exercise threshold

Utilization of a given energy system is dependent on

• rate of energy demand

  • magnitude, timeline

• Substrate availability

• local (mitoch) oxygen supply

Rate of energy demand and utilization energy

• it takes time for aerobic system to supply energy

• aerobic energy is pretty slow (low rate)

Substrate avialability and utilization energy system

• ATP + PCr run out

• without substrate we can’t do metabolism

Local oxygen supply (in mitoch)

• limits on O2 supply will limit aerobic performance

Oxygen at any given time can be

• in the lungs

• bound to hemoglobin within the blood

• bound to myoglobin in the muscle

• in the mitochondria

In order for oxygen to be consumed it has to be

• present in the mitochondria of the working muscle

• if oxygen is not present or present in sufficient amounts then the muscle must utilize anerobic sources

Oxygen does no good when

• oxygen in the lungs or blood does the exerciser no good

• oxygen bound to myoglobin in non-active muscles does the exerciser no good

Local muscle can have insufficent oxygen supply for aerobic metabolizm

Insufficient oxygen supply for aerobic metabolism results

in anaerobic compensation which will lead to fatigue

Oxygen defecit can be

brief

sustained

brief oxygen defecit

• quickly resolved deficiencies in oxygen supply

• At Onset of exercise or increase in intensity

• small, brief, loca

Sustained oxygen deficit

• deficiency in oxygen supply so anaerobic has to supplement energy supply

  • larger, sustained and accumlating, becoming systemic

look into oxygen deficit

two metabolic boundaries

• threshold one

• threshold twothreshol

threshold one

the intensity at which blood lactate can be maintained at resting levels

threshold 2

the intensity at which lactate production within muscle may be stabilized in blood

production and clearance of lactate look

H+ clearance

• cleared by using bicarbonate buffering

bicarbonate buffering

HCO3 combines with H+ to form water and carbon dioxide

Lactate clearance

lactate is converted back into pyruvate

clearance of lactate and H+ can occur in both

• the muscle of origin

• the blood

Lactate and H+ are produced in _______ but cleared _____

produced in the muscle

cleared in the muscle and in the blood

order of metabolic boundaries order

moderate, threshold one, heacy, threshold 2, severe

Moderate section

• mostly aerobic, whatever lactate that is produced gets buffered locally

• no change in blood lactate

Heavy area

lactate production in the muscle exceeds lactate clearence in the muscle but is buffered in the blood

• lactate spilling over into blood

Severe exercise

lactate production in the muscle exceeds systemic lactate clearance

• blood lactate accumulation accelerates

lactate in moderate

lactate is produced and cleared locally

lactate and heavy

too much lactate is produced so it has to be cleared systemically

severe lactate exercise

too much lactate is produced overall, systemic clearance can’t keep up

Higher intensity domain training is

shorter in duration and requires greater recovery

Lower intensity training is

longer in duration but requires shorter recovery

Energy system activation is dependent on

rate of demand, substrate availability, oxygen supply

at higher intensities oxygen

supplies fails to meet energy demand

intensity can be quantified based on relationship between

lactate production and clearance (thresholds)

At the onset of exercise,

anaerobic systems compensate for delays in aerobic metabolism (ocygen defecit)