stre&cond: chapter 5 - adaptations to anaerobic training

anaerobic training

high intensity, intermittent bouts of exercise

• weight/resistance training

• plyo

• speed/agility

• HIIT

energy systems:

• sprint and plyo (<10s) — creatine phosphate

• RT and HIIT (~20-30s) — fast glycolysis

neural adaptations

the nervous system is one of the EARLY sites of adaptation

• beginner weightlifters: see rapid increases in strength

  • bc NS better recruits fibers

• training continues — hypertrophy (changes in skeletal muscle)

  • strength precedes hypertrophy

• recruit more type II muscle fibers

central adaptations

brain → spinal cord → nerves → muscle

higher brain center: motor cortex activity increases with

• intent to produce max force/power — new exercises or movement

• increased task memory — improved coordination

spinal cord: signals travel down corticospinal tracts

• faster signal transmission

• greater maximal voluntary contraction (MVC)

  • untrained: can only activate 71% — need to improve this neural activation = greater force

motor unit adaptations

all work to increase force production

increased motor unit recruitment: recruits more muscle

• type II fibers

• larger motor neurons need higher recruitment threshold = more force but fatigue quicker

increased firing rate: motor units send signals more frequently

• more APs in shorter periods = summation of muscle contractions

increased motor unit synch: motor units fire together = increases rate of force development (RFD)

increased inter-muscle coordination: agonist/synergist muscle coordination = better efficiency

henneman size principle

says that motor units are recruited in ascending order of size

• small/low threshold → larger/high threshold

• as more force is required: small motor units → large type II motor units

• recruiting entire unit, NOT individual fibers

• ex: eccentric exercise — larger motor units needed to provide force

selective recruitment

ability to inhibit/bypass lower-threshold motor units and activate higher threshold motor units in their place

• NS can do this when rapid, powerful force is needed

• ex: barbell backsquat (typical recruitment pattern) vs vertical jump (need rapid recruitment of larger motor units)

• seen in experienced athletes — need more force more quickly

  • more efficient in this than size principle

NMJ adaptations

where the NS communicates with the muscular system

• brain → spinal cord → motor neuron → NMJ → muscle contracts

increased total area of NMJ = larger area for nerve and muscle to communicate

increased terminal branching: end of motor neuron has more branching

increased density of ACh receptors = better activates muscle for contraction

• increased speed of APs and motor unit firing = faster signals to activate muscle

stretch reflex

muscle spindle detects rapid stretch → signal extrafusal fibers to contract and produce force

• aka myotatic

• increased rate of force development (RFD) = increased explosive strength and power

• reflex shown to increase between 19-55% with RT

• ex: plyo, vertical jump

golgi tendon reflex

senses very high tension/force → inhibition of contracting muscle → muscle relaxes to protect against injury

• protective mechanism aka inverse myotatic

• decreased inhibitory sensitivity with RT — GTO tolerates the higher force before inhibition → can continue producing FORCE

• increases max strength

cross education

unilateral training causes effect in contralateral resting muscle

• central neural adaptation

• ex: training only your right leg while left is injured — untrained limb experiences 8-22% increase in strength

• maintain untrained limb neuromuscular pattern, reduce some atrophy and return toward normal function faster

  • training right leg: activates motor pathways, recruiting motor units, movement coordination

bilateral deficit

sum of force produced bilaterally is less than unilateral sum

• force with both limbs together < sum of each side separately

• ex: barbell with 120 lbs and lift for 1 rep < shoulder press with 60 lbs in each hand for 8 reps

• common in novice (beginner lifters) — should include more bilateral training

bilateral facilitation

sum of force produced bilaterally is more than unilateral sum

• NS more effective → better at activating and coordinating muscles when they work together

• force with both limbs together > sum of each side separately

• ex: barbell with 120 lbs and lift for 8 reps > shoulder press with 60 lbs in each hand for 1 rep

• common in experienced lifters

  • have increased voluntary agonist activation = NS better at activating main muscles needed

hypertrophy vs hyperplasia (h vs h)

hypertrophy: increase in muscle cross sectional area (CSA) from mechanical tension and exercise induced muscle damage RT

• increased contractile proteins in myofibril

• type II — high threshold, high output — hypertrophy the most

  • as force needed increases: type 1 (slight hypertrophy)→ type 2

• individual fibers become larger

hyperplasia: increase in number of muscle fibers

• inconclusive evidence — could affect a small amount of muscle tissue

fiber type transition

with training, muscle fibers shift from type II to intermediate type II (within type II fibers)

• type IIx: high anaerobic training + fatigues quick

• type IIa: still fast/type II + more fatigue resistant

  • maintain force for longer before fatiguing

  • detraining can cause type IIa → back to type IIx

• type I: highly oxidative/aerobic + most fatigue resistant

• type 2 to type 1 is inconclusive

muscular adaptations

increased in overall muscle circumference: hypertrophy of ind muscle fibers and myofibrillar volume

decreased capillary density: volume of muscle increases so it looks like less concentration of capillaries

decreased %BF: from increase volume in lean tissue

• aerobic enzymes unchanged or slight decrease (bc of RT)

• VO2max unchanged or slight increase (bc only training anaerobic)

• mitochondrial density unchanged or slight decrease (bc of RT)

• regulate acid-base balance — repeated exposure to H+ accumulation = increased buffering capacity

