Pedersen, Mogens T. PhD; Blangsted, Anne K. PhD; Andersen, Lars L. PhD; Jørgensen, Marie B. MS; Hansen, Ernst A. PhD; Sjøgaard, Gisela PhD, DrMedSc
* Review previous research on the benefits of worksite physical activity programs on outcomes such as spinal pain, physical fitness, and blood pressure.
* Describe the benefits of the two worksite physical activity interventions evaluated in this study, including effects on physical capacity, general health, and productivity.
* Discuss the effects of specific resistance training versus all-around physical exercise on neck, shoulder, and back pain and on maximal oxygen uptake.
It has been proposed that humans inherited genes that were evolved to support a physically active lifestyle, and that physical inactivity therefore causes disease.1 Indeed, a number of lifestyle-related disorders and diseases have emerged over the past decades concurrent with a more sedentary lifestyle, especially at work.2–5 Diseases related to metabolic syndrome, cardiovascular diseases, and musculoskeletal disorders account for the majority of public health problems, and physical activity has been shown to counteract a number of these.1,6,7 Worksite physical activity programs seem to be a feasible way of conducting primary prevention. Both strength training and all-round physical exercise (APE) have proven effective for relieve of musculoskeletal pain symptoms.8–12 A recent study on trapezius myalgia showed that involvement of the painful muscle during rehabilitation is necessary to achieve marked reduction of pain symptoms.13 Altogether, there is modest to strong evidence of the efficacy of physical activity programs on neck and lower back pain, but it is uncertain which exercises are most efficient for relieving such symptoms.
Interestingly, evidence for the effectiveness of worksite physical activity programs on physical fitness, blood pressure, and general health is inconclusive.10 In general, APE charging the aerobic capacity has proven efficient for improving metabolic and cardiovascular health.6 Part of the reason for not finding an effect in some studies might be that the physical activity regimens were not sufficient in terms of type, intensity, and frequency.14,15 An ongoing discussion is whether exercises must be specific for the intended improved health outcome, such as specific strength training for reduced neck, shoulder and back pain, and whole body aerobic exercise for reduced cardiovascular risk factors, or whether there may be transfer effects from all exercises of sufficient volume to improve several diverse health outcomes. More randomized controlled studies are needed including contrasting physical activity regimes and assessment of various health outcomes other than the neck and lower back.10
Physical capacity, in terms of maximal muscle strength and maximal oxygen uptake, may be important with regard to musculoskeletal disorders as well as diseases related to metabolic syndrome and cardiovascular diseases, respectively. Nevertheless, it is relatively unknown whether it is gains in physical capacity per se or physical activity that is most important for reductions in musculoskeletal pain.16,17 For diseases related to metabolic syndrome and cardiovascular diseases, high values for body mass index, body fat percentage, and blood pressure are known risk factors and are therefore relevant markers when investigating health promoting physical activity programs and their long-term effect.
Worksite physical activity programs seem to be an efficient way of conducting primary prevention, and have proven effective, at least for musculoskeletal pain.10 Nevertheless, evidence for the effectiveness of worksite physical activity programs on physical fitness, blood pressure, and general health is inconclusive.10
Although health is important for the employee, the employer may be more interested in work productivity. Thus, for successful large-scale integration of worksite physical activity interventions, it is important to document whether changes in productivity occur as well. In a cross-sectional study, vigorous physical activity and cardiorespiratory fitness, were significantly associated with self-rated overall work performance,18 suggesting that physical activity programs might have the potential to improve productivity.
The International Physical Activity Questionnaire (IPAQ) is suitable for monitoring physical activity in populations of 15- to 65-year-old adults in diverse settings, and the long form19 should be used for research requiring detailed assessment.20 Physical activity during work, transportation, housework or gardening, and leisure can be accurately quantified by the IPAQ but it is not known whether relatively small increases in physical activity from worksite interventions can be detected by the questionnaire.
We performed a 1-year randomized controlled trial to examine three worksite interventions: 1) specific resistance training (SRT); 2) APE; and 3) a reference intervention (REF) that consisted of providing information on health enhancing activities but did not include physical activity. This study was conducted to compare the effects of the interventions on physical capacity, musculoskeletal pain, risk factors, health, and productivity. Four specific hypotheses were tested: 1) physical activity interventions result in increased physical activity, as quantified by questionnaire; 2) physical activity interventions increase physical capacity, self-rated general health, and self-rated productivity more than REF; 3) specific strength training, in contrast to APE, reduces the duration of neck, shoulder, and low back pain; and 4) APE, in contrast to specific strength training, increases maximal oxygen uptake and reduces metabolic syndrome-related and cardiovascular disease-related risk factors. Finally, for comparison with a previous study,18 baseline data were analyzed for correlations between physical activity and physical capacity, musculoskeletal pain, risk factors, general health, and productivity.
