I've been reading through a lot of 2:30 marathon training threads on LetsRun, and what strikes me is how many "easy" runs these guys are doing to hit their 80-100 mpw targets. I've been conditioned to think of this a "junk" mileage over the years since transitioning from a pure runner to a triathlete.
My limiter is cycling. I'm a strong swimmer and runner (though don't run to my potential in tris due to bike weakness). Would I benefit for doing lots of easy rides? For example, I could, theoretically, do an easy 30-45 min trainer spin every evening while my kid sleeps and wife does more work. And/or I could bike commute to work (about 30 min each way) a few times a week. Would there be any training benefit? A waste of time? Or worse, counter productive by detracting from my "key" sessions? If I add these extra base mileage rides, anything else to keep in mind?
My typical weekly schedule looks something like this, with key workouts in early morning:
M) Swim: Speed + Technique AM, "Prehab" PT/Strength PM
Tu) Hard run (hills or track)
W) Hard ride, optional brick run off time permitting
Th) Swim focus: Long/endurance swim, optional brick or PM run, time permitting
F) Long run
Sat) Long ride w/ mandatory brick run
Sun) Family day (which usually includes a light-moderate hike with our 1yo son on my back)
So with the framework above, I figure I could conceivably add some low Z2 riding Mon, Tues, Fri at a minimum and maybe also a 2nd Wed ride.
I comment on these types of questions a lot because my training observations are entirely at odds with the current recommendations. I've been listening to a lot of top coaches discuss volume and intensity, both in podcasts and in youtube videos. Without having hard numbers from which to pull, they usually estimate that their athletes are between 85 and 95% easy (aka, junk) efforts. These are mainly olympic tri distance coaches.
This is utterly baffling to me. First, my ~10 years of garmin data robustly confirms that when I start chasing distance or time-spent as a metric for prescribing my sessions, my performance plummets, both in the run and on the bike (swimming, not so sure). I can give hard numbers as examples, for context if anyone is interested, but suffice it to say, I'm not back or middle of the pack. Second, endurance performance is bounded by two primary variables: VO2 max and the percent of VO2 max that you can maintain for the duration of the effort. It's not disputable that higher intensity training produces more robust stimuli for both of those factors. In other words, run for 30min easy or hard; the hard effort will product the greatest stimulus for acclimation. So what is the mechanism whereby easy efforts contribute to enhanced performance? It's not enhanced fat metabolism; our capacity for peripheral lipolysis already exceeds our capacity to deliver it to the muscles. My best guess (and what seems to be suggested by these coaches) is that it's a compromise: predominantly high intensity efforts are largely unsustainable from a psychological and physiological platform. And if you have burned-out or sick athletes, those are non-exercising athletes. So the next best thing is to pile on tons of volume, sprinkle in some intensity, and keep everyone healthy and exercising. There's plenty of published observational data to suggest that this approach works, but to my knowledge, no one has even proposed a mechanism attempting to explain the direct superiority of easy vs hard.
Honestly, every time I get sucked back into focusing on miles and time (like I am now), my FTP and 10k just absolutely crash. It's so demoralizing. My best run performances have come from less than 10 training miles per week and my highest FTP has come from doing nothing but 1- and 3-min intervals a few times per week, which ends up being the equivalent of less than 25 miles and maybe two hours of riding. I don't know. Volume doesn't work for me, but here I am, trying it again.