Aims/hypothesis: We hypothesised that the insulin-sensitising effect of physical activity depends on the timing of the activity. Here, we examined cross-sectional associations of breaks in sedentary time and timing of physical activity with liver fat content and insulin resistance in a Dutch cohort. Methods: In 775 participants of the Netherlands Epidemiology of Obesity (NEO) study, we assessed sedentary time, breaks in sedentary time and different intensities of physical activity using activity sensors, and liver fat content by magnetic resonance spectroscopy (n=256). Participants were categorised as being most active in the morning (06:00–12:00 hours), afternoon (12:00–18:00 hours) or evening (18:00–00:00 hours) or as engaging in moderate-to-vigorous-physical activity (MVPA) evenly distributed throughout the day. Most active in a certain time block was defined as spending the majority (%) of total daily MVPA in that block. We examined associations between sedentary time, breaks and timing of MVPA with liver fat content and HOMA-IR using linear regression analyses, adjusted for demographic and lifestyle factors including total body fat. Associations of timing of MVPA were additionally adjusted for total MVPA. Results: The participants (42% men) had a mean (SD) age of 56 (4) years and a mean (SD) BMI of 26.2 (4.1) kg/m². Total sedentary time was not associated with liver fat content or insulin resistance, whereas the amount of breaks in sedentary time was associated with higher liver fat content. Total MVPA (−5%/h [95% CI −10%/h, 0%/h]) and timing of MVPA were associated with reduced insulin resistance but not with liver fat content. Compared with participants who had an even distribution of MVPA throughout the day, insulin resistance was similar (−3% [95% CI −25%, 16%]) in those most active in morning, whereas it was reduced in participants who were most active in the afternoon (−18% [95% CI −33%, −2%]) or evening (−25% [95% CI −49%, −4%]). Conclusions/interpretation: The number of daily breaks in sedentary time was not associated with lower liver fat content or reduced insulin resistance. Moderate-to-vigorous activity in the afternoon or evening was associated with a reduction of up to 25% in insulin resistance. Further studies should assess whether timing of physical activity is also important for the occurrence of type 2 diabetes. Graphical

Aims/hypotheses Our aim was to examine the independent and combined (cross-sectional) associations of sedentary time (ST), higher intensity physical activity (HPA) and cardiorespiratory fitness (CRF) with metabolic syndrome and diabetes status. Methods In 1933 adults (aged 40–75 years) ST and HPA (surrogate measure for moderate to vigorous physical activity) were measured with the activPAL3. CRF was assessed by submaximal cycle–ergometer testing. Metabolic syndrome was defined according to the Adult Treatment Panel (ATP) III guidelines. Diabetes status (normal, prediabetes [i.e. impaired glucose tolerance and/or impaired fasting glucose] or type 2 diabetes) was determined from OGTT. (Multinomial) logistic regression analyses were used to calculate likelihood for the metabolic syndrome, prediabetes and type 2 diabetes according to ST, HPA and CRF separately and combinations of ST–CRF and HPA–CRF. Results Higher ST, lower HPA and lower CRF were associated with greater odds for the metabolic syndrome and type 2 diabetes independently of each other. Compared with individuals with high CRF and high HPA (CRF_high–HPA_high), odds for the metabolic syndrome and type 2 diabetes were higher in groups with a lower CRF regardless of HPA. Individuals with low CRF and low HPA (CRF_low–HPA_low) had a particularly high odds for the metabolic syndrome (OR 5.73 [95% CI 3.84, 8.56]) and type 2 diabetes (OR 6.42 [95% CI 3.95, 10.45]). Similarly, compared with those with high CRF and low ST (CRF_high–ST_low), those with medium or low CRF had higher odds for the metabolic syndrome, prediabetes and type 2 diabetes, irrespective of ST. In those with high CRF, high ST was associated with significantly high odds for the metabolic syndrome (OR 2.93 [95% CI 1.72, 4.99]) and type 2 diabetes (OR 2.21 [95% CI 1.17, 4.17]). The highest odds for the metabolic syndrome and type 2 diabetes were observed in individuals with low CRF and high ST (CRF_low–ST_high) (OR [95% CI]: the metabolic syndrome, 9.22 [5.74, 14.80]; type 2 diabetes, 8.38 [4.83, 14.55]). Conclusions/interpretation These data suggest that ST, HPA and CRF should all be targeted in order to optimally reduce the risk for the metabolic syndrome and type 2 diabetes.

