Distance Walked and Run as Improved Metrics over Time-Based Energy Estimation in Epidemiological Studies and Prevention; Evidence from Medication Use

Purpose

The guideline physical activity levels are prescribed in terms of time, frequency, and intensity (e.g., 30 minutes brisk walking, five days a week or its energy equivalence) and assume that different activities may be combined to meet targeted goals (exchangeability premise). Habitual runners and walkers may quantify exercise in terms of distance (km/day), and for them, the relationship between activity dose and health benefits may be better assessed in terms of distance rather than time. Analyses were therefore performed to test: 1) whether time-based or distance-based estimates of energy expenditure provide the best metric for relating running and walking to hypertensive, high cholesterol, and diabetes medication use (conditions known to be diminished by exercise), and 2) the exchangeability premise.

Methods

Logistic regression analyses of medication use (dependent variable) vs. metabolic equivalent hours per day (METhr/d) of running, walking and other exercise (independent variables) using cross-sectional data from the National Runners'' (17,201 male, 16,173 female) and Walkers'' Health Studies (3,434 male, 12,384 female).

Results

Estimated METhr/d of running and walking activity were 38% and 31% greater, respectively, when calculated from self-reported time than distance in men, and 43% and 37% greater in women, respectively. Percent reductions in the odds for hypertension and high cholesterol medication use per METhr/d run or per METhr/d walked were ≥2-fold greater when estimated from reported distance (km/wk) than from time (hr/wk). The per METhr/d odds reduction was significantly greater for the distance- than the time-based estimate for hypertension (runners: P<10⁻⁵ for males and P = 0.003 for females; walkers: P = 0.03 for males and P<10⁻⁴ for females), high cholesterol medication use in runners (P<10⁻⁴ for males and P = 0.02 for females) and male walkers (P = 0.01 for males and P = 0.08 for females) and for diabetes medication use in male runners (P<10⁻³).

Conclusions

Although causality between greater exercise and lower prevalence of hypertension, high cholesterol and diabetes cannot be inferred from these cross-sectional data, the results do suggest that distance-based estimates of METhr/d run or walked provide superior metrics for epidemiological analyses to their traditional time-based estimates.     

Running for Exercise Mitigates Age-Related Deterioration of Walking Economy

Introduction

Impaired walking performance is a key predictor of morbidity among older adults. A distinctive characteristic of impaired walking performance among older adults is a greater metabolic cost (worse economy) compared to young adults. However, older adults who consistently run have been shown to retain a similar running economy as young runners. Unfortunately, those running studies did not measure the metabolic cost of walking. Thus, it is unclear if running exercise can prevent the deterioration of walking economy.

Purpose

To determine if and how regular walking vs. running exercise affects the economy of locomotion in older adults.

Methods

15 older adults (69±3 years) who walk ≥30 min, 3x/week for exercise, “walkers” and 15 older adults (69±5 years) who run ≥30 min, 3x/week, “runners” walked on a force-instrumented treadmill at three speeds (0.75, 1.25, and 1.75 m/s). We determined walking economy using expired gas analysis and walking mechanics via ground reaction forces during the last 2 minutes of each 5 minute trial. We compared walking economy between the two groups and to non-aerobically trained young and older adults from a prior study.

Results

Older runners had a 7–10% better walking economy than older walkers over the range of speeds tested (p = .016) and had walking economy similar to young sedentary adults over a similar range of speeds (p = .237). We found no substantial biomechanical differences between older walkers and runners. In contrast to older runners, older walkers had similar walking economy as older sedentary adults (p = .461) and ∼26% worse walking economy than young adults (p<.0001).

Conclusion

Running mitigates the age-related deterioration of walking economy whereas walking for exercise appears to have minimal effect on the age-related deterioration in walking economy.     

Breast Cancer Mortality vs. Exercise and Breast Size in Runners and Walkers

Purpose

Identify predictors of breast cancer mortality in women who exercised below (<7.5 metabolic equivalent hours/week, MET-hours/wk), at (7.5 to 12.5 MET-hours/wk), or above (≥12.5 MET-hours/wk) recommended levels.