An examiner-blinded cluster randomized controlled trial was conducted. The participants were office workers recruited from a Danish public administration authority, from 12 offices in geographically different locations in the eastern part of Denmark.21 Criteria for exclusion were hypertension or cardiovascular diseases, symptomatic disc prolapses or severe disorders of the spine, postoperative conditions in neck and shoulder region, history of severe trauma, and pregnancy. All participants gave written consent before entering the study. The study was approved by the regional committee for research ethics (KF 01-201/04) and was qualified for registration in the International Standard Randomized Controlled Trial Number Register on http://isrctn.org. The study was assigned a unique trial identification number: ISRCTN31187106.
A total of 2163 employees were invited to participate in the study. Of those, 1397 replied to the invitation, of which 841 were willing to participate. As previously reported, those agreeing to participate in this study had the same age, height, and body mass compared with those of their colleagues who did not agree to participate.21 Out of the 841 employees, 225 were excluded either due to the exclusion criteria or due to difficulties with logistics and resource allocation because participants were too few at a given office location. Three of the 12 offices were not offered intervention due to the latter. In total, 616 participants from 9 offices were included in the study. After the baseline measurements, an additional 24 participants were excluded, mainly due to hypertension, heart problems, or other problems constituting a health risk in connection with the physical tests. In addition, 43 participants chose to withdraw from the study at this point. The remaining 549 participants were allocated to the three interventions based on a balanced cluster randomization. In short, either two or three types of intervention were conducted at each office, with one third and two thirds of the participants being allocated to each of the interventions. Detailed information on the distribution of the different interventions at the nine offices, the number of participants in each group, the number of clusters, and their sizes etc. (according to CONSORT statements22), is available in our recently published article.21 Clusters of participants working in the same geographically located area within the office participated in the same intervention to avoid contamination of the intervention and enhance compliance.
Intervention took place for a 1-year period from February 2005 until January 2006. Questionnaires were completed and physical testing conducted during January 2005, May or June 2005 (midway follow-up), and February 2006 (1-year follow-up). The interventions were: 1) SRT, n = 180; 2) APE, n = 187; and 3) REF, n = 182. Participants in all interventions were allotted 1 hr/wk during working hours for intervention activities.
SRT consisted of traditional dynamic strengthening exercises performed with dumbbells for the muscles of the shoulder girdle and isometric exercises for the muscles of the cervical spine. The amount of specific exercise in SRT was set according to the recommendations by the American College of Sports Medicine (ACSM) for efficient gains of muscle strength in untrained individuals.23 Two of the three weekly 20-minute sessions were performed under supervision of an instructor at the worksite during working hours. The following dynamic exercises were performed in sets of 2 to 3 with 10 to 15 repetitions: shoulder extension, shoulder abduction, shoulder elevation, and shoulder abduction with emphasis on involvement of musculus supraspinatus. The participants were encouraged to add weight as soon as they were able to perform more than 15 repetitions of an exercise. Initially, two sets of each exercise were performed, which was increased to three sets after 1 month. Repetitions were gradually reduced from 15 to 10 repetitions as the training loads increased. Thereafter, the training load was maintained until 15 repetitions could be performed, where after the loads were gradually increased again. The isometric exercises for the muscles of the cervical spine were performed in the anatomical neutral position. Participants performed neck flexion, extension, and lateral flexion at intensities of 70% to 80% of maximal force during repetitions lasting 5 seconds, as in a previous study.24 Training sessions were concluded with explosive rowing and kayaking ergometer exercises for improving maximum dynamic strength in the shoulder but not for improving endurance or aerobic capacity. The exercises were performed as maximally 10 times 15 to 30 seconds all-out rowing on a rowing ergometer (Concept2, Inc., Morrisville, VT) or a kayak ergometer (Dansprint, Vanløse, Denmark) with rest intervals of 1.5 to 2.0 minutes. This type of anaerobic power-training does not improve aerobic capacity because of the very short duration (15 to 30 seconds). The training activity (type of exercise, load, sets, and repetitions) was registered by the participants in a training diary. In addition, in the follow-up questionnaires, they were inquired about their participation in SRT at the worksite.
