Dear VeloNews Training Center,
I've heard that lactate threshold is something that isn't entirely genetic and that it can be "trained."
Can you explain the genetic/training aspects of lactate threshold and VO2 max and why one is said to be trainable and the other not?
Also, if LT is trainable, what is the best way to go about it?
—Todd
Both VO2 max and lactate threshold have genetically determined limits; however, most individuals have not reached their potential.
VO2 Max
VO2 max is defined as the maximal rate of oxygen consumed by an exercising individual. An excellent resource for understanding this topic is Bassett and Howley's paper "Limiting factors for maximum oxygen uptake and determinants of endurance performance" (Medicine and Science in Sports and Exercise volume 33, 2000). This paper outlines that VO2 max is limited by oxygen delivery to the muscles and not the muscles' ability to utilize oxygen.
They report a muscle can process two to three times the oxygen when exercised in isolation rather than a whole-body maximal effort. Therefore, a muscle is able to utilize much more oxygen than is delivered during typical endurance activities.
The pulmonary and cardiovascular systems are primarily responsible for the delivery of oxygen. The pulmonary system is more than adequate in almost all cases, especially when exercising at sea level.There may be slight limitations in compromised individuals (e.g. Asthma, chronic obstructive pulmonary disease (COPD), the most elite endurance-trained athletes and those exercising at high altitude.
The cardiovascular system, responsible for the rate of oxygen delivery, is thought to be responsible for 70 to 85 percent of the limitation of VO2max. We typically see increases in VO2 max associated with large volumes of training at low intensities (55 to 65 percent of LT power) over long periods of time.
Furthermore, training at very high intensities (110 to 135 percent of LT power) for short intervals (1 to 5 minutes) also improves maximal aerobic power.
Another limiter, oxygen carrying capacity of the blood, is the target of altitude acclimatization. As the body acclimatizes, it secretes a natural form of EPO which causes production of red blood cells: increasing oxygen carrying capacity. This aspect cannot be "trained" in the traditional sense and may potentially decrease slightly with high volumes of training due to a possible associated decrease in red blood cell count.
Lactate Threshold
While VO2 max is limited by "central" systems, lactate threshold is primary limited by "peripheral." While exercising at increasing workloads, the aerobic system eventually becomes unable to supply all the needed energy. To meet the increasing demand, the body dips into its "anaerobic" energy supply, which results in less energy (ATP) production per gram of carbohydrate than does aerobic metabolism. Because lactate is a by-product of anaerobic metabolism, lactate levels rise in the blood as the anaerobic system increases its contribution to energy production.
A contributor to fatigue is the increased reliance on the anaerobic metabolic system, not the lactate molecule itself. Lactate threshold, loosely defined, is the workload which elicits substantial and unsustainable levels of lactate production relative to lactate clearance from the blood (anaerobic contribution).
This workload is typically sustainable for an hour with difficulty and correlates highly to endurance performance regardless of distance. The threshold itself is trainable by increasing the ability of the aerobic system to supply power at higher workloads.
By reducing and delaying the contribution of the anaerobic system, sustainable power output is improved. We typically see improvement in LT with large volumes of low intensity training and sustained efforts (20 minutes to 1 hour) and moderate duration intervals (5 to 20min) at 90 to 110 percent of your threshold intensity.