Methods

Cox proportional hazard analyses of baseline pre-diagnosis MET-hours/wk vs. breast cancer mortality adjusted for follow-up age, race, baseline menopause, and estrogen and oral contraceptive use in 79,124 women (32,872 walkers, 46,252 runners) from the National Walkers'' and Runners'' Health Studies.

Results

One-hundred eleven women (57 walkers, 54 runners) died from breast cancer during the 11-year follow-up. The decline in mortality in women who exercised ≥7.5 MET-hours/wk was not different for walking and running (P = 0.34), so running and walking energy expenditures were combined. The risk for breast cancer mortality was 41.5% lower for ≥7.5 vs. <7.5 MET-hours/wk (HR: 0.585, 95%CI: 0.382 to 0.924, P = 0.02), which persisted when adjusted for BMI (HR: 0.584, 95%CI: 0.368 to 0.956, P = 0.03). Other than age and menopause, baseline bra cup size was the strongest predictor of breast cancer mortality, i.e., 57.9% risk increase per cup size when adjusted for MET-hours/wk and the other covariates (HR: 1.579, 95%CI: 1.268 to 1.966, P<0.0001), and 70.4% greater when further adjusted for BMI (HR: 1.704, 95%CI: 1.344 to 2.156, P = 10⁻⁵). Breast cancer mortality was 4.0-fold greater (HR: 3.980, 95%CI: 1.894 to 9.412, P = 0.0001) for C-cup, and 4.7-fold greater (HR: 4.668, 95%CI: 1.963 to 11.980, P = 0.0004) for ≥D-cup vs. A-cup when adjusted for BMI and other covariates. Adjustment for cup size and BMI did not eliminate the association between breast cancer mortality and ≥7.5 MET-hour/wk walked or run (HR: 0.615, 95%CI: 0.389 to 1.004, P = 0.05).

Conclusion

Breast cancer mortality decreased in association with both meeting the exercise recommendations and smaller breast volume.     

MicroRNAs as Biomarkers for Acute Atrial Remodeling in Marathon Runners (The miRathon Study – A Sub-Study of the Munich Marathon Study)

Introduction

Physical activity is beneficial for individual health, but endurance sport is associated with the development of arrhythmias like atrial fibrillation. The underlying mechanisms leading to this increased risk are still not fully understood. MicroRNAs are important mediators of proarrhythmogenic remodeling and have potential value as biomarkers in cardiovascular diseases. Therefore, the objective of our study was to determine the value of circulating microRNAs as potential biomarkers for atrial remodeling in marathon runners (miRathon study).

Methods

30 marathon runners were recruited into our study and were divided into two age-matched groups depending on the training status: elite (ER, ≥55 km/week, n = 15) and non-elite runners (NER, ≤40 km/week, n = 15). All runners participated in a 10 week training program before the marathon. MiRNA plasma levels were measured at 4 time points: at baseline (V1), after a 10 week training period (V2), immediately after the marathon (V3) and 24h later (V4). Additionally, we obtained clinical data including serum chemistry and echocardiography at each time point.

Results

MiRNA plasma levels were similar in both groups over time with more pronounced changes in ER. After the marathon miR-30a plasma levels increased significantly in both groups. MiR-1 and miR-133a plasma levels also increased but showed significant changes in ER only. 24h after the marathon plasma levels returned to baseline. MiR-26a decreased significantly after the marathon in elite runners only and miR-29b showed a non-significant decrease over time in both groups. In ER miRNA plasma levels showed a significant correlation with LA diameter, in NER miRNA plasma levels did not correlate with echocardiographic parameters.

Conclusion

MiRNAs were differentially expressed in the plasma of marathon runners with more pronounced changes in ER. Plasma levels in ER correlate with left atrial diameter suggesting that circulating miRNAs could potentially serve as biomarkers of atrial remodeling in athletes.     

