Chpt 11: Fitness

Fitness - General

Ability to meet demands of a task

Fitness - Cardiorespiratory

Rate at with the circulatory & respiratory systems are able to:

• Use oxygen

• Provide energy to power muscle contractions

Ability of the working muscles to:

• Use oxygen

• Provide energy to power muscle contractions

Oxygen Consumption During Exercise

• Transfer O₂ from lungs to capillaries

• The heart pumps thru arteries (bound to Hb)

• Oxygen helps liberate energy for muscles to work

VO2 Max

• Maximal volume of oxygen that can be intaken (plateau on curve)

• Maximal aerobic capacity

• Maximum # of oxygen a person can use during intense exercise

• Incremental exercise until exhaustion

• Expressed relative to body weight

VO2max Mask

Measues volumes of gas inhaled/exhaled

Defining fitness - Curve

• Amount consumed per min per unit of body weight

• Work rate > as energy demand >

• Increase E demand → > O2 demand

• Plateau = no further O2 intake (VO2 max); relative to body weight

Determinants of VO2max

• O2 carrying capacity of blood

• Ability of heart to pump

VO2 max across levels of fitness

• Better fitness = higher VO2max

• Substantial genetic component

• Influences baseline

• Influences trainability (ability to see improvements w/ frequent workouts)

Consequences of increased fitness levels

• Smaller effort (less energy output)

• Greater CNV amplitude (> task preperation)

• Smaller N2 amplitude on NO-GO trial (typ >); reflects inhibition/executive control

• No behavioural differences (just less work for the brain)

Difficulties standardizing exercise (equating VO2Max)

• Requires expensive equipment

• Need to exercise to maximum (inappropriate for some pops)

• Variable (prolonged exercise duration, heat conditions, intensity)

VO2 Reserve

• Differences btwn VO2 rest & VO2 max

• Reflects energy expenditure

• VO2 rest can be difficult to measure

Standard VO2

Similar to using a standard output rate

Ways to best equate exercise output

• Target heart rate

• Maximum Lactate Steady State

• Ventilatory Threshold

• Catecholamine Threshold (Tcat)

• Critical Power

• Rating of Perceived Exertion

Equating exercise output - Target Heart Rate

• 220 - age

• Linear relationship btwn HR & VO2 max

• Complete overlap btwn genders, races, & age

Target Heart Rate - Influences

• Hydration

• Temperature

• Substances (caffeine, medications)

• Mental stress

Target Heart Rate - Heart Rate reserve

• HRmax - HR rest

• HRrest + % of reserve = target heart rate

• Might better reflect energy expenditure

Equating exercise output - Maximal Lactate Steady State

• The highest blood lactate concentration & work load that can be maintained/time w/o a continual blood lactate accumulation

Equating exercise output - Ventilatory Threshold

• Changing lactic acid into lactate generates carbon dioxide (or pyruvate → lactate)

• Parallels the production of lactate

Equating exercise output - Catecholamine Thresholds (Tcat)

• Levels > in exponential manner w/ > exercise intensity

• May actually determine both lactate & ventilation thresholds

Equating exercise output - Critical Power

• Maximum # of work you can due without fatigue

• Time-consuming to establish

• Aerobic: hours

• Anaerobic lactate: 60-90 secs

• Alactic: 10-12 sec

Equating exercise output - Rating of Perceived Exertion

• Train participants to use a scale

• Represents integration of information across

  • Peripheral working muscles/joints

  • Cardiovascular system

  • Respiratory system

  • CNS (anxiety, etc)

• Requires: multiple visits, training w/ levels of exercise

Acute Effects of Exercise - Catecholamines (Review)

• Transient > in catecholamines w/ exercise

• CNS Animals: > precursors, > CAT

• Periphery Humans: indirect evidence in indies w/ > enzymes

Catecholamines - Fitness

• 10 weeks training (pre/popst VO2 & CAT testing)

• Greater NE rxn to exercise (at same relative intensity)

• The more you exercise, the better your brain rxn to the exercise is

HPA Axis Hormones (Acute) - Fitness

Review of Acute Effects:

• Need > 80% VO2max to > plasma/salivary ACTH & cortisol

• Need to exercise for > 45 min if intensity is < VO2 max

With fitness:

• This does x chg w/ fitness

• If fit, need to exercise harder to reach this lvl of stress rxn engagement (< perceived stress)

HPA Axis Hormones (Chronic) - Fitness

Review of Chronic Effects:

• Regular exercise x chg baseline ACTH/cortisol lvls in humans

• Animal studies: voluntary x; forced exercise impacts CORT lvls (stress effect)

With fitness:

• Stress rxn remains the same (good thing: x want to lose, just x want worse)

• Same cortisol lvls/HPA rxn but diff feedback mechanism

• Evidence from athletes (fit occupations)

HPA Axis Hormones - Fitness Mechanism

• Slightly higher ACTH

• No diff in cortisol

• < sensitivity to feedback (cortisol binding)

  • < Glucocorticoid R (DA in HC; impact memory/recall - synaptogenesis)

  • < expression of GR mRNA in highly trained athletes

BDNF (Chronic) - Fitness

Exercise Review:

• Humans: x changes in serum concentation (periphery)

• Rodents: > BDNF, > BDNF mRNA expression

• chgs BDNF rxn to exercise (blunts)

With fitness (reg exercise):

• Stronger rxn to exercise

• Sig chg in basal BDNF lvls (> basal lvl)

• stabilized effect (more constant large difference)

• Though mixed findings

Exercise & Cognition - Performance (fitness)

• < basal BDNF (>stress), > response to exercise (sig > BDNF)

• Better memory score at rest

• Faster rxn time (similar accuracy)

• Better performance on WCST

• Better Spatial memory

• < BDNF in athletes → > performance (likely due to timing of BDNF)

Exercise & Cognition - Morphology Chgs

• Dorsolateral PFC

• Hippocampus

• Basal Ganglia

• White fibres (myelination): corticospinal tracts, corpus callosum

Morphology Chgs - Dorsolateral PFC

• Exercise = more grey matter volume

• Function: executive func, planning, rxn selection, working memory

• Helps explain > memory scores, & sorting task

Morphology Chgs - HC

• Exercise = > volume

• Function: memory formation, spatial memory

• Helps explain improved memory scores

Morphology Chgs - Basal Ganglia

• Exercise = > volume

• Function: sensorimotor learning, motor control (initiation/stabilization)

• Helps explain faster rxn time

Morphology Chgs - White fibres

• Higher streamline count in athletes

• Corticospinal tract: controls voluntary movement (faster rxn time)

• Corpus callosum: comm btwn lobes - frontal (> executive func)

Morphology Chgs - Gray/White Matter

• Gray matter = cell bodies (> gray, > cell bodies)

• White = myelination on axon (> white, > myelinated)

• Athletic training = > grey/white matter

• Due to > lvls of BDNF → stimulates growth

Fitness - Implications in CNS changes but not periphery

• Brain & spinal cord = sep from body by BBB

• BDNF is taken from periphery

• Catecholamines x cross BBB (affects measurement)

• Peripheral catecholamines can only influence vagus nerve (supplement HPA rxn)

Whos smarter - athletes vs non-athletes

• Highly variable & too large of a genralization to make that athletes are smarter

• For a given indie, regular exercise > cognitive function