The Efficacy of Blood Flow Restriction Training to Improve Quadriceps Muscle Function after ACL Reconstruction.

Background: Blood flow restriction training (BFRT) is a popular rehabilitation intervention after anterior cruciate ligament reconstruction (ACLR). However, there are a lack of clinical trials establishing the efficacy of using BFRT during rehabilitation to improve quadriceps muscle function.

Purpose: To evaluate the efficacy of blood flow restriction training to improve quadriceps muscle strength, morphology, and physiology, and knee biomechanics in individuals after ACLR in a double-blind, randomized, placebo-controlled clinical trial (NCT03364647).

Sex Differences in Quadriceps Atrophy After Anterior Cruciate Ligament Tear.

Background: Female athletes lag behind their male counterparts in recovery from anterior cruciate ligament (ACL) injury. Quadriceps muscle size and strength are crucial factors for regaining function after ACL injury, but little is known about how these metrics vary due to biological sex.

Hypothesis: Female patients have reduced vastus lateralis fiber cross-sectional area (CSA) and lower quadriceps strength after ACL injury than male patients.

Overexpression of manganese superoxide dismutase mitigates ACL injury-induced muscle atrophy, weakness and oxidative damage.

Oxidative stress has been implicated in the etiology of skeletal muscle weakness following joint injury. We investigated longitudinal patient muscle samples following knee injury (anterior cruciate ligament tear). Following injury, transcriptomic analysis revealed downregulation of mitochondrial metabolism-related gene networks, which were supported by reduced mitochondrial respiratory flux rates.

GDF8 inhibition enhances musculoskeletal recovery and mitigates posttraumatic osteoarthritis following joint injury.

Musculoskeletal disorders contribute substantially to worldwide disability. Anterior cruciate ligament (ACL) tears result in unresolved muscle weakness and posttraumatic osteoarthritis (PTOA). Growth differentiation factor 8 (GDF8) has been implicated in the pathogenesis of musculoskeletal degeneration following ACL injury.

Vitamin D status associates with skeletal muscle loss after anterior cruciate ligament reconstruction.

BACKGROUNDAlthough 25-hydroxyvitamin D [25(OH)D] concentrations of 30 ng/mL or higher are known to reduce injury risk and boost strength, the influence on anterior cruciate ligament reconstruction (ACLR) outcomes remains unexamined. This study aimed to define the vitamin D signaling response to ACLR, assess the relationship between vitamin D status and muscle fiber cross-sectional area (CSA) and bone density outcomes, and discover vitamin D receptor (VDR) targets after ACLR.METHODSTwenty-one young, healthy, physically active participants with recent ACL tears were enrolled (17.

Depressed Protein Synthesis and Anabolic Signaling Potentiate ACL Tear-Resultant Quadriceps Atrophy.

Background: Anterior cruciate ligament (ACL) tear (ACLT) leads to protracted quadriceps muscle atrophy. Protein turnover largely dictates muscle size and is highly responsive to injury and loading. Regulation of quadriceps molecular protein synthetic machinery after ACLT has largely been unexplored, limiting development of targeted therapies.

Elevated dietary selenium rescues mitochondrial capacity impairment induced by decreased vitamin E intake in young exercising horses.

Maintenance of mitochondrial health, which is supported in part by dietary antioxidants such as selenium (Se) and vitamin E (vitE), is pertinent to optimizing athletic performance. Deficiencies in Se and vitE negatively impact muscle health but mitochondrial adaptations to various levels of dietary Se and vitE are poorly understood. Young Quarter Horses (mean ± SD: 17.

A glitch in the matrix: the pivotal role for extracellular matrix remodeling during muscle hypertrophy.

Multinuclear muscle fibers are the most voluminous cells in skeletal muscle and the primary drivers of growth in response to loading. Outside the muscle fiber, however, is a diversity of mononuclear cell types that reside in the extracellular matrix (ECM). These muscle-resident cells are exercise-responsive and produce the scaffolding for successful myofibrillar growth.

Skeletal Muscle Adaptations to Exercise Training in Young and Aged Horses.

In aged humans, low-intensity exercise increases mitochondrial density, function and oxidative capacity, decreases the prevalence of hybrid fibers, and increases lean muscle mass, but these adaptations have not been studied in aged horses. Effects of age and exercise training on muscle fiber type and size, satellite cell abundance, and mitochondrial volume density (citrate synthase activity; CS), function (cytochrome oxidase activity; CCO), and integrative (per mg tissue) and intrinsic (per unit CS) oxidative capacities were evaluated in skeletal muscle from aged ( = 9; 22 ± 5 yr) and yearling ( = 8; 9.7 ± 0.

Muscle-Specific Cellular and Molecular Adaptations to Late-Life Voluntary Concurrent Exercise.

Murine exercise models can provide information on factors that influence muscle adaptability with aging, but few translatable solutions exist. Progressive weighted wheel running (PoWeR) is a simple, voluntary, low-cost, high-volume endurance/resistance exercise approach for training young mice. In the current investigation, aged mice (22-mo-old) underwent a modified version of PoWeR for 8 wk.

