Effects of an exercise program on sick leave due to back pain.

Back pain is a major health problem in the industrialized countries, afflicting about 80% of the population at some time during their lives. [1] In 1983, in Sweden, which then had a population of 8.5 million people, 24% of sick-leave days were due to pain in the back, neck, and shoulders. In 1988, 54,000 people took early retirement in Sweden, 10,500 as a result of back pain (National Social Insurance Board, Stockholm, Sweden; personal communication). In 1986, the cost of sick leave and early retirement because of back pain amounted to 5.1 billion Swedish crowns (approximately $777 million in US currency). [2] A major aim for the health care services, therefore, is to prevent back pain. In Sweden, 3% to 4% of the population suffer from chronic back pain leading to work incapacity. [3] The 10% of patients with back pain having the longest periods of sick leave account for 80% of the total number of sick-leave days attributable to back pain. [4] Thus, preventing acute back pain from progressing to chronic back pain must also be our aim.

The effects of conservative treatment techniques on patients with back pain are still uncertain. [1,5] Many patients have been on sick leave too long before rehabilitation methods such as work training are considered. This delay can cause back pain sufferers to lose confidence in their ability to carry out activities such as walking, standing, sitting, lifting, and carrying. It becomes increasingly difficult to convince patients of their physical capabilities and work capacity when delays occur. [6] Furthermore, it takes a long time to learn an effective work technique and to carry out a training program to attain appropriate strength, coordination, and flexibility. Consequently, few patients manage to carry out a training program for any length of time by themselves. [7]

Positive effects from participation in a back school have been reported in patients with acute and subacute back pain. Whether the back school has a preventive effect on future back pain, however, is uncertain. [8] In a study of patients with chronic back pain, Hemborn and Holmstrom [9] found some change in the participants' attitudes toward back pain following participation in a back school, but this attitudinal change had no effect on the amount of sick leave the participants took.

There is evidence that physical activity is beneficial for both prevention and treatment of back pain. Cady and associates [10] found among fire fighters that the most physically fit individuals had fewer and less costly back injuries than the least physically fit individuals. Activity of the major muscle groups is generally thought to increase the level of endorphins in cerebrospinal fluid and to increase pain tolerance under certain conditions. (12) Delivery of nutrients to the intervertebral disk and articular cartilage is stimulated by physical exercise. (12) Nachemson (6) contends that, when there is damage to muscles, ligaments, and tendons, physical exercise improves symptoms and enhances healing. He concludes tht progressive physical activity is of benefit to patients with back pain.

Mayer and associates [13] have had success in facilitating the return to work of some patients with long periods of sick leave. Their approach utilizes principles of functional training and measurement and of disregarding pain. Their patients perform physical exercise and simulated work tasks. The focus is on what patients can do functionally. Patients' efforts in physical activity are encouraged, rather than the specific treatment of their symptoms. [13]

The Volvo Project in Gothenburg, Sweden, demonstrated that an activity program for patients with subacute lumbar pain (sick leave of 6-8 weeks) resulted in an earlier return to work for male participants than for female participants. The program consisted of a functional assessment; visits to the patients' work place; a back school; and individualized, progressive physical activity. Improved function and increased activity were encouraged, rather than a specific treatment of pain (I Lindstrom, C Ohlund, A Nachemson; unpublished research). Exercise programs to complement a back school have been introduced in Sweden. Of the participants in an exercise program specifically designed for people with back pain in Stockholm, 78% reported an improvement in their symptoms. [14] The improvement was independent of the duration of their symptoms and was the same for all age groups. In a similar study, [15] the majority of the participants reported a reduction in back pain; however, it was difficult for them to continue the exercise program independently.

Although physical activity has been shown to have these positive effects, there are no reports of the effects of physical exercise on short-term absenteeism attributable to back pain (<50 days). Ninety percent of patients with acute back pain return to work within 6 to 7 weeks. [16] The major purpose of this study was to investigate the effect of an exercise program on short-term sick leave attributable to back pain. A secondary purpose was to investigate whether changes in sick leave are related to effects on cardiovascular fitness.

