Causal Association Between Sedentary Behaviors and Health Outcomes: A Systematic Review and Meta-Analysis of Mendelian Randomization Studies.

BACKGROUND: Different types of sedentary behavior are associated with several health outcomes, but the causality of these associations remains unclear. OBJECTIVES: To conduct a systematic review and meta-analysis of Mendelian randomization (MR) studies investigating the associations between sedentary behaviors and health outcomes. METHODS: A systematic search on PubMed, Embase, Web of Science, Scopus, and PsycINFO up to August 2023 was conducted to identify eligible MR studies. We selected studies that assessed associations of genetically determined sedentary behaviors and health outcomes. A meta-analysis was conducted to examine the causal associations when two or more MR studies were available. We graded the evidence level of each MR association based on the results of the main method and sensitivity analyses in MR studies. RESULTS: A total of 31 studies with 168 MR associations between six types of sedentary behavior and 47 health outcomes were included. Results from meta-analyses suggested a total of 47 significant causal associations between sedentary behaviors and health outcomes. Notably, more leisure TV watching is robustly correlated with increased risks of myocardial infarction, coronary artery disease, all-cause ischemic stroke, and type 2 diabetes. Conversely, robust inverse associations were observed between leisure computer use and risks of rheumatoid arthritis, Alzheimer's disease, and gastroesophageal reflux disease. CONCLUSION: These findings suggest that different types of sedentary behavior have distinct causal effects on health outcomes. Therefore, interventions should focus not only on reducing sedentary time but also on promoting healthier types of sedentary behavior. PROSPERO REGISTRATION: CRD42023453828.

Electromyography of Sedentary Behavior: Identifying Potential for Cardiometabolic Risk Reduction.

INTRODUCTION: Muscle activation during interruptions to prolonged sedentary time is a hypothesized mechanism underlying observed cardiometabolic benefits. We examined associations of quadriceps and hamstring muscle activity patterns with cardiometabolic risk markers and how these patterns varied between different sitting-interruption countermeasures. METHODS: Electromyographic (EMG) data (shorts) were gathered for 1 to 2 days from healthy adults in a free-living study (n = 172, age 40.9 ± 12.9, BMI 23.6 ± 1.3) and a laboratory-based study (n = 12, age 47.0 ± 7.7, BMI 30.0 ± 4.7). Patterns examined were average EMG (aEMG ;%EMGMVC); EMG activity duration (% above signal baseline 3 µV); and usual (weighted medians) EMG activity bout amplitude (%EMGMVC) and duration (s). In the free-living study, these were regressed against risk markers (waist; fat percentage; fasting plasma glucose [FPG];total cholesterol; HDL;LDL; triglycerides); in the laboratory study, EMG patterns for the muscle groups were compared between sitting and the active countermeasures. RESULTS: In the free-living study, lower extremity muscles displayed minimal overall activity, with hamstrings and quadriceps using only 2.6% and 2.0% of their capacity (%EMGMVC), respectively, and being active for 30% and 25% of the time. Higher hamstring aEMG and EMG activity duration were beneficially associated with waist, HDL and fat percentage (duration only) and a longer quadriceps usual EMG activity bout duration was beneficially associated with FPG. In the laboratory study, compared with prolonged sitting, active seated or upright active-interruption countermeasures modified these EMG patterns; brief (6 min) walking and simple resistance activities (SRA) were more beneficial than was a bout of standing (30 min) with the SRAs being the only intervention that matched daily aEMG levels. CONCLUSIONS: Upright and physically active interruptions to sitting appear to be required to increase the typically low muscle engagement observed in free-living contexts, promoting muscle activity patterns that may help ameliorate cardiometabolic risk.

Association of accelerometer measured sedentary behavior patterns with cognitive functions in sedentary office workers: Insights from SMART-STEP study.

