Regression to the mean. A threat to exercise science?

Supervised exercise training in patients with cancer during anthracycline-based chemotherapy to mitigate cardiotoxicity: a randomized-controlled-trial

Background

Exercise training (ET) has been shown to mitigate cardiotoxicity of anthracycline-based chemotherapies (AC) in animal models. Data from randomized controlled trials in patients with cancer are sparse.

Methods

Patients with breast cancer or lymphoma receiving AC were recruited from four cancer centres and randomly assigned to 3 months supervised ET. Primary outcome was change in left ventricular global longitudinal strain (GLS) from baseline (before AC) to post AC (AC-end) compared between the EXduringAC group, who participated in an exercise intervention during AC including the provision of an activity tracker, and the control group EXpostAC, who received an activity tracker only. Secondary outcome parameters were changes in high sensitivity Troponin T (hsTnT), NT-pro-brain natriuretic peptide (NT-proBNP), peak oxygen consumption (peak VO2) and objectively measured physical activity (PA) during this same time-period. All assessments were repeated at a 12-week follow-up from AC-end, when also the EXpostAC group had completed the ET, that started after AC. In exploratory analyses, robust linear models were performed to assess the association of PA with changes in echocardiographic parameters and biomarkers of LV function.

Results

Fifty-seven patients (median age 47 years; 95% women) were randomized to EXduringAC (n = 28) and EXpostAC (n = 29) group. At AC-end, GLS deteriorated in both study groups (albeit insignificantly) with 7.4% and 1.0% in EXduringAC (n = 18) and EXpostAC (n = 18), respectively, and hsTnT and NT-proBNP significantly increased in both groups, without difference between groups for any parameter. Change in peak VO2 (-1.0 and -1.1 ml/kg/min) at AC-end was also similar between groups as was duration of moderate-to-vigorous PA (MVPA) with a median of 33 [26, 47] min/day and 32 [21, 59] min/day in the EXduringAC and EXpostAC group, respectively. In the robust linear model including the pooled patient population, MVPA was significantly associated with a more negative GLS and lesser increase in hsTnT at AC-end.

Conclusion

In this small scale RCT, supervised ET during AC was not superior to wearing a PA tracker to mitigate cardiotoxicity. The dose-response relationship between PA and cardioprotective effects during AC found in our and previous data supports the notion that PA should be recommended to patients undergoing AC.

Clinical Trial Registration

ClinicalTrials.gov, identifier NCT03850171.

Personalized redox biology: Designs and concepts

Personalized interventions are regarded as a next-generation approach in almost all fields of biomedicine, such as clinical medicine, exercise, nutrition and pharmacology. At the same time, an increasing body of evidence indicates that redox processes regulate, at least in part, multiple aspects of human physiology and pathology. As a result, the idea of applying personalized redox treatments to improve their efficacy has gained popularity among researchers in recent years. The aim of the present primer-style review was to highlight some crucial yet underappreciated methodological, statistical, and interpretative concepts within the redox biology literature, while also providing a physiology-oriented perspective on personalized redox biology. The topics addressed are: (i) the critical issue of investigating the potential existence of inter-individual variability; (ii) the importance of distinguishing a genuine and consistent response of a subject from a chance finding; (iii) the challenge of accurately quantifying the effect of a redox treatment when dealing with 'extreme' groups due to mathematical coupling and regression to the mean; and (iv) research designs and analyses that have been implemented in other fields, and can be reframed and exploited in a redox biology context.

Inter-individual variability in redox and performance responses after antioxidant supplementation: A randomized double blind crossover study

AIM

We aimed to investigate the inter-individual variability in redox and physiological responses of antioxidant-deficient subjects after antioxidant supplementation.

METHODS

Two hundred individuals were sorted by plasma vitamin C levels. A low vitamin C group (n = 22) and a control group (n = 22) were compared in terms of oxidative stress and performance. Subsequently, the low vitamin C group received for 30 days vitamin C (1 g) or placebo, in randomized, double-blind, crossover fashion, and the effects were examined through a mixed-effects model, while individual responses were calculated.

