This is an excerpt from Science and Practice of Strength Training-3rd Edition by Vladimir M. Zatsiorsky,William J. Kraemer & Andrew C. Fry.
Overtraining is a commonly used term, but in many cases is used incorrectly. In the past, many individuals have reported being overtrained at some point in their training histories, including over 70% of those surveyed in one report. But what exactly is overtraining? How is it defined? One important concept to keep in mind is that overtraining is the process, while overtraining syndrome is the result. In other words, the process of overtraining involves the volumes and intensities of the training being performed that contribute to the inability of the human body to adequately recover. The net result is the overtraining syndrome, a myriad of symptoms and conditions that collectively contribute to impaired performances. Many of these signs and symptoms will be discussed in more detail later in this chapter, but the central concept in the overtraining paradigm is that performance is impaired.
Over the years, many terms have been used synonymously with overtraining, including those listed in table 9.1. Although not an exhaustive list, it becomes readily apparent that this topic can be confusing. To help address this issue, several prominent international sport and exercise science organizations created a joint task force to help define overtraining, to establish what we know and don't know about it, and to determine what needs to be done to better understand this phenomenon. The original document was published in 2006 and helped to define and clarify the problem. A subsequent version was published in 2013 and presented the current base of knowledge as applied to numerous sport and exercise settings, as well as to specific physiological systems and the psychology of overtraining. These documents made clear that overtraining is accompanied by impaired performances, and recovery requires weeks, months, or longer.
If recovery can be attained in a matter of one or two weeks, this is called overreaching. When subsequent performance is enhanced after overreaching, it is called functional, and is often a desired training strategy to optimize later performance. When recovery from overreaching takes longer, and produces no supercompensation or enhanced performance, it is called nonfunctional. The goal of this chapter is to present these concepts as they pertain specifically to resistance exercise and strength training, and to present some practical applications based on the science as it is currently understood.