The absence of GLUT4 severely impairs basal glucose uptake in vivo, but does not alter glucose homeostasis or circulating insulin. Glucose uptake in isolated contracting skeletal muscle (MGU) is also impaired by the absence of GLUT4, and onset of muscle fatigue is hastened. Whether the body can compensate and preserve glucose homeostasis during exercise, as it does in the basal state, is unknown. One aim was to test the effectiveness of glucoregulatory compensation for the absence of GLUT4 in vivo. The absence of GLUT4 was also used to further define the role of hexokinase (HK) II, which catalyses glucose phosphorylation after it is transported in the cell. HK II increases MGU during exercise, as well as exercise endurance. In the absence of GLUT4, HK II expression will not affect MGU. A second aim was to test whether, in the absence of GLUT4, HK II retains its ability to increase exercise endurance. Wild-type (WT), GLUT4 null (GLUT4 −/− ), and GLUT4 null overexpressing HK II (GLUT4 −/− HK Tg ) mice were studied using a catheterized mouse model that allows blood sampling and isotope infusions during treadmill exercise. The impaired capacity of working muscle to take up glucose in GLUT4 −/− is partially offset by an exaggerated increase in the glucagon : insulin ratio, increased liver glucose production, hyperglycaemia, and a greater capillary density in order to increase the delivery of glucose to the exercising muscle of GLUT4 −/− . Hearts of GLUT4 −/− also exhibited a compensatory increase in HK II expression and a paradoxical increase in glucose uptake. Exercise tolerance was reduced in GLUT4 −/− compared to WT. As expected, MGU in GLUT4 −/− HK Tg was the same as in GLUT4 −/− . However, HK II overexpression retained its ability to increase exercise endurance. In conclusion, unlike the basal state where glucose homeostasis is preserved, hyperglycaemia results during exercise in GLUT4 −/− due to a robust stimulation of liver glucose release in the face of severe impairments in MGU. Finally, studies in GLUT4 −/− HK Tg show that HK II improves exercise tolerance, independent of its effects on MGU.

Hexokinase (HK) II content is elevated in fatigue resistant muscle fibres and exercise trained muscle. The aim of this study was to determine if exercise capacity is dependent on muscle HK protein content. C57Bl/6 mice with a 50% HK knockout (HK +/− ), no genetic manipulation (wild-type, WT) and an ∼3-fold HK overexpression (HK Tg ) were tested. Mice (n = 12/group) completed both a maximal oxygen consumption (V O 2 ,max ) test and an endurance capacity test (run at ∼75%V O 2 ,max ) on an enclosed treadmill equipped to measure gas exchange. Arterial and venous catheters were surgically implanted into separate groups of mice (n = 9-11/group) in order to measure an index of muscle glucose uptake (R g ) during 30 min of treadmill exercise. Maximum work rate (0.95 ± 0.05, 1.00 ± 0.04 and 1.06 ± 0.07 kg m min −1 ),V O 2 ,max (137 ± 3, 141 ± 4 and 141 ± 5 ml kg −1 min −1 ) and maximal respiratory exchange ratio (1.04 ± 0.02, 1.00 ± 0.03 and 1.04 ± 0.04) were similar in HK +/− , WT and HK Tg , respectively. Exercise endurance capacity (measured as time to exhaustion) increased as HK content increased (55 ± 11, 77 ± 5 and 98 ± 9 min) and this was related to R g measured in mice during 30 min of exercise (13 ± 2, 24 ± 5 and 42 ± 5 µmol (100 g) −1 min −1 ). Muscle glycogen in sedentary HK +/− mice and HK +/− mice following 30 min of exercise were significantly lower than in HK Tg and WT mice. However, the net exercise-induced muscle glycogen breakdown was equal in the three genotypes. In summary, HK protein content within the range studied (a) was not associated with a difference in the capacity to perform maximal intensity exercise, (b) was a powerful determinant of the ability to sustain moderate intensity exercise, as reducing HK content impaired endurance and increasing HK content enhanced endurance, and (c) although directly related to exercise endurance, was not a determinant of net muscle glycogen usage during exercise. In conclusion, adaptations that increase HK protein content and/or functional activity such as regular exercise contribute to increased muscular endurance.

