd lumbar vertebra on the right side; LEA, limitation by emotional aspects; LPA, limitation by physical aspects; L5L, threshold in the 5th lumbar vertebra on the left side; L5R, threshold in the 5th lumbar vertebra on the right side; SA, social aspects; VAS, visual analog scale.

TABLE 2 - Mean values and standard deviation of the Roland-Morris, sit-to-stand, and SF-36 domains in the prepost and postprotocol
Control (n = 11) Cryotherapy (n = 11) Burst TENS (n = 11) Combination (n = 11)
Variable Pre Post Pre Post Pre Post Pre Post P Between ES
Functional capacity
 Roland-Morris 8.72 ± 4.33 4.09 ± 3.78 a 8.63 ± 3.52 4.00 ± 3.46 a 10.00 ± 3.87 4.27 ± 2.72 a 8.27 ± 2.53 4.09 ± 2.25 a 0.744 0.13
 Sit-to-stand, sec 14.88 ± 2.55 13.16 ± 2.52 a 14.70 ± 2.48 11.16 ± 2.07 a 13.13 ± 2.41 10.72 ± 2.63 a 12.64 ± 1.58 10.77 ± 1.9 a 0.064 0.46
SF-36
 FC 73.63 ± 13.80 85.90 ± 9.17 a 70.00 ± 16.58 80.90 ± 16.09 a 69.09 ± 17.14 83.63 ± 13.4 a 75.90 ± 1.36 78.18 ± 4.87 0.880 0.13
 LPA 22.72 ± 4.27 65.90 ± 40.73 a 11.36 ± 3.35 36.36 ± 34.21 11.36 ± 0.50 45.45 ± 45.8 a 13.63 ± 3.05 29.54 ± 1.56 0.182 0.35
 Pain 42.45 ± 17.86 75.00 ± 16.64 a 46.00 ± 14.34 65.09 ± 16.17 a 40.54 ± 9.28 64.63 ± 8.05 a 40.27 ± 9.37 59.27 ± 5.79 a 0.254 0.32
 GHS 58.90 ± 21.37 71.63 ± 22.22 a 56.45 ± 6.15 70.45 ± 15.66 a 61.00 ± 20.17 71.27 ± 1.83 a 60.27 ± 18.52 65.36 ± 14.39 0.968 0.08
 Vitality 43.18 ± 22.72 64.54 ± 25.53 a 55.00 ± 5.49 69.54 ± 0.42 a 41.81 ± 13.65 52.27 ± 21.83 40.00 ± 3.55 49.09 ± 21.19 0.087 0.42
 SA 69.09 ± 33.25 82.72 ± 9.71 71.36 ± 27.43 89.72 ± 16.60 a 63.45 ± 21.98 72.54 ± 2.32 62.18 ± 23.61 78.27 ± 16.77 0.417 0.27
 LEA 48.36 ± 47.94 60.54 ± 49.02 31.00 ± 41.51 69.59 ± 0.74 a 36.18 ± 43.20 51.36 ± 45.58 27.27 ± 46.70 33.09 ± 6.33 0.429 1.39
 Mental health 73.81 ± 18.70 81.81 ± 2.82 72.36 ± 3.44 78.18 ± 2.31 72.36 ± 1774 70.18 ± 14.89 60.36 ± 19.63 75.27 ± 12.2 a 0.315 2.29
aP < 0.05 with respect to the premoment.
ES, effect size; FC, functional capacity; GHS, general health status; LEA, limitation by emotional aspects; LPA, limitation by physical aspects; pre and post, in relation to the treatment protocol; SA, social aspects.

In quality of life, there were no statistically significant differences in any of the eight domains: functional capacity (P = 0.880, a small effect size = 0.13); limitation by physician aspects (P = 0.182, a moderate effect size = 0.35); pain (P = 0.254, a moderate effect size = 0.32); general healthy status (P = 0.968, a small effect size = 0.08); vitality (P = 0.087 an large effect size = 0.42); social aspects (P = 0.417, a moderate effect size = 0.27); limitation by emotional aspects (P = 0.429, a large effect size = 1.39), and mental health (P = 0.315, a large effect size = 2.29).

