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Original Research

The Response of Persons With Chronic Nonspecific Low Back Pain to Three Different Volumes of Periodized Musculoskeletal Rehabilitation

Kell, Robert T; Risi, Alaina D; Barden, John M

Author Information
Journal of Strength and Conditioning Research: April 2011 - Volume 25 - Issue 4 - p 1052-1064
doi: 10.1519/JSC.0b013e3181d09df7
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Abstract

Introduction

Back pain is a prevalent health issue that nearly all will experience, with the most common diagnosis being chronic nonspecific low back pain (CLBP) (8). Various predictors have been suggested to denote improvements in CLBP, and among these, pain, disability, and components of quality of life (QoL) are considered to be important (24). Low back pain often presents with reduced muscular strength and endurance (32) and increased pain, disability, and reduced QoL (27). Frequently, the back pain initiates a fear-avoidance cycle, further reducing physical activity and thus muscular strength, thereby perpetuating the chronic condition (41). There are a few rehabilitation options, one of which is whole-body muscle strengthening (3,13,16,26,28).

Research has shown that nonperiodized whole-body resistance training (i.e., weightlifting) (3,13,16,22,23,26,30,39) may reduce CLBP symptoms (e.g., pain, disability). By increasing whole-body muscular strength and endurance activities of daily living become easier, reducing the accumulation of fatigue and thus the potential for injury and pain.

As one of the most effective methods of increasing muscular strength is via a periodized training model (34), it seemed logical that if a nonperiodized model was beneficial in rehabilitating CLBP, the application of a periodized model may also be beneficial. Periodization was initially developed for the purposes of training and conditioning athletes (29) but was recently adapted to rehabilitate those with CLBP (23). Kell and Asmundson (23) compared whole-body periodized resistance training (i.e., weightlifting) with periodized aerobic training. Sixteen weeks of periodized resistance training (periodized musculoskeletal rehabilitation [PMR]) produced significantly (p ≤ 0.05) greater improvements in pain, disability, and QoL in those with CLBP than did periodized aerobic training (23).

The manipulation of training volume and intensity are important considerations in the design of an effective resistance training program for healthy persons (25). Similarly, volume and intensity should be important variables when designing PMR for those with CLBP, but a search of the low back pain literature revealed no existing research addressing the influence of volume (variation in repetitions [reps]) in the efficiency of the rehabilitation program. One study was found that compared exercise for the treatment of chronic spinal pain at a frequency of 2 vs. 3 days per week (33). The findings indicated that the outcomes obtained from the 2 exercise frequencies were similar. However, the programs used a combined therapy approach (i.e., step aerobics, strength and endurance equipment, and stretching), and the difference in the volume between the 2 frequencies could not be quantified (e.g., noted in time not reps). Thus, the question remains as to how much training volume (number of reps) elicits the best results (e.g., decrease pain) in the rehabilitation of those with CLBP.

The purpose of this study was to examine the influence of 3 different PMR training volumes (reps per week) on a sample of middle-aged untrained males and females with CLBP. Specifically, the purposes of this study were to determine (a) which PMR training volume (4D, 1,563 reps per week; 3D, 1,344 reps per week; and 2D, 564 reps per week) is most effective at improving strength and QoL while reducing pain and disability and (b) if there are any significant (p ≤ 0.05) associations between changes in strength and pain, disability, and QoL. The initial hypotheses were that (a) PMR would produce statistically significant (p ≤ 0.05) improvements in muscular strength, pain, disability, with the 3 and 4 day per week PMR training volumes being most effective and (b) significant relationships would exist between improved strength and pain and disability.

