Effects of high loading by eccentric triceps surae training on Achilles tendon properties in humans.

PURPOSE: To document the magnitude and time course of human Achilles tendon adaptations (i.e. changes in tendon morphological and mechanical properties) during a 12-week high-load plantar flexion training program. METHODS: Ultrasound was used to determine Achilles tendon cross-sectional area (CSA), length and elongation as a function of plantar flexion torque during voluntary plantar flexion. Tendon force-elongation and stress-strain relationships were determined before the start of training (pre-training) and after 4 (post-4), 8 (post-8) and 12 (post-12) training weeks. RESULTS: At the end of the training program, maximum isometric force had increased by 49% and tendon CSA by 17%, but tendon length, maximal tendon elongation and maximal strain were unchanged. Hence, tendon stiffness had increased by 82%, and so had Young's modulus, by 86%. Significant changes were first detected at post-4 in stiffness (51% increase) and Young's modulus (87% increase), and at post-8 in CSA (15% increase). CONCLUSIONS: Achilles tendon material properties already improved after 4 weeks of high-load training: stiffness increased while CSA remained unchanged. Tendon hypertrophy (increased CSA) was observed after 8 training weeks and contributed to a further increase in Achilles tendon stiffness, but tendon stiffness increases were mostly caused by adaptations in tissue properties.

Biomechanical, physiological and anthropometrical predictors of performance in recreational runners.

Background: The maximal running speed (VMAX) determined on a graded treadmill test is well-recognized as a running performance predictor. However, few studies have assessed the variables that predict VMAX in recreationally active runners. Methods: We used a mathematical procedure combining Fick's law and metabolic cost analysis to verify the relation between (1) VMAX versus anthropometric and physiological determinants of running performance and, (2) theoretical metabolic cost versus running biomechanical parameters. Linear multiple regression and bivariate correlation were applied. We aimed to verify the biomechanical, physiological, and anthropometrical determinants of VMAX in recreationally active runners. Fifteen recreationally active runners participated in this observational study. A Conconi and a stead-steady running test were applied using a heart rate monitor and a simple video camera to register the physiological and mechanical variables, respectively. Results: Statistical analysis revealed that the speed at the second ventilatory threshold, theoretical metabolic cost, and fat-mass percentage confidently estimated the individual running performance as follows: VMAX = 58.632 + (-0.183 * fat percentage) + (-0.507 * heart rate percentage at second ventilatory threshold) + (7.959 * theoretical metabolic cost) (R2 = 0.62, p = 0.011, RMSE = 1.50 km.h-1). Likewise, the theoretical metabolic cost was significantly explained (R2 = 0.91, p = 0.004, RMSE = 0.013 a.u.) by the running spatiotemporal and elastic-related parameters (contact and aerial times, stride length and frequency, and vertical oscillation) as follows: theoretical metabolic cost = 10.421 + (4.282 * contact time) + (-3.795 * aerial time) + (-2.422 * stride length) + (-1.711 * stride frequency) + (0.107 * vertical oscillation). Conclusion: Critical determinants of elastic mechanism, such as maximal vertical force and vertical and leg stiffness were unrelated to the metabolic economy. VMAX, a valuable marker of running performance, and its physiological and biomechanical determinants can be effectively evaluated using a heart rate monitor, treadmill, and a digital camera, which can be used in the design of training programs to recreationally active runners.

Juçara (Euterpe edulis Martius) improves time-to-exhaustion cycling performance and increased reduced glutathione: a randomized, placebo-controlled, crossover, and triple-blind study.

