LT refers to the exercise intensity at which lactate production exceeds removal and begins to accumulate. It is an important determinant of endurance performance and provides a measure of metabolic fitness compared to VO2max as a measure of cardiovascular fitness. LT can be measured in various ways that are closely related. Factors like muscle mitochondria, fiber type, exercise mode determine LT. Training, especially continuous training around threshold, can significantly improve LT over a season in athletes. Interval training may also effectively raise LT.

1. Lactate threshold:
what does it really mean?
Andrew R. Coggan, Ph.D.
Cardiovascular Imaging Laboratory
Washington University School of Medicine
St. Louis, MO 63110

2. Lactate threshold (LT)
•
•
•
•
•
What is it?
How do you measure it?
Why is it important?
What determines it?
How do you train it?

3. LT – what is it?
Definition
• The exercise intensity at which lactate production
exceeds lactate removal, and thus begins to
accumulate in muscle and hence in the blood.
Related concepts
• OBLA, MLSS, lactate minimum, individual
anaerobic threshold, ventilatory (anaerobic)
threshold, critical power, etc.

4. Lactate threshold: the theory

5. Lactate threshold: the reality
Smith et al., MSSE 29:654-660, 1997

6. Blood lactate as a function of time
during exercise at a constant intensity
245 W
275 W
310 W
325 W
6
5
4
Time to fatigue @ 310 W: 58 min
3
)
/
m
(
a
L
H
d
o
l
B
2
1
0
0
2
4
6
Time (min)
8
10

7. Lactate minimum as an estimate of
maximal lactate steady state
Tegtbur, Busse, and Braumann MSSE 25:620-627, 1993

8. LT: why multiple criteria?
• The concept of a lactate “threshold” is really just a
convenient way of describing, with a single number, the
non-linear relationship between lactate concentration
and exercise intensity.

9. LT – why is it important?
• LT is the single most important physiological
determinant of endurance exercise performance.
• Many physiological responses to exercise are more
closely related to metabolic fitness (i.e., LT) than
they are to cardiovascular fitness (i.e., VO2max).

10. Relationship of performance to LT
when VO2max is constant
Coyle et al., J Appl Physiol
64:2622-2630, 1988

11. Relationship of muscle glycogen use
to LT when VO2max is constant

12. LT – what determines it?
Many factors
•
•
•
•
Number and/or size of muscle mitochondria
Fiber type/motor unit recruitment
Mode of exercise (muscle recruitment)
Hormonal response

13. Characteristics of human slow and fast
twitch muscle fibers

14. RAMPLIKE RECRUITMENT OF FIBERS

15. Fiber type recruitment as a function of
exercise intensity
100
Total
80
60
Type I
a
d
t
u
c
s
r
e
b
i
f
%
i
c
r
x
f
t
e
s
n
o
40
Type IIa
20
Type IIb
0
25
50
75
% of VO2max
Vollestad et al. Acta Physiol Scand 125:395-405, 1985
100

16. Effect of mode of
exercise on LT in
trained cyclists
Coyle et al., J Appl Physiol
64:2622-2630, 1988

17. Training-induced changes in LT over the
course of a season in triathletes
+6%
+10%
Kohrt, O’Conner, and Skinner, MSSE 21:569-575, 1989

18. Changes in lactate and epinephrine as a
function of exercise intensity
Mazzeo and Marshall, J Appl Physiol 67:1319-1322, 1989

19. Physiological responses related to LT
• Muscle glycogenolysis
• Glucose uptake,
production, &
concentration
• Plasma K+
• Plasma NH4+
•
•
•
•
•
• Pi/PCr (ADPf)
• Etc.
• Epinephrine
• Norepinephrine
Growth hormone
Cortisol
ß-endorphin
Ventilation
iEMG
• Muscle pO2

20. LT – how do you train it?
• At least/especially in untrained persons, training
at a wide range of intensities and durations will
tend to lead to rapid improvements in LT, but
• For trained athletes there may be particular
benefit to continuous training at circa-threshold
intensities.

21. Effect of continuous versus interval
training on VO2max and citrate
synthase activity
Gorostiaga et al. Eur J Appl Physiol Occup Physiol 63:101-107, 1991

22. Effect of continuous versus interval
training on blood lactate
concentration during exercise
Continuous exercise
Before
training
Interval exercise
Same
Same
absolute
relative
Before
training
Same
Same
absolute
relative
intensity
intensity
intensity
intensity
4.7±1.1
2.5±0.4*
2.5±0.3*†
6.2±0.8
4.1±0.3*
5.8±0.8
4.8±1.0
3.0±0.7*
5.1±0.9
8.8±1.6
4.3±0.4*
9.0±1.3
Continuous
training
group
Interval
training
group
Gorostiaga et al. Eur J Appl Physiol Occup Physiol 63:101-107, 1991

23. The “sweet spot”?
100
90
Arbitrary units
80
L2
Training effect
(increase in threshold power)
L1
L4
L3
L5
L6
70
60
50
40
Physiological strain
30
20
10
Maximum duration (volume)
0
40
50
60
70
80
90
100
110
120
Exercise intensity (% of functional threshold power)
130
140
150

24. Key Points
Lactate threshold (LT)
 is, at least in theory, the exercise intensity at which
lactate production exceeds lactate removal.
 can be measured in various ways, all of which
provide different, but closely interrelated, values.
 is an excellent predictor of endurance exercise
performance.
(continued)

25. Key Points (continued)
Lactate threshold (LT)
 provides a measure of a person’s metabolic fitness,
as opposed to their cardiovascular fitness (i.e.,
VO2max).
 determines numerous metabolic and neurohormonal
responses to exercise.
 in turn is determined by numerous factors, but
especially muscle respiratory capacity (mitochondrial
content).
(continued)

26. Key Points (continued)
Lactate threshold (LT)
 responds rapidly (at least initially) to training at a
wide variety of intensities and durations, but
 may be particularly improved by continuous training
in the “sweet spot”.