Posted: February 18, 2005

Science of Sport: Taking A Break - Without Breaking Up Your Hard-Earned Fitness

By Owen Anderson, Ph. D. (copyright © 2003-2005)

You need a break. You can't expect your body and mind to stand up to 12 months of nearly constant training - and then immediately embark on another year of hard work. Each year of your training life should feature at least one major break designed to enhance mental and physical recovery. Without such a peaceful pause from strenuous training, the risks of injury and overtraining in a subsequent year are likely to increase.

However, it is unclear how long this substantial break should be. Some runners (including many of the top Kenyans) favor a three- to four-week respite from training, but research suggests that such lay-offs are associated with significant drops in fitness. For example, one scientific study detected a 7-percent drop in maximal aerobic capacity in athletes who did not train for three weeks (1). For a 10-K runner averaging about 40 minutes for the race, this drop-off would add about two to three minutes to finishing time.

There is also evidence that even-shorter breaks can harm exercise capacity. The classic work in this area was carried out in the late 1970s by Michael Houston, Henning Bentzen, and Henrik Larsen at the revered August Krogh Institute in Copenhagen, Denmark (2). The '70s were an extremely interesting period in the overall history of exercise physiology; researchers were just beginning to understand the array of physiological changes which took place in response to strenuous endurance training, and it was natural for them to ask whether these adaptations persisted for very long when training stopped. In the Copenhagen study, six highly trained runners (average age 33, marathon time range 2:35-3:10, weekly training distance 60 miles or more) simply ceased training for 15 days. To make matters worse (for the runners), a walking plaster cast was placed on each runner's right leg for the first seven days of detraining, immobilizing the calf muscles.

The 15-day period without training produced a 4-percent fall in VO2max (maximal aerobic capacity) in the well-seasoned runners and also induced drops in key, energy-producing muscle enzymes of 13 to 24%. Actual running performance (measured as the amount of time the subjects could continue running at an exertion level of 94% of VO2max, which is very close to 5-K race intensity) fell by a frightening 25%, and peak heart rates associated with these efforts climbed by nine beats per minute.

A separate, more-recent investigation detected a close-to-8-percent drop in maximal aerobic capacity in a group of competitive, experienced, female runners after just a 10-day lay-off (3). 2400-meter race times in these same runners slowed by an average of 22 seconds after five additional days (15 days total) of detraining.

Taken together, these studies provide strong evidence that fitness can fall precipitously during break periods. It is true that fitness gradually returns once training is resumed, but some training theorists have argued that it is harder to reach a very high peak in performance during any one training cycle if an athlete begins the cycle from a relatively low "platform" of fitness, rather than a higher one. In this view, a 4- to 8-percent fitness plummet (associated with a break from training) might be counterproductive from the standpoint of long-term improvement.

Although three- to four-week lay-offs seem to have a strongly negative impact on fitness and performance, breaks of the same duration might actually be ideal from the standpoint of recovery. For example, research has shown that four-week recovery periods are needed for marathon-runners' leg muscles to begin to return to normalcy following a marathon (4), and one might reasonably argue that the same would be true for runners who have conducted extended training programs of rather ample intensity and/or volume.

Unfortunately, exercise scientists aren't sure how much restoration the muscles - or the nervous system - really need after a solid year of training, and of course the amount of recovery required may vary greatly; a 20-mile per week 5-K runner, for example, probably has different recovery needs, compared with the 70-mile per week marathoner. The former might prosper with a three-week respite, while the latter might need as much as six to eight weeks of light or no training to truly recover. The psychological characteristics of an athlete will of course at least partially determine the optimal length of a break, too. Athletes who become depressed when training is "taken away from them" may have troubles with long breaks, even though their leg muscles might really need such extended furloughs. On the other hand, runners who reach the end of the training year dreading their long or intense workouts might truly benefit from lengthy spells of inactivity. During their break periods, these runners will often wake up in the morning feeling glad that they do not have to train strenuously that day; this does not mean that they have lost their competitive edge - it simply means they are getting a great break.

