Elevated heart rate and decreased muscle endothelial nitric oxide synthase in early development of insulin resistance.

Insulin resistance (IR) is a risk factor for the development of several major metabolic diseases. Muscle fiber composition is established early in life and is associated with insulin sensitivity. Hence, muscle fiber composition was used to identify early defects in the development of IR in healthy young individuals in the absence of clinical manifestations. Biopsies were obtained from the thigh muscle, followed by an intravenous glucose tolerance test. Indices of insulin action were calculated and cardiovascular measurements, analyses of blood and muscle were performed. Whole body insulin sensitivity (SIgalvin) was positively related to expression of type I muscle fibers (r = 0.49; P < 0.001) and negatively related to resting heart rate (HR, r = -0.39; P < 0.001), which was also negatively related to expression of type I muscle fibers (r = -0.41; P < 0.001). Muscle protein expression of endothelial nitric oxide synthase (eNOS), whose activation results in vasodilation, was measured in two subsets of subjects expressing a high percentage of type I fibers (59 ± 6%; HR = 57 ± 9 beats/min; SIgalvin = 1.8 ± 0.7 units) or low percentage of type I fibers (30 ± 6%; HR = 71 ± 11; SIgalvin = 0.8 ± 0.3 units; P < 0.001 for all variables vs. first group). eNOS expression was 1) higher in subjects with high type I expression; 2) almost twofold higher in pools of type I versus II fibers; 3) only detected in capillaries surrounding muscle fibers; and 4) linearly associated with SIgalvin. These data demonstrate that an altered function of the autonomic nervous system and a compromised capacity for vasodilation in the microvasculature occur early in the development of IR.NEW & NOTEWORTHY Insulin resistance (IR) is a risk factor for the development of several metabolic diseases. In healthy young individuals, an elevated heart rate (HR) correlates with low insulin sensitivity and high expression of type II skeletal muscle fibers, which express low levels of endothelial nitric oxide synthase (eNOS) and, hence, a limited capacity to induce vasodilation in response to insulin. Early targeting of the autonomic nervous system and microvasculature may attenuate development of diseases stemming from insulin resistance.

Improving movement behavior in office workers: effects of two multi-level cluster-RCT interventions on mental health.

BACKGROUND: We have previously reported on the design and efficacy of two cluster-randomized multi-level workplace interventions, attempting to decrease sedentary behavior (SED) or increase moderate to vigorous physical activity (MVPA) among office workers to improve mental health outcomes. The aim of this study was to investigate intervention effects on mental health outcomes, i.e., mental wellbeing, depression or anxiety symptoms, and stress immediately after the 6-month intervention period. METHODS: Teams of 263 office workers were cluster-randomized to one of two interventions or a waitlist control group. The PA intervention (iPA) focused on increasing MVPA and the SED intervention (iSED) on reducing SED. Both multi-level interventions targeted individual office workers and their social, physical, and organizational work environment, incorporating counseling based on cognitive behavioral therapy and motivational interviewing. Mental health outcomes were assessed using validated questionnaires before and immediately after the intervention. Intervention effects were analyzed using linear mixed effects models. RESULTS: Participants were mostly female and highly educated, with a mean age of 42 years and had favorable levels of mental health at baseline. Mental wellbeing improved for the iSED group (ß = 8, 95% CI 1 to 15, p = 0.030) but not for the iPA group (ß = 6, 95% CI -1 to 12, p = 0.072) compared to the control group. No effects were found for depression or anxiety symptoms or stress. CONCLUSIONS: The multi-level interventions improved mental wellbeing among this population of office workers, reaching statistical significance in the iSED group. The size of the effect can be regarded meaningful, considering favorable mental health and high PA level at baseline. Thus, workplace interventions that provide support on multiple levels appear to have potential for improving mental wellbeing, but not reducing ill-health variables, among healthy office workers. More research is needed to understand the mechanisms through which such improvements can be achieved and to identify the most effective intervention components. TRIAL REGISTRATION: ISRCTN92968402 (27 February 2018).

Insulin resistance after a 3-day fast is associated with an increased capacity of skeletal muscle to oxidize lipids.

