In order to separate and clarify the elements of breakthrough marathon performance we need to acknowledge some of the most widespread problems. Too much dependency on 'quantitative' long runs and generic tempo runs, for example, rather than 'qualitative' hill workouts, 5K & 10K paced sessions & speed-strength circuits designed to complement those essential longer efforts. By supervising these higher intensity exertions carefully, I see them have a much broader impact on V02 max and lactate threshold, key physiological variables that effect endurance running success.
A recently published report from the website RunRepeat.com found that American road race results are slower than ever before. The report looked at more than 34 million U.S. road race results between 1996 and 2016, the largest analysis of its kind. The only ones not getting slower are the top elite runners.
Scientists have a pretty clear picture of what happens when summer sunlight, high air temperatures and/or humidity increase both skin and core temperatures in runners who increase their mileage training for a fall marathon or cyclists and triathletes preparing for autumn events. They bake. Muscles in motion generate enormous amounts of energy, only about 25 percent of which is used in contractions. The other 75 percent or so becomes body heat. Yet why someone has more difficulty dissipating body heat on one hot afternoon’s run than on another is still mysterious.