KNES 203 - Thresholds and Domains

Describe exercise induced metabolic acidosis

Lactate and acidosis are highly correlated.

Lactic acid exists as lactate and it's formation consumes protons from ATP hydrolysis and the breakdowns of glucose and glycogen

What happens when ATP's needs exceed the capability of the aerobic system?

The anaerobic system steps in, but because the production of protons (H+) is higher than the consumption (lactate) then there is an accumulation of protons

What happens with H+ when exercise reaches higher intensities?

H+ accumulation

What is a threshold?

the specific magnitude or intensity needed to be reached for something to actually happen

What is domain?

separated by thresholds (you need to REACH a certain threshold to be in a certain DOMAIN)

Distinct physiological responses occur in each domain (Moderate, Heavy, or Severe)

Why are ramp incremental tests performed?

1) Determine maximal aerobic capacity (VO2max)

2) Identify cardiorespiratory response thresholds

What is the issue with percentage maximal values like VO2max and HRmax?

They don't account for individual exercise thresholds

Differences between Zones 1, 2, and 3 in the incremental ramp test

Zone 1/Moderate: Ventilation and Oxygen uptake match each other

Zone 2/Heavy: First Ventilation Threshold (GET), first deviation from the minute ventilation(Ve)-oxygen consumption(VO2) relationship

Zone 3/Severe: Second Ventilation Threshold (RCP), faster increase in minute ventilation

exercise intensity increases in the moderate domain...

Increase in oxygen consumption, carbon dioxide removal, and minute ventilation (Ve)

No significant increase in blood lactate concentration

When exercise intensity increases in the Heavy Domain...

Lactate production is higher than metabolizing production, increase in blood lactate concentration

Proton(H+) buffering by bicarbonate increases CO2 production

Steep increase of minute ventilation(Ve) but VO2 still maintains a linear increase with increasing workload

Despite increasing protons, the oxidative capacity of the system is able to cope

When exercise intensity increases in the Severe Domain...

Lactate production exceeds lactate elimination rate which greatly increases blood glucose levels

What happens as exercise intensity is constant in the Moderate Domain?

blood lactate will remain at similar level to resting values, and VO2 will reach a steady state fairly quickly

What happens as exercise intensity is constant in the Heavy Domain?

Blood lactate will eventually reach a steady state

VO2 will eventually reach a steady state but it will just take longer compared to Moderate

What happens as exercise intensity is constant in the Severe Domain?

VO2 and blood lactate WILL NOT reach a steady state, so lactate will accumulate an VO2 will eventually reach VO2max

What is the Maximum Lactate Steady State (MLSS)?

Highest constant intensity at which lactate can STILL STABILIZE over time

What is the talk test?

A good test marker for VT1, as between VT1 and VT2 you should still be able to speak

What is the power duration curve?

Plotting power output vs the duration that it can be sustained, we see a hyperbolic relationship

W represents the work that can be done above critical power (the line between heavy and severe domain)

What is functional threshold power?

as the highest power outputthat can be sustained for 60 min

what are fatigue mechanisms during moderate exercise

glycogen depletion

what are fatigue mechanisms during heavy exercise

metabolite disruption or glycogen depletion

what are fatigue mechanisms during severe exercise

disruption of metabolic milieu

What is gas exchange threshold (GET) and respiratory compensation point (RCP)

GET - carbon dioxide (VCO2) increases disproportionately to oxygen uptake (VO2) during exercise

RCP - partial pressure of carbon dioxide declines due to increasing exercise intensities