To summarize, we can say that endurance athletes walk a tightrope when they take their breaks. As they elongate their lay-offs, restoration may be optimized, but actual fitness may fall. If fitness falls far enough, it may be difficult for athletes to return to the previous-season's fitness level in a reasonable period of time. On the other hand, if recovery periods are short, fitness may be well-preserved, but an athlete may enter a new training period in a far-less-than-recovered state - and then "burn out" during the following season.

So how long a break should you really take, and how long will it take to come back to par after your time away from the rigors of training? To answer these two key questions, it is necessary to take a look at what actually happens physiologically when a runner stops training for awhile. As it turns out, the performance of the heart appears to go downhill fairly rapidly once training ceases. One of the key declines in heart function is a fairly rapid drop-off in stroke volume, which is simply the amount of blood pumped out to the body by the heart with each beat.

Of course, stroke volume is an indicator of how much blood can be pumped to a runner's leg muscles during running. As it turns out, a three-week break during which no running is carried out can send stroke volume plummeting downward by more than 10 percent. When exercise scientists first learned of this rapid cardiac downfall, they were quite shocked at the heart's apparent decline, but some ingenious research carried out by Eddie Coyle and his colleagues at the University of Texas revealed that the downturn in stroke volume actually was not caused by heart weakening.

What causes stroke volume to fall when runners are on furlough, then? Coyle found that the blood volume (the total amount of blood in the heart and blood vessels) of endurance athletes declines by an average of half a quart, or 10 percent, during a three-week break period. Speculating that it was this decline in blood volume - not heart ineptitude - which reduced stroke volume, Coyle alertly pumped fluid back into the blood vessels of the athletes taking breaks and was able to reverse the reduction in stroke volume almost completely (5)! Thus, Coyle showed that it is a loss of blood, not a heart handicap, which sends stroke volume sinking downward after just three workout-free weeks.

Trying to avoid unnecessary nicks and cuts to your skin won't help prevent this unpleasant blood loss. The disappearing plasma is literally urinated out of the body when training stops. Fortunately, although this decline in blood volume happens rather rapidly when you take a break, the missing blood can be restored quite quickly by a small number of intense workouts. This is important information: We'll use it to create what we think can be an optimal break for most runners.

In addition to the ebbing away of blood and the consequent sinking of stroke volume, other bad things can happen during break periods, but the majority of these physiological performance pitfalls seem to occur at a considerably slower rate. For instance, your leg-muscles' ability to extract oxygen from the blood does not decline significantly until a break is extended beyond three weeks or so.

There is even better news about muscle capillarization (the extent to which your muscles are supplied with adjoining blood capillaries). Having lots of little blood vessels (capillaries) looped around your muscle cells is great for performance, because it improves the delivery of oxygen and nutrients to your muscles and also enhances the removal of troubling substances which might induce fatigue (like hydrogen ions, for example, which are produced inside muscles when glucose is broken down oxygen-independently to form lactate). A good endurance training program should boost capillary density by up to 50 percent, and not a single one of these extra capillaries appears to be lost, even if breaks from training last for three months (6)!

This makes it seem as though the stroke-volume slaughter is all we need to worry about during breaks, but there is another worrisome problem: Enzymes of energy metabolism - chemicals inside our muscle cells which are necessary to create the energy required for running - begin a fairly steady decline almost as soon as training ceases. It is known that enzyme activity decreases by about 20 to 25 percent in experienced runners after just a three-week break. If a break continues, there is a slower - but nonetheless progressive - decline in enzyme activity, until an individual reaches the baseline level which is genetically and historically programmed for him/her.

