NetTop20.com

The Fitness Net Top 20 brings you the pick of the most popular and highest-rating sites for fitness on the Net today.

It gives you access to the world’s best fitness sites, all from a single page.

If you like this page you may also want to check out the other Net Top 20 directory listings which link you to the best on the Net in all the most popular categories. 

And they are all at the one easy-to-remember address:

http://fitness.nettop20.com/

Five Best Fitness Tracking Web Sites and Services

One step towards making taking improving your health and well being is taking control over it and making sure you keep an eye on your performance, exercise, and diet. One of the best ways to do that is to sign up for a site or service to help you track your progress to your health goals. Thankfully, there are plenty of sites to help.

Earlier this week we asked you which sites or services you preferred to track your health goals, diet progress, and exercise habits. You responded with dozens of suggestions, and now we’re here to highlight the top five.Photo by Hector Alejandro.

Fitocracy

Fitocracy is a new service, currently in beta, that turns fitness tracking and management into a social game, complete with motivation from others, achievements to unlock, and points to earn to help you “level” as you get in shape. The service boasts an easy to use interface and a wealth of health tracking tools to make sure that if you’re getting in shape that you stay on track, and once you’ve reached your goals you’re able to stick to them.

Fitocracy and its fans weighed in heavily to make it into the top five, and while we normally wouldn’t highlight an invite-only service, Fitocacy has provided 3000 invites to Lifehacker fans who want to try and service themselves. Just use invite code LIFEHACKER to sign up, or follow this link to give it a try.

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MyFitnessPal

MyFitnessPal is a large community of people eager to help one another with their diet, fitness, and overall health goals. It’s built on top of a series of tools to help users easily track their diets, log their meals and exercise routines, track their overall progress, and share their experiences, troubles, and challenges with the community. The service has a massive database of foods and workouts to make it easy to accurately log your meals and exercise, and a users around the world to help you stay motivated and active. It even has mobile apps to help you stay motivated and keep your logs up to date on the go from your iPhone, Android device, BlackBerry, or Windows Mobile phone.

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RunKeeper

Runkeeper puts a social spin on keeping track of your exercise and running habits. The webapp, combined with its Android and iOS apps, can help you monitor your run while you’re out, review your speed and distance progress over time, and help you tailor your workouts for the most impact over time. While Runkeeper doesn’t have a diet or food tracking portion, and it doesn’t boast a built-in community, it does help runners and avid exercisers keep track of their activities, share them with either own friends on Twitter and Facebook, and lets you look back over your past performance. The last time we looked at your favorite exercise tools, Runkeeper came out on top.

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SparkPeople

SparkPeople is actually a network of sites, each targeted at helping you leave a healthier life. The Sparkpeople.com keystone site would be your first stop towards getting involved with a community of people who can help you get active and tools to help you build a diet and exercise program that fits your needs. The site hosts calorie counters and whole meal plans you can customize, fitness programs you can tweak to make your own, and a built-in system that rewards you for sticking to your guns. Of course, the site also gives you reports and tools you can use to monitor your overall progress. From there, you can explore the rest of the SparkPeople network, including a recipe site, a motivational site, even other sites that help you with parenting, personal finance, and more. SparkPeople also has iPhone, Android, and Blackberry apps to use when you’re away from your computer.

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DailyBurn

DailyBurn is a webapp and iPhone app that offer meal tracking, exercise tracking, calorie counting, nutrition tracking, and workout plans that can all be customized to fit your needs. The webapp gives you the ability to monitor your progress and track our performance, and the iPhone app (and its companion apps) let you update your account while on the go, scan food and snap photos of your meals to have them virtually dissected and added to your diet log, and keep an eye on your workout schedule. The service also has a social component and a community of other users who all help motivate one another, either by offering advice and tips or competing with one another on fitness challenges and leaderboards.

6 Week Arm Builder Workout Plan

6 Week Arm Builder Workout Plan

The workout plan helps you build bigger biceps and triceps by increasing exercise effectiveness, volume and intensity over a 6 week period.