Running Pace Decrease during a Marathon Is Positively Related to Blood Markers of Muscle Damage

Background

Completing a marathon is one of the most challenging sports activities, yet the source of running fatigue during this event is not completely understood. The aim of this investigation was to determine the cause(s) of running fatigue during a marathon in warm weather.

Methodology/Principal Findings

We recruited 40 amateur runners (34 men and 6 women) for the study. Before the race, body core temperature, body mass, leg muscle power output during a countermovement jump, and blood samples were obtained. During the marathon (27 °C; 27% relative humidity) running fatigue was measured as the pace reduction from the first 5-km to the end of the race. Within 3 min after the marathon, the same pre-exercise variables were obtained.

Results

Marathoners reduced their running pace from 3.5 ± 0.4 m/s after 5-km to 2.9 ± 0.6 m/s at the end of the race (P<0.05), although the running fatigue experienced by the marathoners was uneven. Marathoners with greater running fatigue (> 15% pace reduction) had elevated post-race myoglobin (1318 ± 1411 v 623 ± 391 µg L⁻¹; P<0.05), lactate dehydrogenase (687 ± 151 v 583 ± 117 U L⁻¹; P<0.05), and creatine kinase (564 ± 469 v 363 ± 158 U L⁻¹; P = 0.07) in comparison with marathoners that preserved their running pace reasonably well throughout the race. However, they did not differ in their body mass change (−3.1 ± 1.0 v −3.0 ± 1.0%; P = 0.60) or post-race body temperature (38.7 ± 0.7 v 38.9 ± 0.9 °C; P = 0.35).

Conclusions/Significance

Running pace decline during a marathon was positively related with muscle breakdown blood markers. To elucidate if muscle damage during a marathon is related to mechanistic or metabolic factors requires further investigation.     

Exercise-Induced Changes in Iron Status and Hepcidin Response in Female Runners

Background and Aims

Exercise-induced iron deficiency is a common finding in endurance athletes. It has been suggested recently that hepcidin may be an important mediator in this process.

Objective

To determine hepcidin levels and markers of iron status during long-term exercise training in female runners with depleted and normal iron stores.

Methods

Fourteen runners were divided into two groups according to iron status. Blood samples were taken during a period of eight weeks at baseline, after training and after ten days’ recovery phase.

Results

Of 14 runners, 7 were iron deficient at baseline and 10 after training. Hepcidin was lower at recovery compared with baseline (p<0.05). The mean cell haemoglobin content, haemoglobin content per reticulocyte and total iron binding capacity all decreased, whereas soluble transferrin receptor and hypochromic red cells increased after training and recovery (p<0.05 for all).

Conclusion

The prevalence of depleted iron stores was 71% at the end of the training phase. Hepcidin and iron stores decreased during long-term running training and did not recover after ten days, regardless of baseline iron status.     

Arterial stiffness is inversely associated with a better running record in a full course marathon race

[Purpose]

Arterial stiffness is an independent predictor of cardiovascular risk and may contribute to reduced running capacity in humans. This study investigated the relationship between course record and arterial stiffness in marathoners who participated in the Seoul International Marathon in 2012.

[Methods]

A total of 30 amateur marathoners (Males n = 28, Females n = 2, mean age = 51.6 ± 8.3 years) were assessed before and after the marathon race. Brachial-ankle pulse wave velocity (ba-PWV) was assessed by VP-1000 plus (Omron Healthcare Co., Ltd., Kyoto, Japan) before and immediately after the marathon race. Pearson''s correlation coefficient was used to determine the relationship between race record and ba-PWV. In addition, Wilcoxon signed rank test was used to determine the difference in ba-PWV between before and after the race.

[Results]

There was no significant change in the ba-PWV of marathoners before and after the race (1271.1 ± 185 vs. 1268.8 ± 200 cm/s, P=0.579). Both the full course record (Pearson''s correlation coefficient = 0.416, P = 0.022) and the record of half line (Pearson''s correlation coefficient = 0.482, P = 0.007) were positively related with the difference in ba-PWV, suggesting that reduced arterial stiffness is associated with a better running record in the marathon.

[Conclusion]

These results may suggest that good vascular function contributes to a better running record in the marathon race.     