Methods

Experimental Approach to the Problem

In the treatment of CLBP, some research has indicated that nonperiodized whole-body musculoskeletal strengthening is a beneficial rehabilitation (2,13,16,22,23,26,30,39). However, the application of a periodized model, initially designed for sport training (29) and considered to be more effective at producing strength gains than a nonperiodized model (34), has only been applied to CLBP rehabilitation in one study (23). The present study is an extension of our initial research that found periodized resistance training (i.e., weightlifting) to be significantly (p ≤ 0.05) more effective than periodized aerobic training in CLBP rehabilitation (23). However, the present study will address the influence of training volume (reps per week), which has yet to be adequately addressed within the CLBP literature. Three different training volumes (reps per week) will be used to determine the influence on strength, pain, disability, and QoL. Thus, the purpose of this study was to examine the influence of training volume in a PMR program on those with CLBP. To attribute the differences between the groups to volume, the training intensity, exercise type, exercise order with a muscle group, rest time, and intensity were held constant across the 3 exercise groups (38). Thus, any variation in exercise effect would be associated with volume and not, for example, intensity or rest time.

Subjects

The subjects (n = 240) were recruited throughout the province of Alberta via word of mouth and advertisement. All subjects read the information letter and had an opportunity to ask questions, after which they were informed of any experimental risks and completed 2 standardized forms. These forms included an informed consent form and physical activity readiness questionnaire. Thus, all subjects gave their free and informed consent before participation in the study. The study met the approval of the Faculty of Education, Extension, and Augustana Research Ethics Board at the University of Alberta for the use of Human Subjects.

The inclusion criteria were men and women between the ages of 18 and 50 years and a diagnosis of chronic (≥3 months, ≥3 days per week) nonspecific (soft tissue in origin) low back (lumbar 1-5) pain (visual analogue scale [VAS] ≥ 3) by a physician. The mean duration of the back pain was 37.2 months (range 14-109 months). The most common symptoms registered by the subjects were diffuse pain in the lumbar region and fatigue at the end of the day. Potential subjects were excluded from participation if they had been diagnosed with any of the following: pain below the knee, spinal stenosis, herniated or ruptured disc(s), spondylolisthesis, infection in the lumbosacral area, tumor(s), scoliosis, rheumatologic disorder, osteoporosis, or previous back surgery. Subjects were also excluded if they were using any prescriptive or nonprescriptive pain medication. Furthermore, any subjects with a medical history of metabolic, endocrine, cardiovascular, or neurological disease were excluded from participation. The Godin Leisure-Time Exercise Questionnaire (GLTEQ) had a mean value of 13.1 and a range of 8-22. The GLTEQ indicated that the present physical activity level of the subjects was not habitual and ranged between sedentary and low (15). Thus, the volunteers were untrained. The subjects had no history of formularized resistance training experience. The control (C) group volunteers were able to seek any necessary medical, physical therapy, and/or chiropractic treatment during the course of the study but were precluded from beginning any formalized exercise (i.e., weight training) regimen. After completion of the study, the C group subjects were provided a 12-week (weeks) PMR program of their choice, that is, a 2 days per week (2D), 3 days per week (3D), or 4 days per week (4D) program. Thirty-three subjects dropped out of the study before completion; their data were not included in the results. Dropout rate was determined by the subjects contacting the researcher and indicating that they either no longer wished to participate or missing one testing session. Subject compliance was 84%, which was based on a short questionnaire completed at the conclusion of the study. Noncompliance was considered: (a) missing 2 consecutive training sessions or 3 or more training sessions in a 4-week period, (b) not completing the prescribed number of sets within a workout session, (c) changing the exercise order within a workout session, or (d) not adhering to the prescribed rest time between sets. Not all subjects returned the exercise compliance questionnaires at the conclusion of the study (47% returned), and as a result, noncompliance was not used as an exclusion criteria.

Data Collection

The duration of the study was 16 weeks in total, with the initial 3 weeks addressing familiarization and the remaining 13 weeks focusing on PMR (i.e., weight training). Table 1 outlines the duration and testing and training periods of the study. Information was provided on exercise technique (video and illustrations), warm-up, cooldown, and attire. Because each subject was permitted to complete his/her PMR program at a facility of his/her choice, the brand of fitness equipment was not consistent. Most of the resistance equipment used in the study was (a) Atlantis Strength Equipment (Laval, QC, Canada), (b) Life Fitness (Schiller Park, IL, USA), (c) Body-Solid Equipment (Forest Park, IL, USA), (d) Magnum Fitness System (Milwaukee, WI, USA), or (e) Hoist Fitness Systems, Inc. (San Diego, CA, USA).