Method

Subjects

The participants in this study were employees of Marbodal AB, the biggest employer in Tidaholm, Sweden, and Scandinavia's major producer of kitchen units. The management showed considerable interest in the project and gave their agreement that about 60 employees could take part in an exercise program 1 hour a week for 1 1/2 years during paid working hours. Information about the project was sent to all employees of Marbodal AB. Criteria for inclusion in the study were self-reported current or previous back pain, written commitment to participate in the exercise program during working hours, and a willingness to exercise at least once a week outside working hours for 1 1/2 years. Exclusion criteria were any period of sick leave longer than 50 days, irrespective of cause, during the 1 1/2 years prior to the study, and medical reasons affecting the employee's ability to participate in the exercise program.

Of 850 employees, 143 volunteered to participate in the study. Eighteen volunteers were rejected according to the exclusion criteria. From the remaining 125 volunteers, 58 individuals were randomly selected to form the exercise group, and the remaining 67 individuals formed the control group. Ten individuals were not interested in continuing as part of the control group because they would not be participating in the exercise program, and 4 control group subjects did not participate in the initial cardiovascular fitness test. Thus, the exercise group consisted of 58 subjects and the control group consisted of 53 subjects.

Research Design

The study used a prospective, randomized, controlled research design to evaluate the effect of physical exercise intervention on the participants' sick leave attributable to back pain. The number of days of sick leave attributable to back pain and the number of episodes of back pain were recorded during the intervention period (period 2=November 1, 1986-April 30, 1988) and compared with data recorded during a period prior to intervention (period 1=November 1, 1984-April 30, 1986). The timing of the intervention and baseline periods was chosen to eliminate the effects of seasonal variation in sick leave. The data relating to sick leave were obtained from the register of the National Social Insurance Board in Tidaholm, Sweden. Participants were guaranteed anonymity. The project was carried out in Tidaholm by personnel from The Primary Health Care Centre and the industrial nurse at the factory of Marbodal AB.

Procedure

Exercise program. The exercise group was divided into two subgroups, and each subgroup participated in the exercise program once a week during working hours. The program was conducted to music, and, to ensure variety, the program was changed every 6 months. One of the three different exercise programs is described in the Appendix. During the first 10 weeks, the program was carried out at low intensity. Participants were encouraged to perform the exercises at a speed and intensity level that did not feel strenuous or cause increased pain after the session. The main aim during these first 10 weeks was for the participants to become accustomed to movements of the arms, legs, and trunk in different positions (eg, standing upright; standing on hands and knees; lying on back, side, and front). Emphasis was placed on the harmony and rhythm of the movements. The subjects were allowed to stop and rest if an exercise was painful, and they were encouraged to find similar alternative movements that felt better for them. This meant that jumping and jogging exercises could be included.

When the participants had learned an individual intensity level that did not cause discomfort after the training session, the intensity of the program was progressively increased. The exercise intensity was progressively increased by instructions such as: "It is now time for you to increase your physical efforts so that you become warm and sweaty and feel a bit tired in your muscles afterward. If you feel pain anywhere after the session, you have done too much. On the other hand, if you do not feel tired afterward, you have done too little." There were no assesments of heart rate to estimate exercise intensity. Instead, it was emphasized that the participants must find an intensity level that suited them best. Consequently, considerable differences were observed in the participants' exercise intensity levels.

Each session started with a warm-up and gentle stretching exercises and continued with alternate strengthening and cardiovascular fitness exercises. Coordination exercises were included throughout the session. The session ended with a "warm-down" and specific stretching exercises (Appendix).

Each exercise session lasted 30 to 35 minutes and was followed by 5 to 10 minutes of relaxation, during which relaxing music was played. The participants were then instructed to tense their muscles for about 5 seconds, to relax for about 10 seconds, and finally to feel the difference. This procedure was performed for muscle groups throughout the body.

Two thirds of the sessions were led by a physical therapist assistant and a physical fitness instructor. The remaining third were led by a physical therapist (KMK), who started each class with 10 minutes of lectures relating to theories associated with traditional back schools. [19] Emphasis was placed on achieving a good prognosis for acute back pain. In the event of a recurrence of acute back pain, the participants were encouraged to be active as quickly as possible, starting with walking and swimming. Bed rest was not suggested for more than a few hours at a time. The program continued for 1 1/2 years, with breaks for the industrial holidays in 1987 (4 weeks) and Christmas 1986 and 1987 (3 weeks each). There was an average of 77% attendance at each session.

