Leg Fidgeting During Prolonged Sitting Improves Postprandial Glycemic Control in People with Obesity

Joint association of antioxidant intakes from diet and supplements and sedentary behavior with all-cause and cardiovascular disease mortality among US adults

BACKGROUND

Imbalanced dietary patterns, sedentary behavior, and other unhealthy lifestyle behaviors are among the potentially modifiable risk factors most consistently linked to all-cause and cardiovascular disease (CVD) mortality. This study aimed to investigate the joint association of antioxidant intakes from diet and supplements and sedentary behavior with all-cause and CVD mortality.

METHODS

This retrospective cohort study included 16,019 adults from National Health and Nutrition Examination Survey (NHANES) 2007-2014. All-cause and CVD mortality was ascertained by linkage to National Death Index records through 31 December 2019. Participants were divided into four lifestyle patterns based on their intake of six antioxidants from dietary intakes and supplements and their self-reported sedentary behavior: low-antioxidant diet and prolonged sedentary behavior, low-antioxidant diet and nonprolonged sedentary behavior, high-antioxidant diet and prolonged sedentary behavior, high-antioxidant diet and nonprolonged sedentary behavior. Multivariable Cox proportional hazards models were utilized to evaluate the associations of antioxidant diet and sedentary behavior with regards to all-cause and CVD mortality.

RESULTS

Over an average follow-up of 8.5 years, a total of 1,894 overall deaths and 482 CVD deaths were reported. Compared with the low-antioxidant diet and prolonged sedentary behavior group, participants in the high-antioxidant diet and nonprolonged sedentary behavior group had a significantly lower risk of all-cause (hazard ratio [HR], 0.60; 95% confidence interval [CI], 0.50-0.72) and CVD (0.51; 0.34-0.77) mortality. Similarly, individuals following a low-antioxidant diet and engaging in nonprolonged sedentary behavior also had a reduced risk of all-cause (0.63; 0.52-0.75) and CVD (0.54; 0.38-0.76) mortality. On the other hand, there was no significant reduction in all-cause mortality among individuals in the high-antioxidant diet and prolonged sedentary behavior group (0.83; 0.68-1.03), as well as CVD mortality (0.87; 0.62-1.21). Subgroup and sensitivity analyses yielded results that were consistent with the overall analysis.

CONCLUSIONS

Participants with both high-antioxidant diet and nonprolonged sedentary behavior had the lowest all-cause and CVD mortality. Additionally, nonprolonged sedentary behavior can help counteract the harms of low-antioxidant diet, whereas a high-antioxidant diet fails to offset the deleterious effect of prolonged sedentary behavior.

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 d 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;%EMG MVC ); EMG activity duration (% above signal baseline 3 μV); and usual (weighted medians) EMG activity bout amplitude (%EMG MVC ) and duration (s). In the free-living study, these were regressed against risk markers (waist, fat percentage, fasting plasma glucose, total cholesterol, high-density lipid cholesterol, low-density lipid cholesterol, 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 (%EMG MVC ), respectively, and being active for 30% and 25% of the time. Higher hamstring aEMG and EMG activity duration were beneficially associated with waist, high-density lipid cholesterol and fat percentage (duration only) and a longer quadriceps usual EMG activity bout duration was beneficially associated with fasting plasma glucose. 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.

Imprecision nutrition? Intraindividual variability of glucose responses to duplicate presented meals in adults without diabetes

BACKGROUND

Continuous glucose monitors (CGMs) are used to characterize postprandial glucose responses and provide personalized dietary advice to minimize glucose excursions. The efficacy of such advice depends on reliable glucose responses.

OBJECTIVES

To explore within-subject variability of CGM responses to duplicate presented meals in an inpatient setting.

METHODS

CGM data were collected from two inpatient feeding studies in 30 participants without diabetes, capturing 1189 responses to duplicate meals presented ∼1 wk apart from four dietary patterns. One study used two different CGMs (Abbott Freestyle Libre Pro and Dexcom G4 Platinum) whereas the other study used only Dexcom. We calculated the incremental area under the curve (iAUC) for glucose for each 2-h postmeal period and compared within-subject, within-CGM responses to duplicate presented meals using linear correlations, intra-class correlation coefficients (ICC), and Bland-Altman analyses. Individual variability of interstitial glucose responses to duplicate meals were also compared with different meals using standard deviations (SDs).

