Physiology and Anatomy

Specificity Principle (Specificity of Exercise Training or SAID)

Specificity has to do with the specific responses that occur as a result of training. In order for long-term physiological changes or adaptations to occur, a repeated, or chronic, stimuli must be applied to the body, along with progressive overload. This means for new levels of fitness to be achieved, an exercise (the stimulus) must be repeated often over a period of time. The specificity principle states that these metabolic or physiologic changes are specific to the muscular, cardiorespiratory, and neurologic responses that are required by the exercise activity. The patterns of muscle firing, and the cardiorespiratory responses are the two variables that have the most specific change.Bibliography item ehrman not found.,Bibliography item mcardle not found. The specificity principle is also known as SAID or Specific Adaptations to Imposed Demands.

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Soda Loading (Bicarbonate Loading, Buffer Boosting) for High Intensity Anaerobic Endurance

During high intensity anaerobic events, the muscles fatigue and energy supply is compromised because of the buildup of lactic acid from glycolysis. Athletes in high intensity events that last 2 to 10 minutes, such as a 400 to 800 or 1500 meter running races or middle distance swimming races sometimes use soda loading in an attempt to neutralize the lactic acid that accumulates in the blood. Depending on interpretation of the research, some experts suggest that the benefit is limited to events of 1 to 7 minute duration. Soda loading is also called buffer boosting or bicarbonate loading. It is also called, more rarely, soda doping or simply acid buffering.

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All-Or-None Response (Of Muscle Fibers)

All-or-none Response: Phenomenon in which a muscle fiber contracts completely when exposed to a threshold stimulus, or not at all. When a skeletal muscle is stimulated to contract by a motor neuron a minimum amount of stimulus is needed to start the process of muscle contraction. This minimum amount of stimulus is called the threshold stimulus and results in an action potential. Once this threshold signal is released, a muscle cell contracts completely. A muscle cell never contracts partially. Once the stimulus reaches the depolarization threshold, the muscle membrane depolarizes and the cell (fiber) contracts. The all or none response is the same for nerves cells, where if a threshold stimulus for depolarization is reached, the membrane depolarizes. Any increase in the intensity of the stimulus does not result in a greater response. Either a muscle or nerve cell depolarizes completely or not at all..so "all" or "none at all". In this way, a muscle fiber always contracts maximally, even if the contraction is initiated by a large electrical shock rather than a motor neuron signal..the contraction is the same intensity, either maximal or nonexistent.

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Active Insufficiency

Active insufficiency occurs when a multi-joint muscle reaches a length (shortened) where it can no longer apply an effective force. To demonstrate active insufficiency one can fully flex (bend) the knee on one leg while simultaneously trying to bring that leg back to achieve full hip extension. Hip extension will be limited because the hamstrings are unable to shorten enough to produce a complete range of motion. Some will also notice a cramping in the hamstring muscles during this maneuver. By the same token, if you try bringing back your hip into a hyper-extended position (bringing your leg behind you), and then bending your knee, you will find that your knee flexion is limited. The hamstrings can only perform one of these functions well at one time. When both are attempted at the same time, the muscle essentially goes "slack" and is unable to contract effectively because it is already well shortened. Straightening the leg (extending the knee) should restore full range of hip extension motion and the difference will be significant. Active insufficiency reflects the inability of a multijoint muscle to apply an adequate force in all degrees of motion.

Another example is the finger flexors. You may have noticed that you cannot produce a tight flex with your wrist bent (in flexion). This is because of active insufficiency of the finger flexors. They can only make a tight flex with the wrist in a neutral position. See passive insufficiency.

The gastrocnemius of the calf plantar flexes the ankle but also crosses over the knee joint. Therefore, if the knee bent, shortening the muscle at that joint, it can no longer apply as effective a force in plantarflexion. This fact is taken advantage of during calf raises, when, if done seated with the knees bent, shifts the focus from the gastronemius, which is actively insufficient, to the soleus, making it the prime mover in seated calf raises. When the calf raises are done standing, the gastrocnemius can apply a full force.

Need more information like this? See Applied Biomechanics: Concepts and Connections

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Action Potential

An action potential is an electrical signal that passes along the membrane of a neuron or muscle fiber. When an applied electrical stimulus is beyond a certain level called the threshold of excitation, a massive depolarization of the membrane occurs.

