Subacute Low Back Pain in Active Duty (LBP)

The overall objective of this project is to compare three home-managed treatment regimens for subacute low back pain: Progressive Exercise Plan (PEP), NMES (neuromuscular electrical stimulation) core strength training and standard primary care management (PCM). Each of the two treatment arms will be supplemented by Primary Care Management. The specific aim of the study is to determine whether the two treatment regimes are significantly more efficacious than standard PCM alone in improving lower back muscle strength, daily physical activity, physical function, quality of life, and symptoms associated with subacute LBP.

The overall objective of this project is to compare three home-managed treatment regimens for subacute low back pain: Progressive Exercise Plan (PEP), NMES (neuromuscular electrical stimulation) core strength training and standard primary care management (PCM). The central hypothesis is that the NMES with PCM core strength training and PEP with PCM will show significantly greater improvements in muscle strength, pain, mobility/function, daily activity and quality of life (QOL) than PCM alone in military members with low back pain lasting three to eighteen weeks. The rationale for this study is that increasing torso muscle strength and decreasing pain through strength training exercises will significantly improve mobility, physical activity, QOL and reduce disability. Such outcomes could ultimately result in improved deployability, retention of military personnel and decreased economic costs in this population. The specific aims will be to determine whether the two treatment régimes are significantly more efficacious than standard PCM alone in improving lower back muscle strength, daily physical activity, physical function, quality of life, and symptoms associated with subacute LBP. After consent and baseline testing, active duty male and female subjects, ages 18 to <45, (n=135) with LBP will be randomly assigned to one of the three groups. Each of the two treatment arms will be supplemented by PCM and compared to a group receiving standard PCM alone. All groups will receive nine weeks of home therapy. Using longitudinal mixed regression models, differences in time trends for the outcome variables among controls and those in the treatment groups will be examined. In these regression analyses, the important primary measures will be expressed as a function of time, treatment group, and group-by-time interactions, while controlling for important covariates. Positive results could translate into accelerated rehabilitation, decreased symptoms and lower medical costs with better patient outcomes.

Non-specific LBP, where the cause for the pain cannot be determined, accounts for ninety percent of LBP cases.(Koes, et al, 2006) Reducing pain and continuing daily activity to prevent deconditioning are the primary therapy goals of PCM. Traditional PCM treatment of LBP will include advice/information on self-care options, over-the-counter analgesics, heat application, and remaining active.(Chou, et al., 2007; Koes, et al, 2010) Despite evidence that physical activity is effective, limiting activity remains common; individuals cite pain or re-injury fear as a limiting factor.( Lethem, et al., 1983; Poirandeau, et al., 2006; Steenstra, et al., 2016)

Rehabilitation requires activation of deep stabilizing muscle groups in the lumbopelvic region. Traditional exercises specific for these muscles are hard to teach with poor compliance. NMES is effective in stimulating these muscles, (Porcari, et al., 2005; Glaser, et al., 2001) resulting in enhanced activation, and improved performance. (Coghlan, et al., 2011) NMES devices are programmed to exercise core muscles through a series of stimulated muscle contractions. Concurrent muscle stimulation of the abdominal wall and lumbar paraspinal area has been shown to be most effective to maximally activate deep lumbar stabilizers in LBP patients. (Baek, et al., 2016) NMES provides as much pain relief as transcutaneous electric nerve stimulation (TENS) in LBP subjects. (Moore SR, Shurman J, 1997)

The literature suggests that this intervention may be of benefit in military personnel with subacute LBP. (Chou, et al., 2007;Marshall PW, Murphy BA, 2006) Meta-analysis showed evidence that graded-activity exercise improved patient outcomes in subacute LBP; however, evidence for other exercise programs were inconsistent. (Hayden, et al., 2005) A strengthening program involving the trunk and abdomen muscles showed clinical reductions in low back pain and disability with high adherence. (Kendall, et al., 2015) Systematic reviews were unable to support any one type of exercise over another. The use of pain-relieving modalities combined with muscle strengthening, such as home-based electrotherapy or progressive exercise, could reduce pain and improve function more rapidly.

The goal of PEP is to reduce back pain, disability, and improve trunk flexibility, strength and endurance through controlled, gradual, progressive back exercises. PEP teaches muscle strengthening exercises and self-management strategies to promote back fitness. PEP sessions provide a standardized self-management framework for performing the exercises at home. PEP is performed every other day/week for about ~1 hour over a period of 9 weeks. PEP consists of 3 sequential phases with each phase lasting 3 weeks. Exercises become progressively more difficult and intense, focusing on back stretching and strengthening that progressively load and unload the lumbar spine by means of flexion/extension exercises. The PEP group will perform 31 exercise sessions for 60 minutes on alternating days.

The NMES treatment group will receive a portable battery-operated device, Recovery Back (Neurotech®, Minnetonka, MN) with a 2-garment site-specific system: back & abdomen. NMES muscle contractions will be elicited by an electrical impulse generated by the Recovery Back system. The device delivers a pre-set program of NMES using a symmetrical biphasic square pulse waveform. (Moore SR, Shurman J, 1997) The garments are light-weight, breathable fabric that wraps around the waist with precise placements for the reusable electrodes. The controller uses a rechargeable battery with charger supplied. The NMES protocol consists of 30-minutes of NMES stimulation alternating between the abdominal and lumbar site over 9-weeks (one day Back training, next day Abdominal training).

