Physiological assessment of a 16 day, 4385 km ultra-endurance mountain bike race: A case study.

The Tour Divide (TD) is a 4385 km ultra-endurance bicycle race that follows the continental divide from Canada to Mexico. In this case study, we performed a comprehensive molecular and physiological profile before and after the completion of the TD. Assessments were performed 35 days before the start (Pre-TD) and ∼36 h after the finish (Post-TD).

Contralateral versus ipsilateral protective effect against muscle damage of the elbow flexors and knee extensors induced by maximal eccentric exercise.

The present study compared the ipsilateral repeated bout effect (IL-RBE) and contralateral repeated bout effect (CL-RBE) of the elbow flexors (EF) and knee flexors (KF) for the same interval between bouts to shed light on their mechanisms. Fifty-two healthy sedentary young (20-28 years) men were randomly assigned to the IL-EF, IL-KF, CL-EF, and CL-KF groups (n = 13/group). Thirty maximal eccentric contractions of the EF were performed in IL-EF and CL-EF, and 60 maximal eccentric contractions of the KF were performed in IL-KF and CL-KF, with a 2-week interval between bouts.

An altered response in macrophage phenotype following damage in aged human skeletal muscle: implications for skeletal muscle repair.

The purpose of this study was to test the hypothesis that macrophage polarization is altered in old compared to young skeletal muscle, possibly contributing to the poor satellite cell response observed in older muscle tissue. Muscle biopsies were collected prior to and at 3, 24, and 72 h following a muscle-damaging exercise in young and old individuals. Immunohistochemistry was used to measure i.

Whole-Body Vibration as a Warm-up Before Exercise-Induced Muscle Damage on Symptoms of Delayed-Onset Muscle Soreness in Trained Subjects.

Magoffin, RD, Parcell, AC, Hyldahl, RD, Fellingham, GW, Hopkins, JT, and Feland, JB. Whole-body vibration as a warm-up before exercise-induced muscle damage on symptoms of delayed-onset muscle soreness in trained subjects. J Strength Cond Res 34(4): 1123-1132, 2020-There is no clear scientific evidence that whole-body vibration (WBV) used as a warm-up before performing eccentric exercise mitigates delayed-onset muscle soreness (DOMS) and speeds strength loss recovery.

Preclinical characterization of the JAK/STAT inhibitor SGI-1252 on skeletal muscle function, morphology, and satellite cell content.

Background: Recent studies have highlighted the JAK/STAT signaling pathway in the regulation of muscle satellite cell behavior. Herein we report preclinical studies designed to characterize the effects of a novel JAK/STAT inhibitor on plantar flexor skeletal muscle function, morphology, and satellite cell content.

Methods: The compound, SGI-1252, was administered orally (400mg/kg) in a 10% dextrose solution to wild type mice (n = 6) 3 times per week for 8 weeks.

Ambulation speed and corresponding mechanics are associated with changes in serum cartilage oligomeric matrix protein.

Because serum cartilage oligomeric matrix protein (COMP) has been used to reflect articular cartilage condition, we aimed to identify walking and running mechanics that are associated with changes in serum COMP. Eighteen subjects (9 male, 9 female; age=23 ± 2 yrs.; mass=68.

Skeletal Muscle Inflammation Following Repeated Bouts of Lengthening Contractions in Humans.

Skeletal muscle responds to exercise-induced damage by orchestrating an adaptive process that protects the muscle from damage by subsequent bouts of exercise, a phenomenon called the repeated bout effect (RBE). The mechanisms underlying the RBE are not understood. We hypothesized that an attenuated inflammation response following a repeated bout of lengthening contractions (LC) would be coincidental with a RBE, suggesting a potential relationship.

Extracellular matrix remodeling and its contribution to protective adaptation following lengthening contractions in human muscle.

This study determined the contribution of extracellular matrix (ECM) remodeling to the protective adaptation of human skeletal muscle known as the repeated-bout effect (RBE). Muscle biopsies were obtained 3 hours, 2 days, and 27 days following an initial bout (B1) of lengthening contractions (LCs) and 2 days following a repeated bout (B2) in 2 separate studies. Biopsies from the nonexercised legs served as controls.

