Effects of dynamic stretching on strength, muscle imbalance, and muscle activation

Revisiting the stretch-induced force deficit: A systematic review with multilevel meta-analysis of acute effects

BACKGROUND

When recommending avoidance of static stretching prior to athletic performance, authors and practitioners commonly refer to available systematic reviews. However, effect sizes (ES) in previous reviews were extracted in major part from studies lacking control conditions and/or pre-post testing designs. Also, currently available reviews conducted calculations without accounting for multiple study outcomes, with ES: -0.03 to 0.10, which would commonly be classified as trivial.

METHODS

Since new meta-analytical software and controlled research articles have appeared since 2013, we revisited the available literatures and performed a multilevel meta-analysis using robust variance estimation of controlled pre-post trials to provide updated evidence. Furthermore, previous research described reduced electromyography activity-also attributable to fatiguing training routines-as being responsible for decreased subsequent performance. The second part of this study opposed stretching and alternative interventions sufficient to induce general fatigue to examine whether static stretching induces higher performance losses compared to other exercise routines.

RESULTS

Including 83 studies with more than 400 ES from 2012 participants, our results indicate a significant, small ES for a static stretch-induced maximal strength loss (ES = -0.21, p = 0.003), with high magnitude ES (ES = -0.84, p = 0.004) for stretching durations ≥60 s per bout when compared to passive controls. When opposed to active controls, the maximal strength loss ranges between ES: -0.17 to -0.28, p < 0.001 and 0.040 with mostly no to small heterogeneity. However, stretching did not negatively influence athletic performance in general (when compared to both passive and active controls); in fact, a positive effect on subsequent jumping performance (ES = 0.15, p = 0.006) was found in adults.

CONCLUSION

Regarding strength testing of isolated muscles (e.g., leg extensions or calf raises), our results confirm previous findings. Nevertheless, since no (or even positive) effects could be found for athletic performance, our results do not support previous recommendations to exclude static stretching from warm-up routines prior to, for example, jumping or sprinting.

Acute Effects of Slow, Moderate and Fast Tempo Dynamic Stretching Exercises on Power in Well-Trained Male Wrestlers

Due to the potential detrimental effects of static stretching exercises on subsequent muscle power performance, athletes and trainers have started to replace static stretching with dynamic stretching exercises in their training routines. However, there are no well-accepted guidelines regarding dynamic stretching variables, including tempo/velocity, volume (reps and sets), etc. Therefore, this study aimed to evaluate the acute effects of slow, moderate, and fast tempo dynamic stretching exercises on jump height, relative power, the reactive strength index, and leg stiffness in well-trained male wrestlers. Seventeen wrestlers (aged 20.00 ± 4.06 years, wrestling experience 6.00 ± 3.09 years, and training volume per week 10.00 ± 5.69 hours) took part in the experiment under four conditions (control session, slow tempo dynamic stretching, moderate tempo dynamic stretching, and fast tempo dynamic stretching) on separate days with a 72-h interval in between, following a randomized, crossover study design. The control session consisted of a 10-min jog on a motor-driven treadmill at 6 km/h and a 0% slope. Dynamic stretching sessions consisted of seven dynamic stretching exercises performed at 50 bpm, 100 bpm, and 120 bpm, following a 5-min warm-up on a treadmill at 6 km/h and a 0% slope. After each condition, wrestlers performed a 2 x 30-s repeated vertical jump test with 5-min rest intervals in between. The best results for jump height, relative power, the reactive strength index, and leg stiffness were registered for statistical analysis. One-way repeated ANOVA results demonstrated that there were no significant differences in pairwise comparisons of all variables obtained after the four different conditions (p > 0.05). Overall, none of the slow, moderate, and fast tempo dynamic stretching exercises led to a change in repeated jump performance of well-trained male athletes. Further studies are needed to clarify the acute effects of different tempo dynamic stretching on muscular performance in well-trained wrestlers.

Sitting Less, Recovering Faster: Investigating the Relationship between Daily Sitting Time and Muscle Recovery following Intense Exercise: A Pilot Study

(1) There is growing concern surrounding the adverse effects of prolonged sitting on health, yet its impact on post-exercise recovery remains relatively unexplored. This study aimed to better understand the potential influence of habitual prolonged sitting on recovery time and the unfavorable impact prolonged sitting may have on time to recovery, as assessed by muscle damage and inflammatory markers and an isokinetic dynamometer. (2) Nine college-age men (mean age ± SD = 22.1 ± 3.1 years, body mass = 80.9 ± 15.7 kg, height = 171 ± 9.0 cm, Body Mass Index (BMI) = 27.6 ± 4.9 kg·m2) participated in an exhaustive exercise protocol. Creatine Kinase (CK), Myoglobin (Mb), C-Reactive Protein (CRP), White Blood Cell Count (WBC), Peak Torque (PT), and muscle soreness were measured at baseline and 0, 24, 48, and 72 h post-exercise. Dietary and exercise logs were maintained during the 5-day testing procedure. (3) No significant differences were observed in muscle damage markers (CK [p = 0.068] and Mb [p = 0.128]), inflammatory markers (CRP [p = 0.814] and WBC [p = 0.140]), or PT [p = 0.255]) at any time point. However, a significant positive correlation was found between daily sitting time and the percent increase in CK concentration from 0 h to 72 h (r = 0.738, p = 0.023). Strong correlations were also noted between prolonged sitting and percent change in Mb concentration at 48 h (r = 0.71, p = 0.033) and 72 h (r = 0.889, p = 0.001). There was a significant two-way interaction for time × velocity (p = 0.043) for PT with a simple main effect for time at 60°·s-1 (p = 0.038). No significant associations were detected between daily carbohydrate or protein intake and recovery markers (p > 0.05). (4) The findings suggest minimizing daily sitting time may expedite and potentially aid muscle recovery after an intense exercise bout, although further research is warranted to validate these findings.

