Evaluation of occupational physical load during 6-month international crisis management operation

This is an electronic reprint of the original article. This reprint may differ from the original in pagination and typographic detail. Author(s): Title: Year: Version: Please cite the original version: All material supplied via JYX is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user. Evaluation of occupational physical load during 6-month international crisis management operation Pihlainen, Kai; Santtila, Matti; Vasankari, Tommi; Häkkinen, Keijo; Kyröläinen, Heikki Pihlainen, K., Santtila, M., Vasankari, T., Häkkinen, K., & Kyröläinen, H. (2018). Evaluation of occupational physical load during 6-month international crisis management operation. International Journal of Occupational Medicine and Environmental Health, 31(2), 185-197. https://doi.org/10.13075/ijomeh.1896.01048 2018 185 ORIGINAL PAPER Nofer Institute of Occupational Medicine, Łódź, Poland International Journal of Occupational Medicine and Environmental Health 2018;31(2):185 – 197 https://doi.org/10.13075/ijomeh.1896.01048 EVALUATION OF OCCUPATIONAL PHYSICAL LOAD DURING 6-MONTH INTERNATIONAL CRISIS MANAGEMENT OPERATION KAI PIHLAINEN1, MATTI SANTTILA2, TOMMI VASANKARI3, KEIJO HÄKKINEN4, and HEIKKI KYRÖLÄINEN2,4 1 Finnish Defence Forces, Helsinki, Finland Training Division of Defence Command 2 National Defence University, Helsinki, Finland 3 UKK Institute for Health Promotion Research, Tampere, Finland 4 University of Jyväskylä, Jyväskylä, Finland Department of Biology of Physical Activity Abstract Objectives: Generally, operational military duties are associated with a variety of stressors, such as prolonged physical activity (PA). However, limited information is available on the occupational workload or changes in PA during international military operations. Thus, the aim of the study was to investigate the changes in body composition, stress biomarkers, PA, and heart rate (HR) responses of 79 male soldiers during a 6-month international crisis management operation. Material and Methods: Measurements were conducted 3 times in South-Lebanon during the operation. Body composition was assessed by the bioelectrical impedance method. Blood samples were analyzed for serum testosterone, sex-hormone binding globulin (SHBG), cortisol and insulin-like growth factor. Saliva sampling was used for analyzing stress biomarkers, cortisol and α-amylase. Heart rate and physical activity were monitored by a recordable belt and tri-axial accelerometer, respectively. Results: Increases in muscle mass (39.2±4.1 vs. 39.5±4.2 kg, p < 0.05) and testosterone (15.9±4.6 vs. 17.2±4 nmol/l, p < 0.01), and reductions in PA variables (e.g., daily step count 9472±2547 vs. 8321±2720, p < 0.05) were observed during the first half (i.e., PRE-MID) of the study. The increase in muscle mass remained significant during the latter half (PRE-POST, 39.2±4.1 vs. 39.6±4.4 kg, p < 0.05), but also fat mass increased (MID-POST, 10.6±4.6 vs. 11.0±4.7 kg, p < 0.05) while SHBG (MID-POST, 31.8±12.1 vs. 26.6±13.2 nmol/l, p < 0.01) and cortisol (MID-POST, 445±116 vs. 400±123 nmol/l, p < 0.05) decreased. With the exception of increased concentration of salivary α-amylase (PRE-POST, 36.5±33.7 vs. 55.1±39.7 U/ml), the acute stress biomarkers and HR responses remained unchanged. Furthermore, the low quantity of PA, low HR values and subjective ratings of exertion refer to rather light physical workload. Conclusions: Due to the operatively calm nature of the working environment, the present soldiers did not express any significant signs of physical overload during the study period. Int J Occup Med Environ Health 2018;31(2):185 – 197 Key words: Workload, Military personnel, Physical exertion, Occupational health, Military medicine, Accelerometry Funding: The Scientific Advisory Board for Defence (Finland) and the National Defence Foundation (Finland). Received: June 21, 2016. Accepted: January 2, 2017. Corresponding author: K. Pihlainen, Finnish Defence Forces, Training Division of Defence Command, PO Box 919, 00130 Helsinki, Finland (e-mail: [email protected]). ORIGINAL PAPER K. PIHLAINEN ET AL. IJOMEH 2018;31(2) 186 exercises, while scientific information concerning the physical strain during international military operations seems to be limited. Therefore, the purpose of this study was to investigate changes in body composition, blood and saliva stress biomarkers, volume and intensity of PA, and heart rate responses during the 6-month crisis management operation in the Middle East. MATERIAL AND METHODS Subjects and ethics More than 250 soldiers were deployed for 6 months in the crisis management operation in the Middle East, out of whom 79 male soldiers took voluntarily part in this study. Before the deployment, the soldiers were examined by a physician. They were informed of the study design and gave written consents for their participation. The study was conducted in accordance to the guidelines of the Ethical Committee of the Central Finland Health Care District. All measurements were carried out 3 times, mainly inside the military base in South-Lebanon. The initial measures (PRE) were conducted after a 2-week acclimatization period. The respective measurements were repeated 9 (MID) and 19 (POST) weeks after the initial measures. Study protocol and conditions The soldiers served in a unit with the mission of monitoring the cessation of hostilities and supporting the government of Lebanon as well as the local population. The military base in which the soldiers were mainly accommodated was situated on a hill, 775 m above the sea-level. The most typical task for operative soldiers was patrolling for 4–6 h/day by vehicles around the area of the operative responsibility. Typical operative duties also consisted in daily guarding of the military base for one to 8 h. Soldiers in the headquarters and logistic units worked mainly inside the base. The operative units worked in 3 shifts INTRODUCTION Many of the operational military duties have been characterized as prolonged, low intensity physical activity (PA) intermittent by shorter bouts of higher intensity activities [1,2]. Military tasks are often performed with extra loads and protective equipment such as body armor, which increase the energy expenditure of such activities [1,3–6]. In addition to physical strain, negative energy balance, sustained readiness and sleep deprivation, high ambient temperature, altitude and environmental toxins may all separately or in combination disturb homeostasis of the body and thus, increase stress of soldiers [1,2,7]. Consequently, these stressors may lead to degraded performance and increased risk for illnesses and task or mission failure [2,7]. Internal or external threats in a military environment may lead to acute stress modifying the function of the autonomic nervous system that may be indirectly evaluated by studying metabolic and neuroendocrine responses such as vagal activity of the heart and catabolic (e.g., cortisol) or anabolic biomarkers (e.g., testosterone, insulin-like growth factor-1) [2,8]. An increase in the concentration of catabolic hormones and stressful situations per se may activate immune function [8]. Prolonged stress may weaken the immune function and lead to various diseases or syndromes such as hypertension, atherosclerosis and metabolic