Acute responses to sprint exercise

Question 1

How long would ATP stores last during maximal sprinting if not continuously resynthesised?

Answer 1

~2 seconds

Question 2

Roughly, what is the concentration of ATP in the cell?

Answer 2

5 mmol per kg

Question 3

How is sprint performance most commonly assessed?

Answer 3

Wingate test

Question 4

What 3 performance outcomes can you take from a wingate test?

Answer 4

> peak power output (PPO)
end power output (EPO)
fatigue index % (PPO-EPO)

Question 5

How would you compare power outputs between individuals?

Answer 5

Watts per kg

Question 6

Compare type I and type II fibres in terms of force and power production capabilities at different velocities

Answer 6

type II fibres are able to produce greater force and power at a higher velocity of contraction than type I fibres, making them more useful in high speed movements (i.e. sprunting)

Question 7

Is ATP breakdown during exercise uniform across fibre types?

Answer 7

No,

ATP breakdown rates depends on the activity (demands placed on the different fibre types)

Question 8

During maximal sprinting ATP levels are reduced and there’s a rapid drop in PCr stores.
How do we continue to be able to sprint then?

Answer 8

Glycolysis

Question 9

At what time during high-intensity exercise is glycolysis maximally activated?

Answer 9

after ~5 seconds, plateauing from 5-15 seconds

Question 10

How does the energy contribution of different systems change over the course of a 30 s wingate sprint?

Answer 10

PCr and glycolysis are main contributors in first 6 s.
PCr drops off from 6-15 s and glycolysis is main energy source.
From 15-30 s, glycolysis drops in contribution and oxidative phosphorylation becomes major energy source.

ATP turnover rate drops across the 30 s.
- (Parolin et al, 1999)

Question 11

How much muscle glycogen is broken down over a 15 s sprint?

Answer 11

~20-30 %

Question 12

What happens to levels of glycogenolysis over a 30 s sprint and with the execution of a repeat sprint.

Answer 12

In the first sprint, glycogenolysis drops sharply after 15 s.
Levels of glycogenolysis are much lower in repeat sprint bouts due to lower levels of glycolysis.
- (Parolin et al, 1999)

Question 13

Blood lactate stays stable from pre-exercise to post-exercise.
True or False?

Answer 13

False.
Blood lactate is significantly higher 3 minutes post exercise.
- (Esbjornsson-Liljedahl et al, 1999)

Question 14

What is the result of this blood lactate increase on glycolysis and performance?

Answer 14

> pH drops (metabolic acidosis), from 7.0 to 6.4 in the muscle with intense exercise.
low pH inhibits PFK, almost completing inhibiting glycolysis at pH = 6.4.
excessive H ions interferes with the formation of actin/myosin cross-bridges.

Question 15

Is lactate definitely bad, all the time?

Answer 15

No,

lactate production is useful

Question 16

You can’t just go throwing blanket statements out there like that.
HOW is lactate production useful?

Answer 16

During high intensity exercise lactate production is couple with NAD production from NADH.
This is important as there is limited NAD.
Without lactate being produced, all NAD would be reduced to NADH, preventing glycolysis from proceeding.

Lactate production serves an important role in allowing sprinting to continue

Question 17

Lactate production reduces H ion levels.

True or False?

Answer 17

True,
by taking a H from NADH in the production of NAD.
- (Robergs et al, 2004)

Question 18

How does energy system contribution change over repeat sprints?

Answer 18

MUCH less contribution from glycolytic system.
Greater contribution from oxidative system.
Reduced contribution of PCr.

• (Parolin et al, 1999)

Question 19

What’s likely the limiting factor in power output over repeat sprints?

Answer 19

PCr resynthesis

Question 20

How is lactate accumulation and net balance affected by repeat sprints?

Answer 20

lactate accumulation drops substantially in repeat sprints due to reduced contribution of glycolysis to ATP resynthesis.
Net balance of lactate may even become negative after many sprints as glycolysis activity is so low and lactate is being cleared faster than it is being produced.

Question 21

Which of the aerobic or anaerobic energy systems can produce the most force?

Answer 21

anaerobic due to the greater recruitment of fast twitch fibres over slow twitch.

Question 22

How much does anaerobic energy system contribution to ATP resynthesis drop in a repeat sprint?

Answer 22

from around 69% (Medbo et al, 1999) to 41% (Bogdanis et al, 1996).
mainly down to glycolysis reduction.

Question 23

Is peak power drop during repeat sprints proportional with drop in glycolysis?

Answer 23

No,
because oxidative system plays a larger part in repeat sprints.
- (Parolin et al, 1999; Spencer et al, 2005)

Question 24

Why does peak power output fall across repeat sprints?

Answer 24

reduced contribution of anaerobic energy systems in the resynthesis of ATP.
- (Parolin et al, 1999)