1 [Body Systems], 2 [Biomechanics], 3 [Bioenergetics]

Bone periosteum

Specialized connective tissue that tendons attach into on the bone

Myofibril → Muscle organization and connective tissue (4)

1. Myofibril

   1. Sarcoplasmic reticulum/sarcoplasm covering

2. Muscle Fiber (the true muscle cell)

   1. Sarcolemma/endomysium covering, Sarcoplasm/sarcoplasmic reticulum within

3. Fasciculi (bundles of muscle fibers)

   1. Perimysium covering, endomysium within

4. Muscle (bundles of fasciculi)

   1. Epimysium covering, perimysium within

Sarcoplasm contains

• Protein filaments + other protein

• Stored glycogen and fat particles

• Enzymes

• Specialized organelles (myofibrils, mitochondria, sarcoplasmic reticulum, etc.)

Sarcomere

Smallest unit of contractile muscle, making up myofibrils.

H-zone, A-band, I-band, Z-line

H-zone: Middle of the sarcomere containing only myosin

A-band: Any location in the sarcomere where myosin can be found, overlaps with actin

I-band: The area at each end of a sarcomere containing no myosin, only actin

Z-line: The middle of the I-band and thus the boundary of each sarcomere

Calcium ions are stored in _____

vesicles at the ends of sarcoplasmic reticuli

Sarcoplasmic reticulum runs _____ to myofibrils and terminate _____; T-tubules run _____ to sarcoplasmic reticulum and terminate _____

parallel; as vesicles near Z-lines

perpendicular; near vesicles

*So the SR holds calcium ions, and T-tubules signal the release

T-tubules are contiguous with _____, explaining why discharge of an action potential moves nearly instantaneously through the muscle cell

sarcolemma

Sliding filament theory

Actin filaments on each end of the sarcomere are pulled inward and across myosin filaments, pulling the Z-lines toward the center and shortening the H-zone and I-bands (zones of no cross-over)

Excitation-Contraction coupling phase

Before myosin can contract, it first must attach to actin.

1. Calcium is released from the SR by AP (acetylcholine, not nerve) generated along the T-tubule

2. Calcium binds with troponin along actin

3. Tropomyosin is triggered along actin, which myosin can attach to forming a cross-bridge, then allowing for contraction

Contraction/power stroke phase

1. The energy for contraction comes from the hydrolysis of ATP into ADP + phosphate

2. Actin slides over myosin

Relaxation phase

1. Stimulus of motor nerve stops

2. Calcium is pumped back into SR, preventing cross-bridging

3. Actin and myosin filaments return to unbound state

_____ muscle fibers within each motor unit allow for greater precision of movement

Fewer

Twitch

The brief contraction allowed by a single action potential.

In regular use, muscle twitches are summated and delivered with shorter intervals in between to allow for greater muscular contraction

Tetanus

Complete fusing of twitches caused by extremely high frequency stimuli (such as with certain eStim parameters)

Type I, IIa, and IIx fibers

Type I: Slow-twitch, efficient and fatigue-resistant

Type IIa: Fast-twitch, inefficient and fatigable, more capacity for aerobic metabolism

Type IIx:Fast-twitch, most inefficient and fatigable, most capacity for anaerobic metabolism/force development

Muscle Spindles vs Golgi Tendon Organs

Muscle Spindles: Intrafusal muscle fibers activated by stretch and rate of stretch → activate extrafusal fibers in same muscle to meet the force demand proportionally (such as with DTRs). Effect is maximized at low forces

Golgi Tendon Organs: In series with extrafusal muscle fibers at the MTJ and activated by stretch and rate of stretch → inhibit extrafusal fibers in same muscle to protect from excessive strain. Effect is maximized at high forces

*The ability of the motor cortex to override GTO inhibition may be one of the fundamental adaptations to heavy resistance training

The inherent rhythmicity and conduction properties of the myocardium are influenced by the _____

medulla

1st, 2nd, 3rd-class levers

1st: Muscle force and resistance force are on opposite sides of the fulcrum (triceps extension)

2nd: Muscle + resistance on same side, muscle MA is longer (calf raises to ball of foot)

3rd: Muscle + resistance on same side, resistive MA is longer (biceps curl)

Anatomical variation resulting in tendinous insertion further from the joint than usual (increases/decreases) maximum torque output and (increases/decreases) maximum velocity

increases; decreases

Further insertion increases the MA, increasing torque. An increased MA also acts as a larger radius for the circle around the axis of rotation, decreasing angular velocity for a given linear velocity.

Considerations in Strength Measurement

“Strength” is generally defined arbitrarily because total strength output differs based on velocity requirements. Because of individual differences in the ability to exert forces at different velocities, for example, isometric strength testing may not have good predictability for high-velocity athletic movements.

Pounds → kilograms → newtons conversion

lbs / 2.2 = kg

kg * 9.8 = N

Work equation (General) (Joules)

Force * Displacement

Power equation (Watts)

Work / time

Positive Work Calculation (Resistance Exercise)

(Force 1 + Force 2) * Displacement

Force 1: Total weight in newtons (i.e. isometric requirement) = mass (kg) * acceleration due to gravity (9.8)

Force 2: Additional force used to lift the mass at a desired/measured rate of acceleration (i.e. concentric requirement) = mass (kg) * average acceleration of the weight from bottom to top

Displacement: Distance from bottom → top of a free weight exercise, or distance the weight stack moves in machine exercises

Negative Work Calculation (Resistance Exercise)

(Force 1 + Force 2) * Displacement

Force 2 is measured as a negative due to the eccentric nature of the exercise; therefore, the total work done will also be negative and with an absolute value less than the positive work.

Rad and Degree relationship

1 Rad = 57.3 degrees

180 degrees = (pi) rads

Angular Work Equation

Torque (N*m*theta) * Angular displacement (rad)

Strength vs Power

Strength: The capaacity to exert force at any given velocity

Power: A function of force * velocity

Muscle Pennation and Strength relationship

Pennation is the variation in alignment of sarcomeres relative to the long axis of the muscle. Some muscles, like biceps brachii, are fusiform (no pennation) as the muscle fibers are aligned end-to-end. Others, like the rectus femoris, are bipennate (angled into the central tendon).

Muscles with greater pennation have more sarcomeres in parallel but fewer in series; force > velocity.

Muscles with smaller pennation have more sarcomeres in series and fewer in parallel; force < velocity