I attended a high school that was known for its swimmers. They were the best in the country, and some of them competed in the Olympics. Before championship meets, you could overhear amusing discussions in the hallways about "shaving down" and "tapering" in an attempt to swim faster. As a member of the cross-country and track teams, I was also interested in getting faster. So I couldn't help but eavesdrop. "What were these odd-sounding things," I wondered. "Could they work for me, too? Do swimmers have a secret?"

The idea of progressively reducing, or tapering, the training load has been a long tradition among swimmers, the most often- studied athletes in regard to tapering. While it is not necessary as a runner to shave all of your body hair to run faster, you may benefit from tapering your training. Since most marathoners, either by training or by nature, are a driven bunch, it seems unnatural to cut your weekly mileage to a fraction of your current training. Competitive marathoners think they should always do more. But that is one of the most interesting things about fitness--the adaptations to training occur during the recovery periods from the training, not during the training itself.

The positive physiological adaptation to training is the result of a correctly timed alternation between stress and recovery. Following a training stress, your body adapts and physiologically overcompensates so that the same stress, if reintroduced, does not cause the same degree of physiological disruption. In short, your fitness has improved. When you taper your training, you provide your body the opportunity to recover, adapt, and overcompensate to the training you have done so you are prepared to run your best race.

Performance Effects of Tapering

Most research on runners, swimmers, and cyclists has shown that improved performance (from 0.5 to 6 percent) is more likely to occur after a period of tapering. Studies on runners have been limited to 800-meter performance, time to fatigue on a treadmill at 1,500-meter race pace, 5K performance, and treadmill half-marathon performance. As with any type of training, these studies have shown a large individual response to tapering. One study using 800 meters and another study using a treadmill half-marathon as the performance measure found that while tapering had a positive effect on selected physiological parameters, it did not have an effect on performance. Regarding the latter study, it is possible that racing two half-marathons only a week apart precluded the runners from improving in the second one. Possibly for the same reason, no studies have examined the effects of a taper on marathon performance.

Physiological Effects of Tapering

There are a number of physiological changes that occur during the taper period. Among the most prominent are changes in the characteristics of the blood, including increases in red blood cell volume, total blood volume, and reticulocytes (immature red blood cells), and improvements in the health of red blood cells. These hematological changes reflect a positive balance between hemolyis (the degradation of red blood cells) and erythropoiesis (the production of red blood cells), leading to a greater oxygen carrying capability and, often, an improved performance.

Tapering also increases muscle glycogen content (giving you more fuel), aerobic enzyme activity (allowing for greater aerobic metabolism), and muscular strength and power, and increases or maintains maximum oxygen consumption (VO2max). A decreased level of creatine kinase in the blood (an indirect indicator of muscle damage), which reflects an increased recovery, has also been consistently found following a taper.

Although no studies have examined the effects of tapering following different volumes of training, it is likely that the more running you do prior to the taper, the more you will benefit from the taper. For example, if you run 80 miles a week prior to tapering, chances are you will reap a greater benefit from your taper than if you run 30 miles a week prior to tapering.

Taper Duration

The goal of tapering is to recover from prior training without compromising your previous training adaptations. In other words, you want to decrease fatigue without losing fitness. Unfortunately, research has not clearly established the time frame separating the benefits of a successful taper from the negative consequences of insufficient training, leaving most athletes and coaches to take a trial and error approach. Since studies on tapering in runners have only used one-week tapers and have not examined the taper's effects on long-distance running performance, it is difficult to speculate whether one week is ideal for the marathon. Typically, the longer the race, the longer the taper, so you should probably taper for two to three weeks before your marathon. The exact duration of your taper will vary depending on your prior training load, your level of fatigue, and your genetically-predetermined ability to retain your training effects while reducing the training stimulus (i.e., how quickly you lose fitness). Obviously, if you tend to fall out of shape fast, you don't want a long taper. Positive physiological adaptations and performance gains have been found using tapers lasting six to seven days in college- aged runners, four to 14 days in cyclists and triathletes, and ten days in strength-trained athletes. Masters runners (over age 40) who take longer to recover from hard training may need to taper for longer than one week. A study on female swimmers published in the Journal of Swimming Research in 1998 found that two weeks seems to be the longest time to receive the benefits of a taper before detraining begins, although tapers lasting up to 35 days have been shown to be effective in swimmers. Given that technique plays a greater role in swimming compared to running, swimmers may be able to get away with a longer taper since technique will likely not deteriorate at as fast a rate as physiological variables.