To examine the effects of 7-days juçara powder (JP) intake on oxidative stress biomarkers and endurance and sprint cycling performances. In a randomized, placebo-controlled, crossover, and triple-blind study, 20 male trained cyclists were assigned to intake 10 g of JP (240 mg anthocyanins) or placebo (PLA) for 7 days and performed a cycling time-to-exhaustion (TTE). A 5 s cycling sprint was performed before and after the cycling TTE. Blood oxidative stress biomarkers and lactate concentration where evaluated 1 h before (T-1), immediately after (T0), and 1 h after (T1) the cycling TTE. The mean duration time for the cycling TTE was 8.4 ± 6.0% (63 ± 17 s) longer in the JP condition (JP: 751 ± 283 s) compared to PLA (688 ± 266 s) (P < 0.019). Two-way repeated measures Analysis of variance showed an increase in the JP condition for reduced glutathione (GSH) (P = 0.049) at T0 (P = 0.039) and T1 (P = 0.029) compared to PLA with a moderate effect size at T0 (d = 0.61) and T1 (d = 0.57). Blood lactate levels increased over time in both conditions (P ≤ 0.001). No differences were observed for the post-TTE sprint fatigue index, total phenols, protein carbonyls, and glutathione peroxidase activity. Seven-day intake of JP improved cycling endurance performance and increased GSH levels but had no effect on lactate and cycling sprint-induced fatigue.

Cut-off score of the modified Ashworth scale corresponding to walking ability and functional mobility in individuals with chronic stroke.

PURPOSE: To determine the optimal cut-off score for the Modified Ashworth Scale (MAS) corresponding to unfavorable outcomes for mobility and walking ability. METHODS: The level of plantar flexor muscle spasticity and the 10-meter walking test (10mWT), timed up and go (TUG), and five time sit-to-stand (FTSTS) outcomes were evaluated in individuals after stroke. The correlation between MAS and the tests was investigated, and the optimal cut-off score, sensitivity, and specificity were evaluated through receiver operating characteristic (ROC) curve. RESULTS: Twenty-one participants with chronic stroke and plantar flexors spasticity (11 men; 10 women; mean age = 57.6 ± 12.5 years) participated in the study. Significant correlations between MAS and 10mWT (r= -0.45; p < 0.05), MAS and TUG (r = 0.48; p < 0.05) were found. The optimal cut-off scores were MAS > 2 for unfavorable 10mWT (sensitivity = 100%; specificity = 54.5%; ROC = 0.782) and MAS ≤ 2 for favorable TUG outcomes (sensitivity = 55.5%; specificity = 91.6%; ROC = 0.782). CONCLUSIONS: This study revealed that moderate level of plantar flexors spasticity results in the highest sensitivity to predict poor gait speed performance and the highest specificity to predict good mobility performance in individuals after stroke. These findings will help clinicians in their evidence-based decision making on the role of spasticity for mobility and walking ability.Implications for rehabilitationModerate level of spasticity (MAS <2) is the optimal cut-off score for 10mWT and TUG tests.Reducing the level of spasticity of plantar flexors below this cut-off point might be associated with an increased walking speed in this population.MAS <2 might not limit walking and mobility in individuals after stroke.Calf muscles spasticity might not compromise five time sit-to-stand (FTSTS) performances and might be related to a smaller influence on the sit to stand task.

Quadriceps Muscle Morphology Is an Important Determinant of Maximal Isometric and Crank Torques of Cyclists.

The aim of this study was to determine if quadriceps morphology [muscle volume (MV); cross-sectional area (CSA)], vastus lateralis (VL) muscle architecture, and muscle quality [echo intensity (ECHO)] can explain differences in knee extensor maximal voluntary isometric contraction (MVIC), crank torque (CT) and time-to-exhaustion (TTE) in trained cyclists. Twenty male competitive cyclists performed a maximal incremental ramp to determine their maximal power output (POMAX). Muscle morphology (MV; CSA), muscle architecture of VL and muscle quality (ECHO) of both quadriceps muscles were assessed. Subsequently, cyclists performed three MVICs of both knee extensor muscles and finally performed a TTE test at POMAX with CT measurement during TTE. Stepwise multiple regression results revealed right quadriceps MV determined right MVIC (31%) and CT (33%). Left MV determined CT (24%); and left VL fascicle length (VL-FL) determined MVIC (64%). However, quadriceps morphological variables do not explain differences in TTE. No significant differences were observed between left and right quadriceps muscle morphology (p > 0.05). The findings emphasize that quadriceps MV is an important determinant of knee extensor MVIC and CT but does not explain differences in TTE at POMAX. Furthermore, quadriceps morphological variables were similar between the left and right quadriceps in competitive cyclists.

