Factors to Measure Endurance Performance in Marathon Runners

The current world record for running a marathon is 2 hours, 1 minute, and 39 seconds. To achieve this, it requires a steady rate of oxygen consumption and the ability to sustain this 80-90% of VO2 max for over 2 hours. Although we usually look at VO2 max for runners as a preliminary measure of the aerobic capacity of an athlete, there are other factors that contribute to performance as well. At the tissue level, factors such as capillary density, mitochondrial size, and muscle fiber type can all play a role in endurance performance. These intrinsic qualities influence a muscle’s capacity to sustain a high level of aerobic exercise and can be the deciding factor in an athlete’s ability to put on the performance of a lifetime.

Below is a list of factors that contribute to endurance performance and a bit of information about what they are and how they impact performance:

1. VO2 max

VO2 Max is the fundamental measure of a physiologic functional capacity for exercise. The output shows the integration of high levels of pulmonary, cardiovascular, and neuromuscular functions and provides information about long-term energy systems.

There are a number of exercise tests that can help determine an individual’s VO2 Max, with typical modalities including treadmill running, stationary cycling, and bench stepping. By activating large muscle groups of the body, we are able to get a better picture of how the body is adapting to exercise. The testing typically requires a single, continuous 3-5 minute bout of supramaximal efforts to push your body to the limits and ensure that a maximal value is achieved. Subjects are taken through progressively more difficult increments of exercise until their body gives out and they quit the exercise protocol – the point of exhaustion.

VO2 Max is influenced by a number of different factors including an individual’s gender, body size, body composition, age, and their state of training. A higher level athlete will typically see a higher VO2 Max, which will ultimately play a role in their ability to perform in endurance events.

2. Running Economy

Taking it to the next step, running economy is the measure of how well you can translate your body’s natural VO2 Max into results. Assessing running economy requires an evaluation of the amount of oxygen consumed during exercise at a constant power output or velocity and will closely mirror energy expenditure. Ideally an athlete is looking to maintain a low oxygen consumption at any given work rate. There is strong association between running economy and endurance performance in elite athletes of comparable aerobic fitness. Those athletes with a better running economy will tend towards having better race times when compared with athletes of comparable aerobic capacity.

Running economy can be influenced by a number of different factors including biomechanics, neuromuscular efficiency, cardiovascular efficiency, an individual’s training history, and overall metabolic efficiency. Improvements in any of these areas can lead to better running economy and, through that, better results in your endurance runs.

3. Anaerobic Threshold

Rapid and large accumulation of blood lactate occurs during maximal exercise. The lactate threshold describes the highest oxygen consumption or exercise intensity achieved with less than a 1 millimole increase in blood lactate concentration above the pre-exercise level. Lactate production and accumulation accelerate as exercise intensity increases. In such cases, the muscle cells can neither meet the additional energy demands aerobically nor oxidize lactate at its rate of formation. A similar pattern exists for untrained subjects and endurance athletes, except the threshold for lactate buildup, termed the blood lactate threshold, occurs at a higher percentage of the athlete’s aerobic capacity. Trained endurance athletes perform steady-rate aerobic exercise at intensities between 80 and 90% of maximum capacity for aerobic metabolism. This favorable aerobic response most likely relates to three factors:

1. Athletes’ specific genetic endowment (e.g., muscle fiber type, muscle blood flow responsiveness)
2. Specific local training adaptations that favor less lactate production
3. More rapid rate of lactate removal (greater lactate turnover and/or conversion) at any exercise intensity