Influence of Long-Lasting Static Stretching on Maximal Strength, Muscle Thickness and Flexibility

The effect of a combined long-duration static stretching and resistance training regimen on a competitive bodybuilder: A case study

Both resistance training (RT) and long-duration, high-intensity stretching induce muscular adaptations; however, it is unknown whether the modalities are complementary or redundant, particularly in well-trained individuals. A case-study was conducted on a competitive bodybuilder implementing long-duration, high-intensity stretching of the plantar flexors (60 min 6x/week for 12 weeks) in conjunction with their habitual RT. Ultrasound muscle architecture (muscle thickness [MT], fascicle length [FL], and pennation angle [PA]) measurements were collected at multiple sites at four weekly baseline sessions, six (mid) and 12 (post1) weeks following the commencement of the intervention, and a week after the intervention (post2) while isometric strength and range of motion (RoM) were obtained once at baseline, mid, post1, and post2. 2SD band plots were constructed to determine meaningful changes in MT, FL, and PA from the four baseline measures while percentage and absolute change across each timepoint were calculated for all variables. From baseline to post 1, RoM, strength, and MT increased 25.9%, 11.4%, and 7.4%-23.4%, respectively, while four MT and two PA sites exceeded the threshold for meaningful change. The combined stretching and RT protocols resulted in flexibility, strength, and MT adaptations; however, findings should be generalized with caution given the case-study nature of our investigation.

Improving Golf Swing Kinematics in a 78-Year-Old Golfer with Lower Back Pain: A Case Report

BACKGROUND Due to the complexity of the golf swing, poor form affects performance and lead to injuries in the spine and extremities. The Titleist Performance Institute (TPI) has created a movement screen to identify a golfer's physical limitations. The TPI includes 16 movement patterns within a golfer's swing that could lead to poor performance, dysfunction, and pain. TPI recommends specific exercises to address any dysfunctions. CASE REPORT This case report examined the benefit of a TDI-specific exercise program for a 78-year-old man with a history of low back pain and decreasing golf performance. Treatments included 3 sessions over 10 weeks, including lumbar stabilization exercises, balance training, and manual therapy. The dependent variables were the TDI movement screen, Trackman Driver analysis, and 3D Kvest Swing analysis. The patient's main goal was to increase driving distance and be able to play a round of golf without pain. The patient's specific functional scale showed that trunk rotation, right shoulder mobility, and hamstring length improved. His TPI Fitness handicap decreased, and his Trackman Driver averages improved. CONCLUSIONS This case report demonstrates that the TDI movement screen and TDI-recommended exercises in combination with manual therapy improved a golfer's TPI composite score, overall performance, and kinematic sequencing. Although, based on a case report, cause and effect cannot be established, it does appear that interventions, in this case, contributed to a decrease in low back pain and self-reported disability, improved golf swing and performance, and met the patient's objectives.

Optimising the Dose of Static Stretching to Improve Flexibility: A Systematic Review, Meta-analysis and Multivariate Meta-regression

BACKGROUND

Static stretching is widely used to increase flexibility. However, there is no consensus regarding the optimal dosage parameters for increasing flexibility.

OBJECTIVES

We aimed to determine the optimal frequency, intensity and volume to maximise flexibility through static stretching, and to investigate whether this is moderated by muscle group, age, sex, training status and baseline level of flexibility.

METHODS

Seven databases (CINAHL Complete, Cochrane CENTRAL, Embase, Emcare, MEDLINE, Scopus, and SPORTDiscus) were systematically searched up to June 2024. Randomised and non-randomised controlled trials investigating the effects of a single session (acute) or multiple sessions (chronic) of static stretching on one or more flexibility outcomes (compared to non-stretching passive controls) among adults (aged ≥ 18 years) were included. A multi-level meta-analysis examined the effect of acute and chronic static stretching on flexibility outcomes, while multivariate meta-regression was used to determine the volume at which increases in flexibility were maximised.

RESULTS

Data from 189 studies representing 6654 adults (61% male; mean [standard deviation] age = 26.8 ± 11.4 years) were included. We found a moderate positive effect of acute static stretching on flexibility (summary Hedges' g = 0.63, 95% confidence interval 0.52-0.75, p < 0.001) and a large positive effect of chronic static stretching on flexibility (summary Hedges' g = 0.96, 95% confidence interval 0.84-1.09, p < 0.001). Neither effect was moderated by stretching intensity, age, sex or training status, or weekly session frequency and intervention length (chronic static stretching only) [p > 0.05]. However, larger improvements were found for adults with poor baseline flexibility compared with adults with average baseline flexibility (p = 0.01). Furthermore, larger improvements in flexibility were found in the hamstrings compared with the spine following acute static stretching (p = 0.04). Improvements in flexibility were maximised by a cumulative stretching volume of 4 min per session (acute) and 10 min per week (chronic).

CONCLUSIONS

Static stretching improves flexibility in adults, with no additional benefit observed beyond 4 min per session or 10 min per week. Although intensity, frequency, age, sex and training status do not influence improvements in flexibility, lower flexibility levels are associated with greater improvement following both acute and chronic static stretching. These guidelines for static stretching can be used by coaches and therapists to improve flexibility.

CLINICAL TRIAL REGISTRATION

PROSPERO CRD42023420168.

Chronic effects of a static stretching intervention program on range of motion and tissue hardness in older adults

Introduction

Clinically, knowing whether a static stretching (SS) intervention program conducted for several weeks can reduce passive muscle stiffness is important. Still, only a few previous studies have evaluated the chronic effects of an SS intervention program in older adults, and the potential relationship between ROM changes and muscle stiffness changes is still unclear. This study aimed to investigate the effects of a 10- week SS intervention partially supervised program on joint range of motion (ROM) and tissue hardness in older adults.

Methods

The SS intervention program was conducted at least three times a week for 10 weeks in the ankle plantar flexor muscles of 24 community-dwelling older adults (73.8 ± 5.1 years; height: 156.0 ± 6.8 cm; body mass: 52.7 ± 8.0 kg). The SS intervention program consisted of 4 × 30-s repetitions. Ankle joint dorsiflexion (DF) ROM and tissue hardness of the medial gastrocnemius were measured before and after the 10-week SS intervention program.