Late-life exercise mitigates skeletal muscle epigenetic aging.

There are functional benefits to exercise in muscle, even when performed late in life, but the contributions of epigenetic factors to late-life exercise adaptation are poorly defined. Using reduced representation bisulfite sequencing (RRBS), ribosomal DNA (rDNA) and mitochondrial-specific examination of methylation, targeted high-resolution methylation analysis, and DNAge™ epigenetic aging clock analysis with a translatable model of voluntary murine endurance/resistance exercise training (progressive weighted wheel running, PoWeR), we provide evidence that exercise may mitigate epigenetic aging in skeletal muscle. Late-life PoWeR from 22-24 months of age modestly but significantly attenuates an age-associated shift toward promoter hypermethylation.

Vitamin D Promotes Skeletal Muscle Regeneration and Mitochondrial Health.

Vitamin D is an essential nutrient for the maintenance of skeletal muscle and bone health. The vitamin D receptor (VDR) is present in muscle, as is CYP27B1, the enzyme that hydroxylates 25(OH)D to its active form, 1,25(OH)D. Furthermore, mounting evidence suggests that vitamin D may play an important role during muscle damage and regeneration.

Complexed trace mineral supplementation alters antioxidant activities and expression in response to trailer stress in yearling horses in training.

To test the hypothesis that complexed trace mineral supplementation would increase antioxidant capacity and decrease muscle oxidative stress and damage in young horses entering an exercise training program, Quarter Horses (mean [Formula: see text] SD; 9.7 ± 0.7 mo) balanced by age, sex, and BW were assigned to receive complexed (CTM; n = 8) or inorganic (INORG; n = 8) trace minerals at -12 week relative to this study.

Dietary conjugated linoleic acid supplementation alters skeletal muscle mitochondria and antioxidant status in young horses.

Conjugated linoleic acid (CLA) improves oxidative stress and mitochondrial biogenesis in various species but has not been thoroughly investigated in horses. We collected blood and muscle samples from lightly exercising horses before and 6 and 12 wk after receiving either soybean oil (CON; n = 5) or CLA (CLA; n = 5) supplementation. Samples were analyzed for markers of mitochondrial characteristics, antioxidant status, oxidative stress, and muscle damage.

Temperament influences mitochondrial capacity in skeletal muscle from 8 through 18 mo of age in Brahman heifers.

Temperamental cattle tend to yield carcasses of poorer quality, and Brahman cattle are reportedly more temperamental than non-indicus cattle breeds. A potential link between temperament and product quality may be mitochondrial activity. We hypothesized that mitochondrial measures would be greater in temperamental compared with calm heifers and that the relationships between temperament and mitochondria would persist as heifers age.

RAPID COMMUNICATION: Differential skeletal muscle mitochondrial characteristics of weanling racing-bred horses1.

Responses of equine skeletal muscle characteristics to growth and training have been shown to differ between breeds. These differential responses may arise in part because muscle fiber type and mitochondrial density differ between breeds, even in untrained racing-bred horses. However, it is not known when these breed-specific differences manifest.

Rapid Communication: Differential skeletal muscle mitochondrial characteristics of weanling racing-bred horses.

Responses of equine skeletal muscle characteristics to growth and training have been shown to differ between breeds. These differential responses may arise in part because muscle fiber type and mitochondrial density differ between breeds, even in untrained racing-bred horses. However, it is not known when these breed-specific differences manifest.

Erratum: Evaluating equine feeding behavior utilizing GrowSafe Systems: a pilot study.

[This corrects the article DOI: 10.1093/tas/txz002.].

Evaluating equine feeding behavior utilizing GrowSafe Systems: a pilot study.

Equine research and management is limited to single-housing systems if individual animal intake is to be precisely recorded. Even then, dry forage intake is difficult to quantify accurately due to stomping or mixing hay with fecal matter and bedding. In cattle management, GrowSafe Systems (GrowSafe) is a commonly used tool to closely monitor individual animal feeding data using radio frequency identification (RFID) tag technology.

Effects of dietary amino acid supplementation on measures of whole-body and muscle protein metabolism in aged horses.

The objective of this study was to examine markers of whole-body and muscle protein metabolism in aged horses fed a diet typical for North American aged horses, supplemented with amino acids. In a replicated Latin square design, six aged horses (20 ± 1.1 years) were studied while receiving each of three isocaloric, isonitrogenous diets, a control treatment concentrate (CON; 100 mg/kg BW day lysine, 84 mg kg  day threonine, 51 mg kg  day methionine), LYS/THR (134 mg kg BW day lysine, 110 mg kg BW day threonine, 52 mg kg BW day methionine) and LYS/THR/MET (132 mg kg BW day lysine, 112 mg kg BW day threonine, 62 mg kg BW day methionine).