Muscle Aches, Soreness, and Pathology

Muscle aches

Occur from tension, overuse, muscle injury, and may involve muscles, tendons, ligaments, and fascia. They can also be a sign of conditions like flu, lupus, or fibromyalgia.

DOMS (Delayed onset muscle soreness)

Soreness pain that occurs 24-48 hours after exercise, often caused by microtears in muscle fibers which lead to inflammation. Eccentric contraction exercises may cause more microtears.

Active recovery

The recommended method for dealing with muscle soreness, which requires blood moving through the muscles.

Tetanus (disease)

A condition caused by the toxin from Clostridium tetani, which blocks the release of glycine (an inhibitory neurotransmitter in the spinal cord). This leads to the overstimulation of motor neurons of muscle cells and causes excessive muscle contraction.

Botulism

A condition caused by the toxin from Clostridium botulinum (an anaerobic bacteria). The toxin prevents the release of Acetylcholine (ACh) at synaptic terminals, resulting in muscular paralysis.

Botulism A

Repeated applications of this toxin can be used to reduce wrinkles.

Spasticity

The over contraction of muscles. Botulism A is used to reduce spasticity and treat conditions such as cerebral palsy, muscular sclerosis, strokes, and spinal cord injuries.

Hydroxy apatite

A substance formed when Ca++ binds with PO4 ions that were released from ATP; its formation can calcify and harden muscles.

Myosin (thick) heads

Re-setting these heads is the process for which most of the ATP produced for muscle cells during contraction is utilized.

Skeletal Muscle Relaxation

This requires the termination of rapid nerve signals, which stops ACh release. This leads to the closure of ACh receptors on the sarcolemma and a decrease in Ca++ channels in the sarcoplasmic reticulum and T-tubules, causing Ca++ to return to storage.

ATP in Relaxation

ATP is required for both contraction and relaxation of muscles. Specifically, ATP is used to cause Ca++ pumps to be active in keeping Ca++ in the cytosol low.

Rigor mortis

A state where muscle relaxation does not occur, and muscles stay contracted, because insufficient ATP is available (as in death).

Myokinase

An enzyme involved in the transfer of P from ADP to ATP. The ATP produced this way, along with limited ATP stores within the muscle fibers, is good for 5-6 seconds of maximum exercise.

Creatine PO4

High energy bonds stored with PO4 in muscle and brain cells. The phosphorus is transferred from Creatine PO4 to ADP, yielding ATP. This pathway allows for an additional 20-25 seconds of maximum exertion.

Creatine kinase

The enzyme involved when some ATP is used during rest to build more creatine PO4.

Rest

The time when the limited stores of ATP and Creatine PO4 are replenished, with ATP formed in cellular respiration helping to restore reserves.

Glycolysis

An ATP formation process using glucose from glycogen stores within muscle fibers or delivered by the blood. Its advantages are that no O2 is needed, and the rate of production is rapid (twice as fast as aerobic cellular respiration).

Aerobic Respiration/Cellular Respiration

This process occurs within the mitochondria and requires O2 from the blood or myoglobin. Its advantages include utilizing a variety of nutrients (glucose, fatty acids, amino acids, etc.) and yielding greater amounts of ATP. At rest, skeletal muscle obtains the needed ATP almost exclusively from aerobic cellular respiration.

Lactate formation

Occurs when O2 is low due to increased exercise intensity. The enzyme involved is lactase dehydrogenase.

Lactate destination

Lactate either enters the mitochondria within the muscle fiber or the blood, where it may be taken up by cardiac muscle and oxidized to pyruvate, or it is taken up by the liver and converted to glucose (glucogenesis).

Glucogenesis

The process undertaken by the liver to convert lactate back to glucose.

50-yard sprint (ATP source)

Takes 5-6 seconds; ATP is supplied almost entirely from stored ATP and the P transfer between two ADP molecules and between creatine PO4 and ADP.

400-meters (ATP source)

ATP is initially supplied by stored ATP/CP, then by glycolysis, and subsequently by lactic acid fermentation.

1500 meters (ATP source)

ATP is supplied by all three means (stored ATP/CP, glycolysis, and aerobic respiration), but primarily from aerobic cellular respiration.

O2 debt (Oxygen Debt)

Incurred during exercise when the demand for O2 exceeds the available O2.

Definition of O2 debt

The amount of additional O2 that is consumed following exercise to restore pre-exercise conditions.

Uses of Additional O2 (To pay off the debt)

Required primarily to replace O2 on myoglobin molecules, replenish ATP and Creating PO4, replace glycogen stores, allow the liver to convert lactate back to glucose through glucogenesis, support respiratory muscles engaging in forced breathing, allow the heart to pump more blood, and support the overall higher metabolic rate.