Chronic flexibility gains: effect of isometric contraction duration during proprioceptive neuromuscular facilitation stretching techniques

The aim of this study was to assess the effect of to isometic contraction durations during propiceptive neuromuscular facilitation stretching on gains inflexion at the hip. Forty-three women (M age = 20.0 years, SD = 1.3) were assigned to one of three groups: 5-s isometric contraction (5-IC), 10-IC, and control. Flexibility was assessed at baseline and Weeks 3 and 6. Analysis of covariance, controlling for pretest differences, showed a significant interaction, F(2, 33) = 44.1, p < .001. Flexibility was significant lower in the control group relative to the 5-IC and 10-IC groups and in the 5-IC group relative to the 10-IC group at 3 and 6 weeks (3 weeks = 101.2 +/- 1.4 degrees, 114.3 +/- 1.5 degrees, 120.5 +/- 1.3 degrees; 6 weeks = 103.0 +/- 1.4 degrees, 126.1 +/- 1.6 degrees, 133.3 +/- 1.4 degrees for control, 5-IC and 10-IC groups, respectively). A longer contraction time led to greater increases in flexibility.     

不同拉伸内容在短跑准备活动组合练习中教学效果的实验比较研究

在查阅文献、专家访谈和问卷调查的基础上,进行了短跑准备活动组合练习中不同拉伸内容的实验比较研究,分别测试两组的股后肌群柔韧性、膝关节活动幅度、体温、心率等指标,通过数据比较分析,以探求短跑项目准备活动组合练习中不同拉伸内容的练习效果,为科学化训练提供一定的理论依据。     

Optimal sampling frequency in recording of resistance training exercises

The purpose of this study was to analyse the raw lifting speed collected during four different resistance training exercises to assess the optimal sampling frequency. Eight physically active participants performed sets of Squat Jumps, Countermovement Jumps, Squats and Bench Presses at a maximal lifting speed. A linear encoder was used to measure the instantaneous speed at a 200 Hz sampling rate. Subsequently, the power spectrum of the signal was computed by evaluating its Discrete Fourier Transform. The sampling frequency needed to reconstruct the signals with an error of less than 0.1% was f_99.9 = 11.615 ± 2.680 Hz for the exercise exhibiting the largest bandwidth, with the absolute highest individual value being 17.467 Hz. There was no difference between sets in any of the exercises. Using the closest integer sampling frequency value (25 Hz) yielded a reconstruction of the signal up to 99.975 ± 0.025% of its total in the worst case. In conclusion, a sampling rate of 25 Hz or above is more than adequate to record raw speed data and compute power during resistance training exercises, even under the most extreme circumstances during explosive exercises. Higher sampling frequencies provide no increase in the recording precision and may instead have adverse effects on the overall data quality.     

PNF拉伸法对武术专选学生下肢柔韧性的影响

以陕西师范大学体育学院2013级36名武术专选生为研究对象,以前俯腰、横叉、纵叉、正踢腿为指标对PNF拉伸法（A组）,动静力结合训练法（B组）,传统的武术下肢柔韧训练方法（C组）的效果进行对比研究。结果表明：经过10周的训练,A、B、C三组学生的各指标成绩均有不同程度的变化,且变化幅度A组>B组>C组。可见,PNF拉伸法是三种训练方法中对提高武术专选生下肢柔韧性最有效的方法。     

Evaluation of a static stretching intervention on vascular endothelial function and arterial stiffness

Purpose: Maintenance and enhancement of vascular endothelial function contribute to the prevention of cardiovascular disease and prolong a healthy life expectancy. Given the reversible nature of vascular endothelial function, interventions to improve this function might prevent arteriosclerosis. Accordingly, we studied the effects of a 6-month static stretching intervention on vascular endothelial function (reactive hyperaemia peripheral arterial tonometry index: RH-PAT index) and arterial stiffness (brachial-ankle pulse wave velocity: baPWV) and investigated the reversibility of these effects after a 6-month detraining period following intervention completion. Methods: The study evaluated 22 healthy, non-smoking, premenopausal women aged ≥40 years. Subjects were randomly assigned to the full-intervention (n?=?11; mean age: 48.6?±?2.8 years) or a half-intervention that included a control period (n?=?11; mean age: 46.9?±?3.6 years). Results: Body flexibility and vascular endothelial function improved significantly after 3 months of static stretching. In addition to these improvements, arterial stiffness improved significantly after a 6-month intervention. However, after a 6-month detraining period, vascular endothelial function, flexibility, and arterial stiffness all returned to preintervention conditions, demonstrating the reversibility of the obtained effects. Conclusion: A 3-month static stretching intervention was found to improve vascular endothelial function, and an additional 3-month intervention also improved arterial stiffness. However, these effects were reversed by detraining.     