Results and discussion

The results showed that the 10-week SS intervention program significantly increased DF ROM (+9°, p < 0.01, Cohen's d = 1.37) and decreased tissue hardness (-0.9, p = 0.04, Cohen's d = -0.27). However, there was no significant correlation between these changes (r = 0.086, p = 0.561). The results of this study suggest that a 10-week SS intervention program can effectively increase DF ROM and decrease tissue hardness but that the increase in DF ROM is related to stretch tolerance rather than changes in tissue hardness.

Chronic Effects of Static Stretching Exercises on Skeletal Muscle Hypertrophy in Healthy Individuals: A Systematic Review and Multilevel Meta-Analysis

BACKGROUND

The chronic effect of static stretching (SS) on muscle hypertrophy is still unclear. This study aimed to examine the chronic effects of SS exercises on skeletal muscle hypertrophy in healthy individuals.

METHODS

A systematic literature search was conducted in the PubMed, Web of Science, Cochrane Library, and SPORTDiscus databases up to July 2023. Included studies examined chronic effects of SS exercise compared to an active/passive control group or the contralateral leg (i.e., utilizing between- or within-study designs, respectively) and assessed at least one outcome of skeletal muscle hypertrophy in healthy individuals with no age restriction.

RESULTS

Twenty-five studies met the inclusion criteria. Overall, findings indicated an unclear effect of chronic SS exercises on skeletal muscle hypertrophy with a trivial point estimate (standardised mean difference [SMD] = 0.118 [95% prediction interval [95% PI] = - 0.233 to 0.469; p = 0.017]) and low heterogeneity (I2 = 24%). Subgroup analyses revealed that trained individuals (β = 0.424; 95% PI = 0.095 to 0.753) displayed larger effects compared to recreationally trained (β = 0.115; 95% PI = - 0.195 to 0.425) and sedentary individuals (β = - 0.081; 95% PI = - 0.399 to 0.236). Subanalysis suggested the potential for greater skeletal muscle hypertrophy in samples with higher percentages of females (β = 0.003, [95% confidence interval [95% CI] = - 0.000 to 0.005]). However, the practical significance of this finding is questionable. Furthermore, a greater variety of stretching exercises elicited larger increases in muscle hypertrophy (β = 0.069, [95% CI = 0.041 to 0.097]). Longer durations of single stretching exercises (β = 0.006, [95% CI = 0.002 to 0.010]), time under stretching per session (β = 0.006, [95% CI = 0.003 to 0.009]), per week (β = 0.001, [95% CI = 0.000 to 0.001]) and in total (β = 0.008, [95% CI = 0.003 to 0.013]) induced larger muscle hypertrophy. Regarding joint range of motion, there was a clear positive effect with a moderate point estimate (β = 0.698; 95% PI = 0.147 to 1.249; p < 0.001) and moderate heterogeneity (I2 = 43%). Moreover, findings indicated no significant association between the gains in joint range of motion and the increase in muscle hypertrophy (β = 0.036, [95% CI = - 0.123 to 0.196]; p = 0.638).

CONCLUSIONS

This study revealed an overall unclear chronic effect of SS on skeletal muscle hypertrophy, although interpretation across the range of PI suggests a potential modest beneficial effect. Subgroup analysis indicated larger stretching-induced muscle gains in trained individuals, a more varied selection of SS exercises, longer mean duration of single stretching exercise, increased time under SS per session, week, and in total, and possibly in samples with a higher proportion of females. From a practical perspective, it appears that SS exercises may not be highly effective in promoting skeletal muscle hypertrophy unless a higher duration of training is utilized. PROSPERO registration number: CRD42022331762.

Acute and chronic effects of stretching on balance: a systematic review with multilevel meta-analysis

Introduction

Balance is a multifactorial construct with high relevance in, e.g., everyday life activities. Apart from sensorimotor control, muscle strength and size are positively linked with balance performance. While commonly trained for via resistance training, stretch training has emerged as a potential substitution in specific conditions. However, no review has investigated potential effects of stretching on balance, yet.

Methods

PubMed, Web of Science and Scopus were searched with inception to February, 2024. Studies were included if they examined acute and/or chronic effects of any stretching type against passive and/or active controls on balance parameters - without any population-related restrictions concerning sex/gender, age, health status, activity level. Methodological quality was assessed using PEDro scale. Meta-analyses were performed if two or more studies reported on the same outcome. Certainty of evidence was determined based on GRADE criteria.

Results

Eighteen acute and eleven chronic effect studies were included. Stretching studies exhibited significant improvements for sway parameters with eyes open against passive controls of moderate magnitude for chronic (ES: 0.63, p = 0.047) and of small magnitude for acute studies (ES: 0.21, p = 0.032). Most other subgroups against passive controls as well as actively-controlled comparisons resulted in trivial and/or non-significant effects.

Conclusion

Even though some pooled effects slightly reached the level of significance, the overall results are biased by (very) low certainty of evidence (GRADE criteria downgrading for risk of bias, imprecision, publication bias). Moderators suggested by literature (strength, muscle size, flexibility, proprioception) were rarely assessed, which prevents conclusive final statements and calls for further, high quality evidence to clarify potential mechanisms-if any exist.

The effects of static and dynamic stretching on deep fascia stiffness: a randomized, controlled cross-over study

AIM

Previous stretching studies mostly investigated effects on the skeletal muscle but comprehensive explorations regarding the role of the connective tissue are scarce. Since the deep fascia has been demonstrated to be sensitive to mechanical tension, it was hypothesized that the fascia would also respond to stretching, contributing to enhanced range of motion (ROM).

METHODS

Forty (40) recreationally active participants (male: n = 25, female: n = 15) were included in the randomized controlled cross-over trial and allocated to different groups performing 5 min static (STAT) or dynamic (DYN) plantar flexor stretching or control condition (CC) in a random order. Pre- and immediately post-intervention, muscle and fascia stiffness, as well as muscle and fascia thickness were measured using high-resolution ultrasound and strain elastography. ROM was assessed in the ankle joint via the knee to wall test (KtW) and goniometer.