BACKGROUND: High levels of sedentary behavior in workplaces are currently recognized as an independent risk factor for cognitive dysfunction and poor mental health. However, sedentary patterns vary between workdays and non-workdays, which may influence cognitive functions. OBJECTIVE: The present study aimed to quantify and compare work and nonwork device-measured sedentary time (ST) and its association with cognitive function in Indian office workers. METHODS: In an ongoing randomized controlled trial (SMART-STEP), the baseline data of 136 full-time office workers, including accelerometer-measured sedentary patterns and cognitive functions, were analyzed. The ST was measured using a hip-worn accelerometer (Actigraph wGT3X-BT) for seven days, and executive functions were measured using computer-based tests. Linear regression models were employed to analyze the relationships between ST and executive function measures. RESULTS: The median daily ST of Indian office workers was 11.41 hours. The ST was greater on both workdays (11.43 hrs.) and non-workdays (11.14 hrs.) though different (F = 6.76, p = 0.001, ηp2 = 0.032). Office workers accumulate more prolonged sitting bouts (+21.36 min) during work days than non-workdays. No associations between device-measured ST and executive functions were observed. CONCLUSION: Indian office workers exhibited high ST patterns, especially on workdays. Although lower than workdays, Indian office workers exhibited more ST patterns during non-workdays than did their Western counterparts. Culturally adaptable workplace and leisure time physical activity interventions are needed to address the high ST of Indian office workers.

Enhanced muscle activity during interrupted sitting improves glycemic control in overweight and obese men.

The efficacy of interrupting prolonged sitting may be influenced by muscle activity patterns. This study examined the effects of interrupting prolonged sitting time with different muscle activity patterns on continuously monitored postprandial glycemic response. Eighteen overweight and obese men (21.0 ± 1.2 years; 28.8 ± 2.2 kg/m2) participated in this randomized four-arm crossover study, including uninterrupted sitting for 8.5 h (SIT) and interruptions in sitting with matched energy expenditure and duration but varying muscle activity: 30-min walking at 4 km/h (ONE), sitting with 3-min walking at 4 km/h (WALK) or squatting (SQUAT) every 45 min for 10 times. Net incremental area under the curve (netiAUC) for glucose was compared between conditions. Quadriceps, hamstring, and gluteal muscles electromyogram (EMG) patterns including averaged muscle EMG amplitude (aEMG) and EMG activity duration were used to predict the effects on glucose netiAUC. Compared with SIT (10.2 mmol/L/h [95%CI 6.3 to 11.7]), glucose netiAUC was lower during sitting interrupted with any countermeasure (ONE 9.2 mmol/L/h [8.0 to 10.4], WALK 7.9 mmol/L/h [6.4 to 9.3], and SQUAT 7.9 mmol/L/h [6.4 to 9.3], all p < 0.05). Furthermore, WALK and SQUAT resulted in a lower glucose netiAUC compared with ONE (both p < 0.05). Only increased aEMG in quadriceps (-0.383 mmol/L/h [-0.581 to -0.184], p < 0.001) and gluteal muscles (-0.322 mmol/L/h [-0.593 to -0.051], p = 0.022) was associated with a reduction in postprandial glycemic response. Collectively, short, frequent walking or squatting breaks effectively enhance glycemic control in overweight and obese men compared to a single bout of walking within prolonged sitting. These superior benefits seem to be associated with increased muscle activity intensity in the targeted muscle groups during frequent transitions from sitting to activity.

Sensitivity and specificity of measuring children's free-living cycling with a thigh-worn Fibion® accelerometer.

