Physiology of endurance athlete

Question 1

What is a possible explanation for endurance exercise?

Answer 1

• Continuous activity beyond 5 minutes, but less than 4 hours
• Exercise that predominantly requires the oxidative/aerobic systems for energy

Question 2

What are the problems with the current literature definitions and consensus for ultra/ endurance?

Answer 2

• Current literature states events exceeding 4-6 hours and that can last up to 40 hours/days. Also suggestions for running that it can be considered distances greater than a marathon.
• However, elite athletes can run the marathon in times close to 2 hours therefore is a distance slightly longer than that which would still be under 4 hours actually ultra endurance?
• On the other end of the spectrum normal population some may take more than 4 hours to complete the marathon therefore is that ultra endurance or not.

Question 3

What are the considerations for an ultra endurance athlete to achieve excellent exercise management?

Answer 3

• Long term preparation through Periodisation of training, injury management and suitable goal setting
• Optimal rate of movement so understanding race pace, training pace and efficiency of effort
• Overtraining and prevention of injuries
• Sufficient nutrition both pre training and competition and during and good management of CHO, FATS, PRO and hydration
• Psychological toughness as racing for prolonged periods and multiple days will be tough

Question 4

What are the physiological factors influencing endurance performance?

Answer 4

• Aerobic capacity – well developed aerobic capacity prerequisite for endurance performance
• Lactate threshold has a strong relationship with endurance performance depending on distance
• Economy. Improve economy results in lower o2 consumption and lower rate of fuel consumption
• Performance VO2 – Improved fractional utilization of vo2 results in improve performance. The ability to sustain a higher vo2 max at race pace.
• Fuel supply. Ability to oxidise fats at submax intensity and therefore spares glycogen thus delaying fatigue.

Question 5

What is the role of VO2max in running performance?

Answer 5

• An indicator of potential endurance performance
• An indicator of training status
• Represents maximal rate of ATP generation aerobically and therefore provides an upper ceiling for endurance performance
• However, it does not determine performance

Question 6

Why does muscle capillary density, stroke volume and aerobic enzyme activity impacts on vo2max?

Answer 6

• Maximal cardiac output is one the main limiting factors of vo2max. As stroke volume is something the directly influences maximal cardiac output, therefore, increases in stroke volume allow for further increases in cardiac output and vo2max.
• Muscle capillary density is known to increase with endurance training as it increases the mean transit time of blood through the muscle and improves oxygen extraction from the muscle. Maintenance of avo2 diff even at high intensities
• When mitochondrial size and density increases this is accompanied with an increase in aerobic enzymes that increase the capacity for aerobic re-synthesis of ATP. Therefore this increases the percentage of vo2max exercise can be performed at.

Question 7

What does the control of lactate/steady state and the mass action effect refer to?

Answer 7

• Lactic acid is regulated so that production and removal result in blood concentrations between 0.5-1.5mmol/L at rest. Therefore, when ra=rd the blood lactate concentrations does not change which is optimal.
• Mass action effect refers to increase lactate production caused by increase rate of glycolysis – ra>rd
• This can indirectly cause fatigue if something is not done or try to get back to steady state

Question 8

Why does lactate not cause fatigue/ why does acidosis cause an athlete to slow down?

Answer 8

• As lactate is produced a proton of H+ is released. These protons can decrease the PH causing a more acidic environment
• The decrease in PH inhibits PFK which is the rate limiting enzyme of glycolysis. Calcium release is also inhibited therefore this affects muscular contraction.
• Lactate doesn’t cause fatigue it’s the acidosis that affects the enzymes of energy metabolism and muscle contraction

Question 9

If two athletes have similar vo2 values what sub max physiological factors are better used to see differences in endurance performance?

Answer 9

• Running economy
• Running velocity at vo2max
• Physiology measures related to accumulation of blood lactate

Question 10

What are the characteristics and factors affecting running economy?

Answer 10

• Running economy can vary by 30% in runners with similar vo2max
• Running economy is a better predictor of performance than vo2max
• Running economy is difficult to improve
• 5% improvement in RE = 3.8% improvement in vo2 max
• greater % slow twitch fibers are associated with better RE.

Question 11

How does an increase in muscle capillarisation affect avo2-diff?

Answer 11

• Increase capillary density in the muscle
• Increase mean transit time
• Maintenance of a-vO2 diff even at high intensities

Question 12

Explain why a greater percentage of slow twitch skeletal muscle fibers is associated with improve RE?

Answer 12

• The metabolic activity or speed of contraction of the muscle fibers seems to influence RE
• The greater percentage of slow twitch muscle fibers someone has, the more mitochondria are available resulting in less oxygen being used to maintain at a given power output. It also increases the capacity for aerobic re-synthesis of ATP and therefore be able to perform exercise whilst maintaining a higher %vo2max or perform the same absolute/relative amount of work at a lower % of vo2max
• Lower rate of oxygen consumption which is associated with an improved running economy

Question 13

Why would an athlete with improve running economy have a better lactate threshold velocity?

Answer 13

• An improved running economy would suggest a more efficient use of oxygen, lower rate of fuel consumption and a low rate of o2 consumption
• Therefore, lactate threshold velocity will be higher as they can run faster at a lower metabolic cost
• Improvements in running economy improves vo2max. Together these can reduce the relative intensity of running
• The more economical a runner the lower percentage of vo2max they can run at, resulting in a lower lactate accumulation at a given speed

Question 14

How does training in a glycogen depleted state improve endurance performance?

Answer 14

• Low glycogen availability causes a shift in substrate metabolism during and after exercise.
• Enhanced fat mobilization and use of fatty acids for fuel – fat oxidation increases
• Sparing of muscle glycogen and great increase in enzyme activity.
• Deferred accumulation of waste products associated with glycolysis