In Japan, the overall age of the population is increasing owing to a decline in the number of births and increases in average life expectancy. By 2065, elderly individuals aged more than or equal to 65 years are estimated to comprise 38.4% of the total population,1 with the proportion of elderly workers in the labor force also projected to increase.2 Therefore, elderly workers play increasing roles in the Japanese labor resource pool, and workers aged more than 60 years account for about 20% of the total number of employees, with a steady annual increase in this proportion.2
Industrial accidents (deaths or injuries among workers requiring 4 or more days of absence) in Japan have tended toward long-term decreases, but the incidence of accidents among aging workers is high. In 2017, the proportion of accidents involving elderly workers aged more than 60 years was 25%, and that involving those aged more than 50 years was 49%.3 Among these, the number of industrial accidents was highest in the manufacturing industry, which accounted for 22% of total accidents in Japan, with the number of falls found to be highest in the manufacturing industry.3 In 2013, workers over the age of 50 accounted for 62% of total industrial falls in the manufacturing industry,3 with high incidence among elderly workers. Aging has been shown to be a risk factor for non-fatal fall accidents.4,5 Therefore, we considered that decreased physical capacity (both musculoskeletal and aerobic capacity) associated with aging6–8 may cause increases in industrial accidents, including falls and lower back pain, in elderly workers. Additionally, low physical capacity was associated with poor work ability9,10 and a higher prevalence of sick leave.11 Thus, it is necessary to improve workers’ physical capacity to prevent future accidents, including falls, that ultimately result in a decreased ability to work.
Workplace physical activity (PA) interventions have been effectively administered to improve worker PA and physical capacity, as has been shown in previous reviews.12–15 Workplace PA interventions can be broadly categorized into either a group approach or individualized approach. There individualized approach encompasses various methods including supervised exercise training programs (SP) and personal-fitness management programs (PP).
The SP is used to promote PA that include resistance training and aerobic exercise under the supervision of an exercise instructor and PP involves receiving advice and guidance that promotes PA through interviews with an instructor who manages all fitness programs. Some studies demonstrated that SP improved the physical capacity of workers,16–19 while others demonstrated that SP was effective in improving or preventing deteriorated work-related outcomes.20,21
Individualized approaches used by various instructors denoted as “exercise training specialist” or “skilled instructor” among others have also been described.18,20 SP run by physical therapists (PTs) were effective for improving physical capacity and pain among workers.22,23 PTs are movement experts who optimize quality of life through prescribed exercise, hands-on care, and patient education.24 They examine each individual and develop a tailored plan, using treatment techniques to promote movement, reduce pain, restore function, and prevent disability.24 The effects of individualized approaches may change depending on instructor ability; therefore, professional qualification requirements are important. We previously demonstrated that SP by PTs was effective in improving the physical capacity of workers25; however, all the participants of this study were nurses enrolled from one hospital, and the study setting was favorable for promoting the use of exercise facilities and employed full-time PTs instructors.
Even if SP seemed to be effective for workers, SP programs have not been practically implemented in most companies. Since SP requires access to a large training room where both staff instructors and exercise machines are present, a large upfront cost is necessary. As a result of these cost concerns, group-fitness management is provided by most companies. While SP is difficult to implement, PP can be more easily implemented and includes individualized approaches; however, the evidence for the effectiveness of PP on PA is limited. To promote workplace adoption of PP, it is necessary to establish whether PP is at least more effective than group-fitness management.
This study aimed to evaluate the effectiveness of PP by PTs on physical performance among manufacturing workers. We hypothesized that PA intervention by PTs would be superior to conventional group exercise education programs performed in occupational health fields to improve the physical performance of workers.
PA was generally defined as any bodily movement produced by skeletal muscles that resulted in energy expenditure.26 In Japan, this may consist mainly of two parts: daily activity and exercise.27 Therefore, we defined interventions on PA in this study as those that primarily included exercise compared with daily activities.