Influence of a Polyphenol-Enriched Protein Powder on Exercise-Induced Inflammation and Oxidative Stress in Athletes: A Randomized Trial Using a Metabolomics Approach

Objectives

Polyphenol supplementation was tested as a countermeasure to inflammation and oxidative stress induced by 3-d intensified training.

Methods

Water soluble polyphenols from blueberry and green tea extracts were captured onto a polyphenol soy protein complex (PSPC). Subjects were recruited, and included 38 long-distance runners ages 19–45 years who regularly competed in road races. Runners successfully completing orientation and baseline testing (N = 35) were randomized to 40 g/d PSPC (N = 17) (2,136 mg/d gallic acid equivalents) or placebo (N = 18) for 17 d using double-blinded methods and a parallel group design, with a 3-d running period inserted at day 14 (2.5 h/d, 70% VO_2max). Blood samples were collected pre- and post-14 d supplementation, and immediately and 14 h after the third day of running in subjects completing all aspects of the study (N = 16 PSPC, N = 15 placebo), and analyzed using a metabolomics platform with GC-MS and LC-MS.

Results

Metabolites characteristic of gut bacteria metabolism of polyphenols were increased with PSPC and 3 d running (e.g., hippurate, 4-hydroxyhippurate, 4-methylcatechol sulfate, 1.8-, 1.9-, 2.5-fold, respectively, P<0.05), an effect which persisted for 14-h post-exercise. Fatty acid oxidation and ketogenesis were induced by exercise in both groups, with more ketones at 14-h post-exercise in PSPC (3-hydroxybutyrate, 1.8-fold, P<0.05). Established biomarkers for inflammation (CRP, cytokines) and oxidative stress (protein carbonyls) did not differ between groups.

Conclusions

PSPC supplementation over a 17-d period did not alter established biomarkers for inflammation and oxidative stress but was linked to an enhanced gut-derived phenolic signature and ketogenesis in runners during recovery from 3-d heavy exertion.

Trial Registration

ClinicalTrials.gov, U.S. National Institutes of Health, identifier: {"type":"clinical-trial","attrs":{"text":"NCT01775384","term_id":"NCT01775384"}}NCT01775384     

Impact of Walking on Glycemic Control and Other Cardiovascular Risk Factors in Type 2 Diabetes: A Meta-Analysis

Background

Walking is the most popular and most preferred exercise among type 2 diabetes patients, yet compelling evidence regarding its beneficial effects on cardiovascular risk factors is still lacking. The aim of this meta-analysis of randomized controlled trials (RCTs) was to evaluate the association between walking and glycemic control and other cardiovascular risk factors in type 2 diabetes patients.

Methods

Three databases were searched up to August 2014. English-language RCTs were eligible for inclusion if they had assessed the walking effects (duration ≥8 weeks) on glycemic control or other cardiovascular risk factors among type 2 diabetes patients. Data were pooled using a random-effects model. Subgroup analyses based on supervision status and meta-regression analyses of variables regarding characteristics of participants and walking were performed to investigate their association with glycemic control.

Results

Eighteen studies involving 20 RCTs (866 participants) were included. Walking significantly decreased glycosylated haemoglobin A1c (HbA1c) by 0.50% (95% confidence intervals [CI]: −0.78% to −0.21%). Supervised walking was associated with a pronounced decrease in HbA1c (WMD −0.58%, 95% CI: −0.93% to −0.23%), whereas non-supervised walking was not. Further subgroup analysis suggested non-supervised walking using motivational strategies is also effective in decreasing HbA1c (WMD −0.53%, 95% CI: −1.05% to −0.02%). Effects of covariates on HbA1c change were generally unclear. For other cardiovascular risk factors, walking significantly reduced body mass index (BMI) and lowered diastolic blood pressure (DBP), but non-significantly lowered systolic blood pressure (SBP), or changed high-density or low-density lipoprotein cholesterol levels.

