4 [Endocrine], 5 [Anaerobic Adaptations], 6 [Aerobic Adaptations]

Categories of Hormones

• Steroid

• Polypeptide

• Amine

Steroid Characteristics

Produced in the adrenal cortex (e.g., cortisol) and gonads (e.g., testosterone and estradiol).

Fat-soluble, passively diffuse across cell membranes.

Polypeptide Characteristics

E.g., growth hormone and insulin.

Made up of chains of amino acids (not fat-soluble) and must bind to the outside of the cell.

Amine Characteristics

Synthesized from the amino acid tyrosine (e.g., epinephrine, norepinephrine, dopamine) and tryptophan (e.g., serotonin).

Bind to hormone receptors on the cell membrane but are not regulated via negative feedback.

Endocrine Response Specificity

On stimulation of a motor unit by the motor cortex, various signals are sent from the brain and activated muscle to the endocrine glands.

The type of exercise protocol initiated will determine the extent of the endocrine system’s involvement.

Endocrine Adaptations to Exercise (6)

• Amount of synthesis and storage of hormones

• Transport of hormones via binding proteins

• Clearance time / hormonal half-life

• Blood-to-tissue fluid shift during exercise

• Receptor count in the tissue

• Magnitude of signal/degree of interaction with cell nucleus

Primary Anabolic Hormones (3)

• Testosterone

• GH

• IGFs

Exercise Variables that increase Serum Testosterone Concentration

• Large muscle group exercises (e.g., deadlift, power clean, squat… but not bench presses)

• Heavy resistance >85% 1RM

• Moderate-high volume of exercise, achieved with multiple sets, multiple exercises, or both

• Short rest intervals

*These do not all have to be done at the same time - you can see that not all of these are compatible for the same exercise program.

Diurnal Variation

Normal fluctuations in hormone levels throughout the day

Time of Day and Exercise

Time of day has NOT been shown to have an effect on resting testosterone, diurnal patterns, or absolute increase in maximum strength.

Women and Serum Testosterone/GH

Women have much lower concentrations of serum testosterone; however, the response of their androgen receptors is very dynamic, allowing for faster upregulation to better use the amount of testosterone present.

Serum GH in women fluctuates throughout their menstrual cycle, being especially higher than men during their follicular phase.

Training Adaptations of Testosterone

Acute increases in serum concentration of test. appear more significant than chronic adaptations.

The major player here is actually the increase in androgen receptor content within skeletal muscle, creating a better ability to utilize test.

GH “Superfamily”

The blood is filled with GH splice variants in different molecular weight combinations. Additionally, there are two types of GH binding proteins that also increase molecular weight.

This is contrary to the previous belief in only one form of GH.

GH Superfamily Physiological Roles

• Decrease glucose utilization/glycogen synthesis

• Increased amino acid transport and protein synthesis

• Increased utilization of fatty acids and lipolysis

• Increased collagen synthesis

• Stimulates cartilage growth

• Increased retention of nitrogen, sodium, potassium, and phosphorous

• Increased renal function

• Enhanced immune cell function

Measuring Anabolic Hormone changes post-exercise

Testosterone: Sooner the better, with marked fall-off after 4-hours

GH: GH concentrations need to be measured over longer time periods (2-24 hours) to show whether acute changes occur. The area under the time curve, which includes the usual pulsatile nature of GH, tells whether changes in release have occurred.

IGF: Acute changes to IGF depend on the starting concentration. Lower concentration elicits higher IGF concentration postexercise, while a higher starting concentration elicits little effect.

^These are all for SERUM levels, and do not reflect the full endocrine adaptation to exercise, which includes receptor up/downregulation, hormone storage/transport, etc.

IGF Function

Synthesis is stimulated by GHs to mediate GHs.

IGF-1 Significance

Most prolific anabolic protein IGF superfamily

Theory of IGF Production postexercise

IGF in the liver takes 8 to 24 hours to synthesize after GH stimulus, so it must be coming from somewhere else.