RESULTS

The low vitamin C group exhibited lower vitamin C (-25 μmol/L; 95%CI[-31.7, -18.3]; p < 0.001), higher F2 -isoprostanes (+17.1 pg/mL; 95%CI[6.5, 27.7]; p = 0.002), impaired VO2max (-8.2 mL/kg/min; 95%CI[-12.8, -3.6]; p < 0.001) and lower isometric peak torque (-41.5 Nm; 95%CI[-61.8, -21.2]; p < 0.001) compared to the control group. Regarding antioxidant supplementation, a significant treatment effect was found in vitamin C (+11.6 μmol/L; 95%CI[6.8, 17.1], p < 0.001), F2 -isoprostanes (-13.7 pg/mL; 95%CI[-18.9, -8.4], p < 0.001), VO2max (+5.4 mL/kg/min; 95%CI[2.7, 8.2], p = 0.001) and isometric peak torque (+18.7; 95%CI[11.8, 25.7 Nm], p < 0.001). The standard deviation for individual responses (SDir) was greater than the smallest worthwhile change (SWC) for all variables indicating meaningful inter-individual variability. When a minimal clinically important difference (MCID) was set, inter-individual variability remained for VO2max , but not for isometric peak torque.

CONCLUSION

The proportion of response was generally high after supplementation (82.9%-95.3%); however, a few participants did not benefit from the treatment. This underlines the potential need for personalized nutritional interventions in an exercise physiology context.

Effects of Arm-Crank Exercise on Fitness and Health in Adults With Chronic Spinal Cord Injury: A Systematic Review

Individuals with spinal cord injury (SCI) may benefit less from exercise training due to consequences of their injury, leading to lower cardiorespiratory fitness and higher risks of developing cardiovascular diseases. Arm-crank exercise (ACE) is the most common form of volitional aerobic exercise used by people with SCI outside a hospital. However, evidence regarding the specific effects of ACE alone on fitness and health in adults with SCI is currently lacking. Hence, this review aimed to determine the effects of ACE on cardiorespiratory fitness, body composition, cardiovascular disease (CVD) risk factors, motor function, health-related quality of life (QoL), and adverse events in adults with chronic SCI. Inclusion criteria were: inactive adults (≥18 years) with chronic SCI (>12 months post injury); used ACE alone as an intervention; measured at least one of the following outcomes; cardiorespiratory fitness, body composition, cardiovascular disease risk factors, motor function, health-related QoL, and adverse events. Evidence was synthesized and appraised using GRADE. Eighteen studies with a combined total of 235 participants having an injury between C4 to L3 were included. There was a moderate certainty of the body of evidence on ACE improving cardiorespiratory fitness. Exercise prescriptions from the included studies were 30-40 min of light to vigorous-intensity exercise, 3-5 times per week for 2-16 weeks. GRADE confidence ratings were very low for ACE improving body composition, CVD risks factors, motor function, or health-related QoL. No evidence suggests ACE increases the risk of developing shoulder pain or other injuries. Overall, this review recommends adults with chronic SCI should engage in regular ACE to improve cardiorespiratory fitness. More high-quality, larger-scale studies are needed to increase the level of evidence of ACE in improving cardiorespiratory fitness and to determine the effects of ACE on other outcomes. Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/display_reco rd.php?ID=CRD42021221952], identifier [CRD42021221952].

Causes and Consequences of Interindividual Response Variability: A Call to Apply a More Rigorous Research Design in Acute Exercise-Cognition Studies

The different responses of humans to an apparently equivalent stimulus are called interindividual response variability. This phenomenon has gained more and more attention in research in recent years. The research field of exercise-cognition has also taken up this topic, as shown by a growing number of studies published in the past decade. In this perspective article, we aim to prompt the progress of this research field by (i) discussing the causes and consequences of interindividual variability, (ii) critically examining published studies that have investigated interindividual variability of neurocognitive outcome parameters in response to acute physical exercises, and (iii) providing recommendations for future studies, based on our critical examination. The provided recommendations, which advocate for a more rigorous study design, are intended to help researchers in the field to design studies allowing them to draw robust conclusions. This, in turn, is very likely to foster the development of this research field and the practical application of the findings.

Thirty-two weeks of randomized interdisciplinary therapy or combined physical training promote similar improvements in anthropometric and biochemical parameters of obese women

BACKGROUND

Obesity is a multicausal illness that generates large expenses to health systems and also for the families of obese individuals. It is important to note that obesity disrupts all systems, generating metabolic consequences that may be irreversible. Interdisciplinary therapy is recommended as the primary method for treating obesity. However, the cost of interdisciplinary treatment can be high due to the need for various professionals, from different areas of expertise. This study compares the effects of 32 weeks of physical training combined with interdisciplinary therapy on anthropometric and biochemical parameters in obese women.