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Table 1:
Training volume.*†

Familiarization Phase

The familiarization period was used to acquaint the subjects specifically with the (a) repetition maximum (RM) protocol, (b) exercise movements (e.g., neuromuscular control), and (c) exercise order and more generally with the surroundings of their selected fitness facility. The subjects completed a 5 RM test on exercises 1-10 (Table 2). The initial testing session determined the loads (resistance in kilograms) for the 2 weeks of familiarization training. Familiarization training consisted of completing 2-3 sets of exercises 1-13 (Table 1), at 55-60 percent (%) of 1RM, 10-12 reps per set, with a 1-minute rest between sets and exercises. The subjects were asked not to vary the exercise order (Table 2) as it may influence outcome measures. Of note, no 5RM testing was conducted on abdominal (Ab) or low back exercises (i.e., core area exercises 11-13). The Ab and Swiss ball crunch exercises initially used body weight as resistance, but once the subjects could complete 30 consecutive crunches, a free weight was added with the subjects holding the free weight on their chest. The prone superman was body weight resistance only, 10 reps each set, with the isometric contractions held from 5 to 30 seconds rep. The progressive overload was administered by increasing the duration of the isometric contraction at the discretion of the subject.

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Table 2:
Exercises, muscles, and equipment.*

Periodized Musculoskeletal Rehabilitation

Baseline testing followed the familiarization training and set the loads for each resistance exercise for the next 3 weeks. Testing occurred every fourth week throughout the study. Immediately after the baseline testing, the subjects were age, sex, strength (i.e., bench press and leg press) and pain matched and randomly assigned to 1 of 4 groups. The groups were 2D (n = 60; men, n = 40; women, n = 20), 3D (n = 60; men, n = 38; women, n = 22), 4D (n = 60; men, n = 41; women, n = 18), and C (n = 60; men, n = 37; women, n = 23). All outcome questionnaires (see Pain, Disability, and Quality of Life section) were completed at baseline and at weeks 8 and 12 testing sessions. The outcome measures were changes in strength (bench press, lat pull-down, and leg press), body mass (kg), % body fat, pain, disability, and QoL. Those subjects assigned to the C group stopped all resistance exercise training after the familiarization period. The subjects assigned to the 2D, 3D, and 4D groups received a PMR program to continue training.

The goal of the PMR program was to systematically and progressively overload each muscle group to maximize strength gains in a safe manner. A traditional periodized training program was used, with variation in the volume (number of reps) between groups (independent variable), but exercise selection, general exercise order, intensity, and rest time were held consistent among the 3 groups (Table 2). Training volume was operationally defined as the total number of reps performed per week and training intensity as the amount (kilograms or pounds) lifted or RM used to perform a certain number of reps (12). A similar periodized resistance training program was previously used and produced good results, with minimal complaints of delayed onset muscle soreness (23).

The 2D and 3D groups performed all PMR exercises on the same day (Table 2). The 2D group completed the PMR on Monday and Thursday, whereas the 3D group completed the PMR on Monday, Wednesday, and Friday (Table 2). However, the 4D group used a split routine that trained chest, back, and core on Monday and Thursday and legs, shoulders, and core on Tuesdays and Fridays. As a result of the split routine, the exercise order could not be identical between all groups but was identical for the 2D and 3D groups. However, within each muscle region, all exercises were completed in the same order (e.g., leg press, leg extension, and leg curl).