RESULTS

There were weak-to-moderate positive linear correlations between within-subject iAUCs for duplicate meals [Abbott r = 0.46, 95% confidence interval (CI): 0.38, 0.54, P < 0.0001 and Dexcom r = 0.45, 95% CI: 0.39, 0.50, P < 0.0001], with low within-participant reliability indicated by ICC (Abbott 0.28, Dexcom 0.17). Bland-Altman analyses indicated wide limits of agreement (LoA) (Abbott -29.8 to 28.4 mg/dL and Dexcom -29.4 to 32.1 mg/dL) but small bias of mean iAUCs for duplicate meals (Abbott -0.7 mg/dL and Dexcom 1.3 mg/dL). The individual variability of interstitial glucose responses to duplicate meals was similar to that of different meals evaluated each diet week for both Abbott [SDweek1 11.7 mg/dL (compared with duplicate P = 0.01), SDweek2 10.6 mg/dL (P = 0.43), and SDduplicate 10.1 mg/dL] and Dexcom [SDweek1 10.9 mg/dL (P = 0.62), SDweek2 11.0 mg/dL (P = 0.73), and SDduplicate 11.2 mg/dL].

CONCLUSIONS

Individual postprandial CGM responses to duplicate meals were highly variable in adults without diabetes. Personalized diet advice on the basis of CGM measurements requires more reliable methods involving aggregated repeated measurements. This trial was registered at clinicaltrials.gov as NCT03407053 and NCT03878108.

The metabolic effects of habitual leg shaking: A randomized crossover trial

AIMS

The adverse effects of sedentary behavior on obesity and chronic diseases are well established. However, the prevalence of sedentary behavior has increased, with only a minority of individuals meeting the recommended physical activity guidelines. This study aimed to investigate whether habitual leg shaking, a behavior traditionally considered unfavorable, could serve as an effective strategy to improve energy metabolism.

MATERIALS AND METHODS

A randomized crossover study was conducted, involving 15 participants (mean [SD] age, 25.4 [3.6]; mean [SD] body mass index, 22 [3]; 7 women [46.7%]). The study design involved a randomized sequence of sitting and leg shaking conditions, with each condition lasting for 20 min. Energy expenditure, respiratory rate, oxygen saturation, and other relevant variables were measured during each condition.

RESULTS

Compared to sitting, leg shaking significantly increased total energy expenditure [1.088 kj/min, 95% confidence interval, 0.69-1.487 kj/min], primarily through elevated carbohydrate oxidation. The average metabolic equivalent during leg shaking exhibited a significant increase from 1.5 to 1.8. Leg shaking also raised respiratory rate, minute ventilation, and blood oxygen saturation levels, while having no obvious impact on heart rate or blood pressure. Electromyography data confirmed predominant activation of lower leg muscles and without increased muscle fatigue. Intriguingly, a significant correlation was observed between the increased energy expenditure and both the frequency of leg shaking and the muscle mass of the legs.

CONCLUSIONS

Our study provides evidence that habitual leg shaking can boost overall energy expenditure by approximately 16.3%. This simple and feasible approach offers a convenient way to enhance physical activity levels.

Exercise Prescription for Postprandial Glycemic Management

The detrimental impacts of postprandial hyperglycemia on health are a critical concern, and exercise is recognized a pivotal tool in enhancing glycemic control after a meal. However, current exercise recommendations for managing postprandial glucose levels remain fairly broad and require deeper clarification. This review examines the existing literature aiming to offer a comprehensive guide for exercise prescription to optimize postprandial glycemic management. Specifically, it considers various exercise parameters (i.e., exercise timing, type, intensity, volume, pattern) for crafting exercise prescriptions. Findings predominantly indicate that moderate-intensity exercise initiated shortly after meals may substantially improve glucose response to a meal in healthy individuals and those with type 2 diabetes. Moreover, incorporating short activity breaks throughout the exercise session may provide additional benefits for reducing glucose response.

Imprecision nutrition? Duplicate meals result in unreliable individual glycemic responses measured by continuous glucose monitors across four dietary patterns in adults without diabetes

Background

Continuous glucose monitors (CGMs) are being used to characterize postprandial glycemic responses and thereby provide personalized dietary advice to minimize glycemic excursions. However, the efficacy of such advice depends on reliable CGM responses.

Objective

To explore within-subject variability of CGM responses to duplicate meals in an inpatient setting.