APE consisted of various types of physical activities at the worksite. For instance, steppers were placed at the copy machines, punch bags in the hall, Nordic Walking group sessions were organized, and some participants were supplied with step counters. In addition, an 8-minute CD-based exercise program for aerobic fitness and general strength (but not specifically for the neck and shoulder area) was offered to the participants. An introductory session was given by experienced instructors, and who visited the participants at the worksite 1 to 4 times a month depending on need for instruction. The activities offered were varied throughout the year according to an activity program developed by a professional company, Dansk Firmaidrætsforbund (DFIF) in Denmark. In addition to the 1 hr/wk of training allotted during working hours, the participants in APE were encouraged by DFIF to increase their physical activity during leisure time. The primary goal of this was to motivate the participants to integrate physical activity into their daily lifestyle in a pleasant way. As a part of the motivation, the participants signed a “contract” in which they stated the ways they intended to increase their physical activity, for example by riding a bicycle to work or “work out” at a local fitness center. To stimulate the latter, participants were provided with information eg, by e-mail contact about location and opening hours of local fitness clubs, swimming pools etc. Two campaigns were run to encourage the participants to increase their physical activity: 1) “Ride your bicycle to work”; and 2) “Increase your daily physical activity.” Most of the activities involved large muscle groups and resulted in cardiopulmonary loading, but not in neck–shoulder muscle strengthening, to distinguish clearly between the two “physical-activity” interventions. Participants in APE did not fill in a training diary. Nevertheless, in the follow-up questionnaires they were inquired about their participation in APE at the worksite as well as their physical activity at leisure according to the IPAQ questionnaire (discussed below).
The participants in REF were encouraged to form groups with the purpose of improving their knowledge on health and working conditions. Some suggestions were improvements in worksite ergonomics, stress management, organization of work, or cafeteria food quality. Different activities occurred at the various worksites, since the participants themselves were responsible for organizing presentations about health-promoting activities that they found interesting, such as diet, stress management, weight loss, meditation, relaxation, and indoor climate. Staff from the National Research Centre for the Working Environment in Denmark supported their work by helping, eg, to organize the presentations at regular meetings and e-mail contacts. The participants in this intervention received the same amount of attention as the participants in SRT and APE; however, no actual changes were implemented at the worksites. In line with the two other groups, the REF participants in the follow-up questionnaires were inquired about their participation in REF activities at the worksite.
Compliance with the intervention in each group was estimated based on questions on participation in the intervention activities.25 For example, “regular participation” meant at least weekly participation in the intervention. Briefly, regular participation was attained in 54%, 31%, and 16% of the participants in SRT, APE, and REF, respectively, during the first half and 35%, 28%, and 9% during the second half of the intervention period.
The dropout rate over the first 4 to 5 months was less than 10%, but increased to 20% over the full year of intervention. At the 1-year follow-up there were 132/160/148 subjects in SRT/APE/REF. We succeeded in obtaining complete sets of data (questionnaires and physical tests) from 73% of the remaining participants, ie, 106/107/106 subjects in SRT/APE/REF were included for final analyses.
At three points during the course of the study—baseline, midway follow-up, and 1-year follow-up, the participants in SRT, APE, and REF completed questionnaires and physical tests.
Physical Activity, Musculoskeletal Pain, General Health, and Productivity.
The participants completed an internet-based questionnaire about physical activity (a Danish version of the IPAQ Long Form Questionnaire19,20), musculoskeletal pain (in neck, shoulders, upper and lower back, hips, knees, feet, elbows, and wrists26), general health,27,28 and productivity.18
Total physical activity and vigorous-intensity activity performed by the participants at work, transportation, housework or gardening, and leisure were converted to metabolic equivalent task (MET)·min·wk−1 according to the guidelines for data processing of the IPAQ.29 Also, in concert with IPAQ, participants were classified into one of three categories termed High, Moderate, and Low based on their performed level of activity. Participants in high performed, on a weekly basis: a) vigorous-intensity activity on at least 3 days, achieving a minimum of 1500 MET·min·wk−1; or b) different activities 5 or more days achieving a minimum of 3000 MET·min·wk−1. Participants in moderate performed, weekly: a) 3 or more days of vigorous-intensity activity of at least 20 min/d; or b) 5 or more days of moderate-intensity activity or walking of at least 30 min/d; or c) 5 or more days of different activities achieving a minimum of 600 MET·min·wk−1. Participants who did not meet the criteria for the two other categories were placed in the low category. High and moderate meet the recommendations set by the American College of Sports Medicine.30
Duration of musculoskeletal pain during the last 3 months was rated on a 5-step ordinal scale: “How many days have you had trouble in (body part) during the last 3 months?” (0 days; 1 to 7 days; 8 to 30 days; >30 days; every day). General health was rated on a 5-step ordinal scale27,28: “How is your general health?” (bad; rather bad; good; very good; excellent).