METHODS

Seventy-six subjects were randomized into two groups: Group Physical Exercise (EXE) and Group Interdisciplinary Treatment (INTER), being evaluated in the initial moment and after 32 weeks. 30 subjects completed the intervention and were evaluated (EXE: N.=13; INTER: N.=17).

RESULTS

Psychobiological and biochemical variables were measured. EXE and INTER were similar before treatment and both showed significantly improvements in anthropometric and biochemical parameters after interventions, without difference between groups.

CONCLUSIONS

The results confirmed the relevant role of physical training or the interdisciplinary therapy on metabolic profile of obese women. We realized that physical training can be incorporated into public or private health systems as an alternative strategy for obesity control, especially in locations that do not have the possibility of offering a complete interdisciplinary therapy.

Acute and Chronic Effects of Exercise on Continuous Glucose Monitoring Outcomes in Type 2 Diabetes: A Meta-Analysis

Objective: To examine the acute and chronic effects of structured exercise on glucose outcomes assessed by continuous glucose monitors in adults with type 2 diabetes. Methods: PubMed, Medline, EMBASE were searched up to January 2020 to identify studies prescribing structured exercise interventions with continuous glucose monitoring outcomes in adults with type 2 diabetes. Randomized controlled trials, crossover trials, and studies with pre- and post-designs were eligible. Short-term studies were defined as having exercise interventions lasting ≤2 weeks. Longer-term studies were defined as >2 weeks. Results: A total of 28 studies were included. Of these, 23 studies were short-term exercise interventions. For all short-term studies, the same participants completed a control condition as well as at least one exercise condition. Compared to the control condition, exercise decreased the primary outcome of mean 24-h glucose concentrations in short-term studies (-0.5 mmol/L, [-0.7, -0.3]; p < 0.001). In longer-term studies, mean 24-h glucose was not significantly reduced compared to control (-0.9 mmol/L [-2.2, 0.3], p = 0.14) but was reduced compared to pre-exercise values (-0.5 mmol/L, [-0.7 to -0.2] p < 0.001). The amount of time spent in hyperglycemia and indices of glycemic variability, but not fasting glucose, also improved following short-term exercise. Among the shorter-term studies, subgroup, and regression analyses suggested that the timing of exercise and sex of participants explained some of the heterogeneity among trials. Conclusion: Both acute and chronic exercise can improve 24-h glucose profiles in adults with type 2 diabetes. The timing of exercise and sex of participants are among the factors that may explain part of the heterogeneity in acute glycemic improvements following exercise.

An Investigation of Short-Term Longitudinal Associations Between Handgrip Strength and Cardiovascular Disease Biomarkers Among Middle-Aged to Older Adults: A Project FRONTIER Study

The purpose of this study was to examine short-term longitudinal relationships between handgrip strength (HGS) and cardiovascular disease (CVD) biomarkers in middle-aged to older adults living in rural areas (N = 138). The association between HGS and CVD biomarkers was examined at baseline, with HGS as a predictor of the annual change in biomarkers, and in a parallel fashion between the annual change in HGS and CVD biomarkers over an average of 2.8 follow-up years. The results showed HGS to cross-sectionally associate with waist circumference and diastolic blood pressure at baseline, but HGS at baseline was not found to predict the annual change in any biomarker. The annual increase in HGS was significantly associated with favorable changes in high-density lipoprotein cholesterol, triglycerides, and systolic/diastolic blood pressures; yet, these associations varied by the baseline levels of biomarkers. The present findings suggest that improved muscle strength with aging is related to favorable changes in CVD biomarkers.

Recruitment and inclusion procedures as "pain killers" in clinical trials?

Background

Recruitment and inclusion procedures in clinical trials are time critical. This holds particularly true for studies investigating patients with fluctuating symptom patterns, like those with chronic neck pain. In a feasibility study on neck pain, we found a clinically relevant decrease in pain ratings within the recruitment period. This paper analyses the phenomenon and gives recommendations for recruitment procedures in clinical trials on pain.

Methods

Changes in pain intensity scores of 44 chronic neck pain patients (6 males and 36 females; mean age: 45.3±13.2 years) between the first telephone contact and baseline assessment were analyzed. Inclusion criterion was a mean pain intensity of ≥40 on a 0-100 numerical rating scale during the last three months. Statistical analyses were performed using ANOVA and parametric/non-parametric correlation coefficients.

