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Related Concept Videos

Classification of Skeletal Muscle Fibers01:48

Classification of Skeletal Muscle Fibers

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Skeletal muscles continuously produce ATP to provide the energy that enables muscle contractions. Skeletal muscle fibers can be categorized into three types based on differences in their contraction speed and how they produce ATP, as well as physical differences related to these factors. Most human muscles contain all three muscle fiber types, albeit in varying proportions.
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Slow oxidative, muscle fibers appear red due to large numbers of capillaries and high levels of...
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Exercise and Muscle Performance01:27

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Exercise induces a range of adaptations in muscle tissue, depending on the type and duration of activity. Such physical training can be broadly categorized into two types: endurance exercises and resistance exercises.
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Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...
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Skeletal muscles are composed of a bundle of muscle fibers and are attached to bones through tendons. Each skeletal muscle fiber is a single muscle cell. The sarcolemma, the plasma membrane of a skeletal muscle cell, consists of a lipid bilayer and glycocalyx that supports muscle fibers. The sarcolemma extends into the muscle cells to form tubular structures called transverse or T-tubules. Each side of the T-tubules consists of a membrane-bound structure called the sarcoplasmic reticulum,...
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The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open....
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Disorders of the Skeletal Muscle

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The clinical conditions affecting the skeletal muscle tissue are broadly categorized as musculoskeletal and neuromuscular disorders.
Musculoskeletal disorders
Musculoskeletal disorders involve injuries and conditions affecting the skeletal muscles and associated connective tissues. These disorders can arise from acute biomechanical stresses or chronic overuse and can occur across different age groups. Common injuries include sprains, fractures, and muscular strains, often resulting from...
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Naming Skeletal Muscles01:19

Naming Skeletal Muscles

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The naming of the approximately 700 muscles in the human body is based on a set of criteria designed to provide descriptive information about each muscle, making it easier to identify and remember them.
The key factors used in naming muscles include:
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Human Skeletal Muscle Biopsy Procedures Using the Modified Bergström Technique
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Skeletal Muscle Glycogen Content at Rest and During Endurance Exercise in Humans: A Meta-Analysis.

José L Areta1, Will G Hopkins2

  • 1Department of Physical Performance, Norwegian School of Sport Sciences, Sognsveien 220, 0863, Oslo, Norway. joselareta@gmail.com.

Sports Medicine (Auckland, N.Z.)
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Muscle glycogen concentration, vital for exercise, is influenced by carbohydrate availability and fitness. These factors also impact glycogen use during exercise, providing insights for endurance training prescriptions.

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Area of Science:

  • Exercise Physiology
  • Nutritional Biochemistry
  • Sports Science

Background:

  • Skeletal muscle glycogen is crucial for muscle contraction and metabolic responses to exercise.
  • Manipulating muscle glycogen can enhance athletic performance and training adaptations.
  • Assessing muscle glycogen in real-world settings is challenging due to a lack of normative data.

Purpose of the Study:

  • To meta-analyze the impact of fitness, dietary carbohydrate (CHO) availability, and other factors on muscle glycogen concentration.
  • To establish normative values for muscle glycogen at rest and during exercise of varying durations and intensities.

Main Methods:

  • A systematic literature search was conducted on PubMed for human studies on muscle glycogen and exercise.
  • 181 studies involving cycling and running were included, with muscle glycogen assessed via biopsy analysis.
  • Meta-regression models analyzed the effects of fitness (VO2max), CHO availability, exercise intensity, and duration on muscle glycogen.

Main Results:

  • High CHO availability significantly increased resting muscle glycogen, while low availability substantially decreased it.
  • Higher exercise intensity and greater baseline muscle glycogen led to increased glycogen utilization, particularly during longer durations.
  • Fitness (VO2max) and CHO availability showed moderate effects on resting glycogen, with smaller effects observed in females and specific muscle groups.

Conclusions:

  • Dietary CHO availability and individual fitness levels are key determinants of resting muscle glycogen.
  • Exercise intensity and initial muscle glycogen levels significantly influence glycogen depletion during exercise.
  • The findings provide valuable normative data for optimizing endurance exercise prescriptions.