Workout Summary

Main Goal:	Build Muscle
Workout Type:	Single Muscle Group
Training Level:	Beginner
Days Per Week:	2
Equipment Required:	Barbell, Cables, Dumbbells, Machines
Target Gender:	Male & Female
Author:	M&S Writers

Workout Description

This arm building approach is broken up into three 2-week segments. The focus of each segment is as follows:

• Weeks 1-2 – Lower volume, low to moderate weight. You will be “easing” into training your arms twice a week.
• Weeks 2-4 – Moderate volume, moderate weight. The intensity and number of sets picks up during this middle segment.
• Weeks 5-6 – You will be training with higher volume and moderate weight. These 2 weeks will be very challenging.

Use as much weight as you can for each set. If you are able to hit the stated rep ranges, add weight the next time you perform the same exercise. After week 6 you may take a week off from training arms, or start the cycle over with week one. Play this by ear. If your arms feel too beat up, a week of rest will do you good.

Workout Schedule

• Workout A – Monday
• Workout B – Thursday

You may adjust this schedule as needed, but always keep as least 2 days off in between each training day.

Weeks 1-2
Workout A – Monday
Exercise	Sets	Rep Goal
Cable Curl	2	12-15
Dumbbell Tricep Kickback	2	12-15
Workout B – Thursday
Exercise	Sets	Rep Goal
Concentration Curl	2	12-15
Cable Tricep Extension	2	12-15

 

Weeks 3-4
Workout A – Monday
Exercise	Sets	Rep Goal
Seated Dumbbell Curl	3-4	10-12
Skullcrusher	3-4	10-12
Workout B – Thursday
Exercise	Sets	Rep Goal
EZ Bar Preacher Curl	3-4	10-12
Seated French Press	3-4	10-12

 

Weeks 5-6
Workout A – Monday
Exercise	Sets	Rep Goal
Barbell Curl	5	8-10
Tricep Dips	5	8-10
Workout B – Thursday
Exercise	Sets	Rep Goal
Chin Ups	5	8-10
Close Grip Bench Press	5	8-10

 

M&S – Beginner Ab Workout

M&S – Beginner Ab Workout

This beginner ab workout hits your abs with 4 sets and 2 exercises. It can be done once or twice a week and added to your current routine.

 

Workout Summary:

• Main Goal: Build Muscle
• Workout Type: Single Muscle Group
• Training Level: Beginner
• Days Per Week: 1-2
• Equipment Required: Bodyweight
• Target Gender: Male & Female
• Author: Doug Lawrenson

 

Workout Description:

This ab workout is designed for beginners to weight training who want to build some muscle and strength in their core. It hits the abs with 4 sets and 2 exercises. The workout can be done once or twice per week, and can be added to the beginning or end of your regular routine.

 

Workout Notes:

1. Perform light warm-up before this workout.
2. Strict technique on all exercises. (see ab exercises)
3. Aim to improve at least one aspect of your workout each week.

 

Weekly Abs Workout Routine:

Ab Exercise:	Sets:	Reps:
Crunches	2	12-15
Lying Knee Raises	2	12-15

 

Workout Diet and Nutrition

Workout Diet and Nutrition

 

If you’re not eating properly, you won’t build much muscle. Many lifters focus all their attention on planning a workout split and training ferociously in the gym, but have no clue how many calories or grams of protein they are eating per day. This won’t cut it.

 

To build muscle you need to monitor your diet just as much, if not more so, than your training. It is not good enough to “just eat healthy.” While healthy eating is a good thing, a muscle building eating plan has specific requirements that must be met:

1. 1.    Calories:

• You must be eating a consistent amount of daily calories. This intake should be substantial enough to allow the body to build muscle. Undereating is one of the major contributers to lack of gains.

1. 2.    Protein:

• You must be monitoring your protein intake. Increasing your daily protein intake while on a resistance training program helps to increase lean muscle mass. The human body is in a constant state of “protein turnover.” Muscle tissue is continuously being repaired and replaced. To maximize this repair, you must maintain a protein positive nitrogen balance.

1. 3.    Carbohydrates:

• Carbohydrates play two key roles in muscle building. The first is energy. Your body needs maximum energy to perform at maximum level. Second, insulin spike post workout. Insulin is the most anabolic hormone in the human body and drives nutrients from the bloodstream into muscle cells. When you finish your workout your muscles are desperately trying to repair and rebuild and are crying out for energy and nutrients. This is the only time when simple carbohydrates will benefit you for muscle building.

