As the season approaches, and talk turns to shaving legs, Body Glide and Pam, you may also hear your friends talk about things like VO₂ max, VO₂ max pace, lactate threshold, or anaerobic threshold.  If you find your head spinning from all this scientific terminology or just want to know how these principles can help you get faster, then be sure to read this month’s Science of Speed column for a review of common athletic physiology terms.
 
VO₂ max: This stands for the maximal level of “oxygen (O₂) volume” that your body can utilize during strenuous exercise.  It is also called “aerobic capacity”.  We like to think of it as the size of your engine. It is measured in the lab by increasing the exercise workload every one minute (incremental ramp test) to three minutes (incremental steady state test) on a treadmill, cycle ergometer, rowing erg, swimming flume (e.g. ”endless pool”), x-country ski machine, etc.  During weight bearing exercise such as running, it is usually reported in relative units – milliliters of O₂ per kilogram of body weight per minute of exercise, or mL/kg/min.  For non-weight-bearing activity, such as cycling, it is often reported in absolute units – liters per minute, or L/min.
 
VO₂ max is the oldest variable for measuring overall cardiovascular fitness levels.  A sedentary adult who starts jogging 3 times a week can improve his or her VO₂ max by 20 to 25 percent in 10-15 weeks, or from 37 to 45 mL/kg/min, for example.  Many recreational triathletes will have VO₂ max’s in the 50’s, pretty good one’s in the low to mid 60’s, and elite racers in the high 60’s or 70’s.  Milers and 5K runners tend to have higher a VO₂ max than marathoners.  Coaching legend Dr. Jack Daniels reported that he tested Steve Prefontaine prior to the 1972 Olympics, while maybe in the best shape of his life, at 90 mL/kg/min.  Gulp.
 
So will a person with a higher VO₂ max always go faster than a person with a lower VO₂ max?  No.  The reason is that there are other variables important to race performance which can compensate for having a lower VO₂ max.  For example, the great miler Peter Snell was once measured at 72 mL/kg/min but he and Prefontaine both ran 3:54 miles.  VO₂ max is simply a measure of the general endurance potential under the hood.  Although someone with a VO₂ max of 50 will not be winning Ironman Hawaii next year, he or she is still capable of racing faster than people with a moderately higher VO₂ max.
 
It is important to note that once you are well trained, your VO₂ max will not increase by much, if at all.  However, VO₂ max does decrease with age, roughly 4-5 mL/kg/min every decade, or 25-40% from 20 to 65 years old in most people.  If there is not much a well-trained athlete can do to improve his or her VO₂ max, this leads to the question, “Which variables may prove more useful in improving training and performance?
 
Running velocity or power output at VO₂ max: Aha!  Now we have a winner.  Consistent with the results of the cycling study that we wrote about last month in which peak power output predicted performance in a 90-min time trial, numerous running studies have demonstrated that peak running pace at the end of an incremental test is highly correlated with performance in events from 8K and up.  Yes, not only in those short 10 K “sprints”.  Renowned exercise physiologist Dr. Tim Noakes found that ultramarathoners’ VO₂ max paces even predicted performance in 90K races.  Finally, some research that does not have to be extrapolated to apply to Ironman performance!
 
Anaerobic or lactate threshold: This is an increasingly popular variable that can be measured quite easily in a lab setting. It is most useful for determining training heart rates for different types of workouts.  It is less useful as a predictor of performance, though it does correlate more closely than VO₂ max .  Unfortunately, the lack of uniform criteria has caused some confusion among coaches and athletes.  “Anaerobic” threshold, or “onset of blood lactate accumulation” (OBLA) usually refers to the exercise workload or heart rate at which a blood lactate level of 4 mmol/L is elicited.  “Maximal lactate steady state” refers to the highest lactate level that can be maintained for the final 20 min of a 30 min exercise bout at a constant workload.  This definition takes into account that it can take at least 10-20 minutes for the blood lactate level to fully stabilize at a given workload.  Since that would take repeat testing on different days to pinpoint the threshold, the impracticality prohibits the pure use of that definition in the real world.  In the research arena, it has been noticed that the muscle groups used for different sports affect this variable.  Well-trained groups of speed skaters could hold a blood lactate level of 6.5 mmol/L, cyclists 5.0 mmol/L, and rowers 3.0 mmol/L. 
 
Another common criteria for determining the lactate threshold is the point on the lactate curve at which linearity ends and steeper increases of  >1 mmol/L occur with each increase in workload.  For training purposes, this must be interpreted with discernment because the inflection point can occur as low as ~2 mmol. 
 
To test recreational athletes who are employed and have to train on the side, a happy medium is to use 3-4 min incremental stages in one test to obtain a reasonable estimate of the blood lactate level at a given exercise intensity.  It is important to test when you are not fatigued or glycogen depleted.  Next month we will discuss the application of the lactate threshold to heart rate based training.
 
Fractional utilization of VO₂ max:  This is simply the percentage of your VO₂ max or your maximal heart rate (HR max) that can be sustained over a given race distance.  The legendary Dr. Per-Olaf Astrand roughly estimated that a well-trained endurance athlete can maintain 100% of VO₂ max (98-100% HR max) pace for approximately 10 min, 95% (96% HR max) for 30 min, 85% (90% HR max) for 1 hr, and 80% (85% HR max) for 2 hr.  Athletes with a lower VO₂ max must race at a higher fraction of their VO₂ max to beat someone with a higher VO₂ max.  Thus, it is advantageous to have a higher lactate threshold.  For example, highly trained athletes can have a threshold at 85-90% of VO₂ max (90-92% HR max) and moderately trained recreational athletes are often 75-84% VO₂ max (80-89% HR max).
 
Economy of Movement:  Obviously, the more efficient the running style or the better the swim strokes, the faster the performance.  This means that at a given pace, you have a lower VO₂ (use less oxygen) than a less efficient athlete.  Biomechanist Dr. Peter Cavanaugh found that the VO₂ of elite runners was 6% lower than that of sub-elite runners at a 6:00 mile pace.  Athletes with higher training volumes usually are more efficient than those with significantly lower training volumes (although this is not an excuse to overtrain).  Dr. Scrimgeour showed that runners training  >60 miles/wk had lower VO₂s at various paces than runners training less.  Of interest, physiologist Dr. David Costill found that at different paces, the VO₂ of marathoners was 5-10% lower than that of middle distance runners.
 
Summary:  These are a few of the variables that make you what you are in the pool or out on the road.  Though all are significant in distinguishing between different groups of athletes, within similar groupings, sweat, grit, and smart training can make up for an awful lot (i.e. your genetic lot in life).  As we mentioned last month, your pace or power output at VO₂ max is not only a good predictor of performance, but a good variable for tracking improvement. With this vocabulary set, we will start applying these principles to heart rate based training next month.  Sorry, too late to help for St. Croix, Lanzarote or Brazil, but just in time for Utah and Blackwater!
 
 
Dr. Dan Moser, Ph D, is the director of research and clinical services at ELITE Health & Wellness (http://www.elitewellness.com).  Coming from a background in track and field, he has  more than 10 years of experience testing professional and recreational athletes, including triathletes, runners, cyclists, in-line skaters, and hockey players.
 
Jeff Devlin is an endurance coach and former professional triathlete, who offers practical insights into the application of the latest science. Jeff holds five national championship titles and two 3rd place finishes at the Hawaii Ironman. He runs his own international coaching business, Human Performance Engineering (http://www.jeffdevlin.com).