Triathlon: Maintaining Training Adaptations During the Off-Season

Written by: Bryan C. Bergman, Ph.D.

Many athletes are taking a break from training in the current off-season, as the competitive calendar ends in October or November. Even the most elite athletes take a break from the rigors of in-season training. However, how long should that break be? Should athletes perform other types of activity to "stay in shape" during the break? How much of fitness will be lost if from a 1, 2 or 4-week break? These types of questions are vital for an off-season training program, as the current off-season is where next year's success will largely be determined. Take Jan Ullrich as an example - what does he do in the off-season? Clearly, not enough - and his performance every season is hampered by an unorganized off-season.

The off-season could be argued as the most important time of the training year. Have a great off-season, and an athlete will likely have great success the following season. Have a poorly planned off-season, with too much time off, emphasis on the wrong types of training and other pitfalls, and an athlete may be mentally broken, or in such poor shape at the beginning of the season that he or she must play catch-up the rest of the year.

Off-season programs should be designed to allow athletes to mentally rejuvenate, while minimizing the loss of physiological adaptations gained during the season that just ended. Detraining is defined as the partial or complete loss of training-induced physiological adaptations due to reducing or stopping training. Detraining is important to understand, as minimizing detraining in the off-season is important for maintaining adaptations and building upon the previous season's gains. Thus, by preventing dramatic detraining in the off-season, athletes can build upon training adaptations and become stronger every year. How do you think Lance Armstrong, George Hincapie and Walker Ferguson (just to name a few) become stronger every year? They minimize detraining in the off-season, relax after a hard season, build upon their weaknesses and come back stronger the following season. This is the basis of organized, periodized training employed by CTS coaches - progression and improvement from year to year.

So what happens when a highly trained athlete stops training during the winter season? The following section summarizes scientific studies that have examined physiological and biochemical responses to detraining.

VO2max
Following complete cessation of training, VO2max decreases in previously highly trained individuals after as little as 4 weeks, with the decrease in VO2max varying between 4 and 14% (19, 22, 43, 59). The decrease in VO2max during the first 3 weeks of detraining is due to a decrease in maximal cardiac output. Subsequent decreases in VO2max are due to decreased oxygen extraction, likely from a decrease in mitochondrial density (see figure below).

Blood Volume
Detraining of 4 weeks has been found to decrease blood volume by 12%, mostly due to a 9% decrease in plasma volume in previously well trained athletes (19). Thus, most of the loss of blood volume was due to a decrease in the water compartment of the blood, however 3% of the decrease in blood volume could be attributed to a decreased red blood cell mass, which contributes to the decreases in VO2max and performance. Plasma volume will decrease after 2 days of inactivity, and decreases proportionally to the total time of training cessation. The decreased blood volume can also largely explain decreased VO2max and increased submaximal heart rate seen in the detrained state.

Endurance Time
Endurance performance of previously highly trained athletes decreases during a period of detraining by as much as 25% in as little as 2-4 weeks of inactivity (44, 55). Decreased endurance performance may be explained by the increased use of carbohydrate as a fuel during submaximal work following detraining (22, 55, 59).

Lactate concentration during submaximal work and lactate threshold

Lactate concentration during submaximal work has been shown to increase after as little as 1 week of detraining in previously highly trained athletes (15, 21, 62). However, the mechanism for the increased lactate concentration cannot be determined from the detraining studies. It is likely that the increased lactate concentration arises from a decrease in lactate clearance, which is the main adaptation during endurance training responsible for decreased arterial lactate concentration (6).

Lactate threshold also decreases progressively during 56 days of detraining in previously highly trained individuals (21). However, decreases in lactate threshold stabilized after 3 months of detraining to values significantly greater than untrained controls. Lactate threshold is the most trainable factor influencing endurance performance. High lactate threshold is one of the most important predictors of endurance performance. It takes a lot of time, even years, to increase lactate threshold to an athlete's genetic potential, so it is vital to prevent a large drop during the off-season. Only by building upon the current season's gains in LT, will LT increase from year to year to an elite level.

Muscle Glycogen
Glycogen is the storage form of glucose in the body. An increased amount of muscle glycogen improves performance and is an adaptation to endurance training. As little as a week of detraining results in a decrease in the body's muscle glycogen storage capacity.

Capillary Density
Capillaries bring blood and oxygen to muscles. Increased muscle capillary density is an important adaptation to endurance training. Cessation of training in athletes has been reported to decrease or not change capillary density in well trained athletes.