There is a debate on whether lipid-mediated insulin resistance derives from an increased or decreased capacity of muscle to oxidize fats. Here, we examine the involvement of muscle fiber composition in the metabolic responses to a 3-day fast (starvation, which results in increases in plasma lipids and insulin resistance) in two groups of healthy young subjects: 1), area occupied by type I fibers = 61.0 ± 11.8%; 2), type I area = 36.0 ± 4.9% (P < 0.001). Muscle biopsies and intravenous glucose tolerance tests were performed after an overnight fast and after starvation. Biopsies were analyzed for muscle fiber composition and mitochondrial respiration. Indices of glucose tolerance and insulin sensitivity were determined. Glucose tolerance was similar in both groups after an overnight fast and deteriorated to a similar degree in both groups after starvation. In contrast, whole body insulin sensitivity decreased markedly after starvation in group 1 (P < 0.01), whereas the decrease in group 2 was substantially smaller (P = 0.06). Nonesterified fatty acids and ß-hydroxybutyrate levels in plasma after an overnight fast were similar between groups and increased markedly and comparably in both groups after starvation, demonstrating similar degrees of lipid load. The capacity of permeabilized muscle fibers to oxidize lipids was significantly higher in group 1 versus 2, whereas there was no significant difference in pyruvate oxidation between groups. The data demonstrate that loss of whole body insulin sensitivity after short-term starvation is a function of muscle fiber composition and is associated with an elevated rather than a diminished capacity of muscle to oxidize lipids.NEW & NOTEWORTHY Whether lipid-mediated insulin resistance occurs as a result of an increased or decreased capacity of skeletal muscle to oxidize lipids has been debated. We show that a 3-day fast results in increases in circulating lipids and insulin resistance in subjects expressing a high or low proportion of type I muscle fibers. High expression of type I is associated with a higher capacity to oxidize lipids and a greater loss of insulin sensitivity after starvation.

Effects of prolonged sitting and physical activity breaks on measures of arterial stiffness and cortisol in adolescents.

AIM: In adults, prolonged periods of sitting have been linked to acute negative effects on vascular structure and function. The aim of this study was to evaluate the acute effects of physical activity (PA) breaks during prolonged sitting on arterial stiffness, cortisol and psychological factors in adolescents. METHODS: Adolescents underwent different short (3-min) breaks starting every 20 min, during 80 min of sitting on three separate days. Breaks were (A) social seated breaks (SOC), (B) low-intensity simple resistance activity PA breaks (SRA) and (C) moderate-intensity step-up PA breaks (STEP). The arterial stiffness measures were augmentation index (AIx), AIx@75 and pulse wave velocity (PWV). Cortisol was measured from saliva. Psychological factors were self-reported. RESULTS: Eleven girls and six boys (average age 13.6 ± 0.7 years) participated, with average baseline heart rates of 72 ± 11 bpm, systolic/diastolic blood pressure 111 ± 7/64 ± 6 mmHg and cortisol 10.9 ± 5.8 nmoL/L. PWV, cortisol and psychological factors did not change after any of the conditions. AIx@75 increased significantly (4.9 ± 8.7-9.2 ± 13.2) after the STEP intervention compared with SOC and SRA (time × condition p < 0.05). CONCLUSION: Arterial stiffness increased after prolonged sitting with frequent, short step-up activity breaks. The results indicate potential important intensity-dependent effects of physical activity on vascular regulation in youth.

The effect of two multi-component behavior change interventions on cognitive functions.

BACKGROUND: We previously reported the effects of two cluster-randomized 6-month multi-component workplace interventions, targeting reducing sedentary behavior or increasing physical activity among office workers, on movement behaviors and cardiorespiratory fitness. The primary aim of this study was to investigate the effects of these interventions on cognitive functions compared to a wait-list control group. The secondary aims were to examine if changes in cognition were related to change in cardiorespiratory fitness or movement behaviors and if age, sex, or cardiorespiratory fitness moderated these associations. METHODS: Both interventions encompassed multi-components acting on the individual, environmental, and organizational levels and aimed to change physical activity patterns to improve mental health and cognitive function. Out of 263 included participants, 139 (mean age 43 years, 76% females) completed a neuropsychological test battery and wore accelerometers at baseline and 6-month follow-up. The intervention effect (aim 1) on cognitive composite scores (i.e., Executive Functions, Episodic Memory, Processing Speed, and Global Cognition) was investigated. Additionally, associations between changes in movement behaviors and cardiorespiratory fitness, and changes in cognition were examined (aim 2). Moreover, age, sex, and cardiorespiratory fitness level were investigated as possible moderators of change associations (aim 3). RESULTS: Overall, cognitive performance improved from baseline to follow-up, but the change did not differ between the intervention groups and the control group. Changes in cardiorespiratory fitness or any movement behavior category did not predict changes in cognitive functions. The association between changes in time in bed and changes in both Executive Function and Global Cognition were moderated by age, such that a more positive relation was seen with increasing age. A less positive association was seen between changes in sedentary behavior and Processing Speed for men vs. women, whereas higher cardiorespiratory fitness was related to a more positive association between changes in moderate-intensity physical activity and Global Cognition. CONCLUSION: The lack of an intervention effect on cognitive functions was expected since the intervention did not change movement behavior or fitness. Age, sex, and cardiorespiratory fitness level might moderate the relationships between movement behaviors and cognitive functions changes. TRIAL REGISTRATION: ISRCTN92968402 . Registered 09/04/2018.

