De menselijk motor : the human engine

Inauguratie Prof.dr. Luc J.C. van Loon, benoemd in de Faculty of Health Medicine and Life Sciences tot bijzonder hoogleraar ‘Fysiologie van Inspanning met bijzonder aandacht voor de rol van voeding

In vivo postprandial lipid partitioning in liver and muscle of diabetic rats is disturbed

Objective: To study in vivo lipid partitioning in insulin-resistant liver and muscle of diabetic rats using magnetic resonance spectroscopy (MRS). Methods: Four groups of n=6 male Zucker diabetic fatty rats were used for this study: obese, pre-diabetic fa/fa rats and lean, non-diabetic fa/+ littermates at the age of 6 weeks, and obese, diabetic fa/fa rats and lean, non-diabetic fa/+ littermates at the age of 12 weeks. 1H-[13C] MRS measurements were performed in liver and tibialis anterior muscle at baseline and 4, 24 and 48 h after oral administration of 1.5 g [U-13C] Algal lipid mixture per kg body weight. Results: At baseline, total lipid content was higher in fa/fa rats compared with fa/+ rats in both liver and muscle, and at both ages. Both in pre-diabetic and in diabetic fa/fa rats, hepatic lipid uptake was increased compared with non-diabetic fa/+ rats. Likewise, in muscle of diabetic fa/fa rats, lipid uptake was higher than in muscle of fa/+ rats. In contrast, lipid uptake in muscle of younger, pre-diabetic fa/fa rats was lower than in controls. Conclusion: In the pre-diabetic state, muscle appeared to be protected from massive lipid uptake, whereas lipid uptake in the liver was largely increased. In contrast, after developing full-blown diabetes, lipid uptake was highly elevated in both liver and muscle. This research was funded by a VIDI grant from the Netherlands Organisation for Scientific Research (NWO)

Characteristics of muscle fiber type are predictive of skeletal muscle mass and strength in elderly men

OBJECTIVES: To investigate the relationship between skeletal muscle fiber type-specific characteristics, circulating hormone concentrations, and skeletal muscle mass and strength in older men. DESIGN: Cross-sectional analyses. SETTING: University research center. PARTICIPANTS: Forty-one community dwelling elderly men (>/= 65). MEASUREMENTS: Leg strength (1-repetition maximum, 1RM) and whole-body and limb muscle mass were determined, and muscle fiber type composition, cross-sectional area (CSA), myonuclear content, and satellite cell (SC) content were assessed in skeletal muscle biopsy samples. In addition, blood samples were collected to determine serum testosterone, sex hormone-binding globulin, insulinlike growth factor (IGF)-1, and IGF binding protein-3 concentrations. RESULTS: Muscle mass correlated with muscle strength (0.41 </= correlation coefficient (r) </= 0.72; P < .01). Muscle fiber CSA, myonuclear content, and SC content were significantly lower in type II than in type I muscle fibers. Myonuclear and SC content were positively correlated with muscle fiber CSA. Furthermore, greater muscle fiber CSA (type I and II) was associated with greater thigh muscle area and muscle strength (0.30 </= r </= 0.45; P < .05). Testosterone concentration was positively correlated with muscle mass and muscle fiber CSA. Regression analysis showed that SC content, myonuclear content, and testosterone concentration are predictive of muscle fiber CSA. Furthermore, muscle mass and type II muscle fiber CSA are predictive of muscle strength. CONCLUSION: Skeletal muscle mass and strength in elderly men are positively correlated with muscle fiber type-specific CSA, myonuclear content, and SC content. These findings support the assumption that a decline in SC content plays an important role in age-related decline in muscle mass and strength

Maximizing postexercise muscle glycogen synthesis: carbohydrate supplementation and the application of amino acid or protein hydrolysate mixtures

Postexercise muscle glycogen synthesis is an important factor in determining the time needed to recover from prolonged exercise.This study investigated whether an increase in carbohydrate intake, ingestion of a mixture of protein hydrolysate and amino acids in combination with carbohydrate, or both results in higher postexercise muscle glycogen synthesis rates than does ingestion of 0.8 g*kg(-)(1)*h(-)(1) carbohydrate, provided at 30-min intervals.Eight trained cyclists visited the laboratory 3 times, during which a control beverage and 2 other beverages were tested. After the subjects participated in a strict glycogen-depletion protocol, muscle biopsy samples were collected. The subjects received a beverage every 30 min to ensure ingestion of 0.8 g carbohydrate*kg(-)(1)*h(-)(1) (Carb trial), 0.8 g carbohydrate*kg(-)(1)*h(-)(1) plus 0.4 g wheat protein hydrolysate plus free leucine and phenylalanine*kg(-)(1)*h(-)(1) (proven to be highly insulinotropic; Carb + Pro trial), or 1.2 g carbohydrate*kg(-)(1)*h(-)(1) (Carb + Carb trial). After 5 h, a second biopsy was taken.Plasma insulin responses in the Carb + Pro and Carb + Carb trials were higher than those in the Carb trial (88 +/- 17% and 46 +/- 18%; P &lt;0.05). Muscle glycogen synthesis was higher in both trials than in the Carb trial (35. 4 +/- 5.1 and 44.8 +/- 6.8 compared with 16.6 +/- 7.8 micromol glycosol units*g dry wt(-)(1)*h(-)(1), respectively; P &lt;0.05).Addition of a mixture of protein hydrolysate and amino acids to a carbohydrate-containing solution (at an intake of 0.8 g carbohydrate*kg(-)(1)*h(-)(1)) can stimulate glycogen synthesis. However, glycogen synthesis can also be accelerated by increasing carbohydrate intake (0.4 g*kg(-)(1)*h(-)(1)) when supplements are provided at 30-min intervals

