Week 4: Physiology of high-intensity intermittent exercise Flashcards
Team sport performance consists of what three elements?
What are these areas made up of?
Physical performance
- Match running performance eg total distance, higher speed running, sprinting, COD
Technical performance
- Sport specific activities: individual skills & execution, involvements and efficiency/effectiveness
Tactical performance
- Positioning, decision-making, strategy, intra-and inter-team dynamics
Combining physiological, sport specific skills (technical & tactical) with what other element affects performance?
Context (environmental & opposition)
What percentage of a football game is spent at moderate/high intensity?
10%
In AFL there is….
* High frequency of ….. ….. …. throughout the match interspersed by lower bouts of activity
* The number of sprint efforts above ….. decrease as the match …..
* Despite this heart rate remains high (around ….. - …..bpm = ….-…..% HRM = large aerobic demand!)
- As a proportion of total playing time over ….% of the time is spent below ….km/hr (just above walking speed)
- ….% of time is spent at moderate and high speed.
- When you look at that by distance covered, around ….% is at these walking speeds
- …..% of total distance covered was during high speed and sprint actions
High speed activities
23km/hr, progresses
170-180, 85-90%
75%, 7km/hr
10%
40%
15%
Across several studies investigating football intensity the overall findings suggest?
Vast majority of playing time spent at very low intensities
Brief but frequent phases of high speed activity
Intensity profiles for different competition levels and playing positions across several sports
- The most intense sport measured (average metres travelled per minute of playing time) was the …..
- The intensity in finals football is about ….% higher than in the regular season
While high speed running isn’t necessarily a key determinant of success it certainly paints a picture of more ….. teams (such as those making the finals - having very fit athletes who can tolerate higher demands)
Lower intensity profiles = …., …. and ….. (brief & infrequent periods of high speed running)
- AFL
- 13%
- Competitive
- Soccer, rugby, cricket
Football comparison: soccer vs Australian Rules
- Overall match duration = ……% longer in AFL than soccer
- Intensity (m/min) is lower in soccer (…m vs …m AFL)
- High speed sprint actions are atleast …..% greater in AFL
- Despite this greater number of high intensity actions …. …. is almost identical
- 30% longer (90-100 vs 125-130 mins)
- 116m vs 129m
- 50%
- Average HR - Could be related to differences in recovery periods between efforts? Or are AFL players fitter?
Types of fatigue
- Physical
- Physiological
- Motor task-induced fatigue
- Mental or cognitive task induced fatigue
What drives physical/physiological/motor task induced fatigue?
Reductions in neural activation &/or contractile function
What drives cognitive task fatigue?
Psychobiological state characterised by an increased perception of tiredness or effort, a lack of energy or motivation, and may be induced by prolonged periods of demanding cognitive activity
Effect of physical and mental fatigue?
Performance decrement
Effect of high intensity activity?
There is acute fatigue immediately after high intensity activity periods.
This results in a significant reduction in work performed not just after that peak intensity period but also compared to the average work rate across the match
Soccer study on match intensity
What happens to intensity of the course of the match?
The greatest proportion of intensity occurs in what portion of the match?
What might these findings be indicative of?
- General reductions in intensity over the course of the match
- Greatest proportion of players are completing their most intense and least intense periods occur in the first & last 15 minutes of the match respectively (demonstrates a clear change in intensity across a match)
- These findings might be reflective of tactical variations across the match and different fatigue mechanisms contributing to an overall performance decrement
Key message from all studies discussed….
- INTENSE EXERCISE CAUSES FATIGUE!
- Fatigue increases as prolonged high-intensity intermittent exercise progresses
Repeat sprint performance
- Another way to assess fatigue is through ….
- …… in repeated sprint performance ….. a match compared to ….. the game and during …. …..
