Author: Christina Ramirez, PT, DPT
I have run three marathons to date, and multiple half marathons. At first, my goal was just to finish the races without getting injured, but during my latest marathon, I set a time goal. I decided that the best way to beat my past times was to train more on hills and include intervals in my training process. I ran my latest marathon in January and surpassed my two previous marathon times by forty minutes! While I do feel training on hills gave me an advantage, I would attribute most of the credit for my improved time to interval training.
While I was training, I decided my goal time was to run the marathon in five hours. When I researched the duration of interval splits I should run, I found most programs agreed a 4 minute run with a 1 minute walk would land me on the finish line at 5 hours. As I stated before, I beat my past records by 40 minutes which meant I ran my latest marathon in 4 hours and 35 minutes! I originally tried interval running because of anecdotal evidence, but after I improved my marathon completion time, I wanted to see what current research had to say about interval running.
In an article by Franch et. al., the authors found that VO2 max (the amount of oxygen one can intake at a given moment), the time to exhaustion, and running economy (the aerobic cost for a given rate or distance) were all improved with running. VO2 max improved the most with long-interval training (LIT) defined as running for 4 mins and pausing for 2 minutes for a total of 20-30 minutes. Time to exhaustion improved the most with continuous distance running (DT) defined as running non-stop for 20-30 minutes at about 65% of heart rate max. Running economy improved most with LIT and DT both. Short interval training (SIT) defined as 15 second run followed by 15 second pause for a total of 20-30 minutes improved in all measures, but not as much as LIT and DT. It is important to keep in mind that the participants in this study were on average 30.4 years old and had been recreational runners for more than 2 years before joining this study.
Another article I found stated the claim that high-intensity interval running is more enjoyable than moderately intense continuous running. Bartlett et al asked eight men, who were known to recreationally run, if they perceived more fun running for 50 minutes at 3 minute intervals of varying VO2 max with a warm up and cool down, or running for 50 minutes at 70% VO2 max. The results showed the participants enjoyed running with set intervals more than continuous running. The authors used the results to hypothesize that runners may be more compliant with running as an exercise or a training schedule if they run in set intervals and enjoy the activity more. One limit to this study could be the subject pool size.
Based on the above article along with my own personal experience, I believe my marathon completion time was improved due in part to me adding interval training to my marathon training routine. Based on the article by Fanch et. al., by adding interval running to my training, I may have caused my VO2 max to improve, my aerobic cost (running economy) to improve, and my time to exhaustion to improve. The results of the above studies however, must be read with reservation due to the population studied and the size of the population studied.
If you want to improve your marathon completion time in the future, I would suggest try adding long-interval running to your training, but keep in mind the results of these studies should only be applied to current moderately trained recreational runners. If you develop any injuries while training for your future marathon, make sure to see a physical therapist to diagnosis your injury and help you get back to running.
Franch, J., Madsen, K., Djurhuus, M. S., & Pedersen, P. K. (1998). Improved running economy following intensified training correlates with reduced ventilatory demands. Medicine& Science in Sports & Exercise,30(8), 1250-1256. doi:10.1097/00005768-199808000-00011