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Background and aims The associations between aerobic fitness and traditional measures of lipid metabolism in children are uncertain. We investigated whether higher levels of aerobic fitness benefit lipoprotein metabolism by exploring associations with a comprehensive lipoprotein particle profile. Methods In our prospective cohort study, we used targeted proton nuclear magnetic resonance (1H NMR) spectroscopy to profile 57 measures of lipoprotein metabolism from fasting serum samples of 858 fifth-grade Norwegian schoolchildren (49.0% girls; mean age 10.0 years). Aerobic fitness was measured using an intermittent shuttle run aerobic fitness test. We used multiple linear regression adjusted for potential confounders to examine cross-sectional and prospective associations between aerobic fitness and lipoprotein particle profile. Results Higher levels of aerobic fitness were associated with a favourable lipoprotein particle profile in the cross-sectional analysis, which included inverse associations with all measures of very low-density lipoprotein (VLDL) particles (e.g., −0.06 mmol·L−1 or –0.23 SD units; 95% CI = −0.31, −0.16 for VLDL cholesterol concentration). In the prospective analysis, the favourable pattern of associations persisted, though the individual associations tended to be more consistent with those of the cross-sectional analysis for the VLDL subclass measures compared to the low-density lipoproteins and high-density lipoproteins. Adjustment for adiposity attenuated the associations in both cross-sectional and prospective models. Nevertheless, an independent effect of aerobic fitness remained for some measures. Conclusions Improving children's aerobic fitness levels should benefit lipoprotein metabolism, though a concomitant reduction in adiposity would likely potentiate this effect. This is an open access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

AimAerobic fitness is associated with cardiometabolic risk factors in children. Associations with traditional measures of lipid metabolism are uncertain. We investigated whether higher levels of fitness benefit lipid metabolism by exploring cross-sectional and prospective associations between aerobic fitness and a comprehensive lipoprotein profile.MethodsWe used targeted proton nuclear magnetic resonance (1H NMR) spectroscopy to profile 29 measures of lipoprotein metabolism for 811 fifth-grade Norwegian schoolchildren (50.1% girls; mean age 10.2 years). Serum samples were taken on two occasions across the academic year. Aerobic fitness was measured at baseline using the Andersen aerobic fitness test. We used multiple linear regression adjusted for potential confounders to examine both cross-sectional and prospective — adjusted for baseline lipoprotein measure — associations between aerobic fitness and lipoprotein profiles.ResultsHigher levels of aerobic fitness were associated with all measures of lipoprotein metabolism in the cross-sectional analysis. There were inverse associations with the apolipoprotein B-containing (apo B) lipoprotein subclasses, including cholesterol and triglyceride concentration. The associations between aerobic fitness and the concentration of high-density lipoprotein (HDL) particles were divergent between larger and smaller subclasses. In the prospective analysis, the inverse associations between aerobic fitness and the measures of larger apo B-containing lipoprotein subclasses persisted as did all but one of the associations with triglyceride concentrations. Additional adjustment for adiposity attenuated most associations in both cross-sectional and prospective models, but an independent effect of fitness remained for certain measures.ConclusionsHigher levels of aerobic fitness are associated with a favourable lipoprotein profile, partly independent of adiposity. Associations tended to be stronger and more consistent over time for the larger apo B-containing lipoprotein measures and those of triglyceride concentration. Our results suggest that improving children’s fitness levels should have beneficial effects on lipoprotein metabolism, though a concomitant reduction in adiposity would likely be more effective.ReferencesAnderssen SA, Cooper AR, Riddoch C, Sardinha LB, Harro M, Brage S, et al. Low cardiorespiratory fitness is a strong predictor for clustering of cardiovascular disease risk factors in children independent of country, age and sex. Eur J Cardiovasc Prev Rehabil 2007.Mintjens S, Menting MD, Daams JG, van Poppel MNM, Roseboom TJ, Gemke RJBJ. Cardiorespiratory fitness in childhood and adolescence affects future cardiovascular risk factors: a systematic review of longitudinal studies. Sports Med 2018 Nov 1;48(11):2577–605.

To what extent do different methods of physical activity measurement and statistical analysis influence the reported associations between physical activity and weight gain? The obesity epidemic has led to a focus on lifestyle approaches to the prevention of weight gain. Physical activity is one such approach. A number of studies have reported beneficial associations between higher levels of physical activity and weight gain at the population level. However, limitations of physical activity measurement and analytical models in some of these studies are likely to have resulted in overestimation of the strength of association. Understanding the limitations of assessment methods and analytical models used in epidemiological research should facilitate more realistic appraisal for physical activity to prevent weight gain at the population level and inform approaches to future research.

