THE BIOMECHANICAL, PHYSIOLOGICAL AND RECOVERY RESPONSE TO THE EXTRA-TIME PERIOD OF MALE SOCCER

Soccer matches are traditionally contested over 90 min. However, when matches are tied in the knockout-phase of some major tournaments, there is an additional 30 min extra-time (ET) period. Aspects of ET have been investigated but knowledge of the biomechanical, physiological and recovery responses to ET is limited. The overarching aim of this thesis was to assess the biomechanical, physiological and recovery responses to 120-minutes of soccer-specific exercise. The specific objectives were to i) review the ET literature and identify gaps in knowledge, ii) evaluate the reliability of a 120-min treadmill-based soccer-specific exercise protocol, iii) investigate the physiological and iv) biomechanical responses to 120-min of soccer-specific exercise, v) explore practitioner views and practices on recovery following ET matches, and vi) assess the recovery responses following 120-min of soccer-specific exercise. To identify gaps in the literature, a systematic review of the ET period of soccer was conducted. The systematic review revealed a dearth of robust evidence concerning biomechanical measures, direct assessments of substrate utilisation, and controlled recovery assessments, during and following 120-min of soccer-specific exercise. The original contribution to new knowledge relates to the critical and systematic appraisal of current ET literature and investigations that explore under researched facets of ET, including biomechanical, physiological and recovery responses.

The four studies of the thesis are distinct in scope but integrate to form a series of studies that are common in their approach to evolving understanding of the ET period of soccer. Study one assessed the test-retest reliability of a validated soccer-specific exercise protocol. The protocol demonstrated moderate-to-very strong reliability. PlayerLoad™, respiratory exchange ratio (RER), and differential ratings of perceived exertion (d-RPE) were also assessed in the study. PlayerLoad™ and d-RPE values increased during ET, and a shift towards fat oxidation was observed during this additional 30-min period. For study two, lower-limb muscle excitation and peak torque responses were assessed over 120-min of soccer-specific activity. Muscle excitation of the rectus femoris was reduced during ET, and decrements in eccentric peak torque of the knee flexors were observed post 120 min versus pre-exercise. Study three surveyed practitioners’ perceptions and practices related to player recovery following ET. Most practitioners specified that competing in 120 min of match-play delays the time-course of recovery (88%), that practices should be adapted following ET matches (82%) and promote further research on recovery following this additional 30 min period (88%). For study four, recovery was assessed following 90- and 120-min of soccer-specific activity. Creatine kinase activity was higher following the 120 min trial, but functional and perceptual recovery measures were not further impacted following ET. In conclusion, the ET period has a detrimental impact on biomechanical and physiological measures and increases creatine kinase activity in the days following 120-min of soccer-specific exercise. The impact of ET on recovery and subsequent performance should be investigated following 90- and 120-min of actual match-play.