Week 4: Physiology of high-intensity intermittent exercise

Question 1

Team sport performance consists of what three elements?

What are these areas made up of?

Answer 1

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

Question 2

Combining physiological, sport specific skills (technical & tactical) with what other element affects performance?

Answer 2

Context (environmental & opposition)

Question 3

What percentage of a football game is spent at moderate/high intensity?

Answer 3

10%

Question 4

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

Answer 4

High speed activities
23km/hr, progresses
170-180, 85-90%
75%, 7km/hr
10%
40%
15%

Question 5

Across several studies investigating football intensity the overall findings suggest?

Answer 5

Vast majority of playing time spent at very low intensities

Brief but frequent phases of high speed activity

Question 6

Intensity profiles for different competition levels and playing positions across several sports

1. The most intense sport measured (average metres travelled per minute of playing time) was the …..
2. 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)

Answer 6

1. AFL
2. 13%
3. Competitive
4. Soccer, rugby, cricket

Question 7

Football comparison: soccer vs Australian Rules

1. Overall match duration = ……% longer in AFL than soccer
2. Intensity (m/min) is lower in soccer (…m vs …m AFL)
3. High speed sprint actions are atleast …..% greater in AFL
4. Despite this greater number of high intensity actions …. …. is almost identical

Answer 7

1. 30% longer (90-100 vs 125-130 mins)
2. 116m vs 129m
3. 50%
4. Average HR - Could be related to differences in recovery periods between efforts? Or are AFL players fitter?

Question 8

Types of fatigue

Answer 8

1. Physical
2. Physiological
3. Motor task-induced fatigue
4. Mental or cognitive task induced fatigue

Question 9

What drives physical/physiological/motor task induced fatigue?

Answer 9

Reductions in neural activation &/or contractile function

Question 10

What drives cognitive task fatigue?

Answer 10

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

Question 11

Effect of physical and mental fatigue?

Answer 11

Performance decrement

Question 12

Effect of high intensity activity?

Answer 12

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

Question 13

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?

Answer 13

• 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

Question 14

Key message from all studies discussed….

Answer 14

1. INTENSE EXERCISE CAUSES FATIGUE!
2. Fatigue increases as prolonged high-intensity intermittent exercise progresses

Question 15

Repeat sprint performance

1. Another way to assess fatigue is through ….
2. …… in repeated sprint performance ….. a match compared to ….. the game and during …. …..
3. 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

Answer 15

1. Repeat sprint performance
2. Decrement, after, before, half-time
3. Even greater, first, second
4. Performance
5. Across, highly

Question 16

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

1. 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)
2. 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)
3. ….. …… 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
4. ….. 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.
5. 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 ….

Answer 16

1. 10%
2. After, 24hrs, reduce
3. Creatine kinase, larger, doubles, 24hrs
4. Myoglobin, 665%
5. 3 days

Question 17

Recovery from performance

1. ….. ….. in maximal voluntary contraction (MVC) impaired immediately after soccer match, returning to baseline 48 hrs later
2. ….. 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

Answer 17

1. Knee extension
2. Voluntary
3. Centrally & peripherally
4. High-intensity, CNS

Question 18

What are the common sources of fatigue

Answer 18

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

Question 19

What energy systems are required for prolonged high intensity intermittent exercise?

Answer 19

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

Question 20

How can we assess aerobic demands of sport?

Answer 20

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)

Question 21

Mean HR for most team sports?

Answer 21

Mean HR for most team sports ~75-85% HR max

Question 22

1. 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
2. This wouldn’t be appropriate when activities are ….. in nature or ….. V02 max such as sprinting
3. In this instance HR cannot be used as a proxy for metabolism because HR ….. at ….. 02 consumption

Answer 22

1. HR, 02
2. Anaerobic, above
3. Plateaus, maximal

Question 23

Heart rate in AFL?

Answer 23

Over an hour is accumulated at intensities above 90% of HR max with almost all of there playing time spent above 75% HR max

Question 24

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

Answer 24

Anaerobic threshold
10%

Question 25

Heart rate in rugby league

Does it fluctuate with intensity?

Average HR response - first half vs second half

Answer 25

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

Question 26

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

Answer 26

1. Dehydration, psychological factors
2. HR & V02, high-intensity intermittent exercise, continuous
3. Soccer
4. Practicality

Question 27

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!)

Answer 27

1. 8mmol/L
2. Taper
3. Greater rate of glycolysis, absence
4. Reduces, aerobic
5. Muscle lactate

Question 28

Blood lactate sampling

Importance of….
* …. of sampling
* …. of sampling
* Effect of ….. ….

Only an estimation of whats really happening
* …… in muscle
* …… in blood
* …… from blood

Answer 28

1. Timing
2. Frequency
3. Activity Type
4. Production
5. Appearance
6. Removal

Question 29

…… 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.

Answer 29

Continuous, highest, blood, muscle

Question 30

The role of high-energy phosphates: estimating demands

1. …… …… analysis
   – …… of sprints and accelerations
2. Biopsies during simulations or game
3. Number of sprints completed in a game

NOTE: The ability to ….. ….. is reduced during a match and during tournaments

Answer 30

1. Time motion
2. Number
3. Repeat springs

Question 31

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

Answer 31

1. PCr, 50%, 30 seconds
2. 3 minutes
3. Greater, aerobic
4. Synthesise

Question 32

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

Answer 32

ATP
Metabolite
Hydrogen
Contractile
EMG
Mechanical
Elastic
Enhances

Question 33

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

Answer 33

1. Energy
2. Maximal sprint speed and V02max, anaerobic speed reserve
3. anaerobic
4. Neuromuscular

Question 34

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

Answer 34

1. Velocity
2. Maximal sprinting
3. Anaerobic energy provision
4. Energy provision
5. Maximal sprint speed,

Question 35

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

Answer 35

Aerobically
Anaerobic Glycolysis
Intense
Physiological

Question 36

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

Answer 36

40%
56g
60ml
60%
~205g
10%

Question 37

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

Answer 37

Free fatty acids
Intramuscular
Glycolysis
Beta-oxidation
Glycogen
Intramuscular stores
Mitochondria

Question 38

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!

Answer 38

Increases
End
Rest, lower
Glycerol
lower blood glucose

Question 39

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

Answer 39

First, decreases
Inverse, glycolysis
Fat oxidation
Glycogen sparing
Protein
Amino acid
Increases
Little

Question 40

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

Answer 40

Decreases
Hydrogen, acidosis
Lower
Glycogen
Reduce, maintain

Question 41

How did was exercise/glycogen stores affected in a study which compared the effects of starting with high/low glycogen?

Answer 41

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

Question 42

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

Answer 42

Slow twitch fibre
Glycogen
Mix
Intense, fast
Specific

Question 43

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

Answer 43

> 50%
Several
Carbohydrate
Additional carbohydrates

Question 44

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

Answer 44

Catecholamines
FFA
Growth Hormone, lipolysis
Cortisol
gluconeogenesis

Question 45

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)

Answer 45

2%
2-5kg
Hypohydration
Euhydrated

Question 46

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

Answer 46

High
2%,
10-20%

Question 47

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

Answer 47

Environmental
Aerobic
2%
3

Question 48

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

Answer 48

1.5L
3L
1.5L

Question 49

…… Rate often exceeds rate of replacement (fluid intake), resulting in a negative fluid balance (…..)

Answer 49

Sweat
Dehydration

Question 50

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

Answer 50

Often
Discomfort
Ad libitum
CHO
Gastric emptying