MATERIALS AND METHODS
This study was an assessor-blinded randomized controlled trial that investigated whether PP was superior to group-fitness management with regard to improving physical performance. This study protocol was approved by the Ethics Committee of University of Occupational and Environmental Health, Japan (registration number: H29-013) and was registered at the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (registration number: UMIN000032535). This study complied with the Helsinki Declaration, and written informed consent was obtained from all participants of the study. Because it was a randomized controlled trial, this study used the CONSORT 2010 checklist criteria (S1 Table, http://links.lww.com/JOM/A642).
Participants and Procedure
Manufacturing industries with 469 employees were the target companies of this study. Participants were recruited via workplace advertisements, and 60 workers volunteered to participate in this study.
Participants with any history of severe cardiovascular, respiratory, musculoskeletal, and neurological diseases; those with sufficient PA (determined by the World Health Organization [WHO] recommendations,28 those who were not permitted by occupational health physicians to perform exercise due to health reasons, and those who wished to withdraw from the study within 1 year of the start date of the study were excluded).
Randomization and Blinding
Participants were randomly assigned to either the PP group (PPG) or group-fitness management group (control group, CG) at a 1:1 ratio. The randomization procedure was performed after the participants completed baseline measurements, using a computerized random number function in Microsoft Excel by a study co-author.
After allocating all participants to each group, they received elastic bands (Thera-Band®; Hygenic Corp., Akron, OH) of varying intensity, including easy, medium, or hard; a pedometer (Kenz Lifecorder GS; Suzuken, Nagoya, Japan) for PA self-monitoring; and a pamphlet describing exercises and health promotion.
Individual exercise lectures and health promoting group lectures were offered during unpaid work hours.
Interventions for PPG
The PP consisted of a monthly, face-to-face personalized education program regarding exercise and PA intervention in a dedicated workplace room for 6 months from July 2017 to December 2017. Each session lasted approximately 20 minutes. The intervention was conducted by each of the PTs with more than 5 (range: 7 to 34) years of work experience at a general hospital. The intervention during the first month was performed according to short-term (1-month) and long-term (6-month) goal settings: exercise and PA education, health guidance, and prescription of exercise and PA tailored to each participant based on their exercise habits, exercise motivation, PA level, lifestyle, and personality. All participants were prescribed a walking program and lower muscle strength training for exercise. The subsequent sessions were performed for changes in goal settings and exercise prescriptions, with additional exercise guidance as needed. The long-term goal was to improve physical fitness by increasing PA, besides including at least one of the following: weight loss, decreasing musculoskeletal pain, and health promotion in general. The education and exercise prescription was conducted based on the WHO global recommendations on PA for health28 and ACSM's Guidelines for Exercise Testing and Prescription, 10th Edition (ACSM's Guidelines).29 Interventions were administered by five PT teams, and the same PT did not necessarily coach the same subject at every session. However, every intervention included a medical chart for each subject and all information was shared across PT teams to ensure consistent intervention.
Intervention for CG
In the first month, all CG participants received a 90-minute group lecture on exercise and health-promotion related to preventing fitness deterioration, musculoskeletal pain, metabolic syndrome, and depression given by a PTs with more than 5 years of work experience at a general hospital. The education was conducted based on the WHO global recommendations on PA for health28 and the ACSM's Guidelines.29
Primary and secondary outcome measures, anthropometric, and exercise-related items, were obtained by a trained PTs, who was blinded regarding participant group allocations, at the baseline and after the 6-month intervention period. The details of the primary and secondary outcomes are described in the following sections.
The exercise-related items were assessed using a self-administered questionnaire. The stage of changes in exercise behavior was assessed using a five-point categorical scale defined as follows: precontemplation (I do not intend to in the next 6 months), contemplation (I intend to the next 6 months), preparation (I intend to in the next 30 days), action (I have been, but for less than 6 months), and maintenance (I have been for more than 6 months).30 Exercise self-efficacy was measured using a four-item survey with a five-point Likert scale ranging from “not at all confident” to “very confident.”31 Exercise self-efficacy score was the sum of the four items, and scores ranged from 4 to 20, with a higher score indicating a higher exercise self-efficacy. Exercise frequency and daily exercise times were assessed using a four-point Likert scale. The symptoms that participants were willing to improve on by exercise were measured using an eight-item questionnaire with yes or no response options.
