Fractional Utilization of VO2 Max (Lactate
Threshold)
Lactate is a substance found in your body
which plays a role in the metabolism to convert your energy stores into
productive mechanical energy in your body.
Though different people have slightly more or less lactate, everyone can
usually be found at rest around 1 mmol/L in the blood. When exercise begins,
the amount of lactate in the blood starts to become effected. Though extremely
gradual at first (perhaps unchanging for some), when the rate of carbohydrate
utilization is elevated, the body cannot buffer out all the waste products
creating higher levels of lactate accumulation in the blood. In other words,
when an athlete is running slowly the majority of the energy which is being
used is being taken care of in an efficient oxidative method which does not produce
significant waste products to hinder performance. We have talked about this
before in the “aerobic capacity” section earlier. When the running speed
increases, the metabolism rate of that individual increases. Due to the need
for high amounts of energy in this state, anaerobic glycolysis (rather than the more efficient oxidative phosphorylation) breaks down
energy stores leaving significant waste products. When a high concentration of
lactate is not transported in or out of cells quickly, accumulation of lactate
occurs. A higher ph occurs as well due to static hydrogen ions which inhibit muscle
contractions. This shows that the waste products, not the lactate alone, hinder
the performance of the runner. This waste product, now referred to as lactic
acid, as well as other factors (glycogen depletion, O2 flow, blood flow, etc)
collectively, are the cause of muscular fatigue in runners.
Lactic acid often is felt significantly at
the beginning of a training program because running form isn’t superior, MCTs 1
and 4’s expression is low, and Na/K pump expression is low. At the end of a
training program often running form is more efficient, MCTs become lactate
influx and effluxing engines and Na/K pumps in cells help resist against
hydrogen ion build ups. In other words, your body both on the outside and inside becomes more efficient at dealing with lactic acid.
If someone were to ask me how to describe
lactic acids effects in my own running I would tell them that from my
perspective lactic acid fatigue is synonymous with pain management. Depending
on the runner, different amounts of lactic acid in the body will force that
individual to slow down. Phil Davies, a Sports Fitness Advisor, has said on his
website, “It is thought that complete exhaustion occurs somewhere in the range
of 20 – 25 mmol/L for most individuals although values greater than 30 mmol/L
have been recorded.” Why are some people crippled at 20 mmols while others can maintain
their form and confidence to continue? One of the more interesting things I
have been exposed to lately is the idea of pain management. I just finished my
last season of competitive collegiate cross country and I have looked back in
hindsight at races that have been pivotal in my progression as a distance
runner. I remember a 10k I ran during my first college track season where after
running over 5 miles on a track (21 laps) I was able to accelerate my pace into
4:40 range with 4 laps to go. I felt fine during that lap, but WHAM it hit me.
I could feel the accumulation of lactic acid shouting at me to slow down. I
fought it the best I could and kept pushing. I felt as if I was maintaining
that pace, but I realized that I was slowing down slightly. I threw in a final
surge to kick off the last lap and finished that lap in 67 seconds completing
the last 1600 in 4:59.
I remembered thinking after that race that
when I decided to go as fast as I could there was something holding me back.
What I believe now is that during these situations pain management becomes so
important. Through years of workouts and race successes and failures I have
learned that one of the reasons we train is to not only to train our body’s
physiology but also our mental capacity to assure our body, during the race, that we have been
through similar situations of pain and that this race or surge may hurt for a
moment but will be ok.
There is a lactate threshold for all
runners. Some runners can maintain a higher running speed, before lactate starts
to accumulate, than others. It would be said that these individuals had a higher
“lactate threshold” or LT. Lactate threshold is a very important factor for serious
distance runners. When determining one’s lactate threshold a runner’s VO2Max is
taken into account; hence the title to this section “Fractional Utilization of VO2
Max”. According to Tim Gibbons et al of the US Olympic Committee, “The
[lactate turn-point] when expressed as a percentage of V02, is high in the
endurance-trained athlete. In sedentary individuals, for example, the [lactate
turn-point] may be at approximately 50-60% of VO2 max, whereas in
endurance-trained athletes it typically occurs at around 75-90% of VO2 max.”
When the word “turn-point” is said here, it is being identified as the point
when running speed increases slightly but an athlete’s blood lactate readings
jump immensely.
How can you increase your lactate threshold?
Several different sources feel that a trusted way to increase a runner’s
lactate threshold is to run “threshold runs” or runs right next to the point
where lactate begins to accumulate in high amounts. If you ever get a chance to
read Jack Daniel’s Running Formula,
within that book there is a chart which can easily approximate the speed at which training
runs should be accomplished, according to the athlete's VO2Max or current
running ability. To get the best measurement to determine one’s lactate
threshold a set of muscle biopsies or blood pricks would be needed. Due to the difficulty
of this, a heart-rate training procedure can be used to replace these. Heart rate increase
often is closely correlated with increases in blood lactate within the body. By
calibrating a heart rate monitor for each specific athlete, workouts can be
reviewed and can help determine an athlete’s threshold. By training at or
slightly above one’s threshold level constantly, the body adapts and allows runners
to push themselves into higher lactate threshold levels.
Genetics are often pointed to when lactate
threshold is the topic. Several studies have shared their findings that
increases in slow twitched muscle percentages allow for the highest possible
LTs. Alternatively, a study produced by Adèle R. Weston et al. entitled African runners exhibit greater fatigue
resistance, lower lactate accumulation, and higher oxidative enzyme activity, the
researcher shared information which appears to question previous
findings. The results highlighted findings that significantly more active
oxidative enzyme activity (citrate synthase, and others) and longer time until
fatigue was shown in African runners than in performance-matched Caucasian runners.
Ironically the average type 1 muscle ratios were higher in the Caucasian runners who had an average of 67% versus African runners having only 49%. If the
results found in this experiment are true, its implications cause one to consider the need of
high slow muscle ratio for a distance runner.
Threshold training is important for distance
runners. Though I have changed my philosophy of workouts many times since I begun running competitively, I naturally throw in threshold runs weekly because
it makes me feel more powerful, more relaxed at “uncomfortable” paces and
mentally stronger. I am only more and more convinced that there is a very close
correlation between LT and pain management.
This last season of cross country I became
curious about strength training in addition to my running. I would perform
sessions of 30 minutes twice a week throughout most of the season. I did
this mainly after reading the interesting studies about increased performance capability
through changes to the neuromuscular adaptations. These exercises were almost
entirely anaerobic in nature. I ended up doing very well at the end of the
season and while I feel that my key running workouts were what help my body
adapt the most, these strength training routines were excellent times where I
could focus on pain management. In the weight room I am not sure if I was able to
increase the strength of my running muscles in ways to help my body
significantly, but I was able to help my brain/body take on high levels of
pain. This made even the hardest workouts and races bearable.