syndrome [9]. Acute occupational physical workload may be assessed by several field measurements, such as recording of cardiorespiratory responses [5], analyzing stress biomarkers from blood and saliva samples [2,10–12] as well as quantifying PA by accelerometers [13,14]. In a follow-up of chronic stress development, the same methods may be used during military operations. In addition, changes in body mass or body composition constitute an essential part of the follow-up since many of the deleterious effects of the degraded performance are associated with body weight loss [1,2,10,11]. Most of the military studies examining occupational workload have focused on field OCCUPATIONAL WORK LOAD DURING MILITARY OPERATION ORIGINAL PAPER IJOMEH 2018;31(2) 187 The inter-assay coefficients of variance (CV) for assays of TES, SHBG, COR and IGF-I were 7–7.2, 4.5–6.2, 4.6–5.8 and 3.7–7.4%, and that of sensitivity 0.5, 0.02, 5.5 nmol/l and 2.6 pmol/l, respectively. The workload assessment was conducted by using heart rate (HR) recording, saliva sampling, and accelerometer to measure PA. The measurement methods were guided to the soldiers in advance at the military base but implemented during their duties in an operational environment. Heart rate (HR) was recorded up to 3 days by a recordable memory belt (Memory belt, Suunto, Vantaa, Finland). Individual absolute and relative mean HR were analyzed for a 24-h period by a computer analysis software (Firsbeat PRO, Firstbeat Technologies, Jyväskylä, Finland). Physical activity was recorded by a tri-axial accelerometer at a frequency of 100 Hz (Hookie AM20, Traxmeet, Espoo, Finland). The device was positioned to the left side of the trunk at the height of the hip with an elastic band. The soldiers were instructed to wear the accelerometer for 10 days at all times with the exception of sleeping and water activities (e.g., shower). Minimum requirement for the inclusion of accelerometer data for further analyses was 4 days with at least 10 h of wearing time each day. The accelerometer data was analyzed for metabolic equivalent (MET) intensities and step counts by using a mean amplitude deviation according to the previously published validation [15]. Saliva samples with concurrent ratings of perceived exertion (RPE) [16] were collected 6 times during one typical working day by using cotton swabs according to the manufacturer’s guidelines (Salivette, Sarstedt, Nümbrecht, Germany). The saliva samples and RPE were instructed to be self-collected after a normal night’s sleep, immediately at the time of wake-up followed by 30 min, 1 h, 4 h and 10 h after wake-up. The last sample was collected just before going to bed for a night-time sleep. With the exception of the first sample the soldiers were instructed to rinse around the clock, while the logistic units worked mainly during a day-time. However, there were separate individual duties among all personnel groups that required 24-h readiness. The security situation at the operation area remained relatively calm throughout the study period. Nonetheless, the situation was continuously susceptible to rapid changes causing soldiers to conduct their daily duties in a peaceful environment while simultaneously being forced to remain vigilant of different types of threats. The average ambient temperature, recorded in one-hour intervals throughout the 6-month study period (Thermochron iButton, Maxim Integrated, San Jose, California, USA) inside the military camp was 22.3±4.3°C (range: 11–36°C). The soldiers had air-conditioning in their accommodation, and no heat illnesses were reported during the study period. Measurements Body composition measurements and blood