All participants will receive standard primary care management for subacute LBP. Primary Care Management follows the clinical practice guidelines for low back pain.(Chou et al., 2007) Service members are to stay as active as possible and progressively increase their activity. Medications prescribed begin with paracetamol and NSAIDs as first-line drugs. Second-line drugs include antidepressants, benzodiazepines, tramadol, and opioids. All participants will receive an information sheet on LBP advising them to remain active and use self-care options such as heat application. To provide an attention control, the PCM only group will receive weekly communication from the study coordinator regarding pain and medication usage.

Torso extension muscle strength is measured with a modified version of the U of Michigan strength test system (Workability Systems, West Chester, Ohio) and a Chattanooga-Baseline® Hand Dynamometer - Digital LCD Gauge - ER™ 300 lb capacity (DJO Global, Chattanooga, Vista, CA USA). To measure trunk extension, the participant stands with their lower anterior abdomen against the padded board. The belt is placed around the posterior back and under the arms. Participants pull against the belt as forcefully as possible. Participants perform two maximal efforts maintaining each voluntary isometric exertion for 5 seconds, separated by 30-second rest; the highest value of the two trials will be accepted.

Torso flexion muscle strength is measured with a modified version of the U of Michigan strength test system (Workability Systems, West Chester, Ohio) and a Chattanooga-Baseline® Hand Dynamometer - Digital LCD Gauge - ER™ 300 lb capacity (DJO Global, Chattanooga, Vista, CA USA). For trunk flexion, the participant stands in the apparatus, buttocks against the padded board, the superior edge level with the iliac crest. A canvas belt is around the chest and under the arms horizontal to the force-measuring dynamometer on the apparatus frame. Participants pull against the belt as forcefully as possible. Participants perform two maximal efforts maintaining each voluntary isometric exertion for 5 seconds, separated by 30-second rest; the highest value of the two trials will be accepted.

The Visual Analog Scale (VAS) of pain will be used to assess pain at rest and after activity. (Revill et al., 1976) Participants will complete this scale following the push-ups, sit-ups, 6-minute walk and the lumbar trunk muscle test. This VAS pain subscale is a 10-cm horizontal line index with descriptive anchors at each end. At the far left (0.0 cm) is "no pain" and at the far right (10 cm) is "worst possible pain". The participant is instructed to place a vertical line at some point between the anchors to describe their level of pain.

The Short Form Health Survey Version 2.0 (SF-12v2) Health Survey will be used to determine each participant's overall impact of bodily pain on normal work. The SF12v2 has a question that asks participants to assess the impact of pain on normal work during the previous 4 weeks using options ranging from Not at all to Extremely. Responses are translated to numerical scores ranging from 0 to 100. Higher scores indicate less impact of bodily pain.

Physical activity will be measured using the Fitbit Charge 2 (San Francisco, CA). The Charge 2 is a wrist-worn three-axis accelerometer that measures steps walked, distance traveled, energy expenditure and floors climbed. The unique feature of this device is a wireless function that automatically uploads data to designated mobile phone devices or computers. Physical Activity is reported as average Kcal expended during a seven day period.

The 2-minute push-up test evaluates upper body endurance and strength as well as the stabilizing torso muscles of the abdomen and back. Starting in a prone position, the participant is positioned with their hands on the ground (shoulder width apart), toes in contact with the floor, spine parallel to the floor, elbows and hips in extension. The body moves as a single rigid unit and is lowered to the ground until elbows are at 90° angle. The body is then returned to the starting position by pushing the arms up to full extension. A push-up is counted if the elbows were brought to flexion of 90° or greater and then return to full extension, while keeping the body elevated on the toes. The number of push-ups performed in 2-minutes is recorded.

The 2-minute sit-up test measures trunk flexion and abdominal endurance. Starting in a supine position, the knee joints are flexed at a 90° angle, with fingers behind the head, soles of the feet and shoulder blades in contact with the floor. With the command to begin, the upper body is raised forward by flexing the abdominal muscles and then lowered. A sit-up is counted if the hands are behind the head, bringing the base of the spine to a vertical position and then returning the shoulder blades to the floor. The number of repetitions performed in 2 minutes is recorded.

The 6-Minute Walk Test (6-MWT) measures the distance a participant walks at a "fast" pace over a 6-minute period. Participants will "walk as quickly as you can" with the opportunity to stop and rest if required. This test measures functional capacity of walking. Healthy adults are expected to walk between 400 and 700 meters [1300-2300 feet] on the 6-minute walk test (Enright, 2003). Outcomes are reported in feet walked.

The Center for Epidemiologic Studies Depression (CES-D) scale is a self-report questionnaire that contains 20 items. Participants were asked to rate how often over the past week they experienced symptoms associated with depression. Scores range from 0-60 with high scores denoting greater depressive symptoms. CES-D scores were recorded at baseline (0 weeks) and subsequent visits. If the baseline score was greater than 23 the participants were not randomized.

Inclusion Criteria: Diagnosed with low back pain, categorized as lumbago or unspecified backache; greater than 3 weeks and less than 18 weeks since the onset of the episode of LBP; active duty military service member at the time of diagnosis; age ≥18 and <45 years; ability to provide freely given informed consent. Exclusion Criteria: Those who might be at risk of adverse outcomes from the study interventions will be excluded. This includes individuals with recurrence of LBP that is less than 3 months from prior episode; a significant co-morbid medical condition (such as severe hypertension, neurological disorder or pacemaker/defibrillator) in which NMES strength training or unsupervised exercise is contraindicated and would pose a safety threat or impair ability to participate; previous back surgeries; inability or unwillingness to participate in an exercise or strengthening program; clinical evidence of a lumbar radiculopathy; inability to speak and/or read English; pregnancy; vision impairment, where participant is classified as legally blind; unwillingness to accept random assignment; or a score >=23 on Center for Epidemiological Studies-Depression scale.

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