Objective: Cycling is an important part of children's active travel, but its measurement using accelerometry is a challenge. The aim of the present study was to evaluate physical activity duration and intensity, and sensitivity and specificity of free-living cycling measured with a thigh-worn accelerometer. Methods: Participants were 160 children (44 boys) aged 11.5 ± 0.9 years who wore a triaxial Fibion® accelerometer on right thigh for 8 days, 24 h per day, and reported start time and duration of all cycling, walking and car trips to a travel log. Linear mixed effects models were used to predict and compare Fibion-measured activity and moderate-to-vigorous activity duration, cycling duration and metabolic equivalents (METs) between the travel types. Sensitivity and specificity of cycling bouts during cycling trips as compared to walking and car trips was also evaluated. Results: Children reported a total of 1,049 cycling trips (mean 7.08 ± 4.58 trips per child), 379 walking trips (3.08 ± 2.81) and 716 car trips (4.79 ± 3.96). There was no difference in activity and moderate-to-vigorous activity duration (p > .105), a lower cycling duration (-1.83 min, p < .001), and a higher MET-level (0.95, p < .001) during walking trips as compared to cycling trips. Both activity (-4.54 min, p < .001), moderate-to-vigorous activity (-3.60 min, p < .001), cycling duration (-1.74 min, p < .001) and MET-level (-0.99, p < .001) were lower during car trips as compared to cycling trips. Fibion showed the sensitivity of 72.2% and specificity of 81.9% for measuring cycling activity type during the reported cycling trips as compared to walking and car trips when the minimum required duration for cycling was less than 29 s. Conclusions: The thigh-worn Fibion® accelerometer measured a greater duration of cycling, a lower MET-level, and a similar duration of total activity and moderate-to-vigorous activity during free-living cycling trips as compared to walking trips, suggesting it can be used to measure free-living cycling activity and moderate-to-vigorous activity duration in 10-12-year-old children.

Erratum to "A new accelerometer (Fibion) device provides valid sedentary and upright time measurements compared to the ActivPAL4 in healthy individuals" [Heliyon 8(10) (October 2022) e1103].

[This corrects the article DOI: 10.1016/j.heliyon.2022.e11103.].

A new accelerometer (Fibion) device provides valid sedentary and upright time measurements compared to the ActivPAL4 in healthy individuals.

Background: Thigh-worn accelerometers can accurately measure time spent sitting, standing and walking in free-living settings. Aim: To investigate the concurrent validity of a new Fibion accelerometer and a validated ActivPAL4 accelerometer for estimating sedentary and upright time in healthy individuals. Methods: A total of 29 healthy individuals, aged between 18 and 50 years, wore the Fibion and ActivPAL4 devices on the same thigh with a medical adhesive tape during one typical weekday. Concurrent validity of the Fibion and ActivPAL4 was assessed by comparing time spent in sitting, walking and standing using intraclass correlation coefficient and Bland-Altman plots. Results: Intraclass correlation coefficients were ≥0.843 which indicated good to excellent validity between the two devices for measuring sedentary (sitting) and upright (standing and walking) time. Analysis of the Bland Altman plots revealed a reasonable agreement for sitting, standing and walking time between both devices. No proportional bias was evident in the Bland-Altman plots. Conclusion: The Fibion demonstrated good to excellent validity in measuring sedentary and upright time compared to the ActivPAL4 in healthy individuals.

Strength-Cognitive Training: A Systemic Review in Adults and Older Adults, and Guidelines to Promote "Strength Exergaming" Innovations.

Background: Despite functional and cognitive benefits, few adults and older adults do strength training twice per week with sufficient intensity. Exercise-based active video games (exergaming) may amplify the cognitive benefits of exercise and increase adherence and motivation toward training. However, the benefits of a well-defined and monitored dose of strength training, executed simultaneously or sequentially with a cognitive element, has received little attention. In this study we have two aims: First, to systematically gather the available evidence; second, to suggest possible ways to promote strength exergaming innovations. Methods: We systematically reviewed randomized controlled trials using simultaneous or sequent combined strength and cognitive training or strength exergaming to improve cognitive or functional outcomes in adults and older adults. Results: After screening 1,785 studies (Google Scholar, ACM Digital Library, IEEE Xplore Library, PsycARTICLES, Scopus, Cochrane Library and PubMed) we found three eligible studies. Of the two studies using sequent strength and cognitive training, one showed improved functionality, but the other showed negative effects on cognition. The third study using simultaneous intervention, reported a positive influence on both cognition and function, when compared with either strength training alone or a control group. Moderate level of evidence was showed on GRADE analysis. Conclusion: The existing little evidence suggests that strength and cognitive training improves cognition and function in adults and older adults. The following suggestions may help to promote further innovation: (1) ensure minimal dosage of strength training (30-60 min, 2 × /week), (2) use machine-based strength training devices to control volume and intensity (to prevent cognitive components from interfering with strength training), (3) include power training by using cognitive tasks requiring rapid reactions, and (4) add cognitive memory tasks (to extend the cognitive benefits of strength training per se), and (5) include motivational exergame elements to increase adherence.