Effects of Photobiomodulation Therapy on Performance in Successive Time-to-Exhaustion Cycling Tests: A Randomized Double-Blinded Placebo-Controlled Trial.

The goal of this study was to investigate the effects of photobiomodulation therapy (PBMT) on performance, oxygen uptake (VO2) kinetics, and lower limb muscle oxygenation during three successive time-to-exhaustions (TTEs) in cyclists. This was a double-blind, randomized, crossover, placebo-controlled trial study. Sixteen cyclists (~23 years) with a cycling training volume of ~460 km/week volunteered for this study. In the first session, cyclists performed a maximal incremental test to determine maximal oxygen uptake and maximal power output (POMAX). In the following sessions, cyclists performed three consecutive TTEs at POMAX. Before each test, PBMT (135 J/thigh) or a placebo (PLA) was applied to both thighs. VO2 amplitude, O2 deficit, time delay, oxyhemoglobin (O2Hb), deoxyhemoglobin (HHb), and total hemoglobin (tHb) were measured during tests on the right vastus lateralis. The PBMT applied before three successive TTE increased performance of the first and second TTE (~10-12%) tests, speed of VO2 and HHb kinetics during the first test, and increased peripheral muscle oxygenation (increase in HHb and tHb) in the first and second exhaustion tests. However, the PBMT effects were attenuated in the third TTE, as performance and all the other outcomes were similar to the ones from the PLA intervention. In summary, PBMT application increased the first and second successive TTEs, speed of VO2, and muscle oxygenation.

Influence of subcutaneous adipose thickness and dominance on reliability of quadriceps muscle quality in healthy young individuals.

BACKGROUND: Echo intensity (EI) can be useful to check muscle quality and has been widely used to identify tissue damage. In the clinical and sports context, it has been used to identify metabolic disorders and training muscle performance. OBJECTIVE: To determine whether subcutaneous adipose thickness (SAT) influences the inter-session EI reliability of the quadriceps femoris and whether EI is influenced by dominance in young healthy subjects. DESIGN: All procedures were approved by the local Institutional Research Ethics Committee (project number 2.620.204). This is a cross-sectional study where 19 healthy young individuals volunteered. METHOD: The individuals were assessed at two time points by an experienced examiner. Imaging of the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) muscles were performed bilaterally by ultrasonography. EI and SAT analysis was performed using ImageJ®software. RESULTS/FINDINGS: Inter-session intraclass correlation coefficient (ICC) for EImeasured showed moderate reliability for RF (R = 0.578; P = 0.038) and VL (R = 0.735; P = 0.004) and low for VM (R = 0.402; P = 0.142). When corrected by SAT, inter-session (EIcorrected), ICC values showed good reliability for RF (R = 0.826; P < 0.001) and VM (R = 0.765; P = 0.002) and excellent for VL (R = 0.909; P < 0.001). Considering inter-side reliability, Student's paired t-test demonstrated no difference for EImeasured (P > 0.283), EIcorrected (P > 0.127), and SAT (P > 0.356). CONCLUSIONS: SAT influenced the inter-session reliability values of EI in all muscles evaluated. Although they showed similarity, EI values were not influenced by dominance in young healthy subjects.

Facial mask acute effects on affective/psychological and exercise performance responses during exercise: A meta-analytical review.

