Your SlideShare is downloading. ×
Lt  what does it really mean
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Lt what does it really mean

918
views

Published on

Webinar for USA Cycling Coaching Education program.

Webinar for USA Cycling Coaching Education program.


0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
918
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
45
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 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”.

×