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The Long Interval

The Long Interval

By Lauren Evans


One of my athletes contacted me after a pretty tough workout, saying this: “Can you please tell me how [the long interval workout] is going to help my marathon time?”


Although the athlete’s question is so simple, it’s right on target. All athletes should have the opportunity to ask their coach how their daily workouts fit into the grander race goal of the season. 


In this article I will share how my athlete’s question was answered in the context of this “long interval workout” (here I will define a long interval workout as a workout containing intervals greater than 3 minutes in length, with longer versions also called a “tempo” or “split tempo”). I hope you can come away with a better understanding of what you may consider the hardest workout of each week. 




My athlete’s particular session was a split tempo session, and it is as follows: 

2 mile warm up 

20 min moderate – hard RPE (rate of perceived exertion)
2 min rest

5 min hard / very hard RPE
2 mile cool down 

Total miles = 8 miles




The lactate system helps to regenerate ATP (energy) rapidly by incompletely breaking down carbohydrate in the body. This occurs when there is not enough oxygen available for aerobic energy production. The lactate system can supply about one minute’s worth of ATP (energy). However, there is a price to paid because when this system becomes the dominant energy source, blood levels of lactate begin to accumulate, causing that familiar ‘burning fatigue’ sensation in muscles.

The aerobic system provides the bulk of our energy requirements by binding fat, carbohydrate, and protein with oxygen to produce ATP. This process is much more efficient because there are little to no toxic byproducts, but the aerobic system takes longer to “kick in” than the lactate system. The incredible benefit of the aerobic system is that, provided there is enough oxygen available to the working muscles, it can provide energy for several hours.




Simply put, the purpose of the long interval session is to challenge your muscles and energy systems to teach your body and mind to adapt to working at increased intensity. The goal is to help you bring about training gains that will not come about with only slow, aerobic-paced running. Additionally, long intervals help you practice running at a sustained, hard pace for a set interval as opposed to the entire training session (in my athlete’s case – 8 miles total), which reduces the risk of injury or illness.

The benefit of interval training in general is that duration and intensity are flexible, so a coach can choose interval duration and intensity to target the athlete’s aerobic system. Specifically, the coach can choose interval duration and intensity levels to perform lactate threshold work if that is the system that needs improvement. The benefit of increasing an athlete’s lactate threshold is that he or she can perform at a faster pace while slowing the buildup of hydrogen ions (which is the toxic byproduct of this work). The buildup of hydrogen ions results in the burning sensation that is commonly called “lactic acid build-up”. Thus, by improving your lactate threshold, you will be working aerobically at a faster pace. In other words, this means a faster marathon time without buildup of hydrogen ions (“lactic acid”) during the race which will essentially bring you to a stop or slow you down significantly. 

Finally, and importantly, long intervals (tempo) sessions help you practice a long, hard, sustained effort = a race! Tempo sessions mimic racing, which is why you often won’t see a tempo session the week you are running a 5 or 10k race, nor up to 2 weeks before a half or full marathon (although there are exceptions). Tempo sessions help you experience what it is going to feel like to race, so you are mentally prepared. The way you mentally prepare for your tempo session should be almost the exact same as how you mentally prepare for a race. Mentally, you know that “you will survive!” and “you can get through it!” It’s a wonderful thing to learn and to keep in your back pocket for race day – the belief and knowledge that you really can do it!


Workout Breakdown


Here is a breakdown of my athlete’s session: 

Action: 2 mile warm up 

Purpose: to gradually warm up muscles, tendons, ligaments; to prepare the body for a hard effort; breathing, heart rate, and perceived effort increase and then level out; to increase daily mileage toward the weekly mileage goal. (Weekly / daily mileage is designed to promote efficiency of your aerobic system (marathon is 98% aerobic), while also increasing strength of ligaments, tendons, muscles and bones to reduce the risk of injury in long efforts. It also serves as a practice for form, helping you to become a more efficient runner.) 

Action: 20 min comfortable hard / hard

Purpose: The athlete is working aerobically, but it is at the limit of his or her aerobic threshold. Breathing is strained as the athlete tries to take in enough oxygen to stay aerobic. This also teaches the athlete that he or she can run at this pace for longer than initially thought. 

Action: 2 min break

Purpose: mentally and physically recover to prepare for the 5 minute interval; this is not enough time for the body to rest and recover carbohydrates and fat to return to the fresh state at the beginning of the workout, but the athlete can recover breathing and mentally prepare for the next increment. 

Action: 5 min hard

Purpose: You thought you couldn’t go any farther at the end of your 20 minute session, but you find out that you can! You have recovered your breathing, so initially you can keep pace with your increase in speed. You are working aerobically until your body cannot keep pace with your speed, so you begin to work anaerobically. You have crossed the threshold. Instead of your body breaking down O2 and fat and carbohydrates to help you move forward, you hit your lactate threshold and begin the incomplete breakdown of carbohydrates. The byproduct of this inefficient breakdown is the “burning fatigue” sensation, often called lactic acid. 

Action: 2 mile cool down 

Purpose: To gradually cool down the muscles, keep hydrogen ions (that have been created as a byproduct of the long intervals) moving through the body; otherwise the ions will accumulate quickly and make the athlete sore. To increases base mileage for the day to help the athlete reach his or her base mileage goal. 




By pushing the athlete to his or her limit, the body will try to adjust to this workout (known as “supercompensation”). With supercompenstaion, the athlete will not reach his or her lactate threshold at the prescribed pace but rather at a harder pace at a point in the future. The result is that the athlete will be able to work aerobically at a faster pace, which translates to a faster marathon time. 

Long interval work has been a staple of nearly all, if not all of the most decorated coaches’ training programs, so be assured that it works! 


Good luck in your training!




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