Conclusions

This meta-analysis supports that walking decreases HbA1c among type 2 diabetes patients. Supervision or the use of motivational strategies should be suggested when prescribed walking to ensure optimal glycemic control. Walking also reduces BMI and lowers DBP, however, it remains insufficient regarding the association of walking with lowered SBP or improved lipoprotein profiles.

Trial Registration

PROSPERO CRD42014009515     

The Relationship of Walking Intensity to Total and Cause-Specific Mortality. Results from the National Walkers’ Health Study

Purpose

Test whether: 1) walking intensity predicts mortality when adjusted for walking energy expenditure, and 2) slow walking pace (≥24-minute mile) identifies subjects at substantially elevated risk for mortality.

Methods

Hazard ratios from Cox proportional survival analyses of all-cause and cause-specific mortality vs. usual walking pace (min/mile) in 7,374 male and 31,607 female recreational walkers. Survival times were left censored for age at entry into the study. Other causes of death were treated as a competing risk for the analyses of cause-specific mortality. All analyses were adjusted for sex, education, baseline smoking, prior heart attack, aspirin use, diet, BMI, and walking energy expenditure. Deaths within one year of baseline were excluded.

Results

The National Death Index identified 1968 deaths during the average 9.4-year mortality surveillance. Each additional minute per mile in walking pace was associated with an increased risk of mortality due to all causes (1.8% increase, P=10^-5), cardiovascular diseases (2.4% increase, P=0.001, 637 deaths), ischemic heart disease (2.8% increase, P=0.003, 336 deaths), heart failure (6.5% increase, P=0.001, 36 deaths), hypertensive heart disease (6.2% increase, P=0.01, 31 deaths), diabetes (6.3% increase, P=0.004, 32 deaths), and dementia (6.6% increase, P=0.0004, 44 deaths). Those reporting a pace slower than a 24-minute mile were at increased risk for mortality due to all-causes (44.3% increased risk, P=0.0001), cardiovascular diseases (43.9% increased risk, P=0.03), and dementia (5.0-fold increased risk, P=0.0002) even though they satisfied the current exercise recommendations by walking ≥7.5 metabolic equivalent (MET)-hours per week.

Conclusions

The risk for mortality: 1) decreases in association with walking intensity, and 2) increases substantially in association for walking pace ≥24 minute mile (equivalent to <400m during a six-minute walk test) even among subjects who exercise regularly.     

Dynamic Patterns of Forces and Loading Rate in Runners with Unilateral Plantar Fasciitis: A Cross-Sectional Study

Aim/Hypothesis

The etiology of plantar fasciitis (PF) has been related to several risk factors, but the magnitude of the plantar load is the most commonly described factor. Although PF is the third most-common injury in runners, only two studies have investigated this factor in runners, and their results are still inconclusive regarding the injury stage.

Objective

Analyze and compare the plantar loads and vertical loading rate during running of runners in the acute stage of PF to those in the chronic stage of the injury in relation to healthy runners.

Methods

Forty-five runners with unilateral PF (30 acute and 15 chronic) and 30 healthy control runners were evaluated while running at 12 km/h for 40 meters wearing standardized running shoes and Pedar-X insoles. The contact area and time, maximum force, and force-time integral over the rearfoot, midfoot, and forefoot were recorded and the loading rate (20–80% of the first vertical peak) was calculated. Groups were compared by ANOVAs (p<0.05).

Results

Maximum force and force-time integral over the rearfoot and the loading rate was higher in runners with PF (acute and chronic) compared with controls (p<0.01). Runners with PF in the acute stage showed lower loading rate and maximum force over the rearfoot compared to runners in the chronic stage (p<0.01).

Conclusion

Runners with PF showed different dynamic patterns of plantar loads during running over the rearfoot area depending on the injury stage (acute or chronic). In the acute stage of PF, runners presented lower loading rate and forces over the rearfoot, possibly due to dynamic mechanisms related to pain protection of the calcaneal area.     

