The Medium-Long Run: A Triathlete's Secret Weapon

The utility of the medium-long run lies in its addressing several components of endurance at once. Any run lasting between 90 minutes and two hours is long enough to stimulate physiological adaptations that do not occur to an appreciable extent in shorter efforts, yet not so long as to prolong recovery. Also, the distance of such runs – commonly 10 to 15 miles, depending on a runner's speed, training load and experience – allows for the integration of a variety of intensities that long runs do not and durations that “normal” (shorter) runs do not. The MLR, therefore, is a strong ally owing as much to its flexibility as to its distance. 

Three Types of MLRs 

As with long runs, it is convenient to separate MLRs into three categories. Each serves a distinct purpose and skimping on any one of them will deprive you of the full range of benefits that the MLR offers. 

Steady-state. These runs are basically everyday runs sustained for an extra 30 to 60 minutes. They aren't recovery runs, but they aren't hard and should not require special recovery. A target heart rate of 75 percent to 80 percent of maximum (representing about 70 percent to 75 percent of maximal oxygen uptake) is desirable. In warmer weather, be sure to start taking in fluids early on, and don't skimp on carbohydrates in the latter stages and immediately after finishing. 

Well-trained athletes can get a little extra bang by doing these runs on hilly courses, although care should be taken not to pound the downhills too enthusiastically. 

Tempo. The tempo run – known to some as a lactate threshold (LT) or an anaerobic threshold (AT) run – has become a staple among distance runners since Jack Daniels coined the term about a quarter of a century ago. The term is used in a variety of ways, but strictly speaking, threshold effort is that which a well-conditioned runner can maintain for approximately an hour under optimal race conditions. So for most people, tempo pace lies between 10K race pace and 10-mile race pace. 

Daniels' original recommendation for the masses was tempo runs of 20 minutes or so, but true endurance athletes, such as marathoners and triathletes, can absorb more stress and hence benefit from longer tempo runs. Therefore, LT stretches lasting as long as about 40 to 45 minutes can be worked into MLRs, either at the end or in the middle. 

Fast finish. As with long runs, it can be useful on occasion to run the first 85 percent to 90 percent of an MLR at the usual pace, then pick up the pace in the last 10 to 15 minutes in a progressive manner, starting this process at roughly tempo-run pace and winding up at 10K pace or even faster in the last few minutes. This challenge recruits both types of endurance-happy muscle fibers (slow oxidative and slow glycolytic) when each has already been significantly taxed but not exhausted, owing to the run's basic duration. The result is a training stimulus not available in either shorter or longer runs. 

Pfitzinger cautions against going overboard with the fast-finish MLRs, even if you feel fantastic. There can be a fine line between incurring a level of fatigue that generates a considerable training stimulus without needing days of recovery and hammering yourself so strongly that the aftereffects are more race-like than training-like. One lesson few endurance athletes fail to learn in their competitive lifetimes is that gauging how much more your legs can take when you’re already 90-plus minutes into a run is very tricky, and it’s best to not have to find that out the hard way. 

As with the other types of MLRs, these can be accommodated once every three weeks or so. 

Putting It All Together 

Here is a sample MLR schedule for a 3:30 marathoner. Athletes who do their long runs on Sunday morning are advised to do their MLR on Tuesday afternoon or Wednesday morning, which allows for one additional intense session on Friday. In any event, a rest period of 60 to 72 hours between an athlete's longest two runs of the week is optimal. 

Also, Pfitzinger recommends that more seasoned athletes incorporate MLRs done right off the bike. If you opt for this route, stick with doing this “brick” on days when your MLR doesn't include either tempo or fast-finish portions, at least in the beginning.