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Introduction
Exercise is now recognised as a major preventive risk factor for the majority of diseases and requires aggressive promotion by health authorities. 1 However, exercise prescription is not as straightforward as it might appear, as sudden increases in physical activity and sport are associated with injuries, particularly tendon injuries. 2-5 The current surveillance and understanding of the causes of gradual onset (sometimes termed 'overuse') injuries associated with sport and exercise are poor, 6 7 making it difficult to recommend ideal amounts of exercise. It is particularly difficult to prospectively assess loading risk factors for tendon injuries, as keeping detailed long-term records of tendon loading is particularly arduous and expensive. Understanding risk factors for gradual onset tendon injuries may be more easily improved by following elite athletes 8 for whom detailed loading records are often kept. However, the difficulty with assessing elite athletes is that the majority are subjected to a high, but fairly constant workload, increasing the challenge of assessing the effects of workload changes on injury risk.
Of the major global team sports, cricket has both a high rate of gradual onset injuries and great variations in player workload. 9 Whereas most team sports are played over a short and fixed duration, cricket is played in a variety of forms. Balls in cricket are delivered in groups of six, called 'overs'. Therefore, 20 overs in cricket consist of 120 balls. One-innings matches are played with a maximum number of set overs (usually 20 or 50 overs at international level) to be bowled in each team's (single) innings, with each bowler being allowed to bowl a maximum number of overs (usually 20% of a team's total overs). Limited overs matches with 20 overs per team are often referred to as 'T20' matches. First class cricket matches (including international Test matches) are played with unlimited overs lasting 4 or 5 days (with two innings per team). The length of an innings in first class cricket is not fixed, which leads to great variation in workloads. In these matches, bowlers can sometimes be required to bowl in excess of 50 overs (300 balls) over the 4-5 days. In addition, the international cricket calendar is fairly unstructured, with no fixed number of matches of the various varieties...