Skeletal Muscle Fiber Adaptations Following Resistance Training Using Repetition Maximums or Relative Intensity.

The purpose of the study was to compare the physiological responses of skeletal muscle to a resistance training (RT) program using repetition maximum (RM) or relative intensity (RI). Fifteen well-trained males underwent RT 3 d·wk for 10 weeks in either an RM group ( = 8) or RI group ( = 7). The RM group achieved a relative maximum each day, while the RI group trained based on percentages.

Preliminary Investigation Into the Effect of ACTN3 and ACE Polymorphisms on Muscle and Performance Characteristics.

Wagle, JP, Carroll, KM, Cunanan, AJ, Wetmore, A, Taber, CB, DeWeese, BH, Sato, K, Stuart, CA, and Stone, MH. Preliminary investigation into the effect of ACTN3 and ACE polymorphisms on muscle and performance characteristics. J Strength Cond Res 35(3): 688-694, 2021-The purpose of this investigation was to explore the phenotypic and performance outcomes associated with ACTN3 and ACE polymorphisms.

Repetition-to-Repetition Differences Using Cluster and Accentuated Eccentric Loading in the Back Squat.

The current investigation was an examination of the repetition-to-repetition magnitudes and changes in kinetic and kinematic characteristics of the back squat using accentuated eccentric loading (AEL) and cluster sets. Trained male subjects (age = 26.1 ± 4.

Accentuated Eccentric Loading and Cluster Set Configurations in the Back Squat: A Kinetic and Kinematic Analysis.

Wagle, JP, Cunanan, AJ, Carroll, KM, Sams, ML, Wetmore, A, Bingham, GE, Taber, CB, DeWeese, BH, Sato, K, Stuart, CA, and Stone, MH. Accentuated eccentric loading and cluster set configurations in the back squat: a kinetic and kinematic analysis. J Strength Cond Res 35(2): 420-427, 2021-This study examined the kinetic and kinematic differences between accentuated eccentric loading (AEL) and cluster sets in trained male subjects (age = 26.

Comparison of the Relationship between Lying and Standing Ultrasonography Measures of Muscle Morphology with Isometric and Dynamic Force Production Capabilities.

The purpose of the current study was (1) to examine the differences between standing and lying measures of vastus lateralis (VL), muscle thickness (MT), pennation angle (PA), and cross-sectional area (CSA) using ultrasonography; and (2) to explore the relationships between lying and standing measures with isometric and dynamic assessments of force production-specifically peak force, rate of force development (RFD), impulse, and one-repetition maximum back squat. Fourteen resistance-trained subjects (age = 26.8 ± 4.

Divergent Performance Outcomes Following Resistance Training Using Repetition Maximums or Relative Intensity.

Purpose: To compare repetition maximum (RM) to relative intensity using sets and repetitions (RISR) resistance training on measures of training load, vertical jump, and force production in well-trained lifters.

Methods: Fifteen well-trained (isometric peak force = 4403.61 [664.

Muscle hypertrophy in prediabetic men after 16 wk of resistance training.

Resistance training of healthy young men typically results in muscle hypertrophy and a shift in vastus lateralis composition away from type IIx fibers to an increase in IIa fiber content. Our previous studies of 8 wk of resistance training found that many metabolic syndrome men and women paradoxically increased IIx fibers with a decrease in IIa fibers. To confirm the hypothesis that obese subjects might have muscle remodeling after resistance training very different from healthy lean subjects, we subjected a group of nine obese male volunteers to progressive resistance training for a total of 16 wk.

Effects of Short-Term Free-Weight and Semiblock Periodization Resistance Training on Metabolic Syndrome.

South, MA, Layne, AS, Stuart, CA, Triplett, NT, Ramsey, MW, Howell, ME, Sands, WA, Mizuguchi, S, Hornsby, WG, Kavanaugh, AA, and Stone, MH. Effects of short-term free-weight and semiblock periodization resistance training on metabolic syndrome. J Strength Cond Res 30(10): 2682-2696, 2016-The effects of short-term resistance training on performance and health variables associated with prolonged sedentary lifestyle and metabolic syndrome (MS) were investigated.