Since the heart's stroke volume can be revitalized rather quickly and since muscle-enzyme levels decline at a fairly predictable rate during break periods, some individuals have suggested that it can be relatively easy to estimate how long it will take to "get back in shape" once a lay-off ends. Sports scientists have noticed that if an experienced runner stops training and enters a break period, his/her muscle-enzyme activity will shrink to a level about half-way between highly trained and completely detrained states in about 10 days! In the next 10-day period without training, his/her enzyme activities will move half the remaining "distance" to the completely detrained level. Eventually, muscle-enzyme concentrations will stabilize at the detrained plateau, usually after about a 60-day (two-month) break from training.

If increases in enzyme concentrations (associated with a return to training) occur at the same rate as decreases, one might predict that a 10-day lay-off would necessitate 10 days of serious training to get the enzymes back again. Unfortunately, the muscles and their valuable enzymes just don't work that way. After a cushy 10-day break, for example, your muscles can not get their beloved enzymes back in just 10 days, even if rather furious training is conducted. In fact, after 10 days of off-time, it takes about 30 days for muscles to climb back to 95 percent of pre-break levels!

Worse yet, it takes 40 days to get back to 95 percent if a break is extended to 20 days (about three weeks). The damage ends there, though: After 30 days of detraining, it also takes 40 days to flood the muscles with enzymes again. In fact, for any break period lasting longer than 20 days or so, it takes 40 days for enzyme levels to get back to almost-normal once serious training is resumed.

The apparently long periods required to restore enzyme levels following a break are somewhat scary to serious athletes, but the slowness of the enzyme response to training doesn't mean that you should never take a break. For one thing, there is some evidence that performance ability can return before enzyme concentrations are fully restored (2). And - let's face it: The longest time required to get back to 95 percent is 40 days. Now, if you have taken a break during the month of December, for example, and you resume training in January, with a big race scheduled toward the end of May, your enzymes will be OK again in about mid-February, leaving you plenty of time to train in a very high-quality away before your major competition - and spike your enzymes above the levels which were reached in the previous season.

Although the break-associated losses in enzyme concentrations seem manageable, there is another problem to consider: If you have been training in warm weather, heat acclimation may also be lost during a break period, a loss which can worsen one of the key problems associated with taking a break. As you already know, blood volume falls during break periods - and then increases if intense training is resumed. One of the adaptations associated with heat acclimation is an increase in blood volume, above and beyond the blood-volume spikes which are a characteristic response to strenuous training per se; some experts contend that the heat-acclimation process can account for as much as 40% of the upswing in blood volume experienced by athletes training in the heat, with training effects accounting for the other 60% (7). Thus, when an athlete takes a break after a spate of training in hot weather, blood volume may take an unusually large nosedive (there will be the usual loss associated with a lack of training and an additional loss because of the fading away of heat acclimation). This double whammy can hit stroke volume hard and may have a particularly large, negative impact on exercise capacity, especially if an athlete "returns to action" when it is still hot.

The loss of heat acclimation would also mean that sweat rates would be lower at above-normal body temperatures during exercise and that the "core-temperature threshold" above which sweating actually occurs would rise (8). As a result, an athlete's body temperature would be higher at any specific exercise intensity (except possibly for very low ones), and fatigue would occur earlier during exertion. We are not telling you this to discourage you from taking a break when weather conditions are rather steamy; there are times when you may need to do so. In addition, there is some good news: Once heat acclimation is achieved, it takes awhile to lose it, with estimates running from 17 to 34 days for a complete loss of heat adjustment (9). The better news is that heat acclimation can be re-gained rather quickly, probably after just seven to 10 days of training in the heat.

What should you do after your break is over? As it turns out, the period following a break, when blood volume, enzyme levels, aerobic capacity, and performance ability are hopefully rising steadily, is a very interesting one. There is debate about whether the risk of injury is heightened immediately following a break; one camp argues that the risk is actually lower, since muscles and connective tissues have repaired themselves effectively during the break. However, a reasonable, opposing viewpoint is that runners are vulnerable to injury during re-starts, since running-specific strength has probably fallen during the break. It would certainly not be unwise to begin one's start-ups after breaks with decent doses of general and running-specific strength training.