Fat cells, which have a high concentration of IGF, are believed to be “disrupted” during exercise, releasing their biostores of IGF that is then used by skeletal muscle.

Adrenal Hormones important to Training

Cortisol (Cortex, hormone-mediated) and Catecholamines (Medulla, neural-mediated)

Cortisol Role

White knight of the glucose

• Inhibits protein synthesis and increases proteolytic enzymes

• Stimulates gluconeogenesis (from amino acids)

• Suppresses glucose-dependent processes (e.g. glycogenolysis and immune cell function)

Historically described as a pure catabolic hormone, its role is really to preserve as much glucose as possible (which ends up being catabolic for protein/muscle).

More significant effect on type II fibers than type I fibers.

Function of Cortisol in Exercise Adaptation

While chronically high cortisol has adverse effects, acute increases in cortisol may actually be a part of the remodeling process of muscle, removing damaged proteins so that new ones can be added in.

Indication of Overtraining by Cortisol Levels

>800 nmol/L

Catecholamines and Role

Epi, norepi, and dopamine. Secreted by adrenal medulla.

Important for the acute expression of strength/power, acting as central motor stimulators, peripheral vascular dilators, enzyme enhancers, and calcium-release enhancers. They also augment secretion of other anabolic hormones.

Exercise Variables that increase Serum 22 kDa GH Concentration

• Workout with higher lactate concentrations and associated acid-base disruptions (high intensity, 3 sets, short rest)

• Supplement diet with cabs and protein before and after workouts

Anaerobic Alactic vs Lactic system

Alactic: Phosphagen

Lactic: Glycolytic

Neural Adaptations to Anaerobic Training

• Increased cortical neural drive

• Increased motor unit coordination / synchronization

• Enhanced NMJ function

• Enhanced reflex potentiation

• Reduced antagonist co-contraction (net increase in agonist strength without any motor unit/NMJ adaptations)

Only ___% of muscle tissue is activated during maximal efforts in untrained populations

71

Size Principle vs Selected Recruitment

Size Principle: Order of motor unit recruitment, from low-threshold (small Type I) to high threshold (large Type II) fibers.

Selective Recruitment: The adaptation/ability of elite athletes to preferentially recruit Type II fibers over Type I fibers, allowing for quicker force production

As muscular hypertrophy occurs, motor unit recruitment (increases/decreases) for the same load

decreases

*This is why it’s important to engage in progressive overloading, or else lose ability to recruit motor units.

Smaller muscles rely more on _____, while larger muscles rely more on _____ (in context of neural adaptations)

firing rate; total recruitment

Cross-education

Where unilateral strength training of one muscle also increases strength/neural activity in the contralateral untrained muscle

*Evidence of Central neural adaptations as opposed to peripheral

Bilateral Deficit vs Bilateral Facilitation

Deficit: Untrained individuals show a lower force output bilaterally than the sum of their unilateral outputs

Facilitation: Trained individuals show a higher force output bilaterally than the sum of their unilateral outputs

Hypertrophy - Protein Pathways

• Akt

• mTOR

• myostatin inhibition

Mechanical Factors for Hypertrophy and Process Results

Factors

• Mechanical (for protein signaling): Heavy loads, eccentric loads, low-moderate volume

• Periodized with Metabolic (for hormones/substrates): moderate-high intensity, high volume

Results

• Optimal recruitment of muscle factors (as muscle fibers need to be recruited and used for growth)

• Growth factor expression

• Potential disruption to sarcomeres

^All of which increase muscle CSA (due to increases filament synthesis within myofibrils, and increased no. of myofibrils within the muscle fiber)

Fiber Size and Type Changes

Size: Selective hypertrophy of Type II fibers increases muscle CSA; Type I do not increase as much, suggesting potential for hypertrophy depends on genetic proportion of Type II to Type I fibers

Type: Type IIx changes to IIa early in exercise programs (more fatigue-resistant), but never Type I ←→ Type II.

