Three Ways A Muscle Generates Force or Tension
1. Isometrically- (Latin- Iso: same, metric: length) muscle generates force or tension w/ no change in length. Isometric endurance and strength is critical to every day life. IE posture muscles work isometrically to keep you in an upright position. Another example is performing the Iron Cross on the rings. Another example of an isometric workout is to stay in the pushup position without performing the pushup. Your abs and triceps are engaged but not lengthening or contracting.
2. Isotonically- (Latin- Iso: same, tonic: tension- this is an inaccurate term) muscle generates force while either shortening or lengthening.
A. Concentric- muscle generates force or tension while shortening
B. Eccentric- muscle generates force or tension while lengthening. Vast majority or DOMS is related to eccentric exercise.
Reason why Isotonic is inaccurate: Torque (T)= Force (F) x Distance (d_ )
(where d_ = distance perpendicular)
A. Concentric- muscle generates force or tension while shortening
B. Eccentric- muscle generates force or tension while lengthening. Vast majority or DOMS is related to eccentric exercise.
Reason why Isotonic is inaccurate: Torque (T)= Force (F) x Distance (d_ )
(where d_ = distance perpendicular)
T90* = (10 lbs.)(16 in.)= 160 in. lbs.
Where d is the distance from the axis of rotation (joint) to the center of gravity of the resistance (weight).
Where d is the distance from the axis of rotation (joint) to the center of gravity of the resistance (weight).
T140*= (10 lbs.)(14 in.)=140 in. lbs.
NOT the same tension throughout the full range of motion. NSCA does not use the term Isotonic. They use any combination of the following: Dynamic Constant External Resistance (DCER, DR, CDER, CER)
NOT the same tension throughout the full range of motion. NSCA does not use the term Isotonic. They use any combination of the following: Dynamic Constant External Resistance (DCER, DR, CDER, CER)
Any difference, from other people, in where your bicep inserts on your radius determines differences in lifting capabilities. This is genetically determined. The difference can be as small as .5 mm but translate into a large difference in lifting capabilities. This determines the “Sticking Point” also. (See pg. 69 of NSCA book). The average sticking point for bench press is about 4 inches off the chest.
STICKING POINT: Aside from the definition on pg. 69 of the NSCA book, according to Physiological Aspects of Sport Training and Performance by Jay Hoffman, Sticking Point refers to the joint angle position of the contraction in which the muscle is the weakest.
3. Isokinetically- (Latin- Iso: same, kinetic: speed/motion) A near maximal effort at a constant speed throughout an entire range of motion (ROM). Only way to do this type of exercise accurately is with an expensive machine often found in physical therapy labs. Mostly used in rehab. (Cybex, Kintron, Med-X machines) These machines keep the speed of motion constant but change the resistance. The machine gives less resistance at your weakest point, and most resistance at your strongest. This is called Accommodation Resistance. This machine is primarily used in physical training facilities because it shuts down when you stop pushing and it gives you a read out.
Theories of the causes of DOMS (Delayed Onset of Muscle Soreness)
1. SPASM theory:
When you work out a muscle aggressively, you have micro-muscle spasms you don’t feel. This happens naturally. These spasms push the muscles against arteries and veins collapsing them. Support for this theory is that stretching and massage helps decrease DOMS.
1. SPASM theory:
When you work out a muscle aggressively, you have micro-muscle spasms you don’t feel. This happens naturally. These spasms push the muscles against arteries and veins collapsing them. Support for this theory is that stretching and massage helps decrease DOMS.
2. TEAR theory:
When you exercise a muscle, you actually destroy the muscles in order to build them back up. In order to heal these tears, your body uses enzymes. The by-products of this repair process of the enzymes are said to create discomfort in the muscles causing DOMS.
When you exercise a muscle, you actually destroy the muscles in order to build them back up. In order to heal these tears, your body uses enzymes. The by-products of this repair process of the enzymes are said to create discomfort in the muscles causing DOMS.
3. LACTATE ACCUMULATION theory:
Muscle produces lactate & H+ ions. This CANNOT be a reason for DOMS because even with rest recovery, it still only takes 2 hrs. for these to be cleared from the muscle. This theory has been disproved.