1. 4.    Healthy Fats:

• A low fat diet is not always a healthy diet. The body requires healthy fats for a myriad of reasons. Undereating healthy fats can compromise sleep, lower cardiovascular function, slow recovery and increase the likelihood of overtraining. You must be monitoring your fat intake to some degree so that you are certain it is at a productive level.

Definitions and Common Terms

Definitions and Common Terms

The following is a list of common terms found in most muscle building articles and workouts, along with definitions.

• Hypertrophy:
  • Hypertrophy is the process of increasing the size of muscle cells through the use of resistance training. There are two different types of muscular hypertrophy: sarcoplasmic and myofibrillar.
  • Sarcoplasmic Hypertrophy:
    • Sarcoplasmic hypertrophy involves and increase in a cell’s sarcoplasmic fluid without an accompanying increase in strength.
    • Myofibrillar Hypertrophy:
      • Myofibrillar hypertrophy involves a cellular increase in the contractile proteins actin and myosin, which is accompanied by strength increases as well as small increases in muscle size. It should be stated that sarcoplasmic and myofibrillar hypertrophy rarely occur independently, meaning one without the other.
      • Split Workout:
        • A split, or training split, is a workout that targets specific areas of the body rather than working the entire body in one training session. A split workout is usually constructed based on bodyparts, but can also be structured according to movement planes, or in an upper body/lower body type manner. Splits generally range anywhere from a 3 day push, pull, legs split to a 6 day bodypart split.
        • Fullbody Workout:
          • A fullbody workout is a training approach that targets the entire body in each session. Fullbody training is generally performed 3 times per week with at least one day off in between sessions. Some fullbody workouts are performed only twice per week.
          • Progression:
            • Progression is the act of making a workout more difficult over time via the addition of additional weight, volume, or through the inclusion of high intensity or advanced training techniques.
            • Rep:
              • A rep, or repetition, is the act of performing an exercise a single time. Each repetition is comprised of two separate actions: a concentric and eccentric movement. The concentric portion of an exercise involves pulling, pushing or squatting a weight, while the eccentric movement involves lowering or raising the bar back to it’s initial point so that another repetition can be performed.
              • Set:
                • A set is a group or repetitions performed with limited rest in between reps, generally in a near continuous manner.

Body Types and Bone Size Factors

Body Types and Bone Size Factors

There are three primary body types: ectomorph, mesomorph and endomorph.

 

Ectomorph:

• An ectomorph is a typical skinny guy. Ecto’s have a light build with small joints and lean muscle. Usually ectomorph’s have long thin limbs with stringy muscles. Shoulders tend to be thin with little width. Typical traits of an ectomorph:
  • Small “delicate” frame and bone structure
  • Classic “hardgainer”
  • Flat chest
  • Small shoulders
  • Thin
  • Lean muscle mass
  • Finds it hard to gain weight
  • Fast metabolism

Mesomorph:

• A mesomorph has a large bone structure, large muscles and a naturally athletic physique. Mesomorphs are the best body type for bodybuilding. They find it quite easy to gain and lose weight. They are naturally strong which is the perfect platform for building muscle. Typical traits of an mesomorph:
  • Athletic
  • Hard body with well defined muscles
  • Rectangular shaped body
  • Strong
  • Gains muscle easily
  • Gains fat more easily than ectomorphs

Endomorph:

• The endomorph body type is solid and generally soft. Endomorphs gain fat very easily. Endo’s are usually of a shorter build with thick arms and legs. Muscles are strong, especially the upper legs. Endomorphs find they are naturally strong in leg exercises like the squat. Typical traits of an endomorph:
  • Soft and round body
  • Gains muscle and fat very easily
  • Is generally short and “stocky”
  • Round physique
  • Finds it hard to lose fat
  • Slow metabolism

Bodytype Combinations:

• Bodytypes are not set in stone. Most of us are a combination of bodytypes with ectomorph/mesomorph or mesomorph/endomorph being fairly common.

Are You a Beginner, Intermediate or Advanced Lifter?

