The development of a soccer-specific high-intensity intermittent running protocol
Recovery from high-intensity exercise in soccer is very important for players to be able to cope with the physical demands of match-play. Evaluation of soccer players ability to perform repeated high-intensity running should therefore be of particular importance to coaches. The aim of this thesis was to develop and apply a high-intensity intermittent running protocol where sub-maximal and maximal components of soccer-specific endurance could be assessed. In Study 1 and Study 2, initial pilot work on the 15-50 protocol and then the 15-30 protocol, two high-intensity intermittent running protocols, were examined for reliability and physiological responses. It was reported that a large learning bias was present in both protocols reflected by performance improvements between trials. These improvements were supported by an improved running economy on the test. The physical load was higher in the maximal stage compared to the sub-maximal stage in both protocols with both aerobic and anaerobic energy production highly simulated as a result of a manipulation of the exercise and rest periods from the sub-maximal stage. It was concluded that several familiarisation sessions were needed on both protocols especially for recreational players to remove any learning bias. The structure of the 15-50 protocol may restrict its application to soccer and may be more suitable as an interval conditioning drill than as a test. The structure and the physiological responses in the 15-30 protocol make it a more practical assessment of soccer-specific endurance. The relationship between the 15-30 protocol and physical performance during match-play, soccer-specific field test performances and aerobic endurance measurements in young professional soccer players was examined in Study 3. There was no relationship between any of the soccer-specific field tests and indices of physical performance during match-play. A significant correlation was reported between maximal oxygen consumption and distance covered in the maximal stage of the 15-30 protocol. No relationship was found between other standardised field tests used in soccer and the 15-30 protocol. It was concluded that physical performance during match-play is highly variable which makes evaluation of the physical capacity of soccer players very difficult. Maximal high-intensity exercise performance was highly influenced by maximal aerobic power. It is plausible that higher aerobic endurance would have facilitated a rapid recovery between high-intensity bouts in the maximal stage. In Study 4 and Study 5, the sensitivity of the 15-30 protocol to pre-season and in-season training periods was investigated. The in-season training period consisted of weekly additional aerobic interval training. Expected improvements in performance were observed at the end of the six-week pre-season training period in both the 15-30 protocol and the Yo-Yo intermittent recovery test in young professional soccer players. Small increases in maximal oxygen consumption as well as a greater increase in 15-30 protocol performance were also reported after the in-season training. It was concluded that significant physiological adaptations can be obtained as a result of soccer-specific training periods during the season. The physiological adaptations are more likely to be attributed to peripheral factors than central factors. A new unique high-intensity intermittent running protocol has been developed during these studies. The physiological mechanisms which govern test performance seem to be different from responses to other soccer-specific field tests. Evaluation of soccer-specific endurance performance is complex since physical performance is influenced by numerous variables.