Context Pre-exercise nutrient availability alters acute metabolic responses to exercise, which could modulate training responsiveness. Objective To assess acute and chronic effects of exercise performed before versus after nutrient ingestion on whole-body and intramuscular lipid utilization and postprandial glucose metabolism. Design (1) Acute, randomized, crossover design (Acute Study); (2) 6-week, randomized, controlled design (Training Study). Setting General community. Participants Men with overweight/obesity (mean ± standard deviation, body mass index: 30.2 ± 3.5 kg⋅m-2 for Acute Study, 30.9 ± 4.5 kg⋅m-2 for Training Study). Interventions Moderate-intensity cycling performed before versus after mixed-macronutrient breakfast (Acute Study) or carbohydrate (Training Study) ingestion. Results Acute Study—exercise before versus after breakfast consumption increased net intramuscular lipid utilization in type I (net change: –3.44 ± 2.63% versus 1.44 ± 4.18% area lipid staining, P < 0.01) and type II fibers (–1.89 ± 2.48% versus 1.83 ± 1.92% area lipid staining, P < 0.05). Training Study—postprandial glycemia was not differentially affected by 6 weeks of exercise training performed before versus after carbohydrate intake (P > 0.05). However, postprandial insulinemia was reduced with exercise training performed before but not after carbohydrate ingestion (P = 0.03). This resulted in increased oral glucose insulin sensitivity (25 ± 38 vs –21 ± 32 mL⋅min-1⋅m-2; P = 0.01), associated with increased lipid utilization during exercise (r = 0.50, P = 0.02). Regular exercise before nutrient provision also augmented remodeling of skeletal muscle phospholipids and protein content of the glucose transport protein GLUT4 (P < 0.05). Conclusions Experiments investigating exercise training and metabolic health should consider nutrient-exercise timing, and exercise performed before versus after nutrient intake (ie, in the fasted state) may exert beneficial effects on lipid utilization and reduce postprandial insulinemia.

Relationship between monetary delay discounting and obesity: A systematic review and meta-regression Background and objectives: Previous studies have documented that high rates of delay discounting are associated with obesity. However, studies utilizing monetary reward experiments typically report no associations, as opposed to positive associations apparent in studies utilising food-reward experiments. Our objective was to investigate the reasons behind the mixed evidence from a methodological perspective using systematic review and meta-analytic methodologies. Methods: Seven databases (EMBASE, MEDLINE, PsycINFO, Scopus, Web of Science, Econlit and IBSS) were systematically searched. Logistic meta-regression was applied to identify the determinants of a significant association and risk of bias was assessed using a modified form of the Newcastle Ottawa cohort scale. Results: A total of 59 studies were identified, among which 29 studies (49.2%) found a significant positive association and 29 (49.2%) reported no association. A higher proportion of significant and positive associations was reported in those studies utilizing 'best-practice' methods (i.e. appropriate measurement models) to estimate monetary delay discounting (15/27; 55.6%) and incentive-compatible experiments (10/16; 62.5%) than those using non-'best-practice' methods (14/34; 41.2%) and hypothetical experiments (19/43; 44.2%). All five studies utilizing both 'best-practice' methods and incentive-compatible experiments generated a positive and significant relationship. Results from a logistic meta-regression also suggested that studies 3 employing incentive-compatible experiments (OR: 4.38, 95% CI = 1.05-18.33, p-value: 0.04), 'best-practice' methods (OR: 4.40, 95% CI = 0.88-22.99, p-value: 0.07), parametric methods (OR: 3.36, 95% CI = 0.83-13.57, p-value: 0.04), those conducted in children/adolescent populations (OR: 3.90, 95% CI = 0.85-17.88, p-value: 0.08), and those with larger sample size (OR: 1.91, 95% CI = 1.15-3.18, p-value: 0.01) tended to show positive and significant associations between delay discounting and obesity. Conclusions: This review suggests that the mixed evidence to date is a result of methodological heterogeneity, and that future studies should utilise 'best practice' methods.

Purpose Prior studies exploring the reliability of peak fat oxidation (PFO) and the intensity that elicits PFO (FATMAX) are often limited by small samples. This study characterised the reliability of PFO and FATMAX in a large cohort of healthy men and women. Methods Ninety-nine adults [49 women; age: 35 (11) years; $$\dot{V}$$ V ˙ O2peak: 42.2 (10.3) mL·kg BM−1·min−1; mean (SD)] completed two identical exercise tests (7–28 days apart) to determine PFO (g·min−1) and FATMAX (%$$\dot{V}$$ V ˙ O2peak) by indirect calorimetry. Systematic bias and the absolute and relative reliability of PFO and FATMAX were explored in the whole sample and sub-categories of: cardiorespiratory fitness, biological sex, objectively measured physical activity levels, fat mass index (derived by dual-energy X-ray absorptiometry) and menstrual cycle status. Results No systematic bias in PFO or FATMAX was found between exercise tests in the entire sample (− 0.01 g·min−1 and 0%$$\dot{V}$$ V ˙ O2peak, respectively; p > 0.05). Absolute reliability was poor [within-subject coefficient of variation: 21% and 26%; typical errors: ± 0.06 g·min−1 and × / ÷ 1.26%$$\dot{V}$$ V ˙ O2peak; 95% limits of agreement: ± 0.17 g·min−1 and × / ÷ 1.90%$$\dot{V}$$ V ˙ O2peak, respectively), despite high (r = 0.75) and moderate (r = 0.45) relative reliability for PFO and FATMAX, respectively. These findings were consistent across all sub-groups. Conclusion Repeated assessments are required to more accurately determine PFO and FATMAX.