sampling were conducted in the morning after an overnight fast at a military hospital. Body height was measured to the nearest 0.1 cm by using a wall-mounted height board (Seca Bodymeter 206, Seca, Hamburg, Germany). Body mass (BM), skeletal muscle mass (SMM), fat mass (FATM) were determined to the nearest 0.1 kg by using the segmental multi-frequency bioimpedance analysis assessment (InBody 720, Biospace, Seoul, South Korea) in accordance with the manufacturer’s guidelines. Blood samples were drawn from the antecubital vein. Plasma and serum were separated from blood by using a centrifuge (1000 rpm, 8 min) and frozen below –20°C for the purpose of further transportation and analysis. Assays for serum testosterone (TES), sex-hormone binding globulin (SHBG), cortisol (COR) and insulin-like growth factor-1 (IGF1) were performed by Immulite 2000 XPi (Siemens Healthcare, Llanberies, UK) using commercial chemiluminescent enzyme immunoassay kits according to the manufacturer’s guidelines. ORIGINAL PAPER K. PIHLAINEN ET AL. IJOMEH 2018;31(2) 188 Firstbeat Technologies, Jyväskylä, Finland) as the highest recorded HR during the running test. Statistics Commercial software (IBM SPSS 22.0.0, Chicago, USA) was used for the purpose of the statistical analyses. Data was analyzed by using repeated-measures ANOVA and t-tests when appropriate. If the model was statistically significant, pairwise group and time comparisons were performed. If assumptions were not to meet logarithm, transformations were applied, or finally nonparametric tests utilized. The relationships among relative changes of the measured variables were tested for linearity with Spearman’s product moment correlation coefficients. The p < 0.05 was used for establishing statistical significance. Soldiers were divided into 2 groups according to their tasks for group-wise comparison. The soldiers in the operative infantry units formed group A (N = 41) while headquarters and logistic units formed group B (N = 38). Due to the demands of high readiness, the present soldiers were not able to attend all the measurements. Therefore, a maximum number of soldiers who took part in all PRE-, MIDand POST-measurements were used in statistical analyses for each variable, and the results are also presented for the total subject group (i.e., group A+B). Physical characteristics of the soldiers are presented in the Table 1. their mouth with water 10 min prior to sampling. The soldiers were also informed to keep the sealed sample containers in a dry and, if possible, cool place during their duties. The samples had been delivered to the military base hospital on the following morning of sampling and stored at –20°C until they were transported in a frozen state for the purpose of further analysis. The samples were thawed and centrifuged at 3500 rpm for 10 min. Saliva cortisol (saCOR) and α-amylase (saAA), as potential determinants of stress [17,18], were analyzed. Saliva cortisol was analyzed by Immulite 2000 XPi (Siemens Healthcare, UK) using chemiluminescent enzyme immunoassay kits, while saAA assays were performed by Konelab 20XTi (Thermo Fisher Scientific, Vantaa, Finland) using the enzyme photometric measurement method (inter-assay CV 13.2% and 3.2%, respectively). Daily mean values from all ratings (RPE) and samples (saCOR, saAA) were formed for the purpose of further statistical analyses. Peak HR (HRpeak) was determined during a 3000-m running test inside the military base. The subjects were instructed to complete the test with a maximal effort and in the shortest possible time. Heart rate was continuously recorded by using the recordable memory belt (Memory Belt, Suunto, Vantaa, Finland). Peak