Exercise-induced modulation of Interferon-signature: a therapeutic route toward management of Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is a multisystemic autoimmune disorder characterized by flares-ups/remissions with a complex clinical picture related to disease severity and organ/tissue injury, which, if left untreated, may result in permanent damage. Enhanced fatigue and pain perception, worsened quality of life (QoL) and outcome are constant, albeit symptoms may differ. An aberrant SLE immunoprofiling, note as "interferon (IFN)α-signature", is acknowledged to break immunotolerance. Recently, a deregulated "IFNγ-signature" is suggested to silently precede/trigger IFNα profile before clinical manifestations. IFNα- and IFNγ-over-signaling merge in cytokine/chemokine overexpression exacerbating autoimmunity. Remission achievement and QoL improvement are the main goals. The current therapy (i.e., corticosteroids, immunosuppressants) aims to downregulate immune over-response. Exercise could be a safe treatment due to its ever-emerging ability to shape and re-balance immune system without harmful side-effects; in addition, it improves cardiorespiratory capacity and musculoskeletal strength/power, usually impaired in SLE. Nevertheless, exercise is not yet included in SLE care plans. Furthermore, due to the fear to worsening pain/fatigue, SLE subjects experience kinesiophobia and sedentary lifestyle, worsening physical health. Training SLE patients to exercise is mandatory to fight inactive behavior and ameliorate health. This review aims to focus the attention on the role of exercise as a non-pharmacological therapy in SLE, considering its ability to mitigate IFN-signature and rebalance (auto)immune response. To this purpose, the significance of IFNα- and IFNγ-signaling in SLE etiopathogenesis will be addressed first and discussed thereafter as biotarget of exercise. Comments are addressed on the need to make aware all SLE care professional figures to promote exercise for health patients.

Potential Effects of Dynamic Stretching on Injury Incidence of Athletes: A Narrative Review of Risk Factors

The use of dynamic stretching as a replacement for static stretching in the warm-up is widespread based on the reports of static stretching-induced performance impairments. While acute and chronic static stretching has been reported to reduce musculotendinous injuries, especially with explosive and change of direction actions, the influence of dynamic stretching on injury incidence lacks a similar volume of literature for acute and chronic responses. It was the objective of this narrative review to examine the acute and training effects of dynamic stretching on injury incidence and possible moderating variables such as dynamic stretching effects on range of motion, strength, balance, proprioception, muscle morphology, and psycho-physiological responses. One study demonstrated no significant difference regarding injury incidence when comparing a dynamic stretching-only group versus a combined dynamic stretching plus static stretching group. The only other study examined functional dynamic stretching training with injured dancers and reported improved ankle joint stability. However, several studies have shown that dynamic activity with some dynamic stretching exercises within a warm-up consistently demonstrates positive effects on injury incidence. Regarding moderating variables, while there is evidence that an acute bout of dynamic stretching can enhance range of motion, the acute and training effects of dynamic stretching on strength, balance, proprioception, and musculotendinous stiffness/compliance are less clear. The acute effects of dynamic stretching on thixotropic effects and psycho-physiological responses could be beneficial for injury reduction. However, the overall conflicting studies and a lack of substantial literature compared with SS effects points to a need for more extensive studies in this area.

Acute Effects of Combining Dynamic Stretching and Vibration Foam Rolling Warm-up on Lower-Limb Muscle Performance and Functions in Female Handball Players

ABSTRACT

Chen, CH, Chiu, CH, Tseng, WC, Wu, CY, Su, HH, Chang, CK, and Ye, X. Acute effects of combining dynamic stretching and vibration foam rolling warm-up on lower-limb muscle performance and functions in female handball players. J Strength Cond Res 36(4): 920-926, 2022-The purpose of this study was to compare the acute effects of 3 warm-up protocols on knee flexor and extensor muscles performance in elite female collegiate handball players. Ten female handball players with poor hamstring flexibility completed 3 randomly sequenced experimental visits. During each visit, a different warm-up protocol (general running warm-up [GW], dynamic stretching [DS], or DS combined with vibration foam rolling [DS + VR]) was delivered before the subsequent tests: quadriceps and hamstring muscle stiffness, knee extension and flexion range of motion (ROM), knee joint position sense, knee extension and flexion isokinetic strength with hamstring-quadriceps strength ratio, and muscle endurance during fatiguing exercise. Relative to the GW, the DS + VR protocol resulted in significantly greater knee flexion ROM (mean ± SD : DS + VR = 79.4° ± 7.7°; GW = 69.3° ± 9.6°) and lower hamstring muscle stiffness (DS + VR = 253.33 ± 36.20 N·m -1 ; GW = 292.89 ± 24.28 N·m -1 ). In addition, the DS + VR protocol also yielded greater hamstring muscle endurance than the other 2 protocols did (fatigue percentage: DS + VR = 30.24% ± 10.84%; GW = 41.40% ± 8.98%; DS = 42.22% ± 9.42%). Therefore, the results of this experiment suggest that it can be more beneficial for the female handball players to warm-up with the DS + VR, rather than the GW and DS protocols.