A Greater Intrinsic, but Not External, Motivation Toward Physical Activity Is Associated With a Lower Sitting Time.

Background: Both reducing sitting and increasing physical exercise promote health but exercising more does not necessarily reduce sitting time. One reason for this non-dependency may be that different aspects of exercise motivation are differently related to sitting time. Identifying the type of exercise motivation that would also be associated with sitting time can help to reduce sitting indirectly through increased exercise, thus bringing greater benefits. Methods: The present study explored the association between quality of motivations toward physical activity with physical activity and sitting time in a total of 373 adults (age range = 23-81; women n = 256). The short version of international physical activity questionnaire (IPAQ) was used for measuring physical activity and sitting time. Reasons for exercising regularly were measured with the Self-Regulated Questionnaire-Exercise (SRQ-E), including four regulation subscales to assess regulation styles (i.e., intrinsic motivation, identified regulation, introjected regulation and external regulation). Confirmatory factor analysis (CFA) was used to test the four subscales of SRQ-E (latent variables) with the data obtained using AMOS v.23 (Analysis of Moment Structures). Then, structural equation model (SEM) with maximum likelihood estimates was used to test the hypothesized model. Results: The results indicated that only intrinsic motivation, but not identified, introjected or external motivation, toward physical activity predicted both physical activity and sitting time. Higher intrinsic motivation toward physical activity was associated with both higher physical activity and lower sitting time. In addition, physical activity was a mediator for lower sitting time when the source was intrinsic motivation. Conclusion: Previous studies have shown low between and within participant correlation between sitting time and physical activity, and interventions have generally failed to both increase physical activity while decreasing sitting time. The present cross-sectional results suggest that targeting increased physical activity by increased intrinsic motivation has the potential to both increase physical activity and decrease sitting time.

Effect of night-time data on sedentary and upright time and energy expenditure measured with the Fibion accelerometer in Emirati women.

BACKGROUND AND AIMS: Wearing an accelerometer during night-time could conflate sedentary behavior time and sleep hours. It is important to assess the impact of including night-time data on sedentary and upright behavior in a sedentary population. Therefore, we investigated differences in sitting and upright time and associated energy expenditure (EE), recorded by a Fibion accelerometer, with and without night-time data in Emirati women working in desk-based jobs. METHODS: Thirty-one healthy Emirati women working in the government offices used the Fibion accelerometer for a week. Fibion data were included if the participants wore the device for ≥600 min per day for a minimum of three weekdays and one weekend day. Sedentary (sitting) and upright time and associated energy expenditure (EE) were recorded using the Fibion. Variables were compared with and without night-time data using the paired t tests or Wilcoxon signed-rank tests. Effect sizes were determined using Cohen's d. RESULTS: Statistically significant differences for 15 out of 18 variables were observed when the night-time data were included. Except for cycling time, cycling EE, and vigorous activity time, nearly all other outcome measures showed a significant increase (moderate to large effect sizes) with night-time data compared to those without night-time data. CONCLUSIONS: Cycling time/EE and vigorous activity time did not change with standard night-time data. Therefore, studies examining only cycling and/or vigorous activity time with the Fibion accelerometer do not require night-time data removal. An analysis of other variables relating to sedentary and upright time will require night-time data exclusion.