The Role of Walkers’ Needs and Expectations in Supporting Maintenance of Attendance at Walking Groups: A Longitudinal Multi-Perspective Study of Walkers and Walk Group Leaders

Background

There is good evidence that when people’s needs and expectations regarding behaviour change are met, they are satisfied with that change, and maintain those changes. Despite this, there is a dearth of research on needs and expectations of walkers when initially attending walking groups and whether and how these needs and expectations have been satisfied after a period of attendance. Equally, there is an absence of research on how people who lead these groups understand walkers’ needs and walk leaders’ actions to address them. The present study was aimed at addressing both of these gaps in the research.

Methods

Two preliminary thematic analyses were conducted on face-to-face interviews with (a) eight walkers when they joined walking groups, five of whom were interviewed three months later, and (b) eight walk leaders. A multi-perspective analysis building upon these preliminary analyses identified similarities and differences within the themes that emerged from the interviews with walkers and walk leaders.

Results

Walkers indicated that their main needs and expectations when joining walking groups were achieving long-term social and health benefits. At the follow up interviews, walkers indicated that satisfaction with meeting similar others within the groups was the main reason for continued attendance. Their main source of dissatisfaction was not feeling integrated in the existing walking groups. Walk leaders often acknowledged the same reasons for walkers joining and maintaining attendance at walking. However, they tended to attribute dissatisfaction and drop out to uncontrollable environmental factors and/or walkers’ personalities. Walk leaders reported a lack of efficacy to effectively address walkers’ needs.

Conclusions

Interventions to increase retention of walkers should train walk leaders with the skills to help them modify the underlying psychological factors affecting walkers’ maintenance at walking groups. This should result in greater retention of walkers in walking groups, thereby allowing walkers to receive the long-term social and health benefits of participation in these groups.     

Decreased Variability of the 6-Minute Walk Test by Heart Rate Correction in Patients with Neuromuscular Disease

Objective

The 6-minute walk test is widely used to assess functional status in neurological disorders. However, the test is subject to great inter-test variability due to fluctuating motivation, fatigue and learning effects. We investigated whether inter-test variability of the 6MWT can be reduced by heart rate correction.

Methods

Sixteen patients with neuromuscular diseases, including Facioscapulohumeral muscular dystrophy, Limb-girdle muscular dystrophy, Charcot-Marie-Tooths, Dystrophia Myotonica and Congenital Myopathy and 12 healthy subjects were studied. Patients were excluded if they had cardiac arrhythmias, if they received drug treatment for hypertension or any other medical conditions that could interfere with the interpretation of the heart rate and walking capability. All completed three 6-minute walk tests on three different test-days. Heart rate was measured continuously.

Results

Successive standard 6-minute walk tests showed considerable learning effects between Tests 1 and 2 (4.9%; P = 0.026), and Tests 2 and 3 (4.5%; P = 0.020) in patients. The same was seen in controls between Tests 1 and 2 (8.1%; P = 0.039)). Heart rate correction abolished this learning effect.

Conclusion

A modified 6-minute walk test, by correcting walking distance with average heart rate during walking, decreases the variability among repeated 6-minute walk tests, and should be considered as an alternative outcome measure to the standard 6-minute walk test in future clinical follow-up and treatment trials.     

Effect of a 12-week walking exercise program on body composition and immune cell count in patients with breast cancer who are undergoing chemotherapy

Purpose

The purpose of this study was to examine the effect of a 12-week walking exercise program on body composition and immune cell count in patients with breast cancer who are undergoing chemotherapy.

Methods

Twenty patients (age, 47.8 ± 3.12) participated in the study. Body composition (weight, body mass index, muscle weight, body fat mass, and percent body fat) and the cell counts for immune cells (white blood corpuscles, lymphocytes, helper T cells, cytotoxic T cells, natural killer cells, and natural killer T cells) were measured before and after the 12-week walking exercise program. SPSS 17.0 statistical software was used. The two-way repeated ANOVA with post hoc was used to determine the difference between time and interaction.

Results

There were significant reductions in the weight (p < .05), BMI (p < .01), and percent body fat (p < .05) after the 12-week walking exercise program. However, the immune cell counts did not change significantly.