Outcome Measures

Physical Characteristics

Anthropometric and body composition measures were standing height (meters), body mass (kg), lean body mass (kg), and % body fat. Measurements were taken at designated locations in or near the communities of the volunteers. Standing height was measured with a wall-mounted metric tape to the wall (nearest 0.5 cm). Body mass, lean body mass, and % body fat were measured by bioelectrical impedance (TBF-300A; Tanita Corporation of America, Inc., Arlington Heights, IL, USA) to the nearest 0.1 kg and 0.1% body fat. Body composition measurements were performed with the volunteers having clean bare feet and at approximately the same time of day and hydration level to ensure validity and reproducibility (36).

Strength Measures

Proper exercise technique was demonstrated for all subjects, and helpful illustrations and video were provided to reinforce proper technique. Five RM testing was completed on all subjects, from which each subject's 1RM was predicted. The 5RM was determined in ≤4 sets. The 3 tests used to monitor strength changes were (a) bench press, using an Olympic barbell, flat bench, and weights; (b) leg press, with pin-operated plates; and (c) lat pull-down, a cable lat pull-down machine with pin-operated plates. Briefly, bench press starting position was hands gripping bar about shoulder with apart and arms extended, the barbell and weight was lowered to touch the chest, and then the elbows were extended raising the barbell back to the starting position (1 rep). The leg press started with the knees flexed to a 45° angle; back flat against the support knees were extended to near lockout and then returned to starting position (1 rep). The lat pull-down used a slightly wider than shoulder width grip, with the bar being pulled from above the head down to the front of the neck (near suprasternal notch) and then raised back to the starting position (1 rep). All reps on each strength test were completed in a smooth controlled movement.

Pain, Disability, and Quality of Life Measures

Three valid and commonly used measures to measure pain, disability, and QoL are the VAS, Oswestry Disability Index (ODI), and the Short Form-36 Health Survey (SF-36), respectively (9,11,14). All volunteers completed health surveys at baseline, week 8, and week 12. These included a VAS, the ODI, and the SF-36). The VAS is a simple self-reported visual scale (ratio scale) used to measure how much back pain the volunteer experienced during a typical week (21). The scale is on a continuum from 0 to 10 (10 cm in length), with 0 indicating no pain and 10 indicating extreme pain. The ODI has been used for 25 years and is a disease-specific measure for low back function. A 0 indicates no disability, whereas a 100 indicates severe disability (10). The scoring of the ODI is completed by summing the points from each category dividing by 50 and multiplying by 100 (11). The categories include (a) pain intensity, (b) personal care, (c) lifting, (d) walking, (e) sitting, (f) standing, (g) sleeping, (h) sex, (i) social life, and (j) traveling. The SF-36 is a comprehensive measure of health-related QoL and is useful for comparing the relative burden of various diseases. It contains 36 items and yields 8 domains (parameters): (a) physical functioning, (b) physical role, (c) bodily pain, (d) general health, (e) vitality, (f) social functioning, (g) emotional role, and (h) mental health (5). A detailed description of each domain can be found in other articles (20). The domains are scored on a scale of 0-100, with 0 indicating the worst possible health and 100 indicating the best possible health. Physical functioning contains 10 items that assess physical activity limitations (e.g., climbing stairs). The domains physical and emotional role measure work or daily activity problems that result from physical or emotional health problems. Bodily pain assesses limitations due to pain, whereas vitality measures energy and tiredness. The social functioning domain assesses the effect of physical and emotional health on normal social activities. Mental health evaluates happiness, nervousness, and depression. The general health perception domain appraises personal health and the expectation of changes in health. These 8 parameters can be used to derive 2 composite scoring summaries: (a) Physical Composite Summary (PCS: physical functioning, role physical, bodily pain, and general health perceptions) and (b) Mental Composite Summary (MCS: vitality, social functioning, mental health, and role emotional) (42).

