We have all seen the pros who detail their twice-daily runs during +100 mile weeks. When does it make sense for us amateurs to run twice a day?

This question often comes up in marathon training, especially during the later stages when mileage is high. The short answer is to Be Careful about adding twice-daily workouts. Additional mileage will help your fitness, but only if approached responsibly. The pros have spent years building an aerobic base of running miles.  

Before running twice a day, try increasing your weekly mileage in these other ways. These miles should be easy runs that leave you feeling recovered and fresh for upcoming workouts. 

• If you are not running seven days a week, add another day of running. Take a day off every 14 or 21 days as needed.  
• Add 1-2 miles to the warmup and cooldown before workout days. If you are doing three quality sessions per week, this translates to 6-12 extra weekly miles. 
• Add another long-run per week. If you are running +2 hours on the weekend, try to run another 2-hour run during the week. 
• Add 2-3 miles to your weekly long-run. This option is the least preferred of the above methods because you run the risk of loading too many weekly miles into one run. 

After trying the above options, running twice a day may be a good idea if you need more mileage or time. For instance, twice a day runs are more commonly prescribed when running +70 miles per week. Sometimes, it is easier to carve out two 1-hour training blocks versus one 2-hour training block. 

If you decide to double, be careful about when you double: 

• Start by adding a second 30-minute easy run the same day as hard workouts. These are already hard days, so you can make them a little harder versus making an easy day more challenging. 
• Next, add a second run to another easy day, preferably one not before a workout day. 
• Try to avoid doubling the day of long-runs. Mentally, this will keep you focused on executing the critical long-run well. 
• In all cases, the second run should be easy. It should be focused on recovery and ran at a comfortable pace. 

Best wishes on chasing your running goals!