# Understanding the Influence of the Head Coach on Soccer Training Drills--An 8 Season Analysis
## 1 Introduction  
Soccer is an intermittent, primarily aerobic activity [1], with bouts of high intensity efforts such as high speed running (HSR) Sprinting and accelerations/decelerations performed throughout [2]. To ensure that players are prepared to cope with the physical demands of match-play whilst minimizing the risk of injury, it is imperative that training sessions provide a stimulus, such as training load, that is sufficient to elicit adaptations [3]. Conversely, excessive training loads or large fluctuations in a player'sphysical loading patterns can increase injury-risk in team sport players [4; 5; 6]. Ongoing monitoring and manipulation of a player's physical loads within the context of a periodized preparation program therefore represents a fundamental task for applied practitioners working in soccer [7]. Soccer training activities are aimed to develop the physical, technical and tactical aspects ready for match play [3]. Technical and tactical objectives represent the primary focus of in-season training programs, as training prescription may be determined predominantly by the team's technical coaches based on the perceived technical/tactical needs of a squad [8; 9; 10]. As these training drills or sessions are based around team cohesion/performance, they may not elicit the specific physical outputs for an individual player intended by the practitioner [9; 11]. Knowledge of the typical physical output elicited during different types of training drills may allow practitioners to estimate a player's upcoming training loads. For example, during single game weeks, professional soccer teams seek to maximize player readiness by typically prescribing their most physically demanding training sessions \(\sim\)3-5 days in advance of the upcoming fixture [8; 9; 10]. A substantial reduction in loading is then provided during the \(\sim\)24-48 h before the match to allow sufficient recovery time [8; 9; 10]. Although this form of within-microcycle periodization is commonplace within professional soccer, researchers investigating this topic have often reported loading patterns as a function of days for example, ['match day minus one, etc.] without reporting the specific training drills used [8; 9; 10]. Substantial differences in internal and external training loads have been reported during small-sided games (SSG) compared with straight line running activities [12] and between SSG conducted under different constraints for example, variations in pitch dimensions, the number of players involved, etc. [3; 13]. As these findings highlight the role of training session design in modulating the type and magnitude of the stimulus provided, practitioners and coaches may benefit from information regarding the physical output associated with a wider variety of different training drills. Such insights could assist the design of varied training programs that provide the desired physical, technical and tactical stimulus in advance of the upcoming fixture or series of fixtures. Frequent changes in coaching staff is a characteristic of professional soccer. Given the head coaches role in designing training programs [10], a change in personnel may influence a player's physical outputs during training and match-play, depending on the head coaches instructions for the team and each playing position. A study of 36 teams across 17 countries reported that the head coach's leadership style was associated with player injury rates [14], whilst increases in the incidence of injury have been observed following a change of head coach in Turkish professional soccer [15]. Despite an overall injury incidence rate of 2.3 muscle injuries per 1000 h of training and match-play exposure, this value increased to rates of 5.3 and 4.5 in the 14 days and 30 days after a change in head coach, respectively [15]. Given the relationship between fluctuations in training load and increased injury-risk [4; 5; 6], it is possible that such observations reflect substantial changes in players' physical outputs accompanying a change in staff.