While scientific research can not shed much light on the injury question (no controlled investigations have been conducted), research does reveal that gains in performance do not occur at a slow, steady rate once training is resumed. Somewhat surprisingly, substantial improvements in performance can actually occur fairly quickly after the training year begins, because blood - and thus stroke - volumes respond very rapidly to training, especially if the training is fairly intense. Even the slow-poking, 40-day-requiring, aerobic enzymes make their biggest jump during the first 10 days following the resumption of training, compared to subsequent 10-day periods.

An issue which often arises is whether a break should be different for a relatively inexperienced runner, compared with someone who has been training for many years. One idea here is that the inexperienced runner might lose fitness more quickly during a training-free period - and thus would be better off with a shorter break. Of course, inexperienced runners might have poorer running-specific strength, compared with long-term harriers, and thus might actually need longer breaks (to give their more-battered muscles and connective tissues more time to heal).

Research in this area has not been very conclusive. We do know that if someone takes up running for the first time, trains for a couple of months, and then decides that he/she is ready for a break, max aerobic capacity will usually rocket upward by from eight to 20 percent during the training period - but will steadily head south during the break. In fact, if the "break" continues for about eight weeks, max aerobic capacity will return to its original, lowly, sedentary-life-style-associated level (10). It would be as though the individual had not trained at all.

For experienced runners, the story - at first glance - seems to be different. When a very experienced runner (defined as someone who has trained consistently for five or more years) goes on break, he/she begins losing the physiological adaptations to training, just as the novice runner does. However, even after several months of being on furlough, the experienced runner does not lapse back to the "normal", untrained state. After three months of non-training, the experienced athlete still usually possesses a max aerobic capacity with is almost 20 percent above the level observed in the sedentary population. In addition, the same experienced athlete (who is temporarily on break) will have an increased ability to extract oxygen from the blood, greater aerobic-enzyme activities within muscle cells, and more small capillaries surrounding muscle cells, compared to the sedentary citizenry (11).

That seems to be good news for experienced runners; it would seem that they could take longer breaks than less-experienced folks, without losing big chunks of fitness. In addition, it would seem that veteran runners would be more resistant to losses in fitness associated with injury- or illness-induced training stoppages.

The problem, though, is that the apparent steadfastness of maximal aerobic capacity, aerobic-enzyme concentration, and high capillary density in experienced runners may be due to genetic factors, rather than long-term training. Individuals with higher-than-normal oxygen-processing abilities, aerobic-enzyme levels, and capillary numbers might be more likely to become experienced runners, compared with average Joes with rather miserly physiological characteristics. If this is true, one would not expect that experienced athletes as a group would ever return to "normal" (provided we define normal as the population average).

Getting back to our original question, what should your break actually look like? Since four weeks are necessary to repair serious muscle damage, we'll set four weeks as the optimal break duration. This may seem a bit surprising, since we have already indicated that it will take muscle enzymes at least 40 days to get back to near-normal after such a lengthy time away - and that even the muscles' ability to extract oxygen from the blood begins to wither after just three weeks. Worse yet, max aerobic capacity is likely to veer downward by 10 percent or more during a one-month time of easiness.

Nonetheless, all of these attributes can be restored within a new training cycle, and once they are restored an athlete can jump up to even higher levels, compared to the year before. In addition, the break we are going to recommend to you is not a complete break, because it is our contention that the inclusion of an occasional, not-excessively stressful type of workout does not retard or prevent complete recovery - and will keep enzymes, max aerobic capacity, and performance from falling too far, if at all. The key is that these occasional workouts will have to be exactly the right type, as we will explain in a moment.

