BACKGROUND: Local vibration (LV) used as part of the warm-up can stimulate a specific body part and muscle group, potentially increasing muscle flexibility and performance. However, the effect of its combination with static stretching (SS) has not been thoroughly examined. OBJECTIVE: To elucidate the acute effectiveness of combining LV and SS (V+S) on the ROM of ankle dorsiflexion, squat jump, counter-movement jump (CMJ) and the dynamic postural stability index (DPSI). METHODS: Fifteen healthy men who were regularly involved in recreational sports participated in this study. Static Stretching, V+S, and non-stretching condition (control) were assigned randomly and the intervention period for each condition was five minutes. RESULTS: The dorsiflexion improved significantly in SS and V+S compared to the control. The CMJ height decreased significantly following SS compared to V+S and control. CONCLUSIONS: This study suggests that V+S improves ankle dorsiflexion ROM without compromising jump performance. Local vibration device could be an effective element in warming up but further research is warranted.
Background
Shoulder microinstability is often overlooked, which can be problematic, especially in overhead athletes. The slipping phenomenon is defined as posterior or lateral sliding of the humeral head in an elevated arm. When the shoulder is close to the end range of stability, the infraspinatus is highly activated and keeps the shoulder in the glenoid cavity. This study aimed to examine the characteristic physical function and infraspinatus activity during the pitching motion in baseball pitchers with shoulder instability.
Methods
Twenty-one male baseball pitchers participated and were divided into 2 groups based on radiograph findings at zero position: slipped (group S) and nonslipped (group N) groups. Physical function using Hara test and infraspinatus muscle activity during pitching were evaluated.
Results
The infraspinatus muscle activity during the acceleration phase was significantly greater in group S (59.5 ± 33.0%MVC) than in group N (33.0 ± 16.9%MVC) (
P
< .05). Positive rate of the Hara test in group S was significantly high in the loose test and elbow push test.
Conclusions
This study shows that baseball pitchers with slipping phenomenon have capsular laxity and scapular instability that indicate high infraspinatus muscle activity during the acceleration phase. Therefore, repetitive pitching with hyperactivity of the infraspinatus on the slipping shoulder may cause fatigue and dysfunction.
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