5A 111 INCREASING WORKLOAD RELATES TO INJURY RISK IN RUNNING The z-score for the acute workload, the chronic workload and the weekly ACWR of the individual runners were calculated to indicate whether the observed value was above or below the average for the individual. The acute workload, chronic workload and the ACWR were classified accordingly [11], [12]. The classifications consisted of the following week categories: (i) Very low, (ii) Low (iii) Moderate low, (iv) Moderate high, (v) High, (vi) Very high. The thresholds of categories based on the corresponding the z-scores are presented in Table 2. Table 2. Workload classifications and boundaries. Workload category z-Score Acute Workload AU Chronic Workload AU Weekly ACWR ratio Very low Low Moderate Low Moderate High High Very High ≤ -2.00 -1.99 – -1.00 -0.99 – -0.01 0.00 – 0.99 1.00 – 1.99 ≥ 2.00 ≤ 3810 3811 – 8170 8171 – 10880 10881 – 14998 14999 – 18052 ≥ 18053 ≤ 6297 6298 – 9158 9159 – 10832 10833 – 13485 13486 – 19675 ≥ 19676 ≤ 0.24 0.25 – 0.68 0.69 – 1.10 1.11 – 1.53 1.54 – 1.96 ≥ 1.96 Workload difference category z-Score Weekly ACWR ratio difference Fortnightly ACWR ratio difference High decrease Moderate decrease Low decrease Low increase Moderate increase High increase ≤-2.00 -1.99 – -1.00 -0.99 – -0.01 0.00 – 0.99 1.00 – 1.99 ≥ 2.00 ≤ -0.57 -0.56 – -0.24 -0.25 – 0.05 0.05 – 0.62 0.63 – 1.14 ≥ 1.15 ≤ -0.53 -0.56 – -0.27 -0.27 – 0.10 0.10 – 0.78 0.79 – 1.29 ≥ 1.30 AU=Arbitrary Units ACWR = Acute:Chronic Workload Ratio The week-to-week ACWR difference is the difference of the ACWR between two subsequent weeks. The fortnightly ACWR difference is the difference between the average of the ACWR of two subsequent weeks compared with average of the ACWR of the following two subsequent weeks. The week-to-week and fortnightly ACWR difference were categorized in the following week-to-week and fortnightly AWCR difference categories:(i)High decrease,(ii) Moderate decrease, (iii) Low decrease, (iv) Low increase, (v) Moderate increase, (vi) High increase [11, 12]. The thresholds of the weekly and fortnightly difference categories were based on the distribution of the z-scores. The weekly and fortnightly difference categories and the corresponding thresholds are presented in Table 2. 2.5. Determining association The association between workload and injury risk was determined for the workload categories related to the four-week blocks preceding the injury. The risk of sustaining
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