Background: Face masks are widely used during the COVID-19 pandemic as one of the protective measures against the viral infection risk. Some evidence suggests that face mask prolonged use can be uncomfortable, and discomfort can be exacerbated during exercise. However, the acute responses of mask-wearing during exercise on affective/psychological and exercise performance responses is still a topic of debate. Purpose: To perform a systematic review with meta-analysis of the acute effects of mask-wearing during exercise on affective/psychological and exercise performance responses in healthy adults of different/diverse training status. Methods: This review (CRD42021249569) was performed according to Cochrane's recommendations, with searches performed in electronic (PubMed, Web of Science, Embase, SportDiscus, and PsychInfo) and pre-print databases (MedRxiv, SportRxiv, PsyArXiv, and Preprint.Org). Syntheses of included studies' data were performed, and the RoB-2 tool was used to assess the studies' methodological quality. Assessed outcomes were affective/psychological (discomfort, stress and affective responses, fatigue, anxiety, dyspnea, and perceived exertion) and exercise performance time-to-exhaustion (TTE), maximal power output (POMAX), and muscle force production] parameters. Available data were pooled through meta-analyses. Results: Initially 4,587 studies were identified, 36 clinical trials (all crossover designs) were included. A total of 749 (39% women) healthy adults were evaluated across all studies. The face mask types found were clothing (CM), surgical (SM), FFP2/N95, and exhalation valved FFP2/N95, while the most common exercises were treadmill and cycle ergometer incremental tests, beyond outdoor running, resistance exercises and functional tests. Mask-wearing during exercise lead to increased overall discomfort (SMD: 0.87; 95% CI 0.25-1.5; p = 0.01; I2 = 0%), dyspnea (SMD: 0.40; 95% CI 0.09-0.71; p = 0.01; I2 = 68%), and perceived exertion (SMD: 0.38; 95% CI 0.18-0.58; p < 0.001; I2 = 46%); decreases on the TTE (SMD: -0.29; 95% CI -0.10 to -0.48; p < 0.001; I2 = 0%); without effects on POMAX and walking/running distance traveled (p > 0.05). Conclusion: Face mask wearing during exercise increases discomfort (large effect), dyspnea (moderate effect), and perceived exertion (small effect), and reduces the TTE (small effect), without effects on cycle ergometer POMAX and distance traveled in walking and running functional tests. However, some aspects may be dependent on the face mask type, such as dyspnea and perceived exertion. Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021249569], identifier [CRD42021249569].

Photobiomodulation Therapy Partially Restores Cartilage Integrity and Reduces Chronic Pain Behavior in a Rat Model of Osteoarthritis: Involvement of Spinal Glial Modulation.

OBJECTIVE: Chronic pain associated with osteoarthritis (OA) often leads to reduced function and engagement in activities of daily living. Current pharmacological treatments remain relatively ineffective. This study investigated the efficacy of photobiomodulation therapy (PBMT) on cartilage integrity and central pain biomarkers in adult male Wistar rats. DESIGN: We evaluated the cartilage degradation and spinal cord sensitization using the monoiodoacetate (MIA) model of OA following 2 weeks of delayed PBMT treatment (i.e., 15 days post-MIA). Multiple behavioral tests and knee joint histology were used to assess deficits related to OA. Immunohistochemistry was performed to assess chronic pain sensitization in spinal cord dorsal horn regions. Furthermore, we analyzed the principal components related to pain-like behavior and cartilage integrity. RESULTS: MIA induced chronic pain-like behavior with respective cartilage degradation. PBMT had no effects on overall locomotor activity, but positive effects on weight support (P = 0.001; effect size [ES] = 1.01) and mechanical allodynia (P = 0.032; ES = 0.51). Greater optical densitometry of PBMT-treated cartilage was evident in superficial layers (P = 0.020; ES = 1.34), likely reflecting the increase of proteoglycan and chondrocyte contents. In addition, PBMT effects were associated to decreased contribution of spinal glial cells to pain-like behavior (P = 0.001; ES = 0.38). CONCLUSION: PBMT during the chronic phase of MIA-induced OA promoted cartilage recovery and reduced the progression or maintenance of spinal cord sensitization. Our data suggest a potential role of PBMT in reducing cartilage degradation and long-term central sensitization associated with chronic OA.