Statistical Analyses

All values were reported as mean and SD (mean ± SD), with significance set at the 0.05 level (p ≤ 0.05) for all comparisons. Separate 3 (Time: baseline, week 9, and week 13) × 4 (training: control, 2, 3, and 4) repeated measures analysis of variance were performed for each dependent variable of interest. When a significant F ratio was achieved, Scheffé's post hoc comparisons were conducted to test differences between training condition means at one time. Statistical power was determined to be 0.97 for the sample size used with the outcome measures in this study. To address the meaningfulness of the improvements in the strength and health survey variables, the effect size (ES) was calculated using Hedges' g, which employs a pooled SD (the SD of the baseline values for the respective group combined with the SD for the training condition) and correction factor (18). As proposed by Cohen (7), an ES value of 0.2 indicates a small difference, 0.5 indicates a moderate difference, and ≥0.8 suggests a large difference between means. Percent change was calculated {([posttest treatment group mean − pretest treatment group mean]/pretest treatment group mean) × 100} on each of the strength test and health survey variables. To assess test-retest reliability, intraclass correlations (ICCs) comparing baseline with week 12 were completed using the C group data on the following dependent variables: bench press, leg press, lat pull-down, PCS, and MCS (43). There was a mean intraclass correlation coefficient of 0.86 and a range from 0.73 to 0.97. Statistical power was determined to range from 0.79 to 0.86 for the sample size used with the outcome measures in this study. The Pearson's product-moment correlation coefficients (r) were computed to determine the ability of one variable to predict changes in another. The C group data were used as opposed to the PMR training group's data as little variation was expected within the C group, thus providing a better assessment of test-retest reliability.

Results

As there were no statistically significant interactions, simple main effects were pursued (differences between periods within a specific training condition), which were evaluated using the Scheffé's comparison.

Physical Characteristics

Table 3 presents subject characteristics (n = 240; n = 60 per group). The 4D and 3D training volumes showed a significant (p ≤ 0.05) increase in body mass (kilograms) and reduction in % body fat from baseline to week 13, whereas the 2D training volume did not. There were no significant (p ≤ 0.05) differences between the training volumes on body mass or % body fat.

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Table 3:
Physical characteristics of participants.*

Musculoskeletal Strength

Table 4 shows the musculoskeletal strength data and the associated ES (Hedges' g). All groups except the C group demonstrated significant (p ≤ 0.05) increases in strength (i.e., bench press, lat pull-down, and leg press) from baseline to week 9 and baseline to week 13. The percent increase in bench press, lat pulldown, and leg press strength is shown in Figure 1. The ESs (Hedges' g) at weeks 9 and 13 are strong (ES = 1.02-2.81) in all training groups. As well, the 4D and 3D training groups showed significant (p ≤ 0.05) increases in strength from weeks 9 to 13 on all strength tests, whereas the 2D training group realized significant (p ≤ 0.05) strength improvements on bench press and lat pull-down but not leg press. At baseline, there were no significant (p ≤ 0.05) differences between the groups on any of the strength tests. However, at both weeks 9 and 13, the 4D group was significantly (p ≤ 0.05) stronger than all other groups, whereas the C group was significantly (p ≤ 0.05) weaker than both the 3D and 2D groups on all strength tests over the same period. As well, on lat pull-down and leg press, the 3D group was significantly (p ≤ 0.05) stronger than the 2D group.

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Table 4:
Changes in musculoskeletal strength.*†

Relationships Between Outcome Measures

Pearson's correlations involving changes in strength, pain, disability, and QoL were found when all training groups (4D, 3D, and 2D) were collapsed. As all training groups made significant (p ≤ 0.05) improvements in all outcome measures between baseline and week 13, we collapsed the training groups to determine the overall relationship (association) between whole-body muscular strength and pain, disability, and QoL. The absolute correlations ranged from low to moderate strength. Table 5 displays the correlations for each of these relationships with significance set at p ≤ 0.05. A positive correlation between pain and disability (r = 0.82) was found, indicating that pain decreased when disability decreased.

