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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.