The effects of static stretching programs on muscle strength and muscle architecture of the medial gastrocnemius

Introduction

Static stretching (SS) program are widely used in clinical and athletic settings. Many previous studies investigate the effect of SS program on muscle strength and muscle architecture (muscle thickness, and pennation angleh). However, no consensus has been reached about the effect of SS programs on muscle strength and muscle architecture. The aim of this study was to investigate the effects of 6-week SS programs performed at different weekly frequencies on muscle strength, muscle thickness and pennation angle at different ankle joint positions.

Methods

A total of 24 healthy male volunteers were performed 6-week SS programs (2,160 s of SS: 360 s/week*6 weeks) and were randomized to a group that performed SS once a week, or a group that performed SS three times per week. Total time under stretching was equated between groups. The muscle strength (maximum voluntary isometric contraction) at three different ankle joints were assessed before and after the 6-week SS program. In addition, muscle thickness and pennation angle were assessed by ultrasonography before and after 6-week SS program.

Results

There were no significant changes in all variables before and after the 6-week SS program, regardless of weekly frequency (p > 0.05).

Conclusions

Our results suggest that 6-week SS programs do not increase muscle strength or muscle architecture at different ankle joint positions, regardless of stretching frequency; however, no negative effect on these outcomes was observed, contrary to evidence on the immediate, detrimental effects of SS.

Dynamic stretching alone can impair slower velocity isokinetic performance of young male handball players for at least 24 hours

There are many adult studies reporting static stretch (SS)-induced deficits and dynamic stretch (DS) performance improvements shortly after the intervention. However, there is only a single study examining stretch-induced performance changes with youth at 24 hours' post-stretch. The objective of this study was to examine physiological responses of young trained athletes at 24-hours after experiencing SS or DS protocols. Eight young male, elite handball players (age: 16.1±5.1 years) were tested prior to-, 3-minutes and 24-hours following the three conditions (DS, SS, Control) in a randomized and counterbalanced order. Similar volumes of SS (2 repetitions of 75s for each leg) and DS (5 repetitions of 30s for each leg) involved one stretch each for the quadriceps and hamstrings. Tests included (i) two 4s maximal voluntary isometric contractions (MVC) at 60° of knee flexion with 2-min rest, (ii) two maximal isokinetic contractions each at 60°/sec and 300°/sec with 1-min rest, and (iii) two drop jumps with 30-sec rest. To simulate a full warm-up, dynamic activity including 5 minutes of aerobic cycling (70 rpm; 1 kilopond), 4 submaximal isometric contractions and 4 drop jumps were instituted before the pre-tests and following the interventions. Two-way repeated measures ANOVAs revealed that 1) both the SS and control conditions exhibited knee extensor 60°.s-1 (SS:-10.3%; p = 0.04, Control: -8.7%; p = 0.07) and 300°.s-1 (SS: -12.9%; p = 0.005, Control: -16.3%; p = 0.02) isokinetic deficits at post-test, 2) DS impaired knee flexor 60°.s-1 isokinetic work and power-related measures at post-test (Work: -10.1%; p = 0.0006; Power: -19.1%; p = 0.08) and at 24-hours' post-test (Work: 9.9%; p = 0.023; Power: -9.6%; p = 0.01), 3) DS (12.07% and 10.47%) and SS (13.7% and 14.6%) enhanced knee flexor 300°.s-1 isokinetic force and power-related measures compared to control. In conclusion, testing-induced knee extensor isokinetic impairments were counterbalanced by DS, however the hip flexion DS could have produced minor muscle damage for at least 24-hours decreasing knee flexor forces and power at 60°.s-1.

Non-pharmacological interventions to combat exercise-induced muscle damage, a little natural tax on work out

Debilitating pain, stiffness, tenderness, fatigue, impaired muscle function, lack of strength subsequent to exercise are not welcomed by those not accustomed to it. It may discourage an individual from participating in regular exercise. Numerou s ph armacological and non - pharmacological strategies have been used to alleviate symptoms of muscle soreness, muscle pain, improving muscle function, the range of motion and recovery time. Non-steroidal anti-inflammatory drugs are suggested to have a beneficial impact on muscle soreness, but fail to rejuvenate muscle weakness and range of motion coupled with muscle soreness. Furthermore, oral antiinflammatory drugs are widely used to mitigate muscle soreness symptoms, but chronic use can lead to different side effects in terms of peptic ulcer and liver toxicity. Non-pharmacological remedies and interventions can be a better choice. This narrative review is intended to provide insight into the non-pharmacological strategies to combat exercise-induced muscle damage.