Satellite cell activity is differentially affected by contraction mode in human muscle following a work-matched bout of exercise.

Optimal repair and adaptation of skeletal muscle is facilitated by resident stem cells (satellite cells). To understand how different exercise modes influence satellite cell dynamics, we measured satellite cell activity in conjunction with markers of muscle damage and inflammation in human skeletal muscle following a single work- and intensity-matched bout of eccentric (ECC) or concentric contractions (CON). Participants completed a single bout of ECC (n = 7) or CON (n = 7) of the knee extensors.

Production of consistent pain by intermittent infusion of sterile 5% hypertonic saline, followed by decrease of pain with cryotherapy.

Context: It is suggested that postinjury pain is difficult to examine; thus, investigators have developed experimental pain models. To minimize pain, cryotherapy (cryo) is applied, but reports on its effectiveness are limited.

Objective: To investigate a pain model for the anterior knee and examine cryo in reducing the pain.

Skeletal muscle dysfunction in muscle-specific LKB1 knockout mice.

Liver kinase B1 (LKB1) is a tumor-suppressing protein that is involved in the regulation of muscle metabolism and growth by phosphorylating and activating AMP-activated protein kinase (AMPK) family members. Here we report the development of a myopathic phenotype in skeletal and cardiac muscle-specific LKB1 knockout (mLKB1-KO) mice. The myopathic phenotype becomes overtly apparent at 30-50 wk of age and is characterized by decreased body weight and a proportional reduction in fast-twitch skeletal muscle weight.

Myogenic regulatory factor response to resistance exercise volume in skeletal muscle.

This study examined the impact of resistance exercise volume on myoD and myogenin in rodent quadriceps muscle. Six-month-old male Sprague-Dawley rats (316 +/- 2 g) performed either low-volume (LV; 10 sets x 10 contractions) or high-volume (HV; 20 sets x 10 contractions) resistance exercise at 75% one-repetition maximum. Muscles were analyzed for myogenin and myoD mRNA and protein expression 6, 12, 24 and 48 h post-exercise.

Ground reaction force differences between running shoes, racing flats, and distance spikes in runners.

Various shoes are worn by distance runners throughout a training season. This study measured the differences in ground reaction forces between running shoes, racing flats, and distance spikes in order to provide information about the potential effects of footwear on injury risk in highly competitive runners. Ten male and ten female intercollegiate distance runners ran across a force plate at 6.

Adaptations to high-intensity intermittent exercise in rodents.

In humans, exercise-induced plasma volume (PV) expansion is typically associated with an increase in plasma albumin content, due in part to an increase in hepatic albumin synthesis. We tested the ability of a 12-day high-intensity intermittent exercise protocol to induce an increase in PV in rodents. Since albumin synthesis is transcriptionally regulated, we tested the hypothesis that exercise training would induce an increase in hepatic albumin gene expression.

Structural protein alterations to resistance and endurance cycling exercise training.

The muscle cytoskeleton is necessary for the effective transmission of forces generated by actin-myosin interactions. We have examined the impact of muscle force and exercise volume on the cytoskeleton by measuring desmin and dystrophin content in human skeletal muscle after 12 weeks of progressive resistance or endurance cycle training. Muscle biopsies of the vastus lateralis were obtained before and after training.

Ballistic stretching increases flexibility and acute vertical jump height when combined with basketball activity.

Stretching is often included as part of a warm-up procedure for basketball activity. However, the efficacy of stretching with respect to sport performance has come into question. We determined the effects of 4 different warm-up protocols followed by 20 minutes of basketball activity on flexibility and vertical jump height.

Temporal response of desmin and dystrophin proteins to progressive resistance exercise in human skeletal muscle.

We have investigated the adaptations of the cytoskeletal proteins desmin and dystrophin in relationship to known muscular adaptations of resistance exercise. We measured desmin, dystrophin, and actin protein contents, myosin heavy chain (MHC) isoform distribution, muscle strength, and muscle cross-sectional area (CSA) during 8 wk of progressive resistance training or after a single bout of unaccustomed resistance exercise. Muscle biopsies were taken from the vastus lateralis of 12 untrained men.

