Blood pressure and heart rate during rest-exercise and exercise-rest transitions

The transients of mean arterial blood pressure (BPa) and heart rate (fc) during rest-exercise and exercise-rest transitions have been studied in six healthy sport students. After 5 min of rest in an upright position on a cycle ergometer they exercised for 15 min and remained seated for a further 5 min. The subjects exercised at four different constant intensities (40 W, 80 W, 120 W, 160 W) in random order separated by at least 24 h. The BPa was determined by a noninvasive and continuous method. During the first minute of exercise, three phases of response could be distinguished, with the first two showing no clear relationship to intensity. Phase 1 consisted of simultaneous increases in both fc and BP during the first 6 s. In phase 2, BPa decreased while fc continued to increase. During phase 3, BPa and fc approximated constant values or a linear increase. Both parameters showed no comparable intensity-independent reactions during the off-transients. In conclusion, during the first 15 s of rest-exercise transitions there seems to be a fast and uniform cardiovascular drive which overrode other influences on fc.     

Predictors of successful long-term weight loss maintenance: a two-year follow-up

Background

Weight regain is a common problem following weight loss intervention, with most people who seek treatment for obesity able to lose weight, but few able to sustain the changes in behavior required to prevent subsequent weight regain. The identification of factors that predict which patients will successfully maintain weight loss or who are at risk of weight regain after weight loss intervention is necessary to improve the current weight maintenance strategies. The aim of the present study is identify factors associated with successful weight loss maintenance by women with overweight or obesity who completed group cognitive behavioral treatment (CBT) for weight loss.

Methods

Ninety women with overweight or obesity completed a 7-month weight loss intervention. The data of 86 who completed follow-up surveys 12 and 24 months after the end of the treatment was analyzed. Depression, anxiety, binge eating, food addiction, and eating behaviors were assessed before and after the weight loss intervention. Participants who lost at least 10% of their initial weight during the weight loss intervention and had maintained the loss at the month 24 follow-up were defined as successful.

Results

The intervention was successful for 27 participants (31.3%) and unsuccessful for 59 (68.6%). Multiple logistic regression analysis extracted larger weight reduction during the weight loss intervention, a lower disinhibition score, and a low food addiction score at the end of the weight loss intervention as associated with successful weight loss maintenance.

Conclusion

The results suggest that larger weight reduction during the weight loss intervention and lower levels of disinhibition and food addiction at the end of the weight loss intervention predicted successful weight loss maintenance.

Trial registration

Trial registry name: Development and validation of effective treatments of weight loss and weight-loss maintenance using cognitive behavioral therapy for obese patients.Registration ID: UMIN000006803Registered 1 January 2012.URL: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000008052

     

Internal disinhibition predicts weight regain following weight loss and weight loss maintenance

Objective: The disinhibition scale of the Eating Inventory predicts weight loss outcome; however, it may include multiple factors. The purpose of this study was to examine the factor structure of the disinhibition scale and determine how its factors independently relate to long‐term weight loss outcomes. Research Methods and Procedures: Exploratory factor analysis of the disinhibition scale was conducted on 286 participants in a behavioral weight loss trial (TRIM), and confirmatory factor analysis was conducted on 3345 members of the National Weight Control Registry (NWCR), a registry of successful weight loss maintainers. Multivariate regressions were used to examine the relationships between the disinhibition scale factors and weight over time in both samples. Results: Using baseline data from TRIM, two factors were extracted from the disinhibition scale: 1) an “internal” factor that described eating in response to internal cues, such as feelings and thoughts; and 2) an “external” factor that described eating in response to external cues, such as social events. This factor structure was confirmed using confirmatory factor analysis in the NWCR. In TRIM, internal disinhibition significantly predicted weight loss at 6 months (p = 0.03) and marginally significantly predicted weight loss at 18 months (p = 0.06), with higher levels of internal disinhibition at baseline predicting less weight loss; external disinhibition did not predict weight loss at any time‐point. In NWCR, internal disinhibition significantly predicted one‐year weight change (p = 0.001), while external disinhibition did not. Discussion: These results suggest that it is the disinhibition of eating in response to internal cues that is associated with poorer long‐term weight loss outcomes.     

Blood pressure and heart rate during periodic breathing while asleep at high altitude.

