Shoulder Injury Prevention in Adolescent Handball Players Based on Scandinavian Protocols

Description: Standard Kibler/McClure SDT with five consecutive repetitions of active shoulder flexion and abduction at a metronome cadence. Participants hold hand weights scaled to body mass: 1.5 kg if body mass <68.1 kg, and 2.5 kg if ≥68.1 kg. Testing is video-recorded. Two trained assessors, rate each shoulder from the videos as none / subtle / obvious dyskinesis for each plane. Primary outcome: proportion with any dyskinesis (subtle+obvious) by plane; secondary: shift in severity category from baseline. Lower prevalence/severity indicates improvement.

Rater reliability plan: Inter-rater agreement will be quantified using weighted Cohen's kappa per plane.

Description: YBT-UQ performed for each arm in three directions (medial, inferolateral, superolateral), three valid trials per direction. Composite reach score = (sum of the 3 maximal reaches / limb length) × 100. Limb length = C7 to tip of middle finger. Primary score is the composite % per arm; higher is better.

Joint position sense was assessed in supine position using a wrist-mounted digital angle gauge. For external rotation testing, the participant actively moved the arm to their individual full external rotation in 90° abduction. The target angle was then calculated using the formula:

(Full ER in degrees-90)/2+90 This yields a mid-range position between neutral and the individual's maximal external rotation.

First, with eyes open, then vision was occluded using a towel, and the procedure was repeated three times per limb: the assessor passively positioned the arm at the target, returned it to vertical, and the participant attempted to reposition it to the same angle without visual feedback.

The absolute repositioning error (in degrees) between the target and reproduced positions was recorded for each trial, then averaged across the three trials per limb.

Internal rotation target angle calculated as: 90-(90-Full IR in degrees)/2 Lower error values indicate better proprioceptive acuity

Weekly Oslo Sports Trauma Research Center Overuse Injury Questionnaire (4 items). Composite 0-100 severity (higher = worse). Report mean weekly severity, prevalence of any problem (non-minimum response on any item), and prevalence of substantial problem (moderate/severe reduction in training/performance or complete inability to participate), as per standard methodology.

Closed Kinetic Chain Upper Extremity Stability Test (CKCUEST). Participants assume a standard push-up position with two parallel tape lines placed at a distance equal to 1.5 × the participant's biacromial breadth (measured between the lateral edges of the acromion processes). They alternately touch the opposite hand with one hand for three trials of 15 seconds each, with 30 seconds rest.

Two outcomes are recorded:

• Touch count - mean number of valid touches across the three trials (per participant). Higher values indicate better upper-extremity closed-chain stability and power.
• Error count - number of form faults (e.g., loss of plank, hip rotation >45°, line misses) summed across the three trials. Lower values indicate better movement quality/control.

A trained assessor records both outcomes according to published protocols, flagging invalid repetitions and documenting errors in real time.

LSST performed by measuring the side-to-side difference (mm) in the distance between the inferior angle of the scapula (angulus inferior) and the nearest midline spinous process in three standardized arm positions: (1) arms relaxed at sides; (2) hands on hips with thumbs posterior; (3) 90° humeral abduction with internal rotation. The total LSST score is calculated as the sum of absolute asymmetries across the three positions. Lower scores indicate better scapular symmetry/control. Measurements are taken with a non-elastic, millimeter-scale measuring tape, with the athlete standing in a relaxed posture, feet shoulder-width apart.

Modified Lateral Scapular Slide Test (mLSST) performed in a static 30° scaption position while holding dumbbells of 2 kg and 4 kg, respectively. For each load, the side-to-side difference (mm) between the inferior angle of the scapula (angulus inferior) and the nearest midline spinous process is measured using a non-elastic, millimeter-scale measuring tape. The outcome for each load is the absolute asymmetry (mm). Lower values indicate better scapular symmetry/control under load.

Maximal isometric shoulder external rotation (ER) and internal rotation (IR) strength measured using a ForceFrame testing system (VALD Performance). Testing was performed in supine position with the shoulder in 90° abduction and neutral rotation. For each rotation direction, participants completed two maximal-effort trials per limb (due to time constraints; standard protocols recommend three), with ~30 seconds rest between trials.

The highest peak force (N) from the two trials was used for analysis. Participants received standardized verbal encouragement during each trial. The ForceFrame system was calibrated before testing and measurements were recorded according to manufacturer guidelines.

Self-reported weekly minutes of handball training, match play, and strength/conditioning. Used to adjust analyses and to compute injury rates (exploratory).

Number of completed prevention sessions per week (team logs + player self-report). Outcome: mean sessions/week per athlete and per team; proportion achieving ≥2 sessions/week.

Weekly self-reported perception of the programme's usefulness on a 0-10 scale (0 = not useful at all, 10 = extremely useful). Report mean weekly score and trends over time. Used to explore the relationship between perceived usefulness and adherence.

Any acute or overuse shoulder complaint causing time-loss (missed full training/match), verified with staff logs. Rate = injuries / 1,000 h (training + match).

Number and nature of adverse events (e.g., exacerbation of pain leading to missed session; other exercise-related events) recorded by staff.