Scope

Musculoskeletal diseases affect more than one out of every two persons in the United States over the age of 18, and nearly three out of four persons aged 65 and over. LBP is one of the most common reasons for physician visits (26–30).

In any given year, between 12% and 14% of the US adult population will visit their primary care physician with a complaint of back pain (31). LBP is the leading cause of disability and years living with disability throughout the world. More than 540 million people have been affected by activity-limiting LBP (9–14,32). The burden from LBP has doubled in the last 25 years, and the prevalence of the condition is expected to continue to increase with an aging and increasingly obese population (9). In the United States, LBP accounts for more lost workdays than any other musculoskeletal condition (31). Data from a recent investigation in Australia indicate that there is a moderate to high level of comorbidity amongst LBP patients; diabetes, arthritis, hyperlipidemia, osteoporosis, and coronary artery disease are within the top 10 most frequently reported comorbidities (18). LBP is the leading chronic health problem forcing older Australian workers to retire prematurely (33). While LBP is the most common cause in Europe of medically certified sick leave and early retirement, occurrence rates vary substantially among European countries (34). LBP affects between 49% and 70% of persons living in westernized countries and 70% and 85% of persons living in the United States in their lifetimes; it is the fifth most common reason for physician visits (28,29). Specific causes of LBP are often unknown and, in approximately 80% to 90% of afflicted patients, a specific pain source and cause cannot be identified (9,10,12,27–29,32,36). A number of investigators conclude that persons with CNSLBP experience PA intolerance, lower levels of physical fitness and function (37–42), increased disability (42,43), PA avoidance (due to fear of increased pain with activity) (9,12,32,44–47), lower PA participation levels (48,49), and reduced health-related quality of life (43). An association exists between CNSLBP and obesity (9,50–53), smoking (9,54), and sedentary lifestyle (9). A recent cross-sectional analysis of data from the National Health and Nutrition Examination Survey (NHANES) found that women participating twice weekly in musculoskeletal exercise training activities had significantly reduced odds of self-reported LBP (55).

Pathophysiology

Low back pain is considered a symptom rather than a disease and reflects many heterogeneous disorders and causes (9,10,12,14,32,35,56). As people age, LBP is accompanied by numerous activity limitations (10). Low back pain is often attributed to either nociceptive (sensitization of pain receptors in spinal/mechanical structures and fascial tissues), neuropathic (radicular or nerve related pain), or central (sensitization within the brain) sources (56). Traditionally, LBP is categorized by its etiology (causes), location, and duration of symptoms. Classifications are noted in Box 1.

In 80% to 90% of cases, a specific pathoanatomical cause of LBP cannot be determined; therefore, the majority of LBP is considered to be nonspecific low back pain (NSLBP) (9,10,12,27–29,32,35,36). This article primarily addresses this population. Chronic low back pain is described as discomfort and pain, localized below the costal margin and above the inferior gluteal folds, with or without leg pain, that has been present for 3 months or longer (11,12,27,30,36,56,57). Chronic nonspecific low back pain (CNSLBP) is further defined as chronic low back pain not attributed to recognizable, known, specific pathology (e.g., infection, tumor, osteoporosis, ankylosing spondylitis, fracture, inflammatory process, radicular syndrome, or cauda equina syndrome) (9,10,12,27–29,32,35,36). During medical examinations of patients with LBP, physicians or qualified healthcare providers (HCP) conduct screening procedures to “rule in” or “rule out” more severe pathology.

“Red Flags” are symptoms or conditions experienced by patients with LBP that may warrant further medical evaluation (9,11,12,27,32,35,58–62). Their presence or absence can determine whether physicians and HCPs clear patients with CNSLBP for—or exclude them from—exercise participation. Although worldwide agreement on a uniform list is lacking, some generally recognized Red Flags exist and are provided in Box 2.

To reiterate, persons with CNSLBP experience PA intolerance, decreased neuromuscular function, strength, and lower levels of physical fitness (37–42,64–70), PA avoidance (due to fear of increased pain with activity) (9,12,32,44–47) and are more sedentary than age- and sexmatched persons without CNSLBP (48,49). An association exists between CNSLBP and obesity (9,50–53), smoking (9,54) and sedentary lifestyle (9). Some investigators found delayed onset of activation in the transversus abdominus muscles and deficits in motor control in persons experiencing CNSLBP (64). Changes in size, composition and fiber typing of the multifidus, erector spinae, and other paraspinal muscles have been considered potential factors in the etiology and/or recurrence of pain symptoms and their effects on muscle strength and endurance (36,65–70). Gluteus medius weakness and gluteal muscle tenderness are common symptoms (70), and CNSLBP can also contribute reduced healthrelated quality of life (HRQOL) (43).

Effects on the Exercise Response

Physical activity tolerance and exercise responses may be negatively affected by pain severity, location, physical fitness, strength, and body positions required during exercise testing and CR exercise training. Some individuals with CNSLBP are intolerant of motions such as trunk flexion or extension. In this case, positions such as prolonged standing, sitting, leaning, and reaching forward can cause discomfort, preventing CR patients from achieving their best exercise or testing efforts and results (3,5,6,22,23,25,75–77).