Research on carrying out small amounts of training during break periods actually goes back a very long way. In a beautiful - but now almost completely forgotten - study carried out in the early 1970s by Paul Brynteson of South Dakota State University and Wayne Sinning from Springfield College in Massachusetts, 21 individuals carried out reduced training for five weeks using 80, 60, 40, or 20% of their usual training load (12). The subjects were undergraduates, graduate students, and faculty members at Springfield College, and their normal training consisted of five 30-minute workouts per week on an exercise bike at an intensity of 80% of heart-rate max. During the 35-day period of reduced training, the individuals trained one, two, three, or four times per week (as opposed to their usual five). Amazingly enough, the students who trained just once weekly during the five-week period were able to completely preserve VO2max, recovery heart rate, and maximal ventilation rate (as did the cyclists working out two to four times per week). This was the first evidence that a very small training volume, the kind of light physical burden which should not be antagonistic to strong recovery, could perfectly sustain the physiological adaptations resulting from prior training.

The South-Dakota-Springfield research drew some fire, however, from critics who contended that since the individuals in the study were rather inexperienced trainers (indeed, they had trained regularly for just five weeks before the reduced-training periods began), the results could not be generalized to serious, experienced athletes. In the early 1980s, Dr. R. C. Hickson and his colleagues at the University of Illinois at Chicago carried out a trio of intriguing studies with both male and female athletes to partially correct this problem (Hickson's subjects had been training longer and also participated regularly in recreational sports) and also to learn more about breaks and reduced training. In one of the investigations, Hickson and Maureen Rosenkoetter found that endurance athletes could trim their frequency of training by 67 percent (from six weekly workouts to just two) and yet still maintain their maximal aerobic capacity and endurance for up to 15 weeks (!), as long as the two remaining workouts were high-quality (13). When Hickson's paper was first published, many endurance athletes were heard to mutter, "Then why are we doing all this work?" This brief stir quieted down, however, and endurance athletes resumed their love affair with high-frequency, high-volume training, an arranged marriage which has remained strong until this day.

An interesting aspect of the Hickson-Rosenkoetter study was that the endurance athletes - prior to entering their reduced-training phase - had been carrying out three bicycle workouts and three running sessions per week. When they dropped down to two weekly workouts, one was a running session and the other a biking effort. Each was high quality: The running workout called for running as far as possible in 40 minutes, and the bike exertion incorporated six five-minute intervals at close to max aerobic capacity, with two-minute recovery intervals. VO2max held rock-steady for both biking and running after five, 10, and 15 weeks of diminished-frequency training (remember that an athlete's VO2max on the bike will usually be different from his/her VO2max while running, and thus both need to be measured; in this study, each variable was assessed at five-week intervals, and neither budged downward at all). It is tempting to conclude that one hot running workout per week preserved running VO2max and that one fiery bike workout each week etched bicycle VO2max in stone, but there was probably some synergy involved. That is, the intense bike workout probably helped running VO2max a bit, and the stringent running effort may have aided bike VO2max, too. So, we'll simply be at peace with the idea that two good workouts per week can preserve aerobic capacity for almost four months.

In a subsequent piece of research, Hickson and his helpers left training frequency untouched (at six workouts per week). However, they reduced their athletes' volume of exercise, such that the individuals were training just 13 minutes per workout, instead of the usual 40 minutes (another 67-percent downswing). Exercise intensity during these 13-minute exertions was set at exactly the same level as the 40-minute affairs. As it turned out, VO2max did not waver over a full 15-week period of reduced-volume training. In addition, a demanding test which called for each athlete to exercise at close to vVO2max for as long as possible revealed no loss in performance capacity for the 13-minute athletes - again for up to 15 weeks of greatly reduced training (14). Essentially, the athletes lost no fitness, even though they were only covering one-third of their usual weekly distances!