- However when you test repeated sprint performance immediately after intense periods in the match there is an even …… ….. decrease in repeated sprint performance in the …. and then …. half
Fairly typical responses of decreasing ….. and activity profiles as the game progresses
Clearly shows that not only are there clear performance consequences of fatigue …. the match but periods of …. intense exercise can lead to additional fatigue that then has implications for tactical and technical components of performance
- Repeat sprint performance
- Decrement, after, before, half-time
- Even greater, first, second
- Performance
- Across, highly
Recovery from performance
This study measured soccer players physical and physiologically responses immediately after a match as well as their recovery every 24hrs after that match
- Peak and sustained knee extension force was about ….% lower immediately after the match and then that returns somewhat back to normal over the following couple of days (although >3 days it hasn’t reached the baseline level of force production)
- Muscle soreness is greatest immediately ….. a match, reducing somewhat …. after the match and then continues to ….. over the following couple of days (>3 days still not at baseline)
- ….. …… is an indicator of muscle damage with that enzyme detected in the blood after …. damage to muscle tissues – you can see there is quite a large or significant increase (it …..) following the match compared to the control. It continues to rise …. after the match before decreasing and returning back to normal levels after 3 days of recovery
- ….. is another indicator of muscle damage (protein detected in blood after microtears within the muscle). There is a massive increase (…..% of the baseline) immediately after the match – tends to return to baseline really quickly.
- Overall we can see that muscle damage and perceptions of soreness all contribute to reductions in physical capacity and that the time course for recovery to baseline levels can be over ….
- 10%
- After, 24hrs, reduce
- Creatine kinase, larger, doubles, 24hrs
- Myoglobin, 665%
- 3 days
Recovery from performance
- ….. ….. in maximal voluntary contraction (MVC) impaired immediately after soccer match, returning to baseline 48 hrs later
- ….. activation of muscles also impaired, indicating central fatigue or impairment
Fatigue is ….. and ….. mediated!
Important to consider time course of recovery in planning subsequent ….. sessions with high …. demand
- Knee extension
- Voluntary
- Centrally & peripherally
- High-intensity, CNS
What are the common sources of fatigue
Acute muscle pH reduction
- Inhibits PFK
- Actin-myosin coupling
Neural activity reduction
- Ion disturbances
- K+ accumulation around muscle fibre
Glycogen depletion
Dehydration & hyperthermia
Mental stress
What energy systems are required for prolonged high intensity intermittent exercise?
They are reliant on all energy systems contributing to performance as it consists of both periods of very high intensity work and very low intensity recovery phases
How can we assess aerobic demands of sport?
Lab based V02 testing - high ecological validity but not always practical
Field based portable V02 testing
Heart rate – V02 relationship (can provide a good approximate measure to estimate aerobic demands)
Mean HR for most team sports?
Mean HR for most team sports ~75-85% HR max
- At Moderate-high & very high intensities the shape of the ….. response tracks very closely with measure …. consumption and clearly this can be useful and an accurate way to measure aerobic demands of sport when measuring V02 isn’t possible
- This wouldn’t be appropriate when activities are ….. in nature or ….. V02 max such as sprinting
- In this instance HR cannot be used as a proxy for metabolism because HR ….. at ….. 02 consumption
- HR, 02
- Anaerobic, above
- Plateaus, maximal
Heart rate in AFL?
Over an hour is accumulated at intensities above 90% of HR max with almost all of there playing time spent above 75% HR max
Heart rate in AFL
High aerobic demand and an impressive fitness level by an athlete who is able to spend so much of their time near their …… ……. and within ……% of their V02 max
Anaerobic threshold
10%
Heart rate in rugby league
Does it fluctuate with intensity?
Average HR response - first half vs second half
Fluctuations in intensity with different phases of play
Average HR is not dissimilar between first and second halves but given players have likely lost fluid through sweat, resulting in plasma volume reductions and therefore increase in CV load at the same intensities – even though their internal load (HR) appears to be the same they are likely working at a lower intensity overall – reduction in external load
Limitations
Estimations based on HR
* Influence of …. & …..
