Introduction:

Poor cardiorespiratory fitness (CRF) is associated with adverse health outcomes. Previous observational and cross-sectional studies have suggested that reducing sedentary behavior (SB) might improve CRF. Therefore, we investigated the effects of a 6-month intervention of reducing SB on CRF in 64 sedentary inactive adults with metabolic syndrome in a non-blind randomized controlled trial.

Materials and Methods:

In the intervention group (INT, n = 33), the aim was to reduce SB by 1 h/day for 6 months without increasing exercise training. Control group (CON, n = 31) was instructed to maintain their habitual SB and physical activity. Maximal oxygen uptake (VO2max) was measured by maximal graded bicycle ergometer test with respiratory gas measurements. Physical activity and SB were measured during the whole intervention using accelerometers.

Results:

Reduction in SB did not improve VO2max statistically significantly (group × time p > 0.05). Maximal absolute power output (Wmax) did not improve significantly but increased in INT compared to CON when scaled to fat free mass (FFM) (at 6 months INT 1.54 [95% CI: 1.41, 1.67] vs. CON 1.45 [1.32, 1.59] Wmax/kgFFM, p = 0.036). Finally, the changes in daily step count correlated positively with the changes in VO2max scaled to body mass and FFM (r = 0.31 and 0.30, respectively, p < 0.05).

Discussion:

Reducing SB without adding exercise training does not seem to improve VO2max in adults with metabolic syndrome. However, succeeding in increasing daily step count may increase VO2max. © 2023 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.

Purpose: This study aimed to investigate whether a reduction in daily sedentary behavior (SB) improves insulin sensitivity in adults with metabolic syndrome in 6 months, without adding intentional exercise training.

Methods: Sixty-four sedentary inactive middle-age adults with overweight and metabolic syndrome (mean (SD) age, 58 (7) yr; mean (SD) body mass index, 31.6 (4.3) kg.m(-2); 27 men) were randomized into intervention and control groups. The 6-month individualized behavioral intervention supported by an interactive accelerometer and a mobile application aimed at reducing daily SB by 1 h compared with baseline. Insulin sensitivity by hyperinsulinemic euglycemic clamp, body composition by air displacement plethysmography, and fasting blood samples were analyzed before and after the intervention. SB and physical activity were measured with hip-worn accelerometers throughout the intervention.

Results: SB decreased by 40 (95% confidence interval, 17-65) min.d(-1), and moderate-to-vigorous physical activity increased by 20 (95% confidence interval, 11-28) min.d(-1) on average in the intervention group with no significant changes in these outcomes in the control group. After 6 months, fasting plasma insulin decreased (similar to 1 mU.L-1) in the intervention group compared with the control group (time-group, P = 0.0081), but insulin sensitivity did not change in either group. The changes in body mass or adiposity did not differ between groups. Among all participants, the changes in SB and body mass correlated inversely with the change in insulin sensitivity (r = -0.31, -0.44; P = 0.025, 0.0005, respectively).

Conclusions: An intervention aimed at reducing daily SB resulted in slightly decreased fasting insulin, but had no effects on insulin sensitivity or body adiposity. However, as the change in insulin sensitivity associated with the changes in SB and body mass, multifaceted interventions targeting to weight loss are likely to be beneficial in improving whole-body insulin sensitivity. © Lippincott Williams & Wilkins.

Background: It is widely accepted that exercise alters the number and function of circulating leukocytes, and many factors are suggested to influence this phenomenon. The aim here was to compare white blood cell mobilization between sexes after acute vigorous-intensity exercise bout.

Methods: The study included healthy and physically active subjects, 10 men (aged 26 (SD 7) years) and 10 women (aged 33 (SD 8) years). Participants performed a 30-min cycling ergometer exercise at 70% VO2max. Blood samples were drawn at rest and 3 min, 1 and 2 h post-exercise. Changes in total leukocyte, neutrophil, lymphocyte, monocyte, eosinophil, and basophil count were analyzed and corrected for plasma volume change.

Results: Women had higher lymphocyte counts and lower eosinophil proportion of total leukocytes compared to men at all time points. Acute exercise significantly increased the number of total leukocytes and all leukocyte subpopulations excluding eosinophils in both women and men. The mobilization of all leukocyte subpopulations was similar in both sexes, but mobilization of total leukocytes, as a percentage change from rest, was greater in men. Increase in total leukocyte, neutrophil, and lymphocyte counts correlated positively with lactate concentration at 3-min timepoint and decrease in lymphocyte and basophil count after exercise correlated negatively with mean exercising heart rate in both sexes.

Conclusion: Our findings indicate that mobilization of total leukocytes is greater in men. The sex-difference however is small and not observed in any leukocyte subpopulations. Further, exercise intensity driven physiological perturbation has a role in immune cell mobilization.