Comparison of vibration rolling,nonvibration rolling,and static stretching as a warm-up exercise on flexibility,joint proprioception,muscle strength,and balance in young adults

Warm-up is an essential component for optimizing performance before an exercise session. This study investigated that the immediate effects of vibration rolling (VR), nonvibration rolling (NVR), and static stretching as a part of a warm-up regimen on the flexibility, knee joint proprioception, muscle strength, and dynamic balance of the lower extremity in young adults. Compared with the preintervention, VR induced the range of motion of knee flexion and extension significantly increased by 2.5% and 6%, respectively, and isokinetic peak torque and dynamic balance for muscle strength and dynamic balance increased by 33%–35% and 1.5%, respectively. In the three conditions, most outcomes between VR and NVR were comparable; however, the participants had a significantly higher knee joint reposition error after NVR than after VR, indicating that NVR would have a hampering knee joint proprioception effect. In particular, compared with static stretching, VR significantly increased the quadriceps muscle strength by 2-fold and dynamic balance by 1.8-fold. These findings suggest that athletic professionals may take VR into account for designing more efficient and effective preperformance routine to improve exercise performances. VR has high potential to translate into an on-field practical application.     

The European College of Sports Sciences Position statement: The role of stretching exercises in sports

Abstract

Possible peripheral mechanisms of fatigue have been widely documented, including the depletion of muscle glycogen and the loss of body fluids. The notion that the brain may be intimately involved in the fatigue process is not a new one, but recently possible neurobiological mechanisms involved in this response have been investigated. Changes in central neurotransmission occur during exercise that may result in feelings of tiredness, lethargy, and a loss of motivation to continue exercise, contributing to the development of fatigue. There is evidence that manipulation of the neurotransmitters serotonin, dopamine, and noradrenaline, through the administration of pharmacological agents, may delay the onset of fatigue during prolonged exercise, particularly when performing in a warm environment. Supplementation with branched-chain amino acids and tyrosine can influence perceived exertion and some measures of mental performance, but the results of several apparently well-controlled laboratory studies have not demonstrated a positive effect on exercise capacity under temperate conditions. The ergogenic effects of carbohydrate and caffeine are well documented, but often little attention is paid to the central effects of these nutrients. Carbohydrate ingestion has been demonstrated to alter brain activity and cerebral metabolism, factors that may be important in the development of fatigue and the maintenance of skill performance. There is strong evidence for a positive effect of caffeine on exercise performance, with recent data highlighting the role of central adenosine as a mediator of this response.     

跳远无板助跑起跳练习与起跳最佳效果的实验研究

跳远起跳最佳效果的特征主要体现在起跳的腾起水平速度(在一定腾起角度状态下)，而起跳腾起的水平速度来于助跑的质量，其中主要表现在起跳前几步助跑的速度、节奏和助跑技术。通过教学实验，反映出无板助跑起跳练习对起跳前几步助跑的速度感、节奏感的效果比有板起跳练习的效果要好，这对形成起跳的最佳效果无疑是有积极的影响。从而可以加大起跳腾空阶段身体重心通过的水平距离，它对提高跳远运动成绩将起到决定性的作用。     

The time course of muscle-tendon properties and function responses of a five-minute static stretching exercise

Abstract

The purpose of this study was to investigate the time course of the changes of muscle-tendon mechanical properties and the function responses of the plantar flexor muscles following 5?×?60?s of static stretching.

Fourteen healthy volunteers were tested on four separate days in a random order with three different rest times (0, 5, 10?min) after 5?×?60?s of stretching or following a control period without stretching. During each test, the dorsiflexion range of motion (RoM), passive resistive torque (PRT), and maximum voluntary contraction (MVC) were measured with a dynamometer. Ultrasonography of the gastrocnemius medialis (GM) muscle-tendon junction displacement and motion capture allowed us to determine the length changes in the tendon and muscle, respectively, and hence to calculate their stiffness.

We observed an increase in RoM and decrease in MVC at 0, 5, and 10?min post-stretching. This could be attributed to an increase in muscle elongation which lasted at least 10?min. A decrease in muscle-tendon stiffness was observed immediately, but not 5 or 10?min after the stretching. A decrease in PRT and muscle stiffness was observed up to 5?min after the stretching. No changes were detected in tendon stiffness or in any variable in the control group.

The effects of a 5?×?60?s static stretching exercise changes the muscle-tendon functions (RoM, MVC), which are related to mechanical changes of the muscle but not the tendon structure, respectively. Although the functional changes last for at least 10?min, changes in muscle stiffness were only observed up to 5?min after the stretching exercise.     

