Semester 1 harder content

How is lactic acidosis partially responsible for the priming effect?

1. Potassium accumulation in the interstitial space deactivates voltage-gated sodium channels. Lactate/ lactic acid interacts with chloride channels on the muscle membrane. Chloride ions enter the cell, repolarising the membrane so voltage-gated sodium channels are reactivated.

2. Lactic acidosis induces a Bohr shift for faster oxygen unloading. Though this is just a benefit in those who are limited by oxygen delivery.

How do altered motor unit recruitment patterns benefit priming?

More motor units are recruited from the onset of exercise so that load is distributed over more fibres and they fatigue less quickly.

Henneman’s size principle: More motor units are recruited over time, with more oxidative ones recruited first.

3 ways priming improves performance

Sped-up oxygen uptake kinetics, enhanced motor unit recruitment patterns, mild lactic acidosis

Advantages and disadvantages of GPS monitoring and camera monitoring like ProZone

GPS: Cheap, but doesn’t work indoors and can be bad in stadiums

Prozone: Can be used indoors but multiple cameras makes it expensive

Research: demands of intermittent sports

VO2 max, distance, performance trends etc

Footballers run and sprint more than jog and walk.

Performance (capacity for high-intensity bouts) significantly declines in the second half.

Demands and configuration and tactical approach-specific

Demands are position-specific.

Requires all major energy systems.

Football requires average 70-80% VO2 max.

Mitochondrial biogenesis contributes to improved mitochondrial respiration, and its the cause of increased mitochondrial content.

Name some other changes involved in improved mitochondrial respiratory function.

(Not important to get all, just read the answer and ensure you understand biogenesis isn’t just leading to content increase)

• Greater abundance and/or activity of proteins in complexes I–IV of ETC.

• Changes in ATP synthase (complex V) and associated oxidative phosphorylation machinery.

• Greater activity or abundance of enzymes involved in pyruvate oxidation, the TCA cycle and sometimes fatty acid oxidation so more NADH and FADH₂ can be supplied to the electron transport chain

• Improved mitochondrial ADP responsiveness, so potentially greater respiration at a given ADP concentration

• Mitochondrial biogenesis

MICT, SIT, HIIT: Percentages of VO2 max, PAP and max HR

MICT: 50-80% VO2 max/ PAP, ~70% max HR, no scheduled recovery

HIIT: 75-100% VO2 max/ PAP, 85-90% max HR, 6-10 reps, 1-5min on and off

SIT: 100% VO2 max, 170% PAP, all-out 30s, 4 min rest, 4-7 reps

Explain why carbohydrate ingestion immediately following glycogen-depleting exercise can accelerate muscle glycogen resynthesis.

Glycogen-depleting exercise increases:

• activity of glycogen synthase

• insulin sensitivity

• GLUT4 availability

This promotes glucose uptake and glycogen synthesis.

These effects are particularly advantageous during the early post-exercise recovery period, allowing glycogen synthesis rates to be elevated.

What are the experimental methods used to monitor mitochondrial content versus respiration?

Muscle biopsies

Content:

• CS activity, since CS is exclusively mitochondrial (KC)

• Other enzymes like SDH

Respiration:

Fibres or isolated mitochondria are analysed via high-resolution respirometry, where oxygen consumption flux is measured in real time.

Specific substrates (such as pyruvate, malate, or succinate) and ADP are added to sequentially stimulate complexes of the ETC, providing a direct measurement of mass-specific mitochondrial respiration (oxygen flux per unit of tissue or mitochondrial protein).