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Table 5:
Displays the correlations between changes in strength and other outcome variables at week 13.†‡

Pain, Disability, and Quality of Life

Changes in pain, disability, and QoL and the related ES are presented in Table 6. The 4D, 3D, and 2D groups all demonstrated significant (p ≤ 0.05) improvements from baseline to week 9 and from baseline to week 13 in pain, disability, and QoL. Effect sizes ranged in size strength from moderate (EF ≥ 0.5) to strong (ES ≥ 0.8). The 4D, 3D, and 2D groups also demonstrated significant (p ≤ 0.05) improvements from weeks 9 to 13 in QoL (PCS and MCS). Groups 2D and 3D did not show significant improvements from weeks 9 to 13 in pain and disability, whereas group 4D did (p ≤ 0.05). At baseline, there were no significant (p ≤ 0.05) differences between any of the groups on any of the variables. By the conclusion of the study, group 4D showed significantly (p ≤ 0.05) less pain and disability and improvements in the QoL (PCS and MCS) as compared with all other groups. At weeks 9 and 13, the 2D and 3D groups showed significant (p ≤ 0.05) improvements in QoL and reductions in pain and disability as compared with the C group. No significant (p ≤ 0.05) differences were found between the 3D and 2D groups on any of the variables at weeks 9 or 13.

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Table 6:
Changes in pain, disability, and QoL.*

Discussion

The present study measured the effect of exercise volume on CLBP (p ≤ 0.05) and attempted to minimize the influence of confounding variables (e.g., prolonged aerobic activity and pain medication). This study showed that unsupervised PMR (i.e., periodized resistance training) can be an effective rehabilitation for CLBP and that the volume of PMR prescribed is important. The overall impact of the PMR programming was positive, improving strength and QoL, while reducing pain and disability in all training groups. However, the 4D PMR volume (mean of 1,563 reps per week) demonstrated the best results as compared with the 2D (mean of 564 reps per week) or 3D volumes. The 4D and 3D training volumes (mean of 1,563 and 1,344 reps per week, respectively) were a considerable increase over our previously prescribed volume (∼800 reps per week) (23), but most importantly, the increased volume was beneficial, with no negative effects (e.g., injury) reported by the subjects. Reduced dropout in the C groups was maintained over the 13 weeks by the promise of a PMR program following the study (i.e., an exit program).

The improved strength associated with the 4D, 3D, and 2D training volumes could not be compared directly with most other research addressing whole-body musculoskeletal rehabilitation for CLBP, as past research did not speak to muscular strength changes before and after training (2,13,16,22,26,39). However, 2 studies provide some insight into pre- to post-training changes in muscular strength. Maul et al. (30) used a whole-body 12-week muscular strength and endurance program that was progressive in nature (∼3 days per week, ∼1 hour per session, with a minimum of 2 sets of 15 reps per exercise). This study demonstrated a small but significant (p < 0.05) increase (∼5%) in isokinetic back flexion and extension strength, at 60, 120, and 150°·s−1 in the exercise group. Previous research from our laboratory showed a significant (p ≤ 0.05) increase (∼27%) in free weight bench press strength after 16 weeks of resistance training (i.e., periodized weightlifting) in a combined male and female periodized resistance training group (23). Of note, the selected exercises, exercise order within the muscle group, and rest time were in essence the same, whereas the intensity (% 1RM) was similar between the present (50-83% 1RM) and former (53-72% 1RM) study (23). However, the exercise volume (reps × sets) in our previous periodized resistance training study had a mean of ∼800 reps per week, whereas the present study's 3D (mean 1,344 reps per week) and 4D (mean of 1,563 reps per week) training groups exceeded that volume. If we compare the studies on changes in bench press strength, the additional training volume and small increase in intensity influenced both the 3D (week 9 = 21% increase, ES of 1.25; week 13 = 32% increase, ES of 1.94) and 4D (week 9 = 29% increase, ES of 1.78; week 13 = 46% increase, ES of 2.81) groups in a positive manner. Thus, these findings support the use of a substantial training volume (500-1,500 reps per week) and intensity (50-83% of 1 RM) in the rehabilitation of those with CLBP, a volume and intensity likely comparable to that prescribed for healthy persons (25).