Are You a Beginner, Intermediate or Advanced Lifter?

The muscle building workouts on Muscle & Strength fall into 3 categories: beginner, intermediate and advanced workouts. Use the following guidelines when trying to decide which workouts are best for you.

Beginner:

• A beginner, or novice, has yet to make a substantial amount of muscle mass gains. They are still trying to figure out proper training and nutrition, or may simply be missing too many gym sessions to make any progress at all.

Intermediate:

• An intermediate has experienced “beginner gains”, and has generally added a minimum of at least 10-15 pounds of muscle. Intermediate lifters know how to eat and train to maximize results in the gym.

Advanced:

• An advanced lifter has reached the point where yearly muscle gains have substantially diminished. They may require more creative training approaches and/or periodization. An advanced lifter looks muscular and impressive in a t-shirt. People will know upon seeing them that they “work out.”

Muscle Contraction

From Wikipedia, the free encyclopedia

  (Redirected from Eccentric contraction)

See also: Twitch (disambiguation) and Tremor

It has been suggested that Sliding filament model be merged into this article or section. (Discuss)Proposed since February 2011.

 

 

Top-down view of skeletal muscle

Muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten, or remain the same. Although the termcontraction implies shortening, when referring to the muscular system, it means muscle fibers generating tension with the help of motor neurons (the terms twitch tension, twitch force, andfiber contraction are also used).

Voluntary muscle contraction is controlled by the central nervous system. The brain sends signals, in the form of action potentials, through the nervous system to the motor neuron thatinnervates several muscle fibers. In the case of some reflexes, the signal to contract can originate in the spinal cord through a feedback loop with the grey matter. Involuntary muscles such as the heart or smooth muscles in the gut and vascular system contract as a result of non-conscious brain activity or stimuli proceeding in the body to the muscle itself.

Contents   [hide]  1 Contractions, by muscle type 1.1 Skeletal muscle contractions 1.1.1 Classification of voluntary muscular contractions 1.2 Smooth muscle contraction 1.2.1 Invertebrate smooth muscles 2 Contractions 2.1 Concentric contraction 2.2 Eccentric contraction 2.2.1 Eccentric contractions in movement 2.3 Isometric contraction 3 Force-length and force-velocity relationships 4 See also 5 Additional images 6 References 7 External links

[edit]Contractions, by muscle type

This section does not cite anyreferences or sources. (August 2009)

For voluntary muscles, all contraction (excluding reflexes) occurs as a result of conscious effort originating in the brain. The brain sends signals, in the form of action potentials, through the nervous system to the motor neuron that innervates several muscle fibers.^[1] In the case of some reflexes, the signal to contract can originate in the spinal cord through a feedback loop with the grey matter. Involuntary muscles such as the heart or smooth muscles in the gut and vascular system contract as a result of non-conscious brain activity or stimuli endogenous to the muscle itself. Other actions such as locomotion, breathing, and chewing have a reflex aspect to them: the contractions can be initiated consciously or unconsciously.

There are three general types of muscle tissues:

• Skeletal muscle responsible for movement
• Cardiac muscle responsible for pumping blood
• Smooth muscle responsible for sustained contractions in the blood vessels, gastrointestinal tract, and other areas in the body

Skeletal and cardiac muscles are called striated muscle because of their striped appearance under a microscope, which is due to the highly organized alternating pattern of A band and I band.

While nerve impulse profiles are, for the most part, always the same, skeletal muscles are able to produce varying levels of contractile force. This phenomenon can be best explained by Force Summation. Force Summation describes the addition of individual twitch contractions to increase the intensity of overall muscle contraction. This can be achieved in two ways:^[2] by increasing the number and size of contractile units simultaneously, called multiple fiber summation, and by increasing the frequency at which action potentials are sent to muscle fibers, called frequency summation.

