Search Results (520)

Background: Astragali radix is a traditional herb known for its antioxidant, anti-inflammatory, and immunomodulatory properties and has gained attention for its potential to support post-exercise recovery. However, the effects of long-term supplementation coupled with resistance training are not well understood. Methods: Twenty-four moderately active participants were recruited and randomly assigned to the Astragali radix supplementation (ASTRA, n = 13) or placebo (PLA, n = 11) group. All participants underwent 8 weeks of regular resistance training (3 sessions/week) and 2 weeks of intensified training (6 sessions/week). Results: Before (BAS), after 8 weeks of resistance training (RT), and at the end of the intensified training (IT), knee extensors’ maximal voluntary isometric contraction torque (MVIT), and leg press and leg extension one repetition max (1RM) were measured. Blood samples were collected to analyze inflammatory markers and testosterone. From BAS to after RT, MVIT, 1RM leg press, and 1RM leg extension increased in both ASTRA and PLA, with no differences between groups. After IT, MVIT, 1RM leg press and 1RM leg extension decreased in both ASTRA and PLA. CPK levels and myoglobin concentration increased while cortisol decreased significantly from BAS to IT, but no group differences were detected. TNF-α and IL-6 showed significant time × supplementation interactions, with lower values after IT in ASTRA compared to PLA. Conclusions: Astragali radix supplementation did not lead to additional benefits in muscle during the period of resistance training, nor did it prevent the decline in force following the intensified training period. However, Astragali radix supplementation prevented the increase in some inflammatory biomarkers, specifically TNF-α and IL-6, during the intensified period of training. Full article

Background: Sunfish sailing requires a combination of morphological and neuromuscular characteristics to effectively manage sail control and maintain postural stability during hiking maneuvers. Objectives: We aimed to describe the anthropometric and neuromuscular characteristics of elite Colombian Sunfish sailors and explore potential sex-related patterns. Methods: Six competitive sailors (three men and three women) underwent anthropometric assessment and somatotype calculation. Neuromuscular performance was evaluated using handgrip strength (HGS), quadriceps maximal voluntary isometric contraction, rate of force development (RFD), one-repetition maximum (1RM) lower-limb assessment, countermovement jump (CMJ), trunk endurance tests, and the Y-balance test for dynamic balance. Descriptive statistics and standardized effect sizes (Hedges’ g) were used to characterize between-sex patterns. Results: Anthropometric assessments suggested descriptive sex-related differences in body composition and skeletal dimensions, with a predominance of mesomorphic characteristics. Descriptive data suggested higher HGS values among men (g = 2.27–4.85), while lower-limb neuromuscular performance showed higher values among men across several RFD time windows (g = 0.81–1.45). Conversely, dynamic balance and trunk endurance outcomes showed minimal variation between sexes. Conclusions: This pilot study provides a preliminary physical profile of elite Colombian Sunfish sailors. The observed patterns in strength-related and morphological variables, especially HGS, quadriceps MVIC, and lower-limb power, should be interpreted as exploratory. Further research with larger samples is required to confirm these findings. Full article

Background: This study aimed to investigate the extent and time course of peripheral neuromuscular fatigue of the knee extensors following different concurrent training protocols in recreationally active men. Methods: In a randomized, counterbalanced, crossover design, ten participants completed one exercise session of three concurrent exercise protocols in consecutive weeks and in similar resting conditions: traditional concurrent training (TCT), sprint interval training (SIT), and high-intensity resistance circuit training (HRC). Maximal voluntary isometric contraction (MVIC) and electrically evoked tetanic force of the knee extensors were assessed before, immediately after, and at 24 and 48 h following each exercise session. Linear mixed models were used to examine the differences among exercise modalities and time points. Results: No significant changes were found in MVIC force following HRC and TCT at any time point (p > 0.05), while significant declines were observed post-exercise (p = 0.015), 24 h (p = 0.001) and at 48 h (p = 0.003) after SIT. Moreover, MVIC force was significantly lower for SIT than HRC at 48 h (p = 0.001). Tetanic force significantly declined in SIT from pre-exercise to post-exercise (p = 0.034), with significant differences when compared to HRC (p = 0.003) and TCT (p = 0.003). HRC and TCT induced no knee extensor fatigue, contrary to a single session of SIT. Conclusions: Peripheral fatigue seemed to prevail following SIT in comparison with HRC and TCT, as seen by the decreased tetanic force in the former only. From an applied perspective, practitioners should carefully plan training activities to be performed the days following a SIT session, as force-generating capacity may be impaired for up to 48 h. Full article