Acute effects of long-lasting stretching and strength training on maximal strength and flexibility in the calf muscle

The so-called “stretch-induced force deficit” is known from a large amount of research. There are many theories trying to explain the stretch-induced force deficit and increases in the range of motion (ROM) which all offer a stretch training-specific explanation. However, when performing a commonly used strength training session, a reduced maximum strength (MSt) capacity can be assumed as well. Based on this, the aim of the study is to investigate the tension-induced force deficit due to a suprathreshold strength or stretching training stimulus. Therefore, 71 participants (age: 24.1 ± 4.2 years, height: 176.3 ± 5.7 cm, weight: 74.1 ± 7.5 kg) were divided into three groups: static stretching group (SST), strength training group (STR), and control group (CG). To investigate possible mechanical tension-induced force deficits, SST performed a long-lasting static stretching intervention for 1 h using an orthosis, while STR executed a common strength training intervention (5 × 12 repetition) for the plantar flexors. The results show a significant reduction of measured MSt as well as increased ROM for both SST and STR following the interventions. Consequently, we found similar acute effects of stretching and strength training regarding MSt and flexibility. We conclude that the decreased MSt capacities can possibly be attributed to mechanical tension-induced damage of the muscle that is not linked to a specific training method. The improvements in flexibility found in both intervention groups might be attributed to warm up effects when inducing high mechanical tension to large ankle joint angles.

Effect of different rehabilitation training timelines to prevent shoulder dysfunction among postoperative breast cancer patients: study protocol for a randomized controlled trial

Introduction

Due to advancements in treatment, the survival of breast cancer (BC) patients has significantly improved. Improving the postoperative quality of life has become a widespread concern for patients and doctors. At present, the staged rehabilitation training program for postoperative BC patients has been recognized. However, there is not yet a consensus about the optimal time to initiate rehabilitation training. We designed this study to investigate the optimal intervention times for postoperative BC patients to begin different stages of rehabilitation.

Design

This is a randomized controlled trial. Female participants with BC who are scheduled to undergo mastectomy, including unilateral total breast or breast-conserving surgery plus axillary lymph node dissection, will be enrolled in this study. The intervention includes the following: 200 participants will be allocated using a 1:1:1:1 ratio to the A, B, C, and D groups, which have four different rehabilitation timelines for four phases of rehabilitation exercises. A therapist will evaluate the patient’s overall health and then adjust the training intensity before initiating training. The assessments include upper limb mobility, grip, limb circumference, postoperative drainage volume (PDV), and pain. The training will last for 12 weeks, and patients will undergo follow-up twice within 6 weeks after discharge. Outcomes include the following: Constant-Murley Score (CMS) is the primary parameter. European Organization Research and Treatment of Cancer Quality of Life Questionnaire-BR23 (EORTC QLQ-BR23), SF-36, range of motion (ROM), strength, grip, circumference, PDV, and pain are the secondary parameters. All enrolled subjects will be assessed at 1 day, 3 days, 1 week, and 2, 3, 6, 9, 12, and 18 weeks after the surgery.

Discussion

This is a randomized controlled trial to evaluate the effect of different rehabilitation training timelines to prevent shoulder dysfunction among postoperative patients with BC. If the results are confirmed, this study will establish an optimal timeline for postoperative BC rehabilitation.

Trial registration

ClinicalTrials.gov NCT03658265. Registered on September 2018.

Static stretch and dynamic muscle activity induce acute similar increase in corticospinal excitability

Even though the acute effects of pre-exercise static stretching and dynamic muscle activity on muscular and functional performance have been largely investigated, their effects on the corticospinal pathway are still unclear. For that reason, this study examined the acute effects of 5×20 s of static stretching, dynamic muscle activity and a control condition on spinal excitability, corticospinal excitability and plantar flexor neuromuscular properties. Fifteen volunteers were randomly tested on separate days. Transcranial magnetic stimulation was applied to investigate corticospinal excitability by recording the amplitude of the motor-evoked potential (MEP) and the duration of the cortical silent period (cSP). Peripheral nerve stimulation was applied to investigate (i) spinal excitability using the Hoffmann reflex (H_max), and (ii) neuromuscular properties using the amplitude of the maximal M-wave (M_max) and corresponding peak twitch torque. These measurements were performed with a background 30% of maximal voluntary isometric contraction. Finally, the maximal voluntary isometric contraction torque and the corresponding electromyography (EMG) from soleus, gastrocnemius medialis and gastrocnemius lateralis were recorded. These parameters were measured immediately before and 10 s after each conditioning activity of plantar flexors. Corticospinal excitability (MEP/M_max) was significantly enhanced after static stretching in soleus (P = 0.001; ES = 0.54) and gastrocnemius lateralis (P<0.001; ES = 0.64), and after dynamic muscle activity in gastrocnemius lateralis (P = 0.003; ES = 0.53) only. On the other hand, spinal excitability (H_max/M_max), cSP duration, muscle activation (EMG/M_max) as well as maximal voluntary and evoked torque remained unaltered after all pre-exercise interventions. These findings indicate the presence of facilitation of the corticospinal pathway without change in muscle function after both static stretching (particularly) and dynamic muscle activity.