* Greater variability in relationship between …. & …. during ….. compared to …./steady state exercise
Direct measures using portable gas analysers
* Influence on specific ….. activities (match)
* ……. & logistics
* Accuracy & error
- Dehydration, psychological factors
- HR & V02, high-intensity intermittent exercise, continuous
- Soccer
- Practicality
Assessing anaerobic demands: Glycolytic energy provision
- Finger lactate samples taken before and throughout a rugby league match demonstrate the high anaerobic demand for athletes reaching on average ….. of blood lactate with some reaching much higher in the first half
- We do see a ….. off towards then end of the match - some would assume that lactate should be highest at the end due to fatigue. Don’t confuse the two!
- Lactate simply indicates a …. ….. …. ….. and carbohydrate use in the ….. of oxygen
- Intensity in matches ….. over the duration of the match so a reduction in lactate is not unexpected as overall intensity and match speed has likely decreased and therefore we have greater ….. energy provision
- There are other issues with using blood lactate to assess the level of anaerobic demand because it differs from what is actually happening in the muscle. To increase accuracy you would measure ….. …. instead of blood lactate – but that’s a lot more invasive (requires muscle tissue samples – not always feasible!)
- 8mmol/L
- Taper
- Greater rate of glycolysis, absence
- Reduces, aerobic
- Muscle lactate
Blood lactate sampling
Importance of….
* …. of sampling
* …. of sampling
* Effect of ….. ….
Only an estimation of whats really happening
* …… in muscle
* …… in blood
* …… from blood
- Timing
- Frequency
- Activity Type
- Production
- Appearance
- Removal
…… cycle exercise has the ….. correlation between ….. lactate and ….. lactate whereas the yo-yo intermittent recovery test has a weaker relationship/is a lot more variable when comparing muscle/blood lactate. Even worse when looking at soccer matches.
Continuous, highest, blood, muscle
The role of high-energy phosphates: estimating demands
- …… …… analysis
– …… of sprints and accelerations - Biopsies during simulations or game
- Number of sprints completed in a game
NOTE: The ability to ….. ….. is reduced during a match and during tournaments
- Time motion
- Number
- Repeat springs
The role of high energy phosphates: Resynthesis rates
- …… is almost completely resynthesised within 3 minutes, with …..% restored within ….. …..
- If performing repeat sprints you could wait ….. ….. to minimise performance losses from high energy phosphate availability. However in most sports, waiting is not always an option!
- Individuals with …. ….. energy system will ….. PCr faster
- PCr, 50%, 30 seconds
- 3 minutes
- Greater, aerobic
- Synthesise
Fatigue & high-intensity exercise
Oxidative metabolism
* Aerobic production of ….. (potentially for repeated sprints)
…… accumulation
* ….. accumulation
* Decrease …… properties of muscle
Decrease in neural drive
* Decrease in ….. activity during repeated bouts
* May be a protective mechanism?
Muscle stiffness
* Change in ….. behaviour (<stiffness) ie more efficient ….. energy contribution = enhances ….. production
ATP
Metabolite
Hydrogen
Contractile
EMG
Mechanical
Elastic
Enhances
Aerobic & anaerobic capacity
- Assessing aerobic and anaerobic capacity of athletes together indicates how much ….. they can provide from each source
- The diagram below shows two athletes with the same velocity at their V02max represented by the top of the green bar
- But you can see they have two very different maximal sprint speeds
- One being 29km/hr and the other being 33km/hr
- The differences between …… …… …… and the velocity at ….. is what is known as the ….. ….. …..