The role of exercise in cancer prevention and control is increasingly recognized, and based on preclinical studies, it is hypothesized that mobilization of leukocytes plays an important role in the anti-tumor effect. Thus, we examined how 10-min acute exercise modulates immune cells in newly diagnosed breast cancer patients. Blood samples were taken at rest, immediately after exercise and 30 min after exercise and phenotypic characterization of major leukocyte subsets was done using 9-color flow cytometry. Total leukocyte count increased by 29%, CD8+ T cell count by 34%, CD19+ B cell count by 18%, CD56+CD16+ NK cell count by 130%, and CD14+CD16+ monocyte count by 51% immediately after acute exercise. Mobilization of CD45+, CD8+, CD19+, and CD56+CD16+ cells correlated positively with exercising systolic blood pressure, heart rate percentage of age predicted maximal heart rate, rate pressure product, and mean arterial pressure. Our findings indicate that a single bout of acute exercise of only 10 min can cause leukocytosis in breast cancer patients. Mobilization of leukocytes appear to be directly related to the intensity of exercise. It is possible that the positive effect of exercise on oncologic outcome might be partly due to immune cell mobilization as documented in the present study. © 2023, The Author(s).

Sedentary behavior (SB) and physical inactivity associate with impaired insulin sensitivity. We investigated whether an intervention aimed at a 1-h reduction in daily SB during 6 mo would improve insulin sensitivity in the weight-bearing thigh muscles. Forty-four sedentary inactive adults [mean age 58 (SD 7) yr; 43% men] with metabolic syndrome were randomized into intervention and control groups. The individualized behavioral intervention was supported by an interactive accelerometer and a mobile application. SB, measured with hip-worn accelerometers in 6-s intervals throughout the 6-mo intervention, decreased by 51 (95% CI 22-80) min/day and physical activity (PA) increased by 37 (95% CI 18-55) min/day in the intervention group with nonsignificant changes in these outcomes in the control group. Insulin sensitivity in the whole body and in the quadriceps femoris and hamstring muscles, measured with hyperinsulinemic-euglycemic clamp combined with [¹⁸F]fluoro-deoxy-glucose PET, did not significantly change during the intervention in either group. However, the changes in hamstring and whole body insulin sensitivity correlated inversely with the change in SB and positively with the changes in moderate-to-vigorous PA and daily steps. In conclusion, these results suggest that the more the participants were able to reduce their SB, the more their individual insulin sensitivity increased in the whole body and in the hamstring muscles but not in quadriceps femoris. However, according to our primary randomized controlled trial results, this kind of behavioral interventions targeted to reduce sedentariness may not be effective in increasing skeletal muscle and whole body insulin sensitivity in people with metabolic syndrome at the population level.

NEW & NOTEWORTHY Aiming to reduce daily SB by 1 h/day had no impact on skeletal muscle insulin sensitivity in the weight-bearing thigh muscles. However, successfully reducing SB may increase insulin sensitivity in the postural hamstring muscles. This emphasizes the importance of both reducing SB and increasing moderate-to-vigorous physical activity to improve insulin sensitivity in functionally different muscles of the body and thus induce a more comprehensive change in insulin sensitivity in the whole body.

BACKGROUND: Cardiorespiratory fitness (CRF) has been inversely associated with insulin resistance and clustering of cardiometabolic risk factors among overweight and obese individuals. However, most previous studies have scaled CRF by body mass (BM) possibly inflating the association between CRF and cardiometabolic health. We investigated the associations of peak oxygen uptake (V?O2peak) and peak power output (Wpeak) scaled either by BM-1, fat free mass (FFM-1), or by allometric methods with individual cardiometabolic risk factors and clustering of cardiometabolic risk factors in 55 overweight or obese adults with metabolic syndrome. METHODS: VO2peak and Wpeak were assessed by a maximal cycle ergometer exercise test. FFM was measured by air displacement plethysmo- graph and glucose, insulin, HbA1c, triglycerides, and total, LDL, and HDL cholesterol from fasting blood samples. HOMA-IR and metabolic syndrome score (MetS) were computed. RESULTS: VO2peak and Wpeak scaled by BM-1 were inversely associated with insulin (β=-0.404 to -0.372, 95% CI: -0.704 to -0.048), HOMAIR (β=-0.442 to -0.440, 95% CI: -0.762 to -0.117), and MetS (β=-0.474 to -0.463, 95% CI: -0.798 to -0.127). Other measures of CRF were not associated with cardiometabolic risk factors. CONCLUSIONS: Our results suggest that using BM-1 as a scaling factor confounds the associations between CRF and cardiometabolic risk in overweight/obese adults with the metabolic syndrome. © 2022 EDIZIONI MINERVA MEDICA.

Objective: The objective of the study was to investigate the associations of sedentary time, physical activity, and cardiorespiratory fitness with skeletal muscle glucose uptake (GU). Methods: Sedentary time and physical activity were measured with accelerometers and VO2max with cycle ergometry in 44 sedentary adults with metabolic syndrome. Thigh muscle GU was determined with [¹⁸F]FDG-PET imaging. Results: Sedentary time (β = −0.374), standing (β = 0.376), steps (β = 0.351), and VO₂max (β = 0.598) were associated with muscle GU when adjusted for sex, age, and accelerometer wear time. Adjustment for body fat-% turned all associations non-significant. Conclusion: Body composition is a more important determinant of muscle GU in this population than sedentary time, physical activity, or fitness. © 2022 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.