Delineating the geographic context of physical activities: A systematic search and scoping review of the methodological approaches used in social ecological research over two decades.

BACKGROUND: The social ecological approach suggests that the spatial context among other factors influence physical activity behavior. Ample research documents physical environmental effects on physical activity. Yet, to date inconsistent associations remain, which might be explained by conceptual and methodological challenges in measuring the spatial dimensions of health behavior. We review methods applied to measure the spatial contexts in the social ecological physical activity literature. METHODS: Online databases and selected reviews were used to identify papers published between 1990 and 2020. A total of 2167 records were retrieved, from which 412 studies that used physical activity as a primary outcome variable, included measures of the physical environment and applied the main principles of the social ecological approach, were included. RESULTS: Subjective approaches were the dominant method to capture the spatial context of physical activities. These approaches were applied in 67% (n=279) of the studies. From the objective approaches an administrative unit was most prevalent and was applied in 29% (n=118) of the studies. The most comprehensive objective spatial methods that capture the true environmental exposure, were used only in 2% (n=10) of the studies. CONCLUSIONS: Current social ecological physical activity research applies simple conceptualizations and methods of the spatial context. While conceptual and methodological concerns have been repeatedly expressed, no substantive progress has been made in the use of spatial approaches. To further our understanding on place effects on health, future studies should carefully consider the choice of spatial approaches, and their effect on study results.

Staying Active under Restrictions: Changes in Type of Physical Exercise during the Initial COVID-19 Lockdown.

The COVID-19 pandemic and the associated governmental restrictions suddenly changed everyday life and potentially affected exercise behavior. The aim of this study was to explore whether individuals changed their preference for certain types of physical exercise during the pandemic and to identify risk factors for inactivity. An international online survey with 13,881 adult participants from 18 countries/regions was conducted during the initial COVID-19 related lockdown (between April and May 2020). Data on types of exercise performed during and before the initial COVID-19 lockdown were collected, translated, and categorized (free-text input). Sankey charts were used to investigate these changes, and a mixed-effects logistic regression model was used to analyze risks for inactivity. Many participants managed to continue exercising but switched from playing games (e.g., football, tennis) to running, for example. In our sample, the most popular exercise types during the initial COVID-19 lockdown included endurance, muscular strength, and multimodal exercise. Regarding risk factors, higher education, living in rural areas, and physical activity before the COVID-19 lockdown reduced the risk for inactivity during the lockdown. In this relatively active multinational sample of adults, most participants were able to continue their preferred type of exercise despite restrictions, or changed to endurance type activities. Very few became physically inactive. It seems people can adapt quickly and that the constraints imposed by social distancing may even turn into an opportunity to start exercising for some. These findings may be helpful to identify individuals at risk and optimize interventions following a major context change that can disrupt the exercise routine.

Comparison of Classroom-Based Sedentary Time and Physical Activity in Conventional Classrooms and Open Learning Spaces Among Elementary School Students.