Purpose To examine whether calcium type and co-ingestion with protein alter gut hormone availability. Methods Healthy adults aged 26 ± 7 years (mean ± SD) completed three randomized, double-blind, crossover studies. In all studies, arterialized blood was sampled postprandially over 120 min to determine GLP-1, GIP and PYY responses, alongside appetite ratings, energy expenditure and blood pressure. In study 1 (n = 20), three treatments matched for total calcium content (1058 mg) were compared: calcium citrate (CALCITR); milk minerals rich in calcium (MILK MINERALS); and milk minerals rich in calcium plus co-ingestion of 50 g whey protein hydrolysate (MILK MINERALS + PROTEIN). In study 2 (n = 6), 50 g whey protein hydrolysate (PROTEIN) was compared to MILK MINERALS + PROTEIN. In study 3 (n = 6), MILK MINERALS was compared to the vehicle of ingestion (water plus sucralose; CONTROL). Results MILK MINERALS + PROTEIN increased GLP-1 incremental area under the curve (iAUC) by ~ ninefold (43.7 ± 11.1 pmol L −1 120 min; p < 0.001) versus both CALCITR and MILK MINERALS, with no difference detected between CALCITR (6.6 ± 3.7 pmol L −1 120 min) and MILK MINERALS (5.3 ± 3.5 pmol L −1 120 min; p > 0.999). MILK MINERALS + PROTEIN produced a GLP-1 iAUC ~ 25% greater than PROTEIN (p = 0.024; mean difference: 9.1 ± 6.9 pmol L −1 120 min), whereas the difference between MILK MINERALS versus CONTROL was small and nonsignificant (p = 0.098; mean difference: 4.2 ± 5.

Background Increasing physical activity in the workplace can provide physical and mental health benefits for employees and economic benefits for the employer through reduced absenteeism and increased productivity. However, there is limited evidence on effective behaviour change interventions in workplace settings that led to maintained physical activity. This study aimed to address this gap and contribute to the evidence base for effective and cost-effective workplace interventions. Objectives To determine the effectiveness and cost-effectiveness of the Physical Activity Loyalty scheme, a multicomponent intervention based on concepts similar to those that underpin a high-street loyalty card, which was aimed at encouraging habitual physical activity behaviour and maintaining increases in mean number of steps per day. Design A cluster randomised controlled trial with an embedded economic evaluation, behavioural economic experiments, mediation analyses and process evaluation. Setting Office-based employees from public sector organisations in Belfast and Lisburn city centres in Northern Ireland. Participants A total of 853 participants [mean age 43.6 years (standard deviation 9.6 years); 71% of participants were female] were randomly allocated by cluster to either the intervention group or the (waiting list) control group. Intervention The 6-month intervention consisted of financial incentives (retail vouchers), feedback and other evidence-based behaviour change techniques. Sensors situated in the vicinity of the workplaces allowed participants to monitor their accumulated minutes of physical activity. Main outcome measures The primary outcome was mean number of steps per day recorded using a sealed pedometer (Yamax Digiwalker CW-701; Yamax, Tasley, UK) worn on the waist for 7 consecutive days and at 6 and 12 months post intervention. Secondary outcomes included health, mental well-being, quality of life, work absenteeism and presenteeism, and the use of health-care resources. Results The mean number of steps per day were significantly lower for the intervention group than the control group [6990 mean number of steps per day (standard deviation 3078) vs. 7576 mean number of steps per day (standard deviation 3345), respectively], with an adjusted mean difference of –336 steps (95% confidence interval –612 to –60 steps; p = 0.02) at 6 months post baseline, but not significantly lower at 12 months post baseline. There was a small but significant enhancement of mental well-being in the intervention group (difference between groups for the Warwick–Edinburgh Mental Wellbeing Scale of 1.34 points, 95% confidence interval 0.48 to 2.20 points), but not for the other secondary outcomes. An economic evaluation suggested that, overall, the scheme was not cost-effective compared with no intervention. The intervention was £25.85 (95% confidence interval –£29.89 to £81.60) more costly per participant than no intervention and had no effect on quality-adjusted life-years (incremental quality-adjusted life-years –0.0000891, 95% confidence interval –0.008 to 0.008). Limitations Significant restructuring of participating organisations during the study resulted in lower than anticipated recruitment and retention rates. Technical issues affected intervention fidelity. Conclusions Overall, assignment to the intervention group resulted in a small but significant decline in the mean pedometer-measured steps per day at 6 months relative to baseline, compared with the waiting list control group. The Physical Activity Loyalty scheme was deemed not to be cost-effective compared with no intervention, primarily because no additional quality-adjusted life-years were gained through the intervention. Research to better understand the mechanisms of physical activity behaviour change maintenance will help the design of future interventions. Trial registration Current Controlled Trials ISRCTN17975376. Funding This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 7, No. 15. See the NIHR Journals Library website for further project information.

