Lactate threshold

Question 1

current consensus on whether lactate is good or bad during exercise

What actually leads to fatigue

Answer 1

does not directly lead to fatigue. Its associated with increased H+. Accumulation of H+ is actually caused by ATP hydrolysis (break of ATP to ADP).

its utilized

Question 2

What system causes lactate accum. explain path.

Answer 2

Rapid glycolysis - Glucose or glycogen converted to pyruvate then lactate

Question 3

what happen once lactate forms in muscle (2 paths)

Answer 3

• diffuse into blood for buffering and removal to be oxidized in other tissues
• provide gluconeogenic substrate for glycogen synthesis
  *substrate is molecule acted on by enzyme.
• ultimately used for fuel or converted back to glucose
• moved via lactate shuttle

Question 4

what percent of aerobic capacity (VO2 max) does lactate start to accumulate. When is point of lactate threshold (single point and two point method).

How this number differ with aerobically trained people and why (3).

Answer 4

> 50-55%

according to single point method the point just before lactate accumulation is the lactate threshold (point just before graph starts to curve up)

two point - (more accurate) - 1st thresh: production increases above resting levels. 2nd thresh: lactate prod outpaces clearance (steady state no longer possible)

For trained - 80-90% VO2 max because of

• decreased lactate prod
• Local adaptations (e.g. mito)
• rapid lactate removal at all intensities

Question 5

what adaptations will sprint training give you (2)

Answer 5

increased glycogen stores in muscle

increased glycolytic related enzymes

Question 6

hypoxia theory and enzyme involved

describe study tested this and findings

Answer 6

theory that reduced O2 availability in muscle mitochondria causes increased LDH (lactate dehydrogenase enzyme) conversion of pyruvate to lactate

study alter ratio oof O2 in air to test normoxia, hypoxia, and hyperoxia.

Found that increased O2 not abolish lactate accumulation.

Question 7

Explain “math” theory of lactate

Answer 7

lactate is continuously formed regardless of hypoxia.

occur when lactate accum is greater thna clearance

Question 8

Explain fibre recruitment theory of lactate

Answer 8

Fast twitch fibres favour pyruvate to lactate and slow twitch fibres favour lactate to pyruvate.

When exercising higher intensities, use more fast twitch therefore create more lactate

Question 9

ventilatory threshold

when occur compared to lactate thresh

Answer 9

point where ventilation increases disproportionally to increase in O2 consump.

(breath more rapid for non-proportional increase in O2 uptake.

occurs suring or just after LT

Question 10

why blow off ventilate more frequently when go above lactate threshold (2)

Answer 10

try get more O2 in

mostly to blow off more CO2 to reduce blood acidity

Question 11

what was the previous idea of lactic acid

Answer 11

that it was a waste product that caused muscle acidosis and lead to fatigue and exhaustion.

Question 12

lactic acid vs lactate

Answer 12

lactic acid - not actually much in body. Is briefly formed in body when NADH+H oxidizes but dissociates into lactate and H+ due to body tissue pH
- Mostly in fermented foods like yoghurt - bacteria convert lactose to lactic acid.

lactate - correct term. does not directly lead to fatigue. Its associated with increased H+. Accumulation of H+ is actually caused by ATP hydrolysis (break of ATP to ADP)

Question 13

Describe lactate shuttle
- what transports lactate
- where it goes

Answer 13

• Monocarboxylate transport protein (MCT) transport lactate

intracellular - go to mitochondria and used for en

extracellular - MCT bring to type I fibre mito, liver, or liver

Question 14

what did a study find when inject lactate into blood

Answer 14

lactate signalled to down regulate glucose use while lactate use increased.

indicates muscle rather use lactate than glucose.

lactate = valuable fuel source reducing need for glucose

RPE stayed the same