Joyce S. Ramos

Fitness is independently associated with central hemodynamics in metabolic syndrome

PURPOSE Fit individuals with metabolic syndrome (MetS) have lower mortality risk compared with less fit counterparts, despite the presence of obesity as a component of the syndrome. To understand the importance of fitness in treating this condition, we examined the association of fitness and fatness with central hemodynamic indices that are known independent predictors of cardiovascular events. METHODS Sixty-eight individuals with MetS participated in this cross-sectional study. Central hemodynamics is calculated from radial applanation tonometry and comprised aortic reservoir pressure, backward pressure wave (Pb), reflection magnitude (RM), and augmentation index at 75 bpm (AIx75). Cardiorespiratory fitness (CRF) and body fat percentage (BF%) were determined via indirect calorimetry during maximal exercise testing and dual-energy x-ray absorptiometry, respectively. RESULTS CRF was inversely associated with aortic reservoir pressure (r = -0.29, P = 0.02), Pb (r = -0.42, P < 0.001), RM (r = -0.48, P < 0.001), and AIx75 (r = -0.65, P < 0.001). BF% was also correlated with AIx75 (r = 0.37, P < 0.05) and RM (r = 0.36, P < 0.005) but at a weaker association compared with CRF. Multiple regression analysis revealed CRF as a predictor of aortic reservoir pressure (β = -0.52, P = <0.01), Pb (β = -0.41, P < 0.03), and AIx75 (β = -0.45, P = 0.01), independent of BF% and other confounding factors. CONCLUSIONS CRF predicts central hemodynamics independent of BF% and other confounding factors. This suggests that CRF improvement may be a higher priority when compared with fat loss for lowering the risk of cardiovascular mortality in MetS individuals.

12 min/week of high-intensity interval training reduces aortic reservoir pressure in individuals with metabolic syndrome: a randomized trial.

Objective: Decreased aortic reservoir function leads to a rise in aortic reservoir pressure that is an independent predictor of cardiovascular events. Although there is evidence that high-intensity interval training (HIIT) would be useful to improve aortic reservoir pressure, the optimal dose of high-intensity exercise to improve aortic reservoir function has yet to be investigated. Therefore, this study compared the effect of different volumes of HIIT and moderate-intensity continuous training (MICT) on aortic reservoir pressure in participants with the metabolic syndrome (MetS). Methods: Fifty individuals with MetS were randomized into one of the following 16-week training programs: MICT [n = 17, 30 min at 60–70% peak heart rate (HRpeak), five times/week]; 4 × 4-min high-intensity interval training (4HIIT) (n = 15, 4 × 4 min bouts at 85–95% HRpeak, interspersed with 3 min of active recovery at 50–70% HRpeak, three times/week); and 1 × 4-min high-intensity interval training (1HIIT) (n = 18, 1 × 4 min bout at 85–95% HRpeak, three times/week). Aortic reservoir pressure was calculated from radial applanation tonometry. Results: Although not statistically significant, there was a trend for a small-to-medium group × time interaction effect on aortic reservoir pressure, indicating a positive adaptation following 1HIIT compared with 4HIIT and MICT [F (2,46) = 2.9, P = 0.07, &eegr;2 = 0.06]. This is supported by our within-group analysis wherein only 1HIIT significantly decreased aortic reservoir pressure from pre to postintervention (pre–post: 1HIIT 33 ± 16 to 31 ± 13, P = 0.03; MICT 29 ± 9–28 ± 8, P = 0.78; 4HIIT 28 ± 10–30 ± 9 mmHg, P = 0.10). Conclusion: Three sessions of 4 min of high-intensity exercise per week (12 min/week) was sufficient to improve aortic reservoir pressure, and thus may be a time-efficient exercise modality for reducing cardiovascular risk in individuals with MetS.

