Sex-related differences in motor unit behavior are influenced by myosin heavy chain during high- but not moderate-intensity contractions.

Aims: Motor unit recruitment and firing rate patterns of the vastus lateralis (VL) have not been compared between sexes during moderate- and high-intensity contraction intensities. Additionally, the influence of fiber composition on potential sex-related differences remains unquantified.

Methods: Eleven males and 11 females performed 40% and 70% maximal voluntary contractions (MVCs).

Myofiber hypertrophy adaptations following 6 weeks of low-load resistance training with blood flow restriction in untrained males and females.

The effects of low-load resistance training with blood flow restriction (BFR) on hypertrophy of type I/II myofibers remains unclear, especially in females. The purpose of the present study is to examine changes in type I/II myofiber cross-sectional area (fCSA) and muscle CSA (mCSA) of the vastus lateralis (VL) from before (Pre) to after (Post) 6 wk of high-load resistance training (HL; = 15, 8 females) and low-load resistance training with BFR ( = 16, 8 females). Mixed-effects models were used to analyze fCSA with group (HL, BFR), sex (M, F), fiber type (I, II), and time (Pre, Post) included as factors.

A noninvasive test for estimating myosin heavy chain of the vastus lateralis in females with mechanomyography.

This study examined relationships between percent myosin heavy chain (%MHC) expression and mechanomyographic amplitude (MMG). Fifteen females (age ± SD=21.3 ± 5.

Notch, Numb and Numb-like responses to exercise-induced muscle damage in human skeletal muscle.

New Findings: What is the central question of this study? Do Notch, Numb and Numb-like expression change in human skeletal muscle after exercise-induced muscle damage? What are the main finding and its importance? Notch gene expression trends toward an increase in response to an acute bout of exercise-induced muscle damage, while Numb and Numb-like expression does not change. These results suggest that human skeletal muscle response to exercise-induced muscle damage is dynamic and may differ from Drosophila and rodent models. Furthermore, the timing of muscle biopsies, training status and muscle damage protocols should be considered.

Effects of continuous cycling training on motor unit firing rates, input excitation, and myosin heavy chain of the vastus lateralis in sedentary females.

This study examined the effects of continuous endurance training on motor unit (MU) mean firing rates (MFR), percent myosin heavy chain (%MHC) isoforms, and muscle cross-sectional area (mCSA) of the vastus lateralis (VL). Twelve females completed 5-weeks of continuous cycling-training (CYC), while 8 females were controls (CON). Participants performed maximal voluntary contractions (MVCs) and 40% MVCs of the knee extensors before (PRE) and after the 5-week treatment period at the same absolute pre-treatment submaximal torque (POST) and relative to post-treatment MVCs (POST).

Change in measures of moral function following acute bouts of Marine Corps Martial Arts Training.

The Marine Corps Martial Arts Program (MCMAP) was developed to prepare Marines for complex battlefield situations that include hand-to-hand combat and ethical decision making. The objective of this study was to quantify changes in ethical decision-making following MCMAP training. Fifty-five, active duty, newly enlisted U.

Effects of Transspinal Direct Current Stimulation on Cycling Perception of Effort and Time to Exhaustion.

Ciccone, AB, Fry, AC, Emerson, DM, Gallagher, PM, Herda, TJ, and Weir, JP. Effects of transspinal direct current stimulation on cycling perception of effort and time to exhaustion. J Strength Cond Res 35(2): 347-352, 2021-In the past decade, researchers have investigated the efficacy of transspinal direct current stimulation (tsDCS) on the central nervous system and afferent neuron function in humans.

Skeletal Muscle Composition and Glucose Levels in Children Who Are Overweight and Obese.

Background: Skeletal muscle is overlooked in the realm of insulin resistance in children who are overweight and obese despite the fact that it accounts for the most glucose disposal.

Objectives: Therefore, this study examined fasted glucose levels and muscle cross-sectional area and echo intensity (EI) via ultrasound images of the first dorsal interosseous, vastus lateralis, and rectus femoris in children who are normal weight and overweight and obese aged 8-10 years.

Methods: In total, 13 males (age = 9.

Muscular strength and power are correlated with motor unit action potential amplitudes, but not myosin heavy chain isoforms in sedentary males and females.

It remains unclear if the sizes of higher-threshold motor units (MU) are associated with muscular strength and power. Therefore, the purpose of this study was to examine sex-related differences in muscle cross-sectional area (mCSA), percent myosin heavy chain (%MHC) isoform expression, and the MU action potential amplitudes (MUAP)-recruitment threshold (RT) relationships of the vastus lateralis and isometric peak torque, isokinetic peak torque and mean power at 1.05 rad·s of the leg extensors.

Transcranial Direct Current Stimulation of the Temporal Lobe Does Not Affect High-Intensity Work Capacity.

Ciccone, AB, Deckert, JA, Schlabs, CR, Tilden, MJ, Herda, TJ, Gallagher, PM, and Weir, JP. Transcranial direct current stimulation of the temporal lobe does not affect high-intensity work capacity. J Strength Cond Res 33(8): 2074-2086, 2019-Stimulation of the left insular cortex may affect heart rate variability (HRV) and exercise effort perception.

