The association between increase* in handball load and risk of shoulder-related injuries in youth handball stratified by shoulder assessments
| Stratum 1 | Stratum 2 | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| SI | W at risk | HR (95% CI) | p Value | SI | W at risk | HR (95% CI) | p Value | Ratio between strata | p Value | |
| Scapula | Normal control | Dyskinesis | ||||||||
| <20% | 16 | 4611 | 1 (ref) | 10 | 2472 | 1.3 (0.6 to 2.8) | 0.54 | |||
| 20–60% | 3 | 1623 | 0.6 (0.2 to 2.0) | 0.37 | 8 | 854 | 2.7 (1.1 to 6.5) | 0.02 | 4.8 (1.3 to 18.3)† | 0.02 |
| >60% | 8 | 1350 | 1.8 (0.7 to 4.3) | 0.14 | 6 | 836 | 2.3 (0.9 to 6.1) | 0.10 | 1.3 (0.4 to 3.7) | 0.66 |
| <−2 SD | 1 | 162 | 1.9 (0.2 to 15.0) | 0.55 | 0 | 106 | NA | NA | ||
| 4 weeks | 8 | 1501 | 2.1 (0.2 to 20.5) | 0.51 | 5 | 791 | 2.5 (0.2 to 25.9) | 0.44 | 1.2 (0.4 to 3.7) | 0.78 |
| Rot str. 0 | >0.75 | ≤0.75 | ||||||||
| <20% | 17 | 4892 | 1 (ref) | 8 | 1989 | 1.2 (0.5 to 2.7) | 0.72 | |||
| 20–60% | 7 | 1748 | 1.1 (0.5 to 2.7) | 0.23 | 2 | 687 | 0.9 (0.2 to 3.8) | 0.86 | 0.8 (0.2 to 3.8) | 0.77 |
| >60% | 10 | 1492 | 1.9 (0.9 to 4.3) | 0.11 | 4 | 634 | 1.9 (0.6 to 5.9) | 0.24 | 1.0 (0.3 to 3.3) | 0.99 |
| <−2 SD | 1 | 186 | 1.8 (0.2 to 14.1) | 0.58 | 0 | 82 | NA | NA | ||
| 4 weeks | 7 | 1447 | 1.8 (0.2 to 14.1) | 0.60 | 8 | 713 | 4.3 (0.4 to 40.6) | 0.21 | 2.4 (0.8 to 6.6) | 1.00 |
| Rot str. 30 | >0.75 | ≤0.75 | ||||||||
| <20% | 20 | 5524 | 1 (ref) | 5 | 1255 | 1.1 (0.4 to 3.0) | 0.78 | |||
| 20–60% | 5 | 1974 | 0.7 (0.3 to 1.8) | 0.45 | 4 | 439 | 2.7 (0.9 to 8.2) | 0.07 | 4.0 (1.1 to 15.2)† | 0.04 |
| >60% | 7 | 1703 | 1.2 (0.5 to 2.8) | 0.74 | 6 | 376 | 4.9 (1.9 to 12.7) | 0.00 | 4.2 (1.4 to 12.8)† | 0.01 |
| <−2 SD | 1 | 221 | 1.5 (0.2 to 11.5) | 0.70 | 0 | 36 | NA | NA | ||
| 4 weeks | 8 | 1584 | 2.1 (0.2 to 19.9) | 0.51 | 5 | 540 | 3.9 (0.4 to 38.9) | 0.25 | 1.8 (0.6 to 5.5) | 0.29 |
| Abd str. | >0.065 N/kg | ≤0.065 N/kg | ||||||||
| <20% | 15 | 3757 | 1 (ref) | 11 | 3277 | 0.9 (0.4 to 1.9) | 0.72 | |||
| 20–60% | 6 | 1330 | 1.1 (0.4 to 2.9) | 0.81 | 4 | 1144 | 0.9 (0.3 to 2.7) | 0.85 | 0.8 (0.2 to 2.9) | 0.73 |
| >60% | 7 | 1224 | 1.4 (0.6 to 3.6) | 0.43 | 6 | 956 | 1.6 (0.6 to 4.3) | 0.33 | 1.1 (0.4 to 3.4) | 0.84 |
| <−2 SD | 1 | 153 | 1.8 (0.2 to 13.9) | 0.59 | 0 | 117 | NA | NA | ||
| 4 weeks | 9 | 1197 | 2.4 (0.3 to 22.5) | 0.44 | 6 | 1031 | 1.9 (0.2 to 18.6) | 0.59 | 0.8 (0.3 to 2.2) | 0.65 |
| TROM | >−10° | ≤−10° | ||||||||
| <20% | 22 | 5655 | 1 (ref) | 0 | 728 | NA | ||||
| 20–60% | 8 | 1972 | 1.0 (0.4 to 2.3) | 0.95 | 2 | 277 | 2.0 (0.4 to 8.7) | 0.37 | 1.9 (0.4 to 9.3) | 0.42 |
| >60% | 11 | 1766 | 1.6 (0.8 to 3.4) | 0.21 | 1 | 238 | 1.9 (0.2 to 9.1) | 0.21 | 0.7 (0.1 to 5.8) | 0.77 |
| <−2 SD | 0 | 214 | NA | 1 | 39 | 7.0 (0.8 to 57.6) | 0.07 | NA | ||