Triceps Surae Muscle-Tendon Properties as Determinants of the Metabolic Cost in Trained Long-Distance Runners.

Purpose: This study aimed to determine whether triceps surae's muscle architecture and Achilles tendon parameters are related to running metabolic cost (C) in trained long-distance runners. Methods: Seventeen trained male recreational long-distance runners (mean age = 34 years) participated in this study. C was measured during submaximal steady-state running (5 min) at 12 and 16 km h-1 on a treadmill. Ultrasound was used to determine the gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and soleus (SO) muscle architecture, including fascicle length (FL) and pennation angle (PA), and the Achilles tendon cross-sectional area (CSA), resting length and elongation as a function of plantar flexion torque during maximal voluntary plantar flexion. Achilles tendon mechanical (force, elongation, and stiffness) and material (stress, strain, and Young's modulus) properties were determined. Stepwise multiple linear regressions were used to determine the relationship between independent variables (tendon resting length, CSA, force, elongation, stiffness, stress, strain, Young's modulus, and FL and PA of triceps surae muscles) and C (J kg-1m-1) at 12 and 16 km h-1. Results: SO PA and Achilles tendon CSA were negatively associated with C (r 2 = 0.69; p < 0.001) at 12 km h-1, whereas SO PA was negatively and Achilles tendon stress was positively associated with C (r 2 = 0.63; p = 0.001) at 16 km h-1, respectively. Our results presented a small power, and the multiple linear regression's cause-effect relation was limited due to the low sample size. Conclusion: For a given muscle length, greater SO PA, probably related to short muscle fibers and to a large physiological cross-sectional area, may be beneficial to C. Larger Achilles tendon CSA may determine a better force distribution per tendon area, thereby reducing tendon stress and C at submaximal speeds (12 and 16 km h-1). Furthermore, Achilles tendon morphological and mechanical properties (CSA, stress, and Young's modulus) and triceps surae muscle architecture (GM PA, GM FL, SO PA, and SO FL) presented large correlations with C.

Corrigendum: Triceps Surae Muscle Architecture Adaptations to Eccentric Training.

[This corrects the article DOI: 10.3389/fphys.2019.01456.].

Effect of corporal suspension and pendulum exercises on neuromuscular properties and functionality in patients with medullar thoracic injury.

BACKGROUND: Traumatic spinal cord injury (TSCI) is one of the most devastating injuries that has a physical impact on patients. The CHORDATA® method involves suspension and pendulous exercises and has been clinically used to treat patients with TSCI. Although empirically used to treat neurological patients, there is no scientific evidence of the efficacy of this method. PURPOSE: To evaluate the chronic effects of CHORDATA® method on torque, muscle activation, muscle thickness, and functionality in patients with traumatic spinal cord injury. METHODS: Twenty-six male patients with medullar thoracic injury were randomly categorised into two groups: intervention group (n = 14) and control group (n = 12). Rehabilitation program comprised of 16 sessions of body suspension and pendulum exercises (twice/week). The maximal voluntary isometric trunk flexion and extension torques, muscle activation and thickness (external and internal oblique, rectus and transversus abdominis, longissimus, and multifidus muscles), and functionality (adapted reach test) were evaluated before and after of rehabilitation program. FINDINGS: A significant increase was observed in maximal voluntary isometric torque (flexion, 58%; extension, 76%), muscle activation of the rectus abdominis muscle, and muscle thickness of all intervention group muscles, without changes in the control group. Compared to the pre-intervention period, the intervention group also showed improvement in functionality at post-intervention, but no such differences were noted in the control group. INTERPRETATION: The corporal suspension and pendulum exercises training improved rectus abdominis muscle activation, trunk muscles structure and strength, and reaching capacity in medullar thoracic injury patients.

Triceps Surae Muscle Architecture Adaptations to Eccentric Training.