Effect of Static Stretching, Dynamic Stretching, and Myofascial Foam Rolling on Range of Motion During Hip Flexion: A Randomized Crossover Trial

Siebert, T, Donath, L, Borsdorf, M, and Stutzig, N. Effect of static stretching, dynamic stretching, and myofascial foam rolling on range of motion during hip flexion: A randomized crossover trial. J Strength Cond Res XX(X): 000-000, 2020-Static and dynamic stretching (DS) are commonly used in sports and physical therapy to increase the range of motion (ROM). However, prolonged static stretching (SS) can deteriorate athletic performance. Alternative methods to increase ROM are thus needed. Foam rolling (FR) may initiate muscle relaxation, improve muscular function, physical performance, and ROM. Previous studies that examined effects of FR on ROM did not control for increased tissue compliance or shifted pain threshold. In this study, the isolated influence of altered tissue compliance on ROM after FR, SS, and DS was investigated using a randomized crossover design. Hip flexion ROM at given joint torques before and after SS, DS, and FR was randomly assessed in 14 young male adults (age: 23.7 +/- 1.3 years; height: 182 +/- 8 cm; body mass: 79.4 +/- 6.9 kg). Hip flexion ROM was measured in the sagittal plane with the subjects lying in a lateral position (no gravitational effects on ROM measurements). Surface electromyographic (EMG) analysis of 2 representative hip extensors (M. biceps femoris and M. semitendinosus) was applied to control for active muscle contribution during ROM measurements. Significant increases in ROM for SS (3.8 +/- 1.1[degrees]; p < 0.001) and DS (3.7 +/- 1.8[degrees]; p < 0.001) were observed, but not for FR (0.8 +/- 3.1[degrees]; p = 0.954). Because stretch forces on tendon and muscle tissue during SS and DS predominately act in longitudinal direction, FR induces mainly transversal forces in the muscle tissue. Thus, increased ROM after FR reported in the literature is more likely due to a shift in the pain threshold. These results provide a better understanding of differential loading conditions during SS, DS, and FR for coaches and practitioners.

Differential Effects of Different Warm-up Protocols on Repeated Sprints-Induced Muscle Damage

Chen, CH, Ye, X, Wang, YT, Chen, YS, and Tseng, WC. Differential effects of different warm-up protocols on repeated sprints-induced muscle damage. J Strength Cond Res 32(11): 3276-3284, 2018-The purpose of this investigation was to examine whether adding a set of hamstring resistance exercise or dynamic stretching to a regular running-based warm-up before a bout of repeated sprints provides protective effects against the sprinting-induced muscle damage. Twelve elite tennis players participated in this study. After the familiarization, subjects completed 3 separate randomly sequenced experimental visits, during which 3 different warm-up interventions were performed before the muscle-damaging protocol (12 sets of 30-m maximal repeated sprints): 5 minutes of running (control); control with single leg slide curl (SLC); and control with active hamstring stretching (AHS). Before, immediately (POST0), 1 day (POST1), and 2 days after (POST2) the sprints, hip flexion passive range of motion, hamstring muscle thickness and pennation angle, muscle stiffness, and knee flexion concentric peak torque were measured. Repeated sprints have induced muscle damage in all 3 visits. For AHS, the muscle thickness and stiffness values at POST2 were significantly lower than those of other 2 protocols. In addition, the decrements of concentric strength at POST0, POST1, and POST2 for AHS were also significantly less than those of control and SLC. Therefore, adding a set of dynamic hamstrings stretching to a regular warm-up protocol before repeated sprints has protective effect on the sprinting-induced muscle damage. Athletes whose competitions are densely scheduled (e.g., tennis player in a tournament) may take advantage of this strategy to facilitate muscle recovery from the potential muscle damage, thus, to get maximal recovery for the subsequent competitions.

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.