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Accommodation

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Acclimatization

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How Metabolic Energy Systems Meet ATP Demand During Intense Exercise

High-intensity exercise can result in up to a 1,000-fold increase in the rate of ATP demand compared to that at rest (Newsholme et al., 1983). To sustain muscle contraction, ATP needs to be regenerated at a rate complementary to ATP demand. Three energy systems function to replenish ATP in muscle: (1) Phosphagen, (2) Glycolytic, and (3) Mitochondrial Respiration. The three systems differ in the substrates used, products, maximal rate of ATP regeneration, capacity of ATP regeneration, and their associated contributions to fatigue. In this exercise context, fatigue is best defined as a decreasing force production during muscle contraction despite constant or increasing effort. The replenishment of ATP during intense exercise is the result of a coordinated metabolic response in which all energy systems contribute to different degrees based on an interaction between the intensity and duration of the exercise, and consequently the proportional contribution of the different skeletal muscle motor units. Such relative contributions also determine to a large extent the involvement of specific metabolic and central nervous system events that contribute to fatigue. The purpose of this paper is to provide a contemporary explanation of the muscle metabolic response to different exercise intensities and durations, with emphasis given to recent improvements in understanding and research methodology.

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Force Transmission between Synergistic Skeletal Muscles through Connective Tissue Linkages

The classic view of skeletal muscle is that force is generated within its muscle fibers and then directly transmitted in-series, usually via tendon, onto the skeleton. In contrast, recent results suggest that muscles are mechanically connected to surrounding structures and cannot be considered as independent actuators. This article will review experiments on mechanical interactions between muscles mediated by such epimuscular myofascial force transmission in physiological and pathological muscle conditions. In a reduced preparation, involving supraphysiological muscle conditions, it is shown that connective tissues surrounding muscles are capable of transmitting substantial force. In more physiologically relevant conditions of intact muscles, however, it appears that the role of this myofascial pathway is small. In addition, it is hypothesized that connective tissues can serve as a safety net for traumatic events in muscle or tendon. Future studies are needed to investigate the importance of intermuscular force transmission during movement in health and disease.

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Strength Performance Psychology Versus Physiology: It's All Mental

I've complained and I've complained about silly quantitative notions concerning the factors that determine success. It's 20% percent training, 80% nutrition and stuff like that. Complete and utter nonsense. Says nothing. Contributes nothing.

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Oxidative Stress From Exercise

The topic of exercise-induced oxidative stress has received considerable attention in recent years, with close to 300 original investigations published since the early work of Dillard and colleagues in 1978. Single bouts of aerobic and anaerobic exercise can induce an acute state of oxidative stress. This is indicated by an increased presence of oxidized molecules in a variety of tissues. Exercise mode, intensity, and duration, as well as the subject population tested, all can impact the extent of oxidation. Moreover, the use of antioxidant supplements can impact the findings. Although a single bout of exercise often leads to an acute oxidative stress, in accordance with the principle of hormesis, such an increase appears necessary to allow for an up-regulation in endogenous antioxidant defenses. This review presents a comprehensive summary of original investigations focused on exercise-induced oxidative stress. This should provide the reader with a well-documented account of the research done within this area of science over the past 30 years.

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Understanding Normal, Injured and Healing Ligaments And Tendons

Ligaments and tendons are soft connective tissues which serve essential roles for biomechanical function of the musculoskeletal system by stabilizing and guiding the motion of diarthrodial joints. Nevertheless, these tissues are frequently injured due to repetition and overuse as well as quick cutting motions that involve acceleration and deceleration. These injuries often upset this balance between mobility and stability of the joint which causes damage to other soft tissues manifested as pain and other morbidity, such as osteoarthritis.

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Muscle Fiber Type: Contractile and Metabolic Properties

Skeletal muscle demonstrates a remarkable plasticity, adapting to a variety of external stimuli (Booth and Thomason 1991; Chibalin et al. 2000; Hawley 2002; Flück and Hoppeler 2003), including habitual level of contractile activity (e.g., endurance exercise training), loading state (e.g., resistance exercise training), substrate availability (e.g., macronutrient supply), and the prevailing environmental conditions (e.g., thermal stress). This phenomenon of plasticity is common to all vertebrates (Schiaffino and Reggiani 1996). However, there exists a large variation in the magnitude of adaptability among species, and between individuals within a species. Such variability partly explains the marked differences in aspects of physical performance, such as endurance or strength, between individuals, as well as the relationship of skeletal muscle fiber type composition to certain chronic disease states, including obesity and insulin resistance.

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Exercise Protects You From Colds

Well, at least it does according to this article by ACSM which claims that, according to David C. Nieman, DrPH, FACSM, "multiple studies have shown a 25- to 50-percent decrease in sick time for active people completing at least 45 minutes of moderate-intensity exercise (such as walking) most days of the week."

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Overuse Injuries in Female Athletes

The last three decades have witnessed a tremendous increase in female sports participation at all levels. However, increased sports participation of female athletes has also increased the incidence of sport-related injuries, which can be either acute trauma or overuse injuries. Overuse injuries may be defined as an imbalance caused by overly intensive training and inadequate recovery, which subsequently leads to a breakdown in tissue reparative mechanisms. This article will review the most frequent overuse injuries in female athletes in the context of anatomical, physiological, and psychological differences between genders.

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