Immediate effects of a single session of physical exercise on cognition and cerebral blood flow: A randomized controlled study of older adults.

BACKGROUND: Regular physical activity is beneficial for cognitive performance in older age. A single bout of aerobic physical exercise can transiently improve cognitive performance. Researchers have advanced improvements in cerebral circulation as a mediator of long-term effects of aerobic physical exercise on cognition, but the immediate effects of exercise on cognition and cerebral perfusion are not well characterized and the effects in older adults are largely unknown. METHODS: Forty-nine older adults were randomized to a 30-min aerobic exercise at moderate intensity or relaxation. Groups were matched on age and cardiovascular fitness (VO2 max). Average Grey Matter Blood Flow (GMBF), measured by a pulsed arterial-spin labeling (pASL) magnetic resonance imaging (MRI) acquisition, and working memory performance, measured by figurative n-back tasks with increasing loads were assessed before and 7 min after exercising/resting. RESULTS: Accuracy on the n-back task increased from before to after exercising/resting regardless of the type of activity. GMBF decreased after exercise, relative to the control (resting) group. In the exercise group, higher n-back performance after exercise was associated with lower GMBF in the right hippocampus, left medial frontal cortex and right orbitofrontal cortex, and higher cardiovascular fitness was associated with lower GMBF. CONCLUSION: The decrease of GMBF reported in younger adults shortly after exercise also occurs in older adults and relates to cardiovascular fitness, potentially supporting the link between cardiovascular fitness and cerebrovascular reactivity in older age.

Inattention and hyperactivity symptoms in childhood predict physical activity in adolescence.

BACKGROUND: Physical activity has been documented to influence several aspects of physical and mental health. Growing evidence shows that physical activity can improve attention. Less is known about how symptoms of inattention and hyperactivity / impulsivity in childhood are associated with physical activity in adolescence. We aimed to explore this relationship further. METHODS: We used a cohort of 3949 Swedish children (1884 boys and 2065 girls) with data collected at ages 9 (or 12) and 15. We investigated the influence of symptoms of inattention and hyperactivity / impulsivity in childhood - age 9/12 (inattention and hyperactivity/impulsivity separately) on self-rated physical activity at age 15, using multiple logistic regression models. We considered potential confounders such as sex, parental education level, physical activity in childhood and neurodevelopmental comorbidity. A cluster robust sandwich estimator was applied to adjust the standard errors for the nested twin data when computing the regression models. RESULTS: Symptoms of inattention in childhood (9/12) predicted less physical activity in adolescence (age 15) (OR = 0.83 CI = 0.78-0.89), whereas the opposite was true for hyperactivity/impulsivity (OR = 1.08 CI = 1.02-1.10). These associations still remained when taking possible confounders into account including neurodevelopmental and neurodevelopmental related comorbidity. CONCLUSIONS: These findings support the importance of helping children and adolescents with inattention symptoms to engage in physical activity in suitable settings.

The effects on self-efficacy, motivation and perceived barriers of an intervention targeting physical activity and sedentary behaviours in office workers: a cluster randomized control trial.