As you can see from these two classic studies, it is possible to rather drastically hack away at your frequency and volume of training during a break period without facing dire consequences. Cut back on intensity, though, and - oh brother! - everything changes. In Hickson's last study, he found that when endurance athletes reduced the intensity (running speed) of their workouts, while preserving frequency and volume, max aerobic capacity plummeted significantly within just five weeks (15).

These three, ground-breaking studies, taken together, mean that an occasional, intense workout is a very strong preserver of fitness during a period of much-reduced training. But - how often is "occasional," and what should these intense workouts actually be like? We'll hang our hat on the idea that one good-quality running workout per week during a break, plus one non-impact, non-running, reasonable-quality session per week will permit good mental and physical recovery and will also preserve fitness completely during a four-week intermission between training years. This is what Hickson's research revealed, and it is the best information we have.

Please don't get the wrong idea, though: It is not absolutely necessary to train during a break period. If you prefer, you may simply take the time completely away from training - and take your physiological losses, counting on the fact that your fitness will bounce back quickly once you start training again. For someone who has had a particularly rigorous year, who has completed a challenging series of races, or who has just finished a marathon, this may be exactly the right thing to do, especially if the athlete can effectively handle the "mental stress" associated with doing nothing (many athletes "stress out" about the side effects of recovery, including weight gain, easily observable loss of strength, and suspected losses in fitness and performance).

On the other hand, if you would like to "keep your hand in," so that you can begin the following year from a higher platform of strength and aerobic capacity, and - based on your knowledge of yourself - you are relatively sure that you can recover mentally and physically while still performing about two workouts per week, you could employ workouts like the following ones during your break. These sessions are divided into appropriate running workouts (to be carried out just once a week) and non-running recovery sessions (also performed once a week):

Great Running Workouts for Break Periods

(1) The Stroke-Volume Preserver: Jog easily for 10 minutes to warm up, and then burst along a forest trail, padded park pathway, or beach for 15 minutes, maintaining what feels like 5- to 10-K intensity throughout (please see reference # 14 for a validation of this kind of session). Cool down following the 15-minute surge with 10 minutes of light running.

(2) The Aerobic-Enzyme Enabler: In the forest, at a pleasant park, or on a stretch of beautiful beach, warm up with 10 minutes of relaxed jogging, and then complete 25 minutes of fartlek effort, alternating - very spontaneously - four- to five-minute surges at bust-butt intensity with two to three minutes of easy floating. Cool down at the end with 10 minutes of no-problem ambling.

Great Non-Running Workouts for Break Periods

(1) The Max-Out: On an exercise bike, start cycling with the intensity set at the lowest-possible level (generally, a "1"). After one minute, increase the intensity to "2". After the second minute, increase the intensity to "3", and so on, until you reach a level of effort which you can not sustain for a full minute. Recover by pedaling easily for four minutes, and then repeat this 1-2-3-4-5 …… pattern one more time, before cooling down with 10 minutes of light pedaling. You will definitely strike VO2max and come close to maximal heart rate on each upward sequence (obtain written permission from your cardiologist beforehand), and your blood-lactate concentrations will soar, providing a stimulus for lactate-threshold maintenance - or even improvement.

(2) Nairobi Hills: On a stair-stepper machine (the foot-platform type, not the descending-escalator variety), warm up with 10 minutes of easy climbing, and then alternate one-minute intervals at a hard intensity but rather routine stepping rate with one-minute intervals during which you crank up your stepping rate to 240 steps per minute or beyond. Continue in this fashion for about 20 minutes (alternating one minute of grueling stepping with one-minute cadence crank-ups), and then cool down with 10 minutes of easy climbing.

(3) The Hickson: On an exercise bike, warm up with 10 minutes of light pedaling, and then hit 4 X 5 minutes at what feels like 5-K race intensity, with two-minute, easy-pedal recoveries and a 10-minute cool-down at the end.

