A morphometrical comparison of right and left whole human vastus lateralis muscle: how to reduce sampling errors in biopsy techniques

In studies of the effects of different training programmes, one muscle--most commonly the vastus lateralis--is used for the experiment while the contralateral muscle serves as a control, at the same time as muscle biopsies are taken from both sides. In order to increase the reliability of such studies, the sources and the magnitude of the sampling errors in the biopsy techniques need to be assessed in detail. In this study, cross-sections of whole right and left vastus lateralis muscle from six young sedentary right-handed men were prepared, and the total number and size of fibres and the proportion of the different fibre types were calculated. A significant difference (P less than 0.05-P less than 0.001) between the right and the left muscle was found for at least one of the three variables in each of the six men, but there was no systematic difference and, therefore, no significant right-left difference for the whole group. The maximum difference between the right and the left side for the mean fibre size was 25% and for the fibre type proportion 5%; these differences are much smaller than the known variation within individual muscles. In conclusion, any study involving biopsies from both the right and the left vastus lateralis may use either muscle for the experiment while the contralateral muscle serves as a control without leading to systematic sampling error, whereas the errors involved in taking small samples from each muscle are much more important to control and to reduce

Effects of soluble milk protein or casein supplementation on muscle fatigue following resistance training program: a randomized, double-blind, and placebo-controlled study

International audienceBackground: The effects of protein supplementation on muscle thickness, strength and fatigue seem largely dependent on its composition. The current study compared the effects of soluble milk protein, micellar casein, and a placebo on strength and fatigue during and after a resistance training program. Methods: Sixty-eight physically active men participated in this randomized controlled trial and underwent 10 weeks of lower-body resistance training. Participants were randomly assigned to the Placebo (PLA), Soluble Milk Protein (SMP, with fast digestion rate) or Micellar Casein (MC, with slow digestion rate) group. During the 10-week training period, participants were instructed to take 30 g of the placebo or protein twice a day, or three times on training days. Tests were performed on quadriceps muscles at inclusion (PRE), after 4 weeks (MID) and after 10 weeks (POST) of training. They included muscle endurance (maximum number of repetitions during leg extensions using 70% of the individual maximal load), fatigue (decrease in muscle power after the endurance test), strength, power and muscle thickness. Results: Muscle fatigue was significantly lower (P < 0.05) in the SMP group at MID and POST (-326.8 +/- 114.1 W and -296.6 +/- 130.1 W, respectively) as compared with PLA (-439.2 +/- 153.9 W and -479.2 +/- 138.1 W, respectively) and MC (-415.1 +/- 165.1 W and -413.7 +/- 139.4 W, respectively). Increases in maximal muscle power, strength, endurance and thickness were not statistically different between groups. Conclusions: The present study demonstrated that protein composition has a large influence on muscular performance after prolonged resistance training. More specifically, as compared with placebo or micellar casein, soluble milk protein (fast digestible) appeared to significantly reduce muscle fatigue induced by intense resistance exercise

Changes in plasma phenylalanine, isoleucine, leucine, and valine are associated with significant changes in intracranial pressure and jugular venous oxygen saturation in patients with severe traumatic brain injury

Changes in plasma aromatic amino acids (AAA = phenylalanine, tryptophan, tyrosine) and branched chain amino acids (BCAA = isoleucine, leucine, valine) levels possibly influencing intracranial pressure (ICP) and cerebral oxygen consumption (SjvO(2)) were investigated in 19 sedated patients up to 14 days following severe traumatic brain injury (TBI). Compared to 44 healthy volunteers, jugular venous plasma BCAA were significantly decreased by 35% (p < 0.001) while AAA were markedly increased in TBI patients by 19% (p < 0.001). The BCAA to AAA ratio was significantly decreased by 55% (p < 0.001) which persisted during the entire study period. Elevated plasma phenylalanine was associated with decreased ICP and increased SjvO(2), while higher plasma isoleucine and leucine levels were associated with increased ICP and higher plasma leucine and valine were linked to decreased SjvO(2). The amount of enterally administered amino acids was associated with significantly increased plasma levels with the exception of phenylalanine. Contrary to the initial assumption that elevated AAA and decreased BCAA levels are detrimental, increased plasma phenylalanine levels were associated with beneficial signs in terms of decreased ICP and reduced cerebral oxygen consumption reflected by increased SjvO(2); concomitantly, elevated plasma isoleucine and leucine levels were associated with increased ICP while leucine and valine were associated with decreased SjvO(2) following severe TBI, respectively. The impact of enteral nutrition on this observed pattern must be examined prospectively to determine if higher amounts of phenylalanine should be administered to promote beneficial effects on brain metabolism and if normalization of plasma BCAA levels is without cerebral side effects