Primary Outcome Measure: Physical Performance
The primary outcome measure was a 30-second chair stand test (CS-30) used as a simple and comprehensive indicator of physical performance.32 While the CS-30 has been widely used as an indicator of physical performance in the field of rehabilitation medicine, it has not been as widely used in occupational health studies. Since the CS-30 is an indicator that can evaluate physical performance easily without using special equipment, we expect an increase in the utilization of this indicator. CS-30 has been associated with leg press performance,32 lower muscle strength,33,34 balance,34 sensorimotor function,34 and psychological parameters.34 Participants sat in the center of a 40-cm-height chair with their arms folded. After receiving a signal to start from the assessor, participants repeatedly raised the chair and sat down as quickly as possible for 30 seconds, and the assessor counted the number of repetitions. The total number of repetitions was used for analyses. The reference values of CS-30 repetitions in participants in their 60s, 70s, and 80s were 22.15, 18.45, and 14.75, respectively.35
Secondary Outcome Measures
Grip strength was measured as an indicator of muscle strength using a Jamar dynamometer (SH5001; SAKAI med, Tokyo, Japan). Measurements were performed using a similar method used in a previous study,36 and the mean of the maximum values of dominant and non-dominant grip strengths were calculated.
The time spent standing on one leg with both eyes closed was measured as an indicator of static balance. Measurements were performed using a method described previously,37 and the test was conducted once after allowing for one practice run.
Body Composition and Physique
Body composition was measured using bioelectrical impedance analysis (InBody 770; BIospace Co. Ltd., Seoul, Korea) with measures of total body water, intracellular water, extracellular water, body fat mass, skeletal muscle mass, and body mass index (BMI) recorded. This device measured impedance of the trunk, arms, and legs separately using a tetra polar eight-point tactile electrode system. The abdominal circumference was measured using a tape measure at the umbilical level on exhalation.
Results of the comparisons between pre and post interventions were based on the intention to treat analysis. The Shapiro-Wilk test was used to evaluate normality of each outcome measure. Differences in baseline values between both groups were assessed using the two-sample t test, Mann–Whitney U test, and chi-square test. The paired t test and Wilcoxon's signed-rank test were used to compare data at baseline and after intervention within groups. Repeated measures analysis of variance was used to compare the effects of the intervention. A P-value of <0.05 was considered significant. Statistical analyses were performed using SPSS version 27.0 (SPSS Inc., Chicago, IL).
The sample size calculation was based on the primary outcome. We estimated a sample size that would detect a 2.5-fold higher score on the CS-30 in the PPG than in the CG. A 2.5-fold difference in the CS-30 score between PPG and CG was estimated in a previous study, which verified the effect of exercise, and a standard deviation (SD) of 2.9 was used in this sample size analysis.38 This estimate required at least 60 patients (30 in each group) to obtain 90% statistical power with a 5% significance level. Finally, 60 participants were included; we assumed that a few participants would drop out of the study. Sample size and post hoc power analyses were performed using STATA version 14 (Stata Corp., College Station, TX).
Participant Characteristics, Exercise-Related Items, and Adherence to Intervention
In total, 61 employees were willing to participate in this study and were assessed for eligibility. All employee volunteers were eligible for study participation, and one employee declined to participate further in the study. A final study population of 60 employees was included in this study with one participant dropping out of the CG at the start of the study due to lack of time. Study analyses were performed on the remaining 59 participants (Fig. 1).
Details of participant characteristics and exercise-related items (stage of exercise behavior change, exercise self-efficacy, exercise frequency, and exercise time per day) are presented in Table 1. No significant difference existed in any baseline variable between the two groups.
The adherence of interventions in PPG and CG were 99.4% (179/180 times) and 100% (29/29 times), respectively. Serious adverse events were not observed with only minor complains of slight pain and fatigue
Effects of Intervention in Each Group and Differences between Groups
The CS-30 significantly increased in both groups (PPG and CG: P < 0.001) after intervention. Significant group–time interaction effects were noted, and the PPG showed better improvement in CS-30 than the CG (P < 0.001) (Table 2).