Muscle produces lactate & H+ ions. This CANNOT be a reason for DOMS because even with rest recovery, it still only takes 2 hrs. for these to be cleared from the muscle. This theory has been disproved.
4. CONNECTIVE TISSUE DAMAGE theory:
This theory has the most credibility. Damage associated with eccentric movements to connective tissue. (See pg. 5 of NSCA book). Every muscle structure is separated by connective tissue. All the connective tissue comes together & connects to the bone (as a tendon). Hydroxyproline is a by-product of connective tissue damage. This means you can use it as a marker of damage to the joints. Hydroxyproline has been shown to be most present in the body around 2 days after exercise, the same time DOMS sets in.
This theory has the most credibility. Damage associated with eccentric movements to connective tissue. (See pg. 5 of NSCA book). Every muscle structure is separated by connective tissue. All the connective tissue comes together & connects to the bone (as a tendon). Hydroxyproline is a by-product of connective tissue damage. This means you can use it as a marker of damage to the joints. Hydroxyproline has been shown to be most present in the body around 2 days after exercise, the same time DOMS sets in.
In one study, Tom had to perform very aggressive negative (eccentric) resistance training. They had him do 90% of his 1 RM as many times as he could but only the eccentric portion of the exercise. The highest concentration of hydroxyproline in his urine was at 48 hrs. after the testing was done.
Three of these theories contribute to do with DOMS.
Your endurance and strength significantly decrease during DOMS. It is suggested not to work out aggressively during this time.
You should NOT get DOMS every time you work out. This is a sign of over training.
MOTOR UNIT: A motor unit nerve and all the muscle fibers it innervates.
Each muscle fiber only has one motor nerve that innervates it. For subtle movements you recruit motor nerves that innervate less muscle fibers. For big/explosive movements you recruit motor nerves that innervate a lot of muscle fibers.
Repetition of training makes the body more efficient at this.
Repetition of training makes the body more efficient at this.
SKELETAL MUSCLE FIBER TYPE CHARACTERISTICS (9 characteristics)
1. Three types of skeletal muscle
* Slow twitch: ST, red, type I, slow oxidative (so)
* Fast twitch a: FT a, pink, type IIa, fast oxidative Glycolitic (FOG)
* fast twitch b: FT b, white, type II b, fast glycolitic (FG)
* Slow twitch: ST, red, type I, slow oxidative (so)
* Fast twitch a: FT a, pink, type IIa, fast oxidative Glycolitic (FOG)
* fast twitch b: FT b, white, type II b, fast glycolitic (FG)
Different muscles have completely different % of fast/slow twitch fibers. To have your fast/slow twitch analyzed, a biopsy is taken from a muscle and studied under a microscope. The three different fiber types are counted separately and divided by the total number of fibers under the microscope. Unfortunately, these % have no use. This is because depth into muscle, proximity to tendons, and other factors influence how many fast twitch and slow twitch fibers there will be.
Not only does the same muscle vary within itself, but each muscle differs greatly from one another in amount of slow/fast twitch fibers they contain. Posture muscles are composed of mainly slow twitch muscles (60% ST, 40% FT). The triceps is 60% FT, 40% ST.
The average American has 50% ST, 25% FT a, and 25% FT b.
2. Energy Pathway Potential
ST: Oxidative (High oxidative capacity, low glycolitic capacity)
FTa: Aerobic & Anaerobic (High oxidative capacity, high glycolitic capacity). Starts mimicing
ST and FTb if you have a great training program. This is why you don't train resistance
ST and FTb if you have a great training program. This is why you don't train resistance
athletes aggresively in aerobic sports.
FTb: Anaerobic (Low oxidative capacity, high glycolitic capacity.