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Figure 1:
Percent improvement (change) in strength on bench press (A), lat pull-down (B), and leg press (C) from baseline to week 9 and baseline to week 13 for the 4D, 3D, 2D, and C groups.

The improvement in muscular strength associated with the 2D training volume was made in the absence of changes in body composition (i.e., % body fat, body mass). However, the trend in the 2D training volume was that of increasing body mass and decreasing % body fat from baseline to week 13. The 3D and 4D training volumes made small but significant (p ≤ 0.05) increases in body mass and decreases in % body fat by week 13 (Table 3). We hypothesized that the changes in body composition would accompany changes in strength in all groups. This hypothesis was primarily based on the results from previous data (23), as the CLBP musculoskeletal rehabilitation literature did not report changes in body composition from pre- to post-training. When the present study is compared with resistance training research involving healthy subjects (non-CLBP), improvements in muscular strength concurrently with changes in body composition are found (6) and improvements in strength in the absence of changes in body composition (1,19). However, it is generally accepted that strength gains in the initial ∼8 weeks of resistance training are predominantly neuromuscular in nature (17). Based on this accepted mechanism of early strength development, the primary mechanisms associated with the increased strength in the present study resulted from neuromuscular adaptations in the early stages and changes muscle hypertrophy in the later stages (17).

It is easier to compare strength gains reported in other research using non-CLBP subjects as more research exists. The strength changes made by the CLBP subjects in the training groups of the present study are comparable to the strength changes reported in literature using non-CLBP subjects. Hickson et al. (19) used a 3 days per week heavy resistance (∼80% 1 RM) training program for 16 weeks (n = 10; 5 men and 5 women) and reported a 22% increase in bench press and 29% increase in parallel squat strength. Similarly, Abe et al. (1) (n = 50; 17 men and 20 women) showed a 19-27% increase in bench press and leg extension strength after 12 weeks of strength training 3 days per week at 60% of 1 RM. Of note, the aforementioned studies are nonperiodized in design.

When compared with other periodized resistance training studies employing non-CLBP subjects, the present study's results are similar. Buford et al. (6) using 30 untrained male (n = 20) and female (n = 10) college students found a ∼25% increase in bench press and 94% increase in leg press strength after 9 weeks of high-intensity periodized resistance training. Also, a study using a 15-week periodized resistance training program (n = 60; 30 men and 30 women) found a 9.5% increase in leg extension strength (35). In summary, the strength gains made by the 3D and 4D training groups in the present study were in most cases equal to or exceeded the strength gains made in non-CLBP populations using either nonperiodized or periodized training methodology.

Although not assessed directly, another positive outcome of the PMR program was the improved ability of the subjects to more easily meet the demands of their activities of daily living regardless of volume. This was surmised indirectly from the training group subjects (2D, 3D, and 4D) having demonstrated a substantial reduction in disability as determined with the ODI and further supported by the significant (p ≤ 0.05) correlations between changes in strength (bench press, lat pull-down, and leg press) and disability and pain. In essence, as pain (r = ∼−0.75) and disability (r = ∼−0.75) decreased, strength increased. This trend was also supported by a correlation (r = ∼0.69) between strength and QoL.

All the PMR training volumes (Table 1) were successful at improving pain, disability, and QoL in those with CLBP over the course of 13 weeks (Table 6), with the 4D training volume being most effective. The improvements in pain, disability, and QoL generated via the PMR were associated with moderate (≥0.5) to large (≥0.8) ESs (Hedges' g; Table 6) and % improvements. The 4D training volume attained the greatest changes at both weeks 9 and 13 on pain (ES = 1.6, 2.4; % change = 16%, 28%), disability (ES = 0.8, 1.4; % change = 21%, 36%), PCS (ES = 0.9, 1.6; % change = 16, 31%), and MCS (ES = 0.7, 1.5; % change = 14, 27%), respectively. Similarly, the 3D and 2D training volumes elicited moderate to large ESs but not as large as the 4D training volume (Table 6, Figure 2). Again, the general trend was for a decrease in ES and % improvement as training volume decreased.