Grip strength increased in both groups with a significant effect observed in the PPG (P = 0.019) and a non-significant trend in the CG (P = 0.099). Extracellular water significantly decreased (P = 0.047), and other outcomes were not significantly different in PPG. In CG, total body water, intracellular water, and skeletal muscle mass significantly increased (P = 0.009, 0.001, and 0.001, respectively), and other outcomes were not significantly different.
Significant group–time interaction effects were observed in total body water, intracellular water, and extracellular water (which indicate the distribution of water in the body) as well as in skeletal muscle mass (used to measure muscle mass; P = 0.009, 0.012, 0.012, and 0.010, respectively). Other clinical outcomes were not significantly different between the groups.
This study primarily evaluated the effectiveness of individualized workplace exercise education programs on the physical fitness of manufacturing workers. In line with our hypothesis, we demonstrated that PT administered workplace PP was effective in improving physical performance among workers in a manufacturing industry setting.
Characteristics of the Study Participants
The mean age of the participants was 48.02 (SD: 7.21) years and the baseline CS-30 was 21.78 (SD: 4.14) repetitions. A report by Tveter et al39 found that the average CS-30 value for individuals between the ages of 40 to 49 years old was 25 for women and 29 for men. Based on this the physical performance level of the subjects in this study was low compared with previous studies. Moreover, since the reference value of CS-30 for individuals in their 60s was 22.15,35 this indicated that the mean baseline results of our study population was similar to that of this age group. Thus, study participants had low physical performance levels at baseline.
Effects of Intervention on Primary Outcome (CS-30) and Physical Capacity
In this study, CS-30 was used as an indicator of comprehensive physical performance and showed significant improvement within groups following intervention in both groups, with greater improvement in PPG than in CG. Chair stand ability has been associated with lower muscle strength, balance, PA level, musculoskeletal symptoms, and respiratory symptoms.32–34,40 Many of these parameters deteriorate as age increases9,41,42; as a result, workers experience imbalances between work demands and physical capacity. Decreased physical capacity is a major risk factor for deteriorated work ability, industrial accidents including falls, and the prevalence of taking sick leave.9–11 An important study finding was that the CS-30 was more improved by personal management in the occupational health field. Grip strength is related to lower extremity muscle power, knee extension torque, and calf cross-sectional muscle area,43 and is often used as an indicator of whole body muscle strength.44 In the PPG, the improvement in grip strength similar to the CS-30 indicates that not only was physical performance improved but also that overall muscle strength had also been improved. On the other hand, while the grip strength of CG showed improved, the overall BMI also increased. Since grip strength has been positively correlated with general BMI,45 the improvement of grip strength in the CG may reflect an increase in body weight rather than any significant improvement in overall muscle strength.
Some previous studies have measured the effects of PP intervention. Arrogi et al46 reported that individualized PA counseling increased PA. Moreover, Marcus et al47 showed that PP interventions based on motivational readiness to adopt PA was effective in increasing PA. The improvement of physical performance and muscle strength in our study might be derived from the increasing PA through personal coaching by PTs. Clancy et al48 mentioned that coaches had a strong influence on worker engagement in workplace programs including PA interventions. PTs are rehabilitation medicine specialists in hospitals and have superior personal coaching abilities for disabled patients. In this study, PTs conducted individualized PA programs for every participant as a professional exercise coach. Proper et al49 revealed that individualized PA counseling in the workplace conducted by PTs was effective in decreasing the prevalence of sick leave. Our results suggest that personal coaching by PTs is effective for improving PA of workers with individual education, although no comparisons were made with other types of exercise instructors. Emphasizing the superiority of PA intervention by PTs is difficult, but we believe that PTs could play a significant role in the workplace similar to the role they play in a hospital setting. However, the PT educational curriculum in Japan includes basic medicine, clinical medicine, kinematics, and exercise physiology among other topics but does not include occupational medicine. In order to improve the quality of worker PA interventions, it may be necessary to incorporate occupational medicine components to PT education programs.
