Over the years, the scientific community has come to recognize various factors that are strongly related to endurance performance. These factors are primarily physiological characteristics and include VO2max, lactate threshold, efficiency/movement economy, and most recently, durability (sometimes referred to as aerobic endurance) (1,2). The determination that these factors relate positively to endurance performance has come about from many decades of lab-based experimental research and field-based observational research. However, any sensible exercise scientist or coach working with athletes will know that overall endurance performance of an athlete is a product of much more than just these four physiological qualities described above.
Physiological development of an endurance athlete is, of course, critical to success. Yet, there are other factors that potentially influence performance as well. Nutritional factors, psychological factors, and health-related factors are just some of the other variables influencing performance. It is difficult to establish some of these as determinants of endurance performance as they have not been focused on in the research literature to quite the same extent as the four physiological variables described above have been. However, a recently published paper dove into this exact topic and aimed to identify the top factors associated with endurance performance via an expert panel. Let’s discuss this paper next!
An Expert Panel to Identify Top Factors Associated with Endurance Performance
A study published in 2022 by Konopka and colleagues in Europe (3) took a list of 120 potential factors that could influence endurance performance and worked it down to 26 factors that 18 international experts agreed upon are associated with high-level endurance performance. These 26 factors are grouped into 5 different cluster groups and are summarized in the image below, which is Table 2 taken directly from this manuscript. The level of agreement from the expert panel had to be between 70-100% for the item to make it onto the final list of factors that are seen below.
As you can see, the four physiological factors that are known to be associated with endurance performance made the list (i.e., VO2max, lactate threshold, efficiency/movement economy [economy of movement], and durability [endurance capacity]). Importantly, however, there are 22 other factors that 18 international experts agreed were associated with endurance performance.
The expert panel organized their factors into the following five categories: physiology, nutrition, injuries, psychology, and fatigue. While all the factors listed in the table above are important, in my opinion, let’s look at some of the ones that had nearly 100% agreement or 100% agreement across the experts in the panel:
Carbohydrate metabolism (100%) and glycolysis capacity (100%)
It is very well-documented that endurance athletes’ success is related to their capacity to oxidize both fat and carbohydrates during exercise, but the capacity to utilize carbohydrates is particularly important as this source of fuel is metabolized quicker than fat during exercise and helps fuel higher-intensity race-day performances in which the demand for energy is needed at a faster rate (4). This becomes even more crucial as the competitiveness level of the athlete increases as so too does the intensity at which they will be racing and, therefore, the rate of demand for energy stores that can be metabolized quickly.
Number of red blood cells (100%) and iron deficiency (94.4%)
Motivation capacity (94.4%)
Sleep quality (94.4%)
What is the Takeaway From All This?
There is quite a lot that can be taken away from this recently published research.
Firstly, I would agree that just about every factor this expert panel decided on as being important to endurance performance. Honestly, there are likely dozens of other factors that are important as well. However, I do understand that this study was trying to get an expert panel consensus on some of the most important factors related to high-level endurance performance. Of the factors they agreed upon, I highlighted a few in the prior section that I thought stood out to me the most as they were modifiable outcomes that athletes can influence through their behaviors.
For example, as mentioned early on, various physiological variables have been established as being critically determinant of endurance performance (i.e., VO2max, lactate threshold, efficiency/movement economy [economy ofmovement], and durability [endurance capacity]), and these factors can all be improved through training. However, the research published herein describes other factors that research should consider studying deeper to determine their power of predicting endurance performance. Things such as sleep, motivation, red blood cell volume, carbohydrate metabolism, and glycolysis capacity are all factors that can be trained and improved upon with the right behavioral approaches. Having more research to suggest which of these factors are most predictive of endurance performance alongside well-established physiological variables would appropriately broaden the list of factors that should be considered important in determining endurance performance capacity. To illustrate the importance of this, in a scenario in which two marathon runners with the exact same physiological profile are competing against each other, which one will end up winning? The critical difference might be in their sleep habits or patterns or their psychological make-up. Knowing and understanding this will help researchers and professionals better define the group of factors that contribute to better endurance performance.
Secondly, as a coach or athlete reading this research, it gives a glimpse into what experts in the endurance sport space think you should be focusing your time and energy on developing. Outside of the basic physiological qualities that we all train for through our physical training, which factors should you also emphasize as a coach working with athletes? Which factors should you focus on bettering if you are an athlete coaching yourself? Maybe dietary intake of iron and red blood cell volume is a consideration for vegan athletes or athletes that don’t consume diverse sources of iron? Maybe improved sleep is a huge area of improvement for an athlete that trains extremely well but that only sleeps 6 hours per night? Or maybe an athlete has an incredible VO2 max, lactate threshold, movement economy, and durability profile, but fails to get the best out of themselves on race day due to lack of motivation?
The research discussed herein and the factors that have been proposed as most crucial in determining high-level endurance performance provides coaches and athletes with a larger list of modifiable factors to target through training, diet, and health behavior changes that will ultimately improve overall endurance performance.
Personally, I hope studies like this pique researcher’s attention so that more factors other than the big four physiological variables are investigated more rigorously to determine their association with endurance performance. If you are a coach or athlete reading this, I hope you can take away some ideas regarding modifiable factors (like sleep, nutrition, psychology) that can be improved to achieve greater endurance performance. Success as an endurance athlete, after all, is about much more than just training to be physically fitter!
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Konopka MJ, Zeegers MP, Solberg PA, Delhaije L, Meeusen R, Ruigrok G, Rietjens G, Sperlich B. Factors associated with high-level endurance performance: An expert consensus derived via the Delphi technique. Plos one. 2022 Dec 27;17(12):e0279492.
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Kuwabara AM, Tenforde AS, Finnoff JT, Fredericson M. Iron deficiency in athletes: A narrative review. PM&R. 2022 May;14(5):620-42.
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Happy training and racing!
-Ryan Eckert, MS, CSCS
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