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.

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.

Reliability and validity of an app-assisted tissue compliance meter in measuring tissue stiffness on a phantom model.

Background: Most methods for soft tissue stiffness assessment require high financial resources, significant technical effort, or extensive therapist training. The PACT Sense device was developed to be used in a wide range of applications and user groups. However, to date, there are no data on its validity and reliability. The aim of this study was to investigate the validity and reliability of the PACT device. Methods: A polyurethane phantom tissue model (PTM) mimicking the mechanical properties of the fascia profunda and the erector spinae muscle was used. Stiffness measurements with PACT were conducted by two independent investigators. For construct validity, correlations were calculated between the known stiffness of the PTM and values obtained with PACT. For concurrent validity, we determined the association between the PACT values and additional measurements with the established MyotonPRO device. To estimate interrater and intrarater (two measurements with an interval of 7 days) reliability, we used the intraclass correlation coefficient (ICC). Results: Correlation analysis (PTM/PACT) revealed very high concurrent validity (r = 0.99; p < 0.001), construct validity (PACT/MyotonPRO) was 0.87, p < 0.001. Both, interrater reliability (ICC = 0.85; p = 0.036) and intrarater reliability were good (ICC = 0.89; p < 0.001). Conclusions: The PACT provides valid and reliable stiffness measurements in tissue phantoms. Further studies in humans are needed to confirm its physiometric properties under in vivo conditions.

Knee Biomechanics During Neurocognitively Challenged Drop Landings in Male Elite Soccer Players with Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Reactive decision-making during athletic movement has been demonstrated to evoke unfavorable biomechanics associated with anterior cruciate ligament (ACL) rupture. However, the current evidence is based on assessments of healthy individuals. We aimed to investigate unplanned jump landing kinetics and knee kinematics in ACL-reconstructed (ACLR) and non-injured athletes. METHODS: A total of 30 male professional soccer players (n = 15 ACLR after return to play, n = 15 matched controls) performed six drop landings onto a force plate. As a neurocognitive challenge requiring decision-making, a diode flashing in randomly selected colors indicated the requested landing location. Knee joint kinematics (flexion, valgus and tibial rotation angles) assessed with a 10-camera motion capture system, vertical ground reaction force (vGRF), time to stabilization (TTS) and length of the center of pressure (COP) trace (all analyzed from force plate data) were calculated. Cognitive function was assessed using the CNS Vital Signs battery. RESULTS: The ACLR group produced lower knee flexion angles than the control group (median [interquartile range] 50.00° [6.60] vs. 55.20° [4.45], p = .02). In addition, path length of the center of pressure (379 mm [56.20] vs. 344 mm [37.00], p = .04) and ground reaction force (3.21 N/kg [0.66] vs. 2.87 N/kg [0.48], p = .01) were higher for the ACLR group. No differences were found for knee valgus (p = .96), tibial rotation (p = .83) and TTS (p = .82). ACLR participants scored lower for reaction time (p = .02) and processing speed (p = .01). Unfavorable knee biomechanics were more often related to cognitive function in the ACLR group than in the control group (p < .05). CONCLUSIONS: Impaired reactive decision-making during athletic movement may contribute to the high re-injury risk in individuals with ACLR. Prospective studies confirming potential cause-effect relationships are warranted.

The knowledge of movement experts about stretching effects: Does the science reach practice?

OBJECTIVE: Stretching is performed with numerous purposes in multiple settings such as prevention, rehabilitation, fitness training and sports. Its patterns of use substantially depend on the education and beliefs of health care and exercise professionals as they represent the multiplicators recommending and prescribing interventions to clients, patients and athletes. This study investigated movement experts' knowledge about the scientific evidence on stretching effects. DESIGN: Survey study. PARTICIPANTS: A total of 117 exercise and health professionals (physiotherapists, sports scientists, coaches) attending a training convention in Austria (male: n = 44, female: n = 73, 36±11 years) completed a digital survey. With its 22 items, the questionnaire addressed the movement experts' awareness of the evidence on stretching effects regarding a variety of related topics selected based on the findings of topical systematic reviews. RESULTS: The majority of the individuals (57-88%) assumed positive effects of stretching on recovery, prevention of muscle injury, range of motion, muscular imbalance and artery elasticity. No or adverse effects were mostly claimed on bone injury prevention, maximal/explosive strength, and delayed-onset muscle soreness. In only 10 of 22 items, participants' classifications were in accord with the scientific evidence. CONCLUSIONS: The awareness of research findings on stretching effects among exercise and health professionals is alarmingly low. Future studies may hence be geared to improve implementation and science communication.