Results

Average pain intensity score decreased significantly from 60.3±13.3 at telephone interview to 38.1±21.7 at baseline assessment. This represents a relative change of 36.8%. A weak but significant negative correlation was found between number of days between assessments and pain rating differences. There was a positive correlation between change of pain intensity and the pain level at the first contact, indicating that the decreased pain ratings over time were also dependent on the initial pain rating.

Conclusions

The clinically significant changes in pain intensity were weakly related to waiting time and moderately dependent on initial pain intensity, suggesting regression to the mean. The natural course of the disease and the Hawthorne effect are also discussed as contributing factors.

Antioxidants in Personalized Nutrition and Exercise

The present review highlights the idea that antioxidant supplementation can be optimized when tailored to the precise antioxidant status of each individual. A novel methodologic approach involving personalized nutrition, the mechanisms by which antioxidant status regulates human metabolism and performance, and similarities between antioxidants and other nutritional supplements are described. The usefulness of higher-level phenotypes for data-driven personalized treatments is also explained. We conclude that personally tailored antioxidant interventions based on specific antioxidant inadequacies or deficiencies could result in improved exercise performance accompanied by consistent alterations in redox profile.

N-acetylcysteine supplementation increases exercise performance and reduces oxidative stress only in individuals with low levels of glutathione

Most of the evidence indicates that chronic antioxidant supplementation induces negative effects in healthy individuals. However, it is currently unknown whether specific redox deficiencies exist and whether targeted antioxidant interventions in deficient individuals can induce positive effects. We hypothesized that the effectiveness of antioxidant supplements to decrease oxidative stress and promote exercise performance depends on the redox status of the individuals that receive the antioxidant treatment. To this aim, we investigated whether N-acetylcysteine (NAC) supplementation would enhance exercise performance by increasing glutathione concentration and by reducing oxidative stress only in individuals with low resting levels of glutathione. We screened 100 individuals for glutathione levels and formed three groups with low, moderate and high levels (N = 36, 12 per group). After by-passing the regression to the mean artifact, by performing a second glutathione measurement, the individuals were supplemented with NAC (2 × 600mg, twice daily, for 30 days) or placebo using a double-blind cross-over design. We performed three whole-body performance tests (VO₂max, time trial and Wingate), measured two systemic oxidative stress biomarkers (F₂-isoprostanes and protein carbonyls) and assessed glutathione-dependent redox metabolism in erythrocytes (glutathione, glutathione peroxidase, glutathione reductase, superoxide dismutase, catalase and NADPH). The low glutathione group improved after NAC supplementation in VO₂max, time trial and Wingate by 13.6%, 15.4% and 11.4%, respectively. Thirty days of NAC supplementation were sufficient to restore baseline glutathione concentration, reduce systemic oxidative stress and improve erythrocyte glutathione metabolism in the low glutathione group. On the contrary, the 30-day supplementation period did not affect performance and redox state of the moderate and high glutathione groups, although few both beneficial and detrimental effects in performance were observed. In conclusion, individuals with low glutathione levels were linked with decreased physical performance, increased oxidative stress and impaired redox metabolism of erythrocytes. NAC supplementation restored both performance and redox homeostasis.

Adaptations to endurance training depend on exercise-induced oxidative stress: exploiting redox interindividual variability

AIM

The aim of this study was to reveal the role of reactive oxygen and nitrogen species (RONS) in exercise adaptations under physiological in vivo conditions and without the interference from other exogenous redox agents (e.g. a pro-oxidant or antioxidant).

METHODS

We invented a novel methodological set-up that exploited the large redox interindividual variability in exercise responses. More specifically, we used exercise-induced oxidative stress as the 'classifier' measure (i.e. low, moderate and high) and investigated the physiological and redox adaptations after a 6-week endurance training protocol.

RESULTS

We demonstrated that the group with the low exercise-induced oxidative stress exhibited the lowest improvements in a battery of classic adaptations to endurance training (VO₂ max, time trial and Wingate test) as well as in a set of redox biomarkers (oxidative stress biomarkers and antioxidants), compared to the high and moderate oxidative stress groups.

CONCLUSION

The findings of this study substantiate, for the first time in a human in vivo physiological context, and in the absence of any exogenous redox manipulation, the vital role of RONS produced during exercise in adaptations. The stratification approach, based on a redox phenotype, implemented in this study could be a useful experimental strategy to reveal the role of RONS and antioxidants in other biological manifestations as well.

