Treadmill walking economy is not affected by body fat and body mass index in adults

To determine whether body fat and body mass index (BMI) affect the energy cost of walking (Cw; J/kg/m), ventilation, and gas exchange data from 205 adults (115 females; percent body fat range = 3.0%-52.8%; BMI range = 17.5-43.2 kg/m2) were obtained at rest and during treadmill walking at 1.34 m/s to calculate gross and net Cw. Linear regression was used to assess relationships between body composition indices, Cw, and standing metabolic rate (SMR). Unpaired t-tests were used to assess differences between sex, and one-way ANOVA was used to assess differences by BMI categories: normal weight, <25.0 kg/m2; overweight, 25.0-29.9 km/m2; and obese, ≥30 kg/m2. Net Cw was not related to body fat percent, fat mass, or BMI (all R2 ≤ 0.011). Furthermore, mean net Cw was similar by sex (male: 2.19 ± 0.30 J/kg/m; female: 2.24 ± 0.37 J/kg/m, p = 0.35) and across BMI categories (normal weight: 2.23 ± 0.36 J/kg/m; overweight: 2.18 ± 0.33 J/kg/m; obese: 2.26 ± 0.31, p = 0.54). Gross Cw and SMR were inversely associated with percent body fat, fat mass, and BMI (all R2 between 0.033 and 0.270; all p ≤ 0.008). In conclusion, Net Cw is not influenced by body fat percentage, total body fat, and BMI and does not differ by sex.

The Biological Basis of Sex Differences in Athletic Performance: Consensus Statement for the American College of Sports Medicine

ABSTRACT

Biological sex is a primary determinant of athletic performance because of fundamental sex differences in anatomy and physiology dictated by sex chromosomes and sex hormones. Adult men are typically stronger, more powerful, and faster than women of similar age and training status. Thus, for athletic events and sports relying on endurance, muscle strength, speed, and power, males typically outperform females by 10%-30% depending on the requirements of the event. These sex differences in performance emerge with the onset of puberty and coincide with the increase in endogenous sex steroid hormones, in particular testosterone in males, which increases 30-fold by adulthood, but remains low in females. The primary goal of this consensus statement is to provide the latest scientific knowledge and mechanisms for the sex differences in athletic performance. This review highlights the differences in anatomy and physiology between males and females that are primary determinants of the sex differences in athletic performance and in response to exercise training, and the role of sex steroid hormones (particularly testosterone and estradiol). We also identify historical and nonphysiological factors that influence the sex differences in performance. Finally, we identify gaps in the knowledge of sex differences in athletic performance and the underlying mechanisms, providing substantial opportunities for high-impact studies. A major step toward closing the knowledge gap is to include more and equitable numbers of women to that of men in mechanistic studies that determine any of the sex differences in response to an acute bout of exercise, exercise training, and athletic performance.

Quantifying the benefits of inefficient walking: Monty Python inspired laboratory based experimental study

OBJECTIVE

To compare the rate of energy expenditure of low efficiency walking with high efficiency walking.

DESIGN

Laboratory based experimental study.

SETTING

United States.

PARTICIPANTS

13 healthy adults (six women, seven men) with no known gait disorder, mean (±standard deviation) age 34.2±16.1 years, height 174.2±12.6 cm, weight 78.2±22.5 kg, and body mass index 25.6±6.0.

INTERVENTION

Participants performed three, five minute walking trials around an indoor 30 m course. The first trial consisted of walking at a freely chosen walking speed in the participant's usual style. The next two trials consisted of low efficiency walks in which participants were asked to duplicate the walks of Mr Teabag and Mr Putey (acted by John Cleese and Michael Palin, respectively) in the legendary Monty Python Ministry of Silly Walks (MoSW) skit that first aired in 1970. Distance covered during the five minute walks was used to calculate average speed. Ventilation and gas exchange were collected throughout to determine oxygen uptake (V̇O₂; mL O₂/kg/min) and energy expenditure (EE; kcal/kg/min; 1 kcal=4.18 kJ), reported as mean±standard deviation.

MAIN OUTCOME MEASURES

V̇O₂ and EE.

RESULTS

V̇O₂ and EE were about 2.5 times higher (P<0.001) during the Teabag walk compared with participants' usual walk (27.9±4.8 v 11.3±1.9 mL O₂/kg/min; 0.14±0.03 v 0.06±0.01 kcal/kg/min), but were not different during the Putey walk (12.3±1.8 mL/kg/min; 0.06±0.01 kcal/kg/min). Each minute of Teabag walking increased EE over participants' usual walking by an average of 8.0 kcal (range 5.5-12.0) in men and by 5.2 kcal (range 3.9-6.2) in women, and qualified as vigorous intensity physical activity (>6 resting metabolic equivalents).

CONCLUSIONS

For adults with no known gait disorder who average approximately 5000 steps/day, exchanging about 22%-34% of their daily steps with higher energy, low efficiency walking in Teabag style-requiring around 12-19 min-could increase daily EE by 100 kcal. Adults could achieve 75 minutes of vigorous intensity physical activity per week by walking inefficiently for about 11 min/day. Had an initiative to promote inefficient movement been adopted in the early 1970s, we might now be living among a healthier society. Efforts to promote higher energy-and perhaps more joyful-walking should ensure inclusivity and inefficiency for all.

Force plate vertical jump scans are not a valid proxy for physical fitness in US special warfare trainees

Background: The United States Air Force Special Warfare Training Wing (SWTW) administers a comprehensive physical fitness test to active duty Airmen entering the Special Warfare training pipeline. The Sparta Science™ system utilizes proprietary software to analyze the force-time curve of a vertical jump and purports to serve as a proxy for traditional military fitness tests. The Sparta Science™ system produces four proprietary metrics, including the Sparta™ Score, which is correlated to high magnitudes of force production purportedly performance. This study investigated how Sparta™ Jump Scans correlate to components of a physical fitness test utilized within the SW training pipeline. Methods: At the entry and exit of an 8-week Special Warfare Training Wing preparatory course (SW PREP), 643 trainees completed both an initial and final Sparta™ Jump Scan and a Candidate Fitness Test (CFT). The Candidate Fitness Test consists of eight components and tests several different domains of fitness including strength, power, muscular endurance, swimming proficiency, and cardiovascular fitness. Paired t-tests were used to determine if Sparta™ Jump Scan metrics and CFT components changed during SW PREP. Sparta™ Score's correlation was assessed against every other Sparta™ Jump Scan metric and all CFT fitness measures. Results: This study found that the Sparta™ Jump Scan metrics decline slightly over SW PREP (p < 0.05; negligible-small effect size), while most CFT measures improve (p < 0.05; small-medium effect size). Changes in Sparta™ Jump Scan metrics did not reflect the changes in CFT performance over SW PREP (r ²: 0.00-0.03). Conclusion: The Sparta™ Score was not correlated to the most tactically-relevant fitness measures (rucking and swimming), and only weakly correlated with the only jumping measure on the fitness test, the standing broad jump.

