Marathon performance: durable enough for the long run?

Deeper analysis

With an understanding of the overall approach to the study, let’s take a deeper look at the testing protocols. Each incremental exercise test was performed on a treadmill. The subjects started at around 70% of predicted marathon speed. They performed 4-minute stages until subjects could no longer maintain the designated pace or declined to continue. The speed of the treadmill was increased by 1 kilometer per hour after each stage. Throughout the test, pulmonary gas exchange data were collected to assess oxygen uptake. Blood lactate samples were collected 20 seconds after the end of each stage. Heart rate was recorded throughout the duration of the test.

Following the test, gas exchange data was analyzed to determine the maximal oxygen uptake. The lactate threshold was calculated using the lactate measurements in relationship to the corresponding treadmill speed when those measurements were taken. The speed at which the lactate threshold occurred was then used for the 90-minute run performed during the second testing session. This testing session was identical to the first one, with the only exception being the performance of this 90-minute run and a 5-minute recovery period prior to the second incremental exercise test. The same data were collected during the 2nd incremental exercise test as the first.

During the 90-minute run, from 3-15 min, 25–30 min, 55–60 min and 85–90 min, gas exchange data were recorded. Lactate samples were collected at the beginning of the test and every 30 minutes thereafter. Running economy was calculated by comparing the oxygen consumption to the running speed. Since this 90-minute run was performed at the same speed, comparing the oxygen cost at the 15-minute and 90-minute marks allowed the researchers to assess any loss of running efficiency over the course of the 90-minute run.

The researchers also calculated the fractional utilization of oxygen uptake at lactate threshold. In other words, they determined what percentage of the maximal oxygen uptake was used when running at the lactate threshold speed. This value was calculated at 15 minutes of the 90-minute trial and at the end. An increase in this percentage would indicate that an exercise had become more difficult, despite the constant speed. This in turn would imply a loss of physiological function. In addition, energy expenditure throughout the trial was determined, as were the carbohydrate and fat oxidation rates. These rates were derived from the gas exchange measurements. On the actual race day, marathon performance was assessed using the subjects’ personal GPS-enable devices, whether a HR monitor, phone, or watch. Heart rate data and racing speeds were taken and analyzed.

What they found

When all the testing was done, and the marathons run, the researcher ran the numbers and discovered some interesting findings:

·        Firstly, there were significant changes in physiological function following the 90-minute run at lactate threshold. Peak VO2 was significantly decreased, as was the calculated speed at lactate threshold (see figure 2). Further, the oxygen uptake while running at threshold was also decreased. These findings indicate significant deterioration of metabolic capacities following the 90-minute run.

·        Secondly, during the 90-minute run, there was no significant change in running economy, indicating that this measure of marathon performance was sufficiently robust to resist any negative changes following 90 minutes at lactate threshold. The fractional utilization of oxygen uptake at lactate threshold also remained unchanged, likely due to decreases in both maximal uptake and actual uptake during the run.

·        Thirdly, a runner’s VO2 peak was significantly correlated with his or her marathon performance, as were running economy and the speed at lactate threshold. These findings are not surprising as they have been consistently shown to relate to endurance performance.

·        Finally (and particularly relevant), the subjects that experienced the smallest decrease in the predicted speed at lactate threshold from pre-test to post-test ran the fastest. This indicates that the ability to maintain physiological function under pressure is directly related to marathon performance. In plain English, having a high physiological baseline is important for performance, but maintaining that baseline as much as possible may be just as important!

Figure 2: Changes in key performance parameters pre/post the 90-minute run

Practical implications for runners

The value of this study is that it directly related physiological parameters to actual race performances, rather than time trials or other laboratory tests. However, while this work confirmed the findings of previous studies in terms of the key physiological determinants (VO2peak, economy, lactate threshold), it also presented evidence that the maintenance of lactate threshold is important for marathon performance.  A key focus of training should therefore be focused on not just elevating these key drivers of performance but ensuring that they can be maintained throughout a performance as well.

While this study was performed specifically in runners, the same principles likely apply across all endurance racing.  The longer the race, the more likely that physiological durability becomes relevant. For all extended endurance events, improving durability is an important component of preparation. While training strategies for developing durability have not been thoroughly studied, the testing protocols in this study indicate potentially effective options.

One of the foundational concepts in training is the specific adaptation principle. Given that the 90-minute testing protocol at a hard intensity was sufficient to induce physiological deterioration (indicating less then optimal durability), it’s likely that exposure to similar training bouts will encourage the body to adapt to those demands and become more durable. It’s likely too that even longer training sessions (120+ minutes) involving lower to moderate intensities are also likely to help develop a more durable endurance physiology. With that concept in mind, it then becomes possible to start designing athlete- and sport-relevant protocols for improving durability.

References

1. J Sport Sci. 2025 Nov;25(11):e70073. doi: 10.1002/ejsc.70073