• increased CP/ATP storage for a larger supply due to repeated stress

increase in strength and power

• neural and muscular adaptations — motor uniit recruitent/firing/coordniation/synch, hypertrophy

• increased pennation angle

• SR/t-tubule — carrying APs

bone

endures mechanical loading from intense exercise such as bending, compression, and torsion

• connective tissue adaptation

• osteoblasts: stress on bone → migrate to bone surface → remodel outer surface → increase diameter and strength

• bone mineral density: mineral deposited in given area

  • increases with progressive loading and recovery — decreases with inactivity

  • wolff’s law: increase loading increases adaptation

• large muscle group and multi joint movement → stress long/structural bones → increase BMD

• minimal essentrial strain to stim osteoblasts

• with training: magnitude, rate, direction, volume, specificity

tendons, ligaments, fascia (TLF)

make connective tissue better handle and transmit force

• connective tissue adaptation

• increased collagen fibril diameter, number, and density

• increased stiffness of tendons: transfers force from muscle more effective = greater rate of force production

• with training: adaptation proportional to intensity, decreased vascularity = slow adaptation, rapid progression can cause damage

cartilage

maintains tissue viability, density, thickness, and strength

• connective tissue adaptation

with training:

• weight bearing forces through complete ROM — nutrients need to diffuse thru synovial fluid since lack blood supply

• moderate intensity for increase in thickness

bp rises

an acute hemodynamic response

systolic and diastolic bp rise bc of

• SNS activation: vasoconstriction of non-working muscle

• contracting muscles compress blood vessels and increase resistance → increase bp

• valsalva maneuver: breathing in and holding while engaging core → increases intrathoracic pressure

  • compresses aorta then decrease venous return to the heart → increase SNS

• bp rises and falls over RT

  • eccentric: bp decreases and drop is higher than the previous

  • concentric: bp rises due to muscle shortening → decrease venous return

cardiac output

an acute hemodynamic response

CO = HR x SV — deliver more oxygenated blood to working muscle

• eccentric phase: HR/SV increase

• concentric phase: decrease venous return → decrease EDV (vol of blood in ventricles)

  • muscles contract → compresses blood vessels → less blood returned

reactive hyperemia

surge in blood flow/venous return after completing a set

• an acute hemodynamic response

• muscle relaxes → decrease SNS → vasodilation → decrease resistance → increase venous return

• HR can still be high

• bp may decrease

chronic hemodynamic response

to training

at rest:

• decrease in resting bp by 2-4% — more prominent in those with elevated bp before training

• decrease in resting HR by 4-13%

of acute CV response:

• working same workload over time = smaller acute CV response (smaller increase in HR, BP, and CV demand)

• feels easier

LV size:

• LV wall thickens

  • due to concentric hypertrophy from pressure overload (when bp increases from RT)

  • with hypertension/high bp: non contractile tissue (fibrosis) buildup and does not benefit LV contraction = stressor

• little to no change in LV volume

pulmonary adaptations

acute: set completion → significant RR and TV increase

• breath more frequent and larger/deeper breaths

• replenish O2 stores that are lost during exercise

chronic:

• maximal exercise: increased RR and TV

• submaximal exercise/rest: decreased RR and increased TV — lungs more efficient, ore O2 when increasing TV so don’t need to increase rate

overreaching

excessive training short term that decreases performance

• functional: days to weeks — not always a bad thing and can “shock/peak” a system for adaptation

• nonfunctional: weeks to month

overtraining

excessive volume, or intensity of training for an extended period, that results in extreme fatigue, illness, or injury

• due to lack of sufficent rest, recovery, or nutrient intake

OTS

weeks to months of excessive training and/or inadequate recovery that can take years to recover

sympathetic: heightened SNS at rest

• occurs early — indicates overreaching too far

• increases resting HR, may increase bp, decreased HRV (less resilient to stress)

• acute (altered neuron), functional (altered motor unit recruitment), nonfunctional (decreased motor coordination)

• OVER-responsive system

parasympathetic: heightened PNS at rest

• occurs later

• legarthic (fatigue), decreased resting HR — HR doesn’t increase as much as expected during exericse

• UNDER-responsive

psychological alterations: can occur before decrements in performance — check in athlete’s mood and mental state

volume vs intensity

volume OT: too high of workload — sets, exercises, training sessions ; with insufficient recovery

• metabolic stressor

intensity OT: too high of neural demand — too heavy of a load, peaking too often, not enough recovery bt sessions

• neural stressor

can be combined

detraining

increment in performance/loss of adaptations

• added training stimulus goes away

• unplanned: ex — acute injury prevents training

• can occur from substantial reduction — not progressively overloading

  • decreased frequency, volume, intensity

principle of reversibility

temporary declines in adaptation

• power declines quickly — neural (less motor unit recruitment and rate = force declines)

• muscle CSA declines with no stimulus

  • quicker decrease in trained

  • greater decrease in type 2 bc of no RT stimulus

• fiber type initially maintained — transitions more oxidative to nonoxidative over longer period (IIa to Ilx)

• strength:

  • novice lifters initially maintained for 4-6 weeks

  • experienced lifters maintained for 2-3 weeks — greater decreases after (7-12% over 8-12 weeks)

    • bc accumulated more adaptations that need continuued training

retraining

adaptations typically return quickly upon resumption of training

• strength/power quickly return

• maintains neural adaptation

• muscle memory since body was trained before