The Use of Force Plate Vertical Jump Scans to Identify Special Warfare Trainees at Risk for Musculoskeletal Injury: A Large Cohort Study

BACKGROUND

Vertical jump scans from commercially available force plate systems are increasingly used in military settings to screen for musculoskeletal injury (MSKI) risk. However, to date, no studies have determined the ability of these tools to identify tactical athletes at elevated risk for MSKI.

PURPOSE

To (1) determine associations between scores from a force plate vertical jump test and the likelihood of experiencing an MSKI and to (2) establish the test-retest reliability of the output scores from the force plate system used.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 823 male Air Force Special Warfare trainees underwent force plate vertical jump screenings before entering an 8-week training course at US Air Force Special Warfare Training Wing. MSKI data were collected for the 8-week surveillance period for each trainee. Logistic regression analyses were used to identify associations between baseline force plate jump scores and the likelihood of MSKI (any region) or a lower extremity MSKI (significance level, P = .05). The test-retest portion of the study collected force plate output scores from 12 trainees performing 3 trials of the standard test procedures. The reliability of 5 output scores was assessed with intraclass correlation coefficients (ICCs) using a single rater.

RESULTS

All force plate output scores demonstrated excellent test-retest reliability (ICC >0.90). Overall 308 (36.4%) trainees had an MSKI during the surveillance period. However, no significant associations were found between the proprietary force plate vertical jump scan output scores and the likelihood of experiencing either an MSKI or a lower extremity MSKI.

CONCLUSION

Output scores from this commercially available force plate system did not identify Air Force Special Warfare trainees at elevated risk of experiencing an MSKI.

A New Carbohydrate Food Quality Scoring System to Reflect Dietary Guidelines: An Expert Panel Report

Existing metrics of carbohydrate food quality have been based, for the most part, on favorable fiber- and free sugar-to-carbohydrate ratios. In these metrics, higher nutritional quality carbohydrate foods are defined as those with >10% fiber and <10% free sugar per 100 g carbohydrate. Although fiber- and sugar-based metrics may help to differentiate the nutritional quality of various types of grain products, they may not aptly capture the nutritional quality of other healthy carbohydrate foods, including beans, legumes, vegetables, and fruits. Carbohydrate food quality metrics need to be applicable across these diverse food groups. This report introduces a new carbohydrate food scoring system known as a Carbohydrate Food Quality Score (CFQS), which supplements the fiber and free sugar components of previous metrics with additional dietary components of public health concern (e.g., sodium, potassium, and whole grains) as identified by the Dietary Guidelines for Americans. Two CFQS models are developed and tested in this study: one that includes four dietary components (CFQS-4: fiber, free sugars, sodium, potassium) and one that considers five dietary components (CFQS-5: fiber, free sugars, sodium, potassium, and whole grains). These models are applied to 2596 carbohydrate foods in the Food and Nutrient Database for Dietary Studies (FNDDS) 2017−2018. Consistent with past studies, the new carbohydrate food scoring system places large percentages of beans, vegetables, and fruits among the top scoring carbohydrate foods. The whole grain component, which only applies to grain foods (N = 1561), identifies ready-to-eat cereals, oatmeal, other cooked cereals, and selected whole grain breads and crackers as higher-quality carbohydrate foods. The new carbohydrate food scoring system shows a high correlation with the Nutrient Rich Food (NRF9.3) index and the Nutri-Score. Metrics of carbohydrate food quality that incorporate whole grains, potassium, and sodium, in addition to sugar and fiber, are strategically aligned with multiple 2020−2025 dietary recommendations and may therefore help with the implementation of present and future dietary guidelines.

Postexercise Hypotension Is Delayed in Men With Obesity and Hypertension

Background

Postexercise hypotension (PEH) can play a major role in the daily blood pressure management among individuals with hypertension. However, there are limited data on PEH in persons with obesity and hypertension, and no PEH data in this population beyond 90 min postexercise.

Purpose

The purpose of this study was to determine if PEH could be elicited in men with obesity and hypertension during a 4-h postexercise measurement period.

Methods

Seven men [age = 28 ± 4 years; body mass index = 34.6 ± 4.8 kg/m²; brachial systolic blood pressure (SBP): 138 ± 4 mmHg; brachial diastolic BP (DBP): 80 ± 5 mmHg; central SBP: 125 ± 4 mmHg; central DBP: 81 ± 8 mmHg] performed two exercise sessions on a cycle ergometer, each on a separate day, for 45 min at ∼65% VO_2max. One exercise session was performed at a cadence of 45 RPM and one at 90 RPM. Blood pressure was monitored with a SunTech Oscar2 ambulatory blood pressure monitor for 4 h after both exercise sessions, and during a time-matched control condition.

Results

Both brachial and central SBP were not changed during the first h postexercise but were reduced by ∼5-11 mmHg between 2 and 4 h postexercise (p < 0.05) after both exercise sessions. Brachial and central DBP were elevated by ∼5 mmHg at 1 h postexercise (p < 0.05) but were ∼2-3 mmHg lower compared to control at 4 h postexercise, and ∼2-4 mmHg lower at 3 h postexercise compared to baseline. Mean arterial pressure (MAP) was elevated compared to control at 1 h postexercise after both exercise sessions, but was ∼2-3 mmHg lower compared to control at 2, 3, and 4 h postexercise, and ∼4-7 mmHg lower at 3 h postexercise compared to baseline.

Conclusion

Despite the small sample size and preliminary nature of our results, we conclude that PEH is delayed in men with obesity and hypertension, but the magnitude and duration of PEH up to 4 h postexercise is similar to that reported in the literature for men without obesity and hypertension. The PEH is most pronounced for brachial and central SBP and MAP. The virtually identical pattern of PEH after both exercise trials indicates that the delayed PEH is a reproducible finding in men with obesity and hypertension.

Adaptive Goals and Reinforcement Timing to Increase Physical Activity in Adults: A Factorial Randomized Trial

INTRODUCTION

Potent lifestyle interventions to increase moderate-to-vigorous physical activity are urgently needed for population-level chronic disease prevention. This trial tested the independent and joint effects of a mobile health system automating adaptive goal setting and immediate financial reinforcement for increasing daily walking among insufficiently active adults.

STUDY DESIGN

Participants were randomized into a 2 (adaptive versus static goal setting) X 2 (immediate versus delayed financial incentive timing) condition factorial trial to increase walking.

SETTINGS/PARTICIPANTS

Participants (N=512 adults) were recruited between 2016 and 2018 and were 64.5% female, aged 18-60 years, 18.8% Hispanic, 6.1% African American, and 83% White.

INTERVENTION

Principles of reinforcement and behavioral economics directed intervention design.