Selective effect of static stretching, concentric contractions, and a balance task on ankle force sense

Proper ankle motor control is critical for balance in the human body during functional activities such as standing, walking, and running. Different exercise modalities are often performed during the same training session where earlier activities may influence later ones. The purpose of the current study was to determine the acute effects of different exercise modalities on ankle force sense. Seventeen subjects performed four different intervention protocols (static stretching, balance task, concentric contractions, and control) in random order. Each session comprised measurements before and after the intervention protocol of the force sense of the ankle plantar flexors (PF) and dorsal flexors (DF) at 10% and 30% of maximal voluntary isometric contraction (MVC). Absolute errors (AE) were calculated separately for each force level and muscle group. An overall PF error (PF-SUM = PF at 10%MVC + PF at 30%MVC), DF error (DF-SUM = DF at 10%MVC + DF at 30%MVC) and ankle error (PF-DF-SUM = PF-SUM + DF-SUM) were also calculated. The main effect of time generally revealed that ankle force sense was significantly reduced after static stretching (PF-DF-SUM: Pre: 6.11±2.17 Nm, Post: 8.03±3.28 Nm; p < 0.05), but no significant differences were observed for the concentric contractions (PF-DF-SUM: Pre: 6.01±1.97 Nm, Post: 6.50±2.28 Nm) and the balance task (PF-DF-SUM: Pre: 5.25±1.97 Nm, Post: 5.50±1.26 Nm). The only significant interaction was observed for the PF-DF-SUM (F = 4.48, p = 0.008) due to greater error scores after stretching (+31.4%) compared to the concentric (+8.2%), balance (+4.8%), and control (-3.5%) conditions. Based on these results, static stretching should not be performed before activities that require a high ankle force sense such as balance, coordination, and precision tasks.

Acute Effects of Proprioceptive Neuromuscular Facilitation on Peak Torque and Muscle Imbalance

BACKGROUND

The effects of proprioceptive neuromuscular facilitation (PNF) stretching on muscle imbalance are not fully understood. The aim of this study was to examine the acute effects of PNF stretching on knee extension and flexion peak torque (PT), as well as the conventional and functional hamstrings to quadriceps (H:Q) ratios.

METHODS

Fifteen men (age = 22 ± 1 years; body mass = 76 ± 12 kg; height = 176 ± 7 cm) and fifteen women (age = 22 ± 2 years; body mass = 63 ± 8 kg; height = 161 ± 5 cm) performed concentric quadriceps and hamstrings, and eccentric hamstrings muscle actions at different angular velocities (60, 180, and 300°·s^-1 concentric; 60 and 180°·s^-1 eccentric) before and after a bout of PNF stretching, and a control condition.

RESULTS

Neither PNF or control conditions affected concentric PT or H:Q ratios (p > 0.05), apart from knee extension at 60°·s^-1 in men (p = 0.001). However, there was a reduction in hamstrings eccentric PT in both control and PNF conditions for men and women (p = 0.003).

CONCLUSIONS

PNF stretching of the hamstrings may not adversely affect the H:Q ratios, and consequently not negatively affect injury risk associated with muscular strength imbalances.

Acute Effects of Dynamic Stretching on Muscle Flexibility and Performance: An Analysis of the Current Literature

Stretching has long been used in many physical activities to increase range of motion (ROM) around a joint. Stretching also has other acute effects on the neuromuscular system. For instance, significant reductions in maximal voluntary strength, muscle power or evoked contractile properties have been recorded immediately after a single bout of static stretching, raising interest in other stretching modalities. Thus, the effects of dynamic stretching on subsequent muscular performance have been questioned. This review aimed to investigate performance and physiological alterations following dynamic stretching. There is a substantial amount of evidence pointing out the positive effects on ROM and subsequent performance (force, power, sprint and jump). The larger ROM would be mainly attributable to reduced stiffness of the muscle-tendon unit, while the improved muscular performance to temperature and potentiation-related mechanisms caused by the voluntary contraction associated with dynamic stretching. Therefore, if the goal of a warm-up is to increase joint ROM and to enhance muscle force and/or power, dynamic stretching seems to be a suitable alternative to static stretching. Nevertheless, numerous studies reporting no alteration or even performance impairment have highlighted possible mitigating factors (such as stretch duration, amplitude or velocity). Accordingly, ballistic stretching, a form of dynamic stretching with greater velocities, would be less beneficial than controlled dynamic stretching. Notwithstanding, the literature shows that inconsistent description of stretch procedures has been an important deterrent to reaching a clear consensus. In this review, we highlight the need for future studies reporting homogeneous, clearly described stretching protocols, and propose a clarified stretching terminology and methodology.

Dynamic stretching is not detrimental to neuromechanical and sensorimotor performance of ankle plantarflexors

The acute effects of two dynamic stretching (DS) protocols on changes in the ankle range of motion (RoM), neuromechanical, and sensorimotor properties of the plantarflexor muscle group were examined. Eighteen participants received slow (SDS) or fast dynamic stretching (FDS) on two separate days. Outcome measures were assessed pre- and 2 minutes post-interventions, and included maximum dorsiflexion angle, maximum isometric torque at neutral ankle position, maximum concentric and eccentric torques, force matching capacity, joint position sense and medial gastrocnemius muscle and tendon strain. Possibly and likely small increases in dorsiflexion RoM were observed after SDS (mean ± 90% confidence intervals; 1.8 ± 1.2°) and FDS (2.1 ± 1.2°), respectively. Very likely moderate decreases in muscle strain after SDS (-38.0 ± 20.6%) and possibly small decrease after FDS (-13.6 ± 21.2%) were observed. SDS resulted in a likely beneficial small increase in tendon strain (25.3 ± 29.7%) and a likely beneficial moderate increase after FDS (41.4 ± 44.9%). Effects on strength were inconsistent. Possibly small effect on positional error after SDS (-27.1 ± 37.5%), but no clear effect after FDS was observed. Both DS protocols increased RoM, and this was more due to an increase in tendon elongation rather than the muscle. However, SDS showed greater improvement than FDS in both neuromechanical and sensorimotor performance, and hence, SDS can be recommended as part of warm-up in sporting contexts.

