The present study was designed to determine postexercise muscle protein synthesis and whole body protein balance following the combined ingestion of carbohydrate with or without protein and/or free leucine. Eight male subjects were randomly assigned to three trials in which they consumed drinks containing either carbohydrate (CHO), carbohydrate and protein (CHO+PRO), or carbohydrate, protein, and free leucine (CHO+PRO+Leu) following 45 min of resistance exercise. A primed, continuous infusion of l-[ ring-¹³C₆]phenylalanine was applied, with blood samples and muscle biopsies collected to assess fractional synthetic rate (FSR) in the vastus lateralis muscle as well as whole body protein turnover during 6 h of postexercise recovery. Plasma insulin response was higher in the CHO+PRO+Leu compared with the CHO and CHO+PRO trials (+240 ± 19% and +77 ± 11%, respectively, P < 0.05). Whole body protein breakdown rates were lower, and whole body protein synthesis rates were higher, in the CHO+PRO and CHO+PRO+Leu trials compared with the CHO trial ( P < 0.05). Addition of leucine in the CHO+PRO+Leu trial resulted in a lower protein oxidation rate compared with the CHO+PRO trial. Protein balance was negative during recovery in the CHO trial but positive in the CHO+PRO and CHO+PRO+Leu trials. In the CHO+PRO+Leu trial, whole body net protein balance was significantly greater compared with values observed in the CHO+PRO and CHO trials ( P < 0.05). Mixed muscle FSR, measured over a 6-h period of postexercise recovery, was significantly greater in the CHO+PRO+Leu trial compared with the CHO trial (0.095 ± 0.006 vs. 0.061 ± 0.008%/h, respectively, P < 0.05), with intermediate values observed in the CHO+PRO trial (0.0820 ± 0.0104%/h). We conclude that coingestion of protein and leucine stimulates muscle protein synthesis and optimizes whole body protein balance compared with the intake of carbohydrate only.

Recent evidence suggests that intramyocellular lipid (IMCL) accretion is associated with obesity and the development of insulin resistance and/or type 2 diabetes. However, trained endurance athletes are markedly insulin sensitive, despite an elevated mixed muscle lipid content. In an effort to explain this metabolic paradox, we compared muscle fiber type-specific IMCL storage between populations known to have elevated IMCL deposits. Immunofluorescence microscopy was performed on muscle biopsies obtained from eight highly trained endurance athletes, eight type 2 diabetes patients, and eight overweight, sedentary men after an overnight fast. Mixed muscle lipid content was substantially greater in the endurance athletes (4.0 ± 0.4% area lipid stained) compared with the diabetes patients and the overweight men (2.3 ± 0.4 and 2.2 ± 0.5%, respectively). More than 40% of the greater mixed muscle lipid content was attributed to a higher proportion type I muscle fibers (62 ± 8 vs. 38 ± 3 and 33 ± 7%, respectively), which contained 2.8 ± 0.3-fold more lipid than the type II fibers. The remaining difference was explained by a significantly greater IMCL content in the type I muscle fibers of the trained athletes. Differences in IMCL content between groups or fiber types were accounted for by differences in lipid droplet density, not lipid droplet size. IMCL distribution showed an exponential increase in lipid content from the central region toward the sarcolemma, which was similar between groups and fiber types. In conclusion, IMCL contents can be substantially greater in trained endurance athletes compared with overweight and/or type 2 diabetes patients. Because structural characteristics and intramyocellular distribution of lipid aggregates seem to be similar between groups, we conclude that elevated IMCL deposits are unlikely to be directly responsible for inducing insulin resistance.

The purpose of this study was to examine the impact of acute high-intensity interval training (HIIT) compared with continuous moderate-intensity (CMI) exercise on postprandial hyperglycemia in overweight or obese adults. Ten inactive, overweight or obese adults (41 ± 11 yrs, BMI = 36 ± 7 kg/m²) performed an acute bout of HIIT (10 × 1 min at approximately 90% peak heart rate (HR_peak) with 1-min recovery periods) or matched work CMI (30 min at approximately 65% HR_peak) in a randomized, counterbalanced fashion. Exercise was performed 2 h after breakfast, and glucose control was assessed by continuous glucose monitoring under standardized dietary conditions over 24 h. Postprandial glucose (PPG) responses to lunch, dinner, and the following day’s breakfast were analyzed and compared with a no-exercise control day. Exercise did not affect the PPG responses to lunch, but performing both HIIT and CMI in the morning significantly reduced the PPG incremental area under the curve (AUC) following dinner when compared with control (HIIT = 110 ± 35, CMI = 125 ± 34, control = 162 ± 46 mmol/L × 2 h, p < 0.05). The PPG AUC (HIIT = 125 ± 53, CMI = 186 ± 55, control = 194 ± 96 mmol/L × 2 h) and the PPG spike (HIIT = Δ2.1 ± 0.9, CMI = Δ3.0 ± 0.9, control = Δ3.0 ± 1.5 mmol/l) following breakfast on the following day were significantly lower following HIIT compared with both CMI and control (p < 0.05). Absolute AUC and absolute glucose spikes were not different between HIIT, CMI, or control for any meal (p > 0.05 for all). We conclude that a single session of HIIT has greater and more lasting effects on reducing incremental PPG when compared with CMI.