BACKGROUND: The importance of physical activity on health is clear, but changing behaviour is difficult. Successful interventions aiming to improve physical activity and reduce sedentary behaviour is therefore of importance. The aim of this study was to evaluate effects on motivation, self-efficacy and barriers to change behaviour from two different behavioural intervention focusing either on reducing sedentary behaviour or on increasing physical activity as compared to a waiting list control group. METHODS: The study was designed as a cluster randomized control trial (RCT) within two private companies. Self-efficacy, motivation and perceived barriers were together with demographic variables assessed before and after a 6-month intervention. Participant cluster teams were randomly allocated to either the physical activity intervention (iPA), the sedentary behaviour intervention (iSED), or control group. The intervention was multi componential and included motivational counselling based on Cognitive behaviour therapy and Motivational interviewing, group activities and management involvement. Group differences were determined using Bayesian multilevel modelling (parameter estimate; credible interval (CI)), analysing complete cases and those who adhered to the protocol by adhering to at least 3 out of 5 intervention sessions. RESULTS: After the intervention, the complete cases analysis showed that the iPA group had significantly higher autonomous motivation (0.33, CI: 0.05-0.61) and controlled motivation (0.27, CI: 0.04-0.51) for physical activity compared with the control group. The iSED group scored less autonomous and controlled motivation compared to the iPA group (0.38, CI: - 0.69- -0.087 respectively - 0.32, CI: - 0.57-0.07) but no significant differences compared with the control group. Among individuals that adhered to the protocol, the results showed higher scores on Exercise (3.03, CI: 0.28-6.02) and Sedentary self-efficacy (3.59, CI: 0.35-7.15) for individuals in the iPA group and on Sedentary self-efficacy (4.77, CI: 0.59-9.44) for the iSED group compared to the control group. CONCLUSION: These findings indicate that the interventions were successful in increasing self-efficacy in each intervention group and autonomous motivation for exercise in the iPA group, in particular when actively participating in the motivational counselling sessions.

Abdominal Muscle Activation During Common Modifications of the Trunk Curl-up Exercise.

ABSTRACT: Crommert, ME, Bjerkefors, A, Tarassova, O, and Ekblom, MM. Abdominal muscle activation during common modifications of the trunk curl-up exercise. J Strength Cond Res 35(2): 428-435, 2021-The purpose of this study was to investigate effects of common modifications of trunk curl-up exercise on the involvement of the abdominal muscles, particularly the deepest muscle layer, transversus abdominis (TrA). Ten healthy females performed 5 different variations of the trunk curl-up at a standardized speed, varying the exercise by assuming 3 different arm positions and applying left and right twist. Indwelling fine-wire electromyography (EMG) electrodes were used to record from TrA, obliquus internus (OI), obliquus externus (OE), and rectus abdominis (RA) unilaterally on the right side. Increasing the load by changing the arm position during a straight trunk curl-up increased the EMG of all abdominal muscles. Obliquus internus and TrA showed higher activation during right twist compared with left twist, whereas OE displayed the opposite pattern. Rectus abdominis did not show any change in activation level between twisting directions. The apparent load dependency on the activation level of all muscles, and the twisting direction dependency of all muscles except RA, are in keeping with the fiber orientation of the muscles. Notably, also TrA, with a less obvious mechanical role with regards to fiber orientation, increased activation with load during the straight trunk curl-up. However, the highest activation level of TrA during the trunk curl-up was only 40% of a maximum contraction; thus, it might not be the most suitable strength training exercise for this muscle.

The effectiveness of multi-component interventions targeting physical activity or sedentary behaviour amongst office workers: a three-arm cluster randomised controlled trial.

BACKGROUND: Interventions to increase physical activity or reduce sedentary behaviour within the workplace setting have shown mixed effects. This cluster randomised controlled trial assessed whether multi-component interventions, focusing on changes at the individual, environmental, and organisational levels, either increased physical activity or reduced sedentary behaviour, compared to a passive control group. METHODS: Teams of office-workers from two companies participated in one of two interventions (iPA: targeting physical activity; or iSED: targeting sedentary behaviour), or wait-list control group (C). Exclusion criterion was very high physical activity level (MVPA ≥30 min/day in ≥10 min bouts every day). Randomisation occurred at the level of workplace cluster, and groups were randomly allocated (1:1) with stratification for company and cluster size. Personnel involved in data collection and processing were blinded to group allocation. Both interventions included five sessions of cognitive behavioural therapy counselling for 6 months. iPA included counselling focused on physical activity, access to a gym, and encouragement to exercise, and go for lunch walks. iSED included counselling on sedentary behaviour and encouragement to reduce sitting and increase engagement in standing- and walking-meetings. At baseline and the 6-month mark accelerometers were worn on the hip and thigh for 7 days. The primary outcomes were group differences in time spent in moderate-to-vigorous intensity physical activity (%MVPA) and in sedentary behaviour (%), analysed using Bayesian multilevel modelling for those with complete data. RESULTS: Two-hundred and sixty three office workers (73% women, mean age 42 ± 9 years, education 15 ± 2 years) were randomised into 23 cluster teams (iPA n = 84, 8 clusters; iSED n = 87, 7 clusters; C n = 92, 7 clusters). No significant group differences (posterior mean ratios: 95% credible interval) were found after the intervention for %MVPA or for %Sedentary. %MVPA: iPA vs C (0·04: - 0·80-0·82); iSED vs C (0·47: - 0·41-1·32); iPA vs iSED (0·43: - 0·42-1·27). %Sedentary: iPA vs C (1·16: - 1·66-4·02); iSED vs C (- 0·44: - 3·50-2·64); iPA vs iSED (- 1·60: - 4·72-1·47). CONCLUSIONS: The multi-component interventions focusing on either physical activity or sedentary behaviour were unsuccessful at increasing device-measured physical activity or reducing sedentary behaviour compared to a control group. TRIAL REGISTRATION: ISRCTN, ISRCTN92968402 . Registered 27/2/2018, recruitment started 15/03/2018.