Appraising the Methodological Quality of Sports Injury Video Analysis Studies: The QA-SIVAS Scale.

BACKGROUND: Video analysis (VA) is commonly used in the assessment of sports injuries and has received considerable research interest. Until now, no tool has been available for the assessment of study quality. Therefore, the objective of this study was to develop and evaluate a valid instrument that reliably assesses the methodological quality of VA studies. METHODS: The Quality Appraisal for Sports Injury Video Analysis Studies (QA-SIVAS) scale was developed using a modified Delphi approach including expert consensus and pilot testing. Reliability was examined through intraclass correlation coefficient (ICC3,1) and free-marginal kappa statistics by three independent raters. Construct validity was investigated by comparing QA-SIVAS with expert ratings by using Kendall's tau analysis. Rating time was studied by applying the scale to 21 studies and computing the mean time for rating per study article. RESULTS: The QA-SIVAS scale consists of an 18-item checklist addressing the study design, data source, conduct, report, and discussion of VA studies in sports injury research. Inter- and intra-rater reliability were excellent with ICCs > 0.97. Expert ratings revealed a high construct validity (0.71; p < 0.001). Mean rating time was 10 ± 2 min per article. CONCLUSION: QA-SIVAS is a reliable and valid instrument that can be easily applied to sports injury research. Future studies in the field of VA should adhere to standardized methodological criteria and strict quality guidelines.

Pain quality patterns in delayed onset muscle soreness of the lower back suggest sensitization of fascia rather than muscle afferents: a secondary analysis study.

Delayed onset muscle soreness (DOMS) of the lower back is considered a surrogate for acute low back pain (aLBP) in experimental studies. Of note, it is often unquestioningly assumed to be muscle pain. To date, there has not been a study analyzing lumbar DOMS in terms of its pain origin, which was the aim of this study. Sixteen healthy individuals (L-DOMS) were enrolled for the present study and matched to participants from a previous study (n = 16, L-PAIN) who had undergone selective electrical stimulation of the thoracolumbar fascia and the multifidus muscle. DOMS was induced in the lower back of the L-DOMS group using eccentric trunk extensions performed until exhaustion. On subsequent days, pain on palpation (100-mm analogue scale), pressure pain threshold (PPT), and the Pain Sensation Scale (SES) were used to examine the sensory characteristics of DOMS. Pain on palpation showed a significant increase 24 and 48 h after eccentric training, whereas PPT was not affected (p > 0.05). Factor analysis of L-DOMS and L-PAIN sensory descriptors (SES) yielded a stable three-factor solution distinguishing superficial thermal ("heat pain ") from superficial mechanical pain ("sharp pain") and "deep pain." "Heat pain " and "deep pain" in L-DOMS were almost identical to sensory descriptors from electrical stimulation of fascial tissue (L-PAIN, all p > 0.679) but significantly different from muscle pain (all p < 0.029). The differences in sensory description patterns as well as in PPT and self-reported DOMS for palpation pain scores suggest that DOMS has a fascial rather than a muscular origin.

Effects of Maximal Eccentric Trunk Extensor Exercise on Lumbar Extramuscular Connective Tissue: A Matched-Pairs Ultrasound Study.