This cross-sectional study is one of the first to examine and compare the independent associations of objectively measured sedentary time, moderate to vigorous physical activity (MVPA) and fitness with cardio-metabolic risk factors. We studied 543 men and women (aged 18–49 years) from the NHANES 2003–2004 survey. Sedentary time and MVPA were measured by accelerometry. Fitness was assessed with a submaximal treadmill test. Cardio-metabolic risk factors included: waist circumference (WC), BMI, blood pressure, fasting glucose, HDL- and non HDL cholesterol, triglycerides (TG), and C-reactive protein (CRP). Sedentary time, MVPA and fitness were used as predictors for the cardio-metabolic outcomes in a multiple regression analysis. Standardized regression coefficients were computed. Results show that sedentary time was associated with HDL-cholesterol (β = −0.080, p = 0.05) and TG (β = 0.080, p = 0.03). These results became non-significant after adjustment for MVPA and fitness. MVPA was associated with WC (β = −0.226), BMI (β = −0.239), TG (β = −0.108) and HDL-cholesterol (β = 0.144) (all p < 0.05). These results remained significant after adjustment for sedentary time and fitness. Fitness was associated with WC (β = −0.287), BMI (β = −0.266), systolic blood pressure (β = −0.159), TG (β = −0.092), and CRP (β = −0.130) (all p < 0.05). After adjustment for sedentary time and MVPA these results remained significant. These differences in relative importance of sedentary time, MVPA and fitness on cardio-metabolic-risk are important in the design of prevention programs. In this population, the strength of the associations between MVPA and fitness with cardio-metabolic markers appeared to be similar; both MVPA and fitness showed independent associations with cardio-metabolic risk factors. In contrast, sedentary time showed no independent associations with cardio-metabolic risk after correction for fitness and MVPA.

Aims/hypothesis: We aimed to examine associations of cardiometabolic risk factors, and (pre)diabetes, with (sensorimotor) peripheral nerve function. Methods: In 2401 adults (aged 40–75 years) we previously determined fasting glucose, HbA_1c, triacylglycerol, HDL- and LDL-cholesterol, inflammation, waist circumference, blood pressure, smoking, glucose metabolism status (by OGTT) and medication use. Using nerve conduction tests, we measured compound muscle action potential, sensory nerve action potential amplitudes and nerve conduction velocities (NCVs) of the peroneal, tibial and sural nerves. In addition, we measured vibration perception threshold (VPT) of the hallux and assessed neuropathic pain using the DN4 interview. We assessed cross-sectional associations of risk factors with nerve function (using linear regression) and neuropathic pain (using logistic regression). Associations were adjusted for potential confounders and for each other risk factor. Associations from linear regression were presented as standardised regression coefficients (β) and 95% CIs in order to compare the magnitudes of observed associations between all risk factors and outcomes. Results: Hyperglycaemia (fasting glucose or HbA_1c) was associated with worse sensorimotor nerve function for all six outcome measures, with associations of strongest magnitude for motor peroneal and tibial NCV, β_{fasting glucose} = −0.17 SD (−0.21, −0.13) and β_{fasting glucose} = −0.18 SD (−0.23, −0.14), respectively. Hyperglycaemia was also associated with higher VPT and neuropathic pain. Larger waist circumference was associated with worse sural nerve function and higher VPT. Triacylglycerol, HDL- and LDL-cholesterol, and blood pressure were not associated with worse nerve function; however, antihypertensive medication usage (suggestive of history of exposure to hypertension) was associated with worse peroneal compound muscle action potential amplitude and NCV. Smoking was associated with worse nerve function, higher VPT and higher risk for neuropathic pain. Inflammation was associated with worse nerve function and higher VPT, but only in those with type 2 diabetes. Type 2 diabetes and, to a lesser extent, prediabetes (impaired fasting glucose and/or impaired glucose tolerance) were associated with worse nerve function, higher VPT and neuropathic pain (p for trend <0.01 for all outcomes). Conclusions/interpretation: Hyperglycaemia (including the non-diabetic range) was most consistently associated with early-stage nerve damage. Nonetheless, larger waist circumference, inflammation, history of hypertension and smoking may also independently contribute to worse nerve function.

