Despite the common occurrence of directional change in football, few studies have attempted to investigate the demands of players performing such movement patterns (Stevens et al., 2014; Akenhead et al., 2014; Dellal et al., 2010). The aim of the current thesis was to identify the physiological responses associated with performing directional changes in elite football players. The aim of the first study was to investigate the occurrence of directional change within an elite football team?s typical four-day training week and to determine the external load and subsequent physiological demands associated with performing such movement patterns. Five male elite football players were monitored during each session via global positioning system (GPS), accelerometry (ACC) and heart rate (HR). The data indicated that acceleration and deceleration (movements used to represent the occurrence of directional change) occurred frequently throughout each session of the training week but were found to be significantly higher for one particular training day when compared to all other remaining sessions (+22-43 (p <0.05). Although the external load as measured through ACC and the rate of perceived exertion (RPE) as measured through the modified Borg scale were greatest for this training day, they were not found to be significantly different when compared to all other training days. The physiological response however as indicated through HR was found to be significantly higher for this training day (+24-40 (p <0.05). These results would indicate that a higher cardiovascular response may be associated with training sessions that include more frequent changes in direction. Despite these findings the approach used to collect the physiological data within the study may have had several limitations. The biggest limitation was perhaps the influence of training variables other than movements relevant to directional change. There is therefore a need for an investigation which applies greater control of extraneous training variables during data collection. Such an approach would allow for a more precise interpretation regarding the physiological demands associated with performing directional changes. The aim of the second study was to investigate the external load and subsequent physiological demands of controlled intermittent protocols which included varying frequencies of 180 degree directional changes in elite football players. Thirteen male elite players were monitored via GPS, ACC and HR during protocols which involved one, three or seven change(s) in direction. In this study important extraneous variables such as the total running distance, speed of movement as well as the number and intensity of accelerations and decelerations performed were carefully controlled in an attempt to isolate and manipulate only the movement pattern. The results showed that external load as measured in gravitational force (g-force) was significantly greater for the protocol that involved seven directional changes when compared to the protocol which involved one (+32 or three (+24 directional changes (p <0.05). Participants resulting HR as measured through heart rate exertion (HRE) was also significantly higher for the protocol which involved seven directional changes when compared to protocols which involved one (+54 or three (+53 directional changes (p <0.05). The increase in the physiological response was further supported by a significant increase in RPE for the protocol which involved seven directional changes (5 $1) when compared to the protocols which involved only one (3 $0) or three (3 $1) directional changes (p <0.05). A positive correlation was found when comparing g-force with both HRE (r = 0.45, p <0.01) and RPE (r = 0.63, p <0.01). These results show that increasing the frequency of 180 degree directional changes through intermittent exercise protocols, increases the external load and physiological responses in elite football players. The current research indicates that directional change occurs frequently throughout an elite football team?s typical training week. Performing 180 degree directional changes increases the external load which may subsequently elevate the physiological and subjective responses. Careful consideration must therefore be placed on such movement patterns when designing training drills for elite football players throughout various days of the training week.
|Publication status||Published - 2015|