Recently, it has been shown that the extramuscular connective tissue (ECT) is likely involved in delayed onset muscle soreness (DOMS). Therefore, the aim of the present study was to investigate the effects of maximal trunk extension eccentric exercise (EE) on ECT thickness, self-reported DOMS, ECT stiffness, skin temperature, and possible correlations between these outcomes. Healthy adults (n = 16, 29.34 ± 9.87 years) performed fatiguing EE of the trunk. A group of highly active individuals (TR, n = 8, > 14 h of sport per week) was compared with a group of less active individuals (UTR, n = 8, < 2 h of sport per week). Ultrasound measurements of ECT thickness, stiffness with MyotonPro and IndentoPro, skin temperature with infrared thermography, and pain on palpation (100 mm visual analog scale, VAS) as a surrogate for DOMS were recorded before (t0), immediately (t1), 24 h (t24), and 48 h (t48) after EE. ECT thickness increased after EE from t0 to t24 (5.96 mm to 7.10 mm, p = 0.007) and from t0 to t48 (5.96 mm to 7.21 mm, p < 0.001). VAS also increased from t0 to t24 (15.6 mm to 23.8 mm, p < 0.001) and from t0 to t48 (15.6 mm to 22.8 mm, p < 0.001). Skin temperature increased from t1 to t24 (31.6° Celsius to 32.7° Celsius, p = 0.032) and t1 to t48 (31.6° Celsius to 32.9° Celsius, p = 0.003), while stiffness remained unchanged (p > 0.05). Correlation analysis revealed no linear relationship between the outcomes within the 48-hour measurement period. The results may confirm previous findings of possible ECT involvement in the genesis of DOMS in the extremities also for the paraspinal ECT of trunk extensors. Subsequent work should focus on possible interventions targeting the ECT to prevent or reduce DOMS after strenuous muscle EE.

Thoracolumbar fascia deformation during deadlifting and trunk extension in individuals with and without back pain.

Background: Alterations in posture, lumbopelvic kinematics, and movement patterns are commonly seen in patients with low back pain. Therefore, strengthening the posterior muscle chain has been shown to result in significant improvement in pain and disability status. Recent studies suggest that thoracolumbar fascia (TLF) has a major impact on the maintenance of spinal stability and paraspinal muscle activity, and thus is likely to have an equal impact on deadlift performance. Objective: Aim of the study was to evaluate the role of thoracolumbar fascia deformation (TFLD) during spinal movement in track and field athletes (TF) as well as individuals with and without acute low back pain (aLBP). Methods: A case-control study was performed with n = 16 aLBP patients (cases) and two control groups: untrained healthy individuals (UH, n = 16) and TF (n = 16). Participants performed a trunk extension task (TET) and a deadlift, being assessed for erector spinae muscle thickness (EST) and TLFD using high-resolution ultrasound imaging. Mean deadlift velocity (VEL) and deviation of barbell path (DEV) were measured by means of a three-axis gyroscope. Group differences for TLFD during the TET were examined using ANOVA. Partial Spearman rank correlations were calculated between TLFD and VEL adjusting for baseline covariates, EST, and DEV. TLFD during deadlifting was compared between groups using ANCOVA adjusting for EST, DEV, and VEL. Results: TLFD during the TET differed significantly between groups. TF had the largest TLFD (-37.6%), followed by UH (-26.4%), while aLBP patients had almost no TLFD (-2.7%). There was a strong negative correlation between TLFD and deadlift VEL in all groups (r = -0.65 to -0.89) which was highest for TF (r = -0.89). TLFD during deadlift, corrected for VEL, also differed significantly between groups. TF exhibited the smallest TLFD (-11.9%), followed by aLBP patients (-21.4%), and UH (-31.9%). Conclusion: TFLD maybe a suitable parameter to distinguish LBP patients and healthy individuals during lifting tasks. The cause-effect triangle between spinal movement, TFLD and movement velocity needs to be further clarified. Clinical trial registration: https://drks.de/register/de/trial/DRKS00027074/, German Clinical Trials Register DRKS00027074.

Myofascial force transmission between the calf and the dorsal thigh is dependent on knee angle: an ultrasound study.