Background: In an ageing population, regular physical activity (PA) and exercise have been recognized as important factors in maintaining physical function and thereby preventing loss of independence and disability. However, (older) adults spent the majority of their day sedentary and therefore insight into the consequences of sedentary behavior on physical function, independent of PA, is warranted. Objective: To examine the associations of objectively measured sedentary time (ST), patterns of sedentary behavior, overall PA, and higher intensity PA (HPA) with objective measures of physical function. Methods: This is a cross-sectional study in 1,932 men and women (aged 40-75 years) participating in The Maastricht Study. The activPAL3 was used to assess daily sedentary behavior: ST (h), sedentary breaks (n), prolonged (≥30min) sedentary bouts (n), and to assess time spent in (H)PA (h). Measures of physical function included: covered distance during a six minute walk test (6MWD (meters)), timed chair rise stand test performance (TCSTtime (seconds)), grip strength (kg kg 1), and elbow flexion and knee extension strength (Nm kg 1). Linear regression analyses were used to examine associations between daily sedentary behavior and PA with physical function. Results: Every hour ST was associated with shorter 6MWD (B= -2.69 m (95% CI= -4.69;-0.69)) and lower relative elbow extension strength (B= -0.01 Nm kg-1 (-0.02;0.00). More sedentary breaks were associated with faster TCSTtime: B= -0.55 s (-0.85;-0.26). Longer average sedentary bout duration was associated with slower TCSTtime (B= 0.17 s (0.09;0.25)) and lower knee extension strength (B=-0.01 Nm kg-1(-0.02;0.00)). Every hour of PA and HPA were associated with greater 6MWD (BPA= 15.88 m (9.87;21.89), BHPA= 40.72 m (30.18;51.25)), faster TCSTtime (BPA= -0.55 s (-1.03;-0.07), BHPA= -2.25 s (-3.09;-1.41)), greater elbow flexion strength (BPA=0.03 Nm kg-1 (0.01; 0.07)), (BHPA=0.05 Nm kg-1 (0.01;0.08)), and greater knee extension strength (BPA= 0.04 Nm kg-1 (0.01; 0.07)), (BHPA= 0.13 Nm kg-1 (0.06;0.20)). Conclusion: In adults aged 40-75 years, sedentary behavior appeared to be marginally associated with lower physical function, independent of HPA. This suggests that merely reducing sedentary behavior is insufficient to improve/maintain physical function. In contrast, engaging regularly in PA, in particular HPA, is important for physical function.

Van den Heuvel AMJ, Kerry P, van der Velde JHPM, Patterson MJ, Taylor NAS. Torso undergarments: their merit for clothed and armored individuals in hot-dry conditions. Aviat Space Environ Med 2010; 81:1107–13. Introduction: The aim of this study was to evaluate how the textile composition of torso undergarment fabrics may impact upon thermal strain, moisture transfer, and the thermal and clothing comfort of fully clothed, armored individuals working in a hot-dry environment (41.2°C and 29.8% relative humidity). Methods: Five undergarment configurations were assessed using eight men who walked for 120 min (4 km · h⁻¹), then alternated running (2 min at 10 km · h⁻¹) and walking (2 min at 4 km · h⁻¹) for 20 min. Trials differed only in the torso undergarments worn: no t-shirt (Ensemble A); 100% cotton t-shirt (Ensemble B); 100% woolen t-shirt (Ensemble C); synthetic t-shirt (Ensemble D: nylon, polyethylene, elastane); hybrid shirt (Ensemble E). Results: Thermal and cardiovascular strain progressively increased throughout each trial, with the average terminal core temperature being 38.5°C and heart rate peaking at 170 bpm across all trials. However, no significant between-trial separations were evident for core or mean skin temperatures, or for heart rate, sweat production, evaporation, the within-ensemble water vapor pressures, or for thermal or clothing discomfort. Conclusion: Thus, under these conditions, neither the t-shirt textile compositions, nor the presence or absence of an undergarment, offered any significant thermal, central cardiac, or comfort advantages. Furthermore, there was no evidence that any of these fabrics created a significantly drier microclimate next to the skin.