A Physiologically Driven Performance Paradigm
Imagine we have two runners, John and Steve. Both John and Steve have a VO2max of 80 ml/kg/min. This VO2max value represents the maximum integrated capacity of their pulmonary, cardiovascular, and muscular system to uptake transport and utilize oxygen. Despite these athletes having identical VO2max values, John beats Steve in a 5k race when they go head to head. How do we reconcile this?
I’ve heard one camp of coaches make the argument that a high VO2max is everything and that the results of races are predetermined before they start. A different camp of coaches asserts that VO2max is meaningless because it can’t predict finishing places among elite runners. In reality, both of these camps are right. If two runners show up to a race and one has a VO2max of 50 ml/kg/min, and the other has a VO2max of 80 ml/kg/min, we can bet that the later will win. But, when two athletes with high, but similar VO2max values race against one another it’s a toss-up. That is, unless we account for other factors outside of VO2max. The reason for this is that VO2max is a functional criterion, not a performance criterion. We need to be careful not to conflate the two. The following example, applied to cars, helps explain the distinction:
The functional criteria of a car establish how much power it’s engine can produce. It says nothing about how far the car can go, how quickly it can go from zero to sixty miles per hour, or how many miles it gets per gallon. These are all performance criteria. Similarly, VO2max tells us something about the maximum integrated capacity of major organ systems, but it doesn’t tell us how exactly an athlete will perform in a foot race. To understand when John beat Steve in the 5,000m footrace, we need to look past VO2max and start to consider specific performance criteria, like critical speed, which represents the fastest pace an individual can sustain before their rate of oxygen utilization outstrips their oxygen supply. This has less to do with the maximal rate of energy turnover and more to do with an individual’s ability to transfer energy into mechanical work. Using the above example, this might mean that both John can sustain a 5:28 mile pace before his oxygen consumption outstrips his oxygen supply, and Steve can only sustain a 5:32 mile pace before the same thing occurs. In this case, John can run at a 5:30 mile pace without depleting his finite oxygen reserves since he is running slower than his critical speed, while Steve depletes himself to hang on.
However, when we’re dealing with the highest level athletes, things can get even more complex. Let’s take another scenario, where we have two runners, Raina and Alexa. Both of these runners have a VO2max of 55 ml/kg/min, and they both have a critical speed of 7:45 per mile. Yet, when they go head to head in a 10k, Raina ends up beating Alexa to the finish line. We know that both runners have the same rate of maximal energy turnover and the same ability to transfer energy into mechanical work, yet one still wins the race while the other loses. This is explained by differences in running economy, which defines their energy expenditure per unit of output. Running economy is calculated as the rate of oxygen consumption for running at a specific submaximal velocity. Improvements in economy allow athletes to run faster for the same oxygen consumption and thus achieve superior performances, like the famous case study on Paula Radcliffe titled, “The Physiology of the World Record Holder for the Women’s Marathon” .
This case report shows that Paula Radcliffs 3000m PR dropped from 9:22 down to 8:36 between the years of 1991 and 1995. Interestingly, her VO2max decreased from 72.8 ml/kg/min to 66.7 ml/kg/mi over that same period. This is attributed to a substantial improvement in her economy, which is demonstrated by the fact that her oxygen cost of running at 16 km/hr dropped from 53 ml/kg/min down to 47 ml/kg/min during that period as well as the fact that her running speed at VO2max went from 19 km/hr upto 20.4 km/hr. This means that over a 5 year period, Paula Radcliff improved her running speed at VO2max and did so while consuming less total oxygen. Going back to the car analogy, this would mean that her engine got smaller, but now produces more power, and has better fuel efficiency. This is akin to trading a 1960’s muscle car for a brand new Tesla.
This ties into my three-tier performance paradigm for work capacity-based sports. Whoever has the highest sustainable rate of energy turnover (the highest VO2max), the greatest ability to transfer energy into mechanical power (highest critical speed / critical power), and the greatest ability to apply power to the task with the most efficiency for the longest duration (greatest economy) wins.
