# Understanding the Influence of the Head Coach on Soccer Training Drills--An 8 Season Analysis
## 4 Discussion  
The aim of this study was to quantify the external physical loads elicited by different categories of training drills performed by professional soccer players while assessing the influence of manager identity and playing position. On average, drills lasted \(\sim\)14 min and elicited distances covered and HSR of \(\sim\)1000 m and 40 m, respectively. However, all physical variables differed as a function of drill type and manager identity, with playing position influencing all variables except for relative sprint distance. Acknowledging that the demands of training may also be influenced by factors such as the specific task constraints [3, 13], knowing the external load responses associated with each training drill may be valuable for practitioners as a guide. Based on the methods used in this study, practitioners may also find it beneficial to create their own drill data sets to help support their own team and individual specific training prescriptions [3], while accounting for the influence of any coaching staff changes. Development of technical and tactical skills typically represent the primary focus of in-season training [3, 9, 11], with specific session content being mostly determined by head coaches or senior coaching staff [10]. However, soccer players also require well-developed aerobic and anaerobic energy systems to cope with the varied demands of match-play in addition to adequate lower-limb strength and range of motion to perform frequent high-speed actions such as sprint, jumping and changes of direction [1, 3]. It is therefore imperative that preparation programs expose players to a volume and intensity of stimulus that can elicit [or at least maintain] these necessary adaptations. The current study observed that TAC were typically the longest training drills, although by far the greatest absolute and relative HSR and sprint distances were elicited by CON. Conversely, absolute acceleration and deceleration outputs were highest for SSG and TAC drills (Table 1), whereas SSG and CON drills had the highest relative outputs. Given the consistency of these differences within head coaches, practitioners may use the current information to consider the implementation of these drill types within the microcycle. This information may also be valuable when designing 'top-up' training sessions for substitutes or unused squad members in an effort to compensate for reductions in match-day loading when compared with players who complete a full match [22, 25]. Subject to the existence of practical and regulatory restrictions [22, 25], practitioners may select the type of drill to implement during top-up sessions based upon recorded deficits in specific external load variables. Practitioners have adopted the use of stimulating the most demanding sections of match-play to create specificity within an individual's training program/ top-up sessions [22, 25]. In combination with the proposed method of monitoring different drill categories, practitioners and coaches can help prescribe relevant training drills for these type of sessions and ensure players training is specific to their external training loads [22]. Although the overall proportion of training drills from each category was CON: 10%, PS: 4%, POS: 27%, SSG: 33%, TAC: 11% and TEC: 15%, substantial variation was observed between managers. For example, the proportion of training drills accounted for by SSG ranged from 22-44% for each ofthe nine head coaches whilst the contribution from TAC varied between 6-28%. Such observations likely reflect between-head coach differences in training philosophies or priorities and highlight that a change in staff could profoundly affect the loading patterns of individual squad members. As each drill category elicits a distinct external load profile, sudden changes in training composition may produce concomitant fluctuations in overall loads. Moreover, it is notable that head coach identity influenced all external load variables even when drill category was held constant.