MAIN OUTCOME MEASURES

Participants wore accelerometers daily (133,876 day-level observations) that remotely measured moderate-to-vigorous physical activity bout minutes of ≥3 minutes/day for 1 year. Primary outcomes were between-condition differences in (1) engaging ≥1 bout of moderate-to-vigorous physical activity on each day and (2) on days with ≥1 bout, daily total moderate-to-vigorous physical activity minutes.

RESULTS

Mixed-effects hurdle models tested treatment group X phase (time) interactions using an intent-to-treat approach in 2021. Engaging in any ambulatory moderate-to-vigorous physical activity was greater for Adaptive than for Static Goal groups (OR=2.34, 95% CI=2.10, 2.60 vs OR=1.66, 95% CI=1.50, 1.84; p<0.001) and for Immediate than for Static Reinforcement groups (OR=2.16 95% CI=1.94, 2.40 vs OR=1.77, 95% CI=1.59, 1.97; p<0.01). The Immediate Reinforcement group increased by 16.54 moderate-to-vigorous physical activity minutes/day, whereas the Delayed Reinforcement group increased by 9.91 minutes/day (p<0.001). The combined Adaptive Goals + Immediate Reinforcement group increased by 16.52 moderate-to-vigorous physical activity minutes/day, significantly more than that of either Delayed Reinforcement group.

CONCLUSIONS

This study offers automated and scalable-behavior change strategies for increasing walking among adults most at-risk for chronic diseases attributed to sedentary lifestyles.

TRIAL REGISTRATION

This study is registered at www.clinicaltrials.gov (ClinicalTrials.gov Identifier: NCT02717663).

Effects of indulgent food snacking, with and without exercise training, on body weight, fat mass, and cardiometabolic risk markers in overweight and obese men

We hypothesized that exercise training would prevent gains in body weight and body fat, and worsening of cardiometabolic risk markers, during a 4-week period of indulgent food snacking in overweight/obese men. Twenty-eight physically inactive men (ages 19-47 yr) with body mass index (BMI) ≥25 kg/m2 consumed 48 donuts (2/day, 6 days/week; ~14,500 kcal total) for 4 weeks while maintaining habitual diet. Men were randomly assigned to control (n = 9), moderate-intensity continuous training (MICT; n = 9), or high-intensity interval training (HIIT; n = 10). Exercise training occurred 4 days/week, ~250 kcal/session. Controls did not increase body weight, body fat, or visceral abdominal fat. This was partially explained by a decrease in self-reported habitual energy (-239 kcal/day, p = 0.05) and carbohydrate (-47 g/day; p = 0.02) intake. Large inter-individual variability in changes in body weight, fat, and fat-free mass was evident in all groups. Fasting blood pressure, and blood concentrations of glucose, insulin, and lipids were unchanged in all groups. Glucose incremental area under the curve during an oral glucose tolerance test was reduced by 25.6% in control (p = 0.001) and 32.8% in MICT (p = 0.01) groups. Flow-mediated dilation (FMD) was not changed in any group. VO2max increased (p ≤ 0.001) in MICT (9.2%) and HIIT (12.1%) groups. We conclude that in physically inactive men with BMI ≥25 kg/m2 , consuming ~14,500 kcal as donuts over 4 weeks did not adversely affect body weight and body fat, or several markers of cardiometabolic risk. Consumption of the donuts may have prevented the expected improvement in FMD with HIIT.

Obesity treatment: Weight loss versus increasing fitness and physical activity for reducing health risks

We propose a weight-neutral strategy for obesity treatment on the following grounds: (1) the mortality risk associated with obesity is largely attenuated or eliminated by moderate-to-high levels of cardiorespiratory fitness (CRF) or physical activity (PA), (2) most cardiometabolic risk markers associated with obesity can be improved with exercise training independent of weight loss and by a magnitude similar to that observed with weight-loss programs, (3) weight loss, even if intentional, is not consistently associated with lower mortality risk, (4) increases in CRF or PA are consistently associated with greater reductions in mortality risk than is intentional weight loss, and (5) weight cycling is associated with numerous adverse health outcomes including increased mortality. Adherence to PA may improve if health care professionals consider PA and CRF as essential vital signs and consistently emphasize to their patients the myriad benefits of PA and CRF in the absence of weight loss.

Comparison of constant load exercise intensity for verification of maximal oxygen uptake following a graded exercise test in older adults

Maximal oxygen uptake (VO2 max) declines with advancing age and is a predictor of morbidity and mortality risk. The purpose here was to assess the utility of constant load tests performed either above or below peak work rate obtained from a graded exercise test for verification of VO2 max in older adults. Twenty-two healthy older adults (9M, 13F, 67 ± 6 years, BMI: 26.3 ± 5.1 kg·m-2 ) participated in the study. Participants were asked to complete two experimental trials in a randomized, counterbalanced cross-over design. Both trials (cycle ergometer) consisted of (1) an identical graded exercise test (ramp) and (2) a constant load test at either 85% (CL85; n = 22) or 110% (CL110; n = 20) of the peak work rate achieved during the associated ramp (performed 10-min post ramp). No significant differences were observed for peak VO2 (L·min-1 ) between CL85 (1.86 ± 0.72; p = 0.679) or CL110 (1.79 ± 0.73; p = 0.200) and the associated ramp (Ramp85, 1.85 ± 0.73; Ramp110, 1.85 ± 0.57). Using the study participant's mean coefficient of variation in peak VO2 between the two identical ramp tests (2.9%) to compare individual differences between constant load tests and the associated ramp revealed 19/22 (86%) of participants achieved a peak VO2 during CL85 that was similar or higher versus the ramp, while only 13/20 (65%) of participants achieved a peak VO2 during CL110 that was similar or higher versus the ramp. These data indicate that if a verification of VO2 max is warranted when testing older adults, a constant load effort at 85% of ramp peak power may be more likely to verify VO2 max as compared to an effort at 110% of ramp peak power.

Perspective: Does Glycemic Index Matter for Weight Loss and Obesity Prevention? Examination of the Evidence on "Fast" Compared with "Slow" Carbs

High-glycemic index (high-GI) foods (so-called fast carbs) have been hypothesized to promote fat storage and increase risk of obesity. To clarify whether dietary GI impacts body weight, we searched PubMed and the Cochrane Database of Systematic Reviews for observational studies reporting associations between BMI and dietary GI, and for meta-analyses of randomized controlled trials (RCTs) comparing low-GI and high-GI diets for weight loss. Data on 43 cohorts from 34 publications, totaling 1,940,968 adults, revealed no consistent differences in BMI when comparing the highest with the lowest dietary GI groups. In the 27 cohort studies that reported results of statistical comparisons, 70% showed that BMI was either not different between the highest and lowest dietary GI groups (12 of 27 cohorts) or that BMI was lower in the highest dietary GI group (7 of 27 cohorts). Results of 30 meta-analyses of RCTs from 8 publications demonstrated that low-GI diets were generally no better than high-GI diets for reducing body weight or body fat. One notable exception is that low-GI diets with a dietary GI at least 20 units lower than the comparison diet resulted in greater weight loss in adults with normal glucose tolerance but not in adults with impaired glucose tolerance. While carbohydrate quality, including GI, impacts many health outcomes, GI as a measure of carbohydrate quality appears to be relatively unimportant as a determinant of BMI or diet-induced weight loss. Based on results from observational cohort studies and meta-analyses of RCTs, we conclude that there is scant scientific evidence that low-GI diets are superior to high-GI diets for weight loss and obesity prevention.