Don't forget to stretch all of your major leg-muscle groups after these sessions are over, and remember that these workouts should be interesting and fun to carry out. If they feel like drudgery, it will be hard to argue that they are boosting your mental recovery. In addition, if they leave you completely physically exhausted afterwards, you have done too much. If you are tempted to do a lot of work (an easy-to-understand temptation, since the frequency and volume of training are so low during your break), simply remember Hickson's athletes, who maintained their fitness with just two intense 13-minute workouts per week. Thank you, R. C.!

In addition to your yearly four-week break, you will want to take shorter breaks throughout the year, at times when you are beginning to feel stale or overtrained, for example; these breaks from training will give your body a chance to "catch up" with all the adaptations it needs to make in response to your rigorous training. You may also be confronted with an enforced break: An injury may make it temporarily impossible for you to train. Assuming that no training is carried out at all, how long can these short breaks be without harming your ability to perform?

There is actually good scientific evidence on this issue, and the news is fairly reassuring. In one fascinating investigation, Canadian researchers divided club-level cyclists (men and women) who normally trained five days per week, 60 minutes per day, at an intensity of about 80% VO2max, into four groups (16). Members of one group continued to train normally, athletes in a second group tapered their training over a four-day period, cyclists in a third group tapered for eight days, and individuals in a fourth group (our star athletes for the moment) did absolutely nothing at all for four days.

As it turned out, the four-days-of-nothing plan did almost nothing bad to the athletes. For example, power output at lactate threshold did not fall during the four-day break, and muscle-glycogen concentrations actually increased, an effect which should enhance endurance during extended exertion. It is true that the do-nothing group "suffered" from a decrease in HOAD activity after their inaction. This has nothing to do with Australian tennis; HOAD is a muscle enzyme, and its fall in activity would generally mean that athletes would burn more carbohydrate and less fat during exercise. Such an effect would be unlikely to harm the performance of a middle-distance, 5-K, or 10-K runner. Of course, these findings don't mean that you should do absolutely nothing during the four days before your races; the cyclists who tapered for four to eight days (carrying out small amounts of high-quality exercise) actually fared better than the do-nothingers. The tapered athletes, for example, actually increased their power outputs at lactate threshold (remember that the no-training folks just maintained theirs), and the tapered individuals' muscle-enzyme activity levels also looked a bit better. The point here is simply that four days of no training at all seem to produce no significant physiological or performance pitfalls. You can take such a break without becoming anxious about your ability to train or race.

In another relevant study, seven competitive, female, middle-distance runners completely stopped training for 15 days, while eight counterparts continued their usual training (3); these women had an average age of 20 and a mean max aerobic capacity of 50 ml/kg-min. All had been training regularly for at least two years. When the seven non-training runners were tested after five days of complete inactivity, their mean aerobic capacities were just as high as they had been at the beginning of the lay-off. In addition, stroke volume and total cardiac output did not fall over the five-day period, nor did maximal heart rate change. Furthermore, the rate at which oxygen was extracted from the blood by muscles did not decline, and plasma volume remained unperturbed. In short, there was no sign of fitness being lost after five days of complete inactivity.

When the inactivity continued for 10 days, however, a key problem became apparent: Between days six and 10, max aerobic capacity fell by approximately 8%. VO2max did not fall any further between days 11 and 15 (of inactivity), but when the inactive athletes ran 2400 meters all-out (on the 16th day), their performance times slowed by an average of 21 seconds - from 9:02 to 9:23.

The take-home lesson from these two studies is that you can probably do no training at all for four to five days without losing significant physiological prowess or performance capacity. This should be reassuring if (1) life gets in the way of your running, and you can't train for awhile, (2) you are injured for a few days and are unable to train, or (3) you are burned-out mentally and/or physically and need a short break. Anecdotally, the author of this article has observed situations in which runners do more than hold their own after a complete four-day break from training; they run better than they have in a long time. This is probably because their bodies finally have a chance - during the break - to adapt to all the demanding training which has been completed. It can be a good thing to take a complete, two- to four-day break every month; you should never feel that you must train six days a week, week after week.

