Compared with shoulder-only training and with continued tennis training alone, will the addition of core strengthening to shoulder training produce significantly greater improvements in flat serve ball speed in healthy tennis players? Secondary Hypothesis: * Combined core + shoulder training will produce greater improvement in serve accuracy than shoulder-only training or tennis training alone. * Combined core + shoulder training will produce greater improvement in TGAR than shoulder-only training or tennis training alone. * Combined core + shoulder training will produce greater improvement in core strength/endurance and shoulder rotational strength than the comparator groups.
The kinetic chain model suggests that core musculature plays a crucial role in transferring energy from the lower body to the upper extremity during the tennis serve. However, evidence on the relationship between core strength and tennis serve (TS) ball speed and passive total glenohumeral arc of rotation (TGAR) remains inconsistent, warranting further investigation. It is hypothesized that the addition of core muscle exercises to the training program would yield greater improvements in terms of tennis serve ball speed and TGAR when compared to a control group performing only shoulder exercises in tennis players. Tennis players with at least 1-3 years of weekly tennis training will be included and allocated randomly into the control group (CG) and experimental group (EG). CG participants will perform shoulder exercises and sham core exercises. EG participants will receive the same training as CG in addition to performing core exercises. Both groups will participate in a 12-week intervention (2 sessions per week, 50 minutes per session). Pre- and postintervention assessments will include TS ball speed analysis and TGAR, respectively.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
SINGLE
Enrollment
120
Delivered 2×/week for 10 weeks under supervision of a licensed physical therapist or certified strength and conditioning specialist. Progressive resistance program including: * External/internal rotation strengthening (resistance band, cable, or dumbbell) at 0° and 90° abduction * Scapular stabilization exercises (rows, Y-T-W raises, serratus punch) * Posterior shoulder stretching (sleeper stretch, cross-body stretch) for the TGAR component * Progressive overload every 2 weeks based on tolerated resistance/repetitions Sham :Low-intensity, non-progressive trunk mobility exercises with minimal loading (e.g., seated trunk rotations without resistance, cat-camel stretches), matched for session time and attention to control for non-specific training effects, without targeting core strength/endurance adaptation.
Delivered 2×/week for 10 weeks, same sessions as the shoulder program (combined \~50-60 minute sessions), progressive core program including: * Anti-rotation exercises (Pallof press) * Rotational power exercises (medicine ball rotational throws, cable woodchoppers) * Anterior/lateral/posterior chain stability (plank variations, side plank, bird-dog) * Progressive overload via increased resistance, hold time, or instability surface every 2 weeks
Beirut Arab University
Beirut, Beirut, Lebanon
RECRUITINGBAU activities
Beirut, Giza, Lebanon
RECRUITINGFlat serve ball speed
Flat serve ball speed (km/h or mph), measured via radar gun (e.g., Stalker Pro II) or equivalent validated device, averaged across the best 5 of 10 flat serves hit into the deuce-side service box, measured at baseline (Week 0) and post-intervention (Week 12).
Time frame: measured at baseline (Week 0) and post-intervention (Week 12).
Serve accuracy
* Target-based scoring system: standardized service box divided into scoring zones (e.g., 5 concentric/quadrant zones worth 1-5 points); participant hits 10 flat serves aimed at a designated target zone (e.g., wide serve to deuce court corner); accuracy score = mean points across 10 serves. * Recorded simultaneously with ball speed trials (speed-accuracy trade-off examined as an exploratory outcome).
Time frame: measured at baseline (Week 0) and post-intervention (Week 12).
Total glenohumeral arc of rotation (TGAR)
● Passive internal rotation (IR) + external rotation (ER) range of motion measured via goniometry (or inclinometer) with scapula stabilized, participant supine, shoulder abducted to 90°, elbow flexed to 90°. TGAR = IR + ER (degrees). Measured bilaterally.
Time frame: measured at baseline (Week 0) and post-intervention (Week 12).
Shoulder rotational strength
● Peak IR and ER isometric or isokinetic torque (Nm), measured via hand-held dynamometer (standardized stabilization protocol) or isokinetic dynamometer (60°/sec and 180°/sec) if available, at 0° abduction. ER/IR strength ratio calculated. Measured bilaterally.
Time frame: measured at baseline (Week 0) and post-intervention (Week 12).
Core strength/endurance
● McGill core endurance battery: trunk flexor endurance test (seconds), bilateral side-bridge/plank endurance test (seconds).
Time frame: measured at baseline (Week 0) and post-intervention (Week 12).
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