Additional exercise. In addition to the organized exercise program, participants gave a written commitment to exercise at least once a week on their own outside working hours. Each exercise session was expected to consist of walking 3 km or for 30 minutes, cycling 10 km or for 30 minutes, skiing 3 km or for 30 minutes, jogging 2.5 km or for 20 minutes, or performing a comparable activity for 30 minutes. The participants chose their own level of exercise intensity, and they kept a diary of their activities, which was handed in at the end of the project. No further control of their additional exercise was instituted.

Cardiovascular fitness. Before and after the project, the cardiovascular fitness of both the exercise and the control groups was tested using a computerized exercise cycle. (*) Each subject's oxygen uptake capacity (in milliliters of oxygen per kilogram of body weight per minute) was estimated according to the method described by Astrand. [18] This is a submaximal exercise test from which the maximal oxygen uptake is estimated. The subjects cycled at a measured exercise intensity level while the heart rate was continuously monitored until a steady state of heart rate was reached above a target level of 120 bpm. The oxygen uptake capacity was then correlated to the subject's age, sex, and weight. [18] All fitness tests were administered by a specially trained health worker with experience in fitness training.

Self-report data. At the end of the project, participants in the exercise group reported on the subjective effect of the exercise program on their back pain by anonymously answering the question, "How has the exercise program affected your back pain?" There were five possible answers: "much better," "better," "unchanged," "worse," and "much worse."

Data Analysis

To establish the equivalence of the exercise group and the control group prior to intervention, Student's t tests for independent groups were carried out on the following variables: age, body mass index (BMI) (calculated as weight [in kilograms] divided by length [in square meters]), cardiovascular fitness, sick days attributable to back pain in period 1, and episodes of back pain in period 1. Comparisons of the sick-leave data between period 1 and period 2 were performed using paired t tests for both the exercise and the control groups. Changes in cardiovascular fitness following intervention were also tested by paired t tests in both groups. In addition, the change scores (period 2--period 1) for the variables sick days attributable to back pain and episodes of back pain were compared [TABULAR DATA OMITTED] between the exercise group and the control group, using t tests for independent groups.

Results

The exercise group and the control group were first compared to ascertain the equivalence of the two groups prior to intervention (Tabs. 1 and 2). As shown in Table 1, there were no significant differences between the two groups for the variables age, BMI, or cardiovascular fitness. Table 2 shows that the groups did not differ significantly for either sick days attributable to back pain or episodes of back pain prior to intervention (period 1). The groups were equivalent with respect to sex distribution (ie, women composed 30% of each group) and the ratio between managerial and shop floor workers (eg, 1:2).

During the intervention period, the total dropout rate for the two groups was 23%. Of the 58 participants in the exercise group, 6 individuals withdrew from the exercise program for medical reasons (ie, high blood pressure, spondylolisthesis, epicondylitis, fracture, angina pectoris, and pyelonephritis). An additional 4 subjects found it too inconvenient to leave their work, and 5 subjects withdrew from the program because of an increase in pain (2 because of back pain and 3 because of neck pain). One participant started a study course that prevented continued attendance, 1 left the firm, 1 commuted with co-workers and found it difficult to be ready in time after the session, 1 started working overtime and did not want to reduce his working hours by continuing to participate in the exercise program, 1 started football training and thought he had sufficient exercise, and 1 lost interest in the program. By the end of the project, 37 participants (64%) remained in the exercise group.

Of the 53 subjects in the control group, 3 were excluded because of long periods of sick leave (>50 days) in period 2. Two control group subjects withdrew because of pregnancy. The control group thus consisted of 48 subjects (91%) by the end of the project. [TABULAR DATA OMITTED]

Sick Leave

Thirty-two percent of the exercise group took sick leave because of back pain during period 1, and 21.6% took sick leave during period 2. Twenty-seven percent of the control group took sick leave because of back pain in period 1, and 29% took sick leave during period 2. Sick-leave data for the two groups and the two data-collection periods are presented in Table 2.

Table 2 shows a significant difference between the 51.2% decrease in sick days attributable to back pain in the exercise group and the 65% increase in the control group. A similar significant difference in change scores is noted for the other sick-leave variable, episodes of back pain (Tab. 2). From the data presented in Table 2, the changes in each group were examined separately using paired t tests. In the exercise group, the number of sick days attributable to back pain decreased (t=2.29, df=36, P<.05), but there was no significant change in the number of episodes of back pain (t=1.79, df=36, P=NS). The control group did not change significantly in either sick days attributable to back pain (t=-1.34, df=47, P=NS) or episodes of back pain (t=-1.18, df=47, P=NS). Thus, it appears that the significant difference in change scores on the sick-days variable ,can mainly be attributed to changes in the exercise group. With respect to the sickness episode variable, the difference in change scores was produced because the groups changed in different directions, even though each such change was not significant.

