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Posted: June 10, 2004

Athletics: The Hard/Easy Principle

From Advanced Marathoning by Peter Pfitzinger, Scott Douglas

Advanced Marathoning

Conventional wisdom calls for following the hard/easy principle of training, which is typically interpreted to mean that a hard effort is always followed by one or more recovery days. A recovery day may consist of an easy run, a light cross-training session, or total rest. During your marathon preparation, however, itís sometimes necessary to violate this training pattern and do back-to-back hard days. The appropriate interpretation of the hard/easy principle is that one or more hard days should be followed by one or more recovery days. Letís investigate the physiological rationale for following the hard/easy principle and look at two situations in which you should do back-to-back hard training days.

Reasons to Follow the Hard/Easy Principle
The hard day/easy day training pattern follows from the physiological dogma of stimulus and response - hard training provides a stimulus for your body to improve, but rest is then needed to allow your body to recover and adapt to a higher level. Three reasons to follow the hard/easy principle are to prevent glycogen depletion, to prevent illness, and to minimize the effects of delayed onset muscle soreness (DOMS).

Preventing Glycogen Depletion
As discussed in chapter 3, your body can store only a limited amount of glycogen. With a typical runnerís high-carbohydrate diet, you probably have enough glycogen to get you through a 20- to 22-mile long run or a hard interval workout. It takes about 24 to 48 hours to completely replenish your glycogen stores. When you do two hard workouts in a row, therefore, you risk going into the second workout with partially filled glycogen stores, becoming depleted, and having a bad workout. Although glycogen depletion is potentially a problem on the second hard day, with a bit of planning it neednít be an insurmountable problem. Three hard days in a row, however, would very likely lead to glycogen depletion and a prolonged recovery period. By following the hard/easy principle, you give your body time to build up your glycogen stores so you are prepared for the next hard workout.

Preventing Illness
After high-intensity exercise, your immune system is temporarily suppressed, creating an open window during which youíre at increased risk of infection. Studies indicate that the immune systems of healthy, well-trained runners are typically suppressed only following exercise lasting more than 1 hour at about marathon race pace or faster. Immune system suppression after high-intensity running has been found to last from 12 to 72 hours. The clear implication is to not do another hard training session until your immune function recovers from the previous hard session or race. Allowing at least one easy day before the next hard workout provides a minimum of 48 hours of recovery, which is typically enough time for your immune system to return to full strength.

Minimizing the Effects of DOMS
Contrary to many runnersí beliefs, high levels of lactate (lactic acid) in your muscles arenít what make you sore for several days after a hard effort. Essentially all of the lactate you produce in a race or workout is eliminated from your body within a few hours. Rather, DOMS is caused by microscopic muscle damage that occurs from eccentric (lengthening) muscle contractions, such as when you run downhill. During downhill running, your quadriceps muscles contract eccentrically to resist the pull of gravity and keep your knees from buckling. The resulting muscle damage leads to inflammation, which causes soreness. It takes 1 to 2 days for this process of muscle damage/inflammation/pain to reach a peak, and the effects can last for up to 5 days. While youíre experiencing DOMS, your muscles need time to repair. The damaged muscles are also weaker, so any workout done before the soreness goes away not only will be painful but also will likely not be intense enough to improve your marathon fitness.

The physiology of DOMS favors a 2 hard day/2 easy day approach because it takes 1 to 2 days for DOMS to kick in, then it takes another couple of days for the soreness to dissipate. By doing back-to-back hard days, you may sneak in your second workout before soreness and muscle weakness develop. You would then have 2 days to recover before the next hard effort.

Posted with permission from Human Kinetics Publishers, Inc.

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