Transmission of whole body vibration to the lower body in static and dynamic half-squat exercises

Whole body vibration (WBV) is used as a training method but its physical risk is not yet clear. Hence, the aim of this study is to assess the exposure to WBV by a measure of acceleration at the lower limb under dynamic and static postural conditions. The hypothesis of this paper is that this assessment is influenced by the frequency, position, and movement of the body. Fifteen healthy males are exposed to vertical sinusoidal vibration at different frequencies (20–60 Hz), while adopting three different static postures (knee extension angle: 180°, 120° and 90°) or performing a dynamic half-squat exercise. Accelerations at input source and at three joints of the lower limb (ankle, knee, and hip) are measured using skin-mounted accelerometers. Acceleration values (g) in static conditions show a decrease in the vibrational dose when it is measured at a more proximal location in the lower extremity. The results of the performed statistical test show statistically significant differences (p < 0.05) in the transmissibility values caused by the frequency, the position, and to the presence of the movement and its direction at the different conditions. The results confirm the initial hypothesis and justify the importance of a vibration assessment in dynamic conditions.     

The effects of cold application and modified PNF stretching techniques on hip joint flexibility in college males.

The purpose of the study was to determine the effects of modified Proprioceptive Neuromuscular Facilitation (PNF) flexibility techniques on hip flexion in college males and to determine if local cold application enhances the effectiveness of these techniques. Male subjects (N = 120), with an average age of 21.5 +/- 2.7 years, were randomly assigned to one of four different kinds of stretching treatments with cold or no cold application (15 per group). Range of motion (ROM) in degrees was determined following four stretching techniques: three modified PNF (PCP, 3-PIECP, 3-PIFCP) and a passive stretch (P). Data were analyzed using a 2 (conditions) x 4 (treatments) ANOVA. There were no significant differences in ROM between cold and no cold conditions. Significant differences existed among ROM techniques (p less than .05). Post hoc analyses revealed that the three modified PNF techniques resulted in greater ROM than the passive stretch technique. However, we conclude that cold application does not influence the effectiveness of selected stretching techniques.     

The effects of a 4-week static stretching programme on the individual muscles comprising the hamstrings

The aims of this study were to investigate the effects of a 4-week intervention of static stretching (SS) on muscle hardness of the semitendinosus (ST), semimembranosus (SM) and biceps femoris (BF) muscles. Shear elastic modulus was measured by using ultrasound shear wave elastography as the index of muscle hardness. Thirty healthy men (age 22.7 ± 2.2 years) volunteered for this study and were randomly assigned to the SS intervention group (n = 15) or the control group (n = 15). Participants in the SS intervention group received a 4-week stretch intervention for the hamstrings of their dominant leg. Shear elastic moduli of the hamstrings were measured at initial evaluation and after 4 weeks in both groups at a determined angle. In all muscles, the shear elastic modulus decreased significantly after SS intervention. The percentage change in the shear elastic modulus from the value at initial evaluation to after 4 weeks intervention was greatest in the SM. These results suggest that SS intervention has chronic effects on reducing hardness of the hamstring muscle components, especially the SM muscle.     

Flexibility training in preadolescent female athletes: Acute and long-term effects of intermittent and continuous static stretching

This study compared the acute and long-term effects of intermittent and continuous static stretching training on straight leg raise range of motion (ROM). Seventy-seven preadolescent female gymnasts were divided into a stretching (n = 57), and a control group (n = 20). The stretching group performed static stretching of the hip extensors of both legs, three times per week for 15 weeks. One leg performed intermittent (3 × 30 s with 30 s rest) while the other leg performed continuous stretching (90 s). ROM pre- and post-stretching was measured at baseline, on weeks 3, 6, 9, 12, 15 and after 2 weeks of detraining. ROM was increased during both intermittent and continuous stretching training, but remained unchanged in the control group. Intermittent stretching conferred a larger improvement in ROM compared to both continuous stretching and control from week 3, until the end of training, and following detraining (p = 0.045 to 0.001 and d = 0.80 to 1.41). During detraining, ROM after the intermittent protocol decreased (p = 0.001), while it was maintained after the continuous protocol (p = 0.36). Acute increases in ROM following the intermittent stretching were also larger than in the continuous (p = 0.038). Intermittent stretching was more effective than continuous, for both long-term and acute ROM enhancement in preadolescent female athletes.     

