# New Perspectives in the Development of the Artificial Sport Trainer
## 2 Materials and Methods
### Basics of Sport Training  
The goal of sport training is developing the mental and physical performance of an athlete's body. The mental performance refers to the motivation and attitude of the athlete to sport training as a whole, while the physical performance on the influence of particular workouts they have to specific physiological categories of an athlete's body, like heart, lungs, blood, and muscles. The benefit of sport training is reflected in the athlete's fitness, and determines his/her race readiness, i.e., how competitive an athlete can be in the real competition. According to a theory of sport [23], a training process follows four principles:  
* progressive overload,
* specificity,
* reversibility,
* individuality. The first principle asserts that only increasing the physical stress (i.e., overload) is a key for improving an athlete's fitness. Obviously, a human body responds to the stress either positively or negatively. In the first case, the human body reacts to the overload with fatigue, while, in the second, with overtraining that, typically, leads to injuries. The fatigue can be defeated by resting, while injuries demand recovery and, usually, also the help of medical staff. The specificity refers to effects caused by a particular workout on the particular physiological categories of an athlete's body. In line with this, two categories are distinguished: central and peripheral. The former pertains to improving fitness of the heart, lungs, and blood, while the latter to muscles. The principle of reversibility indicates that the fitness has been decreasing with the inactivity of the athlete. No training, no fitness improving. Also, reduced training results in losing fitness. The last principle says that each athlete is unique, and therefore must be treated by the sport trainer as an individual, and each individual needs different treatment to achieve the same level of fitness as the other. Athletes train according to training plans prepared by either sport trainers manually, or the computer programs automatically. The training plans depend on three so-called training load indicators: duration, intensity, and frequency. Duration specifies how long an athlete must maintain the intensity at high level in overcoming the particular workouts. Indeed, intensity decreases with increasing the duration. The frequency refers to the issue of how many times the specific workout must be repeated in a specific time period. Sport training consists of four phases: planning, realization, control, and evaluation [17]. In the planning phase, workouts are prescribed for athletes in training such that their sequence ensures them the optimal race readiness at the training period by simultaneous development of all physiological categories. The realization phase is dedicated for implementing the sport training plan on a daily basis. The quality of the performed sport training is controlled by measuring the achievement of the athlete during the workout. The measuring was conducted manually by sport trainers in the past, using, for instance, sport watches for measuring time, tapes for measuring distance, and the amount lifted during weight lifting. Recently, modern wearable devices and sport trackers have helped sport trainers by monitoring the results achieved during sport training automatically. The evaluation phase is, typically, performed after finishing some sport training period (e.g., a season). In this phase, an analysis is performed of the results achieved in competitions, and modifications in training are outlined to improve the race readiness of the athlete in the next period. The AST [17] has performed all four phases sequentially. However, the advances of technology, especially IoT, allows for new perspectives in sport training. On the one hand, new sensors have been emerging that enable sport trainers to monitor their athletes according to new training load indicators, while, on the other hand, the existing sensors have become smaller and more accurate.