Muscular Adaptations - Anaerobic Exercise

• Hypertrophy

• Fiber size/type

• Increased pennation angle

• Increased SR and T-tubule density

• Increased sodium-potassium ATPase activity

• Decreased mitochondrial/capillary density (but same or slightly higher total mitochondria/capillaries)

• Increased buffering capacity

• Increaed ATP, PCr, glycogen stores

Collagen Synthesis

1. Stimulus

2. Fibroblasts → Procollagen

3. Procollagen → Collagen filament/molecule

4. Collagen filament/molecules combine into microfibrils

5. Microfibrils → Fibrils → Fibers → Collagen bundle (largest organization)

Collagen Cross-linking

The true strength of collagen comes from the chemical cross-linking that occurs between collagen molecules throughout the collagen bundle.

Collagen Arrangement in different connective tissues

Longitudinally: Tendons, ligaments

Sheets w/ layers in multiple directions: Bone, cartilage, fascia

Collagen adaptations to exercise

• Increase in collagen fibril diameter

• Increase in no. of collagen fibrils and density

• Increase in covalent cross-linking between fibrils

Link between Joint Mobility and Chondrocyte Health

Hyaline Cartilage has no blood supply of its own and relies on active diffusion of oxygen and nutrients from the synovial fluid.

Therefore, regular loading of the joint (which pushes synovial fluid toward the cartilage under pressure) is important for cartilage health and remodeling. Joint immobilization leads to chondrocyte atrophy and even death.

Chronic Changes in Resting Hormonal Concentrations

Anaerobic exercise actually promotes very little/no increase in resting hormone concentrations → rather, that is more dependent on body composition and nutritional factors.

You wouldn’t really want a chronic increase in growth factors anyways, as it would lead to downregulation of those receptors.

AR up/downregulation postexercise

ARs appear downregulated within the 1st hour after exercise, and upregulated by the 48-72 hour period.

Ingesting a protein-carbohydrate supplement before and after the workout attenuates this AR downregulation.

Acute CV Response during Anaerobic Exercise

• Concentric: higher BP

• Eccentric: Higher SV, CO

*Muscular contractions >20% maximum result in a “clamping down” on local capillaries, creating a localized occlusion. However, blood flow increases during the subsequent rest period (reactive hyperemia). This muscular hypoxia is also actually a potent stimulus of muscle growth, partially due to lower pH.

Functional Overreaching/overreaching vs Nonfunctional overreaching/overtraining

FOR: Short-term decrements in performance w/ recovery achieved within a few days or weeks of rest; can be beneficial if implemented properly

NFOR: Long-term stagnation/decrease in performance that continues for several weeks or months, also leading to maladaptations of MSK and endocrine systems

Sympathetic vs Parasympathetic Overtraining Syndrome

Sympathetic OTS: Chronically increased sympathetic activity (fight or flight); more common with anaerobic training

Parasympathetic OTS: Chronically increased parasympathetic activity (depression of body systems); more common with aerobic-endurance training, but also exists as a progression to sympathetic OTS

Markers of Anaerobic Overtraining

• Unexplained underperformance/increased perception of effort

• Persistent fatigue, disordered sleep, loss of appetite

• Errors in training program design (sig. volume/intensity increase, training monotony, inadequate rest)

• Confounding factors: psychology, sociology, recent travel, etc.

• Exclusion criteria: other illnesses that may be causing the underperformance

Detraining Timeline and Mechanism

• Strength performance is maintained for up to four weeks of inactivity, but may decline more quickly in elite athletes

• Strength reductions appear related to neural mechanisms initially, and actual atrophy only becomes predominant later than that. The amount of muscle strength retained is rarely lower than pretraining values, indicating a small residual effect to resistance training.

