Dynamic stretching–electroplating metal-coated textile for a flexible and stretchable zinc–air battery

A metal electrode is a significant component of a zinc–air battery(ZAB),but the metal material is usually not elastic,which severely restricts the application of flexible and stretchable ZABs in the field of wearable electronic devices.Herein,we report a flexible and stretchable metal-coated textile prepared by a dynamic stretching–electroplating based on a wavy spandex textile substrate.Benefiting from the unique woven and wavy structure,the metal-coated textile shows a high stretchability of 100%and stable conductivity.In situ scanning electron microscope observation during stretching showed that the tensile strain of the metal-coated textile is mainly attributed to the deformation of the microfiber network at the bottom position of the wave structure.In addition,a sodium carboxymethyl cellulose–polyacrylic acid–potassium hydroxide composite hydrogel has been used as the electrolyte.This hydrogel shows excellent ionic conductivity,mechanical properties,and water retention properties,which makes it suitable for the semi-open system of ZAB.Furthermore,a flexible and stretchable sandwich-structure ZAB,assembled using the above-mentioned electrodes and electrolyte,operates stably even under rapid stretching/releasing cycle deformation.Because of its facile preparation and low cost,this flexible and stretchable ZAB is suitable for fabrication of large-area batteries to obtain higher output current and power to drive wearable electronic devices.

Effect of different stretching strategies on the kinetics of vertical jumping in female volleyball athletes

Purpose： The present study aimed to examine the effect of static stretching （SS） and a sport-specific dynamic stretching （DS） session at two specific post-stretch time intervals in highly trained female athletes （age 19.90 ± 1.60 years; height 1.80 ±0.06 m; mass 76.87 ± 9.95 kg） on kinetic parameters of peak force, time-to-takeoff, and rate of force development. Methods： The data were collected over 3 days （randomized within subject design with control session）. Following each stretch session （SS vs. DS vs. control） of equal duration （7 min total： 30 s per targeted muscle group） participants performed countermovement jumping on a force platform at 1 and 15 rain after stretching. Results： The DS session significantly improved upon kinetic variables of rate of force development, peak force, and time-to-takeoffrelative to SS at 1 min after stretching. No significant effect was found at 15 min. Conclusion： Together these findings suggest that when training and competing to jump quickly and maximally the female athlete should incorporate DS instead of SS as part of their pre-competition warm-up, but conduct performance within 15 min of their warm-up to elicit maximal gains

Effect of deep transverse friction massage vs stretching on football players’ performance

BACKGROUND Flexibility,agility and muscle strength are key factors to either win or lose a game.Recently the effect of a new technique,deep transverse friction massage(DTFM)on muscle extensibility as compared to traditional stretching techniques has been examined.AIM To compare the effect of DTFM vs static and dynamic stretching techniques on the hamstring’s extensibility,agility,and strength amongst Lebanese and Syrian football players.Recording the incidence of non-contact hamstring muscle injury was a secondary objective.METHODS This study is a single-blinded prospective longitudinal randomized controlled trial.The experiment took place over a period of four weeks.Football players were randomized into three intervention groups(static stretching;dynamic stretching;DTFM).Participants of each group were followed-up carefully by assessors during their intervention sessions three times per week,for a total of 12 sessions and during the data collection.Extensibility,agility,and strength were compared between intervention groups at(baseline;acute;and chronic)phases.Straight leg raise and 1 repetition maximum tests were used to measure the dominant leg hamstring muscle extensibility and maximal strength respectively.T-drill test was used to assess the lower extremities agility.RESULTS Of 103 Lebanese and Syrian male football players aged between 18 and 35 were sampled from Damascus-Syria and South of Lebanon to participate in this study.Between-groups measures of acute strength(P=0.011)and chronic extensibility(P=0.000)solely showed a significant difference,and the static group showed to be superior as compared to the other groups.No loss to follow-up or protocol violation was recorded.CONCLUSION Static stretching is showing to be superior to the other techniques used,regarding gaining long-term extensibility and short-term maximal muscle strength.In addition,DTFM showed improvements but did not outweigh the effects on footballers’performance when comparing it to static and dynamic techniques.Finally,no difference between the interventions is recorded regarding the rate of muscle injuries incidence.

A Universal Equipment for Biaxial Stretching of Polymer Films

A biaxial stretching equipment was designed and constructed to enable fundamental studies of the relationship between film processing conditions and structures of oriented film products. With programmable drive motors and scissorlike mechanism, all stretching modes, including uniaxial stretching with constant and free width, simultaneous and sequential biaxial stretching, can be applied to a square-shaped sheet. Parameters related to film stretching manufacturing, such as temperature, draw ratio and stretching speed can be set independently to meet the requirement of different polymers. The force information during stretching is recorded by two miniature tension sensors in two directions independently, which can monitor the mechanical stimulus and stress response. Using this equipment, experiments are conducted to investigate the influence of stretching parameters on the structure of polypropylene films, which provides an effective method to tailor the processing conditions to obtain the films with desired properties.