• Multiple fiber summation – When a weak signal is sent by the CNS to contract a muscle, the smaller motor units, being more excitable than the larger ones, are stimulated first. As the strength of the signal increases, more motor units are excited in addition to larger ones, with the largest motor units having as much as 50 times the contractile strength as the smaller ones. As more and larger motor units are activated, the force of muscle contraction becomes progressively stronger. A concept known as the size principle allows for a gradation of muscle force during weak contraction to occur in small steps, which then become progressively larger when greater amounts of force are required.
• Frequency summation – For skeletal muscles, the force exerted by the muscle is controlled by varying the frequency at which action potentials are sent to muscle fibers. Action potentials do not arrive at muscles synchronously, and, during a contraction, some fraction of the fibers in the muscle will be firing at any given time. In a typical circumstance, when a human is exerting a muscle as hard as he/she is consciously able, roughly one-third of the fibers in that muscle will be firing at once, though this ratio can be affected by various physiological and psychological factors (including Golgi tendon organs and Renshaw cells). This ‘low’ level of contraction is a protective mechanism to prevent avulsion of the tendon—the force generated by a 95% contraction of all fibers is sufficient to damage the body.

[edit]Skeletal muscle contractions

 

 

Muscle fibers in relaxed (above) and contracted (below) positions

 

 

Molecular mechanisms of skeletal muscular function

Skeletal muscles contract according to the sliding filament model see also Excitation-contraction coupling

1. An action potential originating in the CNS reaches an alpha motor neuron, which then transmits an action potential down its own axon.
2. The action potential propagates by activating voltage-gated sodium channels along the axon toward the neuromuscular junction. When it reaches the junction, it causes a calcium ion influx through voltage-gated calcium channels.
3. The Ca²⁺ influx causes vesicles containing the neurotransmitter acetylcholine to fuse with the plasma membrane, releasing acetylcholine out into the extracellular space between the motor neuron terminal and the neuromuscular junction of the skeletal muscle fiber.
4. The acetylcholine diffuses across the synapse and binds to and activates nicotinic acetylcholine receptors on the neuromuscular junction. Activation of the nicotinic receptor opens its intrinsic sodium/potassium channel, causing sodium to rush in and potassium to trickle out. Because the channel is more permeable to sodium, the muscle fiber membrane becomes more positively charged, triggering an action potential.
5. The action potential spreads through the muscle fiber’s network of T-tubules,depolarizing the inner portion of the muscle fiber.
6. The depolarization activates L-type voltage-dependent calcium channels (dihydropyridine receptors) in the T tubule membrane, which are in close proximity to calcium-release channels (ryanodine receptors) in the adjacent sarcoplasmic reticulum.
7. Activated voltage-gated calcium channels physically interact with calcium-release channels to activate them, causing the sarcoplasmic reticulum to release calcium.
8. The calcium binds to the troponin C present on the actin-containing thin filaments of themyofibrils. The troponin then allosterically modulates the tropomyosin. Under normal circumstances, the tropomyosin sterically obstructs binding sites for myosin on the thin filament; once calcium binds to the troponin C and causes an allosteric change in the troponin protein, troponin T allows tropomyosin to move, unblocking the binding sites.
9. Myosin (which has ADP and inorganic phosphate bound to its nucleotide binding pocket and is in a ready state) binds to the newly uncovered binding sites on the thin filament (binding to the thin filament is very tightly coupled to the release of inorganic phosphate). Myosin is now bound to actin in the strong binding state. The release of ADP and inorganic phosphate are tightly coupled to the power stroke (actin acts as a cofactor in the release of inorganic phosphate, expediting the release). This will pull the Z-bands towards each other, thus shortening the sarcomere and the I-band.
10. ATP binds myosin, allowing it to release actin and be in the weak binding state (a lack of ATP makes this step impossible, resulting in the rigor state characteristic of rigor mortis). The myosin then hydrolyzes the ATP and uses the energy to move into the “cocked back” conformation. In general, evidence (predicted and in vivo) indicates that each skeletal muscle myosin head moves 10–12 nm each power stroke, however there is also evidence (in vitro) of variations (smaller and larger) that appear specific to the myosin isoform.
11. Steps 9 and 10 repeat as long as ATP is available and calcium is present on thin filament.
12. While the above steps are occurring, calcium is actively pumped back into the sarcoplasmic reticulum. When calcium is no longer present on the thin filament, the tropomyosin changes conformation back to its previous state so as to block the binding sites again. The myosin ceases binding to the thin filament, and the contractions cease.

