# Understanding the Influence of the Head Coach on Soccer Training Drills--An 8 Season Analysis
## 2 Materials and Methods
### Procedures  
Players' external loads during normal training sessions were quantified via MEMS (Micromechanical Electrical Systems; Optimeye S5, Catapult Sports, Melbourne, Australia), which were worn between the scapulae within a customized, tight-fitting neoprene garment. The Optimeye S5 unit (Firmware version 6.72-6.88) contains a 10 Hz Global Positioning Systems (GPS) chip alongside a tri-axial piezoelectric linear accelerometer [Kionix: KXP94] sampling at 100 Hz. A GPS sampling rate of 10 Hz has demonstrated good reliability [coefficient of variation; CV% = 2.0-5.3%] for assessing instantaneous velocity [19] and small-to-moderate typical errors of the estimate [1.87%-1.95%] when measuring Sprint speed [19]. The accelerometers within the MEMS devices have also produced good reliability [CV% = 0.9-1.1%] during laboratory and field tests [20]. Units were calibrated before each season using the manufacturer's calibration jig and to the manufacturers recommended values. Calibration values were monitored regularly during the study period to ensure that the accuracy of each conformed to the manufacturer's guidelines. Each player wore the same unit throughout the study period to avoid inter-unit variation. In accordance with the manufacturer's recommendations, MEMS were activated outside for \(\sim\)15 min before each session commenced to minimize the risk of erroneous data arising from poor GPS signal quality [16; 21]. Data was downloaded within the same software version [Catapult Sprint 5.1.7] and were only included if the number of satellites exceeded six and the horizontal displacement of positioning was \(<\)1.5 [16; 21]. All players and head coaches were familiar with these procedures, which were used as part of their routine monitoring practices. The training drills completed throughout the study period were grouped into six categories according to their primary training objective. These categories are defined as 'conditioning' (CON), 'position-specific training' [PS], 'possession' (POS), 'SSG, 'tactical' (TAC) and 'technical' (TEC) drills, with the definitions of each below. The definitions and categories were selected based upon the most used terminology within the previous research into different drills used in soccer and coaching manual resources [3; 13; 22]. Once the definitions were written, these were then shown to each of the head coaches involved within the project to ensure that these definitions were appropriate. **Conditioning [CON]--**Drills designed specifically to exercise the player's physical capabilities. This will include drills with or without the ball, which are designed to exercise a specific part of the players physical performance as the main objective. **Position-Specific training [PS]--**Drills where the demands of the exercise are aimed at specific units of the team, with positions separated and coached as a unit [goalkeeper, defenders, midfielders and forwards] or an individual. **Possession [POS]--**Drills designed to mimic similar demands of match play, with the aim of the session to keep the ball away from the opposing team, with no goals to score in. Small-Sided Games [SSG]Drills designed to mimic similar demands of match play, with the aim of the session to keep the ball away from the opposing team, with no goals to score in. Tactical [TAC]Drills designed to educate the players in the tactical roles they play within a team shape. These include set-pieces and open play team shape. Technical [TEC]Drills aimed to specifically work on a skill aspect of soccer such as passing, shooting, defending and foot work with a ball, working as an entire group. These categories were established using multiple resources. In addition to drill duration, the variables profiled were Total Distance, HSR [defined as distance covered at a speed \(>\)5.5 m\(\cdot\)s\({}^{-1}\)], Sprint distance covered [\(>\)7 m\(\cdot\)s\({}^{-1}\)].