Single-fiber MHC polymorphic expression is unaffected by sprint cycle training.

Purpose: The present investigation examined single-fiber MHC alterations in response to high-intensity, short-duration, sprint cycle training.

Methods: Ten untrained college-age male subjects participated in 8 wk of a progressive sprint cycle training program. Training involved 15-s maximal sprints separated by 5 min of rest beginning with four sprints x 2 d in week 1 and increasing to six sprints x 3 d at week 8.

Aerobic and resistance exercise sequence affects excess postexercise oxygen consumption.

Excess postexercise oxygen consumption (EPOC) may describe the impact of previous exercise on energy metabolism. Ten males completed Resistance Only, Run Only, Resistance-Run, and Run-Resistance experimental conditions. Resistance exercise consisted of 7 lifts.

Glycemic and insulinemic responses to protein supplements.

Objective: The effects of common servings of commercially marketed nutritional protein supplements on blood glucose and insulin responses were studied in 12 healthy men after ingestion of feedings that had varying carbohydrate and protein compositions.

Design: Fasting subjects consumed a 50-gram glucose drink, a white bagel, peanuts, a protein bar, or a protein drink in a counterbalanced fashion.

Setting: Subjects rested in a supine position and were not disturbed while blood samples were drawn at rest and at 10-minute intervals during the ensuing 2 hours.

Desmin increases with high-intensity concentric contractions in humans.

To investigate the role desmin may play in muscular adaptation to exercise, we measured desmin protein content in the vastus lateralis muscle of seven untrained men in response to 8 weeks of high-intensity cycle training. Training involved 15-s sprints separated by rest for 5 min. Subjects began with four sprints twice per week, and progressed to six sprints three times per week.

Cordyceps Sinensis (CordyMax Cs-4) supplementation does not improve endurance exercise performance.

It is purported that supplementation with Cordyceps Sinensis (CordyMax Cs-4) will improve oxidative capacity and endurance performance. The intent of this investigation was to examine the effects of CordyMax Cs-4 supplementation on VO<(2peak,) ventilatory threshold, and endurance performance in endurance-trained cyclists. Twenty-two male cyclists participated in 5 weeks of supplementation with CordyMax Cs-4 tablets (3 g/d).

Inadequate carbohydrate intake following prolonged exercise does not increase muscle soreness after 15 minutes of downhill running.

In Delayed Onset Muscle Soreness (DOMS), muscles become sore 24 to 48 hours after eccentric and unaccustomed activity. Fiber stiffness, due to decreased muscle glycogen, may predispose muscle to greater damage during eccentric exercise. This study sought to determine if inadequate carbohydrate intake following a protocol to decrease muscle glycogen would increase DOMS after 15 min of downhill running.

Single muscle fiber myosin heavy chain distribution in elite female track athletes.

Purpose: Myosin heavy chain (MHC) characterization of tissue samples from the gastrocnemius muscle of six elite female athletes and 10 untrained females was performed using myosin ATPase histochemistry and gel electrophoresis. Athletes were of national and international caliber, whereas their untrained counterparts were healthy individuals not involved in a regular exercise program.

Methods: Muscle biopsies for the athletes were performed 14 wk into their training season and analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and myosin ATPase techniques.

Effects of warm-up before eccentric exercise on indirect markers of muscle damage.

Purpose: To test whether active and passive warm-up conducted before eccentric exercise attenuates clinical markers of muscle damage.

Methods: Untrained subjects were exposed to one of five conditions: low-heat passive warm-up (N = 10), high-heat passive warm-up (N = 4), or active warm-up (N = 9), preceding eccentric exercise; eccentric exercise without warm-up (N = 10); or high-heat passive warm-up without eccentric exercise (N = 10). Passive warm-up of the elbow flexors was achieved using pulsed short-wave diathermy, and active warm-up was achieved by concentric contraction.