Conclusion

These results indicated that the 12-week walking exercise program had an effect on the balances among weight, BMI and percent body fat in patients with breast cancer.     

Predictors of Diabetes in Older People in Urban China

Background

China has the largest number of people with diabetes in the world. Over the last 30 years China has experienced rapid economic growth and a growing income gap between rich and poor. The population is ageing, however diabetes in older people has not been well studied to date. In this study we determined incidence and predictors of diabetes in older Chinese people.

Methods

During 2001, using a standard interview method, we examined 1,317 adults aged ≥65 years who did not have diabetes in the city of Hefei, and characterized baseline risk factors. Over 7.5 years of follow up, we documented incident diabetes using self-reported doctor diagnosis and the cause of death in the whole cohort, and HbA_1C ≥48 mmol/mol in a nested case-control sample. A multivariate Cox regression model was employed to investigate risk of diabetes in relation to baseline risk factors.

Results

During follow up, 119 persons had newly diagnosed diabetes. World age-standardised incidence of diabetes was 24.5 (95% CI 19.5–29.5) per 1,000 person-years. Risk of diabetes was significantly and positively associated with income, waist circumference and body mass index, smoking and uncontrolled hypertension, but negatively associated with having a hobby of walking and frequency of visiting children/other relatives and contacting neighbours/friends. Higher income was significantly associated with increased diabetes risk regardless of cardiovascular and psychosocial risk factors. Compared to those with middle income and no psychosocial risk factors, the hazard ratio for incident diabetes among participants with high income and psychosocial risk was 2.13 (95% CI 1.02–4.45).

Conclusions

Increasing incidence of diabetes in relation to high income has become an important public health issue in China. Maintaining social networks and gentle physical activities and reducing psychosocial factors may be integrated into current multi-faceted preventive strategies for curbing the epidemic of diabetes in the older population.     

How Do Humans Control Physiological Strain during Strenuous Endurance Exercise?

Background

Distance running performance is a viable model of human locomotion.

Methodology/Principal Findings

To evaluate the physiologic strain during competitions ranging from 5–100 km, we evaluated heart rate (HR) records of competitive runners (n = 211). We found evidence that: 1) physiologic strain (% of maximum HR (%HRmax)) increased in proportional manner relative to distance completed, and was regulated by variations in running pace; 2) the %HRmax achieved decreased with relative distance; 3) slower runners had similar %HRmax response within a racing distance compared to faster runners, and despite differences in pace, the profile of %HRmax during a race was very similar in runners of differing ability; and 4) in cases where there was a discontinuity in the running performance, there was evidence that physiologic effort was maintained for some time even after the pace had decreased.

Conclusions/Significance

The overall results suggest that athletes are actively regulating their relative physiologic strain during competition, although there is evidence of poor regulation in the case of competitive failures.     

Does Increased Exercise or Physical Activity Alter Ad-Libitum Daily Energy Intake or Macronutrient Composition in Healthy Adults? A Systematic Review

Background

The magnitude of the negative energy balance induced by exercise may be reduced due to compensatory increases in energy intake.

Objective

To address the question: Does increased exercise or physical activity alter ad-libitum daily energy intake or macronutrient composition in healthy adults?

Data Sources

PubMed and Embase were searched (January 1990–January 2013) for studies that presented data on energy and/or macronutrient intake by level of exercise, physical activity or change in response to exercise. Ninety-nine articles (103 studies) were included.

Study Eligibility Criteria

Primary source articles published in English in peer-reviewed journals. Articles that presented data on energy and/or macronutrient intake by level of exercise or physical activity or changes in energy or macronutrient intake in response to acute exercise or exercise training in healthy (non-athlete) adults (mean age 18–64 years).

Study Appraisal and Synthesis Methods

Articles were grouped by study design: cross-sectional, acute/short term, non-randomized, and randomized trials. Considerable heterogeneity existed within study groups for several important study parameters, therefore a meta-analysis was considered inappropriate. Results were synthesized and presented by study design.