RESULTS

STAT reduced both, muscle and fascia stiffness (d = 0.78 and 0.42, p < 0.001, respectively), while DYN did not reduce stiffness compared to the control condition (p = 0.11-0.41). While both conditions showed significant increases in the KtW (d = 0.43-0.46, p = 0.02-0.04), no significant differences to the CC were observed for the isolated ROM testing (p = 0.09 and 0.77). There was a small correlation between fascia stiffness decreases and ROM increases (r = - 0.25, p = 0.006) but no association was found between muscle stiffness decreases and ROM increases (p = 0.13-0.40).

CONCLUSION

Our study is the first to reveal stretch-induced changes in fascia stiffness. Changes of fascia`s but not muscle`s mechanical properties may contribute to increased ROM following stretching.

Static Stretch Training versus Foam Rolling Training Effects on Range of Motion: A Systematic Review and Meta-Analysis

BACKGROUND

Long-term static stretching as well as foam rolling training can increase a joint's range of motion (ROM). However, to date, it is not clear which method is the most effective for increasing ROM.

OBJECTIVE

The purpose of this systematic review and meta-analysis was to compare the effects of static stretching and foam rolling training on ROM.

METHODS

The literature search was performed in PubMed, Scopus, and Web of Science to find the eligible studies. Eighty-five studies (72 on static stretching; and 13 on foam rolling) were found to be eligible with 204 effect sizes (ESs). For the main analyses, a random-effect meta-analysis was applied. To assess the difference between static stretching and foam rolling, subgroup analyses with a mixed-effect model were applied. Moderating variables were sex, total intervention duration, and weeks of intervention.

RESULTS

Static stretch (ES =  - 1.006; p < 0.001), as well as foam rolling training (ES =  - 0.729; p = 0.001), can increase joint ROM with a moderate magnitude compared with a control condition. However, we did not detect a significant difference between the two conditions in the subgroup analysis (p = 0.228). When the intervention duration was ≤ 4 weeks, however, a significant change in ROM was shown following static stretching (ES =  - 1.436; p < 0.001), but not following foam rolling (ES =  - 0.229; p = 0.248). Thus, a subgroup analysis indicated a significant favorable effect with static stretching for increasing ROM compared with foam rolling (p < 0.001) over a shorter term (≤ 4 weeks). Other moderator analyses showed no significant difference between static stretch and foam rolling training on ROM.

CONCLUSIONS

According to the results, both static stretching and foam rolling training can be similarly recommended to increase joint ROM, unless the training is scheduled for ≤ 4 weeks, in which case static stretching demonstrates a significant advantage. More studies are needed with a high-volume foam rolling training approach as well as foam rolling training in exclusively female participants.

Stressing the Relevance of Differentiating between Systematic and Random Measurement Errors in Ultrasound Muscle Thickness Diagnostics

BACKGROUND

The majority of studies that explore changes in musculature following resistance training interventions or examine atrophy due to immobilization or sarcopenia use ultrasound imaging. While most studies assume acceptable to excellent reliability, there seems to be unawareness of the existing absolute measurement errors. As early as 1998, methodological research addressed a collective unawareness of the random measurement error and its practical indications. Referring to available methodological approaches, within this work, we point out the limited value of focusing on relative, correlation-based reliability indices for the interpretability in scientific research but also for clinical application by assessing 1,512 muscle thickness values from more than 400 ultrasound images. To account for intra- and inter-day repeatability, data were collected on two consecutive days within four testing sessions. Commonly-stated reliability values (ICC, CV, SEM and MDC) were calculated, while evidence-based agreement analyses were applied to provide the accompanied systematic and random measurement error.

RESULTS

While ICCs in the range of 0.832 to 0.998 are in accordance with the available literature, the mean absolute percentage error ranges from 1.34 to 20.38% and the mean systematic bias from 0.78 to 4.01 mm (all p ≤ 0.013), depending on the measurement time points chosen for data processing.

CONCLUSIONS

In accordance with prior literature, a more cautious interpretation of relative reliability values should be based on included systematic and random absolute measurement scattering. Lastly, this paper discusses the rationale for including different measurement error statistics when determining the validity of pre-post changes, thus, accounting for the certainty of evidence.

Therapeutic Interventions for Prevention of Musculoskeletal Pain Among Orthopedic Surgeons

Orthopedic surgery is a physically demanding specialty. The factors contributing to musculoskeletal injury among surgeons often stem from positioning the patient, using non-ergonomic instruments, maintaining static postures, and performing repetitive movements. This article focuses on exercise techniques intended to combat the most common problematic static postures held during procedures. Each exercise explained in this article is organized into "preop," "intraop," and "postop" components. Preop includes strengthening movements, intraop provides postural recommendations, and postop focuses on mobilization and recovery. This article aims for efficient body conditioning, targeting the muscular posterior chain and supporting elements. [Orthopedics. 2024;47(4):e214-e216.].

Influence of 8-weeks of supervised static stretching or resistance training of pectoral major muscles on maximal strength, muscle thickness and range of motion

OBJECTIVES

Current research suggests static stretch-induced maximal strength increases and muscle hypertrophy with potential to substitute resistance-training routines. However, most studies investigated the plantar flexors. This study explored the effects of a static stretching program on maximal strength, hypertrophy and flexibility of the pectoralis major and compared the effects with those of traditional resistance training.

METHODS

Eighty-one (81) active participants were allocated to either a static stretching, strength-training or control group. Pectoralis stretching was applied 15 min/day, 4 days per week for 8 weeks, while resistance training trained 3 days per week, 5 × 12 repetitions.

RESULTS

There was an increase in all parameters (strength: p < 0.001, ƞ2 = 0.313, muscle thickness: p < 0.001, ƞ2 = 0.157-0.264, flexibility: p < 0.001, ƞ2 = 0.316) and a time*group interaction (strength: p = 0.001, ƞ2 = 0.154, muscle thickness: p = 0.008-0.001, ƞ2 = 0.117-0.173, flexibility: p < 0.001, ƞ2 = 0.267). Post-hoc testing showed no difference between both intervention groups regarding maximal strength and muscle thickness (p = 0.905-0.983, d = 0.036-0.087), while flexibility increased in the stretching group (p = 0.001, d = 0.789).