A recent in-vivo experiment has shown that force can be transmitted between the gastrocnemius and the hamstring muscles due to a direct tissue continuity. However, it remains unclear if this mechanical interaction is affected by the stiffness of the structural connection. This study therefore aimed to investigate the impact of the knee angle on myofascial force transmission across the dorsal knee. A randomized, cross-over study was performed, including n = 56 healthy participants (25.36 ± 3.9 years, 25 females). On two separate days, they adopted a prone position on an isokinetic dynamometer (knee extended or 60° flexed). In each condition, the device moved the ankle three times from maximal plantarflexion to maximal dorsal extension. Muscle inactivity was ensured using EMG. High-resolution ultrasound videos of the semimembranosus (SM) and the gastrocnemius medialis (GM) soft tissue were recorded. Maximal horizontal tissue displacement, obtained using cross-correlation, was examined as a surrogate of force transmission. SM tissue displacement was higher at extended (4.83 ± 2.04 mm) than at flexed knees (3.81 ± 2.36 mm). Linear regression demonstrated significant associations between (1) SM and GM soft tissue displacement (extended: R2 = 0.18, p = 0.001; flexed: R2 = 0.17, p = 0.002) as well as (2) SM soft tissue displacement and ankle range of motion (extended: R2 = 0.103, p = 0.017; flexed: R2 = 0.095, p = 0.022). Our results further strengthen the evidence that local stretching induces a force transmission to neighboring muscles. Resulting remote exercise effects such as increased range of motion, seem to depend on the stiffness of the continuity.Trial registration: DRKS (Deutsches Register Klinischer Studien), registration number DRKS00024420, first registered 08/02/2021, https://drks.de/search/de/trial/DRKS00024420 .

Progressive daily hopping exercise improves running economy in amateur runners: a randomized and controlled trial.

This study investigated the effects of a daily plyometric hopping intervention on running economy (RE) in amateur runners. In a randomized, controlled trial, thirty-four amateur runners (29 ± 7 years, 27 males) were allocated to a control or a hopping exercise group. During the six-week study, the exercise group performed 5 min of double-legged hopping exercise daily. To progressively increase loading, the number of hopping bouts (10 s each) was steadily increased while break duration between sets was decreased. Pre- and post-intervention, RE, peak oxygen uptake (VO2peak), and respiratory exchange ratio (RER) were measured during 4-min stages at three running speeds (10, 12, and 14 km/h). ANCOVAs with baseline values and potential cofounders as cofactors were performed to identify differences between groups. ANCOVA revealed an effect of hopping on RE at 12 km/h (df = 1; F = 4.35; p < 0.05; η2 = 0.072) and 14 km/h (df = 1; F = 6.72; p < 0.05; η2 = 0.098), but not at 10 km/h (p > 0.05). Exercise did not affect VO2peak (p > 0.05), but increased RER at 12 km/h (df = 1; F = 4.26; p < 0.05; η2 = 0.059) and 14 km/h (df = 1; F = 36.73; p < 0.001; η2 = 0.520). No difference in RER was observed at 10 km/h (p > 0.05). Daily hopping exercise is effective in improving RE at high running speeds in amateurs and thus can be considered a feasible complementary training program.Clinical trial registration German Register of Clinical Trials (DRKS00017373).

Assessing reliability and validity of different stiffness measurement tools on a multi-layered phantom tissue model.

Changes in the mechanical properties (i.e., stiffness) of soft tissues have been linked to musculoskeletal disorders, pain conditions, and cancer biology, leading to a rising demand for diagnostic methods. Despite the general availability of different stiffness measurement tools, it is unclear as to which are best suited for different tissue types and the related measurement depths. The study aimed to compare different stiffness measurement tools' (SMT) reliability on a multi-layered phantom tissue model (MPTM). A polyurethane MPTM simulated the four layers of the thoracolumbar region: cutis (CUT), subcutaneous connective tissue (SCT), fascia profunda (FPR), and erector spinae (ERS), with varying stiffness parameters. Evaluated stiffness measurement tools included Shore Durometer, Semi-Electronic Tissue Compliance Meter (STCM), IndentoPRO, MyotonPRO, and ultrasound imaging. Measurements were made by two independent, blinded examiners. Shore Durometer, STCM, IndentoPRO, and MyotonPRO reliably detected stiffness changes in three of the four MPTM layers, but not in the thin (1 mm thick) layer simulating FPR. With ultrasound imaging, only stiffness changes in layers thicker than 3 mm could be measured reliably. Significant correlations ranging from 0.70 to 0.98 (all p < 0.01) were found. The interrater reliability ranged from good to excellent (ICC(2,2) = 0.75-0.98). The results are encouraging for researchers and clinical practitioners as the investigated stiffness measurement tools are easy-to-use and comparatively affordable.