The ventilatory and arterial blood pressure (ABP) responses to isocapnic hypoxia during wakefulness progressively increased in normal subjects staying 4 wk at 5,050 m (Insalaco G, Romano S, Salvaggio A, Braghiroli A, Lanfranchi P, Patruno V, Donner CF, and Bonsignore G; J Appl Physiol 80: 1724-1730, 1996). In the same subjects (n = 5, age 28-34 yr) and expedition, nocturnal polysomnography with ABP and heart rate (HR) recordings were obtained during the 1st and 4th week to study the cardiovascular effects of phasic (i.e., periodic breathing-dependent) vs. tonic (i. e., acclimatization-dependent) hypoxia during sleep. Both ABP and HR fluctuated during non-rapid eye movement sleep periodic breathing. None of the subjects exhibited an ABP increase during the ventilatory phases that correlated with the lowest arterial oxygen saturation of the preceding pauses. Despite attenuation of hypoxemia, ABP and HR behaviors during sleep in the 4th wk were similar to those in the 1st wk. Because ABP during periodic breathing in the ventilatory phase increased similarly to the ABP response to progressive hypoxia during wakefulness, ABP variations during ventilatory phases may reflect ABP responsiveness to peripheral chemoreflex sensitivity rather than the absolute value of hypoxemia, suggesting a major tonic effect of hypoxia on cardiorespiratory control at high altitude.     

Blood pressure and heart rate determination by radiotelemetry in mice

Mice are not commonly used in cardiovascular physiology, especially in space physiology because of methodological problems. The initial studies that have monitored arterial pressure and heart rate in mice used the tail cuff plethysmography method or classical catheterization techniques with a catheter liable to an external pressure transducer. But for long term arterial pressure measurements the studies have been facilitated by the development of radiotelemetry. This is a less constraining method as classical one allowing to monitor in continuous in freely moving animal blood pressure, heart rate and temperature. This technique allows to record these parameters thank to an implanted transmitter without physical connection with the monitoring system. The aim of this work was to valid the use of the radiotelemetry in mice to evaluate arterial blood pressure and heart rate during different stress conditions (but only control data are described in this paper).     

Rise of plasma ghrelin with weight loss is not sustained during weight maintenance

Objective: Ghrelin is postulated to be an orexigenic signal that promotes weight regain after weight loss (WL). However, it is not known whether this putative effect of ghrelin is sustained after weight stabilization. The objective of this study was to investigate the relationship of plasma ghrelin concentrations to active WL and weight maintenance in obese subjects. Research Methods and Procedures: This study was a randomized clinical trial, with a 12‐month follow‐up period. Obese Mexican‐American women matched for age and BMI were randomized to a 12‐month WL program (n = 25) or no intervention (controls, n = 23). Interventions included diet, exercise, and orlistat. Body weight and fasting ghrelin, leptin, insulin, and glucose concentrations were measured at baseline and 6 and 12 months. Results: The WL group lost 8.5% of body weight after 6 months and maintained the new weight for the next 6 months. Ghrelin concentrations increased significantly at 6 months but returned to baseline at 12 months. Baseline ghrelin concentrations were directly related to the degree of WL achieved after 12 months. Controls experienced no change in BMI or ghrelin levels. There were no associations between plasma ghrelin and leptin or insulin concentrations. Discussion: Consistent with previous results, ghrelin rises in response to WL, perhaps as a counterregulatory mechanism. However, the present results indicate that ghrelin concentrations return to baseline with sustained weight maintenance, suggesting that its effects are unlikely to regulate long‐term energy balance. Baseline ghrelin concentrations are related to the degree of WL that can be achieved by active weight reduction.     

Blood pressure and heart rate and withdrawal of antihypertensive drugs.

The immediate effects on heart rate and blood pressure of withdrawing antihypertensive drugs were studied over three-day periods in 26 patients. Four groups of drugs were studied. After withdrawal all patients taking clonidine showed a considerable increase in heart rate and blood pressure with intense ectopic activity. Patients taking postganglionic neurone-blocking drugs showed a similar but less pronounced reaction with increased ventricular ectopic activity. No alarming reactions were seen after withdrawal of methyldopa or beta-blocking drugs. Methyldopa and, especially, beta-blocking drugs are less likely to produce withdrawal reactions than clonidine or the postganglionic neurone-blocking drugs, and patients taking these drugs are therefore less likely to suffer violent reactions if they forget to take their tablets.     

