PHYSIOLOGICAL DETERMINANTS OF ENDURANCE PERFORMANCE Flashcards
what is Maximal O2 consumption?
VO2max = oxygen consumption at a given work rate, beyond which no
further increase is observed (‘ceiling’ value of aerobic energy supply)
what is the Blood lactate threshold (LT)?
- The exercise intensity at which lactate produced by the muscle starts to accumulate in the blood
- Demarcates moderate to heavy exercise domains.
what the functional significance of the LT?
- Delayed onset on blood lactate accumulation
* Reduced metabolic perturbations at a given intensity
Two athletes both plan to race 20 km at 75% VO2max but athlete A has a LT at 60% VO2max and athlete B at 80% VO2max:
Are they exercising at the same intensity?
No. They are in different domains. Athlete A will be in a heavy domain, while Athlete B will be in a moderate domain.
Exercise domains: moderate?
All power outputs below LT
VO2 at steady state
Small changes in blood lactate
Endurance time >4hours
Exercise domains: Heavy?
Power outputs above LT but below CP
Blood Lactate elevated but stable over time
Endurance time 3-4 hours
Exercise domains: Severe?
power outputs above CP but below VO2 max
Blood Lactate elevated and keeps on ricing
Slow component evident and keeps on rising to max
Continuing exercise at this power will result in attainment of VO2 max
Endurance time: 15-50 mins
Exercise domains: Supramaximal?
No slow component
Endurance time <120 sec
All-out exercise, such that VO2 max is not attained.
VO2 max as a determinant: % of sustainable VO2 max over time:
Percentage of sustainable
VO2max over time:
- 5 km at close to 100% VO2max
- 10 km is performed at 90–100% VO2max
- Marathon = 75–85% VO2max
(corresponds to near LT)
VO2 max as a determinant: % of sustainable VO2 max over time: What does this tell us?
VO2max sets the ceiling but our capacity to sustain higher
fractions of this is important (fractional utilisation; Fr).
Factoring in functional speed: Running Economy (RE):
‘Oxygen used (fuel) for a given, sub-maximal
speed’
Oxygen per km covered (miles per gallon)
Conclusion to PR
• A high VO2max is a pre-requisite to set the ‘ceiling’ but not the only important factor
• A rightward shift in the LT curve in combination with
the RE at sub-max speed were the most significant
factors
• Speed at VO2max improvements also supported shorter 10 km performance
how to predict a marathon runners performance using three parameters:
𝐸 = Cr*v
• Maximal speed = the ratio of the maximal metabolic power (Emax ~ VO2max)
to the energy cost of locomotion at that speed (Cr). Thus;
V = VO2max / Cr
• Problem: we know Cr and VO2max but we can’t sustain VO2max, thus;
V = Fr*VO2max / Cr
In practice: Fr = 65% VO2max (0.65); VO2max = 60 mlO2 /kg/min Cr 0.182 mlO2 /kg/m Marathon velocity (m/min) = 0.65*60 / 0.182 = 214 m/min=
Speed = distance / Time thus; 42195 / 214 = 197 min (3 h 17 min)
Training for endurance: Delivery of blood and oxygen
VO2max is theoretically limited by the rate at which oxygen can be supplied to the muscles or the muscle’s ability to extract oxygen from the blood it receives.
VO2max is strongly related to the maximal cardiac output (Qmax) (consider this as delivery)
VO2 max= Q x (Ca O2-Cv O2)
Training for endurance: Endurance programmes and
myocardial (heart) changes
Left ventricular (LV) dimension ↑: • 7 weeks, 6 days / week; • Alternating between 40 min continuous or interval (5 x 5 min @ 85- 95% VO2max) (Cox et al., 1986).
LV dimension ↑: • 8 weeks, 3 days / week; • Interval (4 x 4 min @ 90 95% HRmax). • 18% ↑ VO2max • 13% ↑ LV mass • 12% LV contractility