CONCLUSION

Stretching showed increases in maximal strength and hypertrophy, which were comparable with commonly used resistance training. Based on current literature, the influence of mechanical tension as the underlying mechanism is discussed. Furthermore, as equipment and comparatively long stretching durations are requested to induce meaningful strength increases in recreationally active participants, practical application seems limited to special circumstances.

Acute and Chronic Effects of Static Stretching on Intramuscular Hamstring Stiffness

Passive hamstring stiffness varies proximo-distally, resulting in inhomogeneous tissue strain during stretching that may affect localized adaptations and risk of muscle injuries. The purpose of the present study was to determine the acute and chronic effects of static stretching (SS) on intramuscular hamstring stiffness. Thirty healthy active participants had acute changes in passive biceps femoris (BF), semimembranosus (SM), and semitendinosus (ST) stiffness measured at 25% (proximal), 50% (middle), and 75% (distal) muscle length, using shear-wave elastography, immediately after SS. Participants then completed 4 weeks of either a SS intervention (n = 15) or no intervention (CON, n = 15) with stiffness measured before and after the interventions. The acute and chronic effects of SS were compared between anatomical regions and between regions on the basis of their relative stiffness pre-intervention. Acutely, SS decreased stiffness throughout the BF and SM (p ≤ 0.05) but not the ST (p = 0.326). However, a regional effect of stretching was observed for SM and ST with greater reduction in stiffness occurring in stiffer muscular regions (p = 0.001-0.013). Chronically, SS increased BF and ST (p < 0.05), but not SM (p = 0.422) stiffness compared with CON, but no regional effect of stretching was observed in any muscle (p = 0.361-0.833). SS resulted in contrasting acute and chronic effects, acutely decreasing stiffness in stiffer regions while chronically increasing stiffness. These results indicate that the acute effects of SS vary along the muscle's length on the basis of the relative stiffness of the muscle and that acute changes in stiffness from SS are unrelated to chronic adaptations.

Relative Cross-Education Training Effects of Male Youth Exceed Male Adults

ABSTRACT

Ben Othman, A, Anvar, SH, Aragão-Santos, JC, Behm, DG, and Chaouachi, A. Relative cross-education training effects of male youth exceed male adults. J Strength Cond Res 38(5): 881-890, 2024-Cross-education has been studied extensively with adults, examining the training effects on contralateral homologous muscles. There is less information on the cross-education effects on contralateral heterologous muscles and scant information comparing these responses between adults and youth. The objective was to compare cross-education training effects in male youth and adults to contralateral homologous and heterologous muscles. Forty-two male children (10-13-years) and 42 adults (18-21-years) were tested before and following an 8-week unilateral, dominant or nondominant arm, chest press (CP) training program or control group (14 subjects each). Unilateral testing assessed dominant and nondominant limb strength with leg press and CP 1 repetition maximum (1RM), knee extensors, elbow extensors (EE), elbow flexors, and handgrip maximum voluntary isometric contraction (MVIC) strength and shot put distance and countermovement jump height. Upper-body tests demonstrated large magnitude increases, with children overall exceeding adults ( p = 0.05- p < 0.0001, η2 : 0.51, 10.4 ± 11.1%). The dominant trained limb showed significantly higher training adaptations than the nondominant limb for the adults with CP 1RM ( p = 0.03, η2 : 0.26, 6.7 ± 11.5%) and EE ( p = 0.008, η2 : 0.27, 8.8 ± 10.3%) MVIC force. Unilateral CP training induced significantly greater training adaptations with the ipsilateral vs. contralateral limb ( p = 0.008, η2 : 0.93, 27.8 ± 12.7%). In conclusion, children demonstrated greater training adaptations than adults, upper-body strength increased with no significant lower-body improvements, and ipsilateral training effects were greater than contralateral training in adults.

Effects of Chronic Static Stretching on Maximal Strength and Muscle Hypertrophy: A Systematic Review and Meta-Analysis with Meta-Regression

BACKGROUND

Increases in maximal strength and muscle volume represent central aims of training interventions. Recent research suggested that the chronic application of stretch may be effective in inducing hypertrophy. The present systematic review therefore aimed to syntheisize the evidence on changes of strength and muscle volume following chronic static stretching.

METHODS

Three data bases were sceened to conduct a systematic review with meta-analysis. Studies using randomized, controlled trials with longitudinal (≥ 2 weeks) design, investigating strength and muscle volume following static stretching in humans, were included. Study quality was rated by two examiners using the PEDro scale.

RESULTS

A total of 42 studies with 1318 cumulative participants were identified. Meta-analyses using robust variance estimation showed small stretch-mediated maximal strength increases (d = 0.30 p < 0.001) with stretching duration and intervention time as significant moderators. Including all studies, stretching induced small magnitude, but significant hypertrophy effects (d = 0.20). Longer stretching durations and intervention periods as well as higher training frequencies revealed small (d = 0.26-0.28), but significant effects (p < 0.001-0.005), while lower dosage did not reach the level of significance (p = 0.13-0.39).

CONCLUSIONS

While of minor effectiveness, chronic static stretching represents a possible alternative to resistance training when aiming to improve strength and increase muscle size. As a dose-response relationship may exist, higher stretch durations and frequencies as well as long program durations should be further elaborated.

Comparison of Supervised versus Self-Administered Stretching on Bench Press Maximal Strength and Force Development

PURPOSE

While there is reported superior effectiveness with supervised training, it usually requires specialized exercise facilities and instructors. It is reported in the literature that high-volume stretching improves pectoralis muscles strength under supervised conditions while practical relevance is discussed. Therefore, the study objective was to compare the effects of volume equated, supervised- and self-administered home-based stretching on strength performance.

METHODS

Sixty-three recreational participants were equally assigned to either a supervised static stretching, home-based stretching, or control group. The effects of 15 min pectoralis stretching, 4 days per week for 8 weeks, were assessed on dynamic and isometric bench press strength and force development.

RESULTS

While there was a large magnitude maximal strength increase (p < 0.001-0.023, ƞ2 = 0.118-0.351), force development remained unaffected. Dynamic maximal strength in both groups demonstrated large magnitude increases compared to the control group (p < 0.001-0.001, d = 1.227-0.905). No differences between the intervention group for maximal strength (p = 0.518-0.821, d = 0.101-0.322) could be detected.