Productivity was rated on an 11-step ordinal scale18,31: “How do you perceive your overall productivity the last 4 weeks?.” The rating went from 0 (the worst a worker could do) to 10 (the best a worker in the same job could do).18
Maximal Muscle Strength.
Tests of maximal voluntary isometric muscle strength were performed for shoulder elevation, shoulder abduction, hand grip, back extension, and back flexion according to a standardized procedure.32 Subjects were instructed to gradually build up force over 5 seconds, to keep the maximal force for another 2 seconds, and to finally reduce force slowly. The tests were performed at least three times for each exercise. If the third test resulted in more than 5% higher force than either of the previous two tests, a fourth test was performed. A maximum of five tests were performed. Strong verbal encouragement was given during all tests. The individual setting of the testing equipment was noted at the baseline test and used again when testing at midway and 1-year follow-up. The personnel testing the participants were blinded with regard to which intervention each subject participated in.
Maximal Oxygen Uptake.
A submaximal cycle ergometer test was conducted to estimate maximal oxygen uptake.33 An Ergomedic 874 E cycle ergometer (Monark AB, Varberg, Sweden) was used for this test. The initial power output was estimated based on age and estimated fitness, and was typically 30 to 90 W at the predetermined cadence of 60 revolutions·min−1. Heart rate was measured with a POLAR Sport tester heart rate monitor (Polar Electro OY, Kempele, Finland). If the heart rate was less than 110 beats·min−1 after the first minute, power output was increased with the goal of achieving a heart rate of 60% of the estimated maximal heart rate reserve capacity, and at least 120 beats·min−1. If heart rate had reached a steady state, defined as less than 5 beats·min−1 change from the 5th to the 6th min, the test was terminated and heart rate was registered. Otherwise, the participant continued cycling until a steady heart rate was reached. The maximum duration of cycling was 10 minutes. Subsequently, the power output and corresponding heart rate were used to estimate maximal oxygen uptake using the Åstrand-Rhyming nomogram with correction for age.33
Height, Body Mass, Body Mass Index, Body Fat Percentage, Blood Pressure.
Height of each participant was measured. Weight and body fat percentage were measured with a TBF-300 body composition monitor (Tanita UK Limited, Middlesex, UK). Body mass index was calculated as (body mass, in kg)·(height, in m)−2. Blood pressure was measured with a UA-779 blood pressure monitor (A&D Instruments LTD, Abingdon, UK). All measurements were performed by trained clinical personnel (physiotherapists and physiologists) who worked together as a calibrated team.
Interventions were compared by multivariate analyses of variance (MANOVA), ie, analyses were performed with intervention (SRT, APE, REF) as factor. Nevertheless, due to low statistical power, SRT and APE were collapsed subsequently for analysis in case of no difference between these two groups. MANOVAs were applied (SRT or APE vs REF, and correspondingly SRT vs APE) to test for an intervention effect on physical activity, physical capacity (maximal muscle strength measures and maximal oxygen uptake), metabolic syndrome-related and cardiovascular disease-related risk factors (body mass index, body fat percentage, and blood pressures), duration of musculoskeletal pain (each body part), self-rated general health, and self-rated productivity. Cluster was added as a nested random effect to adjust for the clustered randomization, and all analyses were performed on an intention to treat basis. The numbers of subjects participating in the mid and 1-year follow-up in SRT/APE/REF were 137/140/135 and 106/107/106, respectively.
At baseline, analysis of variance was applied to test for differences at baseline between participants being dichotomized into low-moderate or high (level of physical activity). The variables tested were maximal muscle strength (all measurements), maximal oxygen uptake, body mass index, body fat percentage, blood pressures, duration of musculoskeletal pain (all body parts), self-rated general health, and self-rated productivity. Linear regression analysis was applied to analyze for associations between the same variables and total weekly physical activity as well as weekly vigorous-intensity activity.