Available 2020-06-05 Background and aims: Physical activity is favourably associated with certain markers of lipid metabolism. The relationship of physical activity with lipoprotein particle profiles in children is not known. Here we examine cross-sectional associations between objectively measured physical activity and sedentary time with serum markers of lipoprotein metabolism. Methods: Our cohort included 880 children (49.0% girls, mean age 10.2 years). Physical activity intensity and time spent sedentary were measured objectively using accelerometers. 30 measures of lipoprotein metabolism were quantified using nuclear magnetic resonance spectroscopy. Multiple linear regression models adjusted for age, sex, sexual maturity and socioeconomic status were used to determine associations of physical activity and sedentary time with lipoprotein measures. Additional models were adjusted for adiposity. Isotemporal substitution models quantified theoretical associations of replacing 30 min of sedentary time with 30 min of moderate- to vigorous-intensity physical activity (MVPA). Results: Time spent in MVPA was associated with a favourable lipoprotein profile independent of sedentary time. There were inverse associations with a number of lipoprotein measures, including most apolipoprotein B-containing lipoprotein subclasses and triglyceride measures, the ratio of total to high-density lipoprotein (HDL) cholesterol, and non-HDL cholesterol concentration. There were positive associations with larger HDL subclasses, HDL cholesterol concentration and particle size. Reallocating 30 min of sedentary time to MVPA had broadly similar associations. Sedentary time was only partly and weakly associated with an unfavourable lipoprotein profile. Conclusions: Physical activity of at least moderate-intensity is associated with a favourable lipoprotein profile in schoolchildren, independent of time spent sedentary, adiposity and other confounders.

Distance running continues to experience increased participation in the Western world, although it is associated with high injury rates. Barefoot running has been increasingly proposed as a means to prevent overuse injury due to various biomechanical differences, including reduced joint loading rates and altered kinematics and muscle activity patterns compared to shod running. The aim of this review was to systematically evaluate biomechanical differences between running barefoot and shod, including the quality of available evidence, in order to provide guidance on the phenomenon of barefoot running to the running and sports medicine communities. A comprehensive search of MEDLINE, Web of Knowledge and EMBASE from inception to January 2013 was performed. Trials evaluating injury-free recreational or competitive adults who participate in long-distance running (≥5 km), where a comparison of barefoot and shod running lower-limb kinetics, kinematics and/or electromyography were included. Studies examining sprinting and studies of single-subject design were excluded. Following initial searching, two reviewers identified a shortlist of relevant studies based on title and abstract, with the full text of these studies being tested against the inclusion criteria. References of included studies were examined and citation tracking was performed in Web of Knowledge. Two independent reviewers evaluated the methodological quality of each included study using a modified version of the Downs and Black quality index. Results of the quality assessment were used to identify high- and low-quality studies, data pooling was completed where possible and levels of evidence were determined based on the van Tulder criteria. Eighteen studies were identified, all of low methodological quality. Effect size (ES) calculation was possible for 12 studies. Pooled results indicate moderate evidence that barefoot running is associated with reduced peak ground reaction force (GRF), increased foot and ankle plantarflexion and increased knee flexion at ground contact compared with running in a neutral shoe. Limited evidence indicates barefoot running is associated with reduced impact GRF, reduced peak knee flexion and varus joint moments, and a higher stride frequency compared to a neutral shoe. Very limited to limited evidence also indicates power absorption at the knee is decreased while being increased at the ankle whilst barefoot running. Additionally, the effects of barefoot running on loading rate appear dependent on strike pattern adopted, with a forefoot strike pattern found to reduce loading rate, whilst a rearfoot strike pattern increases loading rate when running barefoot compared to shod. Key methodological weaknesses that must be addressed in future research were identified. Of particular note were absence of investigator blinding, infrequent intervention randomisation, small sample sizes and lack of evaluation following habituation. Two studies could not be retrieved because of publication in a non-English-language journal. Of particular note is that the validity of the body of work is compromised by the lack of evaluation after habituation, or re-training, of previously shod rearfoot-striking runners to barefoot forefoot-striking running styles. There has been a great deal of publicity for barefoot running, and many claims made about its effects and risks. Despite a large amount of biomechanical data available for meta-analysis, clear guidance for clinical practice is limited because of the low methodological quality of the associated studies. Preliminary biomechanical differences identified suggest barefoot running may be associated with positive biomechanical changes in regards to injury prevention, although this may be dependent on strike pattern adopted. Further research employing more robust methodology, which addresses weaknesses highlighted in this review, is needed to confirm current preliminary evidence. Additionally, prospective research would have higher validity were the biomechanical effects of habituating to barefoot running fully examined alongside an evaluation of prevention of repetitive use injury.