Slow Twitch
Stores 3 x more muscle triglycerides (because it uses the oxidative system it can use fat)
stores same amount of muscle glycogen
better suited for aerobic system
Slow Twitch
Stores 3 x more muscle triglycerides (because it uses the oxidative system it can use fat)
stores same amount of muscle glycogen
better suited for aerobic system
Fast Twitch
Enzymes used by the CP-ATP system are 3 x more active
Stores same amount of muscle glycogen
better suited for anaerobic system
Enzymes used by the CP-ATP system are 3 x more active
Stores same amount of muscle glycogen
better suited for anaerobic system
3. Speed of Contraction
FT contracts faster. FT can contract in 1/3 the time of a ST. This is because the energy system it uses is faster but also because the motor nerves that innervate FT fibers are thicker. The brain can send a message faster down larger diameter nerves. This means you must not only train the muscle but also the nervous system. The nerves make a muscle ST or FT, not the muscle itself necessarily.
4. Force of Contraction
FT can generate a more forceful contraction. Motor nerves that innervate FT innervate more muscle fibers. Specificity of Training: to be explosive you must teach the muscles with explosive exercise. To be a high duration low intensity athlete, you must train with low intensity and high duration exercise.
FT can generate a more forceful contraction. Motor nerves that innervate FT innervate more muscle fibers. Specificity of Training: to be explosive you must teach the muscles with explosive exercise. To be a high duration low intensity athlete, you must train with low intensity and high duration exercise.
5. Force-Velocity Curve
Graph. We are at our strongest at 0 movement (isometric resistance). Our ability to generate force decreases with velocity (speed of movement).
Graph. The graph of the trained person moves up and to the right from an untrained person. At the same velocity, a trained person can produce 15% more force than the untrained person. At the same force, a trained person's speed can increase 85% above the untrained person's.
Graph. We are at our strongest at 0 movement (isometric resistance). Our ability to generate force decreases with velocity (speed of movement).
Graph. The graph of the trained person moves up and to the right from an untrained person. At the same velocity, a trained person can produce 15% more force than the untrained person. At the same force, a trained person's speed can increase 85% above the untrained person's.
6. Recruitment
High intensity low duration: body prefers to use FT. Low intensity high duration: body prefers to use ST.
High intensity low duration: body prefers to use FT. Low intensity high duration: body prefers to use ST.
7. Distribution in Athletes
Vertical jump is a good indication of fast twitch muscle fibers. Athletes who excel at low intensity high duration sports probably have a lot more slow twitch fibers and therefore may not excel in high intensity low duration sports. Eg Flo Joe who excelled at sprinting but could not excel at running long distances due to the great difference in FT to ST muscle fibers in her body.
Vertical jump is a good indication of fast twitch muscle fibers. Athletes who excel at low intensity high duration sports probably have a lot more slow twitch fibers and therefore may not excel in high intensity low duration sports. Eg Flo Joe who excelled at sprinting but could not excel at running long distances due to the great difference in FT to ST muscle fibers in her body.
8. Heredity
We are born with a certain number of FT and ST muscle fibers. These #s cannot be changed. They are determined by genetics: 99.9% genetically determined in males, 92.2% genetically determined in females.
We are born with a certain number of FT and ST muscle fibers. These #s cannot be changed. They are determined by genetics: 99.9% genetically determined in males, 92.2% genetically determined in females.
9. Fatigability
Slow Twitch
6 Reasons why they fatigue
1. Muscle glycogen depletion
2. Liver (and thus blood glucose) glycogen depletion
(Hypoglycemia)
3. Dehydration
4. Electrolyte loss (especially in excessive heat-sweating electrolytes)
5. Increased core body temperature
6. Boredom
6 Reasons why they fatigue
1. Muscle glycogen depletion
2. Liver (and thus blood glucose) glycogen depletion
(Hypoglycemia)
3. Dehydration
4. Electrolyte loss (especially in excessive heat-sweating electrolytes)
5. Increased core body temperature
6. Boredom
Fast Twitch
Fatigues faster because of its energy system
1. Fatiguing by-products (H+)
Must train athletes to use anaerobic Glyc. System and deal with high levels of H+. To be able to metabolize them faster and work at partial recovery (tolerated and clear faster).
Fatigues faster because of its energy system
1. Fatiguing by-products (H+)
Must train athletes to use anaerobic Glyc. System and deal with high levels of H+. To be able to metabolize them faster and work at partial recovery (tolerated and clear faster).
http://www.brianmac.co.uk/muscle.htm
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