Criterion validity of the Ekblom-Bak and the Åstrand submaximal test in an elderly population.

PURPOSE: The aim of this study was to validate the submaximal Ekblom-Bak test (EB-test) and the Åstrand test (Å-test) for an elderly population. METHODS: Participants (n = 104), aged 65-75 years, completed a submaximal aerobic test on a cycle ergometer followed by an individually adjusted indirect calorimetry VO2max test on a treadmill. The HR from the submaximal test was used to estimate VO2max using both the EB-test and Å-test equations. RESULTS: The correlation between measured and estimated VO2max using the EB method and Å method in women was r = 0.64 and r = 0.58, respectively and in men r = 0.44 and r = 0.44, respectively. In women, the mean difference between estimated and measured VO2max was - 0.02 L min-1 (95% CI - 0.08 to 0.04) for the EB method and - 0.12 L min-1 (95% CI - 0.22 to - 0.02) for the Å method. Corresponding values for men were 0.05 L min-1 (95% CI - 0.04 to 0.14) and - 0.28 L min-1 (95% CI - 0.42 to - 0.14), respectively. However, the EB method was found to overestimate VO2max in men with low fitness and the Å method was found to underestimate VO2max in both women and men. For women, the coefficient of variance was 11.1%, when using the EB method and 19.8% when using the Å method. Corresponding values for men were 11.6% and 18.9%, respectively. CONCLUSION: The submaximal EB-test is valid for estimating VO2max in elderly women, but not in all elderly men. The Å-test is not valid for estimating VO2max in the elderly.

Effects of moderately increased testosterone concentration on physical performance in young women: a double blind, randomised, placebo controlled study.

OBJECTIVE: To investigate the effects of a moderate increase in serum testosterone on physical performance in young, physically active, healthy women. METHODS: A double blind, randomised, placebo controlled trial was conducted between May 2017 and June 2018 (ClinicalTrials.gov ID: NCT03210558). 48 healthy, physically active women aged 18-35 years were randomised to 10 weeks of treatment with 10 mg of testosterone cream daily or placebo (1:1). All participants completed the study. The primary outcome measure was aerobic performance measured by running time to exhaustion (TTE). Secondary outcomes were anaerobic performance (Wingate test) and muscle strength (squat jump (SJ), counter movement jump (CMJ) and knee extension peak torque). Hormone levels were analysed and body composition assessed by dual energy X-ray absorptiometry. RESULTS: Serum levels of testosterone increased from 0.9 (0.4) nmol/L to 4.3 (2.8) nmol/L in the testosterone supplemented group. TTE increased significantly by 21.17 s (8.5%) in the testosterone group compared with the placebo group (mean difference 15.5 s; P=0.045). Wingate average power, which increased by 15.2 W in the testosterone group compared with 3.2 W in the placebo group, was not significantly different between the groups (P=0.084). There were no significant changes in CMJ, SJ and knee extension. Mean change from baseline in total lean mass was 923 g for the testosterone group and 135 g for the placebo group (P=0.040). Mean change in lean mass in the lower limbs was 398 g and 91 g, respectively (P=0.041). CONCLUSION: The study supports a causal effect of testosterone in the increase in aerobic running time as well as lean mass in young, physically active women.

Post Activation Potentiation and Concentric Contraction Performance: Effects on Rate of Torque Development, Neuromuscular Efficiency, and Tensile Properties.