Pathophysiology of Exercise Intolerance and Its Treatment With Exercise-Based Cardiac Rehabilitation in Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is the fastest growing form of heart failure in the United States. The cardinal feature of HFpEF is reduced exercise tolerance (peak oxygen uptake, (Equation is included in full-text article.)O2peak) secondary to impaired cardiac, vascular, and skeletal muscle function. There are currently no evidence-based drug therapies to improve clinical outcomes in patients with HFpEF. In contrast, exercise training is a proven effective intervention for improving (Equation is included in full-text article.)O2peak, aerobic endurance, and quality of life in HFpEF patients. This brief review discusses the pathophysiology of exercise intolerance and the role of exercise training to improve (Equation is included in full-text article.)O2peak in clinically stable HFpEF patients. It also discusses the mechanisms responsible for the exercise training-mediated improvements in (Equation is included in full-text article.)O2peak in HFpEF. Finally, it provides evidence-based exercise prescription guidelines for cardiac rehabilitation specialists to assist them with safely implementing exercise-based cardiac rehabilitation programs for HFpEF patients.

Integrating Transwomen and Female Athletes with Differences of Sex Development (DSD) into Elite Competition: The FIMS 2021 Consensus Statement

Sport is historically designated by the binary categorization of male and female that conflicts with modern society. Sport’s governing bodies should consider reviewing rules determining the eligibility of athletes in the female category as there may be lasting advantages of previously high testosterone concentrations for transwomen athletes and currently high testosterone concentrations in differences in sex development (DSD) athletes. The use of serum testosterone concentrations to regulate the inclusion of such athletes into the elite female category is currently the objective biomarker that is supported by most available scientific literature, but it has limitations due to the lack of sports performance data before, during or after testosterone suppression. Innovative research studies are needed to identify other biomarkers of testosterone sensitivity/responsiveness, including molecular tools to determine the functional status of androgen receptors. The scientific community also needs to conduct longitudinal studies with specific control groups to generate the biological and sports performance data for individual sports to inform the fair inclusion or exclusion of these athletes. Eligibility of each athlete to a sport-specific policy needs to be based on peer-reviewed scientific evidence made available to policymakers from all scientific communities. However, even the most evidence-based regulations are unlikely to eliminate all differences in performance between cisgender women with and without DSD and transwomen athletes. Any remaining advantage held by transwomen or DSD women could be considered as part of the athlete’s unique makeup.

0550 Insomnia is Associated with Greater Arterial Stiffness and Cardiac Dysfunction

Introduction

Insomnia is a novel and modifiable risk factor for incident cardiovascular disease (CVD). However, identification of early markers of subclinical CVD in diagnosed insomnia is understudied. Our aim for this ongoing study is to contrast markers of cardiovascular structure and function between people with insomnia and good-sleeping controls.

Methods

Persons with insomnia (met ICSD-III criteria) and good sleeping controls (&lt;8 Insomnia Severity Index, mean 8-night SOL and WASO&lt;31min) were recruited from the community. Twenty-two adults (21-39y; 55% women) with no history of CVD, diabetes, inflammatory conditions, significant hypertension, or current sleep-disordered breathing (WatchPat200, Itamar Medical) were enrolled and underwent fasting cardiovascular testing. Testing included: Central augmented aortic pressure (AP) and carotid-femoral pulse wave velocity (cfPWV) for vascular stiffness; brachial artery flow mediated dilation (FMD) to assess endothelial function; and 2D echocardiography to assess ejection fraction (EF%), left ventricular global longitudinal strain (LVGLS), left atrial volume index (LAVI), mitral valve E/e’ ratio (E/e’), and lateral e’. ANCOVA models, adjusting for age, comparing persons with insomnia (n=6) to good sleeping controls (n=16) on each cardiovascular measure were conducted.

Results

AP (range:-5,10mmHg), cfPWV (range: 4.8-7.6m/s), EF% (range:55.0-72.0%), LVGLS (range:-26,-19%) LAVI (range:14.1-26.7mL/m2), E/e’ (range:3.2-7.8), and lateral e’ (range:0.09-0.22cm/sec) were all within normal ranges according to age and sex normative standards. Mean FMD was 8.8% (SD=4.3, range:4.3-19.8%). Age adjusted ANCOVA models indicated that the insomnia group had significantly worse cardiovascular function than good sleeping controls on cfPWV (M=6.8±0.3 vs. M=5.7±0.2; p=0.004), EF% (M=60.0±1.7 vs. M=65.2±1.0; p=0.017), LVGLS (M=-21.6±0.6 vs. M=-24.3±0.4; p=0.001), and lateral e’ (M=0.12±0.01 vs. M=0.18±0.01; p=0.003). No group differences were found for AP, FMD, LAVI, and E/e’.

Conclusion

Among relatively healthy young adults, people with insomnia had greater arterial stiffness and worse left ventricular systolic and diastolic functioning.

Support

American Academy of Sleep Medicine Foundation Focused Projects Award for Junior Investigators 179-FP-18

Delay Discount Rate Moderates a Physical Activity Intervention Testing Immediate Rewards

Financial incentives can increase physical activity (PA), but differences in the immediacy of reward delivery and individual differences in delay discount rates (i.e., higher discount values associated with less tolerance for delayed rewards) may explain differential responding. The current study tested whether delay discount rate moderated the relative effectiveness of immediate financial rewards on increasing daily PA. Inactive, overweight adults (ages 18-60, N = 96) were randomized to receive either smaller, immediate goal-contingent rewards or larger, delayed rewards for participation. Delay discount rates were derived for those who completed the Monetary Choice Questionnaire (N = 85). Linear mixed models tested interactions between discount rate and intervention arm on changes in mean daily Fitbit-measured steps from baseline to intervention phases, and rates of change during the intervention phase. Across all groups, participants increased by 2258 steps/day on average from baseline to intervention and declined by 9 steps/day across the 4-month intervention phase. The mean increase in daily steps was greater for immediate reward-arm participants across all discount rates. Descriptive exploration of reward effects by delay discount rate suggested that the magnitude of reward effects decreased at higher discount rates. During the 4-month intervention phase, rates of decline in daily steps were similar in both reward arms, but declines became more pronounced at higher discount rates. Overall, intervention efficacy decreased with less tolerance for delays. The importance of financial reward immediacy for increasing PA appears to increase with greater delay discount rates.