Background: The progressive loss of skeletal muscle mass with aging is attributed to a disruption in the regulation of skeletal muscle protein turnover. Objective: We investigated the effects on whole-body protein balance and mixed-muscle protein synthesis rates of the ingestion of carbohydrate with or without protein and free leucine after simulated activities of daily living. Design: Eight elderly (75 ± 1 y) and 8 young (20 ± 1 y) lean men were randomly assigned to 2 crossover experiments in which they consumed either carbohydrate (CHO) or carbohydrate plus protein and free leucine (CHO+Pro+Leu) after performing 30 min of standardized activities of daily living. Primed, continuous infusions with l-[ring-¹³C₆]phenylalanine and l-[ring-²H₂]tyrosine were applied, and blood and muscle samples were collected to assess whole-body protein turnover and the protein fractional synthetic rate in the vastus lateralis muscle over a 6-h period. Results: Whole-body phenylalanine and tyrosine flux were significantly higher in the young than in the elderly men (P < 0.01). Protein balance was negative in the CHO experiment but positive in the CHO+Pro+Leu experiment in both groups. Mixed-muscle protein synthesis rates were significantly greater in the CHO+Pro+Leu than in the CHO experiment in both the young (0.082 ± 0.005%/h and 0.060 ± 0.005%/h, respectively; P < 0.01) and the elderly (0.072 ± 0.006%/h and 0.043 ± 0.003%/h, respectively; P < 0.01) subjects, with no significant differences between groups. Conclusions: Co-ingestion of protein and leucine with carbohydrate after activities of daily living improves whole-body protein balance, and the increase in muscle protein synthesis rates is not significantly different between lean young and elderly men.

Glycemic instability is a severely underestimated problem in type 2 diabetes treatment. Therapeutic targets should aim to reduce postprandial blood glucose excursions. Exercise prescription can effectively improve glucose homeostasis and reduce the risk of cardiovascular complications. To assess the impact of a single, isoenergetic bout of low- (LI) and high-intensity (HI) exercise on the prevalence of hyperglycemia throughout the subsequent 24-h postexercise period in longstanding type 2 diabetes patients. Nine sedentary, male type 2 diabetes patients (age = 57 +/- 2 yr, body mass index = 29.0 +/- 1.0 kg x m(-2), Wmax = 2.2 +/- 0.2 W x kg(-1) body weight) were selected to participate in a randomized crossover study. Subjects performed an isoenergetic bout of endurance-type exercise for 60 min at 35% Wmax (LI) or 30 min at 70% Wmax (HI) or no exercise at all (NE). Thereafter, glycemic control was assessed during the subsequent 24-h postexercise period by continuous glucose monitoring under strict dietary standardization but otherwise free-living conditions. Average 24-h glucose concentrations were reduced after the LI exercise bout (7.8 +/- 0.9 mmol x L(-1)) when compared with the control experiment (9.4 +/- 0.8 mmol x L(-1); P < 0.05). The HI exercise bout did not significantly lower mean glucose concentrations (8.7 +/- 0.7 mmol x L(-1); P = 0.14). Hyperglycemia was prevalent for as much as 35% +/- 9% throughout the day (NE). A single bout of exercise reduced the prevalence of hyperglycemia by 50% +/- 4% (P < 0.05) and 19% +/- 9% (P = 0.13) in the LI and HI exercise experiments, respectively. A single bout of LI, as opposed to HI, exercise substantially reduces the prevalence of hyperglycemia throughout the subsequent 24-h postexercise period in longstanding type 2 diabetes patients.

Exercise represents an effective interventional strategy to improve glycaemic control in type 2 diabetes patients. However, the impact of exercise intensity on the benefits of exercise training remains to be established. In the present study, we compared the clinical benefits of 6 months of continuous low- to moderate-intensity exercise training with those of continuous moderate- to high-intensity exercise training, matched for energy expenditure, in obese type 2 diabetes patients. Fifty male obese type 2 diabetes patients (age 59 ± 8 years, BMI 32 ± 4 kg/m²) participated in a 6 month continuous endurance-type exercise training programme. All participants performed three supervised exercise sessions per week, either 55 min at 50% of whole body peak oxygen uptake \( \left( {\mathop V\limits^{ \cdot } {\text{O}}_{{2{\text{peak}}}} } \right) \) (low to moderate intensity) or 40 min at 75% of \( \mathop V\limits^{ \cdot } {\text{O}}_{{2{\text{peak}}}} \) (moderate to high intensity). Oral glucose tolerance, blood glycated haemoglobin, lipid profile, body composition, maximal workload capacity, whole body and skeletal muscle oxidative capacity and skeletal muscle fibre type composition were assessed before and after 2 and 6 months of intervention. The entire 6 month intervention programme was completed by 37 participants. Continuous endurance-type exercise training reduced blood glycated haemoglobin levels, LDL-cholesterol concentrations, body weight and leg fat mass, and increased \( \mathop V\limits^{ \cdot } {\text{O}}_{{2{\text{peak}}}} \), lean muscle mass and skeletal muscle cytochrome c oxidase and citrate synthase activity (p < 0.05). No differences were observed between the groups training at low to moderate or moderate to high intensity. When matched for energy cost, prolonged continuous low- to moderate-intensity endurance-type exercise training is equally effective as continuous moderate- to high-intensity training in lowering blood glycated haemoglobin and increasing whole body and skeletal muscle oxidative capacity in obese type 2 diabetes patients. ISRCTN32206301 None