apart from normal growth, despite observable differences in playing experience. This observation is consistent with another overhead racket sport. 25 , 26 For the females, there was no age group effect in most indices (shoulder and knee) with the exception of ER-CON-D and ER-ECC-ND strength wherein the
Noh Zulfikri, Victor S. Selvanayagam, and Ashril Yusof
Charles Goulet and Isabelle Rogowski
Context: Tennis playing generates specific adaptations, particularly at the dominant shoulder. It remains to be established whether shoulder-strength balance can be restored by sling-based training for adolescent recreational tennis players. Objective: To investigate the effects of a sling-based exercise for shoulder external rotators on external rotator muscle strength, internal rotator muscle strength, glenohumeral range of motion, and tennis serve performance. Design: Test-retest design. Setting: Tennis training sports facilities. Participants: Twelve adolescent male players volunteered to participate in this study (age: 13.3 ± 0.5 y; height: 1.64 ± 0.07 m, mass: 51.7 ± 5.8 kg, International Tennis Number: 8). Intervention: The procedure spanned 10 wk. For the first 5 wk, players performed their regular training (RT) twice a week. For the last 5 wk, a sling-based exercise (SE) for strengthening the shoulder external rotator muscles was added to their RT. Main Outcome Measures: Maximal isometric strength of shoulder external and internal rotator muscles and glenohumeral range of motion in external and internal rotation were assessed in both shoulders. Serve performance was also evaluated by accuracy and postimpact ball velocity using a radar gun. Results: No change was found in any measurement after the RT period. Significant increases in external (∼+5%; P < .001) and internal (∼+2%; P < .05) rotator muscle strength and in external/internal strength ratio (∼+4%; P < .001) were observed after the SE period. Serve velocity and accuracy were significantly improved after SE (∼+2% and ∼+24%, respectively; P < .05 for both), while no clinically meaningful alterations in range of motion were observed. Conclusions: Prophylactic intervention through SE for strengthening shoulder external rotator muscles appears effective in restoring strength balance at the dominant shoulder and may prevent adolescent tennis players from sustaining degenerative shoulder problems, which could later impair their performance of daily and work-related tasks.
Marcel Bouffard and Albert E. Wall
The effect of knowledge on decision making and performance of educable mentally handicapped (EMH) adolescents was studied in a simulated table tennis situation. In two experiments, knowledge about where the ball would land on the table was manipulated. The position the players selected to return the ball was affected by the knowledge (uncertainty) associated with its future landing location. Depending upon the degree of uncertainty, results indicated the players used (a) a total preparation for one particular event strategy, (b) a partial preparation for one particular event strategy, or (c) a no-preparation for one particular event strategy. Further, knowledge about the ball’s future landing location affected the decision about the type of stroke to use and had a minimal effect on the number of balls hit. Overall, these results demonstrate an intricate relationship between knowledge, decision making, and performance in a simulated racket sport by EMH adolescents.
Mia Beck Lichtenstein, Claire Gudex, Kjeld Andersen, Anders Bo Bojesen, and Uffe Jørgensen
undertaken was ball sport (eg, football, handball), running, fitness, biking, weight lifting, dancing/gymnastics, racket sport, swimming, and power walking. As shown in Table 1 , injured exercisers were significantly older and had a higher BMI and were more likely to be male. The groups were similar in the