Physicians are increasingly being called upon to promote physical activity (PA) among patients. However, a paucity of exercise medicine teaching in the UK undergraduate medical curricula prevents students from acquiring the necessary knowledge and skills to do so. To address this issue, King's College London School of Medicine introduced an exercise medicine strand of teaching. This study evaluated the acceptability of exercise promotion behaviour change lectures and explored the knowledge and attitudes of the students who received it.Students were invited to complete a 6-item online questionnaire prior to and after exercise medicine lectures. The questionnaire assessed beliefs regarding the importance of PA in disease prevention and management, in addition to their confidence in advising patients on PA recommendations. A focus group (n=7) explored students' attitudes towards and knowledge of PA promotion and exercise prescribing.In total, 121 (15%) first-year and second-year MBBS students completed the questionnaire. Students' beliefs regarding the importance of PA in managing disease and their confidence in PA promotion among patients increased after the teaching (p0.001). More students were able to correctly identify the Chief Medical Officer recommended adult PA guidelines (p0.05). Students were enthusiastic about the exercise medicine teaching, strongly supportive of its continued inclusion in the curriculum and advocated its importance for patients and themselves as future doctors.Behaviour change teaching successfully improved students' knowledge of and confidence regarding PA promotion. These improvements are a step forward and may increase the rates and success of physician PA counselling in the future.

Background Endurance exercise capacity diminishes under hot environmental conditions. Time to exhaustion can be increased by lowering body temperature prior to exercise (pre-cooling). This systematic literature review synthesizes the current findings of the effects of pre-cooling on endurance exercise performance, providing guidance for clinical practice and further research. Methods The MEDLINE, EMBASE, CINAHL, Web of Science and SPORTDiscus databases were searched in May 2012 for studies evaluating the effectiveness of pre-cooling to enhance endurance exercise performance in hot environmental conditions (≥ 28°C). Studies involving participants with increased susceptibility to heat strain, cooling during or between bouts of exercise, and protocols where aerobic endurance was not the principle performance outcome were excluded. Potential publications were assessed by two independent reviewers for inclusion and quality. Means and standard deviations of exercise performance variables were extracted or sought from original authors to enable effect size calculations. Results In all, 13 studies were identified. The majority of studies contained low participant numbers and/or absence of sample size calculations. Six studies used cold water immersion, four crushed ice ingestion and three cooling garments. The remaining study utilized mixed methods. Large heterogeneity in methodological design and exercise protocols was identified. Effect size calculations indicated moderate evidence that cold water immersion effectively improved endurance performance, and limited evidence that ice slurry ingestion improved performance. Cooling garments were ineffective. Most studies failed to document or report adverse events. Low participant numbers in each study limited the statistical power of certain reported trends and lack of blinding could potentially have introduced either participant or researcher bias in some studies. Conclusions Current evidence indicates cold water immersion may be the most effective method of pre-cooling to improve endurance performance in hot conditions, although practicality must be considered. Ice slurry ingestion appears to be the most promising practical alternative. Interestingly, cooling garments appear of limited efficacy, despite their frequent use. Mechanisms behind effective pre-cooling remain uncertain, and optimal protocols have yet to be established. Future research should focus on standardizing exercise performance protocols, recruiting larger participant numbers to enable direct comparisons of effectiveness and practicality for each method, and ensuring potential adverse events are evaluated.

The development of functional tolerance to ethanol was studied in young adult mice of the TO Swiss and C57BL strains. Ethanol administration was by intermittent inhalation for 7 h and the development of tolerance was assessed by estimating blood ethanol concentrations at successive losses of the righting reflex. The administration of (±)α-tocopherol at a dose previously shown to inhibit the effect of ethanol on peripheral phospholipid composition (750 mg kg−1 i.p.) was without effect on functional tolerance. Chronic administration of DL-carnitine, 7% w/w in diet for 10 days, a treatment previously shown to prevent ethanol-induced triglyceride accumulation, was also without effect on ethanol tolerance. Administration of the cholesterol synthesis inhibitor, diazacholesterol (30 mg kg−1 i.p.) 3 times per week for 3 weeks from weaning, markedly inhibited the subsequent development of functional tolerance. Administration of the inhibitor of protein synthesis, cycloheximide (300 μg kg−1 i.p.) greatly inhibited the development of ethanol tolerance whereas actinomycin D (100 μg kg−1 i.p.) was without effect. The results are discussed in relation to the hypothesis that ethanol cellular tolerance results from adaptation in the composition of the lipids of neuronal membranes. It is concluded that synthesis of some protein is involved in the development of cellular tolerance and also that cholesterol plays some part in the development of tolerance.