Reliability of Sonographic Assessment of Biceps Femoris Distal Tendon Strain during Passive Stretching

The purpose of this study was to determine the intra-rater, inter-examiner and inter-observer reliability of biceps femoris long head (BFlh) tendon strain using ultrasound imaging. Nineteen patients (age: 20.4 ± 0.35 y) were tested twice with a 1-wk interval. Each session included passive stretching from three different hip positions. Tests were performed independently by two examiners while BFlh tendon displacement (mm) and strain (%) were manually extracted from ultrasound video footages by two observers. Intra-rater comparisons revealed an intra-class correlation coefficient (ICC_2,1) range of 0.87 to 0.98 and a variability less than 4.74%. Inter-examiner comparisons revealed an ICC_2,1 range of 0.83 to 0.99 and less than 4.69% variability. Inter-observer ICCs ranged from 0.93 to 0.97 with variability less than 4.89%. Using a well-defined scanning protocol, two experienced examiners attained high levels of intra-rater agreement, with similarly excellent results for inter-rater and inter-observer reliability for BFlh tendon displacement and strain.

NCAA strength and conditioning coach demographics, current practice trends and common injuries of athletes during strength and conditioning sessions

BACKGROUND

NCAA strength and conditioning coaches are responsible for the day-to-day conditioning and strength training of collegiate athletes. NCAA regulations will likely require all strength and conditioning coaches to have a strength and conditioning certification. NCAA strength and conditioning coaches have varied philosophies on exercise programming based on educational background. The study aims to further evaluate the backgrounds and exercise philosophies of NCAA strength and conditioning coaches.

METHODS

A survey (Survey Monkey®, Palo Alto, CA, USA) was distributed to NCAA strength and conditioning professionals to evaluate their education background, current practice trends, use of specific equipment and footwear, and what injuries occurred during sessions.

RESULTS

Of the 208 survey participants, 77.9% were male with an average age of 34.5±9.1 years old. An exercise-related bachelor's degree was held by 80.4% and an exercise-related master's degree by 72.4%. Over 89% had a strength and conditioning certification. Having a master's, bachelor's, or type strength and conditioning certification had no difference in 1-repetition maximal practice with athletes. Lower extremity injuries made up the highest percentage (58.9%) of injuries seen by NCAA Strength and Conditioning Coaches than lumbar spine injuries (16.7%). The five most common injuries reported during workouts were lumbar strain (N.=431, 14.7%), hamstring strain (N.=332, 11.3%), ankle sprain (N.=299, 10.2%), patellar tendonitis (N.=232, 7.9%), and shin splints (N.=226, 7.7%).

CONCLUSIONS

Collegiate education and certifications have impact on practice patterns of strength and conditioning coaches in the NCAA.

Rupture of Subcutaneous Peritoneal Dialysis Catheter by Stretching Exercise: A Case Report

Rupture of the peritoneal dialysis (PD) catheter is rare complication. Here, we report a case of catheter rupture that occurred because of exercise after partial catheter reimplantation.A 66-year-old man with a history of end-stage kidney disease secondary to diabetic nephropathy experienced refractory exit-site and tunnel infection. After the infected parts of the catheter were excised, a partial catheter reimplantation was performed. At the time of that surgery, a presternal location was selected for the new exit site, and a titanium extender was used to connect the two catheters. The patient was discharged on postoperative day 3, but was readmitted for a pericatheter leak 5 days later. Fluoroscopy performed to investigate the cause demonstrated a pericatheter leak from the connecting portion between the titanium extender and the catheter.Surgery performed to repair the leak revealed that the catheter had ruptured. We believe that the cause of the rupture was mechanical stress induced by the patient's stretching exercise program. The PD catheter was made of silicone rubber with high elasticity. Even when such resilient materials are used, we recommend that, to avoid PD catheter rupture after partial reimplantation, clinicians should discourage the patient from stretching excessively.