European children and adolescents spend most of their daily life and especially their school hours being sedentary which may increase their risk for chronic non-communicable diseases later in life. After the curriculum reform of Finnish basic education in 2014, most of the new or renovated comprehensive schools in Finland incorporate open and flexible classroom designs. Their open learning spaces may provide students opportunities to reduce sedentary behavior during school hours. Thus, waist-worn accelerometers were used to assess classroom-based sedentary time (ST), the number of breaks from sedentary time (BST), and physical activity (PA) among cross-sectional samples of 3rd and 5th grade students during two separate academic years in a school that underwent a renovation from conventional classrooms to open learning spaces. The cohort of 5th grade students before renovation had a smaller proportion of ST from total classroom time (56.97 ± 12.24%, n = 42 vs. 67.68 ± 5.61%, n = 28, mean difference = 10.71%-points, 95%CI = -15.65 to-5.77, p < 0.001), a greater number of BST per 60 min of classroom time (7.41 ± 1.16 breaks/h vs. 9.19 ± 1.59 breaks/h, mean difference = -1.78 breaks/h, 95%CI = -2.486 to -1.079, p < 0.001) and a greater proportion of light intensity PA (28.66 ± 9.99% vs. 22.56 ± 4.59%, mean difference = 6.10%, 95%CI = 2.56 to 9.64, p = 0.001) than the 5th grade cohort assessed after renovation. The cohort of 3rd grade student had a greater proportion of moderate-to-vigorous intensity PA (MVPA) after the renovation compared to the cohort assessed before the renovation [Mean Rank (Before) = 27.22, Mean Rank (After) = 37.58, U =524.0, p = 0.033]. Despite the greater ST found in 5th graders, schools with open learning spaces may facilitate BST or MVPA as observed in the 5th and 3rd grade cohorts in open learning spaces compared to the cohorts in conventional classrooms, respectively. Future studies should seek to investigate and develop teacher practices to capitalize the potential of open classrooms to reduce ST, since classroom renovation alone may not be a sufficient intervention as of itself. Longitudinal studies utilizing randomized controlled trials are warranted.

Does breaking up prolonged sitting improve cognitive functions in sedentary adults? A mapping review and hypothesis formulation on the potential physiological mechanisms.

BACKGROUND: Prolonged (excessive) sitting is detrimentally associated with cardiovascular, metabolic and mental health. Moreover, prolonged sitting has been associated with poor executive function, memory, attention and visuospatial skills, which are important cognitive aspects of work performance. Breaking up prolonged sitting with standing or light-intensity exercises at the workplace is recognized as a potential measure in improving cognition. However, preliminary evidence, primarily from acute laboratory experiments, has enabled formulating hypothesis on the possible mechanistic pathways. Hence, the aim of this mapping review is to gather preliminary evidence and substantiate possible physiological mechanisms underpinning the putative effects of breaking prolonged sitting on improving cognitive function among sedentary office workers. MAPPING METHOD: We searched four databases to identify relevant studies that explored the effects of uninterrupted sitting on cognitive function. First, we introduce how prolonged sitting increases the risks of hyperglycemia, autonomic stability, inflammation, adverse hormonal changes and restrictions in cerebral blood flow (CBF) and alters cognitive function. Second, we elucidate the direct and indirect effects of breaking up prolonged sitting time that may prevent a decline in cognitive performance by influencing glycaemic variability, autonomic stability, hormones (brain derived neurotrophic factor, dopamine, serotonin), vascular functions, and CBF. We highlight the importance of breaking up prolonged sitting on metabolic, vascular and endocrine functions, which in turn may improve cognitive functions and eventually foster work productivity. Improved synaptic transmission or neuroplasticity due to increased brain glucose and mitochondrial metabolism, increased endothelial shear and CBF, increased brain neurotrophic factors (dopamine) and accelerated anti-inflammatory functions are some of the hypothetical mechanisms underpinning improved cognitive functions. CONCLUSION: We postulate that improving cognitive function by breaking up prolonged sitting periods is biologically plausible with the myriad of (suggested) physiological mechanisms. Future experimental studies to ascertain the aforementioned hypothetical mechanisms and clinical trials to break sedentary behavior and improve cognitive functions in sedentary office workers are warranted.

Continuity and Discontinuity of Sport and Exercise Type During the COVID-19 Pandemic. An Exploratory Study of Effects on Mood.

Involvement in sport and exercise not only provides participants with health benefits but can be an important aspect of living a meaningful life. The COVID-19 pandemic and the temporary cessation of public life in March/April/May 2020 came with restrictions, which probably also made it difficult, if not impossible, to participate in certain types of sport or exercise. Following the philosophical position that different types of sport and exercise offer different ways of "relating to the world," this study explored (dis)continuity in the type of sport and exercise people practiced during the pandemic-related lockdown, and possible effects on mood. Data from a survey of 601 adult exercisers, collected shortly after the COVID-19 outbreak in Finland, were analyzed. Approximately one third (35%) of the participants changed their "worldmaking" and shifted to "I-Nature"-type activities. We observed worse mood during the pandemic in those who shifted from "I-Me," compared to those who had preferred the "I-Nature" relation already before the pandemic and thus experienced continuity. The clouded mood of those experiencing discontinuity may be the result of a temporary loss of "feeling at home" in their new exercise life-world. However, further empirical investigation must follow, because the observed effect sizes were small.