Using register data to estimate causal effects of interventions: An ex post synthetic control-group approach

AIMS

It is common in the context of evaluations that participants have not been selected on the basis of transparent participation criteria, and researchers and evaluators many times have to make do with observational data to estimate effects of job training programs and similar interventions. The techniques developed by researchers in such endeavours are useful not only to researchers narrowly focused on evaluations, but also to social and population science more generally, as observational data overwhelmingly are the norm, and the endogeneity challenges encountered in the estimation of causal effects with such data are not trivial. The aim of this article is to illustrate how register data can be used strategically to evaluate programs and interventions and to estimate causal effects of participation in these.

METHODS

We use propensity score matching on pretreatment-period variables to derive a synthetic control group, and we use this group as a comparison to estimate the employment-treatment effect of participation in a large job-training program.

RESULTS

We find the effect of treatment to be small and positive but transient.

CONCLUSIONS

Our method reveals a strong regression to the mean effect, extremely easy to interpret as a treatment effect had a less advanced design been used (e.g. a within-subjects panel data analysis), and illustrates one of the unique advantages of using population register data for research purposes.

Changes in objectively measured physical activity in adolescents with Down syndrome: the UP&DOWN longitudinal study

BACKGROUND

It is a priority to understand that physical activity behaviour over time is a priority in Down syndrome population in order to design and promote succesfull interventions to maintain or increase levels of physical activity. We aimed to study 1 and 2-year changes in objectively measured physical activity among a relatively large sample of adolescents with Down syndrome.

METHODS

This study comprised a total of 99 adolescents with Down syndrome (38 girls) aged from 11 to 20 years old at baseline. Participants with valid accelerometer data at baseline and at least one of the follow-up visits were included in the analysis.

RESULTS

Overall, levels of physical activity observed in adolescents with Down syndrome declined from baseline to follow-ups, but these changes were not significant (all P > 0.05). Moderate-to-moderately high tracking of physical activity was observed in adolescents with Down syndrome (all P < 0.001). Youths who met physical activity guidelines at baseline demonstrated a greater decline in physical activity in 1 and 2-year changes (P < 0.05), although they were also more likely to meet physical activity guidelines at 1 and 2-year follow-ups (P < 0.05).

CONCLUSIONS

Adolescents with Down syndrome do not change their levels of physical activity at 2-year follow-ups, but those who met physical activity guidelines presented stronger declines in physical activity over time.

Experimental verification of regression to the mean in redox biology: differential responses to exercise

An important methodological threat when selecting individuals based on initial values for a given trait is the "regression to the mean" artifact. This artifact appears when a group with an extreme mean value during a first measurement tends to obtain a less extreme value (i.e. tends toward the mean) on a subsequent measurement. The main aim was to experimentally confirm the presence of this artifact in the responses of the reference oxidative stress biomarker (F₂-isoprostanes) after exercise. Urine samples were collected before and immediately following acute exercise in order to determine the level of exercise-induced oxidative stress. Afterwards, participants were arranged into three groups based on their levels of exercise-induced oxidative stress (low, moderate and high oxidative stress groups; n = 12 per group). In order to verify the existence of the regression to the mean artifact, the three groups were subjected to a second exercise trial one week after the first trial. This study confirmed the regression to the mean artifact in a redox biology context and showed that this artifact can be minimized by performing a duplicate pretreatment measurement after completing a nonrandom sorting based on the first assessment. This study also indicated that different individuals experience high oxidative stress or reductive stress (or no stress) to the same exercise stimulus even after adjusting for regression to the mean. This finding substantiates the methodological choice to divide individuals based on their degree of exercise-induced oxidative stress in future experiments to investigate the role of reactive species in exercise adaptations.

The Effect of Atorvastatin on Habitual Physical Activity among Healthy Adults

PURPOSE

Statin therapy can result in muscle pain, cramps, and weakness that may limit physical activity, although reports are mixed. We conducted a randomized control trial to examine the effect of atorvastatin on habitual physical activity levels in a large sample of healthy adults.

METHODS

Participants (n = 418) were statin-naive adults (44.0 ± 16.1 yr (mean ± SD)) who were randomized and double-blinded to 80 mg · d(-1) of atorvastatin or placebo for 6 months. Accelerometers were worn for 96 h before and after drug treatment. Repeated-measures analysis tested physical activity levels after versus those before drug treatment among groups with age and VO2max as covariates.