Gago, P, Zoellner, A, Cezar, J, and Ekblom, MM. Post activation potentiation and concentric contraction performance: effects on rate of torque development, neuromuscular efficiency and tensile properties. J Strength Cond Res 34(6): 1600-1608, 2020-This study investigated how a 6-second maximal voluntary isometric contraction (MVIC) conditioning affected plantar flexor twitch rate of torque development (RTDTW), as well as peak torque (PTCC) and rate of torque development (RTDCC) of maximal voluntary concentric contractions (MVCC) performed at 60°·s. RTDCC and normalized triceps surae electromyography signals (EMGTS) were measured during different phases of contraction. In addition, muscle tendon unit passive stiffness index (SI) calculated from the torque-angle relation was measured after each MVCC. Enhancements were found in the RTDTW immediately (by 59.7%) and up to 480 seconds (by 6.0%) after MVIC (p < 0.05). RTDCC during the 100-200 ms, 50-200 ms, and 0-200 ms phases and PTCC were enhanced (by 5.7-9.5%) from 90 to 300 seconds after conditioning (p < 0.05). Neuromuscular efficiency increased (decreased EMGTS/RTDCC) in the 50-200 ms and 0-200 ms phases by 8.8-12.4%, from 90 to 480 seconds after MVIC (p < 0.05). No significant changes were found in the SI or in RTDCC during the 50-100 ms phase, suggesting that the enhancements reported reflect mainly contractile rather than neural or tensile mechanisms. PAP effects on PTCC and RTDCC were significant and more durable at a lower velocity than previously reported. Enhancement in RTDCC and neuromuscular efficiency were found to be more prominent in later phases (>100 ms) of the MVCC. This suggests that enhanced contractile properties, attained through MVIC, benefit concentric contraction performance.

Investigating the effects of muscle contraction and conditioning stimulus intensity on short-interval intracortical inhibition.

A reduction in short-interval intracortical inhibition (SICI) has been shown to accompany acute or chronic resistance exercise; however, little is known about how SICI is modulated under different contraction intensities. Therefore, the purpose of this study was to assess the effect of muscle contraction and conditioning stimulus intensity on the modulation of SICI. Single- and paired-pulse transcranial magnetic stimulation was applied to the primary motor cortex (M1), and motor evoked potentials (MEPs) were recorded from the biceps brachii in 16 adults (10M/6F). A conditioning-test stimulus paradigm (3 ms inter-stimulus intervals) was delivered during 10%, 20%, 40% and 75% of maximal voluntary isometric contraction (MVIC). At each force level, conditioning stimulus intensities of 60%, 70% and 80% of active motor threshold (AMT) were tested. Single-pulse MEPs were expressed as a proportion of the maximal muscle compound action potential, while SICI was quantified as a ratio of the unconditioned MEP. MEP amplitude increased with force output, with the greatest increase at 75% of MVIC. A reduction in SICI was observed from 40% to 75% of MVIC, but not 10%-40% of MVIC. There was no significant interaction between conditioning stimulus intensity and force level. The conditioning stimulus intensity (60%, 70% or 80% of AMT) did not alter the modulation of SICI. SICI was reduced at 75% of MVIC compared with the lower force outputs, and the magnitude of SICI in individual participants at different force outputs was not related. The findings suggest that strong muscle contractions are accompanied by less inhibition, which may have implications for neuroplasticity in exercise interventions.

Criterion validity and test-retest reliability of SED-GIH, a single item question for assessment of daily sitting time.

BACKGROUND: Sedentary behaviour has been closely linked to metabolic and cardiovascular health and is therefore of importance in disease prevention. A user-friendly tool for assessment of sitting time is thus needed. Previous studies concluded that the present tools used to assess a number of sedentary behaviours are more likely to overestimate sitting than single-item questions which often underestimate sitting time, and that categorical answering options are recommended. In line with this, the single-item question with categorical answering options, SED-GIH, was developed. The aim of this study was to investigate the criterion validity of the SED-GIH question using activPAL3 micro as the criterion measure. The second aim was to evaluate the test-retest reliability of the SED-GIH questionnaire. METHOD: In the validity section of this study, 284 middle-aged adults answered a web questionnaire, which included SED-GIH, wore activPAL and filled in a diary log for one week. Spearman's rho assessed the relationship between the SED-GIH answers and the daily average sitting time as monitored by the activPAL (activPAL-SIT), a Weighted Kappa assessed the agreement, ANOVA assessed differences in activPAL-SIT between the SED-GIH answer categories, and a Chi2 compared the proportions of hazardous sitters between the different SED-GIH answer categories. In the reliability section, 95 elderly participants answered the SED-GIH question twice, with a mean interval of 5.2 days. The reliability was assessed with ICC and a weighted Kappa. RESULTS: The SED-GIH question correlated moderately with activPAL-SIT (rho = 0.31), with a poor agreement (weighted Kappa 0.12). In total, 40.8% underestimated and 22.2% overestimated their sitting time. The ANOVA showed significant differences in activPAL-SIT between the different SED-GIH answer categories (p < 0.001). The Chi2 showed a significant difference in proportion of individuals sitting more than 10 h per day within each SED-GIH answer category. ICC for the test-retest reliability of SED-GIH was excellent with ICC = 0.86, and the weighted Kappa showed an agreement of 0.77. CONCLUSIONS: The unanchored single item SED-GIH question showed excellent reliability but poor validity in the investigated populations. Validity and reliability of SED-GIH is in line with other questionnaires that are commonly used when assessing sitting time.

