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7/30/2019 HPHE 6720 - Topic 3
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Topic 3:
Determination of the Lactate and
Ventilatory Thresholds
Laboratory Manual Section 03
HPHE 6720
Dr. Cheatham
Review of Physiology, Methods of Detection, and
Application
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Goals for this Topic
Understand the physiological origins of lacticacid/lactate
Understand the concepts of the lactate
threshold and ventilatory threshold Become familiar with the protocols, equipment,
testing procedures to measure LT/VT Become familiar with the analysis methods to
determine the LT/VT
Understand the relationship betweenperformance and the LT/VT
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Physiology of Lactate Production
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One cause of lactate threshold: Fate of pyruvate is lactate when
mitochondrial hydrogen shuttle cannot keep pace with accelerated rate ofglycolysis (increased rate of glycolytic production of NADH+ H+)
Physiology of Lactate Production
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Lactate During Exercise
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Lactate During Exercise
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Definition of Lactate Threshold
Lactate threshold is defined as the workload, or
exercise intensity, at which lactate begins to
accumulate in the blood.
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Physiological Basis of LT
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Methods of Detection of LT
Two-Line Regression Model Beaver, W., Wasserman, K., & Whipp, B. (1986). A new method for
detecting anaerobic threshold by gas exchange. Journal of Applied
Physiology, 60(6), 2020-2027.
Fixed Blood Lactate Concentrations
2.0, 4.0 mmol/L
Individual Anaerobic Threshold (IAT)
Stegmann, H., Kindermann, W. & Schnabel, A. (1981) Lactate kinetics
and individual anaerobic threshold. International Journal of Sports
Medicine, 2, 160-165.
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Methods of Detection of LT
Two-Line Regression Model
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Methods of Detection of LT
Fixed Blood Lactate Concentrations
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Ventilatory Threshold (VT) - Definition
The point during incremental exercise at which
ventilation increases out of proportion to the
increase in oxygen uptake
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VT - Physiological Basis
The increase in H+ from lactic acid dissociation isbuffered by bicarb system
The end result is an increase in CO2
Ventilation increases in order to rid body of excess CO2
H+ + HCO3- H2CO3 H2O + CO2
Lactic Acid Lactate- + H+
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VT - Determination
Protocol Considerations
Similar protocols to LT test
However, shorter continuous test can be used
because of rapid alterations in ventilation
Three Main Methods
Ventilation curve
V-slope method
Ventilatory equivalents method
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VT - Determination
Ventilation Curve Plot VE vs. VO2 or Watts or Time
The point at which there is a non-linear increase inventilation
V-Slope Method Plot VO2 vs. VCO2
The point at which the increase in VCO2 in greater thanthe increase in VO2
Ventilatory Equivalents Method
Plot VE/VO2 and VE/VCO2 vs. Watts or time or VO2
Point at which VE/VO2 increases while VE/VCO2
decreases or stays the same.
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VT Determination - VE Curve
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VT - Determination
Ventilation Curve Plot VE vs. VO2 or Watts or Time
The point at which there is a non-linear increase inventilation
V-Slope Method Plot VO2 vs. VCO2
The point at which the increase in VCO2 in greater thanthe increase in VO2
Ventilatory Equivalents Method
Plot VE/VO2 and VE/VCO2 vs. Watts or time or VO2
Point at which VE/VO2 increases while VE/VCO2
decreases or stays the same.
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VT Determination - V Slope Method
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
VO2 (L/min)
VCO2(L/m
in)
VT Breakpoint
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VT - Determination
Ventilation Curve Plot VE vs. VO2 or Watts or Time
The point at which there is a non-linear increase inventilation
V-Slope Method Plot VO2 vs. VCO2
The point at which the increase in VCO2 in greater thanthe increase in VO2
Ventilatory Equivalents Method
Plot VE/VO2 and VE/VCO2 vs. Watts or time or VO2
Point at which VE/VO2 increases while VE/VCO2
decreases or stays the same.
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VT - Ventilatory Equivalents Plot
10
15
20
25
30
35
40
45
50
25 50 75 100 125 150 175 200 225 250 275 300
Exercise Intensity (Watts)
VE/VO2orV
E/VCO2
VE/VO2
VE/VCO2
VT Breakpoint
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How is LT/VT Expressed?
VO2 at LT/VT
Percentage of
VO2max at LT/VT
Workload/Exercise
intensity at LT/VT
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LT/VT and Performance
Farrell et al. (1979) LT was significantly correlated with performance
time during long distance running (3.2km tomarathon)
r > 0.91 (VO2max r > 0.83) Kumagai et al. (1982)
Correlated performance time in 5km, 10km, and 10mile runs with LT
LT: 5km r = 0.945 10km r = 0.839 10m r = 0.835
VO2max: 5km r = 0.645 10km r = 0.674 10m r = 0.574
Powers et al. (1983) Correlated VO2max, running economy and VT to performance time in
10km road race
VT: r = 0.94 RE: r = 0.51 VO2max: r = 0.38
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Lactic acid accumulation contributes to
muscular fatigue
H+ ion interferes with Ca2+ binding to troponin-C
Lactate ion may also interfere with this binding
Alteration in fiber type utilization
Alterations in substrate utilization
Mechanism for LT/VT Affecting Performance
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Class Project
We will perform one maximal graded exercisetest on a cycle ergometer to determine the
LT/VT.
Student will use a variety of analysis techniquesto identify the LT/VT.