Interesting study titled "World-Class Long-Distance Running Performances Are Best Predicted by Volume of Easy Runs and Deliberate Practice of Short-Interval and Tempo Runs" and completed by Arturo Casado, Brian Hanley, Jordan Santos-Concejero, and Luis M. Ruiz-Perez was recently and released and is available below.
Some of they key findings are that among 85 athletes (world-class to competitive national standard level, including Wilson Kipsang it seems), the key factors corelating with performance were total volume, volume of easy runs, volume of tempo runs and short interval training. Interestingly long intervals (1000m+ @92-95% HRmax) did not correlate. Additionally, performance was evaluated 3, 5 and 7 years from the start of deliberate training and with every period, the importance of tempo runs steadily increased.
Quote from the study: "One key finding of this study was that some forms of DP training (tempo running and short-interval training) had large correlations with performance scores after 3, 5, and 7 years of systematic training (Table 2). Tempo runs were the most important predictor within the DP activities, agreeing with Tjelta (37) on the relevance of this kind of training, particularly with regard to improving LA (4). Over the course of their careers, the relevance of tempo runs seemed to increase, highlighting the importance of progressive specialization from the most fundamental training sessions (easy runs) to those most specific to long distance racing (tempo runs)" For reference Tjelta is Norwegian excercise scientist who released work on H. Ingebrigtsen preparation before becoming 2012 European champion and 5th at Olympics. He is also the one who performs threshold test on Jakob in Team Ingebrigtsen episodes and seems to be proponent of high volume and tempo training which is something that Ingebrigtsens seem to use very successfully.
Discus.