Improving office workers' mental health and cognition: a 3-arm cluster randomized controlled trial targeting physical activity and sedentary behavior in multi-component interventions.

BACKGROUND: Physically inactive and sedentary lifestyles are negatively related to both mental health and cognition. For office-workers, who spend two-thirds of their workday sitting, it is important to improve these lifestyles. The aim of this study is to assess the effectiveness of multi-component interventions, incorporating individual, environmental and organizational changes, to increase physical activity or reduce sedentary behavior among office-workers in order to improve mental health and cognition. METHODS: a 3-arm, clustered randomized controlled trial (RCT) with waiting list control group amongst adult office-workers of two large Swedish companies. Cluster teams will be randomized into 6-month interventions or to a passive waiting list control group which will receive the allocated intervention with a 6-month delay. Two multicomponent interventions will be studied of which one focuses on improving physical activity and the other on reducing sedentary behavior. Both interventions include 5 sessions of motivational counselling. In the physical activity intervention persons also get access to a gym and team leaders will organize lunch walks and encourage to exercise. In the sedentary behavior intervention standing- and walking meetings will be implemented and team leaders will encourage to reduce sitting. The recruitment target is 110 office-workers per arm (330 in total). Measurements will be repeated every 6 months for a total intended duration of 24 months. Proximal main outcomes are physical activity measured with accelerometers and sedentary behavior with inclinometers. Distal outcomes are self-reported mental health and a cognition test battery. Additional outcomes will include cardiovascular fitness, body composition, sleep, self-reported physical activity and sedentary behavior, other health habits, physical health, and working mechanisms from blood samples and questionnaires. DISCUSSION: This cluster RCT will contribute to the currently available evidence by comparing the effectiveness of multi-component interventions targeting physical activity or sedentary behavior with the end goal of improving mental health and cognition. This study is strong in its cluster randomized design, numerous objective outcome measures and long-term follow-up. The exact content of the interventions has been defined by combining theory with results from a larger research project as well as having a continuous dialogue with the involved companies. TRIAL REGISTRATION: ISRCTN92968402 .

Do unfavourable alcohol, smoking, nutrition and physical activity predict sustained leisure time sedentary behaviour? A population-based cohort study.

Comparing lifestyle of people remaining sedentary during longer periods of their life with those favourably changing their behaviour can provide cues to optimize interventions targeting sedentary behaviour. The objective of this study was to determine lifestyle predictors of sustained leisure time sedentary behaviour and assess whether these predictors were dependent on gender, age, socioeconomic position and occupational sedentary behaviour. Data from a large longitudinal population-based cohort of adults (aged 18-97years) in Stockholm responding to public health surveys in 2010 and 2014 were analysed (n=49,133). Leisure time sedentary behaviour was defined as >3h per day of leisure sitting time e.g. watching TV, reading or using tablet. Individuals classified as sedentary at baseline (n=9562) were subsequently categorized as remaining sedentary (n=6357) or reduced sedentary behaviour (n=3205) at follow-up. Lifestyle predictors were unfavourable alcohol consumption, smoking, nutrition, and physical activity. Odds ratios (OR) and corresponding 95% Confidence Intervals (CI) were calculated, adjusting for potential confounders. Unfavourable alcohol consumption (OR=1.22, CI:1.11-1.34), unfavourable candy- or cake consumption (OR=1.15, CI:1.05-1.25), and unfavourable physical activity in different contexts were found to predict sustained sedentary behaviour, with negligible differences according to gender, age, socioeconomic position and occupational sedentary behaviour. People with unfavourable lifestyle profiles regarding alcohol, sweets, or physical activity are more likely to remain sedentary compared to sedentary persons with healthier lifestyle. The impact of combining interventions to reduce leisure time sedentary behaviour with reducing alcohol drinking, sweet consumption and increasing physical activity should be tested as a promising strategy for behavioural modification.

Post activation potentiation can be induced without impairing tendon stiffness.

