Effect of Stretching Protocols on Glenohumeral-Joint Muscle Activation in Elite Table Tennis Players

Context: Several studies report static-stretch-induced deficits and dynamic-stretch performance improvement after intervention. Purpose: To investigate the muscle activation of the forehand and backhand in table tennis players after experiencing static- and dynamic-stretching protocols. Methods: A total of 24 elite male table tennis players (age 22.7 [3.46] y, height 1.78 [0.03] m) were tested before and 0, 10, 20, and 30 min after the 3 conditions (dynamic stretch, static stretch, and no stretch). The MEGA ME6000 (Mega Electronics, Kuopio, Finland) was used to capture the surface EMG data of the anterior deltoid, middle deltoid, posterior deltoid, biceps, and triceps muscles. Muscle activation data of the pretest were compared with posttest 0, 10, 20, and 30 min. These data were also compared between 3 different conditions (dynamic stretch, static stretch, and no stretch). Results: A 2-way repeated-measures analysis of variance indicated significant differences in the forehand and backhand, and Bonferroni test as a post hoc comparison revealed significant differences between the pretest and posttests in several muscles (P < .05). Furthermore, there were significant differences in the posttest between the 3 conditions (P < .05). Conclusions: In general, there was a short-term effect of static- and dynamic-stretching protocols on glenohumeral-joint muscle activation in elite table tennis players. The static and dynamic stretching presented a decrease and increase, respectively, in muscle activation up to 30 min after stretching. In conclusion, the additive and subtractive effects of dynamic- and static-stretching protocols on muscle activation seem to persist after 30 min.

El efecto agudo de diferentes tipos de estiramiento sobre la altura de salto de gimnastas: revisión sistemática

Objetivo: El principal objetivo del presente estudio fue analizar el efecto de diferentes tipos de estiramiento sobre la altura de salto de gimnastas. Metodología: Se consultaron las siguientes bases de datos: EBSCOhost (SPORTDiscus, MEDLINE, Academic Search Complete, E-Journals, Fuente Académica Premier, International Bibliography of Theatre & Dance with Full Text y PsycARTICLES) y Pubmed. Se utilizó la siguiente frase bolena: (stretch OR static stretch OR dynamic stretch OR ballistic stretch OR proprioceptive neuromuscular facilitation) AND (jumping OR vertical jump OR countermovement jump OR explosive strength OR performance) AND (gymnasts OR gymnastics). Se establecieron los siguientes criterios de elegibilidad: Que posea un diseño experimental, cuasiexperimental o preexperimental. Que la muestra sea de gimnastas. Explicación de metodología clara. Buena descripción del método de estiramiento aplicado. Resultados: Se incluyó un total de 10 estudios individuales, la muestra total entre esa cantidad de estudios fue de 226 sujetos y, la cantidad de intervenciones fue de 16. El 75 % de las intervenciones tuvo un efecto no significativo (p>.05), mientras que el otro 25 % tuvo un efecto significativo (p<.05*) sobre la altura de salto. Ese porcentaje de efectos significativos corresponde a dos aumentos y dos disminuciones de la altura de salto. Conclusiones: La mayoría de las intervenciones indica que la altura de salto de gimnastas no se ve afectada por los diferentes tipos de estiramiento (sólo el 12.5 % de las intervenciones refutan esta afirmación), incluso, dos intervenciones mostraron aumentos de la capacidad de salto durante un tiempo determinado.

Acute Effects of Gastrocnemius/Soleus Self-Myofascial Release Versus Dynamic Stretching on Closed-Chain Dorsiflexion

Context: Limited ankle dorsiflexion (DF) range of motion has been correlated with decreased flexibility of the gastrocnemius/soleus complex. Decreased ankle DF range of motion can lead to an increase in lower-extremity injuries, for example, acute ankle sprains, Achilles tendinopathy. Objective: The purpose of this study was to determine whether a single application of the intervention to the gastrocnemius/soleus complex via multidirectional self-myofascial release using a foam roller, multiplanar dynamic stretch performed in downward dog, or a combination of both techniques acutely improved ankle DF. Design: Subjects were assigned to groups via random card selection. Investigators provided verbal cues as needed to yield correct performance of interventions. Both interventions were performed twice for 1 minute using a dynamic walking rest of 30.48 m at a self-selected pace between interventions. Statistical analyses were completed using a 1-way analysis of variance, at α level ≤ .05. Setting: A convenience sample study. Participants: A total of 42 asymptomatic physical therapy students (18 females and 24 males) with mean age of 26.12 (4.03) years volunteered to participate. Interventions: Multidirectional self-myofascial release using a foam roller, multiplanar dynamic stretch performed in downward dog, or a combination of both techniques. Main Outcome Measures: Weight-bearing right ankle DF measurements were recorded in centimeters using a forward lunge technique (intraclass correlation coefficient = .98, .97, and .96). Results: Data analysis revealed no significant difference between the 3 groups in all pre–post measurements (P = .82). Mean (SD) measurements from pretest to posttest for myofascial release, dynamic stretching, and combination interventions were 0.479 (0.7) cm, 0.700 (0.7) cm, and 0.907 (1.4) cm, respectively. Conclusion: Until further studies are conducted, the selection of technique to increase ankle DF range of motion should be based on each individual patient’s ability, preference, and response to treatment.

Structural and mechanical remodeling of the cytoskeleton maintains tensional homeostasis in 3D microtissues under acute dynamic stretch

When stretched, cells cultured on 2D substrates share a universal softening and fluidization response that arises from poorly understood remodeling of well-conserved cytoskeletal elements. It is known, however, that the structure and distribution of the cytoskeleton is profoundly influenced by the dimensionality of a cell’s environment. Therefore, in this study we aimed to determine whether cells cultured in a 3D matrix share this softening behavior and to link it to cytoskeletal remodeling. To achieve this, we developed a high-throughput approach to measure the dynamic mechanical properties of cells and allow for sub-cellular imaging within physiologically relevant 3D microtissues. We found that fibroblast, smooth muscle and skeletal muscle microtissues strain softened but did not fluidize, and upon loading cessation, they regained their initial mechanical properties. Furthermore, microtissue prestress decreased with the strain amplitude to maintain a constant mean tension. This adaptation under an auxotonic condition resulted in lengthening. A filamentous actin cytoskeleton was required, and responses were mirrored by changes to actin remodeling rates and visual evidence of stretch-induced actin depolymerization. Our new approach for assessing cell mechanics has linked behaviors seen in 2D cultures to a 3D matrix, and connected remodeling of the cytoskeleton to homeostatic mechanical regulation of tissues.