RESULTS

In the total sample, sedentary behavior increased (19.5 ± 5.1 min · d(-1)), whereas light-intensity (9.1 ± 3.0 min · d(-1)) and moderate-intensity (9.7 ± 2.8 min · d(-1)) physical activity decreased, as did total activity counts (17.8 ± 6.3 d × 10(-3)) over 6 months (P < 0.01), with no differences between groups. The atorvastatin group increased sedentary behavior (19.8 ± 7.4 min · d(-1)) and decreased light-intensity (10.7 ± 4.3 min · d(-1)) and moderate-intensity (8.5 ± 4.0 min · d(-1)) physical activity (P < 0.05). On the other hand, the placebo group increased sedentary behavior (19.2 ± 7.1 min · d(-1)) and decreased moderate-intensity (11.0 ± 3.8 min · d(-1)) and total physical activity counts (-23.8 ± 8.8 × 10(-3) d(-1)) (P < 0.05).

CONCLUSIONS

Time being sedentary increased and physical activity levels decreased in the total sample over 6 months of drug treatment, independent of group assignment. Our results suggest that statins do not influence physical activity levels any differently from placebo, and the lack of inclusion of a placebo condition may provide insight into inconsistencies in the literature.

The use of shear rate-diameter dose-response curves as an alternative to the flow-mediated dilation test

The brachial artery flow-mediated dilation test (FMD) is the non-invasive gold-standard used to test endothelial function. Reduced FMD precedes the development of atherosclerosis and provides an early marker for predicting future cardiovascular disease events. Although, this test is of high potential, it is somewhat limited by poor reproducibility. By utilizing hand warming and grip exercise combined with hierarchical linear modeling, shear rate-diameter dose-response curves may provide a novel and more accurate way to assess endothelial function in humans. Shear rate-diameter dose-response curves could potentially improve upon the traditional FMD measurement and serve as a superior clinical and research tool for assessing cardiovascular disease risk in a variety of populations. The current paper presents testable hypotheses and methodology for assessing the validity and reliability of an alternative to the current FMD test.

The relationship between the blood pressure responses to exercise following training and detraining periods

BACKGROUND

Exercise training lowers blood pressure (BP), while BP increases and returns to pre-training values with detraining. Yet, there is considerable variability in these BP responses. We examined the relationship between the BP responses after 6 months of training followed by 2 weeks of detraining among the same people.

METHODOLOGY/PRINCIPAL FINDINGS

Subjects (n = 75) (X+SD, 50.2 ± 10.6 yr) were sedentary, obese, and had prehypertension. They completed an aerobic (n = 34); resistance (n = 28); or aerobic + resistance or concurrent (n = 13) exercise training program. We calculated a metabolic syndrome z score (MetSz). Subjects were classified as BP responders (BP decreased) or non-responders (BP increased) to training and detraining. Linear and multivariable regression tested the BP response. Chi Square tested the frequency of responders and non-responders. The systolic BP (SBP, r =  -0.474) and diastolic (DBP, r =  -0.540) response to training negatively correlated with detraining (p<0.01), independent of modality (p>0.05). Exercise responders reduced SBP 11.5 ± 7.8 (n = 29) and DBP 9.8 ± 6.2 mmHg (n = 31); non-responders increased SBP 7.9.± 10.9 (n = 46) and DBP 4.9 ± 7.1 mmHg (n = 44) (p<0.001). We found 65.5% of SBP training responders were SBP detraining non-responders; while 60.9% of SBP training non-responders were SBP detraining responders (p = 0.034). Similarly, 80.6% of DBP training responders were DBP detraining non-responders; while 59.1% of DBP training non-responders were DBP detraining responders (p<0.001). The SBP detraining response (r =  -0.521), resting SBP (r =  -0.444), and MetSz (r = 0.288) explained 44.8% of the SBP training response (p<0.001). The DBP detraining response (r =  -0.553), resting DBP (r =  -0.450), and MetSz (r = 0.463) explained 60.1% of the DBP training response (p<0.001).

CONCLUSIONS/SIGNIFICANCE

As expected most subjects that decreased BP after exercise training, increased BP after detraining. An unanticipated finding was most subjects that increased BP after exercise training, decreased BP after detraining. Reasons why the negative effects of exercise training on BP maybe reversed with detraining among some people should be explored further.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov 1R01HL57354; 2003-2008; NCT00275145.

Effect of a telephone-delivered coronary heart disease secondary prevention program (proactive heart) on quality of life and health behaviours: primary outcomes of a randomised controlled trial

BACKGROUND

Participation in coronary heart disease secondary prevention programs is low. Innovative programs to meet this treatment gap are required.