Data are presented as average (SD), unless otherwise indicated. The significance level for the main effects were set to P < 0.05. Due to multiple post hoc comparisons the significance level was set to P < 0.01 and P < 0.02 for one- and two-sided post hoc testing, respectively.
Total physical activity at baseline for all participants, regardless of intervention, averaged 4270 (3971) MET·min·wk−1, and vigorous physical activity averaged 915 (1627) MET·min·wk−1. No changes occurred in these two physical activity variables during the course of the study.
The MANOVA showed a time by group interaction for maximal right and left shoulder elevation strength (P < 0.01). Post hoc tests showed that SRT and APE increased this strength variable from baseline to 1-year follow-up, whereas there was no change for REF as shown for right shoulder in Fig. 1C. No changes were seen in back extension, back flexion, shoulder abduction, or hand grip strength (Figs. 1A and B). Although the MANOVA did not show a time by group interaction for maximal oxygen uptake, the value for APE of 37.0 (8.9) ml·kg−1·min−1 at the 1-year follow-up was higher than the baseline value of 35.2 (8.6) ml·kg−1·min−1 (t test; P < 0.05).
The MANOVA showed a time by group interaction for duration of pain in the right shoulder (P < 0.01) and in the low back (P < 0.05). Post hoc tests showed that pain in the back (P < 0.01) and right shoulder (P < 0.01) decreased for SRT and APE from baseline to 1-year follow-up (Fig. 2) with an overall mean decrease of around 30% in days during the last 3 months.
Metabolic Syndrome- and Cardiovascular Disease-Related Risk Factors.
The MANOVA showed time by group interaction for body fat percentage (P < 0.01) and systolic blood pressure (P < 0.001). Post hoc tests showed that body fat percentage and systolic blood pressure decreased for SRT and APE from baseline to midway follow-up (Figs. 3A and B) with overall mean values of 2.2 body fat% and 6.4 mm Hg. There were no significant differences between groups at baseline for these variables. There were no changes in diastolic blood pressure or body mass index.
There were no changes in self-rated general health during the study period.
There were no changes in self-rated productivity during the study period.
The physical activity of the participants is presented in Fig. 4. A total of 18% of participants were classified in the low category, 30% in the moderate, and 52% in the high category (Fig. 4A). Vigorous-intensity activity of the participants is presented in Fig. 4B.
Participants’ characteristics, physical capacities, and metabolic syndrome- and cardiovascular disease-related risk factors at baseline are presented in Table 1 according to both gender and activity category. Maximal oxygen uptake was higher in the group of High activity level versus the combined group of low-moderate level (P = 0.02).
Pain duration in neck, shoulders, and back at baseline for men and women is presented in Table 2. For elbows, wrists, hips, knees, and feet, 78% to 91% of the participants reported “0-days” pain or “less than 8 days” pain during the last 3 months.
Self-rated general health and self-rated productivity at baseline are presented in Figs. 5A and B. Data for men and women were collapsed because no differences between genders were seen.
Total weekly physical activity was correlated with self-rated general health, whereas total weekly vigorous-intensity activity was correlated with right shoulder elevation strength, maximal oxygen uptake, duration of neck pain, body fat percentage, and self-rated general health (Table 3). No other correlations were identified.
The main finding of the present study was that the worksite physical activity interventions resulted in clinically relevant effects on musculoskeletal pain as well as systolic blood pressure at 1 year, and body fat percentage at 6 months. These positive health-related adaptations occurred despite relatively small changes in physical capacity.
The first hypothesis—that questionnaire assessment could monitor worksite intervention with increased physical activity—was not confirmed. A likely explanation is that the IPAQ is not adequate to detect relatively small changes in physical activity, ie, up to 1 hr/wk in the present study compared with the several fold differences between population groups or individuals, as also seen in this study. This problem has been recognized by other authors as well,9 indicating that IPAQ should be optimized to better detect small changes over time in future intervention studies.