After Dinner Rest a While, After Supper Walk a Mile? A Systematic Review with Meta-analysis on the Acute Postprandial Glycemic Response to Exercise Before and After Meal Ingestion in Healthy Subjects and Patients with Impaired Glucose Tolerance.

BACKGROUND: The most effective way to cope with high blood sugar spikes is to engage in physical activity in temporal proximity to food intake. However, so far, it is unclear as to whether there is an optimal time for physical activity around food intake. OBJECTIVES: We aimed to identify the impact of pre- and post-meal exercise on postprandial glucose excursions in humans with and without type 2 diabetes mellitus. METHODS: We conducted a systematic review with meta-analysis, PROSPERO registration number: CRD42022324070. We screened MEDLINE/PubMed, Cochrane/CINAHL/EMBASE, and Web of Knowledge until 1 May, 2022. We used the risk of bias rating with the crossover extension of the Cochrane risk of bias assessment tool II. Standardized mean differences (SMDs, Hedges' g) with 95% confidence intervals (CIs) were calculated as pooled effect estimates of a random-effects meta-analysis. Eligibility criteria included three-armed randomized controlled trials comparing the acute effects of pre- and post-meal exercise to a no-exercise control in humans. RESULTS: Eight randomized controlled trials (crossover trials, high risk of bias) with 30 interventions in 116 participants (47 diagnosed with type 2 diabetes, 69 without type 2 diabetes) were eligible. Exercise after meal ingestion (real food or meal replacement drinks) led to a reduction in postprandial glucose excursions compared with exercise before eating (15 effect sizes; SMD = 0.47 [95% CI 0.23, 0.70]) and an inactive control condition (15 effect sizes; SMD = 0.55 [95% CI 0.34, 0.75]. Pre-meal exercise did not lead to significantly lower postprandial glucose compared to an inactive control (15 effect sizes; SMD = - 0.13 [95% CI - 0.42, 0.17]). The time between meal and exercise (estimate = - 0.0151; standard error = 0.00473; Z = - 3.19; p = 0.001; 95% CI - 0.024, - 0.006) had a moderating influence on postprandial glucose excursions. CONCLUSIONS: Exercise, i.e., walking, has a greater acute beneficial impact on postprandial hyperglycemia when undertaken as soon as possible after a meal rather than after a longer interval or before eating. CLINICAL TRIAL REGISTRATION: The review was pre-registered in the PROSPERO database (CRD42022324070). The date of submission was 07.04.2022, with the registration on 08.05.2022.

The Combined Effect of Static Stretching and Foam Rolling With or Without Vibration on the Range of Motion, Muscle Performance, and Tissue Hardness of the Knee Extensor.