Effect of Three Different Maximal Concentric Velocity Squat Protocols on MAPK Phosphorylation and Endocrine Responses.

Kudrna, RA, Fry, AC, Nicoll, JX, Gallagher, PM, and Prewitt, MR. Effect of three different maximal concentric velocity squat protocols on MAPK phosphorylation and endocrine responses. J Strength Cond Res 33(6): 1693-1703, 2019-The purpose of this study was to determine the effect of 3 different back squat protocols on intracellular signaling, endocrine responses, and power fatigue.

T cell activation and proliferation following acute exercise in human subjects is altered by storage conditions and mitogen selection.

Recent work investigating exercise induced changes in immunocompetence suggests that some of the ambiguity in the literature is resultant from different cell isolation protocols and mitogen selection. To understand this effect, we compared post-exercise measures of T cell activation and proliferation using two different stimulation methods (costimulation through CD28 or stimulation with phytohaemagglutinin [PHA]). Further, we investigated whether exercise induced changes are maintained when T cell isolation from whole blood is delayed overnight in either a room temperature or chilled (4°C) environment.

The influence of myosin heavy chain isoform content on mechanical behavior of the vastus lateralis in vivo.

This study examined correlations between type I percent myosin heavy chain isoform content (%MHC) and mechanomyographic amplitude (MMGRMS) during isometric muscle actions. Fifteen (age=21.63±2.

Influence of the contractile properties of muscle on motor unit firing rates during a moderate-intensity contraction in vivo.

It is suggested that firing rate characteristics of motor units (MUs) are influenced by the physical properties of the muscle. However, no study has correlated MU firing rates at recruitment, targeted force, or derecruitment with the contractile properties of the muscle in vivo. Twelve participants (age = 20.

Acute bouts of exercise induce a suppressive effect on lymphocyte proliferation in human subjects: A meta-analysis.

Objective: Lymphocyte proliferative responses are commonly used to assess immune function in clinical settings, yet it is unclear how proliferative capacity is altered by exercise. This analysis aims to quantitatively assess the proliferative response of lymphocytes following an acute bout of exercise.

Methods: Electronic databases were searched for articles containing the keywords "exercise" OR "acute" OR "aerobic" OR "resistance training" OR "immune function" AND "proliferation" AND "lymphocyte.

Advanced Treatment Monitoring for Olympic-Level Athletes Using Unsupervised Modeling Techniques.

Context: Analysis of injury and illness data collected at large international competitions provides the US Olympic Committee and the national governing bodies for each sport with information to best prepare for future competitions. Research in which authors have evaluated medical contacts to provide the expected level of medical care and sports medicine services at international competitions is limited.

Objective: To analyze the medical-contact data for athletes, staff, and coaches who participated in the 2011 Pan American Games in Guadalajara, Mexico, using unsupervised modeling techniques to identify underlying treatment patterns.

Immunoendocrine alterations following Marine Corps Martial Arts training are associated with changes in moral cognitive processes.

Combined physical and psychological stress events have been associated with exacerbated endocrine responses and increased alterations in immune cell trafficking when compared to exercise stress alone. Military training programs are rigorous in nature and often purposefully delivered in environments combining high levels of both physical and mental stress. The objective of this study was to assess physiological and cognitive changes following U.

Computerized neurocognitive assessments and detection of the malingering athlete.

Background: Healthcare professionals are concerned that athletes have the capability to intentionally underperform on baseline computerized neurocognitive assessments in an effort to expedite their return to the field of play following a concussion. The purpose of this study was to determine if the use of overlapping validity measures will provide better sensitivity for detecting malingering athletes on a baseline computerized neurocognitive assessment.

Methods: Twenty male, collegiate rugby players (mean age 23±4 years) participated in this study.

Focal adhesion kinase and its role in skeletal muscle.

Skeletal muscle has a remarkable ability to respond to different physical stresses. Loading muscle through exercise, either anaerobic or aerobic, can lead to increases in muscle size and function while, conversely, the absence of muscle loading stimulates rapid decreases in size and function. A principal mediator of this load-induced change is focal adhesion kinase (FAK), a downstream non-receptor tyrosine kinase that translates the cytoskeletal stress and strain signals transmitted across the cytoplasmic membrane by integrins to activate multiple anti-apoptotic and cell growth pathways.

Changes in α7β1 integrin signaling after eccentric exercise in heat-shocked rat soleus.

Introduction: α7β1 integrin links the extracellular matrix to the focal adhesion (FA) in skeletal muscle and serves as a stabilizing and signal relayer. Heat shock (HS) induces expression of proteins that interact with the FA.

Methods: Male Wistar rats were assigned to 1 of 3 groups: control (CON); eccentric exercise (EE); or EE+HS (HS).

Methods comparison: assessing agreement of physiological parameters obtained from exercise on two different cycle ergometers.

The purpose of this study was to determine the agreement of physiological parameters measured during exercise testing on 2 devices at established power outputs (POs). Ten trained male cyclists were recruited. The devices used for comparison were the Lode stationary bicycle ergometer (SBE) (Lode Excalibur) and the PowerTap Pro+ (BPT) (Saris Cycling Group) mobile ergometer.