VLCD-induced weight loss improves heart rate variability in moderately obese Japanese

To evaluate the effects of weight reduction on the autonomic nervous system in obese patients, we investigated heart rate variability (HRV) based on 24-hr ambulatory electrocardiogram (ECG) recordings before and after weight reduction. To aim for weight reduction, 16 obese patients were treated with the very-low-calorie conventional Japanese diet (VLCD-CJ) therapy combined with behavior therapy. Percent weight reduction was 17.8% +/- 1.5% (means +/- SEM), but mean blood pressure did not change significantly after VLCD-CJ therapy. The mean normal R-R interval (mNN) of the 24-hr ECG and all other five time-domain indices increased after weight reduction. Spectral analysis revealed that weight reduction increased the high frequency (HF) component, but decreased the ratio of low to high (LF/HF) components. Rate of change in mNN or HF correlated positively with reduction rate of body mass index, but not that in LF/HF. Analysis of daily fluctuations in each HRV parameter showed that significant improvement after weight loss occurred mainly during the nocturnal period, but an HF component was improved throughout the day and night periods. These findings indicate that functional impairment of the autonomic nervous system in obese subjects, particularly in the nocturnal period, is improved by effective weight reduction after VLCD-CJ therapy.     

Short-term and long-term blood pressure and heart rate variability in the mouse

Knowledge on murine blood pressure and heart rate control mechanisms is limited. With the use of a tethering system, mean arterial pressure (MAP) and pulse interval (PI) were continuously recorded for periods up to 3 wk in Swiss mice. The day-to-day variation of MAP and PI was stable from 5 days after surgery. Within each mouse (n = 9), MAP and PI varied by 21+/-6 mm Hg and 17+/-4 ms around their respective 24-h averages (97+/-3 mm Hg and 89+/-3 ms). Over 24-h periods, MAP and PI were bimodally distributed and clustered around two preferential states. Short-term variability of MAP and PI was compared between the resting (control) and active states using spectral analysis. In resting conditions, variability of MAP was mainly confined to frequencies <1 Hz, whereas variability of PI was predominantly linked to the respiration cycle (3-6 Hz). In the active state, MAP power increased in the 0.08- to 3-Hz range, whereas PI power fell in the 0.08- to 0.4-Hz range. In both conditions, coherence between MAP and PI was high at 0.4 Hz with MAP leading the PI fluctuations by 0.3-0.4 s, suggesting that reflex coupling between MAP and PI occurred at the same frequency range as in rats. Short-term variability of MAP and PI was studied after intravenous injection of autonomic blockers. Compared with the resting control state, MAP fell and PI increased after ganglionic blockade with hexamethonium. Comparable responses of MAP were obtained with the alpha-blocker prazosin, whereas the beta-blocker metoprolol increased PI similarly. Muscarinic blockade with atropine did not significantly alter steady-state levels of MAP and PI. Both hexamethonium and prazosin decreased MAP variability in the 0.08- to 1-Hz range. In contrast, after hexamethonium and metoprolol, PI variability increased in the 0.4- to 3-Hz range. Atropine had no effect on MAP fluctuations but decreased those of PI in the 0.08- to 1-Hz range. These data indicate that, in mice, blood pressure and its variability are predominantly under sympathetic control, whereas both vagal and sympathetic nerves control PI variability. Blockade of endogenous nitric oxide formation by N(G)-nitro-L-arginine methyl ester increased MAP variability specifically in the 0.08- to 0.4-Hz range, suggesting a role of nitric oxide in buffering blood pressure fluctuations.     

A satisfaction enhancement intervention for long-term weight loss

Objective: To compare the effects of two satisfaction enhancement interventions for weight control on behavioral and weight changes among individuals in a 15‐month weight loss program. The primary hypothesis was that long‐term weight loss would be improved by an intervention that enhances perceived satisfaction with achieved outcomes. Research Methods and Procedures: Men and women (331) were randomized to weight control programs comprised of diet and exercise counseling and a cognitive intervention that emphasized either comparing experienced outcomes with expectation of ideal outcomes or comparing experienced outcomes with pretreatment status. The latter was expected to cause greater satisfaction with weight loss progress. Results: The intervention manipulation was not successful in influencing cognitions, satisfaction, or weight change. Discussion: The potential for intervening on satisfaction per se for the purpose of achieving greater or more sustained weight loss remains to be demonstrated.