The second hypothesis—that worksite physical activity interventions would have positive effects on physical capacity, self-rated general health, and self-rated productivity—was confirmed for some aspects of physical capacity, but not for self-rated general health and productivity. Shoulder elevation strength was elevated for both APE and SRT, whereas aerobic fitness was increased for APE only. Although, a previous study hypothesized that physical exercise can improve productivity,18 the gains in physical capacity observed in the present study did not lead to improved self-rated productivity. It should be noted that self-reported productivity at baseline was high in the present group of employees, indicating that significant improvements were difficult to obtain. This is in line with our previous findings on workability.21 No evidence for an effect of worksite physical activity intervention on productivity or work performance is currently available,34 although multicomponent health and productivity management programs have resulted in reduced health risks and cost savings in a few organizations.35,36 Because of the inherent variance of questionnaire based assessment of productivity, more comprehensive methods of quantifying productivity should be considered, eg, by the method of Kessler et al.31
The third hypothesis—that SRT, in contrast to APE, reduces the duration of neck as well as shoulder and low back pain—was not confirmed, because not only SRT but also APE decreased duration of pain in the right shoulder in comparison with REF. Changes in pain intensity of the neck and shoulders or a combined pain measure in neck and shoulders have previously been reported and were in concert with the present finding.25,21 In addition, both SRT and APE showed a decrease in duration of pain in the lower back. The approximately 30% decrease in duration of musculoskeletal pain is considered clinically relevant, based on previous published criteria on clinically relevant changes in pain variables.37 These findings are in agreement with a systematic review8 that reported preventative effects of physical exercise on back pain, but found insufficient evidence to recommend for or against any specific kind of exercise or frequency or intensity.
The fourth hypothesis—that APE, in contrast with SRT, increases maximal oxygen uptake and reduces metabolic syndrome- and cardiovascular disease-related risk factors—was partly confirmed. Maximal oxygen uptake increased significantly in APE only, but interestingly the risk factors (body fat percentage and blood pressure) decreased for both SRT and APE compared with REF in the first part of the intervention. The 6.4 mm Hg decrease in systolic blood pressure in the SRT and APE groups combined may reduce the risk of stroke mortality by 25%.38 It is equivocal whether fitness per se or rather the level of physical activity is most important for health. In a summary from 2001, it was noted that there is a consistent gradient across physical activity groups of increased longevity and reduced risk of coronary heart disease, cardiovascular disease, stroke, and colon cancer in more active individuals.16 Another study found that when comparing subjects within a narrow range of maximal oxygen uptake (varying from 30 to 35 mL·kg−1·min−1), physical activity was more important than the level of maximal oxygen uptake, indicating better metabolic fitness among the active subjects.39
The reduction in body fat percentage and systolic blood pressure from baseline to midway follow-up in the present study is a clinically relevant finding, countering a review on the effect of worksite physical activity programs on physical activity, physical fitness, and health that found inconclusive evidence for an effect of worksite physical activity programs on blood pressure and general health.10 It should be noted that the significant reduction in body fat percentage and systolic blood pressure from baseline to mid-intervention, was not significantly preserved at the 1-year follow-up, probably due to decreased statistical power due to dropouts as well as decreased compliance during the last part of the study.25 General physical exercise has proven effective for reducing metabolic syndrome- and cardiovascular disease-related factors.6 A more controversial finding is that SRT can also have a positive effect on systolic blood pressure and body fat percentage, as also reported in a previous study.40
A comparison of our results with previous studies of the Danish population,41,42 showed that the office workers in the present study were comparable with regard to physical activity, maximal muscle strength and maximal oxygen uptake, whereas prevalence of neck, shoulder, and lower back pain was generally higher. Also, as with previous studies, musculoskeletal pain was more prevalent in women than men, and neck pain was more prevalent than pain in other body regions.42,43 For body mass index and systolic blood pressure, average values were close to upper limits for “normal values” (body mass index >25; systolic blood pressure >140 mm Hg), and maximal oxygen uptake was generally low, as in the general population. These findings indicate a potential for overall health improvement.6
According to the IPAQ data, approximately 80% of the participants of the present study (ie, moderate and high physical activity groups) were classified as active, in terms of meeting the recommendations of the American College of Sports Medicine.30 Nevertheless, estimates of physical activity based on the IPAQ long form are around 10% higher than direct measurements of physical activity.44 The low fitness observed in the present participants supports that the level of physical activity was overestimated. A study of the Danish population45 showed that more than 40% of all adults did not fulfill the recommendations for physical activity put forth by the Danish National Board of Health (DNBH). These recommendations state that people should be physically active at a moderate intensity for at least 30 minutes every day, 7 days a week and not only 5 days a week according to the ACSM. A major part of the participants in the moderate activity category in Fig. 4A would have been classified as “not sufficiently active” according to the DNBH recommendations. In fact, it is likely that more than 30% of the participants in the present study did not fulfill the DNBH recommendations for physical activity. Total physical activity and vigorous activity in this study was also higher than that found in a study of the Swedish population that used the IPAQ short form,46 reinforcing the tendency for high estimates by the IPAQ long form.