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Figure 2:
Percent improvement (change) in pain (visual analogue scale [VAS], A), disability (Oswestry Disability Index [ODI], B), and quality of life (QoL) (physical composite summary, C; and Mental Composite Summary [MCS], D) from baseline to week 9 and baseline to week 13 for the 4D, 3D, 2D, and C groups.

Notably, relationships were found between changes in muscular strength and pain, disability, and QoL. As strength increased over the course of the 13 weeks of training, moderately strong correlations were noted with decreased pain, disability, and an improved physical component of QoL. Thus, an increase in strength after whole-body PMR was associated with improved function, and the reduction in low back pain was more likely to occur in the subjects suffering more intense pain.

With respect to maintaining these benefits once the PMR programming had concluded, it is plausible that the gains in strength made by the subjects will be maintained via the physical demands of their occupation and leisure and sport pursuits. Similarly, the maintenance of reduced pain and disability has been shown to be a lasting quality (30). Maul et al. (30) found that a substantial proportion of their exercise group maintained much of the reduction in pain (48%) and improved functional ability (50%) in a 1- and 10-year follow-up.

Although not listed as a purpose of this study, the author would like to make a brief comment on the economic cost of the PMR program used in this study. It is projected based on general fitness industry costs that programs similar to the present study could be provided at a cost of ∼$40 Canadian for ∼8 weeks of programming. A fitness center membership would cost ∼$35 Canadian per month. The total yearly cost would be $680 Canadian per person (at 4 days per week = 208 sessions per year). This is a similar cost to that projected per year for the combined physiotherapy treatment (i.e., manual therapy, neurophysiology education, exercise training) $720 US ($60 US per session; 12 sessions per year) (31) or most multidisciplinary pain clinics (37). The added benefit of the aforementioned fitness center membership is that access is generally unlimited (e.g., 7 days per week) and other activities can be performed (e.g., aerobic activity, fitness classes), providing more freedom and variety. Additionally, the reduction in pain, disability, and improved QoL found in the present study is equal and in some cases better than those found in studies using a variety of other rehabilitation techniques (e.g., aerobic exercise, low back and abdominal strengthening, physiotherapy, home-based exercise) (4,28,31), making the present rehabilitation not only economical but effective.

In conclusion, a systematic review of the literature suggests that exercise therapy is generally more effective at reducing pain and disability and increasing functional ability than regular care (e.g., back schools) (40). The present study supports these findings and further identifies periodized resistance training (i.e., PMR) as an effective musculoskeletal rehabilitation for CLBP. It also points out that the volume (total number of reps) of rehabilitation is an important ingredient. Just as the prescribed volume in a training program developed for high-performance athletes is important, it is also paramount in the development of CLBP rehabilitation programs. By changing the volume of PMR programming, the amplitude of improvements in strength, pain, disability, and QoL also changed. That is, the greater the training volume the greater the improvement in strength, pain, disability, and QoL in those with CLBP.

Practical Applications

All training volumes demonstrated significant improvements in strength, pain, disability, and QoL. However, the 4 days per week PMR program was the most effective volume in the rehabilitation of CLBP. Accordingly, paying close attention to the prescription of training volume is as important for those with CLBP as it is for athletes. After a diagnosis of CLBP, the rehabilitation expert (e.g., physical therapists, training and conditioning specialists) should not hesitate to prescribe a gradual increase in training volume eventually reaching volumes similar to those associated with healthy persons. By strengthening the musculoskeletal system via weight training, the client will experience the benefit of reduced pain, disability and fatigue, and improved QoL.

Acknowledgments

The University of Alberta, Augustana Campus Research and Travel grant. I am also grateful to Dr. Donald Sharpe for his assistance with the statistical analyses.

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Keywords:

chronic pain; disability; progressive overload; weightlifting; resistance training

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