CONCLUSIONS

The results could potentially be attributed to stretch-induced tension (mechanical overload) with subsequent anabolic adaptations, and alternative explanatory approaches are discussed. Nevertheless, home-based stretching seems a practical alternative to supervised training with potential meaningful applications in different settings.

Minimalist Training: Is Lower Dosage or Intensity Resistance Training Effective to Improve Physical Fitness? A Narrative Review

BACKGROUND

Findings from original research, systematic reviews, and meta-analyses have demonstrated the effectiveness of resistance training (RT) on markers of performance and health. However, the literature is inconsistent with regards to the dosage effects (frequency, intensity, time, type) of RT to maximize training-induced improvements. This is most likely due to moderating factors such as age, sex, and training status. Moreover, individuals with limited time to exercise or who lack motivation to perform RT are interested in the least amount of RT to improve physical fitness.

OBJECTIVES

The objective of this review was to investigate and identify lower than typically recommended RT dosages (i.e., shorter durations, lower volumes, and intensity activities) that can improve fitness components such as muscle strength and endurance for sedentary individuals or beginners not meeting the minimal recommendation of exercise.

METHODS

Due to the broad research question involving different RT types, cohorts, and outcome measures (i.e., high heterogeneity), a narrative review was selected instead of a systematic meta-analysis approach.

RESULTS

It seems that one weekly RT session is sufficient to induce strength gains in RT beginners with < 3 sets and loads below 50% of one-repetition maximum (1RM). With regards to the number of repetitions, the literature is controversial and some authors report that repetition to failure is key to achieve optimal adaptations, while other authors report similar adaptations with fewer repetitions. Additionally, higher intensity or heavier loads tend to provide superior results. With regards to the RT type, multi-joint exercises induce similar or even larger effects than single-joint exercises.

CONCLUSION

The least amount of RT that can be performed to improve physical fitness for beginners for at least the first 12 weeks is one weekly session at intensities below 50% 1RM, with < 3 sets per multi-joint exercise.

Effects of stretching in a pilates program on musculoskeletal fitness: a randomized clinical trial

BACKGROUND

The scientific literature questions the impact of stretching exercises performed immediately before muscle strengthening exercises on different components of musculoskeletal physical fitness. Pilates is a physical exercise modality that typically uses stretching exercises preceding muscle-strengthening exercises. However, no studies have investigated the effects of stretching in a Pilates program on components of musculoskeletal fitness. The aim of the present study was to verify the effects of stretching in a Pilates exercise program on flexibility, strength, vertical jump height and muscular endurance.

METHODS

Thirty-two sedentary young women were randomized into two groups: traditional Pilates (TP), who performed flexibility and muscle strengthening exercises (n = 16), and nontraditional Pilates (NTP), who only performed muscle-strengthening exercises (n = 16). Sessions took place 3 times a week for 8 weeks. The following tests were performed pre- and postintervention: 10-RM knee extensors, vertical jump, handgrip, 1-min sit-ups, Sorensen and sit-and-reach. The occurrence of adverse events was recorded throughout the intervention and compared between groups using odds ratio (OR). To compare the results of motor tests between groups, ANCOVA or Mann‒Whitney U test was used for parametric and nonparametric data, respectively. The data were analyzed by intention-to-treat.

RESULTS

After intervention, the TP was superior to NTP for the sit-and-reach test, with a large effect size (d = 0.87; p = 0.035), with no differences between groups for the other tests. Intragroup comparisons showed significant differences (p < 0.05) for TP and NTP for improvement in 10-RM knee extensors and vertical jump measurements, while only TP showed significant intragroup improvement (p < 0.05) for the sit-and-reach test. A greater chance of experiencing pain or other discomfort as a result of exercise was shown by NTP (OR = 4.20, CI95% 0.69 to 25.26).

CONCLUSION

Our findings demonstrated that stretching exercises performed at the beginning of sessions in a Pilates program did not impair or enhance the development of strength, vertical jump height and muscular endurance in young women. However, only the Pilates program with stretching improved flexibility and reduced the chances of adverse events such as musculoskeletal pain and other discomfort resulting from the exercise protocol.

CLINICALTRIALS

GOV: NCT05538520, prospectively registered on September 16, 2022.

Effects of a Home-Based Stretching Program on Bench Press Maximum Strength and Shoulder Flexibility

Recent research showed significant stretch-mediated maximum strength increases when performing stretching between 5 to 120 minutes per day with the calf muscle. However, since the practical applicability of these long stretching durations was questioned and studies exploring the transferability to the upper body are scarce, the aim of this study was to investigate the possibility of using a home-based stretching program to induce significant increases in maximum strength and flexibility. Therefore, 31 recreationally active participants (intervention group: 18, control group: 13) stretched the pectoralis major for 15min/day for eight weeks, incorporating three different stretching exercises. The maximum strength was tested isometrically and dynamically in the bench press (one-repetition maximum: 1RM) as well as shoulder range of motion (ROM) performing bilateral shoulder rotation with a scaled bar. Using a two-way analysis of variance (ANOVA) with repeated measures, the results showed high magnitude Time effects (ƞ² = 0.388-0.582, p < 0.001) and Group*Time interaction (ƞ² = 0.281-0.53, p < 0.001-0.002), with increases of 7.4 ± 5.6% in 1RM and of 9.8 ± 5.0% in ROM test in the intervention group. In the isometric testing, there was a high-magnitude Time effect (ƞ² = 0.271, p = 0.003), however, the Group*Time interaction failed to reach significance (p = 0.75). The results are in line with previous results that showed stretch-mediated maximum strength increases in the lower extremity. Future research should address the underlying physiological mechanisms such as muscle hypertrophy, contraction conditions as well as pointing out the relevance of intensity, training frequency and stretching duration.