ABSTRACT: Nakamura, M, Konrad, A, Kasahara, K, Yoshida, R, Murakami, Y, Sato, S, Aizawa, K, Koizumi, R, and Wilke, J. The combined effect of static stretching and foam rolling with or without vibration on the range of motion, muscle performance, and tissue hardness of the knee extensor. J Strength Cond Res 37(2): 322-327, 2023-Although the combination of static stretching (SS) and foam rolling (FR) is frequently used for warm-up in sports, the effect of the intervention order is unclear. This study compared mechanical tissue properties, pain sensitivity, and motor function after SS and FR (with and without vibration) performed in different orders. Our randomized, controlled, crossover experiment included 15 healthy male subjects (22.5 ± 3.3 years) who visited the laboratory 5 times (inactive control condition, FR + SS, FR vibration + SS, SS + FR, and SS + FR vibration ) with an interval of ≥48 hours. In each session, subjects completed three 60-second bouts of FR and SS, targeting the anterior thigh. Pressure pain threshold, tissue hardness, knee flexion range of motion (ROM), maximal voluntary isometric (MVC-ISO), and concentric (MVC-CON) torque, as well as countermovement jump height, were determined before and after the intervention. All interventions significantly ( p < 0.01) increased knee flexion ROM ( d = 0.78, d = 0.87, d = 1.39, and d = 0.87, respectively) while decreasing tissue hardness ( d = -1.25, d = -1.09, d = -1.18, and d = -1.24, respectively). However, MVC-ISO torque was significantly reduced only after FR + SS ( p = 0.05, d = -0.59). Our results suggest that SS should be followed by FR when aiming to increase ROM and reduce tissue hardness without concomitant stretch-induced force deficits (MVC-ISO, MVC-CON, and countermovement jump height). Additionally, adding vibration to FR does not seem to affect the magnitude of changes observed in the examined outcomes.

Myofascial force transmission between the ankle and the dorsal knee: A study protocol.

BACKGROUND: Connective tissue links the skeletal muscles, creating a body-wide network of continuity. A recent in-vivo experiment demonstrated that passive elongation of the calf caused a caudal displacement of the semimembranosus muscle, indicating force transmission across the dorsal knee joint. However, it remains unclear as to whether this observation is dependent on the joint angle. If force would not be transmitted at flexed knees, this would reduce the number of postures and movements where force transmission is of relevance. Our trial, therefore, aims to investigate the influence of passive calf stretching with the knee in extended and flexed position on dorsal thigh soft tissue displacement. METHODS: Participants are positioned prone on an isokinetic dynamometer. The device performs three repetitions of moving the ankle passively (5°/s) between plantar flexion and maximum dorsiflexion. With a washout-period of 24 hours, this procedure is performed twice in randomised order, once with the knee extended (0°) and once with the knee flexed (60°). Two high-resolution ultrasound devices will be used to visualize the soft tissue of the calf and dorsal thigh during the manoeuvre. Maximal horizontal displacement of the soft tissue [mm] during ankle movement will be quantified as a surrogate of force transmission, using a frame-by-frame cross-correlation analysis of the obtained US videos. DISCUSSION: Understanding myofascial force transmission under in-vivo conditions is a pre-requisite for the development of exercise interventions specifically targeting the fascial connective tissue. Our study may thus provide health and fitness professional with the anatomical and functional basis for program design. TRIAL REGISTRATION: The study is registered at the German Clinical Trials Register (TRN: DRKS00024420), registered 8 Februar 2021, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00024420.

Physical Activity During Lockdowns Associated with the COVID-19 Pandemic: A Systematic Review and Multilevel Meta-analysis of 173 Studies with 320,636 Participants.

BACKGROUND: Many countries have restricted public life in order to contain the spread of the novel coronavirus (SARS-CoV2). As a side effect of related measures, physical activity (PA) levels may have decreased. OBJECTIVE: We aimed (1) to quantify changes in PA and (2) to identify variables potentially predicting PA reductions. METHODS: A systematic review with random-effects multilevel meta-analysis was performed, pooling the standardized mean differences in PA measures before and during public life restrictions. RESULTS: A total of 173 trials with moderate methodological quality (modified Downs and Black checklist) were identified. Compared to pre-pandemic, total PA (SMD - 0.65, 95% CI - 1.10 to - 0.21) and walking (SMD - 0.52, 95% CI - 0.29 to - 0.76) decreased while sedentary behavior increased (SMD 0.91, 95% CI: 0.17 to 1.65). Reductions in PA affected all intensities (light: SMD - 0.35, 95% CI - 0.09 to - 0.61, p = .013; moderate: SMD - 0.33, 95% CI - 0.02 to - 0.6; vigorous: SMD - 0.33, - 0.08 to - 0.58, 95% CI - 0.08 to - 0.58) to a similar degree. Moderator analyses revealed no influence of variables such as sex, age, body mass index, or health status. However, the only continent without a PA reduction was Australia and cross-sectional trials yielded higher effect sizes (p < .05). CONCLUSION: Public life restrictions associated with the COVID-19 pandemic resulted in moderate reductions in PA levels and large increases in sedentary behavior. Health professionals and policy makers should therefore join forces to develop strategies counteracting the adverse effects of inactivity.