BACKGROUND: Eccentric exercises have been used in physical training, injury prevention, and rehabilitation programs. The systematic use of eccentric training promotes specific morphological adaptations on skeletal muscles. However, synergistic muscles, such as the triceps surae components, might display different structural adaptations due to differences in architecture, function, and load sharing. Therefore, the purpose of this study was to determine the effects of an eccentric training program on the triceps surae (GM, gastrocnemius medialis; GL, gastrocnemius lateralis; and SO, soleus) muscle architecture. METHODS: Twenty healthy male subjects (26 ± 4 years) underwent a 4-week control period followed by a 12-week eccentric training program. Muscle architecture [fascicle length (FL), pennation angle (PA), and muscle thickness (MT)] of GM, GL, and SO was evaluated every 4 weeks by ultrasonography. RESULTS: Fascicle lengths (GM: 13.2%; GL: 8.8%; SO: 21%) and ML increased (GM: 14.9%; GL: 15.3%; SO: 19.1%) from pre- to post-training, whereas PAs remained similar. GM and SO FL and MT increased up to the 8th training week, whereas GL, FL increased up to the 4th week. SO displayed the highest, and GL the smallest gains in FL post-training. CONCLUSION: All three synergistic plantar flexor muscles increased FL and MT with eccentric training. MT increased similarly among the synergistic muscles, while the muscle with the shortest FL at baseline (SO) showed the greatest increase in FL.

Time course of neuromechanical and morphological adaptations to triceps surae isokinetic eccentric training.

OBJECTIVES: To document the magnitude and the time course of neuromechanical and morphological adaptations in response to a triceps surae eccentric training program. METHODS: Twenty healthy male subjects completed a control period followed by a 12-week isokinetic eccentric training program. Triceps surae neuromechanical and morphological evaluations were performed every 4 weeks. RESULTS: The training program led to increases in: eccentric (32%), isometric (13%) and concentric (20%) torques; eccentric (32%) and isometric (24%) electromyographic activity; and, muscle thickness (14%). Torque and muscle thickness increased until the 8th training week. Eccentric and isometric activation increased until the 4th training week. No change was found in concentric activation. The angles of peak torque in eccentric and concentric tests shifted towards longer muscle lengths. While eccentric and isometric strength gains are explained by increased neural activation and muscle mass, changes in concentric torque are not related to neural effects. CONCLUSIONS: Eccentric training led to increases in maximum eccentric and isometric force production due to adaptations in muscle activation and muscle mass. Among the advantages of the shift in the optimal length for force production towards longer lengths, are the increased total joint range of motion and a lower predisposition for muscle strain injuries.

Ingestion of carbohydrate or carbohydrate plus protein does not enhance performance during endurance exercise: a randomized crossover placebo-controlled clinical trial.

A beverage containing protein (PRO) and carbohydrate (CHO) may have an ergogenic effect on endurance performance. However, evidence regarding its efficacy on similar conditions to athletes' race day is still lacking. The objective of this study was to compare the effects of 3 different nutritional supplementation strategies on performance and muscle recovery in a duathlon protocol. Thirteen male athletes (29.7 ± 7.7 years) participated in 3 simulated Olympic-distance duathlon trials (SDTs) under 3 different, randomly assigned supplementation regimens: CHO drink (75 g CHO), isocaloric CHO plus PRO drink (60.5 g CHO and 14.5 g PRO), and placebo drink (PLA). Supplements were offered during the cycling bout. Blood samples were collected before, immediately after, and 24 h after each SDT for creatine kinase (CK) analysis. Isometric peak torque (PT) was measured before and 24 h after each SDT. The primary outcome measure was the time to complete the 5-km running section (t5km) at a self-selected pace. There was no difference in t5km between CHO (1270.3 ± 130.5 s), CHO+PRO (1267.2 ± 138.9 s), and PLA (1275.4 ± 120 s); p = 0.87, effect size (ES) ≤ 0.1. Pre-post changes for PT and CK were not significant for any of the 3 conditions (PT: p = 0.24, ES ≤ 0.4; CK: p = 0.32, ES = 0.3-1.04). For endurance sports lasting up to 2 h, with a pre-exercise meal containing CHO at 1.5 g·kg-1, supplementation with CHO or CHO+PRO does not offer additional benefits for performance and muscle recovery when compared with PLA.