Mitochondrial Volume
When training is stopped, mitochondrial content of the skeletal muscle decreases (12, 34, 49, 59). Athletes who have been training for many years experience a rapid initial decrease in skeletal muscle oxidative enzyme activity in the first 8 weeks of detraining, followed by a stabilization of enzyme levels 50% above sedentary controls throughout the remaining 4 weeks of detraining (22). Upon further analysis of single muscle fibers, it is found that in these well trained athletes, the elevation of enzyme activities above sedentary controls is mainly due to the maintenance of enzyme levels in fast twitch muscle fibers. After 12 weeks of detraining, oxidative enzyme activity of fast twitch muscle fibers remained 50-80% above control values, while slow twitch muscle fibers had decreased to control levels (12, 22).

This effect may be due in part to the large amount of training time that it takes fast glycolytic fibers to adapt to the stress of endurance exercise and take on characteristics of fast oxidative glycolytic fibers. Thus we are seeing minimal fiber type conversion with detraining, possibly due to the length of time the adaptation originally took to occur.

So what should be done to minimize the loss of training adaptations during the off-season?

Reduced Training
The answer is to decrease, but not stop training. But by how much should training decrease?

It is impractical and mentally very difficult to maintain race fitness year round. Thus, during the off-season, training should be reduced in such a way to maintain fitness gains from the current season, allowing the athlete to become stronger every year.

Of the many components of training, the most important for this discussion are Frequency, Intensity, and Time (or volume). How much can each of these components decrease?

Frequency
The frequency of training sessions plays an important role in the retention of physiological adaptations during a period of reduced training. Most studies suggest that when submaximal endurance performances were negatively affected during a reduced training period, training frequency was reduced by at least 50% (42, 62). However, studies that observed no change in athletic performance only reduced frequency by around 20-30% (15, 40). Thus, in order to maintain physiological adaptations to endurance training, frequency of exercise bouts should not decrease more than 30%. In other words, if an athlete currently trains 6 days/week, training should not drop below 4 days/week during reduced training periods.

Volume
As long as training frequency does not drop more than 20-30% during a period of reduced training, it can safely be assumed that training volume can be decreased up to 70-80% with no decreases in submaximal exercise performance. However, performance is only maintained when the intensity of training is not reduced from pre-reduced training levels. Considering training intensity will drop during the off-season, volume should not be allowed to drop by 70-80%. The exact amount volume can decrease in the off-season is individual, and influenced by training intensity and the age of the athlete.

Intensity
The specific effect of training intensity has not been isolated and studied in highly trained endurance athletes. However, Neufer (62) reported that in previously untrained individuals, training intensity must be maintained during a period of reduced frequency and/or duration in order to maintain training adaptations. Similarly, in the previously reported studies where frequency and volume were reduced, training intensity was maintained or only reduced by 10-20% from pre-reduced training levels (15, 40, 42, 46, 62). Therefore, it can be speculated that exercise intensity must be maintained or only decreased by 10-20% in order to maintain training adaptations during a period of reduced training. Greater drops in training intensity will results in proportional decreases in fitness.

Conclusions
During a period of training cessation, VO2max, endurance time, and lactate threshold will decrease rapidly in highly trained athletes. Capillary density appears to be maintained for as long as 12 weeks in highly trained endurance athletes who have been training for many years. In highly trained endurance athletes, mitochondrial volume decreases rapidly in the first 8 weeks of detraining, but stabilizes at 50% above sedentary values for at least 4 more weeks of detraining.

Thus, much of an athlete's performance potential will be decreased after 8 weeks of exercise cessation, yet their capillary density and some of their oxidative enzyme adaptations will be retained through at least 4 more weeks of detraining. Thus, after 2 months of no training, highly trained athletes will lose much, but not all of their physiological adaptations for endurance activities.

Highly trained endurance athletes must stay active in the off-season in order not to lose their training adaptations over a period of reduced training. They can decrease training volume by up to 70-80%, but the frequency of the training bouts can only be reduced by 20-30%, or in other words taking 2-3 rest days per week instead of one. While scientifically unstudied, it is speculated that training intensity must be maintained at close to pre-reduced training levels to prevent a drop in performance. However, maintaining training intensity year-round is impractical. Thus, less of a fall in training volume may help prevent the loss of physiological adaptations in the off-season with decreases in training intensity.

Bryan graduated from the University of California at Berkeley in 1999 with a Ph.D. in Exercise Physiology. He is currently a post-doctoral researcher at the University of Colorado Health Science Center, studying the interaction of exercise and nutrition on weight loss and obesity. Bryan is a Coach with Carmichael Training Systems. For more information on personal coaching packages that fit your lifestyle, goals and budget, please visit www.trainright.com.

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