Records of the National Health Insurance Office revealed no difference in the patterns of absenteeism in exercise group subjects who withdrew from the project because of increased pain and the four subjects who withdrew because they found it inconvenient to leave work compared with the rest of the exercise group. Their reduction in number of sick-leave days attributable to back pain in period 2 was 67%. The reduction in the number of episodes of back pain for these nine participants was 50% in period 2.

Additional Exercise

The exercise group performed exercise on their own at least once a week during the whole of period 2. The majority (n=25) chose walking combined with either cycling, jogging, or skiing. A few participants chose football, dancing, tennis, or other exercise.

Cardiovascular Fitness

The cardiovascular fitness test revealed no significant change in estimated oxygen uptake capacity between the two data-collection periods in the exercise group (preintervention: X=43.78 mL [O.sub.2.kg.sup.-1.min.sup-1], SD=9.79; postintervention: X=43.78 mL [O.sub.2.kg.sup.-1.min.sup.-1], SD=11.31, t=-.48, df=35, P=NS). A significant decreased in cardiovascular fitness, however, was observed in the control group (preintervention: X=44.36 mL [O.sub.2.kg.sup-1], SD=12.31; postintervention: X=41.86 mL [O.sub.2.kg.sup.-1.min.sup.-1], SD=10.74, t=2.46, df=47, P<.02). With consideration taken for age and sex, both groups were found to have average to above-average cardiovascular fitness on both test occasions. [18]

Self-Report Data

All participants in the exercise group replied to the question on the subjective change in their back pain. Forty-six percent of the respondents reported that they felt much better, 35% reported that they felt better, 14% reported no change, and 5% reported that they felt worse. Thus, 81% of the participants reported improvements in symptoms following participation in the exercise program.

Discussion

This study has shown that an exercise program carried out once a week for 1 1/2 years by people with back pain reduced their number of sick-leave days and their number of episodes of sickness attributable to back pain by over 50% compared with a 1 1/2-year period prior to intervention. In contrast, the control group's amount of sick leave attributable to back pain increased during the same period. The analysis of nine exercise group subjects who withdrew from the program (four stating inconvenience to leave work and five stating increased pain) revealed that they had a similar pattern of absenteeism attributable to back pain compared with the other exercise group subjects. This funding might be explained by the fact that six of these subjects participated in the exercised program for more than 1 year and three of these subjects participated between 6 and 12 months. Thus, had they remained in the exercise group, the results apparently would not have been altered.

Although there are no really available statistics on the local change in sick leave attributable to back pain between the two data-collection periods studied in this project, the total level of absenteeism in Tidaholm, Sweden, has increased. In 1985, thee average number of sick days per employee each year was 16.9; in 1987, the average number of sick days had risen to 17.8 (National Social Insurance Board, Tidaholm, Sweden; personal communication). Despite this general increease in absenteeism, the exercise group showed a decrease in sick leave during this time.

In the exercise group, the cardiovascular fitness of the participants remained at an average to high level after the project period. One training session a week was not enough to increase the level of fitness for this group. The participants' own training, which was mainly walking, apparently was not carried out at a sufficient intensity to raise the level of fitness. Cady and associates [10] have shown an inverse relationship between cardiovascular fitness and subsequent back injuries. In our study, although the participants did not significantly alter their oxygem uptake capacity, they did reduce their amount of sick leave attributable to back pain.

The control group's cardiovascular fitness decreased significantly. We considered this decrease in mean oxygen uptake capacity from 44.4 to 41.9 mL [O.sub.2.kg.sup.-1], however, to be minor. The control group was still found to have average to above-average cardiovascular fitness. We believe that this decrease is of minor importance to the control group's increase in sick leave compared with the general trend of increased sick leave in Tidaholm as reported previously.