The calcium ions leave the troponin molecule in order to maintain the calcium ion concentration in the sarcoplasm. The active pumping of calcium ions into the sarcoplasmic reticulum creates a deficiency in the fluid around the myofibrils. This causes the removal of calcium ions from the troponin. Thus, the tropomyosin-troponin complex again covers the binding sites on the actin filaments and contraction ceases.

[edit]Classification of voluntary muscular contractions

Skeletal muscle contractions can be broadly separated into twitch and tetanic contractions. In a twitch contraction, a short burst of stimulation causes the muscle to contract, but the duration is so short that the muscle begins relaxing before reaching peak force. The shape of the graph of force vs time in a twitch contraction can give information about the relative rates of calcium release and re-uptake from the sarcoplasmic reticulum. If the stimulation is long enough, the muscle reaches peak force and plateaus at this level, resulting in a tetanic contraction. If the stimulation is not intense enough, force will oscilate during the plateau and be submaximal, but with sufficient stimulation, there will be a constant force level until stimulation stops.

Voluntary muscular contractions can be further classified according to either length changes or force levels. In spite of the fact that the muscle actually shortens only in concentric contractions, all are typically referred to as “contractions”.

• In concentric contraction, the force generated is sufficient to overcome the resistance, and the muscle shortens as it contracts. This is what most people think of as a muscle contraction.
• In eccentric contraction, the force generated is insufficient to overcome the external load on the muscle and the muscle fibers lengthen as they contract. An eccentric contraction is used as a means of decelerating a body part or object, or lowering a load gently rather than letting it drop.
• In isometric contraction, the muscle remains the same length. An example would be holding an object up without moving it; the muscular force precisely matches the load, and no movement results.
• In isotonic contraction, the tension in the muscle remains constant despite a change in muscle length. This can occur only when a muscle’s maximal force of contraction exceeds the total load on the muscle.
• In isovelocity contraction (sometimes called “isokinetic”), the muscle contraction velocity remains constant, while force is allowed to vary. True isovelocity contractions are rare in the body, and are primarily an analysis method used in experiments on isolated muscles that have been dissected out of the organism.

In reality, muscles rarely perform under any sort of constant force, velocity, or speed, but these contractions are useful for understanding overall muscle properties present in more complex contractions that occur in vivo. Cyclic in vivo contractions can be modeled using work loops.

[edit]Smooth muscle contraction

Further information: Smooth muscle

The interaction of sliding actin and myosin filaments is similar in smooth muscle. There are differences in the proteins involved in contraction in vertebrate smooth muscle compared to cardiac and skeletal muscle. Smooth muscle does not contain troponin, but does contain the thin filament protein tropomyosin and other notable proteins – caldesmon and calponin. Contractions are initiated by the calcium-activated phosphorylation of myosin rather than calcium binding to troponin. Contractions in vertebrate smooth muscle are initiated by agents that increase intracellular calcium. This is a process of depolarizing the sarcolemma and extracellular calcium entering through L-type calcium channels, and intracellular calcium release predominately from the sarcoplasmic reticulum. Calcium release from the sarcoplasmic reticulum is from Ryanodine receptor channels (calcium sparks) by a redox process and Inositol triphosphate receptor channels by the second messenger inositol triphosphate. The intracellular calcium binds with calmodulin, which then binds and activatesmyosin light-chain kinase. The calcium-calmodulin-myosin light-chain kinase complex phosphorylates myosin on the 20 kilodalton (kDa) myosin light chains on amino acid residue-serine 19, initiating contraction and activating the myosin ATPase. The phosphorylation of caldesmon and calponin by various kinases is suspected to play a role in smooth muscle contraction.

Phosphorylation of the 20 kDa myosin light chains correlates well with the shortening velocity of smooth muscle. During this period, there is a rapid burst of energy utilization as measured by oxygen consumption. Within a few minutes of initiation, the calcium level markedly decreases, the 20 kDa myosin light chains’ phosphorylation decreases, and energy utilization decreases; however, force in tonic smooth muscle is maintained. During contraction of muscle, rapidly cycling crossbridges form between activated actin and phosphorylated myosin, generating force. It is hypothesized that the maintenance of force results from dephosphorylated “latch-bridges” that slowly cycle and maintain force. A number of kinases such as Rho kinase, Zip kinase, and Protein Kinase C are believed to participate in the sustained phase of contraction, and calcium flux may be significant.