Patients who are flexion intolerant generally experience pain, discomfort, and fatigue when doing exercises requiring frequent bending at the waist, leaning forward, or prolonged sitting. Box 3 provides movements in which pain and discomfort may occur or worsen.

Patients who are extension intolerant generally experience pain, discomfort, and fatigue when performing exercises requiring frequent standing, backward bending, overhead reaching/lifting, and spinal hyperextension. Box 4 presents movement in which pain and discomfort may occur or worsen.

Regardless of whether or not a CR patient has a movement directional preference, the clinical exercise physiologist (CEP) should select warm-up, ET, RT, and flexibility exercise variations that CR patients can comfortably perform during their workout sessions. (19,20,22,23,25,75–77).

Examples of appropriate exercise modifications for CR patients with CNSLBP who have movement directional preferences are provided in Table 1. Exercise modifications to help CR patients with CNSLBP induced movement intolerance are addressed in a subsequent section.

TABLE 1. Exercise modifications for patients with chronic nonspecific low back pain (CNSLBP) and movement directional preferences.

View Fullscreen

Exercise Benefits

A variety of exercise interventions (including but not limited to yoga, AT, RT, and FT) have been shown to reduce pain and improve physical function in persons with CNSLBP, yet there is no consensus on the most effective form of exercise (21,36,60,72–74). Commonly reported benefits of AT and RT include:

• Increased physical activity tolerance

• Increased range of motion

• Increased physical fitness and strength

• Increased health-related quality of life

• Increased pain tolerance

• Increased functional capacity

• Increased overall physical activity participation levels (21,36,60,73,74).

A recent systematic review and meta-analysis assessed the effects of resistance, endurance, and flexibility exercise in population-based interventions to prevent LBP and associated disability (78). They reported exercise reduced the risk of LBP by 33% and that severity and disability from LBP were lower in exercise training versus control groups. It was concluded that a combination of strengthening exercise with either stretching or aerobic exercise performed 2 to 3 times per week can be reasonably recommended for the prevention of LBP in the general population (78). Other well-tolerated and effective programs include periodized RT programs which improve strength and physical activity participation levels, as well as reduce disability levels in both sedentary and athletic populations with CNSLBP (79–84).

Exercise and Physical Activity Recommendations

These recommendations for persons with CNSLBP are consistent with those from the American College of Sports Medicine (ACSM) and the United States Department of Health and Human Services (USDHHS). They are consistent with those for patients participating in outpatient CR exercise programs, who are healthy, and do not have CNSLBP (1–6).

Common exercise program goals for persons with CNSLBP and patients in outpatient CR are similar and emphasize the importance of:

• Improving health and well-being

• Improving exercise tolerance

• Improving functional capacity

• Improving HRQoL

• Resuming vocational and recreational pursuits (1–4).

Aside from performing structured exercise, persons with CNSLBP should adopt an active lifestyle and add routine PA breaks when periods of sitting cannot be avoided (1–6).

Components of a comprehensive exercise program should include RT, ET, flexibility, and neuromotor training (2,3,5,6,36,73,74,85). The compendium of physical activities can serve as a resource for assisting CR patients with CNSLBP to find additional leisure time and recreational activities they can perform comfortably (86). Table 2 provides a general summary of exercise guidelines and PA recommendations for CR patients with CNSLBP.

TABLE 2. Physical activity and exercise recommendations for persons with chronic nonspecific low back pain.

View Fullscreen

Exercise and Functional Testing

Prior to performing exercise or functional performance tests, CEPs should discuss appropriate individualized protocol selections with the patient's physicians and HCPs. They should perform exercise and functional tests that CR patients with CNSLBP can complete comfortably (5,6).

As an example, patients who experience pain with trunk flexion may be more comfortable and perform better when standing while patients who experience pain when in trunk extension or have difficulty standing might be more comfortable and perform better when seated or recumbent (22–24,77,87).

Treadmill tests using low-level protocols such as the Modified Naughton or ramp or discontinuous protocols, along with the field-based 6-minute walk test can reduce compensatory trunk flexion due to less reliance on elevation. Each of these tests is appropriate for patients with flexion intolerance. Lower body cycle ergometer or recumbent cycle or step ergometer protocols are appropriate for CR patients with extension intolerance (3,5,6). Muscle strength testing using a multiple repetition maximum is well tolerated and an effective tool for measuring current strength levels, determining training loads, and measuring post-program strength increases in clients with CNSLBP and are an acceptable alternative to one-repetition maximum (1-RM) testing (81–83).

The standard Borg rating of perceived exertion (RPE) or the OMNI Resistance Exercise Scale (OMNI RES) scales can approximate intensity of patient effort during muscular strength testing and training (3,88,89).

The multiple repetition sit-to-stand test, 30-second arm curl, and handgrip strength test are viable instruments for measuring muscular strength in patients with CNSLBP who are ≥60 years old (3,90,91).

After a cardiac event, patients are at risk for deficits in mobility and function due to extended periods of inactivity (e.g., bed rest) (91). Gait speed, the 5 times sit-to-stand (STS), and handgrip strength tests are reliable and responsive measures for patients in CR and typically tolerated by those with CNSLBP (91).