Of course, good runners plan their breaks; they don't wait for injuries or overtraining to jam breaks down their throats. A yearly, four-week break is essential for reviving your running, and shorter (three- to four-day) breaks interspersed throughout the year can also be very valuable. Remember that four-week breaks do not lead to massive performance fallbacks when fairly intense, short-duration training is carried out once or twice a week; for runners, this training can be carried out on the feet and on the bike. Remember, too, that your fitness will shoot up almost immediately once training is resumed after a four-week break, and that your break will give you a platform of muscular and nervous-system health from which you can spring to new heights of performance in the ensuing year. The bottom line is that breaks are good for you - so good that you should plan them as carefully as you do your strenuous training. ©

References

(1) "Detraining and Retention of Training-Induced Adaptations," Sports Science Exchange, Vol. 2 (23), 1990
(2) "Interrelationships between Skeletal Muscle Adaptations and Performance as Studied by Detraining and Retraining," Acta Physiologica Scandinavica, Vol. 105, pp. 163-170, 1979
(3) "Fifteen-Day Cessation of Training on Selected Physiological and Performance Variables in Women Runners," Journal of Strength and Conditioning Research, Vol. 17(3), pp. 599-607, 2003
(4) "Are You Already 'Damaged Goods' When You Show Up for Your Races?" Running Research News, Vol. 7(5), pp. 1, 3-5, 1991
(5) "Effects of Detraining on Cardiovascular Responses to Exercise: Role of Blood Volume," Journal of Applied Physiology, Vol. 60, pp. 95-99, 1986
(6) "Capillary Supply and Mitochondrial Content of Different Skeletal Muscle Fiber Types in Untrained and Endurance-Trained Men: A Histochemical and Ultrastructural Study," European Journal of Applied Physiology, Vol. 40, pp. 197-209, 1979
(7) "Exercise Training-Induced Hypervolemia: Role of Plasma Albumin, Renin, and Vasopressin," Journal of Applied Physiology, Vol. 48, pp. 665-669, 1980
(8) "Skin Blood Flow and Sweating Changes Following Exercise Training and Heat Acclimation," Journal of Applied Physiology, Vol. 43, pp. 133-137, 1977
(9) "Human Heat Acclimatization." In Pandolf et al. (Eds.), Human Performance Physiology and Environmental Medicine at Terrestrial Extremes, pp. 153-197, Benchmark Press, Indianapolis, 1988
(10) "Low-Intensity Training, Inactivity, and Resumed Training in Sedentary Men," Acta Physiologica Scandinavica, Vol. 101, pp. 351-362, 1977
(11) "Time Course of Loss of Adaptations after Stopping Prolonged Intense Endurance Training," Journal of Applied Physiology, Vol. 57, pp. 1857-1864, 1984
(12) "The Effects of Training Frequencies on the Retention of Cardiovascular Fitness," Medicine and Science in Sports, Vol. 5(1), pp. 29-33, 1973
(13) "Reduced Training Frequencies and Maintenance of Increased Aerobic Power," Medicine and Science in Sports and Exercise, Vol. 13, pp. 13-16, 1981
(14) "Reduced Training Duration Effects on Aerobic Power, Endurance, and Cardiac Growth," Journal of Applied Physiology, Vol. 53, pp. 225-229, 1982
(15) "Reduced Training Intensities and Loss of Aerobic Power, Endurance, and Cardiac Growth," Journal of Applied Physiology, Vol. 58(2), pp. 492-499, 1985
(16) "The Effects of a Reduced Exercise Duration Taper Programme on Performance and Muscle Enzymes of Endurance Cyclists," European Journal of Applied Physiology, Vol. 65, pp. 30-36, 1992

To learn about Owen-Anderson's running camps in California, please send a note to Owen at owen@rrnews.com.

Copyright © 1998-2004 by Running Research News