[edit]Invertebrate smooth muscles

In invertebrate smooth muscle, contraction is initiated with calcium directly binding to myosin and then rapidly cycling cross-bridges generating force. Similar to vertebrate tonic smooth muscle, there is a low calcium and low energy utilization catch phase. This sustained phase or catch phase has been attributed to a catch protein that is similar to myosin light-chain kinase and titin, called twitchin.

[edit]Contractions

[edit]Concentric contraction

A concentric contraction is a type of muscle contraction in which the muscles shorten while generating force.

During a concentric contraction, a muscle is stimulated to contract according to the sliding filament mechanism. This occurs throughout the length of the muscle, generating force at the musculo-tendinous junction, causing the muscle to shorten and changing the angle of the joint. In relation to the elbow, a concentric contraction of the biceps would cause the arm to bend at the elbow as the hand moved from near to the leg to close to the shoulder (a biceps curl). A concentric contraction of the triceps would change the angle of the joint in the opposite direction, straightening the arm and moving the hand towards the leg.

[edit]Eccentric contraction

During an eccentric contraction, the muscle elongates while under tension due to an opposing force being greater than the force generated by the muscle.^[3] Rather than working to pull a joint in the direction of the muscle contraction, the muscle acts to decelerate the joint at the end of a movement or otherwise control the repositioning of a load. This can occur involuntarily (when attempting to move a weight too heavy for the muscle to lift) or voluntarily (when the muscle is ‘smoothing out’ a movement). Over the short-term, strength traininginvolving both eccentric and concentric contractions appear to increase muscular strength more than training with concentric contractions alone.^[4]

During an eccentric contraction of the biceps muscle, the elbow starts the movement while bent and then straightens as the hand moves away from the shoulder. During an eccentric contraction of the triceps muscle, the elbow starts the movement straight and then bends as the hand moves towards the shoulder. Desmin, titin, and other z-line proteins are involved in eccentric contractions, but their mechanism is poorly understood in comparison to cross-bridge cycling in concentric contractions.^[3]

Muscles undergoing heavy eccentric loading suffer greater damage when overloaded (such as during muscle building or strength trainingexercise) as compared to concentric loading. When eccentric contractions are used in weight training, they are normally called negatives. During a concentric contraction, muscle fibers slide across each other, pulling the Z-lines together. During an eccentric contraction, the filaments slide past each other the opposite way, though the actual movement of the myosin heads during an eccentric contraction is not known. Exercise featuring a heavy eccentric load can actually support a greater weight (muscles are approximately 40% stronger during eccentric contractions than during concentric contractions) and also results in greater muscular damage and delayed onset muscle soreness one to two days after training. Exercise that incorporates both eccentric and concentric muscular contractions (i.e. involving a strong contraction and a controlled lowering of the weight) can produce greater gains in strength than concentric contractions alone.^[4][5]While unaccustomed heavy eccentric contractions can easily lead to overtraining, moderate training may confer protection against injury.^[4]

[edit]Eccentric contractions in movement

Eccentric contractions normally occur as a braking force in opposition to a concentric contraction to protect joints from damage. During virtually any routine movement, eccentric contractions assist in keeping motions smooth, but can also slow rapid movements such as a punch or throw. Part of training for rapid movements such as pitching during baseball involves reducing eccentric braking allowing a greater power to be developed throughout the movement.

Eccentric contractions are being researched for their ability to speed rehab of weak or injured tendons. Achilles tendinitis has been shown to benefit from high-load eccentric contractions.^[6][7]

[edit]Isometric contraction

Main article: Isometric exercise

An isometric contraction of a muscle generates force without changing length. An example can be found when the muscles of the handand forearm grip an object; the joints of the hand do not move, but muscles generate sufficient force to prevent the object from being dropped.

[edit]Force-length and force-velocity relationships

For more details on this topic, see Hill’s muscle model.