- This can tell us how much those athletes can provide from …… sources
- But it is also reflective of neuromuscular differences
- Energy
- Maximal sprint speed and V02max, anaerobic speed reserve
- anaerobic
- Neuromuscular
Assessing aerobic & anaerobic capacity: Training effects
- Training to improve aerobic energy provision there is an increase in the ….. at V02max and that can shift upwards the ….. …… speed slightly because we have increased to some degree the ….. …… …… as well
- However maximal sprint speed is typically limited by neuromuscular factors more so than ….. …… itself
- If they instead train to increase anaerobic energy provision you might see again an increase in the ….. ….. ….. and a small increase in the velocity at v02max and that can lead to an increase in the anaerobic speed reserve
- This can be beneficial in team sports by making it that high intensity efforts and high speed running aren’t as stressful as they were for an athlete compared to before they conducted this training and adapted to that anaerobic stress
- Velocity
- Maximal sprinting
- Anaerobic energy provision
- Energy provision
- Maximal sprint speed,
Summary of physiology of high intensity intermittent exercise
- Predominantly ……. derived supply of energy during team sports
- ……. …… and high energy phosphates supply energy during intense bouts
- Not only ….. bouts but repeated bouts of intense activity essential in team sport
- Training programs can be tailored to focus on ….. limitations
Aerobically
Anaerobic Glycolysis
Intense
Physiological
Fuelling for team sport/high-intensity intermittent exercise
Substrate relative contribution
Fat
* Approximately …..% of total energy provision
* Estimated to be ~…./hr for 70kg athlete with V02max of 60ml/kg/min
Carbohydrate
* Approximately …..% of total energy provision
* Estimated to be ~…../hr for 70kg athlete with V02max of 60ml/kg/min
Protein
* Very little contribution – less than …..%
*Data based on RER during lab-based stimulations
40%
56g
60ml
60%
~205g
10%
Fuel supply
Substrate metabolism
*….. ….. …. form from the breakdown of lipids or triethylene glycerol from adipose tissue and …… stores and that occurs from the enzyme lipoprotein lipase breaking down those lipids
* From that the glycerol backbone can be used in …. while free fatty acids enter the …..-……. process for conversion to acetyl-coA and enter the kreb cycle
* …… is available from the liver, blood and also intramuscular stores where it can then enter the mitochondria or go through glycolysis for the production of ATP
* We know that from endurance and resistance training that ….. ….. increase with training and that makes the substrate more available for use in the muscle and by the ….. for metabolism
Free fatty acids
Intramuscular
Glycolysis
Beta-oxidation
Glycogen
Intramuscular stores
Mitochondria
Free fatty acids
* Blood FFA ….. through match
* Big increase at ….. of match – greater …. periods, …. intensity exercise
* Only a small increase in ….., a gluconeogenic precursor in liver
* When we have increased FFA usage, we have …. …. …. use, so is glycogen sparing!
Increases
End
Rest, lower
Glycerol
lower blood glucose
Carbohydrates
* Here we have the lactate plasma-free fatty acid and ammonia responses during a soccer match
* You can see on the left that lactate is higher in the ….. half and ….. over the rest of the match
* You can see in the middle plasma free fatty acid has the ….. relationship to lactate and then of course ……
* Increasing the amount of ….. …… that occurs to supply our exercise during soccer matches and that again supports our knowledge of the reduced intensity of the match and that ….. …… effect
* On the right hand side the ammonia (by product …… or ….. …. breakdown) responses and we can see that it …… during high intensity intermittent exercise and remains relatively steady throughout
* It contributes ….. in terms of the fuel supply to perform exercise
First, decreases
Inverse, glycolysis
Fat oxidation
Glycogen sparing
Protein
Amino acid
Increases
Little
Metabolic responses
* Muscle lactate ….. across the match which is represented by that decrease in glycolysis as intensity reduces and more oxidative metabolism occurring to fuel our exercise
* pH decreasing = acidosis. Increases in the first half where intensity is higher the more glycolysis the more lactate and ….. accumulation which leads to this …..