Exploring individual responses to exercise training is a growing area of interest. Understanding reasons behind true observed inter-individual responses may help personalise exercise training to maximise the benefits received. While numerous factors have been explored, an often underappreciated consideration in the sport and exercise science field is the influence intraindividual variation, both in a single measurement and in response to an intervention, may have on training outcomes. Several study designs and statistical approaches are available to incorporate intra-individual variation into interventions and accordingly provide information on whether 'true' inter-individual responses are present or if they are an artefact of intraindividual variation. However, such approaches are sparingly applied. Moreover, intraindividual variation may also be important when true inter-individual response differences are present. In this perspective piece, the concept of intra-individual variation is described before briefly summarising study designs and statistical practices to account for intra-individual variation. We then outline two examples of physiological practices (stratified randomisation and prescribing exercise programmes upon training parameters) to demonstrate why sport and exercise scientists should acknowledge intra-individual variation prior to the implementation of an intervention, which potentially offers an additional explanation behind observed true inter-individual responses to training. Repeated testing pre-implementation of exercise training would conceptually provide more confident estimates of training parameters, which if utilised in a study design will help attenuate biases that may dictate inter-individual differences. Moreover, the incorporation of intra-individual differences will facilitate insights into alternative factors that may predict and/or explain true observed individual responses to an exercise training programme.

This study explored lifestyle and biological determinants of peak fat oxidation (PFO) during cycle ergometry, using duplicate measures to account for day-to-day variation. Seventy-three healthy adults (age range: 19–63 years; peak oxygen consumption ; n = 32 women]) completed trials 7–28 days apart that assessed resting metabolic rate, a resting venous blood sample, and PFO by indirect calorimetry during an incremental cycling test. Habitual physical activity (combined heart rate accelerometer) and dietary intake (weighed record) were assessed before the first trial. Body composition was assessed 2–7 days after the second identical trial by dual-energy X-ray absorptiometry scan. Multiple linear regressions were performed to identify determinants of PFO (mean of two cycle tests). A total variance of 79% in absolute PFO (g·min−1) was explained with positive coefficients for (strongest predictor), FATmax (i.e the % of that PFO occurred at), and resting fat oxidation rate (g·min−1), and negative coefficients for body fat mass (kg) and habitual physical activity level. When expressed relative to fat-free mass, 64% of variance in PFO was explained: positive coefficients for FATmax (strongest predictor), , and resting fat oxidation rate, and negative coefficients for male sex and fat mass. This duplicate design revealed that biological and lifestyle factors explain a large proportion of variance in PFO during incremental cycling. After accounting for day-to-day variation in PFO, and FATmax were strong and consistent predictors of PFO.

The maximal capacity to utilise fat (peak fat oxidation, PFO) may have implications for health and ultra-endurance performance and is commonly determined by incremental exercise tests employing 3-min stages. However, 3-min stages may be insufficient to attain steady-state gas kinetics, compromising test validity. We assessed whether 4-min stages produce steady-state gas exchange and reliable PFO estimates in adults with peak oxygen consumption < 40 mL·kg·min. Fifteen participants (9 females) completed a graded test to determine PFO and the intensity at which this occurred (FAT). Three short continuous exercise sessions (SCE) were then completed in a randomised order, involving completion of the graded test to the stage (i) preceding, (ii) equal to (SCE), or (iii) after the stage at which PFO was previously attained, whereupon participants then continued to cycle for 10 min at that respective intensity. Expired gases were sampled at minutes 3-4, 5-6, 7-8, and 9-10. Individual data showed steady-state gas exchange was achieved within 4 min during SCE. Mean fat oxidation rates were not different across time within SCE nor compared with the graded test at FAT (both p > 0.05). However, the graded test displayed poor surrogate validity (SCE, minutes 3-4 vs. 5-6, 7-8, and 9-10) and day-to-day reliability (minutes 3-4, SCE vs. graded test) to determine PFO, as evident by correlations (range: 0.47-0.83) and typical errors and 95% limits of agreement (ranges: 0.03-0.05 and ±0.09-0.15 g·min, respectively). In conclusion, intraindividual variation in PFO is substantial despite 4-min stages establishing steady-state gas exchange in individuals with low fitness. Individual assessment of PFO may require multiple assessments.