No statistical differences were observed in the VAS (Table 3) analysis between the groups (P = 0.082) at the time before and after the first session and at the moment postprotocol (P = 0.598). The effect size was small (0.09). The pressure threshold data are presented in Table 4. In the analysis between groups, there were no differences in the minimum detectable change (LCD) in the lumbar points. Only the control and combination groups showed values above the MDC in AT point.

TABLE 3 - Mean values and standard deviation of pain in the lumbar region in all groups at the different moments studied
Variable Control (n = 11) Cryotherapy (n = 11) Burst TENS (n = 11) Combination (n = 11) P Between
Pre 4.65 ± 1.31 4.23 ± 1.20 4.74 ± 0.83 a 4.13 ± 1.62 0.610
Post 2.28 ± 1.61 b 1.56 ± 1.58 b 2.47 ± 1.66 a,b 0.96 ± 0.92 b 0.082
1st week 2.93 ± 1.46 a 2.65 ± 1.88 2.65 ± 2.08 a,b 2.58 ± 1.06 0.961
2nd week 2.33 ± 2.22 b 1.89 ± 2.62 b 2.11 ± 1.84 b 2.06 ± 1.47 b 0.970
3rd week 1.57 ± 1.40 b 2.00 ± 1.62 b 1.40 ± 1.34 b 1.61 ± 1.18 b 0.773
Postprotocol 0.95 ± 0.95 b 1.21 ± 1.30 b 0.68 ± 0.44 b 1.20 ± 1.26 b 0.598
aP < 0.05 compared with postprotocol.
bP < 0.05 in relation to the preprotocol.
ES, 0.09; pre and post, in relation to the 1st session.