Pre-Training Muscle Characteristics of Subjects Who Are Obese Determine How Well Exercise Training Will Improve Their Insulin Responsiveness.

Stuart, CA, Lee, ML, South, MA, Howell, MEA, Cartwright, BM, Ramsey, MW, and Stone, MH. Pre-training muscle characteristics of subjects who are obese determine how well exercise training will improve their insulin responsiveness. J Strength Cond Res 31(3): 798-808, 2017-Only half of prediabetic subjects who are obese who underwent exercise training without weight loss increased their insulin responsiveness.

Myosin content of individual human muscle fibers isolated by laser capture microdissection.

Muscle fiber composition correlates with insulin resistance, and exercise training can increase slow-twitch (type I) fibers and, thereby, mitigate diabetes risk. Human skeletal muscle is made up of three distinct fiber types, but muscle contains many more isoforms of myosin heavy and light chains, which are coded by 15 and 11 different genes, respectively. Laser capture microdissection techniques allow assessment of mRNA and protein content in individual fibers.

Insulin resistance and muscle insulin receptor substrate-1 serine hyperphosphorylation.

Insulin resistance in metabolic syndrome subjects is profound in spite of muscle insulin receptor and insulin-responsive glucose transporter (GLUT4) expression being nearly normal. Insulin receptor tyrosine kinase phosphorylation of insulin receptor substrate-1 (IRS-1) at Tyr896 is a necessary step in insulin stimulation of translocation of GLUT4 to the cell surface. Serine phosphorylation of IRS-1 by some kinases diminishes insulin action in mice.

Insulin responsiveness in metabolic syndrome after eight weeks of cycle training.

Introduction: Insulin resistance in obesity is decreased after successful diet and exercise. Aerobic exercise training alone was evaluated as an intervention in subjects with the metabolic syndrome.

Methods: Eighteen nondiabetic, sedentary subjects, 11 with the metabolic syndrome, participated in 8 wk of increasing intensity stationary cycle training.

Slow-twitch fiber proportion in skeletal muscle correlates with insulin responsiveness.

Context: The metabolic syndrome, characterized by central obesity with dyslipidemia, hypertension, and hyperglycemia, identifies people at high risk for type 2 diabetes.

Objective: Our objective was to determine how the insulin resistance of the metabolic syndrome is related to muscle fiber composition.

Design: Thirty-nine sedentary men and women (including 22 with the metabolic syndrome) had insulin responsiveness quantified using euglycemic clamps and underwent biopsies of the vastus lateralis muscle.

Impaired muscle AMPK activation in the metabolic syndrome may attenuate improved insulin action after exercise training.

Context: Strength training induces muscle remodeling and may improve insulin responsiveness.

Objective: This study will quantify the impact of resistance training on insulin sensitivity in subjects with the metabolic syndrome and correlate this with activation of intramuscular pathways mediating mitochondrial biogenesis and muscle fiber hypertrophy.

Design: Ten subjects with the metabolic syndrome (MS) and nine sedentary controls underwent 8 wk of supervised resistance exercise training with pre- and posttraining anthropometric and muscle biochemical assessments.

Brain glucose transporter (Glut3) haploinsufficiency does not impair mouse brain glucose uptake.

Mouse brain expresses three principal glucose transporters. Glut1 is an endothelial marker and is the principal glucose transporter of the blood-brain barrier. Glut3 and Glut6 are expressed in glial cells and neural cells.

Cycle training increased GLUT4 and activation of mammalian target of rapamycin in fast twitch muscle fibers.

Purpose: To determine whether cycle training of sedentary subjects would increase the expression of the principle muscle glucose transporters, six volunteers completed 6 wk of progressively increasing intensity stationary cycle cycling.