Other acceptable tests that assess neuromotor function and balance include the timed up and go (TUG), 5-minute walk, and stair climb tests (3,6,26).

Exercise Program Recommendations for CNSLBP

An individualized approach to exercise program development that addresses all health-related fitness variables is appropriate when working with patients who have CNSLBP. The CR program should help to enhance functional performance and HRQOL (1–6,21,74,73,85). Components of a comprehensive exercise program for CR patients with CNSLBP should include AT, RT, FT, and neuromotor training (1–6,12,21,74,77,81–83,85). Due to potential physical deconditioning and pain in some patients who have CNSLBP, a slower rate of exercise program progression, volume, and intensity may be warranted (3,5).

Aerobic endurance training (AT) is generally well-tolerated by patients with CNSLBP (80). An appropriate goal for CR patients with comorbid CNSLBP is to accumulate ≥30 min of moderate intensity AT on most (≥5) days of the week (2–6). Initial AT bouts of ≤10 min repeated 2 to 3 times per day might be best tolerated in deconditioned CR patients. Total daily time during a single AT bout can be increased gradually to meet or exceed the 30 min goal (3–5). It is prudent to increase exercise duration gradually so longer, continuous AT exercise bouts can be tolerated (5). An initial AT intensity equivalent to an RPE of between 12 and 13 and progressing to 16 out of 20 over time is appropriate (1–3,5). If heart rate-guided, then maintaining exercise within the target heart rate range is appropriate but may start at a lower (50%–60%) level and progress to higher percentages (60%–80%). Walking, upright and recumbent cycling, step ergometry, elliptical, seated, and recumbent stepping, rowing, swimming, and aquatic exercises are all acceptable forms of AT. For patients in CR, AT exercise selections should be dictated by their comfort and (if present) movement directional preferences. Exercises that are high-impact, like running, should be avoided or introduced gradually with caution (5). Figures 1, 2, and 3 depict recumbent combined arm and leg ergometry, treadmill walking, and upper body ergometry, three types of AT commonly prescribed during CR.

View Figure

• Download as Powerpoint
• Download Figure

View Figure

• Download as Powerpoint
• Download Figure

View Figure

• Download as Powerpoint
• Download Figure

Cardiac rehabilitation patients with comorbid CNSLBP are encouraged to follow RT guidelines for apparently healthy sedentary adults without CNSLBP (3,5) and should complete RT workouts consisting of 8 to 10 exercises—all of which emphasize major muscle groups—on 2 to 3 nonconsecutive days of the week. A variety of modalities are appropriate and include: free weights, machines, elastic resistance tubing, and body weight exercises (1–3,92,93). Patient comfort and, if present, movement directional preferences should dictate the equipment and body position selected during all RT exercises. Standing exercises may be more comfortable for patients who experience pain with trunk flexion, while seated exercises may be more comfortable for patients who experience pain during prolonged standing or with trunk extension (3,5,6,22,23,75–77). Figures 4 through 7 depict the leg press, row, Lat pull-down, and chest press exercises commonly performed during CR. An initial training intensity that is equivalent with an RPE of 12 to 13 (out of 20) or 4 to 6 (out of 10) on the OMNI RES scale is appropriate and, if tolerated, may be progressed over time (1,3,5). Although single set RT programs have produced significant strength increases in sedentary, untrained individuals (92), progressing to a protocol consisting of 2 to 4 exercise sets per muscle group is recommended as tolerated (2,3,92). Periodized, progressive, multi-set RT programs have produced significant increases in strength in persons with CNSLBP who were comparable to those in apparently healthy individuals without CNSLBP (81–83). Intensity and loading of RT exercises should follow the “two for two” rule (increase the resistance after ≥2 repetitions more than the number prescribed during the last set of an exercise can be properly completed during two consecutive workouts) (92). Table 3 describes RT exercise program modifications for patients who have movement directional preferences and are either flexion or extension intolerant.

View Figure

• Download as Powerpoint
• Download Figure

View Figure

• Download as Powerpoint
• Download Figure

View Figure

• Download as Powerpoint
• Download Figure

View Figure

• Download as Powerpoint
• Download Figure

TABLE 3. Sample machine-based resistance training exercises for flexion and extension intolerant patients.

View Fullscreen

A discussion of trunk stability and core exercise training is beyond the scope of this article. For additional resources regarding back and core conditioning exercises and management of CNSLBP, refer to McGill (24,77).

Flexibility training should be preceded by light aerobic activity for approximately 8 to 10 min daily. Static, dynamic, and proprioceptive neuromuscular facilitation stretching are all acceptable as tolerated (2,3,5). Hip flexor, hamstring, anterior shoulder girdle, and calf muscle flexibility exercises should be emphasized (3,5). Clinical exercise physiologists should use caution if signs of new or worsening pain and fatigue occur during or after exercise sessions. Signs and symptoms warranting exercise termination and prompt communication with a physician or HCP are provided in Box 5. Physician or HCP clearance for patients to return to CR exercise sessions after symptom exacerbations and flare ups is prudent.