Of note is the wide range of physical activity (large SD-values) among participants in this study, which allows identifying possible relationships between physical activity and various health outcomes. The observed positive correlation between vigorous-intensity activity and shoulder elevation strength and maximal oxygen uptake in the present study confirms a well known association between vigorous-intensity activity and physical capacity.33 The baseline analysis also showed that the most intensively physically active workers had the highest self-rated general health. Indeed, the present results support results from numerous studies showing that physical exercise counteracts a number of lifestyle-related chronic poor health conditions.1,6,7 Still, the relationship between physical activity and neck pain was only significant for vigorous-intensity physical activity, indicating that the intensity of the physical activity may play a role in prevention of specific musculoskeletal pain. Nevertheless, it should be noted that the baseline study does not reveal causation, and further studies are needed to clarify the optimal dose of training intensity, volume and frequency on musculoskeletal pain symptoms. Indications for an association between physical activity and productivity are equivocal. Our baseline data showed that self-rated productivity was not higher among the most physically active participants, a finding that agrees with another study47 that found no associations between physical activity (or cardiorespiratory fitness) and work productivity. Nevertheless, a different research group that studied the associations between lifestyle-related modifiable health risks factors and work performance18 found significant associations between moderate- and vigorous-intensity physical activity (as well as cardiorespiratory fitness) and self-rated overall work performance. Lack of such findings in the present study may be due to the rather high self-rated productivity at baseline, ie, a low range of variability. Overall, our interpretation of our baseline data is that physical activity, including moderate-intensity and in particular vigorous-intensity activity may be an effective intervention, although we recognize that baseline associations are not evidence for causal relationships.
There are inherent limitations associated with the IPAQ in detecting the relatively small changes in physical activity with physical activity interventions of 1 hr/wk at work. In IPAQ, the subjects report activity during “work, transportation, housework/gardening, and leisure.” The intervention added duration of physical activity is not an explicit option in any of these categories, because physical exercise during working hours is considered neither “work” nor “leisure” a problem which has been recognized by other authors as well.9 Thus, the IPAQ is not constructed to detect the level of “physical exercise/training during working time.” An additional explanation may be that a fairly high percentage of participants in the moderate and high intensity physical activity category were reported at baseline, which may partly explain the lack of significant change in the level of physical activity. Another limitation is the low compliance rate and high dropout, eg, only 2/3 of the study participants completed the questionnaires at follow-up, resulting in decreased statistical power. Furthermore, compliance was assessed only retrospectively by questionnaires and a more detailed real time assessment eg, by interview, check lists, or specially developed diaries would have improved this information. Although, it should be noted that participation based on questionnaire replies are fairly related to actual participation based on training diaries (r = 0.72).25 Similarly, “general health” and “productivity” was assessed by questionnaires and not by detailed clinical screenings and workplace observations which could have detected more subtle changes.
SRT and APE resulted in clinically relevant reductions of musculoskeletal pain symptoms and systolic blood pressure at 1 year and body fat percentage at 6 months postintervention. These positive health related adaptations occurred despite relatively small changes in physical capacity. The IPAQ questionnaire did not allow monitoring the physical activity introduced by the intervention. No significant changes in self-rated productivity and general health were noted probably due to high levels at baseline. In the baseline cross-sectional analyses, participants being most intensively physically active had the highest physical capacity and the best self-rated general health.
The study was supported financially by funding from the Ministry of Culture Committee on Sports Research N200310016 and the National Board of Health under the Ministry of the Interior and Health. The contribution in terms of allowing approximately 600 employees to participate in the interventions during working hours, 1 hr/wk for 1 year, was sponsored by the public administration authority involved. SRT was supervised by the Department of Exercise and Sport Sciences, University of Copenhagen, and APE was supervised by Dansk Firmaidrætsforbund (DFIF). REF was supervised by the National Centre for the Working Environment. The authors would like to express their gratitude for excellent technical support to technician Dorte Ekner and physiotherapist Klaus Hansen.
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