Methods: In vastus lateralis muscle biopsies, changes in expression of GLUT1, GLUT4, GLUT5, and GLUT12 were compared using quantitative immunoblots with specific protein standards. Regulatory pathway components were evaluated by immunoblots of muscle homogenates and immunohistochemistry of microscopic sections.

Insulin-stimulated translocation of glucose transporter (GLUT) 12 parallels that of GLUT4 in normal muscle.

Context: GLUT4 is the predominant glucose transporter isoform expressed in fat and muscle. In GLUT4 null mice, insulin-stimulated glucose uptake into muscle was diminished but not eliminated, suggesting that another insulin-sensitive system was present.

Objective: This study was intended to determine whether insulin caused GLUT12 translocation in muscle.

IGF-1 controls GLUT3 expression in muscle via the transcriptional factor Sp1.

Glucose transporter 3 (GLUT3), while first found in human fetal muscle, is predominantly expressed in brain and neural tissue. By several independent techniques we have previously shown that GLUT3 is expressed in human skeletal muscle cells. The structure of the human GLUT3 gene has not been previously reported nor has there been any evaluation of the 5'-untranslated region (UTR).

Overexpression of GLUT5 in diabetic muscle is reversed by pioglitazone.

Objective: This study was undertaken to quantify the expression of muscle GLUT in type 2 diabetes and to determine if treatment with an insulin-enhancing thiazolidenedione drug, pioglitazone, would alter its expression.

Research Design And Methods: Twelve patients with type 2 diabetes were randomly assigned to treatment with either pioglitazone or placebo in a double-blinded 8-week protocol. Protein and mRNA for GLUT4 and GLUT5 were quantified in muscle homogenates from biopsies of vastus lateralis before and after treatment.

Adipose tissue, hepatic, and skeletal muscle insulin sensitivity in extremely obese subjects with acanthosis nigricans.

We evaluated insulin action in skeletal muscle (glucose disposal), liver (glucose production), and adipose tissue (lipolysis) in 5 extremely obese women with acanthosis nigricans (AN), who had normal oral glucose tolerance, and 5 healthy lean subjects, by using a 5-stage pancreatic clamp and stable isotopically labeled tracer infusion. Basal plasma insulin concentration was much greater in obese subjects with AN than lean subjects (54.8 +/- 4.

Hexose transporter mRNAs for GLUT4, GLUT5, and GLUT12 predominate in human muscle.

In the past few years, 8 additional members of the facilitative hexose transporter family have been identified, giving a total of 14 members of the SLC2A family of membrane-bound hexose transporters. To determine which of the new hexose transporters were expressed in muscle, mRNA concentrations of 11 glucose transporters (GLUTs) were quantified and compared. RNA from muscle from 10 normal volunteers was subjected to RT-PCR.

Gene silencing using small interference RNA in mast cells.

Small interfering RNA (siRNA) is a potent and specific method of inducing gene silencing through induction of RNA interference. siRNAs can be allowed for in vitro and in vivo applications. siRNAs have been successfully studied in vitro, but little is known about its efficacy in vivo.

Angiopoietin-1 inhibits doxorubicin-induced human umbilical vein endothelial cell death by modulating fas expression and via the PI3K/Akt pathway.

Angiopoietin-1 (Ang-1) is essential for the maturation of blood vessels during vasculogenesis. Besides angiogenesis, recent publications indicate that Ang-1 is also a potent survival factor for endothelial cells; however, the mechanisms by which pathways remain elusive. Doxorubicin (DOX) is a powerful anticancer drug, but its use is severely restricted by its cardiotoxicity.

Stimulation of lipolysis by tumor necrosis factor-alpha in 3T3-L1 adipocytes is glucose dependent: implications for long-term regulation of lipolysis.

Tumor necrosis factor-alpha (TNF-alpha) and hyperglycemia both impair insulin sensitivity in vivo. This may be secondary to stimulation of adipose tissue lipolysis and consequent increased circulating free fatty acids (FFAs). Here we report that neither TNF-alpha nor glucose alone has a pronounced effect on lipolysis in 3T3-L1 adipocytes.