Can the Functional Movement Screen Method Identify Previously Injured Wushu Athletes?

The functional movement screen (FMS) is commonly used to evaluate sports injury risks, but no study has been reported for Wushu athletes. The aim of this study was to identify optimal FMS cut-off points for previously injured Wushu athletes and to examine the associations with other possible factors. In this study, a total of 84 Chinese Wushu athletes (15.1 ± 4.5 years old, 51% male) with a minimum of two years of professional training background in either Taiji, Changquan, or Nanquan were assessed by the FMS. Video recordings were used to confirm the scoring criteria, and previous injuries were assessed based on face-to-face interviews. An optimal cut-off of the FMS score was investigated by receiver operating characteristic curves with sensitivity and specificity. We found that FMS score of less than 16 (sensitivity = 80%, specificity = 56%) was related to an increased occurrence of injuries (odds ratio = 5.096, 95%CI: 1.679-15.465) for the current study sample. The training type and training levels were related with FMS scores. More than half of the athletes (58%) had FMS asymmetry and 21% of athletes reported pain while performing the FMS protocol. Future prospective studies are recommended to use FMS with cut-off of 16 points in Wushu athletes.

Allometrically scaled explosive strength, but not static strength or maximal oxygen uptake is associated with better central processing time in young males.

BACKGROUND: We aimed to examine the associations of cardiorespiratory fitness (CRF), static strength and explosive strength with cognitive functions in young males. METHODS: Eighty-six young males (age 16-24 years) participated in the study and took part in a number of tests including: static strength (grip strength test), explosive strength (Sargent jump test), and CRF (via direct measure of maximal oxygen uptake [VO2max]). Static strength and explosive strength were scaled by allometrically modeled skeletal muscle mass (SMM) and height while VO2max was scaled by SMM and body mass (BM). Cognition was assessed by inhibitory control, simple and choice reaction time tasks using computerized Cambridge Neuropsychological Test Battery (CANTAB). Central processing time was measured by surface electromyography changes in isometric contraction response to an audio stimulus. RESULTS: VO2max scaled by BM (but not SMM), was associated with better central processing time and stop-signal reaction time (SSRT). Explosive strength was also associated with better central processing time independent of VO2max. However, static strength was not associated with cognition. CONCLUSIONS: The results suggest that explosive strength is a better predictor of central processing than static strength or VO2max in young males. Longitudinal studies are needed to examine whether explosive strength training in youth would improve central processing time.

Does free public transit increase physical activity and independent mobility in children? Study protocol for comparing children's activity between two Finnish towns with and without free public transit.

BACKGROUND: Children's habitual physical activity, including active travel and catching public transit (walking and cycling to and from destinations), and independent mobility (mobility without an adult) have decreased. Public transit trips are physically active and can provide access to hobbies independent of parents, but there is no device-measured data about children's total physical activity time following the introduction of free public transit. Our aim is to compare physical activity and independent mobility between children living in two Finnish towns, one with a recently introduced free public transit system, and the other without free public transit. METHODS: The city of Mikkeli has provided free public transit for all comprehensive school children since 2017. Various districts from Mikkeli, and the reference town of Kouvola (towns from South-Eastern Finland with a comparative population size and geographical structure), are selected based on their accessibility and the availability of public transit services. Samples of 10-12-year-old children will be recruited through primary schools. We will compare moderate-to-vigorous physical activity time, sitting time (a thigh-worn Fibion® device) and independent mobility (a participatory mapping method, PPGIS) of children: 1) who live in towns with and without free public transit, 2) who live and go to school in districts with high vs. low perceived and objective access to free public transit, and 3) who report using vs. not using free public transit. In addition, ethnography will be used to get insights on the social and cultural effects of the free public transit on children's and parent's everyday life. DISCUSSION: There is a need for scalable solutions that can increase children's physical activity independent of their socioeconomic background or place of residence. This project will give information on how a political action to provide free public transit for children is associated with their total physical activity time and independent mobility patterns, therefore providing highly relevant information for political decision-making and for promoting independent physical activity in children.