Comparison of different frequencies of transcutaneous electrical diaphragmatic stimulation in healthy subjects: a randomized crossover clinical trial / Comparação de diferentes frequências da estimulação diafragmática elétrica transcutânea em indivíduos saudáveis: ensaio clínico randomizado cruzado

Most transcutaneous electric diaphragmatic stimulation (TEDS) studies use a stimulation frequency (SF) of 30 Hz, although the reason for this SF value is not completely understood. Objective:The purpose of this study was to compare the acute effect of two TEDS frequencies on the respiratory muscle strength and endurance, muscle activation, muscle thickness, diaphragmatic mobility, cardiovascular variables and safety in healthy subjects. Methods:Randomized crossover clinical trial with 20 healthy subjects subjected to two interventions: SF=30 Hz group and SF=80 Hz group. TEDS was applied at the diaphragm motor points with a symmetric biphasicpulsed current (pulse duration= 500 µs) for 30 minutes. The evaluated outcomes were systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), respiratory muscle strength by maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), inspiratory peak flux (PIF), diaphragm thickness during inspiration (DTI) and expiration (DTE), diaphragm mobility and activation, and endurance (S-Index). Results:SF-30 Hz showed a reduction with respect to baseline values for SBP (p=0.04), HR (p<0.001), DTE (p=0.02), IPF (p=0.01), and S-Index (p=0.03). SF-80 Hz showed a reduction with respect to baseline values for HR (p<0.001) and an increase in MEP (p<0.001). However, these changes were not clinically important and there were no between-groups differences for any of the evaluated outcomes. No complications were observed. Conclusion:TEDS with SF-80 Hz produces similar effects to SF-30 Hz in healthy subjects and bothfrequencies proved to be safe (NCT03844711).

A maioria dos estudos utilizam a estimulação diafragmática elétrica transcutânea (EDET) com frequência (F) de estímulo de 30Hz e testar diferentes frequências torna-se necessário para uma aplicação otimizada. Objetivo: Foi comparar o efeito agudo de duas frequências diferentes da EDET sobre a força muscular respiratória e endurance, ativação diafragmática, espessura muscular e mobilidade diafragmática, variáveis cardiovasculares e segurança em indivíduos saudáveis. Métodos: Estudo randomizado cruzado com 20 indivíduos saudáveis submetidos a duas intervenções: Grupo I com F= 30Hz e Grupo II com F= 80Hz. A aplicação foi nos pontos motores do diafragma, com duração do pulso de 500µs, durante 30 minutos. Foram avaliados a pressão arterial sistólica (PAS) e diastólica (PAD), frequência cardíaca (FC), força muscular respiratória pela pressão inspiratória máxima (PImax), pressão expiratória máxima (PEmax), endurance e espessura muscular em inspiração (EDI) e expiração (EDE), mobilidade e ativação diafragmática. Resultados: O GI apresentou redução significativa em comparação às condições basais para os desfechos de PAS (p= 0.04), FC (p<0.001), EDI (p= 0,02), PIF (p= 0.01), e S-Index (p= 0.03). O GII apresentou redução significativa em comparação às condições basais para FC (p<0.001) e aumento da PEmax (p<0.001). Porém, estas alterações não foram clinicamente importantes e não houve diferença entre os grupos para nenhum desfecho avaliado. Nenhuma intercorrência foi observada. Conclusão: A EDET com F-80Hz produz efeitos semelhantes a F-30Hz em indivíduos saudáveis e ambas as frequências provaram ser seguras (NCT03844711).

Neuromuscular electrical stimulation (NMES) reduces structural and functional losses of quadriceps muscle and improves health status in patients with knee osteoarthritis.