Taper Volume and Intensity Every high school track coach in the country knows that the fastest way to get his or her athletes in shape is interval training. Research has shown that, to improve or maintain fitness, the intensity of training is more important than either the volume (i.e., weekly mileage) or the frequency (i.e., number of days per week). This seems to also be the case when tapering.

You can reduce your weekly mileage dramatically during the taper as long as you keep the intensity high. Reductions in mileage of up to 60 to 90 percent have been found to be beneficial during the taper period. For example, a study published in the Journal of Applied Physiology in 1992 found that college middle-distance runners significantly improved treadmill time to fatigue at 1,500-meter race pace and increased blood volume, aerobic enzyme activity, and muscle glycogen concentration when using a one-week, low volume/high intensity taper (85 percent reduction in mileage and 5x500 meters at 800-meter race pace with six to seven minutes recovery, decreasing by one repetition each day for five days), but not when using either a moderate-volume/low-intensity taper (six miles at 60 percent VO2max, decreasing by 1.25 miles each day for five days) or a taper with no running at all. Other studies have also found that a large reduction in volume accompanied by an increase or maintenance in intensity improves training-induced adaptations. A study published in Dynamic Medicine in 2005 found that competitive cyclists who underwent a seven-day taper that included a 50 percent reduction in weekly training volume significantly decreased muscle oxygenation (meaning a greater use of oxygen) in the quadriceps during a 20-km time trial and significantly improved their time trial performance. Comparatively, cyclists who underwent a taper that included a 30 or 80 percent reduction in weekly training volume did not significantly improve oxygen use or time trial performance.

Using a mathematical modeling approach, a study published in Medicine and Science in Sports and Exercise in 2005 found that training volume should be reduced in a progressive (linear or exponential) manner rather than by a single step reduction. Furthermore, overload training (i.e., a daily training load greater than the optimal level) prior to the taper would result in a better performance post-taper than if overload training did not precede the taper. The researchers concluded that the best performance would be achieved with a 39 percent reduction in training load for 28 days. If overload training does not precede the taper, the best performance would be achieved with a smaller reduction of training for a shorter period (31 percent reduction for 19 days). Another study using both mathematical and experimental approaches published in the European Journal of Applied Physiology in 1999 also found that an exponential taper was better than a step- reduction taper and that a fast exponential taper was better than a slow exponential taper. In other words, reducing your training quickly and exponentially is better than reducing it slowly and in a single step.

Practical Applications

You can probably expect to improve your marathon performance by reducing your weekly mileage exponentially for two to four weeks and including interval training (if you have already been doing so pre-taper) to maintain training intensity. As you get closer to the marathon, also reduce the "volume of intensity" by reducing the number of intervals in each session. Although research has shown that reductions in training volume up to 60 to 90 percent can improve performance, the research is limited to much shorter races that are not as "endurance-dependent" as the marathon. Given the length of the marathon, and thus its large dependence on aerobic capacity, it is probably better not to decrease mileage by as much as 90 percent.

I typically begin cutting my athletes' mileage and the length of their long runs three weeks before the marathon (or up to a week later if they have not been running high mileage). I reduce peak mileage by 30 percent for the first week, 50 percent for the second week, and 65 percent for the week of the marathon (not counting the marathon itself). I keep the intensity high during the first week, including one interval workout at 3K race pace and one moderately-long run (13-15 miles) with slightly less than half at lactate threshold pace (about 15-20 seconds per mile faster than marathon race pace for highly trained runners). I begin to decrease the intensity slightly during the second week, including two short- to medium- distance runs (5-10 miles) at marathon race pace.

The week of the race, I include one interval workout early in the week at either lactate threshold pace or slightly faster, cutting back on the pre-taper number of reps. The final week also includes a daily reduction in mileage over the last few days that mirrors the pattern of the weekly reduction (see Pre- Marathon Taper example below). Obviously, exactly what you do during your taper will depend on what you did before the taper.

If you want to give your performance a boost, try these tapering strategies before your next marathon. And if you taper smart enough, maybe you won't have to shave your body hair.

Different types of taper. Optimal performance is achieved with the fast exponential taper.

Dr. Jason R. Karp has a Ph.D. in exercise physiology, and is director and coach of REVO2LT Running Team, a freelance writer, fitness consultant, and competitive runner. He writes for numerous international running, coaching, and fitness magazines. He has coached high school and college cross-country and track and field, and currently coaches athletes of all levels and consults with fitness professionals and other coaches through RunCoachJason.com.