Effects of Foam Rolling on Range of Motion, Peak Torque, Muscle Activation, and the Hamstrings-to-Quadriceps Strength Ratios

Madoni, SN, Costa, PB, Coburn, JW, and Galpin, AJ. Effects of foam rolling on range of motion, peak torque, muscle activation, and the hamstrings-to-quadriceps strength ratios. J Strength Cond Res 32(7): 1821-1830, 2018-To examine the effects of foam rolling (FR) on range of motion (ROM), peak torque (PT), hamstrings-to-quadriceps (H:Q) ratios, and muscle activation. Twenty-two recreationally active women (mean age ± SD = 21.55 ± 1.82 years, 161.91 ± 6.58 cm, 61.47 ± 10.54 kg) volunteered for this study. Participants performed pre- and posttests analyzing PT and surface electromyography (EMG) of their dominant limb, completing maximal knee extension and flexion at 3 different velocities. Participants foam rolled the hamstrings muscles or sat for the control condition between the pre- and posttests. Hamstrings ROM increased in the FR condition from (mean ± SE) 123.23 ± 3.49 to 126.41 ± 3.62° (p < 0.001) and decreased in the control condition from 118.82 ± 4.25 to 117.95 ± 4.29° (p = 0.013). Concentric hamstrings PT and conventional H:Q ratios decreased after both conditions, with smaller decreases after FR (p ≤ 0.05). No significant changes were found for eccentric hamstrings PT, eccentric hamstrings EMG, or functional H:Q ratios (p > 0.05). Foam rolling resulted in greater changes in hamstrings ROM without creating a deficit in PT or muscle activation when compared with the control group. When compared with other methods of stretching, FR may be beneficial in increasing ROM without decreasing functional H:Q ratios.

Acute Effects of Stretching on Leg and Vertical Stiffness During Treadmill Running

Pappas, PT, Paradisis, GP, Exell, TA, Smirniotou, AS, Tsolakis, CK, and Arampatzis, A. Acute effects of stretching on leg and vertical stiffness during treadmill running. J Strength Cond Res 31(12): 3417-3424, 2017-The implementation of static (SS) and dynamic (DS) stretching during warm-up routines produces significant changes in biological and functional properties of the human musculoskeletal system. These properties could affect the leg and vertical stiffness characteristics that are considered important factors for the success of athletic activities. The aim of this study was to investigate the influence of SS and DS on selected kinematic variables, and leg and vertical stiffness during treadmill running. Fourteen men (age: 22.58 ± 1.05 years, height: 1.77 ± 0.05 m, body mass: 72.74 ± 10.04 kg) performed 30-second running bouts at 4.44 m·s, under 3 different stretching conditions (SS, DS, and no stretching). The total duration in each stretching condition was 6 minutes, and each of the 4 muscle groups was stretched for 40 seconds. Leg and vertical stiffness values were calculated using the "sine wave" method, with no significant differences in stiffness found between stretching conditions. After DS, vertical ground reaction force increased by 1.7% (p < 0.05), which resulted in significant (p < 0.05) increases in flight time (5.8%), step length (2.2%), and vertical displacement of the center of mass (4.5%) and a decrease in step rate (2.2%). Practical durations of SS and DS stretching did not influence leg or vertical stiffness during treadmill running. However, DS seems to result in a small increase in lower-limb force production which may influence running mechanics.

Acute effects of different dynamic exercises on hamstring strain risk factors

The purpose of the study was to examine the acute effects of different dynamic exercise interventions on hamstring muscle performance. Thirty-six young men with poor hamstring flexibility were randomly assigned to three intervention groups: jogging combined with dynamic open kinetic chain stretching (DS), jogging combined with dynamic closed kinetic chain stretching (lunge with eccentric hamstring windmills, LEC), and jogging only (CON) groups. Hamstring flexibility, muscle stiffness (area under the curve, AUC), joint position sense (JPS), maximal eccentric strength (ECC), and angle of peak torque (APT) were recorded before and immediately after the exercise interventions. The results showed that the hamstring flexibility increased in DS (p < 0.001); muscle stiffness decreased in DS and was lower than jogging (p < 0.001). Moreover, ECC increased in LEC and was higher than jogging and DS (p < 0.001). APT was different among 3 groups (p < 0.001). Decreased accuracy of JPS was found in DS and jogging (p < 0.001). In conclusion, the dynamic closed kinetic chain stretching (LEC) as compared to open kinetic chain stretching (DS) or jogging group, may be an effective technique to enhance muscle performance during the pre-competition warm-up routine.

