Neither Lagat, Rupp, Wheating, or Manzano is running astoundingly high mileage. The reality of US distance running is that you don't make a US team on the track without <50 sec 400m speed.
Solinsky is down under 100/wk average and training faster to spend *less* time on his feet. We know that this is the absolute *most* Solinsky needs to break 13' and 27'.
Ritz broke through by cutting back, realizing he was overtraining. And once he began edging up the volume again, he was back injured.
And even Hall has cut back volume to regain form and go after a faster marathon in Chicago.
Neither Flanagan nor Huddle were doing high volume training when setting US records. Each progressed by finding a way to keep healthy and by training higher quality/ greater specifically. At 1500m our top runners are capable of 2' at 800m. The speed aspect there is inescapable. Our best 800m runners are former 4x400m runners.
At the HS level Fernandez (3200), Webb (mile), Andrews (1000m) all ran their records on remarkably low volume.
Fairly routinely now we have top 3200m runners with moderate volume training (40-50 miles/week)such as what set up the running careers of Solinsky and Kennedy. Hasay topped out at moderate mileage also and wisely backed off when she realize additional training was hindering rather than helping her HS level racing. Chatelet was discovered on a soccer field.
While I don't have time today to explain why moderate volume
good quality training can work better than high volume, the short explanation is that physiological adaptations are not simply due to the duration of training. Pace, consistency, basic speed, nutrition,periodization,specificity of work, and talent also factor into performance capability. There is always more than one way to reach a goal.