heart rate was determined by the computer analysis software (Firsbeat PRO, Table 1. Physical characteristics of male soldiers taking part in the 6-month international crisis management operation Variable Study group total (N = 79) A (operative infantry units) (N = 41) B (headquarters and logistic units) (N = 38) Age [years] (M±SD) 29.8±8.0 26.4±5.6 34.1±8.6 Body height [cm] (M±SD) 179.1±7.4 180.0±7.8 178.0±6.7 Body mass [kg] (M±SD) 79.4±8.1 79.1±7.1 79.9±9.2 Body mass index [kg/m2] (M±SD) 24.5±2.4 24.0±1.9 25.1±2.7 M – mean; SD – standard deviation. OCCUPATIONAL WORK LOAD DURING MILITARY OPERATION ORIGINAL PAPER IJOMEH 2018;31(2) 189 Serum TES concentrations increased from PRE-MID in the total subject group (13±31%, p < 0.01) and the group A (12±24%, p < 0.01) (Table 2). In contrast, SHGB decreased in both groups from MID-POST (group A; –18±34%, p < 0.01, group B; –9±22%, p < 0.05) as well as from PRE-POST (group A; –19±35%, p < 0.05, group B; –14±24%, p < 0.01). Cortisol decreased significantly from MID-POST in the total subject group (–5±33%, p < 0.05) and the group A (–14±38%, p < 0.01). These changes led to significant increases in the TES-to-SHBG ratio (TES/SHBG) from PRE-POST as well as from MID-POST in all groups. The TES-toCOR ratio (TES/COR) increased accordingly, but only in the total subject group and in group A. A significant group difference was observed in the TES/SHBG (p < 0.05) and TES/COR ratios (p < 0.01) during POST. No changes in IGF1 were observed during the study in either group. However, the group A showed higher IGF1 conRESULTS Body composition and blood biomarkers Body mass remained unchanged during the first half of the study period (from PRE-MID), while significant increases were observed during the latter part (from MID-POST) in the total subject group (A+B, 1±2%, p < 0.01) and in the group A (1±2%, p < 0.05). Skeletal muscle mass increased from PRE-MID by 1±3% in the total subject group (p < 0.05), while the increases from PRE-POST were significant in all groups (Table 2). The group B reduced FATM from PRE-MID (– 4±24%, p < 0.05) and regained it from MID-POST (6±14%, p < 0.05). No differences between the groups were observed in BM and SMM during the study while FATM was higher in the group B in all comparison points. Individual increases in SMM were associated with individual decreases in SHBG (r = –0.33, p < 0.05, N = 60) as well as saAA (r = –0.39, p < 0.05, N = 41) from MID-POST. Table 2. Male soldiers’ body composition and serum biomarkers in the beginning (PRE), middle (MID) and at the end (POST) of the 6-month international crisis management operation Variable PRE MID POST Body mass [kg] (M±SD) total group (N = 79) 79.40±8.10 79.30±8.20 79.90±8.80*,** group A (N = 41) 79.10±7.10 79.10±7.20 79.60±7.60** group B (N = 38) 79.90±9.20 79.60±9.30 80.10±10.00 Skeletal muscle mass (SMM) [kg] (M±SD) total group (N = 79) 39.20±4.10 39.50±4.20* 39.60±4.40* group A (N = 41) 39.80±4.00 40.00±4.10 40.10±4.30* group B (N = 38) 38.60±4.20 38.80±4.30 39.00±4.50* Fat mass (FATM) [kg] (M±SD) total group (N = 79) 11.00±4.80 10.60±4.60 11.00±4.70** group A (N = 41) 9.70±3.70 9.50±3.70 9.90±3.70 group B (N = 38) 12.40±5.50#11.70±5.20*,# 12.20±5.40**,# Testosterone (TES) [nmol/l] (M±SD) total group (N = 59)a15.90±4.60 17.2±4.00* 17.30±3.60 group A (N = 29) 16.30±5.40 18.0±4.10* 17.90±3.50 group B (N = 30) 15.50±3.80 16.5±3.90 16.80±3.80 ORIGINAL PAPER K. PIHLAINEN ET AL. IJOMEH 2018;31(2) 190 the groups was the higher mean HR24h in the group A as compared to B during POST (p < 0.05). Individual increases in mean HR24h were associated with individual decreases in IGF1 (r = –0.46, p < 0.05, N = 25) from PRE-MID. No significant