There are many types of workplace PA interventions and the effectiveness of such interventions has been highlighted by systematic reviews and meta-analyses by Conn et al12 and Malik et al.13 Notably, SP at the workplace is effective in improving lower muscle strength,23 physical capacity, work-related outcomes, and PA.16 However, introduction of SP systems has been difficult due to the associated high cost, large space constraints, requirement for training equipment, and lack of workplace exercise instruction. Conversely, PP interventions, including those demonstrated in this study, require only a monthly individualized visit by an exercise specialist and do not require exercise space or equipment. Therefore, from the viewpoint of total cost, PP might be recommended in occupational health settings. Therefore, from the viewpoint of total cost, PP is recommended in occupational health settings. Different definitions of PA intervention have been adopted in many studies, due to differences in the socioeconomic backgrounds of countries and companies. Owing to this variance in definition, comparing and stratifying study findings across multiple studies are difficult.
A significant improvement in the CS-30 was observed in the CG. This improvement may have been partly a result of self-monitoring through pedometer use. Mansi et al50 reported that pedometer-driven walking programs improved worker PA. Moreover, Bravata et al51 also found that pedometer use contributed to increase PA. Takahashi et al52 showed that pedometer and goal setting interventions did not increase the total amount of PA, but improved gait speed and grip strength. Based on these finding, we believed that the improvement of CS-30 in CG might have been partially attributable to pedometer use in addition to PT group instruction. The same may be said for PPG with regards to the pedometer effects. However, since the pedometer was used in both groups, we considered that the difference in the outcome between the two groups was mostly due to the differences in the intervention methods between the two groups.
Effects of Intervention on Physique and Body Composition
BMI, abdominal circumference, and BFM were not significantly different both within and between groups after intervention. Jakicic et al53 reported that moderate or vigorous intensity exercise with behavioral weight loss intervention resulted in significant weight loss in overweight women with sedentary lifestyles. Chambliss54 reported that overweight women with sedentary lifestyle had lost weight through combined diet and exercise regimens. These previous studies suggested that multidisciplinary interventions, including moderate to vigorous intensity exercises, are necessary to improve physique and body composition. SMM increased significantly in CG than in PPG after performing the intervention. A possible explanation for this result was that increasing the body water content increased the skeletal muscle mass in the CG.
This study had several limitations. First, there may be a self-selection bias present in this study. Participants had higher motivation for health awareness; thus, generalizing our study results to all workers would be difficult. Second, the PPG's adherence to the intervention was high (99.4%), but exercise and PA implementation status were not monitored in this study. Therefore, adherence to exercise and PA execution remains uncertain. Third, the appropriate time and frequency of interventions for improving physical capacity remain uncertain. However, a monthly 20-minute intervention improved physical capacity, although lack of time is frequently cited as one of the greatest barriers to PA intervention. Our previous study25 found that the intervention adherence was low (45% to 55%), but the PP in this study was high (99.4%), highlighting a strength of this study. Moreover, this study had a sufficient time of intervention, which also contributed to the strength of study findings. Finally, the intervention was conducted by trained PTs specializing in exercise instruction. Therefore, it remains unknown whether similar results will be obtained using similar interventions without specialized exercise instruction.
Although this study showed the effectiveness of PP at workplace for workers, these results may not be applicable to all workplaces due to the associated costs and labor requirements. If PP is expected to be individually utilized for high-risk workers with lifestyle-related diseases, future studies are warranted to examine the effects of individualized PA intervention. Moreover, it is necessary to compare this intervention to other PA interventions to identify optimal intervention methods. In addition, future study would also benefit from incorporating financial perspectives.
The authors are grateful to the staff of Renesas Electronics Corporation, Oita factory (Hiroshi Sugiyama), Kyushu Nutrition Welfare University (Keiichi Hiroshige), Sawara Hospital (Yuichiro Matsufuji), Fukuoka Mirai Hospital (Hideaki Matsuzaki, Yuria Oishi, Daiki Matsuo, and Keita Kantake), Shinnakama Hospital (Toshio Suematsu), and the University Hospital of Occupational and Environmental Health for their support in this study.
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