Reliability of a New Indentometer Device for Measuring Myofascial Tissue Stiffness.

Changes in tissue stiffness are associated with pathological conditions such as myofascial pain and increased risk of muscle injury. Furthermore, they have been shown to modify performance indicators such as running economy or jump height. Indentometry is an affordable way to assess tissue stiffness. However, to date, there is a paucity of studies examining the measurement properties of available devices. With this trial, we aimed to evaluate the reliability of the "IndentoPro". Two investigators repeatedly measured the stiffness of the lateral head of the gastrocnemius muscle in healthy participants (N = 35), using 5 and 10 mm indentation depths. Intraclass Correlation Coefficients (ICC) revealed moderate inter-rater reliability (5 mm: ICC3,1 0.74, 95%CI = 0.54 to 0.86, p < 0.001; 10 mm: ICC3,1 0.59, 95%CI = 0.27 to 0.78, p < 0.001) and good intra-rater reliability (5 mm: ICC3,1 0.84, 95%CI = 0.71 to 0.92, p < 0.001; 10 mm: ICC3,1 0.83, 95%CI = 0.69 to 0.91, p < 0.001). No correlations between age, height, weight, BMI, skinfold thickness and myofascial tissue stiffness were observed (p > 0.5). In conclusion, the IndentoPro is reliable in assessing calf tissue stiffness, but the predictors of stiffness remain unclear.

Association between physical activity and musculoskeletal pain: an analysis of international data from the ASAP survey.

OBJECTIVE: To explore the association of physical activity (PA) with musculoskeletal pain (MSK pain). DESIGN: Cross-sectional study SETTING: 14 countries (Argentina, Australia, Austria, Brazil, Chile, France, Germany, Italy, the Netherlands, Singapore, South Africa, Spain, Switzerland and the USA). PARTICIPANTS: Individuals aged 18 or older. PRIMARY AND SECONDARY OUTCOME MEASURES: PA volumes were assessed with an adapted version of the Nordic Physical Activity Questionnaire-short. Prevalence of MSK pain was captured by means of a 20-item checklist of body locations. Based on the WHO recommendation on PA, participants were classified as non-compliers (0-150 min/week), compliers (150-300 min/week), double compliers (300-450 min/week), triple compliers (450-600 min/week), quadruple compliers (600-750 min/week), quintuple compliers (750-900 min/week) and top compliers (more than 900 min/week). Multivariate logistic regression was used to obtain adjusted ORs of the association between PA and MSK pain for each body location, correcting for age, sex, employment status and depression risk. RESULTS: A total of 13 741 participants completed the survey. Compared with non-compliers, compliers had smaller odds of MSK pain in one location (thoracic pain, OR 0.77, 95% CI 0.64 to 0.93). Double compliance was associated with reduced pain occurrence in six locations (elbow, OR 0.70, 95% CI 0.50 to 0.98; forearm, OR 0.63, 95% CI 0.40 to 0.99; wrist, OR 0.74, 95% CI 0.57 to 0.98; hand, OR 0.57, 95% CI 0.40 to 0.79; fingers, OR 0.72, 95% CI 0.52 to 0.99; abdomen, OR 0.61, 95% CI 0.41 to 0.91). Triple to top compliance was also linked with lower odds of MSK pain (five locations in triple compliance, three in quadruple compliance, two in quintuple compliance, three in top compliance), but, at the same time, presented increased odds of MSK pain in some of the other locations. CONCLUSION: A dose of 300-450 min WHO-equivalent PA/week was associated with lower odds of MSK pain in six body locations. On the other hand, excessive doses of PA were associated with higher odds of pain in certain body locations.