changes were observed in saCOR concentration. However, saAA increased from PRE-POST in the total subject group (108±203%, p < 0.05) as well as in the groups A (116±189%, p < 0.05) and B (103±217%, p < 0.05). While no differences were observed between centrations at all time points as well as lower COR at POST (p < 0.05). Workload assessment The 24-h HR (HR24h) responses of soldiers are presented in the Table 3. No changes within the groups were found in mean, minimum or peak HR24h in relation to time. However, relative HR decreased in the total subject group (A+B) from PRE-MID (–2±8%, p < 0.05). The only difference between Variable PRE MID POST Sex-hormone binding globulin (SHBG) [nmol/l] (M±SD) total group (N = 59)a32.30±12.00 31.80±12.10 26.60±13.20*,** group A (N = 29) 31.00±13.40 32.40±15.70 25.50±16.40*,** group B (N = 30) 33.60±10.50 31.20±7.50 27.70±9.30*,** Testosterone to sex-hormone binding globulin ratio (TES/SHBG) [nmol/l] (M±SD) total group (N = 59)a0.54±.020 0.60±0.21 0.80±0.43*,** group A (N = 29) 0.58±.021 0.64±0.25 0.95±0.55*,** group B (N = 30) 0.50±.019 0.55±0.16 0.65±0.18*,**,# Insulin-like growth factor 1 (IGF1) [pmol/l] (M±SD) total group (N = 59)a27.40±9.90 27.60±10.20 25.90±9.80 group A (N = 29) 31.90±9.20 33.00±9.00 28.80±10.80 group B (N = 30) 23.00±8.50#22.30±8.60#23.10±7.90# Cortisol (COR) [nmol/l] (M±SD) total group (N = 59)a425.00±101.00 445.00±116.00 400.00±123.00** group A (N = 29) 420.00±108.00 476.00±127.00 368.00±138.00** group B (N = 30) 429.00±96.00 414.00±98.00 430.00±99.00# Testosterone to cortisol ratio (TES/COR) [nmol/l] (M±SD) total group (N = 59)a0.04±0.02 0.04±0.01 0.05±0.02*,** group A (N = 29) 0.04±0.02 0.04±0.01 0.05±0.02*,** group B (N = 30) 0.04±0.01 0.04±0.01 0.04±0.01# Group A – operative infantry units; group B – headquarters and logistic units. a Due to the demands of high readiness, the soldiers (N = 79) were not able to attend all the measurements. Therefore, a maximum number of soldiers who took part in all PRE-, MIDand POST-measurements were used in statistical analyses for each variable. * Within-group comparison: significantly different from PRE (p < 0.05). ** Within-group comparison: significantly different from MID (p < 0.05). # Between-group comparison: significantly different from group A (p < 0.05). Other abbreviations as in Table 1. Table 2. Male soldiers’ body composition and serum biomarkers in the beginning (PRE), middle (MID) and at the end (POST) of the 6-month international crisis management operation – cont. OCCUPATIONAL WORK LOAD DURING MILITARY OPERATION ORIGINAL PAPER IJOMEH 2018;31(2) 191 A positive correlation was observed in the MID-POST individual changes between RPE and COR (r = 0.41, p < 0.05, N = 25). Physical activity The accelerometer data was collected for 9.3±2.5, 9.6±3.1 and 9.6±2.8 days during PRE, MID and POST, respectively. The respective daily wearing times of the accelerometer were 14:27±1:39 h:min, 13:45±1:40 h:min the groups in saAA during the study, saCOR concentration was higher in the group B (p < 0.05) during POST (Table 3). A positive correlation in the individual changes between saCOR and SHBG (r = 0.30, p < 0.05, N = 43), as well as saAA and mean HR24h (r = 0.37, p < 0.05, N = 41) were observed from PRE-POST. The daily mean RPE of soldiers (group A+B, N = 24) remained unchanged (9±1) throughout the study and no withinor between-group differences were found. Table 3. Male soldiers’ 24-h mean heart rate (HR) responses and saliva stress biomarkers in the beginning (PRE), middle (MID) and at the end (POST) of the 6-month international crisis management operation Variable PRE MID POST HRmean 24h [bpm] (M±SD) total group (N = 26)a72±6 