| Short-term match congestion (number of days between match exposures) | |||||
| ≤3 days | 4 days | 5 days | 6 days | 7–10 days | |
| Low long-term match congestion (≤4.5 hours)* | |||||
| Observations, n (%) | 2996 (18%) | 3049 (18%) | 1222 (7%) | 1991 (12%) | 7394 (44%) |
| Total match exposure, hours | 3504 | 3617 | 1544 | 2633 | 9657 |
| Mean match exposure time/observation, minutes (SD) | 70.2 (30.4) | 71.2 (29.8) | 75.8 (26.8) | 79.4 (23.1) | 78.4 (24.2) |
| Mean long-term match congestion, hours (SD) | 3.5 (1.0) | 3.5 (1.0) | 3.5 (1.0) | 3.6 (1.0) | 3.6 (1.0) |
| Muscle injuries, n (% of all injuries) | 37 (45%) | 47 (48%) | 24 (55%) | 23 (36%) | 79 (36%) |
| Muscle injury rate/1000 hours (95% CI) | 10.6 (7.7 to 14.6) | 13.0 (9.8 to 17.3) | 15.5 (10.4 to 23.2) | 8.7 (5.8 to 13.1) | 8.2 (6.6 to 10.2) |
| Muscle injury rate ratio† (95% CI) | Reference group | 1.23 (0.80 to 1.89) | 1.47 (0.88 to 2.46) | 0.83 (0.49 to 1.39) | 0.77 (0.52 to 1.14) |
| Medium long-term match congestion (>4.5 to ≤7.5 hours)* | |||||
| Observations, n (%) | 9275 (23%) | 9644 (23%) | 3942 (10%) | 4955 (12%) | 13 276 (32%) |
| Total match exposure, hours | 12 077 | 12 797 | 5350 | 6887 | 18 427 |
| Mean match exposure time/observation, minutes (SD) | 78.1 (24.1) | 79.6 (22.9) | 81.4 (20.1) | 83.4 (18.0) | 83.3 (18.0) |
| Mean long-term match congestion, hours (SD) | 6.5 (0.9) | 6.5 (0.9) | 6.5 (0.9) | 6.4 (0.9) | 6.3 (0.8) |
| Muscle injuries, n (% of all injuries) | 124 (40%) | 131 (44%) | 65 (46%) | 53 (33%) | 147 (34%) |
| Muscle injury rate/1000 hours (95% CI) | 10.3 (8.6 to 12.2) | 10.2 (8.6 to 12.1) | 12.1 (9.5 to 15.5) | 7.7 (5.9 to 1 0.1) | 8.0 (6.8 to 9.4) |
| Muscle injury rate ratio† (95% CI) | Reference group | 1.00 (0.78 to 1.27) | 1.18 (0.88 to 1.60) | 0.75 (0.54 to 1.03) | 0.78 (0.61 to 0.99) |
| High long-term match congestion (>7.5 hours)* | |||||
| Observations, n (%) | 9 907 (36%) | 8 666 (32%) | 2 899 (11%) | 2 174 (8%) | 3 770 (14%) |
| Total match exposure, hours | 13 553 | 12 084 | 4050 | 3058 | 5338 |
| Mean match exposure time/observation, minutes (SD) | 82.1 (19.9) | 83.7 (18.2) | 83.8 (16.7) | 84.4 (16.3) | 85.0 (15.4) |
| Mean long-term match congestion, hours (SD) | 9.4 (1.1) | 9.3 (1.0) | 9.2 (1.0) | 9.0 (0.9) | 8.8 (0.8) |
| Muscle injuries, n (% of all injuries) | 122 (37%) | 125 (43%) | 36 (39%) | 19 (29%) | 40 (38%) |
| Muscle injury rate/1000 hours (95% CI) | 9.0 (7.5 to 10.7) | 10.3 (8.7 to 12.3) | 8.9 (6.4 to 12.3) | 6.2 (4.0 to 9.7) | 7.5 (5.5 to 10.2) |
| Muscle injury rate ratio† (95% CI) | Reference group | 1.15 (0.90 to 1.47) | 0.99 (0.68 to 1.43) | 0.69 (0.43 to 1.12) | 0.83 (0.58 to 1.19) |
Values in bold indicate significant difference compared with ≤3 days.
*Long-term match congestion denotes total registered match exposure for the individual during 30 days.
†Injury rate ratios were analysed between long-term match congestion groups using >7.5 hours as reference group and between short-term match congestion groups using ≤3 days as reference.