TABLE 4 - Mean values and standard deviation of the pain threshold in all groups and in the different moments and regions studied
Variable Pre Post ∆1 1st Week ∆2 2nd Week ∆3 3rd Week ∆4 Postprotocol ∆5
Control
(n = 11)
L5R 3.37 ± 1.45 3.01 ± 1.17 −0.36 3.17 ± 1.19 −0.20 3.98 ± 2.14 0.61 4.20 ± 2.06 0.83 a 4.95 ± 3.13 1.58 a
L5L 3.27 ± 1.51 3.36 ± 1.51 0.09 3.33 ± 1.37 b 0.06 4.52 ± 3.11 1.25 a 4.71 ± 2.21 1.44 a 5.09 ± 2.87 1.82 a
L3R 3.35 ± 1.23 3.27 ± 1.27 b −0.8 3.36 ± 1.41 b 0.01 4.53 ± 3.27 1.18 a 4.76 ± 2.91 1.41 a 5.23 ± 3.08 1.88 a
L3L 3.59 ± 1.94 3.59 ± 1.68 b 0 4.11 ± 2.14 0.52 4.76 ± 3.14 1.17 a 5.15 ± 2.94 1.56 a 5.43 ± 3.18 1.84 a
AT 5.41 ± 1.89 5.19 ± 1.98 b −0.22 4.96 ± 2.16 b −0.45 6.33 ± 3.15 c 0.92 6.63 ± 3.07 1.22 a 6.89 ± 2.90 1.48 a
Cryotherapy
(n = 11)
L5R 3.65 ± 1.33 4.98 ± 3.03 1.33 a 3.28 ± 1.11 b −0.37 4.11 ± 2.07 b 0.46 4.91 ± 3.26 c 1.26 a 5.31 ± 3.27 1.66 a
L5L 3.94 ± 1.23 5.03 ± 2.91 1.09 a 3.55 ± 1.44 b −0.39 4.24 ± 1.91 b 0.3 5.00 ± 3.28 1.06 a 5.57 ± 3.14 1.63 a
L3R 3.95 ± 1.39 d 4.98 ± 2.31 1.03 a 3.50 ± 1.08 b,d −0.45 4.15 ± 1.74 b 0.2 4.90 ± 3.14 0.95 a 5.41 ± 3.06 1.46 a
L3L 4.07 ± 1.13 5.20 ± 2.77 c 1.13 a 3.67 ± 1.09 b −0.40 4.42 ± 1.87 b 0.35 5.19 ± 3.15 c 1.12 a 5.71 ± 3.25 1.64 a
AT 6.36 ± 2.60 6.48 ± 2.47 0.12 5.52 ± 1.52 b −0.84 5.70 ± 1.69 b −0.66 6.34 ± 2.24 −0.02 7.14 ± 2.56 0.78
Burst TENS
(n = 11)
L5R 4.02 ± 2.23 3.41 ± 0.97 −0.61 3.84 ± 2.61 −0.18 4.24 ± 2.51 b 0.22 4.71 ± 2.51 0.69 5.32 ± 2.90 1.3 a
L5L 3.86 ± 2.42 3.55 ± 1.36 b −0.31 4.07 ± 3.05 0.21 4.38 ± 2.41 b 0.52 4.85 ± 2.93 0.99 5.57 ± 2.90 1.71 a
L3R 3.75 ± 2.11 3.45 ± 1.32 −0.30 4.24 ± 3.02 0.49 a 4.49 ± 2.19 0.74 a 4.64 ± 2.36 0.89 a 5.06 ± 2.22 1.31 a
L3L 3.86 ± 2.13 3.78 ± 1.70 −0.08 4.24 ± 3.01 0.38 4.64 ± 2.67 0.78 a 4.98 ± 2.95 1.12 a 5.44 ± 2.88 1.58 a
AT 5.59 ± 2.42 5.31 ± 2.02 b −0.28 5.33 ± 2.90 b −0.26 5.89 ± 2.92 0.3 6.42 ± 2.67 0.83 7.11 ± 2.64 1.52 a
Combination
(n = 11)
L5R 3.59 ± 1.48 4.06 ± 1.55 0.47 3.45 ± 1.80 −0.14 4.25 ± 2.53 0.66 4.37 ± 3.17 0.78 4.64 ± 3.02 1.05 a
L5L 3.46 ± 1.46 4.22 ± 1.89 0.76 3.82 ± 2.11 0.36 4.57 ± 3.06 1.11 4.40 ± 3.14 0.94 4.81 ± 2.75 1.35 a
L3R 3.48 ± 1.27 4.05 ± 1.40 0.57 a 3.45 ± 1.35 −0.03 4.09 ± 2.72 0.61 a 4.35 ± 3.12 0.87 a 4.61 ± 2.77 1.13 a
L3L 3.38 ± 1.41 4.14 ± 1.60 0.76 a 4.07 ± 1.91 0.69 a 4.64 ± 2.83 1.26 a 4.47 ± 2.38 1.09 a 5.14 ± 2.93 e 1.76 a
AT 5.60 ± 2.35 5.23 ± 1.99 −0.37 5.54 ± 2.85 −0.06 5.58 ± 2.96 −0.02 5.55 ± 2.96 −0.05 5.93 ± 2.83 0.33
aValues greater than MDC.
bP < 0.05 in relation to the moment postprotocol.
cP < 0.05 in relation to the 1st week.
dP < 0.05 in relation to the post.
eP < 0.05 in relation to the 3rd week.
1, difference of post in relation to the pre-evaluation; 2, difference of the 1st week in relation to the pre-evaluation; 3, difference of the 2nd week in relation to the pre-evaluation; 4, difference of the 3rd week in relation to the pre-evaluation; 5, difference of postprotocol in relation to the pre-evaluation; AT, anterior tibialis; L3L, 3rd lumbar vertebra on the left side; L3R, 3rd lumbar vertebra on right side; L5L, 5th lumbar vertebra on the left side; L5R, 5th lumbar vertebra on right side; pre and post, in relation to the 1st session.