Effect of static and dynamic muscle stretching as part of warm up procedures on knee joint proprioception and strength

BACKGROUND

The importance of warm up procedures prior to athletic performance is well established. A common component of such procedures is muscle stretching. There is conflicting evidence regarding the effect of static stretching (SS) as part of warm up procedures on knee joint position sense (KJPS) and the effect of dynamic stretching (DS) on KJPS is currently unknown. The aim of this study was to determine the effect of dynamic and static stretching as part warm up procedures on KJPS and knee extension and flexion strength.

METHODS

This study had a randomised cross-over design and ten healthy adults (20±1years) attended 3 visits during which baseline KJPS, at target angles of 20° and 45°, and knee extension and flexion strength tests were followed by 15min of cycling and either a rest period (CON), SS, or DS and repeat KJPS and strength tests. All participants performed all conditions, one condition per visit.

RESULTS

There were warm up×stretching type interactions for KJPS at 20° (p=0.024) and 45° (p=0.018), and knee flexion (p=0.002) and extension (p<0.001) strength. The SS and DS improved KJPS but CON condition did not and SS decreased strength. No change in strength was present for DS or CON.

CONCLUSIONS

Both SS and DS improve KJPS as part of pre-exercise warm up procedures. However, the negative impact of SS on muscle strength limits the utility of SS before athletic performance. If stretching is to be performed as part of a warm up, DS should be favoured over SS.

Influence of chronic stretching on muscle performance: Systematic review

The aim of the current study was to investigate the influence of chronic stretching on muscle performance (MP) by a systematic review. The search strategy included MEDLINE, PEDro, Cochrane CENTRAL, LILACS, and manual search from inception to June 2016. Randomized and controlled clinical trials, non-randomized, and single group studies that have analyzed the influence of flexibility training (FT) (using any stretching technique) on MP were included. Differently, studies with special populations (children, elderly, and people with any dysfunction/disease), and articles that have used FT protocols shorter than three weeks or 12 sessions were excluded. The MP assessment could have been performed by functional tests (e.g. jump, sprint, stretch-shortening cycle tasks), isometric contractions, and/or isotonic contractions. Twenty-eight studies were included out of 513. Seven studies evaluated MP by stretch-shortening cycle tasks, Ten studies evaluated MP by isometric contractions, and 13 studies assessed MP by isotonic contractions. We were unable to perform a meta-analysis due to the high heterogeneity among the included studies. In an individual study level analysis, we identified that 14 studies found positive effects of chronic stretching on MP. The improvements were observed only in functional tests and isotonic contractions, isometric contractions were not affected by FT. Therefore, FT might have an influence on dynamic MP. However, more studies are necessary to confirm whether FT can positively affect MP.

Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: a systematic review

Recently, there has been a shift from static stretching (SS) or proprioceptive neuromuscular facilitation (PNF) stretching within a warm-up to a greater emphasis on dynamic stretching (DS). The objective of this review was to compare the effects of SS, DS, and PNF on performance, range of motion (ROM), and injury prevention. The data indicated that SS- (-3.7%), DS- (+1.3%), and PNF- (-4.4%) induced performance changes were small to moderate with testing performed immediately after stretching, possibly because of reduced muscle activation after SS and PNF. A dose-response relationship illustrated greater performance deficits with ≥60 s (-4.6%) than with <60 s (-1.1%) SS per muscle group. Conversely, SS demonstrated a moderate (2.2%) performance benefit at longer muscle lengths. Testing was performed on average 3-5 min after stretching, and most studies did not include poststretching dynamic activities; when these activities were included, no clear performance effect was observed. DS produced small-to-moderate performance improvements when completed within minutes of physical activity. SS and PNF stretching had no clear effect on all-cause or overuse injuries; no data are available for DS. All forms of training induced ROM improvements, typically lasting <30 min. Changes may result from acute reductions in muscle and tendon stiffness or from neural adaptations causing an improved stretch tolerance. Considering the small-to-moderate changes immediately after stretching and the study limitations, stretching within a warm-up that includes additional poststretching dynamic activity is recommended for reducing muscle injuries and increasing joint ROM with inconsequential effects on subsequent athletic performance.

Acute bouts of upper and lower body static and dynamic stretching increase non-local joint range of motion

PURPOSE

There are conflicts in the literature concerning the crossover or non-local effects of stretching. The objective of this study was to evaluate whether static (SS) and dynamic (DS) stretching of the shoulders would affect hip flexor range of motion (ROM) and performance and reciprocally whether SS and DS of the lower body would affect shoulder extension ROM and performance.

METHODS

A randomized crossover study design examined the acute effects of upper and lower body SS and DS on lower and upper body performance measures, respectively. Experimental sessions included upper and lower body control tests, upper body (shoulder horizontal abduction) SS and lower body (hip abduction) SS, upper body (shoulder horizontal abduction and adduction) DS and lower body DS (hip abduction and adduction). Passive static and dynamic ROM (hip flexion, shoulder extension), leg flexor and elbow flexor maximal voluntary contraction isometric force, fatigue endurance and electromyography were measured.