Intramyocellular lipid content is increased after exercise in nonexercising human skeletal muscle

Intramyocellular lipid (IMCL) content has been reported to decrease after prolonged submaximal exercise in active muscle and, therefore, seems to form an important local substrate source. Because exercise leads to a substantial increase in plasma free fatty acid (FFA) availability with a concomitant increase in FFA uptake by muscle tissue, we aimed to investigate potential differences in the net changes in IMCL content between contracting and noncontracting skeletal muscle after prolonged endurance exercise. IMCL content was quantified by magnetic resonance spectroscopy in eight trained cyclists before and after a 3-h cycling protocol (55% maximal energy output) in the exercising vastus lateralis and the nonexercising biceps brachii muscle. Blood samples were taken before and after exercise to determine plasma FFA, glycerol, and triglyceride concentrations, and substrate oxidation was measured with indirect calorimetry. Prolonged endurance exercise resulted in a 20.4 ± 2.8% (P <0.001) decrease in IMCL content in the vastus lateralis muscle. In contrast, we observed a substantial (37.9 ± 9.7%; P <0.01) increase in IMCL content in the less active biceps brachii muscle. Plasma FFA and glycerol concentrations were substantially increased after exercise (from 85 ± 6 to 1,450 ± 55 and 57 ± 11 to 474 ± 54 µM, respectively; P <0.001), whereas plasma triglyceride concentrations were decreased (from 1,498 ± 39 to 703 ± 7 µM; P <0.001). IMCL is an important substrate source during prolonged moderate-intensity exercise and is substantially decreased in the active vastus lateralis muscle. However, prolonged endurance exercise with its concomitant increase in plasma FFA concentration results in a net increase in IMCL content in less active muscle

Оптимизация предсоревновательного состояния в единоборствах у юношей

Основное отличие соревновательной деятельности в различных видах единоборств, по мнению специалистов, заключается в том, что все технико-тактические действия выполняются на очень высокой скорости, что позволяет говорить о первичности таких качеств как быстрота реагирования и скоростные возможности нервно-мышечного аппарата. Построение тренировочных занятий в режимах субмаксимальной и максимальной интенсивности дает положительный эффект, но его длительность далеко не бесконечна. Поэтому спортсмены, которые добились высоких результатов в возрасте 17-20 лет, в последующем, несмотря на достаточный арсенал эффективных технико-тактических действий и большой соревновательный опыт уступают ведущие позиции молодым спортсменам

Post-exercise protein synthesis rates are only marginally higher in type I compared with type II muscle fibres following resistance-type exercise.

We examined the effect of an acute bout of resistance exercise on fractional muscle protein synthesis rates in human type I and type II muscle fibres. After a standardised breakfast (31 ± 1 kJ kg(−1) body weight, consisting of 52 Energy% (En%) carbohydrate, 34 En% protein and 14 En% fat), 9 untrained men completed a lower-limb resistance exercise bout (8 sets of 10 repetitions leg press and leg extension at 70% 1RM). A primed, continuous infusion of l-[ring-(13)C(6)]phenylalanine was combined with muscle biopsies collected from both legs immediately after exercise and after 6 h of post-exercise recovery. Single muscle fibres were dissected from freeze-dried biopsies and stained for ATPase activity with pre-incubation at a pH of 4.3. Type I and II fibres were separated under a light microscope and analysed for protein-bound l-[ring-(13)C(6)]phenylalanine labelling. Baseline (post-exercise) l-[ring-(13)C(6)]phenylalanine muscle tissue labelling, expressed as (∂(13)C/(12)C), averaged −32.09 ± 0.28, −32.53 ± 0.10 and −32.02 ± 0.16 in the type I and II muscle fibres and mixed muscle, respectively (P = 0.14). During post-exercise recovery, muscle protein synthesis rates were marginally (8 ± 2%) higher in the type I than type II muscle fibres, at 0.100 ± 0.005 versus 0.094 ± 0.005%/h, respectively (P < 0.05), whereby rates of mixed muscle protein were 0.091 ± 0.005%/h. Muscle protein synthesis rates following resistance-type exercise are only marginally higher in type I compared with type II muscle fibres

Role of dietary protein in post-exercise muscle reconditioning

Dietary protein ingestion after exercise stimulates muscle protein inhibits protein breakdown and, as such, stimulates net muscle protein following resistance as well as endurance type exercise. Protein and/or immediately after exercise has been suggested to facilitate the muscle adaptive response to each exercise session, resulting in more muscle reconditioning. A few basic guidelines can be defined with regard preferred type and amount of dietary protein and the timing by which should be ingested. Whey protein seems to be most effective to increase post-exercise muscle protein synthesis rates. This is likely attributed rapid digestion and absorption kinetics and specific amino acid Ingestion of approximately 20 g protein during and/or immediately after is sufficient to maximize post-exercise muscle protein synthesis rates. Additional ingestion of large amounts of carbohydrate does not further post-exercise muscle protein synthesis rates when ample protein is ingested. Dietary protein should be ingested during and/or immediately cessation of exercise to allow muscle protein synthesis rates to reach levels. Future research should focus on the impact of the timing of provision throughout the day on the adaptive response to more prolonged training. Copyright (c) 2013 Nestec Ltd., Vevey/S. Karger AG, Basel