*This is an excerpt from our textbook.
When you consider that a single training method will affect individuals differently, depending on their fitness level and genetic variation, the task of designing a training plan may feel complicated. In order to take an individual’s abilities from point A to point B you have to not only consider your methodology, but the individual differences of the person you are training. Having a solid understanding of how training effects work will contribute a great deal to your ability to do this. Training effects can be classified into four major categories: Neurological, Metabolic, Structural, and Cardiorespiratory. We’ll begin with what is probably one of the most complex and comprehensive training effects: neurological adaptations.
The reason that a new movement feels “hard” or that lifting more weight feels “heavy” is because you are uncoordinated. You are uncoordinated because your brain and nervous system have not yet figured out how to efficiently recruit muscle fibers to master a new complex movement or move a heavy load. It is a well-established that most strength gains early in a training program are the result of increased neurological coordination. As you practice lifting heavy loads with consistent form, your nervous system adapts to be able to recruit more muscle fiber units with less stimulation. In other words, it becomes more efficient.
Other training methods also take advantage of neurological adaptations. Increased speed, agility, coordination, and reaction time are the result of practicing complex movements at their required intensities. Cardiorespiratory, structural, and metabolic adaptations also support these training effects, while increased neurological efficiency plays a dominant role in muscle fiber recruitment. Neurological adaptations are also responsible for spatial awareness and proprioception; one’s ability to react and adjust to one’s environment. For example a cross country runner needs to be able to use visual and sensory cues to adjust to obstacles and uneven surfaces.
The take-home lesson here is that a large number of training adaptations result simply from learning how to move correctly at the required intensities. In other words, whether you are developing strength, speed, agility, or balance, practice makes perfect.
Neural coordination allows proper movement and recruitment to take place, but there are other training effects that support the efforts of the nervous system. Efficient muscle fiber recruitment makes one stronger, but the body must also adapt structural changes to withstand increased loads, intensities, and multi-directional forces that are a part of advanced training methods and sport. Structural changes include: increased bone density, connective tissue proliferation around individual muscle fibers, strengthening of supportive tendons, ligaments, and fascia, and an increase in the number of capillaries within the muscle. The muscle fibers themselves can also increase in size and convert from one type to another to support different types of efforts. Structural changes take a relatively long time to develop and training plans must allow for this development both for optimal results and injury prevention.
In addition to structural changes, the muscles must be able to efficiently use oxygen and nutrients to fuel efforts at the required intensities. Muscle cells conditioned to strength or power training will develop an increased ability to store glycogen. Muscle cells adapted to endurance training have a greater capacity to take in a utilize oxygen (VO2 max) through increases in enzymes used for aerobic metabolism. This enables the cells to use fat as a substrate at higher exercise intensities. An adaptation associated with this increase in VO2 max is an increase in the number of mitochondria within the muscle fiber. Mitochondria are the cellular structures responsible for converting cellular nutrients into ATP via aerobic metabolism. Simply put, the muscle fibers are able to supply and utilize more fuel for long-term efforts and/or access fuel more immediately and repeatedly for maximum strength and power efforts. Metabolic adaptations are relatively quick to develop, but rely on other systems for optimal expression. In other words, your conditioning is only as good as your strength and aerobic base.
Lastly, cardiorespiratory adaptations include: Diaphragm endurance, circulatory efficiency and blood volume increases, increase in vital capacity and efficiency of lungs, and physiological (not pathological) hypertrophy or enlargement of the heart. This means that the heart actually becomes bigger and stronger and can pump larger volumes of blood. Many cardiorespiratory adaptations involve structural changes such as capillary proliferation in the skeletal muscle, development of the muscles that support breathing, and increased heart function. Although the metabolic changes that enhance aerobic fitness can occur within a relatively short period of time, the changes that support long-term development of an aerobic base take much longer to improve.
All four of these adaptations occur in individuals participating in training programs. However, the most dramatic adaptations occur in untrained individuals in the first few months, or even years of training. Strength, power, coordination, and endurance all improve dramatically with the simplest of training input in the untrained person. Your average untrained, or under-trained, individual will benefit from increased cardiovascular conditioning, muscular endurance, strength, and coordination from participating in a training program. However, the less intelligent the programming, the more rapidly the individual may plateau and/or begin to experience overuse injuries and strength imbalances. Although “everything works for a while”, it is always good to have a well-thought out plan. It is also necessary to consider that the structural changes that support increased coordination take longer to develop than other adaptations and these must be sufficient to withstand training loads and volume in order to prevent injury.