We did not make any objective measurements of changes in back pain inthis study; nevertheless, 81% of the participants in the exercise group reported a subjective improvement in back pain. This finding is in concordance with the results of a study by Garderud, [14] who reported an improvement in 78% of the participants in a similar exercise group. Although we took no objective measurements to determine why the participants' sick leave attributable to back pain decreased, several factors in addition to the exercise protocol may have been influential. We believe it is unlikely that either the back school or the increase in general exercise levels could have had any major effect. The back school has not been shown to have any preventive effect on sick leave attributable to back pain, [8] and the participants did not increase their exercise levels to a degree that affected their cardiovascular fitness.

The effects of group support, improved attitudes toward the employer, reassurance about prognosis, and nonspecific intervention effects (eg, life-style changes) may have contributed to the positivie results obtained in our study. We believe, however, that the exercises had a major influence on the outcome. Although the exercises were not specific, because they could have been varied in many different ways, we believe that, because of the design of the exercise program and the way in which it was carried out, the results are attributable to the program. The participants were given responsibility to adapt exercises and to find an exercise intensity level that suited them. We believe that this responsibility helped the participants develop a better capacity to adapt postures in different functional activities, such as walking, standing, lifting, carrying, and sitting, which may have improved their body mechanics in their daily activities. In our opinion, the participants probably learned postures and movements that caused less strain on their back.

Traditional management of patients with back pain with rest and passive treatment has not been shown to reduce the length of sick leave or to prevent the recurrence of back pain. [1,5] Our study demonstrates that physicial activity is beneficial for reducing short periods of sick leave attributable to back pain (<50 days). There is also evidence that physical activity is beneficial in the management of subacute and chronic back pain, as shown in the Volvo project (I Lindstrom, C Ohlund, A Nachemson; unpublished research) and the work of Mayer and associates. [13]

Clinical Implications

We believe that therapeutic measures should be diverted away from passive treatment and instead directed at mobilizing patients more actively. We suggest that an exercise program can be integrated into the traditional back school and that this program should continue for 2 to 3 months so that participants can establish a training routine.

Physical therapists can interact with instructors of physical fitness classes to establish cooperation so that patients can continue with regular exercise in organized forms. Most people do not succeed in continuing with a training program on their own, [7] and it is therefore important that they are given support and encouragement to participate in group activities. It is difficult to motivate many people on a voluntary basis; therefore, the possibility of establishing exercise programs during working hours should be considered.

Conclusions

This study has shown that a weekly exercise program has resulted in a reduction of sick leave for people with relatively short (<50 days) episodes of back pain. The majority of patients who develop chronic back pain have previously had repeated short episodes of back pain. This study demonstrated that it is possible to reduce sick leave by 50%; therefore, it is probable that the number of patients developing chronic back pain can also be reduced. An investment in exercise programs for people with back pain could lead to considerable benefits for the employer, society, and individuals with back pain.

(*) Dynavit, Scheelevagen, S-302 39 Halmstad, Sweden.

References

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[11] Terenius L. Endorphines and pain. Front Horm Res. 1981;8:162-177.

[12] Holm S, Nachemson A. Variations in the nutrition of the canine intervertebral disc induced by motion. Spine. 1983;8:866-874.

[13] Mayer TG, Gatchel RJ, Kitchino N, et al. Objective assessment of spine function following industrial injury. Spine. 1985;10:482-493.

[14] Garderud A. Riskis och Svettis ryggympa: vilka deltar och med vilken effekt? Stockholm, Sweden: Metropol Foretagshalsovard; 1986.

[15] Linderoth L. Training vid ryggbesvar. SPRI U 20849; 1986.

[16] Nachemson A. Advances in low back pain. Clin Orthop. 1985;200:266-278.

[17] Zachrisson-Forsell M. The back school. Spine. 1981;6:104-106.

[18] Astrand I. Aerobic work capacity in men and women with special reference to age. Acta Physiol Scand [Suppl]. 1960;49:169.

K Kellett, BSc, is Superintendent Physiotherapist, Department of Physiotherapy, The Health Centre, Box 305, 522 00 Tidaholm, Sweden. Address correspondence to Ms Fellett.

D Kellett, MB, ChB, is General Practitioner, The Health Centre.

L Nordholm, PhD, is Associate Professor, Gothenburg College of Health and Caring Sciences, Guldhedsgatan 6, 413 20 Gothenburg, Sweden.

This article was submitted April 24, 1989, and was accepted November 20, 1990.