Effects of Low-Fat and High-Fat Meals, with and without Dietary Fiber, on Postprandial Endothelial Function, Triglyceridemia, and Glycemia in Adolescents

The consumption of fiber-rich foods may negate the deleterious effects of high-fat meals on postprandial triglyceridemia and endothelial function. Despite supportive data in adults, little is known about the effects of high-fat and high-fiber foods on cardiovascular health parameters in pediatric populations. In this crossover trial, male and female adolescents (n = 10; 14.1 + 2.6 years; range 10–17 years) consumed (1) low-fat, low-fiber, (2) low-fat, high-fiber, (3) high-fat, low-fiber, and (4) high-fat, high-fiber breakfast meals in randomized order, each following an overnight fast. Baseline and 4 h post-meal blood was obtained for determination of glucose, insulin and triglyceride concentrations. Endothelial function was assessed via brachial artery flow-mediated dilation (FMD). Postprandial FMD was not significantly changed after any meal. However, regression analyses revealed a significant inverse relationship between the change in 4 h triglyceride concentration and change in 4 h FMD for the high-fat, low-fiber meal (β = −0.087; 95% CI = −0.138 to −0.037; p = 0.001) that was no longer significant in the high-fat, high-fiber meal (β = −0.044; 95% CI = −0.117 to 0.029; p = 0.227). Interpretation of these analyses must be qualified by acknowledging that between-meal comparison revealed that the two regression lines were not statistically different (p = 0.226). Addition of high-fiber cereal to the high-fat meal also reduced 4 h postprandial triglyceride increases by ~50% (p = 0.056). A high-fiber breakfast cereal did not attenuate postprandial glucose and insulin responses after consumption of a low-fat meal. While further work is needed to confirm these results in larger cohorts, our findings indicate the potential importance of cereal fiber in blunting the inverse relationship between postprandial hypertriglyceridemia and FMD after consumption of a high-fat meal in adolescents.

Effects of Glycemic Index and Cereal Fiber on Postprandial Endothelial Function, Glycemia, and Insulinemia in Healthy Adults

Both glycemic index and dietary fiber are associated with cardiovascular disease risk, which may be related in part to postprandial vascular effects. We examined the effects of both glycemic index (GI) and dietary (mainly cereal) fiber on postprandial endothelial function. Eleven adults (5 men; 6 women; age = 42.4 ± 16.1 years; weight = 70.5 ± 10.7 kg; height = 173.7 ± 8.7 cm) consumed four different breakfast meals on separate, randomized occasions: High-Fiber, Low-GI (HF-LGI: Fiber = 20.4 g; GI = 44); Low-Fiber, Low-GI (LF-LGI: Fiber = 4.3 g; GI = 43); Low-Fiber, High-GI (LF-HGI: Fiber = 3.6 g; GI = 70); High-Fiber, High-GI (HF-HGI: Fiber = 20.3 g; GI = 71). Meals were equal in total kcal (~600) and macronutrient composition (~90 g digestible carbohydrate; ~21 g protein; ~15 g fat). The HF-LGI meal resulted in a significant increase in flow-mediated dilation (FMD) 4 h after meal ingestion (7.8% ± 5.9% to 13.2% ± 5.5%; p = 0.02). FMD was not changed after the other meals. Regardless of fiber content, low-GI meals resulted in ~9% lower 4-h glucose area under curve (AUC) (p < 0.05). The HF-LGI meal produced the lowest 4-h insulin AUC, which was ~43% lower than LF-HGI and HF-HGI (p < 0.001), and 28% lower than LF-LGI (p = 0.02). We conclude that in healthy adults, a meal with low GI and high in cereal fiber enhances postprandial endothelial function. Although the effect of a low-GI meal on reducing postprandial glucose AUC was independent of fiber, the effect of a low-GI meal on reducing postprandial insulin AUC was augmented by cereal fiber.

Rationale, design, and baseline characteristics of WalkIT Arizona: A factorial randomized trial testing adaptive goals and financial reinforcement to increase walking across higher and lower walkable neighborhoods

Little change over the decades has been seen in adults meeting moderate-to-vigorous physical activity (MVPA) guidelines. Numerous individual-level interventions to increase MVPA have been designed, mostly static interventions without consideration for neighborhood context. Recent technologies make adaptive interventions for MVPA feasible. Unlike static interventions, adaptive intervention components (e.g., goal setting) adjust frequently to an individual's performance. Such technologies also allow for more precise delivery of "smaller, sooner incentives" that may result in greater MVPA than "larger, later incentives". Combined, these factors could enhance MVPA adoption. Additionally, a central tenet of ecological models is that MVPA is sensitive to neighborhood environment design; lower-walkable neighborhoods constrain MVPA adoption and maintenance, limiting the effects of individual-level interventions. Higher-walkable neighborhoods are hypothesized to enhance MVPA interventions. Few prospective studies have addressed this premise. This report describes the rationale, design, intervention components, and baseline sample of a study testing individual-level adaptive goal-setting and incentive interventions for MVPA adoption and maintenance over 2 years among adults from neighborhoods known to vary in neighborhood walkability. We scaled these evidenced-based interventions and tested them against static-goal-setting and delayed-incentive comparisons in a 2 × 2 factorial randomized trial to increase MVPA among 512 healthy insufficiently-active adults. Participants (64.3% female, M age = 45.5 ± 9.1 years, M BMI = 33.9 ± 7.3 kg/m2, 18.8% Hispanic, 84.0% White) were recruited from May 2016 to May 2018 from block groups ranked on GIS-measured neighborhood walkability and socioeconomic status (SES) and classified into four neighborhood types: "high walkable/high SES," "high walkable/low SES," "low walkable/high SES," and "low walkable/low SES." Results from this ongoing study will provide evidence for some of the central research questions of ecological models.

Chronic doxorubicin administration impacts satellite cell and capillary abundance in a muscle-specific manner

Anthracycline chemotherapies are effective at reducing disease recurrence and mortality in cancer patients. However, these drugs also contribute to skeletal muscle wasting and dysfunction. The purpose of this study was to assess the impact of chronic doxorubicin (DOX) administration on satellite cell and capillary densities in different skeletal muscles. We hypothesized that DOX would reduce satellite cell and capillary densities of the soleus (SOL) and extensor digitorum longus (EDL) muscles, along with muscle fiber size. Ovariectomized female Sprague-Dawley rats were randomized to receive three bi-weekly intraperitoneal injections of DOX (4 mg∙kg-1 ; cumulative dose 12 mg∙kg-1 ) or vehicle (VEH; saline). Animals were euthanized 5d following the last injection and the SOL and EDL were dissected and prepared for immunohistochemical and RT-qPCR analyses. Relative to VEH, CSA of the SOL and EDL fibers were 26% and 33% smaller, respectively, in DOX (P < 0.05). In the SOL, satellite cell and capillary densities were 39% and 35% lower, respectively, in DOX (P < 0.05), whereas in the EDL satellite cell and capillary densities were unaffected by DOX administration (P > 0.05). Proliferating satellite cells were unaffected by DOX in the SOL (P > 0.05). In the SOL, MYF5 mRNA expression was increased in DOX (P < 0.05), while in the EDL MGF mRNA expression was reduced in DOX (P < 0.05). Chronic DOX administration is associated with reduced fiber size in the SOL and EDL; however, DOX appeared to reduce satellite cell and capillary densities only in the SOL. These findings highlight that therapeutic targets to protect skeletal muscle from DOX may vary across muscles.