PURPOSE: This study aimed to investigate conditioning effects from a single 6-s plantar flexion maximal voluntary isometric contraction (MVIC) on Achilles tendon stiffness (ATS) and twitch properties of the triceps surae in athletes. METHODS: Peak twitch (PT), rate of torque development (RTD), rising time (RT10₋90%) and half relaxation time (HRT) were measured from supramaximal twitches evoked in the plantar flexors of 10 highly trained athletes. Twitches were evoked before and at seven occasions during 10 min of recovery after a 6-s MVIC. In a second session, but at identical post-conditioning time points, ATS was measured at 30 and 50% of MVIC (ATS30% and ATS50%) using an ultrasonography-based method. RESULTS: The magnitude and duration of the conditioning MVIC on muscle contractile properties were in accordance with previous literature on post activation potentiation (PAP), i.e., high potentiation immediately after MVIC, with significant PAP for up to 3 min after the MVIC. While PT and RTD were significantly enhanced (by 60.6 ± 19.3 and 90.1 ± 22.5%, respectively) and RT10₋90% and HRT were reduced (by 10.1 ± 7.7 and 18.7 ± 5.6%, respectively) after conditioning, ATS remained unaffected. CONCLUSIONS: Previous studies have suggested that changes in stiffness after conditioning may interfere with the enhancements in twitch contractile properties. The present study, however, provided some evidence that twitch enhancements after a standard PAP can be induced without changes in ATS. This result may suggest that athletes can use this protocol to enhance muscle contractile properties without performance deficits due to changes in ATS.

Pro-Brain-Derived Neurotrophic Factor (BDNF), but Not Mature BDNF, Is Expressed in Human Skeletal Muscle: Implications for Exercise-Induced Neuroplasticity.

Exercise promotes brain plasticity partly by stimulating increases in mature brain-derived neurotrophic factor (mBDNF), but the role of the pro-BDNF isoform in the regulation of BDNF metabolism in humans is unknown. We quantified the expression of pro-BDNF and mBDNF in human skeletal muscle and plasma at rest, after acute exercise (+/- lactate infusion), and after fasting. Pro-BDNF and mBDNF were analyzed with immunoblotting, enzyme-linked immunosorbent assay, immunohistochemistry, and quantitative polymerase chain reaction. Pro-BDNF was consistently and clearly detected in skeletal muscle (40-250 pg mg-1 dry muscle), whereas mBDNF was not. All methods showed a 4-fold greater pro-BDNF expression in type I muscle fibers compared to type II fibers. Exercise resulted in elevated plasma levels of mBDNF (55%) and pro-BDNF (20%), as well as muscle levels of pro-BDNF (∼10%, all P < 0.05). Lactate infusion during exercise induced a significantly greater increase in plasma mBDNF (115%, P < 0.05) compared to control (saline infusion), with no effect on pro-BDNF levels in plasma or muscle. A 3-day fast resulted in a small increase in plasma pro-BDNF (∼10%, P < 0.05), with no effect on mBDNF. Pro-BDNF is highly expressed in human skeletal muscle, particularly in type I fibers, and is increased after exercise. While exercising with higher lactate augmented levels of plasma mBDNF, exercise-mediated increases in circulating mBDNF likely derive partly from release and cleavage of pro-BDNF from skeletal muscle, and partly from neural and other tissues. These findings have implications for preclinical and clinical work related to a wide range of neurological disorders such as Alzheimer's, clinical depression, and amyotrophic lateral sclerosis.

The role of acute changes in mBDNF, cortisol and pro-BDNF in predicting cognitive performance in old age.

The interplay between biomarkers of relevance to neuroplasticity and its association with learning and cognitive ability in old age remains poorly understood. The present study investigated acute changes in plasma concentrations of mature brain-derived neurotrophic factor (mBDNF), its precursor protein (pro-BDNF), and cortisol, in response to acute physical exercise and cognitive training interventions, their covariation and role in predicting cognitive performance. Confirmatory results provided no support for mBDNF, pro-BDNF and cortisol co-varying over time, as the acute interventions unfolded, but did confirm a positive association between mBDNF and pro-BDNF at rest. The confirmatory results did not support the hypothesis that mBDNF change following physical exercise were counteracted by temporally coupled changes in cortisol or pro-BDNF, or by cortisol at rest, in its previously demonstrated faciliatory effect on cognitive training outcome. Exploratory results instead provided indications of a general and trait-like cognitive benefit of exhibiting greater mBDNF responsiveness to acute interventions when coupled with lesser cortisol responsiveness, greater pro-BDNF responsiveness, and lower cortisol at rest. As such, the results call for future work to test whether certain biomarker profiles are associated with preserved cognition in old age.