Purpose: The muscle perfusion response to postexercise cold-water immersion (CWI) is not well understood. We examined the effects of graded postexercise CWI upon global and regional quadriceps femoris muscle perfusion using positron emission tomography and [¹⁵O]H₂O. Methods: Using a matched-group design, 30 healthy men performed cycle ergometer exercise at 70% VO_2peak to a core body temperature of 38°C, followed by either 10 min of CWI at 8°C, 22°C, or seated rest (control). Quadriceps muscle perfusion; thigh and calf cutaneous vascular conductance; intestinal, muscle, and local skin temperatures; thermal comfort; mean arterial pressure; and heart rate were assessed at preexercise, postexercise, and after CWI. Results: Global quadriceps perfusion was reduced beyond the predefined minimal clinically relevant threshold (0.75 mL per 100 g·min^-1) in 22°C water versus control (difference (95% confidence interval (CI)), -2.5 (-3.9 to -1.1) mL per 100 g·min^-1). Clinically relevant decreases in muscle perfusion were observed in the rectus femoris (-2.0 (-3.0 to -1.0) mL per 100 g·min^-1) and vastus lateralis (-3.5 (-4.9 to -2.0) mL per 100 g·min^-1) in 8°C water, and in the vastus lateralis (-3.3 (-4.8 to -1.9) mL per 100 g·min^-1) in 22°C water versus control. The mean effects for vastus intermedius and vastus medialis perfusion were not clinically relevant. Clinically relevant decreases in thigh and calf cutaneous vascular conductance were observed in both cooling conditions. Conclusions: The present findings revealed that less noxious CWI (22°C) promoted clinically relevant postexercise decreases in global quadriceps muscle perfusion, whereas noxious cooling (8°C) elicited no effect. © Lippincott Williams & Wilkins

Background: This study examined whether hemoglobin (Hb) and white blood cell count (WBC) associate with body adiposity and other cardiometabolic risk factors, as well as accelerometer-measured sedentary behavior (SB) and physical activity (PA), when adjusted for body mass index (BMI). Methods: The cross-sectional analysis included 144 participants (42 men) with a mean age of 57.0 years and a mean BMI of 31.7 kg/m2. SB and standing time, breaks in sedentary time and PA were measured during four consecutive weeks with hip-worn accelerometers. A fasting blood sample was collected from each participant during the 4-week measurement period and analyzed using Sysmex XN and Cobas 8000 c702 analyzers. Associations of WBC, Hb and other red blood cell markers with cardiometabolic risk factors and physical activity were examined by Pearson’s partial correlation coefficient test and with linear mixed regression models. Results: In sex- and age-adjusted correlation analyses both BMI and waist circumference correlated positively with Hb, WBC, red blood cell count (RBC), and hematocrit. Hb was also positively correlated with systolic blood pressure, insulin resistance scores, liver enzymes, LDL, and triglyceride levels. Sedentary time correlated positively with WBC, whereas standing time correlated negatively with WBC. Lying time correlated positively with WBC, RBC, hematocrit, and Hb. Regarding SB and PA measures, only the association between lying time and RBC remained significant after adjustment for the BMI. Conclusion: We conclude that body adiposity, rather than components of SB or PA, associates with Hb levels and WBC, which cluster with general metabolic derangement. © 2022 by the authors.

Objectives: To investigate if reducing sedentary behavior improves cardiometabolic biomarkers in adults with metabolic syndrome. Design: Randomized controlled trial. Methods: Sixty-four sedentary middle-aged adults with metabolic syndrome were randomized into intervention (INT; n = 33) and control (CON; n = 31) groups. INT was guided to limit sedentary behavior by 1 h/day through increased standing and light-intensity physical activity. CON was instructed to maintain usual habits. Sedentary behavior, breaks in sedentary behavior, standing, and physical activity were measured with hip-worn accelerometers for three months. Fasting blood sampling and measurements of anthropometrics, body composition, and blood pressure were performed at baseline and at three months. Linear mixed models were used for statistical analyses. Results: INT reduced sedentary behavior by 50 (95% CI: 24, 73) min/day by increasing light-intensity and moderate-to-vigorous physical activity (19 [8, 30] and 24 [14, 34] min/day, respectively). Standing increased also, but non-significantly (6 [−11, 23] min/day). CON maintained baseline activity levels. Significant intervention effects favoring INT occurred in fasting insulin (INT: 83.4 [68.7, 101.2] vs. CON: 102.0 [83.3, 125.0] pmol/l at three months), insulin resistance (HOMA-IR; 3.2 [2.6, 3.9] vs. 4.0 [3.2, 4.9]), HbA1c (37 [36, 38] vs. 38 [37, 39] mmol/mol), and liver enzyme alanine aminotransferase (28 [24, 33] vs. 33 [28, 38] U/l). Conclusions: Reducing sedentary behavior by 50 min/day and increasing light-intensity and moderate-to-vigorous activity showed benefits in several cardiometabolic biomarkers in adults with metabolic syndrome. Replacing some of the daily sedentary behavior with light-intensity and moderate-to-vigorous physical activity may help in cardiometabolic disease prevention in risk populations. © 2022 The Authors