Impact of beta-blockers on cardiopulmonary exercise testing in patients with advanced liver disease

Patients with advanced liver disease may develop portal hypertension that can result in variceal haemorrhage. Beta‐blockers reduce portal pressure and minimise haemorrhage risk. These medications may attenuate measures of cardiopulmonary performance, such as the ventilatory threshold and peak oxygen uptake measured via cardiopulmonary exercise testing.

Cardiorespiratory fitness is positively associated with increased pancreatic beta cell function independent of fatness in individuals with the metabolic syndrome: Fitness versus fatness

OBJECTIVES The vulnerability of individuals with the metabolic syndrome (MetS) to cardiovascular events (CVEs) is attenuated by increased cardiorespiratory fitness (CRF), despite the presence of obesity as a usual component of MetS. To better understand the importance of CRF and body fat in treating this condition, we investigated the relationship between fitness and fatness with pancreatic beta cell function (BCF) indices that are known independent predictors of CVEs. DESIGN Cross sectional study. METHODS This study included 84 individuals with MetS. BCF indices were derived from a fasted steady state (basal disposition index [DI], proinsulin, proinsulin:insulin, and proinsulin:C-peptide) and dynamic conditions via an oral glucose tolerance test (1st and 2nd phase DI). CRF and body fat percentage (BF%) were assessed via indirect calorimetry (during a maximal exercise test) and dual energy X-ray absorptiometry, respectively. RESULTS CRF was positively associated with basal DI (r=0.40, p<0.001), 1st phase DI (r=0.49, p<0.005), and 2nd phase DI (r=0.38, p=0.02). Hierarchical multiple regression analysis showed CRF was associated with basal DI (β=0.18, p=0.04), 1st phase DI (β=0.36, p=0.04), and 2nd phase DI (β=0.33, p=0.03), independent of BF% and other confounding factors including age, sex, diabetic status, anthropometric measures, lipid profile, and insulin sensitivity. No significant associations were found between CRF and proinsulin measures. BF% was not significantly correlated with BCF indices. CONCLUSIONS Increased CRF was independently associated with enhanced BCF. This study provides evidence that equal, if not more attention should be dedicated to CRF improvement relative to fat-loss for favorable pancreatic BCF and thus possible reduction in CV risk in individuals with MetS.

High-intensity interval training and cardiac autonomic control in individuals with metabolic syndrome: A randomised trial

BACKGROUND Insulin resistance has been postulated to play a central role in the co-appearance of various cardiovascular disease risk factors constituting the metabolic syndrome (MetS). There is evidence that altered cardiac autonomic function (CAF) may precede the onset of insulin resistance. Exercise training has been shown to improve CAF in different populations, yet little is known regarding the exercise dose response for CAF. The aim of this study was to investigate the impact of different volumes of high-intensity interval training (HIIT) and traditional moderate-intensity continuous training (MICT) on CAF in participants with MetS. METHODS Individuals with MetS (n=56) were randomised into the following 16-week training interventions: i) MICT (n=16, 30min at 60-70%HRpeak, 5×/week); ii) 4HIIT (n=19, 4×4min bouts at 85-95%HRpeak, interspersed with 3min of active recovery at 50-70%HRpeak, 3×/week); or iii) 1HIIT (n=21, 1×4min bout at 85-95%HRpeak, 3×/week). R-R interval recorded for 5min in a supine position at pre- and post-intervention was used to derive linear (SDNN, RMSSD, pNN50, LF, HF, LF/HF) and non-linear (SD1, SD2, Alpha1, Alpha2, SampEn) heart rate variability (HRV) indices as measures of CAF. Group×time interaction effects were examined (ANCOVA) and Eta squared (η2) interaction effect sizes calculated. RESULTS While there were no significant between-group differences in CAF indices, there were small-to-medium group×time interaction effects on SDNN [F(2,52)=0.70, p=0.50, η2=0.02], RMSSD [F(2,52)=1.35, p=0.27, η2=0.03], HF power [F(2,52)=1.27, p=0.29, η2=0.03], SD1 [F(2,52)=0.47, p=0.63, η2=0.01], and SD2 [F(2,52)=0.41, p=0.67, η2=0.01]. The following represent the relative percentage increases across these variables for 4HIIT, MICT, and 1HIIT respectively (SDNN, +30%, +17%, 9%; RMSSD, +30%, +22%, -2%; HF power, +69%, +18%, +7%; SD1, +30%, +22%,-2%; SD2, +22%, +14%, 4%). CONCLUSIONS There were no significant between-group differences for the effects of exercise dose on CAF indices, however; high-volume HIIT demonstrated the greatest magnitude of effect for improving CAF in individuals with MetS.