* Whereas in the second half with …. intensity pH returns closer to normal or neutral around that 7.1 mark
* Over the course of the match we also see muscle ….. depleting reflecting its use throughout the match to fuel high-intensity exercise
* Now as glycogen becomes depleted we need to …… our intensity to ….. exercise and also retain some of that glycogen for any high intensity bouts that we may experience later in the match
Decreases
Hydrogen, acidosis
Lower
Glycogen
Reduce, maintain
How did was exercise/glycogen stores affected in a study which compared the effects of starting with high/low glycogen?
Those who started with a moderate to high baseline glycogen availability were able to complete the match and they finished with some glycogen remaining
The person with low starting glycogen (in the red) depleted their glycogen stores rapidly and couldn’t sustain exercise to perform in the second half so it’s very obvious that carbohydrates & glycogen matters to high performance athletes and high intensity exercise
Maintaining a proper diet that provides all of the substrates and macronutrients required to perform at a higher level and for the duration of the match
Glycogen depletion: Fibre-type specific responses
- Moderate intensity exercise primarily involves oxidative metabolism and ….. ….. …. involvement
- So most ….. is depleted from these fibres
- Intermittent intense exercise involves a …. of fiber type involvement and so fairly even depletion between fibre types
- Extended …. exercise involves more …. twitch fibres for power production and therefore more depletion occurs
- Glycogen depletion is fiber type ….. and depends on exercise intensity but all fibres are impacted by that exercise
Slow twitch fibre
Glycogen
Mix
Intense, fast
Specific
Fuelling for recovery: carbohydrates
- Muscle glycogen can deplete >…..% after soccer matches
- Muscle glycogen can take ….. days to recover after match play
- …… rich diets can improve repletion and recovery rates
- Those who fuelled with ….. ….. recovered faster = can return to perform sooner
> 50%
Several
Carbohydrate
Additional carbohydrates
Hormonal responses
* …… (adrenaline & noradrenaline) increase during game, increasing ….. release from adipose tissue and stimulating glycolysis
* ….. …. increases, stimulating lipolysis
* Cortisol increases, stimulating liver ….. from amino acids
Catecholamines
FFA
Growth Hormone, lipolysis
Cortisol
gluconeogenesis
Hydration
- …..% fluid loss (by body weight change) can result in decreased performance
- Depending on context, team sport athletes often lose ….. - …..kg during matches
- …… increases physiological strain and can result in reduced mental, physical, tactical and technical performance
- Players need to start each game …… and try to minimise fluid losses through fluid consumption to limit dehydration throughout the game (without over-drinking)
2%
2-5kg
Hypohydration
Euhydrated
Dehydration & the effect on performance
- The magnitude of decrement in exercise capacity and aerobic power is …
- With a ….% bodyweight loss there is ….-…..% reduction in exercise capacity
High
2%,
10-20%
Contributing factors to dehydration
- …… – ie hot & humid environment increases sweat loss
- High …… demand
- Baseline hydration status
- Hypohydration >…..% body mass lost
- When all these ….. components occur it is very likely you will see performance losses
Environmental
Aerobic
2%
3
Fluid balance
* Typical intake is …..L during a match
* On a mild day ….L of fluid loss – when environmental factors are added eg hot/humid weather = additional …..L of fluid loss
* Fluid loss often exceeds intake resulting in a negative fluid balance and therefore dehydration
1.5L
3L
1.5L
…… Rate often exceeds rate of replacement (fluid intake), resulting in a negative fluid balance (…..)
Sweat
Dehydration
During matches
* Present fluids to players as ….. as possible to increase fluid intake opportunities
* Maintaining fluid balance not always practical - large volumes of fluid can increase ….
* Players should drink .. …../to thirst most of match and use quarter/half time breaks to replenish fluids and ….
* CHO intake can decrease …. …… which may increase discomfort (bolus) and reduce water absorption in gut
Often
Discomfort
Ad libitum
CHO
Gastric emptying