PURPOSE

To aim of this study is to describe the effectiveness of a telephone-delivered secondary prevention program for myocardial infarction patients.

METHODS

Four hundred and thirty adult myocardial infarction patients in Brisbane, Australia were randomised to a 6-month secondary prevention program or usual care. Primary outcomes were health-related quality of life (Short Form-36) and physical activity (Active Australia Survey).

RESULTS

Significant intervention effects were observed for health-related quality of life on the mental component summary score (p = 0.02), and the social functioning (p = 0.04) and role-emotional (p = 0.03) subscales, compared with usual care. Intervention participants were also more likely to meet recommended levels of physical activity (p = 0.02), body mass index (p = 0.05), vegetable intake (p = 0.04) and alcohol consumption (p = 0.05).

CONCLUSIONS

Telephone-delivered secondary prevention programs can significantly improve health outcomes and could meet the treatment gap for myocardial infarction patients.

The isotopic composition and insect content of diet predict tissue isotopic values in a South American passerine assemblage

We analyzed the carbon and nitrogen isotopic values of the muscle, liver, and crop contents ("diet") of 132 individuals of 16 species of Chilean birds. The nitrogen content of diet was tightly correlated with the fraction of gut contents represented by insects relative to plant material. The carbon and nitrogen isotopic values of diet, liver, and muscle were all linearly correlated, implying high temporal consistency in the isotopic value of the diet of these birds. However, δ(15)N was not significantly related with the percentage of insects in diet. These results cast doubt on the applicability of the use of (15)N enrichment to diagnose trophic level in, at least some, terrestrial ecosystems. However, the residuals of the relationship relating the isotopic value of bird tissues with those of their diet were weakly negatively correlated with insect intake. We hypothesize that this negative correlation stems from the higher quality of protein found in insects relative to that of plant materials. Finally, our data corroborated a perplexing and controversial negative relationship between tissue to diet isotopic discrimination and the isotopic value of diet. We suggest that this relationship is an example of the commonly observed regression to the mean effect that plagues many scientific studies.

Dissection of the factors driving the placebo effect in hypnotic treatment of depressed insomniacs

OBJECTIVES

Our prior work has shown that there is improvement in self-reported sleep in persons receiving placebo in hypnotic clinical trials. We examined the components of the "placebo response" in a hypnotic clinical trial.

METHODS

This was an exploratory analysis of a randomized, double-blind clinical trial of eszopiclone versus placebo in the treatment of persons with depression and insomnia who were also receiving fluoxetine at a clinic of a teaching hospital. Sixty adults with both depression and insomnia symptoms, who were free of significant primary sleep disorders, received open-label fluoxetine for 9weeks. Patients were further randomized 1:1 to receive either masked eszopiclone 3mg or placebo at bedtime after the first week of fluoxetine. We examined the respective contributions of three factors associated with the "placebo effect": (1) regression to the mean, (2) expectancy, and (3) social desirability.

RESULTS

There was evidence for regression to the mean for the continuous measurement of the Insomnia Severity Index (ISI) and the Hamilton Depression Rating Scale. There was evidence for expectancy in self-reported Wake After Sleep Onset, continuous measurement of ISI, and dichotomous remission/non-remitter measurement of ISI. There was evidence of social desirability affecting self-reported Total Sleep Time.

CONCLUSIONS

Factors that have been associated with the "placebo effect" are operating in hypnotic clinical trials. However, the role of each factor differs depending upon which self-reported variable is being considered. The findings have implications for clinical trial design in insomnia.

Characteristics of control group participants who increased their physical activity in a cluster-randomized lifestyle intervention trial

BACKGROUND

Meaningful improvement in physical activity among control group participants in lifestyle intervention trials is not an uncommon finding, and may be partly explained by participant characteristics. This study investigated which baseline demographic, health and behavioural characteristics were predictive of successful improvement in physical activity in usual care group participants recruited into a telephone-delivered physical activity and diet intervention trial, and descriptively compared these characteristics with those that were predictive of improvement among intervention group participants.

METHODS

Data come from the Logan Healthy Living Program, a primary care-based, cluster-randomized controlled trial of a physical activity and diet intervention. Multivariable logistic regression models examined variables predictive of an improvement of at least 60 minutes per week of moderate-to-vigorous intensity physical activity among usual care (n = 166) and intervention group (n = 175) participants.