Methods

CGM data were collected in two controlled feeding studies (NCT03407053 and NCT03878108) in 30 participants without diabetes capturing 1056 meal responses in duplicate ~1 week apart from four dietary patterns. One study used two different CGMs (Abbott Freestyle Libre Pro and Dexcom G4 Platinum) whereas the other study used only Dexcom. We calculated the incremental area under the curve (iAUC) for each 2-h post-meal period and compared within-subject iAUCs using the same CGM for the duplicate meals using linear correlations, intra-class correlation coefficients (ICC), Bland-Altman analyses, and compared individual variability of glycemic responses to duplicate meals versus different meals using standard deviations (SDs).

Results

There were weak to moderate positive linear correlations between within- subject iAUCs for duplicate meals (Abbott r=0.47, p<0.0001, Dexcom r=0.43, p<0.0001), with low within-participant reliability indicated by ICC (Abbott 0.31, Dexcom 0.14). Bland-Altman analyses indicated wide limits of agreement (Abbott -31.3 to 31.5 mg/dL, Dexcom -30.8 to 30.4 mg/dL) but no significant bias of mean iAUCs for duplicate meals (Abbott 0.1 mg/dL, Dexcom -0.2 mg/dL). Individual variability of glycemic responses to duplicate meals was similar to that of different meals evaluated each diet week for both Abbott (SDduplicate = 10.7 mg/dL , SDweek 1 =12.4 mg/dL, SDweek 2 =11.6 mg/dL, p=0.38) and Dexcom (SDduplicate = 11.1 mg/dL, SDweek 1 = 11.5 mg/dL, SDweek 2 =11.9 mg/dL, p=0.60).

Conclusions

Individual postprandial CGM responses to duplicate meals were unreliable in adults without diabetes. Personalized diet advice based on CGM measurements in adults without diabetes requires more reliable methods involving aggregated repeated measurements.

Responsiveness of electromyographically assessed skeletal muscle inactivity: methodological exploration and implications for health benefits

Prolonged sedentary behaviour is detrimental to health due to low contractile activity in large lower extremity muscle groups. This muscle inactivity can be measured with electromyography (EMG), but it is unknown how methodological factors affect responsiveness longitudinally. This study ranks 16 different EMG inactivity thresholds based on their responsiveness (absolute and standardized effect size, responsiveness) using data from a randomized controlled trial targeted at reducing and breaking up sedentary time (InPact, ISRCTN28668090). EMG inactivity duration and usual EMG inactivity bout duration (weighted median of bout lengths) were measured from large lower extremity muscle groups (quadriceps, hamstring) with EMG-sensing shorts. The results showed that the EMG inactivity threshold above signal baseline (3 μV) provided overall the best responsiveness indices. At baseline, EMG inactivity duration of 66.8 ± 9.6% was accumulated through 73.9 ± 36.0 s usual EMG inactivity bout duration, both of which were reduced following the intervention (-4.8 percentage points, -34.3 s). The proposed methodology can reduce variability in longitudinal designs and the detailed results can be used for sample size calculations. Reducing EMG inactivity duration and accumulating EMG inactivity in shorter bouts has a potential influence on muscle physiology and health.

A potent physiological method to magnify and sustain soleus oxidative metabolism improves glucose and lipid regulation

Slow oxidative muscle, most notably the soleus, is inherently well equipped with the molecular machinery for regulating blood-borne substrates. However, the entire human musculature accounts for only ∼15% of the body’s oxidative metabolism of glucose at the resting energy expenditure, despite being the body’s largest lean tissue mass. We found the human soleus muscle could raise local oxidative metabolism to high levels for hours without fatigue, during a type of soleus-dominant activity while sitting, even in unfit volunteers. Muscle biopsies revealed there was minimal glycogen use. Magnifying the otherwise negligible local energy expenditure with isolated contractions improved systemic VLDL-triglyceride and glucose homeostasis by a large magnitude, e.g., 52% less postprandial glucose excursion (∼50 mg/dL less between ∼1 and 2 h) with 60% less hyperinsulinemia. Targeting a small oxidative muscle mass (∼1% body mass) with local contractile activity is a potent method for improving systemic metabolic regulation while prolonging the benefits of oxidative metabolism.

•

We developed a method to capitalize upon the unique phenotype of the soleus

•

“A high quality versus large quantity perspective” for muscle activation

•

Singular movement targeting the 1 kg soleus easily sustains oxidative metabolism

•

This method provides a distinct muscular activity stimulus for metabolic control