Effects of short duration static stretching on jump performance, maximum voluntary contraction, and various mechanical and morphological parameters of the muscle-tendon unit of the lower extremities

Purpose

Static stretching is used in sport practice but it has been associated with decrements in force and performance. Therefore, we examined the effect of short duration static stretch on the mechano-morphological properties of the m. vastus lateralis (VL) muscle tendon unit (MTU) and on the jumping performance.

Methods

Eight males and three females (mean ± SD, 25.5 ± 3.1 years) stretched their lower legs for a 15 or 60 s duration or acted as their own control without stretching in a randomized order. In a pre-post design, a passive movement (5°/s) and a maximum voluntary knee extension contraction (MVC) were performed on dynamometer while the VL tendon and aponeurosis was observed via ultrasound. Furthermore, the participants performed countermovement (CMJ) and squat jumps (SJ).

Results

Repeated measures ANOVA did not show significant differences in MVC, active and passive strain, stiffness, elongation, knee joint angle range, and jump performance between and within groups.

Conclusions

The applied stretch stimuli (15 or 60 s) were not sufficient to trigger adaptations in the mechano-morphological properties of the lower extremities MTU which therefore did neither affect jump performance nor MVC. As a possible mechanism, we hypothesized that the dose-time dependency effect of static stretch might have important implications when measuring functional parameters of the MTU and performance. Further examination is necessary to elucidate its impact in the examination of the MTU mechano-morphological properties.

A review of the acute effects of static and dynamic stretching on performance

An objective of a warm-up prior to an athletic event is to optimize performance. Warm-ups are typically composed of a submaximal aerobic activity, stretching and a sport-specific activity. The stretching portion traditionally incorporated static stretching. However, there are a myriad of studies demonstrating static stretch-induced performance impairments. More recently, there are a substantial number of articles with no detrimental effects associated with prior static stretching. The lack of impairment may be related to a number of factors. These include static stretching that is of short duration (<90 s total) with a stretch intensity less than the point of discomfort. Other factors include the type of performance test measured and implemented on an elite athletic or trained middle aged population. Static stretching may actually provide benefits in some cases such as slower velocity eccentric contractions, and contractions of a more prolonged duration or stretch-shortening cycle. Dynamic stretching has been shown to either have no effect or may augment subsequent performance, especially if the duration of the dynamic stretching is prolonged. Static stretching used in a separate training session can provide health related range of motion benefits. Generally, a warm-up to minimize impairments and enhance performance should be composed of a submaximal intensity aerobic activity followed by large amplitude dynamic stretching and then completed with sport-specific dynamic activities. Sports that necessitate a high degree of static flexibility should use short duration static stretches with lower intensity stretches in a trained population to minimize the possibilities of impairments.

Complete semimembranosus rupture following therapeutic stretching after a traumatic brain injury

Acute hamstring rupture is an uncommon event often occurring during high impact sports. Such events have not been previously reported during neurological rehabilitation. This case report describes a 30 year-old Chinese male presenting in a minimally responsive state 5 years after a severe traumatic brain injury. He was tetraplegic and bed-bound with spasticity involving all four limbs and flexion contracture of the right knee. During an episode of inpatient rehabilitation, he developed acute swelling and bruising of the posterior proximal thigh region associated with fever, tachycardia and diaphoresis. MRI showed a large soft tissue rim-enhancing mass in the right proximal hamstring muscle. During surgical exploration, complete rupture of the right semi-membranosus muscle was found without evidence of pus. The possible causative factors of hamstring rupture in this subject and a brief literature review are discussed. To the authors' knowledge, this is the first such reported case.

Acute first-time hamstring strains during slow-speed stretching: clinical, magnetic resonance imaging, and recovery characteristics

BACKGROUND

Hamstring strains can be of 2 types with different injury mechanisms, 1 occurring during high-speed running and the other during stretching exercises.

