Intramuscular triglycerides (IMTG) are a key substrate during prolonged exercise, but little is known about the rate of IMTG resynthesis in the postexercise period. We investigated the hypothesis that the distribution of the lipid droplet (LD)-associated perilipin (PLIN) proteins is linked to IMTG storage following exercise. Fourteen elite male triathletes (27 ± 1 yr, 66.5 ± 1.3 mL·kg−1·min−1) completed 4 h of moderate-intensity cycling. During the first 4 h of recovery, subjects received either carbohydrate or H2O, after which both groups received carbohydrate. Muscle biopsies collected pre- and postexercise and 4 and 24 h postexercise were analyzed using confocal immunofluorescence microscopy for fiber type-specific IMTG content and PLIN distribution with LDs. Exercise reduced IMTG content in type I fibers (−53%, P = 0.002), with no change in type IIa fibers. During the first 4 h of recovery, IMTG content increased in type I fibers ( P = 0.014), but was not increased more after 24 h, where it was similar to baseline levels in both conditions. During recovery the number of LDs labeled with PLIN2 (70%), PLIN3 (63%), and PLIN5 (62%; all P < 0.05) all increased in type I fibers. Importantly, the increase in LDs labeled with PLIN proteins only occurred at 24 h postexercise. In conclusion, IMTG resynthesis occurs rapidly in type I fibers following prolonged exercise in highly trained individuals. Furthermore, increases in IMTG content following exercise preceded an increase in the number of LDs labeled with PLIN proteins. These data, therefore, suggest that the PLIN proteins do not play a key role in postexercise IMTG resynthesis.

Despite over 50 years of research, a comprehensive understanding of how intramuscular triglyceride (IMTG) is stored in skeletal muscle and its contribution as a fuel during exercise is lacking. Immunohistochemical techniques provide information on IMTG content and lipid droplet (LD) morphology on a fibre type and subcellular-specific basis, and the lipid dye Oil Red O (ORO) is commonly used to achieve this. BODIPY 493/503 (BODIPY) is an alternative lipid dye with lower background staining and narrower emission spectra. Here we provide the first quantitative comparison of BODIPY and ORO for investigating exercise-induced changes in IMTG content and LD morphology on a fibre type and subcellular-specific basis. Estimates of IMTG content were greater when using BODIPY, which was predominantly due to BODIPY detecting a larger number of LDs, compared to ORO. The subcellular distribution of intramuscular lipid was also dependent on the lipid dye used; ORO detects a greater proportion of IMTG in the periphery (5 μm below cell membrane) of the fibre, whereas IMTG content was higher in the central region using BODIPY. In response to 60 min moderate-intensity cycling exercise, IMTG content was reduced in both the peripheral (− 24%) and central region (− 29%) of type I fibres (P < 0.05) using BODIPY, whereas using ORO, IMTG content was only reduced in the peripheral region of type I fibres (− 31%; P < 0.05). As well as highlighting some methodological considerations herein, our investigation demonstrates that important differences exist between BODIPY and ORO for detecting and quantifying IMTG on a fibre type and subcellular-specific basis.

Purpose: To quantify net glycogen utilisation in the vastus lateralis (VL) and gastrocnemius (G) of male (n=11) and female (n=10) recreationally active runners during three outdoor training sessions. Methods: After 2 days standardisation of carbohydrate (CHO) intakes (6 g.kg -1 body mass per day), glycogen was assessed before and after 1) a 10-mile road run (10-mile) at lactate threshold, 2) 8 x 800 m track intervals (8 x 800 m) at velocity at V O2max and 3) 3 x 10 minute track intervals (3 x 10 min) at lactate turnpoint. Results: Resting glycogen concentration was lower in the G of females compared with males (P<0.001) though no sex differences were apparent in the VL (P=0.40). Within the G and VL of males, net glycogen utilisation differed between training sessions where 10-mile was greater than both track sessions (all comparisons, P<0.05). In contrast, net glycogen utilisation in females was not different between training sessions in either muscle (all comparisons, P>0.05). Net glycogen utilisation was greater in males than females in both VL (P=0.02) and G (P=0.07) during the 10-mile road run. With the exception of males during the 3 x 10 min protocol (P=0.28), greater absolute glycogen utilisation was observed in the G versus the VL muscle in both males and females and during all training protocols (all comparisons, P<0.05). Conclusion: Data demonstrate 1) prolonged steady state running necessitates a greater glycogen requirement than shorter but higher intensity track running sessions, 2) females display evidence of reduced resting muscle glycogen concentration and net muscle glycogen utilisation when compared with males and 3), net glycogen utilisation is higher in the gastrocnemius muscle compared with the vastus lateralis.

Muscle glycogen and intramuscular triglycerides (IMTG, stored in lipid droplets) are important energy substrates during prolonged exercise.r Exercise-induced changes in lipid droplet (LD) morphology (i.e. LD size and number) have not yet been studied under nutritional conditions typically adopted by elite endurance athletes, that is, after carbohydrate (CHO) loading and CHO feeding during exercise.r We report for the first time that exercise reduces IMTG content in both central and peripheral regions of type I and IIa fibres, reflective of decreased LD number in both fibre types whereas reductions in LD size were exclusive to type I fibres.r Additionally, CHO feeding does not alter subcellular IMTG utilisation, LD morphology or muscle glycogen utilisation in type I or IIa/II fibres. r In the absence of alterations to muscle fuel selection, CHO feeding does not attenuate cell signalling pathways with regulatory roles in mitochondrial biogenesis.

BackgroundSocial media use (SMU) is increasingly widespread. More recently, SMU has been associated with increases in disordered eating; however, few qualitative studies have explored this issue in nutrition and dietetics students specifically, where susceptibility to disordered eating may be particularly high. The present study therefore aimed to investigate the perceived impact of SMU on disordered eating in nutrition and dietetics students.MethodsOne‐to‐one, in‐depth, semi‐structured interviews were conducted with nutrition and dietetics students from universities across the UK. Interviews explored students’ views on the potential influence of SMU on their eating‐related thoughts, feelings and behaviours. Data were thematically analysed to identify key themes.ResultsThe findings suggested that SMU may provide students with a useful tool for the exploration of new recipes, ingredients and health‐related information, thus enabling them to improve their eating behaviour and diet quality. However, students also showed high levels of objective awareness regarding the problems associated with SMU, including the presence of misinformation, body image dissatisfaction, social pressures and disordered eating. Interestingly, despite enabling them to detect sources of misinformation, students also discussed the negative impact that their course had on their eating habits, suggesting course content may be an additional risk factor for the development of disordered eating for this particular group.ConclusionsFuture research should investigate ways to mitigate the negative impact of SMU and course content on disordered eating in nutrition and dietetics students.