RESULTS

Baseline variables predictive of a meaningful change in physical activity were different for the usual care and intervention groups. Being retired and completing secondary school (but no further education) were predictive of physical activity improvement for usual care group participants, whereas only baseline level of physical activity was predictive of improvement for intervention group participants. Higher body mass index and being unmarried may also be predictors of physical activity improvement for usual care participants.

CONCLUSION

This is the first study to examine differences in predictors of physical activity improvement between intervention group and control group participants enrolled in a physical activity intervention trial. While further empirical research is necessary to confirm findings, results suggest that participants with certain socio-demographic characteristics may respond favourably to minimal intensity interventions akin to the treatment delivered to participants in a usual care group. In future physical activity intervention trials, it may be possible to screen participants for baseline characteristics in order to target minimal-intensity interventions to those most likely to benefit. (Australian Clinical Trials Registry, http://www.anzctr.org.au/default.aspx, ACTRN012607000195459).

The John Sutton memorial lecture, 2009. Conductance systems: an integrative approach to the physiology of extreme conditions

This presentation explores the value of mechanical, electrical, and mathematical analogues in understanding and evaluating a variety of closely integrated transport processes in human biology. Particular attention is directed to a major interest of John Sutton: the factors limiting transport of oxygen from the atmosphere to the working muscles when exercising in a variety of hostile environments. In most circumstances, the limiting term in a closely linked chain of conductances seems to be in the blood stream, and its magnitude can be estimated by measurements of maximal oxygen intake. Despite recent criticisms of this index by those who have proposed a feed-forward control of maximal aerobic effort, conductance theory suggests that the main limitation of oxygen transport is normally maximal cardiac output. Therefore, careful laboratory determinations of maximal oxygen intake continue to provide a convenient integrating assessment of an individual’s cardiorespiratory function, with many important applications in sports medicine and exercise science.

Occasional cigarette smoking chronically affects arterial function

Cigarette smoking is associated with impaired arterial function as measured by reduced vasodilation in response to reactive hyperemia. However, previous studies did not account for potential differences in shear stimuli. The purpose of this study was to use young, occasional smokers to ethically evaluate the effects of acute and chronic smoking on shear rate-diameter dose-response slopes. Young (20 to 26-y-old) nonsmokers (n = 9) and occasional (<1 pack/week) smokers were tested (n = 9). Smokers were tested after abstaining for 2 or more d and then immediately after smoking two cigarettes. Shear rate was manipulated using five upstream ischemic durations (0.5, 1, 2, 5 and 10 min). Radial artery blood velocities and diameters were assessed using Doppler ultrasound. Hierarchical linear modeling (HLM) was used to estimate change in diameter using repeated measures of shear rate nested within each subject. The shear rate-diameter slope was reduced by 35.9% in occasional smokers compared with nonsmoking controls (beta = 2.78(10-4) versus 1.78(10-4), p = 0.004). Acute smoking further attenuated the shear rate-diameter slope (i.e., arterial function) by 23.8% (beta = 1.79(10-4) versus 1.36(10-4), p = 0.037). These results suggest that repeated bouts of occasional cigarette smoking can chronically attenuate arterial function in otherwise healthy, young persons.

Correcting for regression to the mean in behavior and ecology

If two successive trait measurements have a less-than-perfect correlation, individuals or populations will, on average, tend to be closer to the mean on the second measurement (the so-called regression effect). Thus, there is a negative correlation between an individual's state at time 1 and the change in state from time 1 to time 2. In addition, whenever groups differ in their initial mean values, the expected change in the mean value from time 1 to time 2 will differ among the groups. For example, birds feeding nestlings lose weight, but initially heavier birds lose more weight than lighter birds, a result expected from the regression effect. In sexual selection, males who remain unmated in the first year are, on average, less attractive than mated males. The regression effect predicts that these males will increase their attractiveness in the second year more than mated males. In well-designed experiments, changes in the experimental and control groups would be compared. In observational studies, however, no such comparison is available, and expected differential effects must be accounted for before they can be attributed to external causes. We describe methods to correct for the regression effect and assess alternative causal explanations.

Placebo effects in primary insomnia

Placebo effects are commonly observed in insomnia clinical trials. With the advent of longer-term trials, such effects appear to be remarkably robust and durable. In this paper we review the classic factors that are believed to contribute to placebo effects and how these factors operate in insomnia randomized clinical trials. Beyond this we suggest that the episodic nature of insomnia may interact with patient preferences for intermittent dosing in such a way as to sustain placebo effects in the long term. An appreciation of the latter phenomenon may provide increased power to detect therapeutic outcomes and may be used to potentiate clinical gains.