70±7 71±8 group A (N = 15) 70±6 70±8 71±10 group B (N = 11) 73±7 69±6 71±7 HRmin 24h [bpm] (M±SD) total group (N = 26)a47±5 46±5 47±5 group A (N = 15) 47±6 47±5 48±6 group B (N = 11) 46±3 46±5 46±5 HRpeak 24h [bpm] (M±SD) total group (N = 26)a147±18 139±21 148±19 group A (N = 15) 145±15 141±27 140±19 group B (N = 11) 149±20 138±17 153±18# HR24h [% HRpeak] (M±SD) total group (N = 26)a37.6±3.8 36.5±3.9* 37.2±4.6 group A (N = 15) 36.1±3.2 36.1±4.7 36.7±5.4 group B (N = 11) 38.7±3.9 36.7±3.5 37.5±4.0 Saliva cortisol (saCOR) [nmol/l] (M±SD) total group (N = 34)a14.2±5.4 15.0±6.3 17.4±7.1 group A (N = 14) 11.1±2.7 13.2±3.5 13.8±7.7 group B (N = 20) 16.4±5.7 16.3±7.5 19.9±5.4# Saliva α-amylase (saAA) [U/ml] (M±SD) total group (N = 39)a36.5±33.7 49.1±35.3 55.1±39.7* group A (N = 16) 34.9±24.0 52.5±49.5 55.5±45.1* group B (N = 23) 41.1±41.0 46.8±21.8 54.9±36.5* Explanations as in Table 2. ORIGINAL PAPER K. PIHLAINEN ET AL. IJOMEH 2018;31(2) 192 ject group and the group B (Table 4). Nonetheless, the group B was generally more active than group A in all PA levels. The daily step count of soldiers (A+B) decreased from the initial levels by –10±24% (9472±2547 vs. 8321±2720, p < 0.05) from PRE-MID and by –7±29% (9472±2547 vs. 8517±2772, p < 0.05) from PRE-POST. In the group level, a significant reduction was observed in the group B (–12±25%, 10 594±2122 vs. 9288±3133, p < 0.05) from PRE-POST. Again, the PA of group B was significantly higher during PRE (10 594±2122 vs. 8291±2460, p < 0.01) and MID (9515±2985 vs. 7065±1720, p < 0.01) as compared to group A (Figure 1). The changes in running steps were non-significant in all comparisons (Figure 2). High and 14:13±1:47 h:min. In relative terms, the total subject group (A+B) spent 76±6% of wearing time at a level of sedentary behavior (MET < 1.5) during PRE (Table 4). The relative volume of sedentary time increased by 2±6% in the total subject group and by 3±6% in the group B from PRE-POST (p < 0.05). However, in absolute terms (h:min), the increased sedentary time was observed in the total subject group (A+B, 5±12%, p < 0.05) and the group A (4±9%, p < 0.05) from MID-POST. A significant reduction in the absolute volume of light PA (MET = 1.5–3) was observed only in group B (–12±29%) from PRE-MID (p < 0.05). Concurrent reductions in absolute and relative volumes of moderate PA (MET = 3–6) were observed in the total subTable 4. Male soldiers’ mean absolute and relative volume of physical activity in different metabolic equivalent (MET) intensities in the beginning (PRE), middle (MID) and at the end (POST) of the 6-month international crisis management operation Variable PRE MID POST absolute [h:min] (M±SD) relativeb [%] (M±SD) absolute [h:min] (M±SD) relativeb [%] (M±SD) absolute [h:min] (M±SD) relativeb [%] (M±SD) MET < 1.5 total group (N = 39)a11:04±1:44 76±6 10:41±1:41 78±5 11:08±1:42** 78±5* group A (N = 19) 10:58±1:32 78±5 10:46±1:29 79±5 11:13±1:44** 79±5 group B (N = 20) 11:10±1:57 75±6 10:37±1:53 77±6 11:03±1:42 77±5* MET 1.5–3.0 total group (N = 39)a1:45±0:26 12±3 1:38±0:22 12±3 1:39±0:25 12±3 group A (N = 19) 1:35±0:20 11±3 1:37±0:18 12±2 1:33±0:22 11±3 group B (N = 20) 1:55±0:26#13±3 1:38±0:26* 12±3 1:45±0:27 12±3 MET 3.0–6.0 total group (N = 39)a1:27±0:23 10±3 1:17±0:21* 9±3* 1:16±0:22* 9±2* group A (N = 19) 1:17±0:19 9±2 1:10±0:15 9±2 1:11±0:16 9±2 group B (N = 20) 1:36±0:24#11±3 1:24±0:24* 10±3#1:21±0:26* 9±3*,** MET > 6.0 total group (N = 39)a0:10±0:09 1±1 0:09±0:08 1±1 0:10±0:09 1±1 group A (N = 19) 0:09±0:09 1±1 0:07±0:05 1±1 0:08±0:08 1±1 group B (N = 20) 0:12±0:09 1±1 0:11±0:09 1±1 0:12±0:09 1±1 b Presented as % of accelerometer wearing time. Other explanations as in Table 2.