Results

No effect of physical activity, exercise or exercise training on energy intake was shown in 59% of cross-sectional studies (n = 17), 69% of acute (n = 40), 50% of short-term (n = 10), 92% of non-randomized (n = 12) and 75% of randomized trials (n = 24). Ninety-four percent of acute, 57% of short-term, 100% of non-randomized and 74% of randomized trials found no effect of exercise on macronutrient intake. Forty-six percent of cross-sectional trials found lower fat intake with increased physical activity.

Limitations

The literature is limited by the lack of adequately powered trials of sufficient duration, which have prescribed and measured exercise energy expenditure, or employed adequate assessment methods for energy and macronutrient intake.

Conclusions

We found no consistent evidence that increased physical activity or exercise effects energy or macronutrient intake.     

Acute Effects of Aerosolized Iloprost in COPD Related Pulmonary Hypertension - A Randomized Controlled Crossover Trial

Background

Inhaled iloprost potentially improves hemodynamics and gas exchange in patients with chronic obstructive pulmonary disease (COPD) and secondary pulmonary hypertension (PH).

Objectives

To evaluate acute effects of aerosolized iloprost in patients with COPD-associated PH.

Methods

A randomized, double blind, crossover study was conducted in 16 COPD patients with invasively confirmed PH in a single tertiary care center. Each patient received a single dose of 10 µg iloprost (low dose), 20 µg iloprost (high dose) and placebo during distinct study-visits. The primary end-point of the study was exercise capacity as assessed by the six minute walking distance.

Results

Both iloprost doses failed to improve six-minute walking distance (p = 0.36). Low dose iloprost (estimated difference of the means −1.0%, p = 0.035) as well as high dose iloprost (−2.2%, p<0.001) significantly impaired oxygenation at rest. Peak oxygen consumption and carbon dioxide production differed significantly over the three study days (p = 0.002 and p = 0.003, accordingly). As compared to placebo, low dose iloprost was associated with reduced peak oxygen consumption (−76 ml/min, p = 0.002), elevated partial pressure of carbon dioxide (0.27 kPa, p = 0.040) and impaired ventilation during exercise (−3.0l/min, p<0.001).

Conclusions

Improvement of the exercise capacity after iloprost inhalation in patients with COPD-associated mild to moderate PH is very unlikely.

Trial Registration

Controlled-Trials.com ISRCTN61661881     

Mean Platelet Volume (MPV) Predicts Middle Distance Running Performance

Background

Running economy and performance in middle distance running depend on several physiological factors, which include anthropometric variables, functional characteristics, training volume and intensity. Since little information is available about hematological predictors of middle distance running time, we investigated whether some hematological parameters may be associated with middle distance running performance in a large sample of recreational runners.

Methods

The study population consisted in 43 amateur runners (15 females, 28 males; median age 47 years), who successfully concluded a 21.1 km half-marathon at 75–85% of their maximal aerobic power (VO₂max). Whole blood was collected 10 min before the run started and immediately thereafter, and hematological testing was completed within 2 hours after sample collection.

Results

The values of lymphocytes and eosinophils exhibited a significant decrease compared to pre-run values, whereas those of mean corpuscular volume (MCV), platelets, mean platelet volume (MPV), white blood cells (WBCs), neutrophils and monocytes were significantly increased after the run. In univariate analysis, significant associations with running time were found for pre-run values of hematocrit, hemoglobin, mean corpuscular hemoglobin (MCH), red blood cell distribution width (RDW), MPV, reticulocyte hemoglobin concentration (RetCHR), and post-run values of MCH, RDW, MPV, monocytes and RetCHR. In multivariate analysis, in which running time was entered as dependent variable whereas age, sex, blood lactate, body mass index, VO₂max, mean training regimen and the hematological parameters significantly associated with running performance in univariate analysis were entered as independent variables, only MPV values before and after the trial remained significantly associated with running time. After adjustment for platelet count, the MPV value before the run (p = 0.042), but not thereafter (p = 0.247), remained significantly associated with running performance.

Conclusion

The significant association between baseline MPV and running time suggest that hyperactive platelets may exert some pleiotropic effects on endurance performance.