The Fluidity of Gender and Implications for the Biology of Inclusion for Transgender and Intersex Athletes

One of the most contentious issues in modern day sport arises when sports are divided into male and female categories. The International Association of Athletics Federations' (IAAF) previous policy regulating intersex athletes was suspended by the Court of Arbitration for Sport (CAS), resulting in a new policy. The challenge faced by the governing body of athletics is to formulate a policy that upholds both international law and the Olympic charter that stipulates athletes compete without discrimination of any kind. Implementation of the policy has been delayed until after a verdict, expected no later than March 26, 2019, in the Semenya versus IAAF trial in the Court of Arbitration for Sport. If the policy is enacted, it will restrict athletes from competing in the female athletics category with specific differences of sex development (DSD) in races from 400 m up to the mile in international level competitions unless they lower their natural testosterone (T) levels below 5 nmol·L. To thoroughly assess this new IAAF policy, one needs to appreciate its legal, sociological, and scientific underpinnings but also the history of previous policies attempting to define precisely how athletes should be divided into male and female categories. We previously proposed a system to deal with gender variant athletes that relied on a determination of an "athlete/athletic gender." The concept of "athlete gender" was presented to multiple audiences, and the resulting survey is included. A large majority of participants (71% of 153) who answered the survey agreed with the idea of an athlete gender. This position also was accompanied by the request for more studies (20% of those who agreed) and concern over the process of hormone monitoring (32% of those who agreed) to avoid doping misuse. The primary argument of those participating in the survey that disagreed with the position (23% of 153) was that biological differences between males and females remained even after the transition (47% of opposing comments). Mixed gender/sex competitions provide unique opportunities for athletes to compete against one another outside of the traditional male/female divide and pave the way for a more flexible approach for dealing with gender variant athletes.

Cardiorespiratory Fitness (Peak Oxygen Uptake): Safe and Effective Measure for Cardiovascular Screening Before Kidney Transplant

BACKGROUND

Significant heterogeneity exists in practice patterns and algorithms used for cardiac screening before kidney transplant. Cardiorespiratory fitness, as measured by peak oxygen uptake (VO_2peak), is an established validated predictor of future cardiovascular morbidity and mortality in both healthy and diseased populations. The literature supports its use among asymptomatic patients in abrogating the need for further cardiac testing.

METHODS AND RESULTS

We outlined a pre-renal transplant screening algorithm to incorporate VO_2peak testing among a population of asymptomatic high-risk patients (with diabetes mellitus and/or >50 years of age). Only those with VO_2peak <17 mL/kg per minute (equivalent to <5 metabolic equivalents) underwent further noninvasive cardiac screening tests. We conducted a retrospective study of the a priori dichotomization of the VO_2peak <17 versus ≥17 mL/kg per minute to determine negative and positive predictive value of future cardiac events and all-cause mortality. We report a high (>90%) negative predictive value, indicating that VO_2peak ≥17 mL/kg per minute is effective to rule out future cardiac events and all-cause mortality. However, lower VO_2peak had low positive predictive value and should not be used as a reliable metric to predict future cardiac events and/or mortality. In addition, a simple mathematical calculation documented a cost savings of ≈$272 600 in the cardiac screening among our study cohort of 637 patients undergoing evaluation for kidney and/or pancreas transplant.

CONCLUSIONS

We conclude that incorporating an objective measure of cardiorespiratory fitness with VO_2peak is safe and allows for a cost savings in the cardiovascular screening protocol among higher-risk phenotype (with diabetes mellitus and >50 years of age) being evaluated for kidney transplant.

Exercise Protects Skeletal Muscle during Chronic Doxorubicin Administration

PURPOSE

This study aimed to assess the ability for exercise training performed before and during biweekly doxorubicin (DOX) administration to attenuate adverse effects of DOX on skeletal muscle. We hypothesized that DOX treatment would increase REDD1, impair mammalian target of rapamycin (mTOR) signaling, and reduce muscle fiber size, and that exercise training would attenuate these responses.

METHODS

Eight-week-old ovariectomized female Sprague-Dawley rats were randomized to one of four treatments: exercise + DOX (Ex-Dox), Ex + vehicle (Ex-Veh), sedentary + DOX (Sed-Dox), and Sed + Veh (Sed-Veh). DOX (4 mg·kg) or vehicle (saline) intraperitoneal injections were performed biweekly for a total of three injections (cumulative dose, 12 mg·kg). Ex animals performed interval exercise (4 × 4 min, 85%-90% V˙O2peak) 5 d·wk starting 1 wk before the first injection and continued throughout study duration. Animals were euthanized ~5 d after the last injection, during which the soleus muscle was dissected and prepared for immunoblot and immunohistochemical analyses.

RESULTS

REDD1 mRNA and protein were increased only in Sed-Dox (P < 0.05). The phosphorylation of mTOR and 4E-BP1 and MHC I and MHC IIa fiber size were lower in Sed-Dox versus Sed-Veh (P < 0.05). By contrast, REDD1 mRNA and protein, mTOR, 4E-BP1, and MHC I fiber size were not different between Ex-Dox and Ex-Veh (P > 0.05). LC3BI was higher, and the LC3BII/I ratio was lower in Sed-Dox versus Sed-Veh (P < 0.05) but not between Ex-Dox and Ex-Veh (P > 0.05).

CONCLUSION

These data suggest that DOX may inhibit mTORC1 activity and reduce MHCI and MHCIIa fiber size, potentially through elevated REDD1, and that exercise may provide a therapeutic strategy to preserve skeletal muscle size during chronic DOX treatment.