Effects of Maximal Eccentric Exercise on Deep Fascia Stiffness of the Knee Flexors: A Pilot Study using Shear-Wave Elastography.

The deep fascia is intimately linked to skeletal muscle and may be involved in delayed onset muscle soreness (DOMS). The present study therefore explored the effect of eccentric exercise on fascia stiffness and its relation with DOMS. Healthy active male adults (n = 19, 27 ± 4 years) performed 6 x 10 maximal eccentric knee flexions using an isokinetic dynamometer. Before (baseline) as well as immediately (T0), 1 hour (T1), and each day up to 72 hours (T24 to T72) afterwards, shear wave elastography was used to measure the mechanical stiffness of the biceps femoris muscle and the overlying fascia. As a surrogate of DOMS, pain upon palpation was captured by means of a 100mm visual analogue scale. While muscle stiffness remained unchanged (p > 0.05), deep fascia stiffness increased from baseline to T24 (median: 18 kPa to 21.12 kPa, p = 0.017) and T72 (median: 18 kPa to 21.3 kPa, p = 0.001) post-exercise. Linear regression showed an association of stiffness changes at T24 and pressure pain at T72 (r2 = 0.22, p < 0.05). Maximal eccentric exercise leads to a stiffening of the fascia, which, in turn, is related to the magnitude of future DOMS. Upcoming research should therefore gauge the effectiveness of interventions modifying the mechanical properties of the connective tissue in order to accelerate recovery.

Cortical Motor Planning and Biomechanical Stability During Unplanned Jump Landings in Men With Anterior Cruciate Ligament Reconstruction.

CONTEXT: Athletes with anterior cruciate ligament (ACL) reconstruction (ACLR) exhibit increased cortical motor planning during simple sensorimotor tasks compared with healthy athletes serving as control groups. This may interfere with proper decision making during time-constrained movements, elevating the reinjury risk. OBJECTIVE: To compare cortical motor planning and biomechanical stability during jump landings between participants with ACLR and healthy individuals. DESIGN: Cross-sectional study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Ten men with ACLR (age = 28 ± 4 years, time after surgery = 63 ± 35 months) and 17 healthy men (age = 28 ± 4 years) completed 43 ± 4 preplanned (landing leg shown before takeoff) and 51 ± 5 unplanned (visual cue during flight) countermovement jumps with single-legged landings. MAIN OUTCOME MEASURE(S): Movement-related cortical potentials (MRCPs) and frontal θ frequency power before the jump were analyzed using electroencephalography. Movement-related cortical potentials were subdivided into 3 successive 0.5-second time periods (readiness potential [RP]-1, RP-2, and negative slope [NS]) relative to movement onset, with higher values indicating more motor planning. Theta power was calculated for the last 0.5 second before movement onset, with higher values demonstrating more focused attention. Biomechanical landing stability was measured via peak vertical ground reaction force, time to stabilization, and center of pressure. RESULTS: Both the ACLR and healthy groups evoked MRCPs at all 3 time periods. During the unplanned task analyzed using P values and Cohen d, the ACLR group exhibited slightly higher but not different MRCPs, achieving medium effect sizes (RP-1: P = .25, d = 0.44; RP-2: P = .20, d = 0.53; NS: P = .28, d = 0.47). The ACLR group also showed slightly higher θ power values that were not different during the preplanned (P = .18, d = 0.29) or unplanned (P = .42, d = 0.07) condition, achieving small effect sizes. The groups did not differ in their biomechanical outcomes (P values > .05). No condition × group interactions occurred (P values > .05). CONCLUSIONS: Our jump-landing task evoked MRCPs. Although not different between groups, the observed effect sizes provided the first indication that men with ACLR might have consistently relied on more cortical motor planning associated with unplanned jump landings. Confirmatory studies with larger sample sizes are warranted.