Chasing Pheidippides

Chasing Pheidippides: Marathon Training 101

From the time ancient Greek runner Pheidippides ran from Marathon to Athens in 490 B.C. to announce the Greek victory in the Battle of Marathon, mankind has held a compelling interest in endurance. With nearly 400 marathons in the U.S. each year (more than a dozen in San Diego County alone) and nearly half-a-million runners, it is an understatement to suggest that running a marathon is a big deal; once the realm of elite athletes, the average age of marathon finishers is 40 for men and 36 for women.  So in a quest to cross the finish line and quite possibly chase Pheidippides in the process, how does one actually train for a marathon?


The number of miles you run each week is the most important part of marathon training because of how it improves your aerobic fitness. More specifically, running many miles: improves blood vessels’ oxygen-carrying capability by increasing the number of red blood cells and hemoglobin, increases the use of intramuscular fat to spare your limited store of carbohydrates (glycogen), creates a greater capillary network around your muscle fibers so oxygen can diffuse more quickly into the muscles, and increases the number of mitochondria (aerobic factories) in your muscles – thus increasing your aerobic endurance.

Long Runs

Long runs in excess of two hours deplete the supply of glycogen in muscles, which stimulates greater storage (and thus increases endurance) as running out of fuel is threatening to the muscles’ survival. Long runs also prepare muscles and tendons to handle the stress of pounding the pavement for 26 miles, increase muscle ability to effectively use fat once they run out of carbohydrates, and callous you psychologically for running long periods of time.

Lactate Threshold Runs

The lactate threshold (LT) demarcates the transition between aerobic running and running that includes a significant oxygen-independent (anaerobic) component. The LT is an important determinant of marathon performance because it represents the fastest speed you can sustain aerobically. The goal of marathon training is to increase your LT pace and your ability to sustain as high of a fraction of your LT as possible.

VO2max Intervals

VO2max is the maximum volume of oxygen your muscles consume per minute and is largely dictated by your heart’s ability to pump blood and oxygen to the working muscles. Interval training (3 to 5 minute periods of hard running with 2 to 4 minute recovery periods) run at the speed at which VO2max occurs is the most potent stimulus for improving VO2max because you repeatedly reach your maximum stroke volume (the volume of blood the heart pumps per beat), cardiac output (the volume of blood the heart pumps per minute), and VO2max during the hard running periods. The higher your VO2max, the higher your aerobic ceiling.

Dr. Jason Karp is a nationally-recognized speaker, writer, exercise physiologist, and owner of, a state-of-the-science running, coaching and personal training company.  He holds a Ph.D. in exercise physiology and is founder and coach of REVO2LT Running TeamÔ and Dr. Karp’s Run-Fit Boot Camp in San Diego

Injury-Free Marathon Training Tips

Increase mileage by no more than 1 mile/day/week.  If you currently run 20 miles in 4 days/week, run no more than 24 miles next week by adding 1 mile to each of the 4 days. Do not run 24 miles next week by adding all 4 miles to only 1 day of running. Trained runners can get away with adding more miles more quickly, especially if they have experience running more miles.

Run same mileage for 3-4 weeks before increasing it. Give legs a chance to adapt to each level of running before increasing the level. 

Back off training by about 1/3 for 1 recovery week before increasing training load. If you have been running 30 miles/week for 3 weeks, back off to 20 miles for 1 week before increasing above 30 miles for next week.   

Never increase volume and intensity at the same time. When you begin to include speedwork, either drop overall mileage for the week or maintain mileage from where it was prior to adding speedwork. Never add more miles to the week at the same time as introducing speedwork.

Get adequate recovery. All adaptations from training occur during recovery from training, not during training itself. The older you are, the more time you need to recover from training, so the longer you need before increasing volume and intensity.