Cycling efficiency and energy cost of walking in young and older adults

To determine whether age affects cycling efficiency and the energy cost of walking (Cw), 190 healthy adults, ages 18-81 yr, cycled on an ergometer at 50 W and walked on a treadmill at 1.34 m/s. Ventilation and gas exchange at rest and during exercise were used to calculate net Cw and net efficiency of cycling. Compared with the 18-40 yr age group (2.17 ± 0.33 J·kg^-1·m^-1), net Cw was not different in the 60-64 yr (2.20 ± 0.40 J·kg^-1·m^-1) and 65-69 yr (2.20 ± 0.28 J·kg^-1·m^-1) age groups, but was significantly ( P < 0.03) higher in the ≥70 yr (2.37 ± 0.33 J·kg^-1·m^-1) age group. For subjects >60 yr, net Cw was significantly correlated with age ( R² = 0.123; P = 0.002). Cycling net efficiency was not different between 18-40 yr (23.5 ± 2.9%), 60-64 yr (24.5 ± 3.6%), 65-69 yr (23.3 ± 3.6%) and ≥70 yr (24.7 ± 2.7%) age groups. Repeat tests on a subset of subjects (walking, n = 43; cycling, n = 37) demonstrated high test-retest reliability [intraclass correlation coefficients (ICC), 0.74-0.86] for all energy outcome measures except cycling net energy expenditure (ICC = 0.54) and net efficiency (ICC = 0.50). Coefficients of variation for all variables ranged from 3.1 to 7.7%. Considerable individual variation in Cw and efficiency was evident, with a ~2-fold difference between the least and most economical/efficient subjects. We conclude that, between 18 and 81 yr, net Cw was only higher for ages ≥70 yr, and that cycling net efficiency was not different across age groups. NEW & NOTEWORTHY This study illustrates that the higher energy cost of walking in older adults is only evident for ages ≥70 yr. For older adults ages 60-69 yr, the energy cost of walking is similar to that of young adults. Cycling efficiency, by contrast, is not different across age groups. Considerable individual variation (∼2-fold) in cycling efficiency and energy cost of walking is observed in young and older adults.

High-intensity interval exercise attenuates but does not eliminate endothelial dysfunction after a fast food meal

We investigated whether two different bouts of high-intensity interval exercise (HIIE) could attenuate postprandial endothelial dysfunction. Thirteen young (27 ± 1 yr), nonexercise-trained men underwent three randomized conditions: 1) four 4-min intervals at 85-95% of maximum heart rate separated by 3 min of active recovery (HIIE 4 × 4), 2) 16 1-min intervals at 85-95% of maximum heart rate separated by 1 min of active recovery (HIIE 16 × 1), and 3) sedentary control. HIIE was performed in the afternoon, ~18 h before the morning fast food meal (1,250 kcal, 63g of fat). Brachial artery flow-mediated dilation (FMD) was performed before HIIE ( baseline 1), during fasting before meal ingestion ( baseline 2), and 30 min, 2 h, and 4 h postprandial. Capillary glucose and triglycerides were assessed at fasting, 30 min, 1 h, 2 h, and 4 h (triglycerides only). Both HIIE protocols increased fasting FMD compared with control (HIIE 4 × 4: 6.1 ± 0.4%, HIIE 16 × 1: 6.3 ± 0.5%, and control: 5.1 ± 0.4%, P < 0.001). For both HIIE protocols, FMD was reduced only at 30 min postprandial but never fell below baseline 1 or FMD during control at any time point. In contrast, control FMD decreased at 2 h (3.8 ± 0.4%, P < 0.001) and remained significantly lower than HIIE 4 × 4 and 16 × 1 at 2 and 4 h. Postprandial glucose and triglycerides were unaffected by HIIE. In conclusion, HIIE performed ~18 h before a high-energy fast food meal can attenuate but not entirely eliminate postprandial decreases in FMD. This effect is not dependent on reductions in postprandial lipemia or glycemia. NEW & NOTEWORTHY Two similar high-intensity interval exercise (HIIE) protocols performed ∼18 h before ingestion of a high-energy fast food meal attenuated but did not entirely eliminate postprandial endothelial dysfunction in young men largely by improving fasting endothelial function. Both HIIE protocols produced essentially identical results, suggesting high reproducibility of HIIE effects.

Mechanisms of the Improvement in Peak VO2 With Exercise Training in Heart Failure With Reduced or Preserved Ejection Fraction

Heart failure (HF) is a major health care burden associated with high morbidity and mortality. Approximately 50% of HF patients have reduced ejection fraction (HFrEF) while the remainder of patients have preserved ejection fraction (HFpEF). A hallmark of both HF phenotypes is dyspnoea upon exertion and severe exercise intolerance secondary to impaired oxygen delivery and/or use by exercising skeletal muscle. Exercise training is a safe and effective intervention to improve peak oxygen uptake (VO_2peak) and quality of life in clinically stable HF patients, however, evidence to date suggests that the mechanism of this improvement appears to be related to underlying HF phenotype. The purpose of this review is to discuss the role of exercise training to improve VO_2peak, and how the central and peripheral adaptations that mediate the improvements in exercise tolerance may be similar or differ by HF phenotype (HFrEF or HFpEF).

Adaptive goal setting and financial incentives: a 2 × 2 factorial randomized controlled trial to increase adults' physical activity

Background

Emerging interventions that rely on and harness variability in behavior to adapt to individual performance over time may outperform interventions that prescribe static goals (e.g., 10,000 steps/day). The purpose of this factorial trial was to compare adaptive vs. static goal setting and immediate vs. delayed, non-contingent financial rewards for increasing free-living physical activity (PA).

Methods

A 4-month 2 × 2 factorial randomized controlled trial tested main effects for goal setting (adaptive vs. static goals) and rewards (immediate vs. delayed) and interactions between factors to increase steps/day as measured by a Fitbit Zip. Moderate-to-vigorous PA (MVPA) minutes/day was examined as a secondary outcome.

Results

Participants (N = 96) were mainly female (77%), aged 41 ± 9.5 years, and all were insufficiently active and overweight/obese (mean BMI = 34.1 ± 6.2). Participants across all groups increased by 2389 steps/day on average from baseline to intervention phase (p < .001). Participants receiving static goals showed a stronger increase in steps per day from baseline phase to intervention phase (2630 steps/day) than those receiving adaptive goals (2149 steps/day; difference = 482 steps/day, p = .095). Participants receiving immediate rewards showed stronger improvement (2762 step/day increase) from baseline to intervention phase than those receiving delayed rewards (2016 steps/day increase; difference = 746 steps/day, p = .009). However, the adaptive goals group showed a slower decrease in steps/day from the beginning of the intervention phase to the end of the intervention phase (i.e. less than half the rate) compared to the static goals group (−7.7 steps vs. -18.3 steps each day; difference = 10.7 steps/day, p < .001) resulting in better improvements for the adaptive goals group by study end. Rate of change over the intervention phase did not differ between reward groups. Significant goal phase x goal setting x reward interactions were observed.

Conclusions

Adaptive goals outperformed static goals (i.e., 10,000 steps) over a 4-month period. Small immediate rewards outperformed larger, delayed rewards. Adaptive goals with either immediate or delayed rewards should be preferred for promoting PA.

Trial Registration

ClinicalTrials.gov ID: NCT02053259 registered prospectively on January 31, 2014.

The effect of exercise training on biventricular myocardial strain in heart failure with preserved ejection fraction

Aims

High‐intensity interval training (HIIT) improves peak oxygen uptake and left ventricular diastology in patients with heart failure with preserved ejection fraction (HFpEF). However, its effects on myocardial strain in HFpEF remain unknown. We explored the effects of HIIT and moderate‐intensity aerobic continuous training (MI‐ACT) on left and right ventricular strain parameters in patients with HFpEF. Furthermore, we explored their relationship with peak oxygen uptake (VO_2peak).