Physiology of Stretch-Mediated Hypertrophy and Strength Increases: A Narrative Review

Increasing muscle strength and cross-sectional area is of crucial importance to improve or maintain physical function in musculoskeletal rehabilitation and sports performance. Decreases in muscular performance are experienced in phases of reduced physical activity or immobilization. These decrements highlight the need for alternative, easily accessible training regimens for a sedentary population to improve rehabilitation and injury prevention routines. Commonly, muscle hypertrophy and strength increases are associated with resistance training, typically performed in a training facility. Mechanical tension, which is usually induced with resistance machines and devices, is known to be an important factor that stimulates the underlying signaling pathways to enhance protein synthesis. Findings from animal studies suggest an alternative means to induce mechanical tension to enhance protein synthesis, and therefore muscle hypertrophy by inducing high-volume stretching. Thus, this narrative review discusses mechanical tension-induced physiological adaptations and their impact on muscle hypertrophy and strength gains. Furthermore, research addressing stretch-induced hypertrophy is critically analyzed. Derived from animal research, the stretching literature exploring the impact of static stretching on morphological and functional adaptations was reviewed and critically discussed. No studies have investigated the underlying physiological mechanisms in humans yet, and thus the underlying mechanisms remain speculative and must be discussed in the light of animal research. However, studies that reported functional and morphological increases in humans commonly used stretching durations of > 30 min per session of the plantar flexors, indicating the importance of high stretching volume, if the aim is to increase muscle mass and maximum strength. Therefore, the practical applicability seems limited to settings without access to resistance training (e.g., in an immobilized state at the start of rehabilitation), as resistance training seems to be more time efficient. Nevertheless, further research is needed to generate evidence in different human populations (athletes, sedentary individuals, and rehabilitation patients) and to quantify stretching intensity.

Comparison of the effects of long-lasting static stretching and hypertrophy training on maximal strength, muscle thickness and flexibility in the plantar flexors

Maximal strength measured via maximal voluntary contraction is known as a key factor in competitive sports performance as well as injury risk reduction and rehabilitation. Maximal strength and hypertrophy are commonly trained by performing resistance training programs. However, literature shows that long-term, long-lasting static stretching interventions can also produce significant improvements in maximal voluntary contraction. The aim of this study is to compare increases in maximal voluntary contraction, muscle thickness and flexibility after 6 weeks of stretch training and conventional hypertrophy training. Sixty-nine (69) active participants (f = 30, m = 39; age 27.4 ± 4.4 years, height 175.8 ± 2.1 cm, and weight 79.5 ± 5.9 kg) were divided into three groups: IG1 stretched the plantar flexors continuously for one hour per day, IG2 performed hypertrophy training for the plantar flexors (5 × 10-12 reps, three days per week), while CG did not undergo any intervention. Maximal voluntary contraction, muscle thickness, pennation angle and flexibility were the dependent variables. The results of a series of two-way ANOVAs show significant interaction effects (p < 0.05) for maximal voluntary contraction (ƞ2 = 0.143-0.32, p < 0.006), muscle thickness (ƞ2 = 0.11-0.14, p < 0.021), pennation angle (ƞ2 = 0.002-0.08, p = 0.077-0.625) and flexibility (ƞ2 = 0.089-0.21, p < 0.046) for both the stretch and hypertrophy training group without significant differences (p = 0.37-0.99, d = 0.03-0.4) between both intervention groups. Thus, it can be hypothesized that mechanical tension plays a crucial role in improving maximal voluntary contraction and muscle thickness irrespective whether long-lasting stretching or hypertrophy training is used. Results show that for the calf muscle, the use of long-lasting stretching interventions can be deemed an alternative to conventional resistance training if the aim is to increase maximal voluntary contraction, muscle thickness and flexibility. However, the practical application seems to be strongly limited as a weekly stretching duration of up to 7 h a week is opposed by 3 × 15 min of common resistance training.

Muscle Architecture Adaptations to Static Stretching Training: A Systematic Review with Meta-Analysis

BACKGROUND

Long-term stretching of human skeletal muscles increases joint range of motion through altered stretch perception and decreased resistance to stretch. There is also some evidence that stretching induces changes in muscle morphology. However, research is limited and inconclusive.

OBJECTIVE

To examine the effect of static stretching training on muscle architecture (i.e., fascicle length and fascicle angle, muscle thickness and cross-sectional area) in healthy participants.

DESIGN

Systematic review and meta-analysis.

METHODS

PubMed Central, Web of Science, Scopus, and SPORTDiscus were searched. Randomized controlled trials and controlled trials without randomization were included. No restrictions on language or date of publication were applied. Risk of bias was assessed using Cochrane RoB2 and ROBINS-I tools. Subgroup analyses and random-effects meta-regressions were also performed using total stretching volume and intensity as covariates. Quality of evidence was determined by GRADE analysis.

RESULTS

From the 2946 records retrieved, 19 studies were included in the systematic review and meta-analysis (n = 467 participants). Risk of bias was low in 83.9% of all criteria. Confidence in cumulative evidence was high. Stretching training induces trivial increases in fascicle length at rest (SMD = 0.17; 95% CI 0.01-0.33; p = 0.042) and small increases in fascicle length during stretching (SMD = 0.39; 95% CI 0.05 to 0.74; p = 0.026). No increases were observed in fascicle angle or muscle thickness (p = 0.30 and p = 0.18, respectively). Subgroup analyses showed that fascicle length increased when high stretching volumes were used (p < 0.004), while no changes were found for low stretching volumes (p = 0.60; subgroup difference: p = 0.025). High stretching intensities induced fascicle length increases (p < 0.006), while low stretching intensities did not have an effect (p = 0.72; subgroup difference: p = 0.042). Also, high intensity stretching resulted in increased muscle thickness (p = 0.021). Meta-regression analyses showed that longitudinal fascicle growth was positively associated with stretching volume (p < 0.02) and intensity (p < 0.04).

CONCLUSIONS

Static stretching training increases fascicle length at rest and during stretching in healthy participants. High, but not low, stretching volumes and intensities induce longitudinal fascicle growth, while high stretching intensities result in increased muscle thickness.

REGISTRATION

PROSPERO, registration number: CRD42021289884.