Abstract:The importance of ergonomics across several scientific domains, including biomechanics, psychology, sociology, and physiology, have been extensively explored. However, the role of other factors that may influence the health and productivity of workers, such as nutrition, is generally overlooked. Nutra-ergonomics describes the interface between workers, their work environment, and performance in relation to their nutritional status. It considers nutrition to be an integral part of a safe and productive workplace that encompasses physical and mental health as well as the long-term wellbeing of workers. This review explores the knowledge, awareness, and common practices of nutrition, hydration, stimulants, and fortified product use employed prior to physical employment standards testing and within the workplace. The influence of these nutra-ergonomic strategies on physical employment standards, worker safety, and performance will be examined. Further, the roles, responsibilities, and implications for the applicant, worker, and the employer will be discussed within the context of nutra-ergonomics, with reference to the provision and sustainability of an environment conducive to optimize worker health and wellbeing. Beyond physical employment standards, workplace productivity, and performance, the influence of extended or chronic desynchronization (irregular or shift work) in the work schedule on metabolism and long-term health, including risk of developing chronic and complex diseases, is discussed. Finally, practical nutra-ergonomic strategies and recommendations for the applicant, worker, and employer alike will be provided to enhance the short-and long-term safety, performance, health, and wellbeing of workers.

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Objectives The prevalence of household food insecurity increases in the summer when school meals are no longer accessible, which can negatively impact children's health and wellbeing. Summer food programs, such as I Can for Kids (IC4K) in Calgary, Alberta, Canada, aim to reduce food insecurity in low income households with school-aged children during the summer months. Qualitative studies have not yet examined whether or how grocery gift cards (GGC) can reduce experiences of food insecurity among low-income households. We explored recipients’ and agency staff experiences and perceived outcomes of receiving or distributing GGC from IC4K. Methods This study used qualitative descriptive methodology. Data generation and analysis were guided by Freedman et al's theoretical framework of nutritious food access. Semi-structured interviews were conducted between August and November 2020 with 38 primary caregivers (i.e., GGC recipients) and 17 agency staff who distributed GGC. Directed content analysis was used to analyze the data from each set of interviews using a deductive-inductive approach. Codes were combined into themes that summarized GGC recipients’ and agency staff's experiences and perceived outcomes of receiving or distributing GGC, and feedback to improve program delivery. Results Three themes were generated from the data. The first theme was Financial Relief and reflected increased self-efficacy, improved diet quality, and reduced household stress from receiving GGC. The second theme was Social Connectedness and described enriched family relationships, enhanced rapport between staff and recipients, and increased recipient social capital. The last theme was Program Enhancements and described feedback to improve program delivery by extending program duration, increasing strategic direction to staff on GGC distribution, and additional promotional efforts to increase awareness of GGC availability. Conclusions GGC recipients and agency staff perceived that GGC offered financial relief and enhanced social connections for recipients, and suggested areas for program improvements. Study findings can inform improvements to summer food programs that deliver GGC to reduce food insecurity among low-income households in the summer. Funding Sources Funding provided by the O'Brien Institute for Public Health at the University of Calgary.

Objectives Household food insecurity negatively affects children's diet quality, physical and mental health, and academic performance. I Can for Kids’ (IC4K) grocery gift card (GGC) program provides GGC to low-income households with school-aged children at risk of household food insecurity in Calgary, Canada. This study described program recipients’ and facilitators’ experiences and perceived outcomes of accessing or facilitating IC4K's GGC program. Methods This study used qualitative descriptive methodology. Data generation and analysis were guided by Freedman et al's theoretical framework of nutritious food access. Semi-structured interviews were conducted between August and November 2020 with 37 program recipients and 17 program facilitators who were purposively recruited. Directed content analysis was used to analyze the data using a deductive-inductive approach. Codes were combined into subthemes and themes that summarized program recipients’ and facilitators’ experiences and perceived outcomes of receiving or distributing GGC, and suggestions to improve IC4K's GGC program. Results Three themes were generated from the data: 1) IC4K's GGC program promoted a sense of autonomy and dignity among program recipients; 2) recipients used GGC to purchase foods that improved household dietary patterns and food skills, including foods that aligned with health-related food needs and cultural foodways and; 3) program logistical strengths and limitations, including the program's impact on facilitators’ connection with clients and their workload, experiences of differential access to GGC among recipients, and the importance of increasing program awareness to reach more food insecure households. Conclusions IC4K's GGC program enhanced recipients’ access to nutritious foods, had positive impacts on household finances and diet quality, as well as recipients’ social health and emotional wellbeing. However, differential access to GGC among recipients was also identified. Study findings were used to inform three recommendations to improve IC4K's GGC program: 1) increase the number of GGC that recipients can receive; 2) establish concrete guidelines governing GGC distribution and; 3) increase program awareness. Funding Sources O'Brien Institute for Public Health.

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