Methods and results

Fifteen patients with HFpEF (age = 70 ± 8.3 years) were randomized to either: (i) HIIT (4 × 4 min, 85–90% peak heart rate, interspersed with 3 min of active recovery; n = 9) or (ii) MI‐ACT (30 min at 70% peak heart rate; n = 6). Patients were trained 3 days/week for 4 weeks and underwent VO_2peak testing and 2D echocardiography at baseline and after completion of the 12 sessions of supervised exercise training. Left ventricular (LV) and right ventricular (RV) average global peak systolic longitudinal strain (GLS) and peak systolic longitudinal strain rate (GSR) were quantified. Paired t‐tests were used to examine within‐group differences and unpaired t‐tests used for between‐group differences (α = 0.05). Right ventricular average global peak systolic longitudinal strain improved significantly in the HIIT group after training (pre = −18.4 ± 3.2%, post = −21.4 ± 1.7%; P = 0.02) while RV‐GSR, LV‐GLS, and LV‐GSR did not (P > 0.2). No significant improvements were observed following MI‐ACT. No significant between‐group differences were observed for any strain measure. ΔLV‐GLS and ΔRV‐GLS were modestly correlated with ΔVO_2peak (r = −0.48 and r = −0.45; P = 0.1, respectively).

Conclusions

In patients with HFpEF, 4 weeks of HIIT significantly improved RV‐GLS.

Postexercise Hypotension After Continuous, Aerobic Interval, and Sprint Interval Exercise

We examined the effects of 3 exercise bouts, differing markedly in intensity, on postexercise hypotension (PEH). Eleven young adults (age: 24.6 ± 3.7 years) completed 4 randomly assigned experimental conditions: (a) control, (b) 30-minute steady-state exercise (SSE) at 75-80% maximum heart rate (HRmax), (4) aerobic interval exercise (AIE): four 4-minute bouts at 90-95% HRmax, separated by 3 minutes of active recovery, and (d) sprint interval exercise (SIE): six 30-second Wingate sprints, separated by 4 minutes of active recovery. Exercise was performed on a cycle ergometer. Blood pressure (BP) was measured before exercise and every 15-minute postexercise for 3 hours. Linear mixed models were used to compare BP between trials. During the 3-hour postexercise, systolic BP (SBP) was lower (p < 0.001) after AIE (118 ± 10 mm Hg), SSE (121 ± 10 mm Hg), and SIE (121 ± 11 mm Hg) compared with control (124 ± 8 mm Hg). Diastolic BP (DBP) was also lower (p < 0.001) after AIE (66 ± 7 mm Hg), SSE (69 ± 6 mm Hg), and SIE (68 ± 8 mm Hg) compared with control (71 ± 7 mm Hg). Only AIE resulted in sustained (>2 hours) PEH, with SBP (120 ± 9 mm Hg) and DBP (68 ± 7 mm Hg) during the third-hour postexercise being lower (p ≤ 0.05) than control (124 ± 8 and 70 ± 7 mm Hg). Although all exercise bouts produced similar reductions in BP at 1-hour postexercise, the duration of PEH was greatest after AIE.

Predictors of fat mass changes in response to aerobic exercise training in women

Aerobic exercise training in women typically results in minimal fat loss, with considerable individual variability. We hypothesized that women with higher baseline body fat would lose more body fat in response to exercise training and that early fat loss would predict final fat loss. Eighty-one sedentary premenopausal women (age: 30.7 ± 7.8 years; height: 164.5 ± 7.4 cm; weight: 68.2 ± 16.4 kg; fat percent: 38.1 ± 8.8) underwent dual-energy x-ray absorptiometry before and after 12 weeks of supervised treadmill walking 3 days per week for 30 minutes at 70% of (Equation is included in full-text article.). Overall, women did not lose body weight or fat mass. However, considerable individual variability was observed for changes in body weight (-11.7 to +4.8 kg) and fat mass (-11.8 to +3.7 kg). Fifty-five women were classified as compensators and, as a group, gained fat mass (25.6 ± 11.1 kg to 26.1 ± 11.3 kg; p < 0.001). The strongest correlates of change in body fat at 12 weeks were change in body weight (r = 0.52) and fat mass (r = 0.48) at 4 weeks. Stepwise regression analysis that included change in body weight and body fat at 4 weeks and submaximal exercise energy expenditure yielded a prediction model that explained 37% of the variance in fat mass change (R = 0.37, p < 0.001). Change in body weight and fat mass at 4 weeks were moderate predictors of fat loss and may potentially be useful for identification of individuals who achieve less than expected weight loss or experience unintended fat gain in response to exercise training.

The Walking Interventions Through Texting (WalkIT) Trial: Rationale, Design, and Protocol for a Factorial Randomized Controlled Trial of Adaptive Interventions for Overweight and Obese, Inactive Adults

Background

Walking is a widely accepted and frequently targeted health promotion approach to increase physical activity (PA). Interventions to increase PA have produced only small improvements. Stronger and more potent behavioral intervention components are needed to increase time spent in PA, improve cardiometabolic risk markers, and optimize health.

Objective

Our aim is to present the rationale and methods from the WalkIT Trial, a 4-month factorial randomized controlled trial (RCT) in inactive, overweight/obese adults. The main purpose of the study was to evaluate whether intensive adaptive components result in greater improvements to adults’ PA compared to the static intervention components.

Methods

Participants enrolled in a 2x2 factorial RCT and were assigned to one of four semi-automated, text message–based walking interventions. Experimental components included adaptive versus static steps/day goals, and immediate versus delayed reinforcement. Principles of percentile shaping and behavioral economics were used to operationalize experimental components. A Fitbit Zip measured the main outcome: participants’ daily physical activity (steps and cadence) over the 4-month duration of the study. Secondary outcomes included self-reported PA, psychosocial outcomes, aerobic fitness, and cardiorespiratory risk factors assessed pre/post in a laboratory setting. Participants were recruited through email listservs and websites affiliated with the university campus, community businesses and local government, social groups, and social media advertising.

Results

This study has completed data collection as of December 2014, but data cleaning and preliminary analyses are still in progress. We expect to complete analysis of the main outcomes in late 2015 to early 2016.

Conclusions

The Walking Interventions through Texting (WalkIT) Trial will further the understanding of theory-based intervention components to increase the PA of men and women who are healthy, insufficiently active and are overweight or obese. WalkIT is one of the first studies focusing on the individual components of combined goal setting and reward structures in a factorial design to increase walking. The trial is expected to produce results useful to future research interventions and perhaps industry initiatives, primarily focused on mHealth, goal setting, and those looking to promote behavior change through performance-based incentives.

Trial Registration

ClinicalTrials.gov NCT02053259; https://clinicaltrials.gov/ct2/show/NCT02053259 (Archived by WebCite at http://www.webcitation.org/6b65xLvmg).