• When an athlete returns to training, the rate of strength reattainment is high, supporting the paradigm of “muscle memory”

1 MET = _____ ml/kg/min VO2

3.5

VO2 =

Q * a-vO2 difference

Rate-pressure product

HR * Systolic BP

MAP equation

Diastolic + 1/3 the Syst/Diast difference

Ventilatory Equivalent equation

Minute Ventilation / Oxygen Consumption

Anatomical vs Physiological Dead space

Anatomical: Area in air cavities where gas exchange does not take place (i.e. everywhere except the alveoli)

Physiological: Alveoli that do not function properly due to any reason

Systemic Arterial PPO2 and PPCO2

PPO2: 100 mmHg

PPCO2: 40 mmHg

Chronic Adaptations to Aerobic Exercise

• Increased aerobic power

• Capillary/mitochondrial density

• Stored ATP, PCr, glycogen, triglycerides

• Ligament, tendon strength

• Decreased %BF

Myoglobin

Oxygen-transporting protein within muscle cells

Adaptations to Aerobic Endurance Training (Principles)

Maximal oxygen uptake increases for first 6-12 months, then further adaptations are linked to increased lactate threshold and improved running economy.

Aerobic training is, at the minimum, very important for exercise recovery.

At elevations greater than ___ feet, acute physiological adjustments begin to occur to compensate for the reduced PO2.

3,900

Study Question

After a bout of resistance training, acute hormonal secretions provide all of the following information to the body except

a. amount of physiological stress

b. metabolic demands of exercise

c. type of physiological stress

d. energy expended

D. Energy expended

Study Question

Which of the following hormones enhances muscle growth?

I. GH

II. Cortisol

III. IGF-1

IV. Progresterone

I and III only

Study Question

Which of the following is NOT a function of growth hormone?

Increased lipolysis, decreased collagen synthesis, increased amino acid transport, decreased glucose utilization

Decreased collagen synthesis

Study Question

Which of the following hormones has the greatest influence on neural changes?

GH, test, cortisol, IGF

Testosterone

Study Question

What type of resistance training workout promotes the highest GH increases in the acute period?

High volume/intensity, low rest intervals

Study Question

When one is performing a box-to-box plyometric drop jump, in order to generate sufficient force in a limited amount of time (<200 ms), which muscle fibers are bypassed through the principle of selective recruitment?

Type I

Study Question

Which of the following performance or physiological characteristics is NOT usually observed in a state of NFOR within athlete populations?

Performance stagnation/decrease, hormonal disturbances, mood disturbances/depression, increased fatigue

Mood disturbances/depression (late OTS, not NFOR; NFOR is mostly quantitative, objective changes)

Study Question

Following prolonged periods of detraining in elite athletes, which of the following physical characteristics will likely show the largest reduction as a consequence of the removal of an anaerobic training stimulus?

Total fat mass, fast-twitch CSA, slow-twitch CSA, total Type I muscle fiber content

Fast-twitch CSA

Study Question

Following a period of chronic high-intensity resistance training, a variety of physiological adaptations take place in a number of systems within the body that promote improved athletic performance in strength/power activities. If an elite athlete were to undergo 12 wks of heavy resistance strength training, which of the following adaptations would NOT be expected consequent to this type of anaerobic exercise?

Transition from Type IIx to Type IIa muscle fiber, increased pennation angle in certain muscle groups, reduced SR and T-Tubule density, elevated sodium-potassium ATPase activity

reduced SR/T-tubule density

Study Question

A 17-year old HS x-country runner has been training aerobically for six months in preparation for the upcoming season. Which of the following adaptations will occur in muscles during that time?

Increased conc. of glycolytic enzymes, hyperplasia of Type II fibers, transformation from Type I to II fibers, hypertrophy of Type I fibers

Hypertrophy of Type I fibers

Study Question

The amt. of blood ejected from the L ventricle during each beat is the _____

Stroke volume

Study Question

Which of the following does NOT normally increase during an aerobic exercise session?

EDV, cardiac contractility, cardiac output, DBP

DBP

Study Question

The MAP is defined as the _____

average BP throughout the cardiac cycle

Study Question

Primary training adaptations of elite aerobically trained athletes include which of the following?

I. Increased VO2max

II. Decreased blood lactate concentration

III. Increased running economy

IV. Decreased capillary density

I, II, and III only