RESULTS

There were significant shoulder ROM increases following lower body SS (P < 0.010, ∆% = 8.2%) and DS (P < 0.019, ∆% = 9%). There was a significant hip flexor ROM (P < 0.016, ∆% = 5.2%) increase following upper body SS. There were no significant main effects or interactions for dynamic ROM or muscle force and activation variables.

CONCLUSION

The lack of stretch-induced force and fatigue changes suggests that rather than a mechanical or neural drive mechanism, an enhanced stretch tolerance was likely the significant factor in the improved ROM.

Unilateral static and dynamic hamstrings stretching increases contralateral hip flexion range of motion

Static (SS) and dynamic stretching (DS) can lead to subsequent performance impairments or enhancement with the stretched limb. Crossover or non-local muscle fatigue (NLMF) refers to unilateral fatigue-induced impairments in a contralateral or non-exercised muscle. Whereas there are conflicting findings in the NLMF literature, there are few studies examining the effect of an acute bout of SS or DS on contralateral flexibility, torque or power. Fourteen highly trained subjects (means ± standard deviations: 18 ± 2 years; 179·4 ± 4·6 cm; 70·5 ± 6·3 kg; %body fat: 10·7 ± 2·5%) were tested before and following separate sessions of eight repetitions of 30 s of unilateral hip flexion SS or DS. Pre- and postintervention testing at 1 and 10 min included hip flexor range of motion (ROM), isokinetic leg flexion torque and power at 60°.s^-1 and 300°.s^-1 of the stretched and contralateral limbs. The stretched limb had a 6·3% (P = 0·01; ES: 0·91) ROM increase with DS at 10 min. The contralateral non-stretched hip flexors experienced ROM increases with SS of 5·7% (P = 0·02; ES: 0·68) from pretest to 1 min post-test, whereas DS showed 7·1% (P<0·0001; ES: 1·09) and 8·4% (P = 0·005; ES: 0·89) increases, respectively. There were no relative differences in ROM changes between conditions or limbs nor any stretch-induced changes in isokinetic torque or power. In conclusion, unilateral SS and DS augment contralateral limb ROM likely through an increased stretch tolerance.

Acute effects of different stretching techniques on the number of repetitions in a single lower body resistance training session

This study aimed to investigate the acute effects of passive static and ballistic stretching on maximal repetition performance during a resistance training session (RTS). Nine male subjects underwent three experimental conditions: ballistic stretching (BS); passive static stretching (PSS); and a specific warm-up (SW). The RTS was composed of three sets of 12RM for the following exercises: leg press 45 (LP), leg extension (LE), leg curl (LC), and plantar flexors (PF). Performance of six sessions was assessed 48 hours apart. The first visit consisted of a familiarization session including stretching methods and exercises used in the RTS. On the second and third visit, a strength test and retest were performed. During the fourth to the sixth visit, the volunteers randomly performed the following protocols: BS+RTS; PSS+RTS; or SW+RTS. For the sum of the RM number of each three-set exercise, significant differences were found between PSS vs. SW for the LP (p = 0.001); LE (p = 0.005); MF (p = 0.001); and PF (p = 0.038). For the comparison between the methods of stretching PSS vs. BS, significant differences were found only for the FP (p = 0.019). When analyzing the method of stretching BS vs. SW, significant differences were found for the LP (p = 0.014) and MF (p = 0.002). For the total sum of the RM number of three sets of the four exercises that composed the RTS, significant differences were observed (p < 0.05) in the following comparisons: PPS vs. SW (p = 0.001), PPS vs. BS (p = 0.008), and BS vs. SW (p = 0.002). Accordingly, the methods of passive static and ballistic stretching should not be recommended before a RTS.

Acute effects of static active or dynamic active stretching on eccentric-exercise-induced hamstring muscle damage

OBJECTIVES

To examine whether an acute bout of active or dynamic hamstring-stretching exercises would reduce the amount of muscle damage observed after a strenuous eccentric task and to determine whether the stretching protocols elicit similar responses.

DESIGN

A randomized controlled clinical trial.

METHODS

Thirty-six young male students performed 5 min of jogging as a warm-up and were allocated to 1 of 3 groups: 3 min of static active stretching (SAS), 3 min of dynamic active stretching (DAS), or control (CON). All subjects performed eccentric exercise immediately after stretching. Heart rate, core temperature, maximal voluntary isometric contraction, passive hip flexion, passive hamstring stiffness (PHS), plasma creatine kinase activity, and myoglobin were recorded at prestretching, at poststretching, and every day after the eccentric exercises for 5 d.

RESULTS

After stretching, the change in hip flexion was significantly higher in the SAS (5°) and DAS (10.8°) groups than in the CON (-4.1°) group. The change in PHS was significantly higher in the DAS (5.6%) group than in the CON (-5.7%) and SAS (-6.7%) groups. Furthermore, changes in muscle-damage markers were smaller in the SAS group than in the DAS and CON groups.

CONCLUSIONS

Prior active stretching could be useful for attenuating the symptoms of muscle damage after eccentric exercise. SAS is recommended over DAS as a stretching protocol in terms of strength, hamstring range of motion, and damage markers.