Knee osteoarthritis (OA) is associated with quadriceps atrophy and weakness, so muscle strengthening is an important point in the rehabilitation process. Since pain and joint stiffness make it often difficult to use conventional strength exercises, neuromuscular electrical stimulation (NMES) may be an alternative approach for these patients. This study was aimed at (1) identifying the associations of knee OA with quadriceps muscle architecture and strength, and (2) quantifying the effects of a NMES training program on these parameters. In phase 1, 20 women with knee OA were compared with 10 healthy female, asymptomatic, age-matched control subjects. In phase 2, 12 OA patients performed an 8-week NMES strength training program. OA patients presented smaller vastus lateralis thickness (11.9 mm) and fascicle length (20.5%) than healthy subjects (14.1 mm; 24.5%), and also had a 23% smaller knee extensor torque compared to the control group. NMES training increased vastus lateralis thickness (from 12.6 to 14.2 mm) and fascicle length (from 19.6% to 24.6%). Additionally, NMES training increased the knee extensor torque by 8% and reduced joint pain, stiffness, and functional limitation. In conclusion, OA patients have decreased strength, muscle thickness, and fascicle length in the knee extensor musculature compared to control subjects. NMES training appears to offset the changes in quadriceps structure and function, as well as improve the health status in patients with knee OA.

Effects of strength training and detraining on knee extensor strength, muscle volume and muscle quality in elderly women.

Strength training seems to be an interesting approach to counteract decreases that affect knee extensor strength, muscle mass and muscle quality (force per unit of muscle mass) associated with ageing. However, there is no consensus regarding the changes in muscle mass and their contribution to strength during periods of training and detraining in the elderly. Therefore, this study aimed at verifying the behaviour of knee extensor muscle strength, muscle volume and muscle quality in elderly women in response to a 12-week strength training programme followed by a similar period of detraining. Statistical analysis showed no effect of time on muscle quality. However, strength and muscle volume increased from baseline to post-training (33 and 26 %, respectively). After detraining, the knee extensor strength remained 12 % superior to the baseline values, while the gains in muscle mass were almost completely lost. In conclusion, strength gains and losses due to strength training and detraining, respectively, could not be exclusively associated with muscle mass increases. Training-induced strength gains were partially maintained after 3 months of detraining in elderly subjects.

Neuromuscular adaptations to concurrent training in the elderly: effects of intrasession exercise sequence.

The aim of this study was investigate the effects of different intrasession exercise orders in the neuromuscular adaptations induced by concurrent training in elderly. Twenty-six healthy elderly men (64.7 ± 4.1 years), were placed into two concurrent training groups: strength prior to (SE, n = 13) or after (ES, n = 13) endurance training. Subjects trained strength and endurance training during 12 weeks, three times per week performing both exercise types in the same training session. Upper and lower body one maximum repetition test (1RM) and lower-body isometric peak torque (PTiso) and rate of force development were evaluated as strength parameters. Upper and lower body muscle thickness (MT) was determined by ultrasonography. Lower-body maximal surface electromyographic activity of vastus lateralis and rectus femoris muscles (maximal electromyographic (EMG) amplitude) and neuromuscular economy (normalized EMG at 50 % of pretraining PTiso) were determined. Both SE and ES groups increased the upper- and lower-body 1RM, but the lower-body 1RM increases observed in the SE was higher than ES (35.1 ± 12.8 vs. 21.9 ± 10.6 %, respectively; P < 0.01). Both SE and ES showed MT increases in all muscles evaluated, with no differences between groups. In addition, there were increases in the maximal EMG and neuromuscular economy of vastus lateralis in both SE and ES, but the neuromuscular economy of rectus femoris was improved only in SE (P < 0.001). Performing strength prior to endurance exercise during concurrent training resulted in greater lower-body strength gains as well as greater changes in the neuromuscular economy (rectus femoris) in elderly.