Unlike mechanical systems such as motors, the force a muscle can generate depends upon both the length and shortening velocity of the muscle.

 

 

Muscle length versus isometric force

Force-length relationship, also called the length-tension curve, relates the strength of an isometric contraction to the length of the muscle at which the contraction occurs. Muscles operate with greatest active force when close to an ideal length (often their resting length). When stretched or shortened beyond this (whether due to the action of the muscle itself or by an outside force), the maximum active force generated decreases.^[8] This decrease is minimal for small deviations, but the force drops off rapidly as the length deviates further from the ideal. As a result, in most biological systems, the range of muscle contraction will remain on the peak of the length-tension curve, in order to maximize contraction force (a notable exception is cardiac muscle which functions on ascending limb so it can increase force when stretched by an increase in preload-Starling’s law). Due to the presence of elastic proteins within a muscle (such as titin), as the muscle is stretched beyond a given length, there is an entirely passive force, which opposes lengthening. Combined together, we see a strong resistance to lengthening an active muscle far beyond the peak of active force.

 

 

Force–velocity relationship: right of the vertical axis concentric contractions (the muscle is shortening), left of the axis excentric contractions (the muscle is lengthened under load); power developed by the muscle in red.

Force–velocity relationship: The speed at which a muscle changes length (usually regulated by external forces, such as load or other muscles) also affects the force it can generate. Force declines in a hyperbolic fashion relative to the isometric force as the shortening velocity increases, eventually reaching zero at some maximum velocity. The reverse holds true for when the muscle is stretched – force increases above isometric maximum, until finally reaching an absolute maximum. This has strong implications for the rate at which muscles can perform mechanical work (power). Since power is equal to force times velocity, the muscle generates no power at either isometric force (due to zero velocity) or maximal velocity (due to zero force). Instead, the optimal shortening velocity for power generation is approximately one-third of maximum shortening velocity.

These two fundamental properties of muscle have numerous biomechanical consequences, including limiting running speed, strength, and jumping distance and height.

 

8 Sets Of 8

8 Sets Of 8

8 x 8 is designed to rapidly build muscle while at the same time reduce body fat.

The 8 x 8 is also a wonderful program to follow when you hit a sticking point and need to shock muscles into a new growth pattern, whether it is an individual muscle or your entire body.

Rules:

1. You must move quickly with minimum rest during the entire workout. Each session should last no longer than about thirty minutes. The speed in which you perform each movement should be quick but not jerky and you must adhere to strict form and rest no longer then 15 seconds between movements.
2. Do not drink water during your workout session or immediately after. Wait at least forty-five minutes after your session and then sip water slowly.
3. Concentrate on each movement. No outside distractions and no talking during the workout.
4. Follow the routine exactly as outlined and do not adjust the order in which the movements are listed.
5. Intermediate trainers should follow this routine 1x per day. Advanced trainers could follow it 2x per day. Pros could follow it 3x per day.
6. One with less than two solid years of training behind them should not attempt the 8 sets of 8 routine.
7. Vince advised taking a nap after each session to help the body recuperate and recover.
8. This is important for understanding the 8 sets of 8 and how to perform it, at least the way it was given to me. Take the chest for example. You will perform one set of 8 reps of Barbell Bench Press To The Neck then immediately, super-set fashion; perform 8 reps of the “V” Bar Dips. Rest a maximum of fifteen to thirty seconds; you will then repeat this sequence. Perform it four times. In other words, you do not perform 8 sets of presses and 8 sets of dips; you actually perform 4 sets of presses and 4 sets of dips for a total of eight sets.
   1. The exception to this is the Wednesday and Friday leg workouts. On these days, you perform 4 sets of each exercise listed in straight set fashion. Occasionally I would perform them in giant set fashion but you had better be in shape because it will really drain you. I use to perform them in giant set fashion on Saturdays only, because I knew I would get an extra day of rest on Sunday with no workout scheduled and believe me I needed it. Only the most advanced trainer should attempt performing them in giant set fashion.

 

 

Routine:

Monday & Thursday Chest – Back – Shoulders

	Exercise	Sets
Chest	Barbell Bench Press To The Neck
Chest	“V” Bar Dips
Back
Back
Shoulders
Shoulders