Got the time? Go the distance. 

Lots of free time and/or a flexible schedule can create the perfect environment for training by mileage. This is true, provided you’re a disciplined athlete, when it comes to running the appropriate pace and effort for the day’s workout. But therein lies the pitfall. In order to complete the prescribed workout, there may be some temptation to run slightly too hard to save time. The busier your life, the more likely you’ll fall prey to this problem. You’ll run moderately hard on your easy days and end up in the metabolic gray zone for too much of your weekly volume. That low zone-3 heart rate builds up a state of acidosis in the system and is stressful to the body without much adaptation benefit. 

Keep your easy days easy and your hard days hard. Eighty percent of your weekly volume should be easy (under your aerobic threshold). 

Time is of the essence. 

Most runners will benefit the most from training by time — at least during the work week. If you're supposed to run a 60-minute easy run, the mileage you cover doesn’t matter. If you're tired, run slower. Feeling spry that day? Cover a little more distance. Running by time will encourage you to go more by feel and stick to the prescribed effort for that day’s workout. 

Every run should have a focus — whether it’s a recovery run, an easy run, or tempo. Know the purpose of the workout and train at the appropriate effort level. When you train by time, you don’t stress about the mileage so much. You just put in the time and let the weekly mileage total fall where it may. 

When training for trail or mountain running, training by time becomes even more important. A 10K trail run with 2,000 feet of climbing in technical mountain terrain is different from a 10K rolling buffed-out singletrack trail run. I sometimes recommend that seasoned runners with flexible schedules and proven discipline train by mileage. However, I suggest most runners train by time (I include myself in this category). 

Exception to the rule. 

There’s an exception to the run-by-time rule, and that’s the long run. Once you’re training actively for events and adventures, shift your long run to mileage and keep all of your other maintenance running throughout the week by time. This will ensure you are covering the appropriate distance of your upcoming goal run and give you confidence knowing you’ve done the work. 

In the off-season, when runners encounter more varied and challenging conditions (like rain, sleet, and snow), it’s a good strategy to train by time. If you're a trail runner, you know that those conditions can vary wildly. Take a deep breath, put away your GPS stats, and enjoy the journey.  

Giddyup! 

About the Author 

Jeff Browning is a veteran ultrarunner and ultra-endurance coach. As a masters athlete, he has embraced both mobility and strength consistently in his training to slow down aging and to prepare his body for the rigors of up to five 100-milers per season—some just weeks apart. You can learn more about him, his adventures, and his coaching at GoBroncoBilly.com or on Instagram: @GoBroncoBilly