Functional Capacity and Quality of Life

In the analysis within groups, in functional capacity, there was statistical difference for the Roland-Morris questionnaire (P < 0.01) and the functional sit-to-stand test (P < 0.01) in all of groups. Regarding quality of life, in the analysis within groups, there was statistically significant differences only in pain domain in all of groups (P < 0.05).

Pain

Statistical differences were observed in the analysis of VAS within groups at the time before and after the first session (P < 0.01) and at the moment postprotocol (P < 0.01) in all of groups. In the pressure threshold, the analysis within groups, all groups showed values above the minimum detectable change (LCD) in the lumbar points at the moment postprotocol.

DISCUSSION

In the analysis between the groups, the results showed that pain education with the individual or combined use of the electrophysical agents did not present better results when compared with the placebo application.

Regarding functional capacity, the literature demonstrates that to obtain clinically relevant improvement in patients with CLBP it is necessary to improve 4 points in the Roland-Morris questionnaire.23 In the present study, although all groups obtained this improvement, no differences were evident between the groups. One explanation for the improvement in the control group could be the pain education, because, according to Tegner et al.,6 education in health neurophysiology has low evidence and a small to moderate effect on functionality in patients with nonspecific CLBP. According to Buchmuller et al.,26 passive treatments used alone do not tend to improve functional capacity, reinforcing the hypothesis that education influenced functional capacity.

In addition to functional capacity, quality of life was also influenced by education. The improvement observed in this study corroborated Topuz et al.12 for the burst TENS group. However, in the study by Topuz et al.,12 the control group did not present improvement in the SF-36 domains, which can be explained by the fact this group in the present study received health education, as well as the placebo effect. This effect is associated with the activation of naloxone, a mi-μ-opioid receptor antagonist, providing analgesia through activation of the central inhibitory pathway of pain.27 Another mechanism is the patient’s expectation of the treatment, which may generate an unconscious placebo response. Positive expectation generates a decrease in anxiety, decreasing pain in patients with CLBP.28

In relation to the groups who underwent cryotherapy, they possibly presented effective results through reduction in the conduction of the nervous impulse and possible release of analgesic opioids29 immediately after application. However, after 2 wks of treatment, all remaining groups were able to achieve clinical relevance on the VAS, a decrease of at least 2 centimeters on this scale,29 with effects that lasted for up to the end of the protocol. This improvement in the participants over the following weeks may have been due to factors such as suppression of nociceptive receptor sensitivity27 and education on the neurophysiology of pain.30 According to Tegner et al.,6 education in health neurophysiology has moderate evidence and a small to moderate effect on pain in patients with nonspecific CLBP, which may justify in part the responses obtained for this variable.

Regarding the PPT, it is possible to consider some aspects by observing the MDC obtained in the evaluation of absolute reliability of the evaluator. Regarding the immediate effect of the first session, the suppression of nociceptive receptor sensitivity may explain these results of the PPT found after the first session at the lumbar points.5 In the cryotherapy and burst TENS groups, there was only the effect of cryotherapy, because in the burst TENS group, no increase was observed in the threshold above the MDC. One hypothesis for this finding is that after a single session, it is not possible to observe effects of the activation of endogenous opioids on the pain threshold.

A possible explanation for the two combined modalities not showing an additional analgesic effect could be that individuals with chronic pain symptoms respond through alteration in the endogenous pain pathway and present sensitization of the central nervous system,3 whereas in healthy individuals, there are no changes at the central level. Another hypothesis may be that the two modalities act by different mechanisms: burst TENS through activation of receptors of the endogenous pathway of pain11 and cryotherapy through the reduction in the nervous impulse conduction5 so that even if different possible mechanisms occurred, they did not provide a potentiated analgesic effect. Possible limitations of this study are the nonachievement of intention to treat and a drop rate of approximately 21%.

CONCLUSIONS

Pain education with cryotherapy and burst TENS alone or in combination are no better than the placebo application in improving pain, functional capacity, and some domains of quality of life in patients with nonspecific CLBP.

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Keywords:

Chronic Pain; Analgesia; Electric Stimulation and Ice

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