by Thomas Kurz
This article covers requirement 11 for instructors. Requirements 9 and 10 are covered in the previous article.
11. Understand the concepts of fatigue, rest, recovery, and supercompensation.
Fatigue
The whole training process is predicated on fatigue and on recovery from it—degree of fatigue dictates the changes of training load, means of recovery, frequency and sequence of exercises and workouts, periodization, and nutrition. Without understanding fatigue it is not possible to understand all these issues.
Fatigue is the decreased capacity of the body, or part of it, to expend effort, resulting from exertion or excessive stimulation. There are several types of fatigue: mental (boredom); sensory (a result of intense activity of one or more of the senses); emotional (a consequence of intense emotions, observed after performing at important sports competitions, or after executing movements that demand overcoming fear); and physical (caused by muscle work). Although workouts cause all types of fatigue (in various degrees), the most obvious is physical fatigue. Physical fatigue directly affects the function and structure of the musculoskeletal system, and muscle fatigue is its main component.
Muscle fatigue is a complex phenomenon influenced by central nervous system factors and peripheral factors, such as damage to muscle cells. The two main factors causing muscle fatigue are mechanical damage and chemical damage to muscle cells. There is strong evidence to suggest a relationship between physicochemical damages and exercise-induced muscle soreness.
Mechanical damage is most likely to occur when the vector of force acting on a muscle fiber (muscle cell) is not parallel to its long axis. This is usually the case because of how muscle fibers are arranged in most muscles. (And indeed, hardly anyone has gotten strained or sore muscles of one’s arms, for example, by merely holding heavy weights with the arms hanging straight down. This is because in such a position the majority of muscle fibers lie parallel to the line of force, and the angles of those that are not parallel are very acute.)
Mechanical stress partially or completely destroys structures in the muscle cell. The more intense the effort, the greater the number of destroyed muscle cells, and destroyed cells cannot contract.
Chemical damage is caused by oxidative stress—the overproduction of oxygen-derived free radicals. Oxidative stress damages all the structures of the cell as well as enzymes and nucleic acids that store and pass genetic information.
Exercise leads to an increase in the free radicals produced, but many indicators of muscular damage caused by oxygen radicals are restored to normal in the after-effort recovery period. Even well-trained individuals display indicators of both damage and repair after a bout of hard exercise.
Important: Damaged muscle cell structures are not repaired by fixing them up but by rebuilding them (i.e., by tearing them down and then building anew). This means there is a time during the recovery when the damaged muscle cells are weaker than immediately after the original damage. This time may be several hours, even not until the next day, after an intense exercise. So, a sign—best not to be missed—of muscles not ready for any exercise is light soreness and sleepiness the day after the workout.
Rest
Type of rest (e.g., passive, active) and its amount, must be adequate for the training task. The wrong type or the wrong duration (too short, too long) of rest adversely affects the training effect. It may lead to undesirable changes in the character of the exercise, or worse, to detraining, overtraining, or even injuries.
Rest can be passive or active. Passive rest means no activity. Active rest means light, fun activity, usually just above the aerobic threshold and well below the anaerobic threshold, or onset of blood lactate accumulation. Recovery after intense efforts that generate excess lactate can be speeded up with active rest consisting of aerobic activity between 30% and 50% of the athlete’s VO2max. This is because aerobic exercise of the muscles that were not stressed during the previous work helps remove excess lactate. After long aerobic efforts, however, such active rest should not be employed. Active rest is effective even if the same muscle groups are exercised but using different movements. Everyday observation reveals that after a strength workout with squats and deadlifts, a brisk walk or a jog loosens one up sooner than just sitting around, and both the workout and the active rest involve the same muscles.
Recovery
Here are simple indicators of adequate recovery.
—Constant heart rate during the zone of effort well tolerated by the athlete
—Constant body mass
—Constant volume of urine per day (24 hours) with no more than 20% change (±20%)
—Lack of sediment or dark coloring in the urine after a workout or a return to normal within 24 hours after a workout
In the case of blood in the urine (hematuria), an athlete needs to drink lots of water; a low volume of urine (oliguria—reduction of urine secretion to between 100 and 400 ml in 24 hours) caused by sweating and by reduced blood flow through the kidneys also requires increased water consumption. The amount of water drunk after a workout should be such as to maintain the normal daily volume of urine. After long efforts in high temperatures, restoring water losses can take up to three days.
Gradually lowering heart rate values after the workout, particularly after an endurance workout, means the recovery is proceeding normally. If such a gradual lowering of the heart rate is interrupted by a sudden drop to lower values, it may be a sign of overtraining. A heart rate higher than average may signal exhaustion or fever.
A frequency of breath, measured in the morning, that is greater than normal for an individual may indicate a problem in the cardiovascular and respiratory systems.
Supercompensation
Rational doses of effort, followed by adequate rest, cause the body not only to compensate for the loss of energy sources and building materials used in the effort but to compensate in excess (supercompensate). Through supercompensation it is possible to increase the work capability of the body. The frequency of workouts should be such as to hit the phase of supercompensation often enough to ensure growth. If the rest breaks between workouts are too short or too long, the supercompensation phase is missed, and the next workout hits a phase of reduced work capability, either before or after the supercompensation.
In conclusion: Frequency of exercise should be dictated by the athlete’s recovery, not by the work schedule of an instructor or times of availability of a gym.
If interested, see Science of Sports Training: How To Plan And Control Training For Peak Performance for in-depth info on rest (pp. 17-22), on recovery (pp. 329-336), and on supercompensation (pp 66-73) and the article posted at https://www.stadion.com/muscle-fatigue.
This article is based on the book Science of Sports Training: How To Plan And Control Training For Peak Performance. Get it now and have all of the info—not just the crumbs!
