The Effects of Training Load on Match Performance and Injury Incidence in an English Professional Soccer Club

Training load can be divided into 2 categories: internal and external training load. External training load is the physical stress work done by the athlete. External training load can be measured by the use of global positioning system (GPS) and video-based time motion analysis. Internal training load is the physiological responses from training sessions. It can be measured by the use of heart rate monitors and rate of perceived exertion. Monitoring training load can be used to measure the players' readiness for matches and as a precautionary measure to reduce overreach from training sessions. The aim of this thesis are to quantify training periodisation practices employed by a professional football club throughout a competitive season, determine the changes to microcycle training plan according to the number of matches in a week and the neuromuscular response during weekly microcycles of different football training and match loads among professional football players and to evaluate the eccentric hamstring strength and injury occurrence in relation to training load data throughout the competitive season.

Study 1 aimed to quantify training periodisation practices employed by a professional football club throughout a competitive season. Initially, 20 players agreed to take part in the study, although only 12 players provided sufficient data to be included within the study. Training data was recorded via GPS across the competitive season, sub-divided into 4 different stages (each sub-divided into two 5-week blocks; early and late stage). Countermovement jump height was recorded for all players in order to assess their level of neuromuscular fatigue. Significant differences were observed in total distance covered (p = 0.045, effect size = 0.385) and high-speed distance covered (p = 0.001, effect size = 0.264) across the different stages of the season. There were no significant changes were observed in the training load as measured by the accumulated New Body Load (p = 0.085). A sub-analysis was conducted to explore the impact of fixture congestion on player training load by comparing weeks with 1 match, vs weeks with 2 matches. Significant differences were observed in total distance covered (1 match = 14076.16 ± 1569.24 m vs. 2 matches = 7874.35 ± 1923.01 m; t (3) =3.571, p = 0.038, 95% Confidence Interval of Difference [674.40 m to 11729.23 m], effect size = 3.53), high-speed distance covered (1 match = 781.49 ± 109.89 m vs. 2 matches = 413.99 ± 91.87 m; t (3) = 4.445, p = 0.021, 95% Confidence Interval of Difference [104.39 m to 630.60 m], effect size = 3.63) and accumulated New Body Load (1 match = 281.82 ± 35.36 AU vs 2 matches = 135.93 ± 12.02 AU; t (3) = 11.78, p = 0.001, 95% Confidence Interval of Difference [106.47 AU to 185.31 AU], effect size = 5.52) for training sessions in weeks that players were preparing for 1 match vs 2 matches. No correlation was found between the total distance covered (r = -0.001; p = 0.995), high-speed distance covered (r = 0.07; p = 0.547) and New Body Load (r = 0.101; p = 0.386) with countermovement jump height. It was concluded that there was a lack of manipulation in training sessions throughout the season. However, there were efforts to reduce the training load on weeks with 2 matches. Hence, alteration in training microcycles is important for players to be optimally prepared and recuperated for the following match.

Study 2 aimed to evaluate the eccentric hamstring strength and injury occurrence in relation to training load data throughout the competitive season. Players were divided between those who had suffered hamstring injuries (n = 6) and those that did not during the season (n = 14) over the course of the season. They were required to perform isometric Nordic hamstring curl every week after a training session. No statistical differences were observed between the Nordic break-point angles (hamstring strength) of the two groups (p = 0.299). No significant changes were observed in the acute: chronic workload ratios between the two groups prior to injuries of the injured group (p = 0.316). It was concluded that eccentric hamstring strength and the acute: chronic workload ratios cannot be used to predict non-contact injury incidences.

To conclude, the present results suggest that a lack of manipulation to training load may not reduce match running performances. However, coaches and sports scientists still manipulate and periodise training for optimal preparation for matches, especially in weeks with more matches. The use of eccentric hamstring strength tests alone and acute: chronic workload may not be suitable to predict non-contact injuries among the players.