| 4 weeks | 10 | 1548 | 2.0 (0.2 to 18.6) | 0.53 | 4 | 349 | 3.7 (0.4 to 39.8) | 0.27 | 1.8 (0.5 to 5.9) | 0.32 |
| IR ROM | >−7.5° | ≤−7.5° | ||||||||
| <20% | 22 | 5752 | 1 (ref) | 0 | 631 | NA | ||||
| 20–60% | 9 | 2037 | 1.1(0.5 to 2.5) | 0.75 | 1 | 212 | 1.3 (0.2 to 2.5) | 0.82 | 1.1 (0.1 to 9.1) | 0.92 |
| >60% | 11 | 1792 | 1.6 (0.8 to 3.5) | 0.20 | 1 | 213 | 1.2 (0.2 to 9.5) | 0.84 | 0.8 (0.1 to 6.0) | 0.80 |
| <−2 SD | 11 | 238 | 1.2 (0.1 to 9.0) | 0.89 | 0 | 22 | NA | NA | ||
| 4 weeks | 1 | 1621 | 2.2 (0.2 to 20.4) | 0.47 | 3 | 276 | 3.6 (0.3 to 40.3) | 0.30 | 1.6 (0.4 to 5.8) | 0.48 |
| ER ROM | >−10° | ≤−10° | ||||||||
| <20% | 11 | 3666 | 1 (ref) | 11 | 2717 | 1.2 (0.5 to 3.2) | 0.66 | |||
| 20–60% | 6 | 1216 | 1.6 (0.6 to 4.5) | 0.34 | 4 | 1033 | 1.2 (0.3 to 3.9) | 0.81 | 0.7 (0.2 to 2.7) | 0.61 |
| >60% | 6 | 1120 | 1.8 (0.6 to 5.0) | 0.26 | 6 | 884 | 2.1 (0.7 to 6.1) | 0.16 | 1.2 (0.4 to 3.8) | 0.79 |
| <−2 SD | 1 | 4 | 2.3 (0.3 to 19.3) | 0.44 | 0 | 102 | NA | NA | ||
| 4 weeks | 13 | 105 | 1.8 (0.6 to 5.0) | 0.26 | 1 | 116 | 2.1 (0.7 to 6.1) | 0.37 | 1.2 (0.2 to 9.7) | 0.84 |
| I:E ROM | ≤2.7 | >2.7 | ||||||||
| <20% | 18 | 5464 | 1 (ref) | 2 | 512 | 1.3 (0.3 to 5.6) | 0.76 | |||
| 20–60% | 9 | 1928 | 1.4 (0.6 to 3.1) | 0.42 | 0 | 184 | NA | NA | ||
| >60% | 11 | 1693 | 2.1 (0.9 to 4.5) | 0.07 | 1 | 176 | 1.7 (0.2 to 13.4) | 0.60 | 0.8 (0.1 to 6.7) | 0.87 |
| <−2 SD | 1 | 215 | 1.5 (0.2 to 12.0) | 0.70 | 0 | 19 | NA | NA | ||
| 4 weeks | 12 | 1595 | 2.9 (0.3 to 26.0) | 0.35 | 2 | 169 | 4.4 (0.3 to 56.6) | 0.26 | 1.5 (0.3 to 7.1) | 0.58 |
The total number of injuries was 68 and the total number of weeks at risk was 14 684.
*See the text for definition of progression.
†Denotes that the shoulder test (scapula control and isometric rotational strength at 30° rotation) significantly modifies the effect of workload ratio on handball-specific shoulder injuries.
–2 SD, weeks in which the 4-week average handball load was below –2 SDs from the mean; 4 weeks, the first 4 weeks of study, increase in handball load calculations not possible; Abd str., isometric abduction strength difference between dominant and non-dominant arm; ER ROM, external range of motion difference between dominant and non-dominant arm; I:E ROM, The ratio of the difference between internal rotation dominant arm vs. internal rotation non-dominant arm and difference external rotation dominant arm vs. external rotation non-dominant arm; IR ROM, internal range of motion difference between dominant and non-dominant arm; Rot str. 0, external:internal ratio rotational strength at 0° rotation; Rot str. 30, external:internal ratio rotational strength at 30° rotation; SI, shoulder injury; TROM, total range of motion difference between dominant and non-dominant arm; W, weeks.