Training-Induced Acute Neuromuscular Responses to Military Specific Test during a Six-Month Military Operation.

Limited data are available regarding strength and endurance training adaptations to occupational physical performance during deployment. This study assessed acute training-induced changes in neuromuscular (electromyography; EMG) and metabolic (blood lactate, BLa) responses during a high-intensity military simulation test (MST), performed in the beginning (PRE) and at the end (POST) of a six-month crisis-management operation. MST time shortened (145 ± 21 vs. 129 ± 16 s, -10 ± 7%, p < 0.001) during the operation. Normalized muscle activity increased from PRE to POST in the hamstring muscles by 87 ± 146% (116 ± 52 vs. 195 ± 139%EMGMVC, p < 0.001) and in the quadriceps by 54 ± 81% (26 ± 8 vs. 40 ± 20%EMGMVC, p < 0.001). In addition, higher acute BLa values were measured after MST during POST. Changes in BLa and EMG suggested an increased neural input and metabolic rate during POST MST, likely leading to faster performance times at the end of the operation. High EMG values throughout the different phases of MST suggested that despite the anaerobic nature of the test, the soldiers were able to maintain their voluntary muscle activation level until the end of the test. This indicates only limited neural fatigue during the two-minute high-intensity military specific performance. While learning effect may explain some part of the improvement in the MST performance times, combined strength and endurance training three times per week may improve neuromuscular performance in occupationally relevant tasks.

Sedentary Thresholds for Accelerometry-Based Mean Amplitude Deviation and Electromyography Amplitude in 7-11 Years Old Children.

We investigated the ability of energy expenditure, movement sensing, and muscle activity to discriminate sedentary and non-sedentary activities in children. Thirty-five 7-11-year-old children participated in the study. Simultaneous assessment of oxygen uptake (V̇O2), triaxial accelerometry, and thigh muscle electromyography (EMG) were performed during eight different sedentary and non-sedentary activities including lying down, sitting-, standing-, and walking-related activities, which were performed in a random order. Mean values of V̇O2, accelerometry, and EMG from the concurrent 2 min epochs during each activity were computed. Resting energy expenditure (REE) was measured during 30 min supine rest. Directly measured metabolic equivalent of tasks (METs, V̇O2 in activities/V̇O2 in REE) were calculated for each activity. Mean amplitude deviation (MAD) was computed for accelerometry. EMG was normalized for mean muscle activity during self-paced walking. The classification accuracy of METs, MAD, and EMG to discriminate sedentary activities from physical activities was investigated by receiver operating characteristic curves and optimal cut-offs based on maximal sensitivity and specificity. Mean (SD) REE was 5.0 ± 0.8 ml/kg/min. MET, MAD, and EMG values ranged from 1.0 to 4.9, 0.0020 to 0.4146 g, and 4.3 to 133.9% during lying down and walking at 6 km/h, respectively. Optimal cut-offs to discriminate sedentary activities from non-sedentary activities were 1.3 for METs (sensitivity = 82%, specificity = 88%), 0.0033 g for MAD (sensitivity = 80%, specificity = 91%), and 11.9% for EMG (sensitivity = 79%, specificity = 92%). In conclusion, this study provides applicable thresholds to differentiate sitting and standing and sedentary and non-sedentary activities based on METs, MAD, and EMG in young children.