Maximal strength measurement: A critical evaluation of common methods-a narrative review

Measuring maximal strength (MSt) is a very common performance diagnoses, especially in elite and competitive sports. The most popular procedure in test batteries is to test the one repetition maximum (1RM). Since testing maximum dynamic strength is very time consuming, it often suggested to use isometric testing conditions instead. This suggestion is based on the assumption that the high Pearson correlation coefficients of r ≥ 0.7 between isometric and dynamic conditions indicate that both tests would provide similar measures of MSt. However, calculating r provides information about the relationship between two parameters, but does not provide any statement about the agreement or concordance of two testing procedures. Hence, to assess replaceability, the concordance correlation coefficient (ρ c) and the Bland-Altman analysis including the mean absolute error (MAE) and the mean absolute percentage error (MAPE) seem to be more appropriate. Therefore, an exemplary model based on r = 0.55 showed ρ c = 0.53, A MAE of 413.58 N and a MAPE = 23.6% with a range of -1,000-800 N within 95% Confidence interval (95%CI), while r = 0.7 and 0.92 showed ρ c = 0.68 with a MAE = 304.51N/MAPE = 17.4% with a range of -750 N-600 N within a 95% CI and ρ c = 0.9 with a MAE = 139.99/MAPE = 7.1% with a range of -200-450 N within a 95% CI, respectively. This model illustrates the limited validity of correlation coefficients to evaluate the replaceability of two testing procedures. Interpretation and classification of ρ c, MAE and MAPE seem to depend on expected changes of the measured parameter. A MAPE of about 17% between two testing procedures can be assumed to be intolerably high.

Sex differences in stretch-induced hypertrophy, maximal strength and flexibility gains

Introduction: If the aim is to increase maximal strength (MSt) and muscle mass, resistance training (RT) is primarily used to achieve these outcomes. However, research indicates that long-duration stretching sessions of up to 2 h per day can also provide sufficient stimuli to induce muscle growth. In RT literature, sex-related differences in adaptations are widely discussed, however, there is a lack of evidence addressing the sex-related effects on MSt and muscle thickness (MTh) of longer duration stretch training. Therefore, this study aimed to investigate the effects of 6 weeks of daily (1 h) unilateral static stretch training of the plantar flexors using a calf-muscle stretching device. Methods: Fifty-five healthy (m = 28, f = 27), active participants joined the study. MSt and range of motion (ROM) were measured with extended and flexed knee joint, and MTh was investigated in the medial and lateral heads of the gastrocnemius. Results: Statistically significant increases in MSt of 6%-15% (p < .001-.049, d = 0.45-1.09), ROM of 6%-21% (p < .001-.037, d = 0.47-1.38) and MTh of 4%-14% (p < .001-.005, d = 0.46-0.72) from pre-to post-test were observed, considering both sexes and both legs. Furthermore, there was a significant higher increase in MSt, MTh and ROM in male participants. In both groups, participants showed more pronounced adaptations in MSt and ROM with an extended knee joint as well as MTh in the medial head of the gastrocnemius (p < .001-.047). Results for relative MSt increases showed a similar result (p < .001-.036, d = 0.48-1.03). Discussion: Results are in accordance with previous studies pointing out significant increases of MSt, MTh and ROM due to long duration static stretch training. Both sexes showed significant increases in listed parameters however, male participants showed superior increases.

Effects of daily static stretch training over 6 weeks on maximal strength, muscle thickness, contraction properties, and flexibility

Purpose

Static stretch training (SST) with long stretching durations seems to be sufficient to increase flexibility, maximum strength (MSt) and muscle thickness (MTh). However, changes in contraction properties and effects on muscle damage remain unclear. Consequently, the objective of the study was to investigate the effects of a 6-week self-performed SST on MSt, MTh, contractile properties, flexibility, and acute response of creatine kinase (CK) 3 days after SST.

Methods

Forty-four participants were divided into a control (CG, n = 22) and an intervention group (IG, n = 22), who performed a daily SST for 5 min for the lower limb muscle group. While isometric MSt was measured in leg press, MTh was examined via sonography and flexibility by functional tests. Muscle stiffness and contraction time were measured by tensiomyography on the rectus femoris. Additionally, capillary blood samples were taken in the pretest and in the first 3 days after starting SST to measure CK.

Results

A significant increase was found for MSt (p < 0.001, η ² = 0.195) and flexibility in all functional tests (p < 0.001, η ² > 0.310). Scheffé post hoc test did not show significant differences between the rectus femoris muscle inter- and intragroup comparisons for MTh nor for muscle stiffness and contraction time (p > 0.05, η ² < 0.100). Moreover, CK was not significantly different between IG and CG with p > 0.05, η ² = 0.032.

Discussion

In conclusion, the increase in MSt cannot be exclusively explained by muscular hypertrophy or the increased CK-related repair mechanism after acute stretching. Rather, neuronal adaptations have to be considered. Furthermore, daily 5-min SST over 6 weeks does not seem sufficient to change muscle stiffness or contraction time. Increases in flexibility tests could be attributed to a stretch-induced change in the muscle-tendon complex.

Using Daily Stretching to Counteract Performance Decreases as a Result of Reduced Physical Activity-A Controlled Trial

There are many reasons for reduced physical activity leading to reduced maximal strength and sport-specific performance, such as jumping performance. These include pandemic lockdowns, serious injury, or prolonged sitting in daily work life. Consequently, such circumstances can contribute to increased morbidity and reduced physical performance. Therefore, a demand for space-saving and home-based training routines to counteract decreases in physical performance is suggested in the literature. This study aimed to investigate the possibility of using daily static stretching using a stretching board to counteract inactivity-related decreases in performance. Thirty-five (35) participants were either allocated to an intervention group (IG), performing a daily ten-minute stretch training combined with reduced physical activity or a reduced physical activity-only group (rPA). The effects on maximal voluntary contraction, range of motion using the knee-to-wall test, countermovement jump height (CMJ_height), squat jump height (SJ_height), drop jump height (DJ_height), contact time (DJ_ct) and the reactive strength index (DJ_RSI) were evaluated using a pre-test-post-test design. The rPA group reported reduced physical activity because of lockdown. Results showed significant decreases in flexibility and jump performance (d = -0.11--0.36, p = 0.004-0.046) within the six weeks intervention period with the rPA group. In contrast, the IG showed significant increases in MVC90 (d = 0.3, p < 0.001) and ROM (d = 0.44, p < 0.001) with significant improvements in SJ_height (d = 0.14, p = 0.002), while no change was measured for CMJ_height and DJ performance. Hence, 10 min of daily stretching seems to be sufficient to counteract inactivity-related performance decreases in young and healthy participants.