HYPOTHESIS

A stretching type of injury to the proximal rear thigh may involve specific muscle-tendon structures that could affect recovery time.

STUDY DESIGN

Case series (prognosis); Level of evidence, 2.

METHODS

Fifteen professional dancers with acute first-time hamstring strains were prospectively included in the study. All subjects were examined, clinically and with magnetic resonance imaging, on 4 occasions after injury: at day 2 to 4, 10, 21, and 42. The clinical follow-up period was 2 years.

RESULTS

All dancers were injured during slow hip-flexion movements with extended knee and experienced relatively mild acute symptoms. All injuries were located proximally in the posterior thigh close to the ischial tuberosity. The injury involved the semimembranosus (87%), quadratus femoris (87%), and adductor magnus (33%). All injuries to the semimembranosus involved its proximal free tendon. There were no significant correlations between clinical or magnetic resonance imaging parameters and the time to return to preinjury level (median, 50 weeks; range, 30-76 weeks).

CONCLUSION

Stretching exercises can give rise to a specific type of strain injury to the posterior thigh. A precise history and careful palpation provide the clinician enough information to predict a prolonged time until return to preinjury level. One factor underlying prolonged recovery time could be the involvement of the free tendon of the semimembranosus muscle.

Dynamics of indirect symptoms of skeletal muscle damage after stretch-shortening exercise

Healthy untrained men (age 20.4+/-1.7 years, n=20) volunteered to participate in an experiment in order to establish dynamics of indirect symptoms of skeletal muscle damage (ISMD) (decrease in maximal isometric voluntary contraction torque (MVCT) and torque evoked by electrostimulation at different frequencies and at different quadriceps muscle length, height (H) of drop jump (DJ), muscle soreness and creatine kinase (CK) activity in the blood) after 100 DJs from 0.75 m height performed with maximal intensity with an interval of 20s between the jumps (stretch-shortening exercise, SSE). All ISMDs remained even 72 h after SSE (P<0.01-0.001). The muscle experienced greater decrease (P<0.01) in torque evoked by electrostimulation (at low stimulation frequencies and at short muscle length in particular) after SSE than neuromuscular performance (MVCT and H of DJ) which demonstrated secondary decrease (P<0.01) in neuromuscular performance during the first 48 h after SSE. Within 24-72 h after the SSE the subjects felt an acute muscle pain (5-7 points approximately) and the CK activity in the blood was significantly increased up to 1200 IU/L (P<0.001). A significant correlation between decrease in MVCT and H of DJ 24-48 h after SSE on the one hand and muscle soreness registered within 24-48 h after SSE on the other was observed, whereas correlation between the other indirect symptoms of skeletal muscle damage was not significant.

Duration of stretch does not influence the degree of force loss following static stretching

AIM

There is an emerging body of knowledge indicating static stretching (SS) acutely and adversely affects muscle performance. The practical value of this research is limited considering the lengthy stretch durations under investigation. It is unclear if stretch durations typical of those used pre-exercise similarly affect muscle performance. The purpose of this study was to determine if SS using more representative stretch durations affects muscle performance and to establish if changes in muscle performance were influenced by the duration of stretch.

METHODS

Following 2 familiarization sessions, 16 recreationally trained males and females participated in 2 randomly ordered experimental sessions. In each session maximal effort hamstring performance was assessed prior to and immediately after 1 of 2 stretching protocols. During one of the protocols participants were required to hold each stretch for 15 s while stretch duration in the second protocol was 30 s. Both protocols consisted of 3 repetitions of 2 stretching exercises. A Kincom isokinetic dynamometer was used to assess hamstring performance during isometric, concentric, and eccentric actions.

RESULTS

For each of the three muscle actions a repeated measures ANOVA revealed a significant main effect of time (pre- vs poststretch, P<0.05) but no interaction effect (time x SS protocol). Furthermore, the stretch-induced deficits in muscle performance were consistent across muscle action type.

CONCLUSIONS

SS incorporating stretch durations typical of those employed pre-exercise were sufficient to impair muscle performance and the duration of stretch did not influence the degree of force loss. Inclusion of SS, even with short stretch durations, in preparation for strength activities is not appropriate.