Acute effects of static stretching on characteristics of the isokinetic angle - torque relationship, surface electromyography, and mechanomyography

The aims of this study were to examine the acute effects of static stretching on peak torque, work, the joint angle at peak torque, acceleration time, isokinetic range of motion, mechanomyographic amplitude, and electromyographic amplitude of the rectus femoris during maximal concentric isokinetic leg extensions at 1.04 and 5.23 rad x s(-1) in men and women. Ten women (mean +/- s: age 23.0 +/- 2.9 years, stature 1.61 +/- 0.12 m, mass 63.3 +/- 9.9 kg) and eight men (age 21.4 +/- 3.0 years, stature 1.83 +/- 0.11 m, mass 83.1 +/- 15.2 kg) performed maximal voluntary concentric isokinetic leg extensions at 1.04 and 5.23 rad x s(-1). Following the initial isokinetic tests, the dominant leg extensors were stretched using four static stretching exercises. After the stretching, the isokinetic tests were repeated. Peak torque, acceleration time, and electromyographic amplitude decreased (P< or = 0.05) from pre- to post-stretching at 1.04 and 5.23 rad . s(-1); there were no changes (P > 0.05) in work, joint angle at peak torque, isokinetic range of motion, or mechanomyographic amplitude. These findings indicate no stretching-related changes in the area under the angle - torque curve (work), but a significant decrease in peak torque, which suggests that static stretching may cause a "flattening" of the angle - torque curve that reduces peak strength but allows for greater force production at other joint angles. These findings, in conjunction with the increased limb acceleration rates (decreased acceleration time) observed in the present study, provide tentative support for the hypothesis that static stretching alters the angle - torque relationship and/or sarcomere shortening velocity.     

对个体终身锻炼的微观审视

从认识论角度对个体终身锻炼进行了理论上的探讨,微观分析了终身锻炼的4个基本属性、5种锻炼状态及其特征以及保持终身锻炼的4项个体条件.     

Muscle metabolism and performance improvement after two training programmes of sprint running differing in rest interval duration

Repeated-sprint training often involves short sprints separated by inadequate recovery intervals. The effects of interval duration on metabolic and performance parameters are unclear. We compared the effects of two training programmes, differing in rest interval duration, on muscle (vastus lateralis) metabolism and sprint performance. Sixteen men trained three times a week for 8 weeks, each training session comprising 2-3 sets of two 80-m sprints. Sprints were separated by 10 s (n = 8) or 1 min (n = 8). Both training programmes improved performance in the 100-, 200-, and 300-m sprints, but the improvement was greater in the 10-s group during the final 100 m of the 200- and 300-m runs. Independent of interval duration, training mitigated the drop of muscle ATP after two 80-m sprints. The drop in phosphocreatine and the increases in glucose-6-phosphate and fructose-6-phosphate after two 80-m sprints were greater in the 10-s group. In conclusion, training with a limited number of repeated short sprints (≤10 s) may be more effective in improving speed maintenance in 200- and 300-m runs when performed with a 1:1 rather than a 1:6 exercise-to-rest ratio. This may be due to a greater activation of glycolysis caused, in part, by the limited resynthesis of phosphocreatine during the very short rest interval.     

浙江省公安民警体育锻炼动机的研究

采用问卷调查法和数理统计法，对浙江省7个地市的550余名公安民警的体育锻炼现状和需求进行了调查，探索公安民警参与体育锻炼的动机结构及内部特征，了解、控制与预测民警的体育行为，克服影响他们参与体育锻炼的不利因素，推进、普及公安民警的体育锻炼。     

The acute effects of static stretching on peak force,peak rate of force development and muscle activity during single- and multiple-joint actions in older women

Abstract

The present study investigated the acute effects of static stretching on peak force, peak rate of force development and integrated electromyography (iEMG) in 27 older women (65 ± 4 years; 69 ± 9 kg; 157 ± 1 cm; 28 ± 4 kg · m^?2). The participants were tested during two exercises (leg press and knee extension) after two conditions: stretching and control. The data were collected on four days (counterbalanced with a 24-hour rest period). In the stretching condition, the quadriceps muscle was stretched (knee flexion) for three sets of 30 s with 30 s rest intervals. No significant difference was detected for peak force and peak rate of force development during the single- and multiple-joint exercises, regardless of the following interactions: condition (stretching and control) vs. time (pre x post x 10 x 20 x 30 minutes post; P > 0.05) and exercise vs. time (P > 0.05). Additionally, no significant interaction was found for the iEMG activity (condition vs. time; P > 0.05) in the single- and multiple-joint exercises. In conclusion, a small amount of stretching of an agonist muscle (quadriceps) did not affect the peak force, peak rate of force development and EMG activity in older women during single- and multiple-joint exercises.     

青岛市中学生阳光体育锻炼现状调查

青岛市中学生阳光体育锻炼时间基本能够保障,并且存在着明显的地域性特征.中学生对体育课满意度以及时体育教师的授课评价均不高,课外体育活动形式相对单一."阳光体育'在形式上得到基本实现的基础上,应当尽快向追求高质量发展.