Inter-set stretch: A potential time-efficient strategy for enhancing skeletal muscle adaptations

Time is considered a primary barrier to exercise adherence. Therefore, developing time-efficient resistance training (RT) strategies that optimize muscular adaptations is of primary interest to practitioners. A novel approach to the problem involves combining intensive stretch protocols with RT. Conceivably, integrating stretch into the inter-set period may provide an added stimulus for muscle growth without increasing session duration. Mechanistically, stretch can regulate anabolic signaling via both active and passive force sensors. Emerging evidence indicates that both lengthening contractions against a high load as well as passive stretch can acutely activate anabolic intracellular signaling pathways involved in muscle hypertrophy. Although longitudinal research investigating the effects of stretching between RT sets is limited, some evidence suggests it may in fact enhance hypertrophic adaptations. Accordingly, the purpose of this paper is threefold: (1) to review how the active force of a muscle contraction and the force of a passive stretched are sensed; (2) to present evidence for the effectiveness of RT with inter-set stretch for muscle hypertrophy (3) to provide practical recommendations for application of inter-set stretch in program design as well as directions for future research.

Using Long-Duration Static Stretch Training to Counteract Strength and Flexibility Deficits in Moderately Trained Participants

Many sports injuries result in surgery and prolonged periods of immobilization, which may lead to significant atrophy accompanied by loss of maximal strength and range of motion and, therefore, a weak-leg/strong-leg ratio (as an imbalance index ∆ ) lower than 1. Consequently, there are common rehabilitation programs that aim to enhance maximal strength, muscle thickness and flexibility; however, the literature demonstrates existing strength imbalances after weeks of rehabilitation. Since no study has previously been conducted to investigate the effects of long-duration static stretch training to treat muscular imbalances, the present research aims to determine the possibility of counteracting imbalances in maximal strength and range of motion. Thirty-nine athletic participants with significant calf muscle imbalances in maximal strength and range of motion were divided into an intervention group (one-hour daily plantar flexors static stretching of the weaker leg for six weeks) and a control group to evaluate the effects on maximal strength and range of motion with extended and bent knee joint. Results show significant increases in maximal strength (d = 0.84-1.61, p < 0.001-0.005) and range of motion (d = 0.92-1.49, p < 0.001-0.002) following six weeks of static stretching. Group * time effects (p < 0.001-0.004, η² = 0.22-0.55) revealed ∆ changes in the intervention group from 0.87 to 1.03 for maximal strength and from 0.92 to 1.11 in range of motion. The results provide evidence for the use of six weeks of daily, one hour stretching to counteract muscular imbalances. Related research in clinical settings after surgery is suggested.

Influence of One Hour versus Two Hours of Daily Static Stretching for Six Weeks Using a Calf-Muscle-Stretching Orthosis on Maximal Strength

Rebuilding strength capacity is of crucial importance in rehabilitation since significant atrophy due to immobilization after injury and/or surgery can be assumed. To increase maximal strength (MSt), strength training is commonly used. The literature regarding animal studies show that long-lasting static stretching (LStr) interventions can also produce significant improvements in MSt with a dose-response relationship, with stretching times ranging from 30 min to 24 h per day; however, there is limited evidence in human studies. Consequently, the aim of this study is to investigate the dose-response relationship of long-lasting static stretching on MSt. A total of 70 active participants (f = 30, m = 39; age: 27.4 ± 4.4 years; height: 175.8 ± 2.1 cm; and weight: 79.5 ± 5.9 kg) were divided into three groups: IG1 and IG2 both performed unilateral stretching continuously for one (IG1) or two hours (IG2), respectively, per day for six weeks, while the CG served as the non-intervened control. MSt was determined in the plantar flexors in the intervened as well as in the non-intervened control leg to investigate the contralateral force transfer. Two-way ANOVA showed significant interaction effects for MSt in the intervened leg (ƞ² = 0.325, p < 0.001) and in the contralateral control leg (ƞ² = 0.123, p = 0.009), dependent upon stretching time. From this, it can be hypothesized that stretching duration had an influence on MSt increases, but both durations were sufficient to induce significant enhancements in MSt. Thus, possible applications in rehabilitation can be assumed, e.g., if no strength training can be performed, atrophy could instead be reduced by performing long-lasting static stretch training.

Sex differences in stretch-induced hypertrophy, maximal strength and flexibility gains

Introduction: If the aim is to increase maximal strength (MSt) and muscle mass, resistance training (RT) is primarily used to achieve these outcomes. However, research indicates that long-duration stretching sessions of up to 2 h per day can also provide sufficient stimuli to induce muscle growth. In RT literature, sex-related differences in adaptations are widely discussed, however, there is a lack of evidence addressing the sex-related effects on MSt and muscle thickness (MTh) of longer duration stretch training. Therefore, this study aimed to investigate the effects of 6 weeks of daily (1 h) unilateral static stretch training of the plantar flexors using a calf-muscle stretching device. Methods: Fifty-five healthy (m = 28, f = 27), active participants joined the study. MSt and range of motion (ROM) were measured with extended and flexed knee joint, and MTh was investigated in the medial and lateral heads of the gastrocnemius. Results: Statistically significant increases in MSt of 6%-15% (p < .001-.049, d = 0.45-1.09), ROM of 6%-21% (p < .001-.037, d = 0.47-1.38) and MTh of 4%-14% (p < .001-.005, d = 0.46-0.72) from pre-to post-test were observed, considering both sexes and both legs. Furthermore, there was a significant higher increase in MSt, MTh and ROM in male participants. In both groups, participants showed more pronounced adaptations in MSt and ROM with an extended knee joint as well as MTh in the medial head of the gastrocnemius (p < .001-.047). Results for relative MSt increases showed a similar result (p < .001-.036, d = 0.48-1.03). Discussion: Results are in accordance with previous studies pointing out significant increases of MSt, MTh and ROM due to long duration static stretch training. Both sexes showed significant increases in listed parameters however, male participants showed superior increases.