Week 5: Physiology of high intensity exercise Flashcards
Definition of high-intensity exercise?
Exercise intensity eliciting more than 90% V02max
Other definitions:
* All-out effort (eg sprinting)
* Exercise at an intensity eliciting 100% V02max
* Performing the highest possible amount of work in a given time
* Maximal isometric contraction
Where is energy-supplied for high intensity exercise?
Anaerobic
* ATP/Phosphocreatine
* Glycogen –> Lactate
Aerobic
* Carbohydrates, fats, amino acids
The longer the HIE bout the greater the relative contribution from ….. energy supply
Aerobic
ATP Demand in high-intensity exercise?
- Sprint performance requires an incredibly high rate of ATP supply
- For elite sprinters to achieve & maintain the sprint velocities required to be competitive, they need >4,4mmol/kg/dm of ATP
- For Usain Bolt to run this fast (and be ahead by so much) shows how highly developed his anaerobic energy system is
- But, need to consider other factors contributing to sprint performance!
For elite sprinters to achieve & maintain the sprint velocities required to be competitive, they need >……mmol/kg/dm of ATP
4.4mmol/kg/dm
ATP supply - usage rate
- Running: ~75% V02max
- Sprinting: ~200% V02max
- Maximal Isometric contraction
- Running: 1.5mmol/kg/dm
- Sprinting: 4.0mmol/kg/dm
- Isometric contraction: 12.0mmol/kg/dm
ATP Supply - sources
(Concentration, max ATP resynthesis rate, time to depletion)
- ATP Pool
- PCr Pool
- Glycogen (Lactate)
- Glycogen (CO2 + H2O)
- Fat (Adipsoe tissue)
- 24, 0, 2s
- 80, 9, 8
- 300, 4.5, 360 (6 min)
- 300, 2.0, 6000 (100 min)
- Adipose tissue, 1.0, >172,800
What is anaerobic glycolysis
Breakdown of glucose (2 ATP) or glycogen (3 ATP) in absence of 02 to produce lactate + H+
- Occurs within the ……
- Relatively ….. but limited in its supply of ATP
Primary byproduct – H+
* Inhibits ….. enzymes (PFK)
* ….. actin myosin coupling
* Alters ….. signalling
Breakdown of glucose (2 ATP) or glycogen (3 ATP) in absence of 02 to produce lactate + H+
- Occurs within the cytoplasm
- Relatively fast but limited in its supply of ATP
Primary byproduct – H+
* Inhibits glycolytic enzymes (PFK)
* Inhibits actin myosin coupling
* Alters neural signalling
Effects of sprint training: enzyme activity
High energy phosphate metabolism
* Increased rate of ATP ….. in elite sprinters
…… (MK)
* Critical enzyme in ATP resynthesis
* ~…..% greater in elite sprint athletes
Creatine kinase (CK)
* Catalyses breakdown of PCr
* Elite athletes have ~…..% greater CK activity
Glycogen phosphorylase (PHOS)
* Converts stored muscle glycogen into glucose for ……
* Increased in elite sprinters
Phosphofructokinase (PFK)
* ….. …… ….. in glycolysis – catalyses phosphorylation of fructose-6-phosphate
* ….. duration sprint efforts increases PFK activity
….. …… (LDH)
* Catalyses pyruvate to lactate
* LDH activity ….. with short (<10s) and long (>10s) sprint training
Important enzymes in glycolytic pathway – glycolysis contributes ….-….% of energy in 10s sprint
Resynthesis
Myokinase, 20%
36%
Glycolysis
Rate limiting enzyme
Longer
Lactate dehydrogenase
Increased
55-75%
Metabolic adaptations
Aerobic energy system
* Contributes ~…..% of energy during 10s sprint
* Krebs cycle adaptations evident in ….. duration/distance sprints
* Increased ….. ….. synthase and ….. ….. activity in elite sprinters
Intramuscular buffering capacity
* Increased with longer-duration sprint efforts (>10 seconds)
* Limited evidence for shorter sprints
13%
Longer
Citrate synthase
Succinate dehydrogenase
Adaptations in fibre type from high-intensity exercise
- Sprinters = larger portion of type …. fibres
- Daily training results in shift to type …. Cadefau et al., 1990)
Type II
Type I
Hypertrophy
Muscle fibre size
* Longer-term training studies (>…..) have shown significant ….. in type I and II fibre size
* Several studies have demonstrated ….. - …..% increases in fibre diameter
Sarcoplasmic reticulum
* Permits muscle contraction and relaxation through release and …… of Ca2
* Studies show increased ….. …… volume in trained muscle
* Increases capacity for Ca2+ release and reuptake to allow greater actin-myosin …… cycling
8 weeks
Increases
4-16%
Reuptake
Sarcoplasmic reticuluum
Crossbridge
Effects of sprint training: neuromuscular changes
Muscle conduction velocity
* The time required for impulse to travel from ….. ….. to length of ….. muscle determines the speed of contraction
* Limited research suggests …. ….. conduction velocity is increased in sprint-trained athletes
Neural adaptations
* Improved …… …… velocity
* Increased motor unit ……, coordination, firing rate
Other adaptations
* Increased pain tolerance
* Increased movement efficiency
* Increased aerobic capacity (>30 seconds)
Motor unit, innervated
Muscle conduction
Neural conduction
Synchronisation
Effects of sprint training – performance changes
- Increases in maximal ….. output
- Increases in total ….. performed
- Increases in average power output
- Measure improvements with as little as ….. weeks of training
- …..x/week generally inefficient use of training time (*research not on highly trained individuals)
- Adaptations dependent on training stimuli
Power
Work
3
>3
At 10s of exercise contribution from anaerobic is …..% vs …..% aerobic
At 240s of exercise contribution from anaerobic is …..% vs ….%
At 10s of exercise contribution from anaerobic is 95% vs 5% aerobic
At 240s of exercise contribution from anaerobic is 22% vs 78%