Optimal criteria and sampling interval to detect a VO2 plateau at VO2max in patients with metabolic syndrome

This study sought to determine the optimal criteria and sampling interval to detect a V̇O2 plateau at V̇O2max in patients with metabolic syndrome. Twenty-three participants with criteria-defined metabolic syndrome underwent a maximal graded exercise test. Four different sampling intervals and three different V̇O2 plateau criteria were analysed to determine the effect of each parameter on the incidence of V̇O2 plateau at V̇O2max. Seventeen tests were classified as maximal based on attainment of at least two out of three criteria. There was a significant (p < 0.05) effect of 15-breath (b) sampling interval on the incidence of V̇O2 plateau at V̇O2max across the ≤50 and ≤80 mL∙min−1 conditions. Strength of association was established by the Cramer’s V statistic (φc); (≤50 mL∙min−1 [φc = 0.592, p < 0.05], ≤80 mL∙min−1 [φc = 0.383, p < 0.05], ≤150 mL∙min−1 [φc = 0.246, p > 0.05]). When conducting maximal stress tests on patients with metabolic syndrome, a 15-b sampling interval and ≤50 mL∙min−1 criteria should be implemented to increase the likelihood of detecting V̇O2 plateau at V̇O2max.

Can reducing sitting time in the university setting improve the cardiometabolic health of college students

Purpose The high prevalence of metabolic syndrome (MetS), prediabetes, and increased risk of cardiovascular diseases linked with prolonged sitting has created a need to identify options to limit sedentary behaviors. A potentially simple approach to achieve this goal in the university setting is to provide students the option to stand during courses rather than sit. The purpose of the present study was to examine the effects of standing in the college classroom setting on cardiometabolic risk factors in a cohort of college students. Patients and methods Healthy college students (n=21) who attended at least two courses per week (a minimum of 5 hours) in a specified university building with standing desks participated in a 7-week intervention that was divided into three phases: 3 weeks of standing, 1 week of washout (sitting), and 3 weeks of sitting. The participants (mean ± SD: age, height, weight, body mass index, and waist-to-hip ratio were 22.7±6.4 years, 174.3±10.0 cm, 70.6±14.3 kg, 23.0±3.0 kg/m2, and 0.76±0.05, respectively) were randomly assigned to the phase of intervention of which they should start (sitting or standing), and all participants engaged in sitting during the washout phase. Cardiometabolic risk factors and metabolic equivalents (METs) were measured at baseline and weekly throughout the intervention. Results Paired t-tests revealed significant differences (P<0.05) in all cardiometabolic risk factors between the 3 weeks of sitting and 3 weeks of standing time blocks. Moreover, MetS z-score was significantly improved (P<0.05) during the 3 weeks of standing (–5.91±2.70) vs 3 weeks of sitting (–5.25±2.69). The METs were significantly higher (P<0.05) during standing (1.47±0.09) than during sitting (1.02±0.07). Although there was considerable interindividual variability in the ∆ MetS z-score response, there was a 100% (21/21) incidence of a favorable change (ie, responders) in MetS z-score response. Conclusion A standing desk in the classroom paradigm was found to significantly improve cardiometabolic health throughout a short 3 weeks time span. Increasing standing time in the classroom, and therefore lessening weekly sedentary behavior, could be a potential wide-scale, effective strategy for primordial prevention of cardiometabolic diseases.