Transcranial direct current stimulation (tDCS) over motor–premotor regions may modulate motor performance, though underlying mechanisms remain unclear. Twenty-four athletes (9 females, 15 males) were randomly assigned to receive anodal tDCS (2 mA, 20 min) over the left sensorimotor cortex (n = 12) or sham stimulation (n = 12). Participants performed a bimanual isometric force-matching task at 30% maximal voluntary contraction, with visual feedback initially provided and then removed. Force undershoot, root mean square error (RMSE), spectral power (1–3 Hz), and inter-hand coherence were analyzed. A computational model was developed to test whether enhanced proprioceptive feedback processing could account for observed effects. Following tDCS, force undershoot decreased significantly (p = 0.002, d = −1.15) and RMSE improved (p = 0.010, d = −0.91). Spectral power in the 1–3 Hz band increased (p = 0.012, d = 0.87), suggesting enhanced corrective oscillations. These within-group changes were absent in the sham group (all p > 0.20), although Group × Epoch interactions did not reach significance (all p > 0.05), likely due to limited statistical power. Inter-hand coherence remained unchanged. The computational model demonstrated that enhanced proprioceptive feedback gain qualitatively reproduces the observed behavioral pattern. Anodal tDCS over the left sensorimotor/premotor region may enhance bimanual force control under conditions requiring proprioceptive feedback. Replication with larger samples is needed to confirm between-group specificity. Full article

Background: Soccer aerial duels require rapid take-off, repeated-performance maintenance, and effective head–neck control under physically demanding conditions. This study examined the effects of caffeine (CAF), Rhodiola rosea (RHO), and their combination on repeated aerial duel performance and neck neuromuscular function in male collegiate soccer players. Methods: Ninety-six players were randomly assigned, in a double-blind, placebo-controlled, parallel design, to placebo control (CTR), RHO, CAF, or RHO + CAF groups (n = 24 each) for 4 weeks. CAF was acutely administered at 3 mg·kg⁻¹ before testing, whereas RHO was chronically supplemented at 2.4 g·day⁻¹. Outcome measures included countermovement jump height, early take-off impulse, repeated heading contact height, ball exit velocity, heading duel success rate, neck maximal voluntary isometric contraction, and session rating of perceived exertion (session-RPE). Results: Significant group × time or group × repetition effects were observed for CMJ height (p = 0.0034), early take-off impulse (p = 0.0007), and post-intervention repeated heading contact height (p < 0.0001), with additional significant effects across heading-specific, neck strength, duel-success, and perceived-load outcomes. CAF was mainly associated with improved take-off-related explosive performance and duel success, whereas RHO was mainly associated with lower perceived exertion and better maintenance of heading contact height during the later repeated trials. Combined RHO + CAF supplementation produced the broadest pattern of benefits across explosive output, ball-contact performance, duel success, and multidirectional neck strength. Conclusions: These findings suggest that, in male collegiate soccer players, CAF and RHO may contribute differently to repeated aerial duel-related performance, and their combination may offer broader sport-specific benefits under repeated high-intensity demands. Full article

Artificial muscles such as braided pneumatic actuators (BPAs) offer many advantages for robotic systems, including high durability and strength-to-weight ratios. However, their use in robotic systems is still extremely limited, in part due to their poor force, length, and pressure characterization. In this work, a test setup is created to compare force produced by Festo fluidic BPAs with leading models. Our analysis of the data has resulted in (1) the development of new equations to calculate force as functions of pressure and contraction for Festo BPAs with uninflated diameters of 10 mm and 20 mm, and (2) a novel equation for the maximum force in 10 mm and 20 mm diameter Festo BPAs as a function of their resting length. This will lead to faster design processes and the development of new systems such as biomimetic robots that are able to more accurately reproduce the range of motion and isometric torque profiles that exist in the animals they are mimicking. Full article

Background: Although several studies have compared muscle activity in ‘healthy’ and ‘unhealthy’ shoulders, studying ‘healthy’ shoulders alone could improve the understanding of shoulder biomechanics. Objective: This study aims to describe the electromyographic activity of several shoulder muscles during a full range of free active flexion, as well as during abduction and scaption movements, and to compare gender differences in subjects with no history of shoulder pain or pathology. Methods: A cross-sectional descriptive study was conducted with 34 subjects aged between 18 and 60 years of both genders. The activity of the anterior, middle, and posterior deltoid, serratus anterior, infraspinatus, latissimus dorsi, and teres major muscles was measured using surface electromyography. Root Mean Square (RMS) values were calculated as a percentage of Maximal Voluntary Isometric Contraction (MVIC). Results: Regardless of whether they are considered agonists or antagonists, these muscles were active, with no statistically significant differences (Mann–Whitney U test), during both the lifting and lowering phases of the studied movements. Statistically significant differences between movements were observed only in the deltoid (Kruskal–Wallis H test, p < 0.004), which was more active during abduction. Women showed statistically significant muscle activity increase compared with men in some movements, except in the infraspinatus muscle—for example, in the three parts of the deltoid during the lifting phase of scaption (ANCOVA, p = 0.002–0.024). Conclusions: In this sample, the shoulder muscles studied showed comparable activity, acting as agonists or antagonists during shoulder elevation. These findings are exploratory and may help inform future studies on muscle activation in healthy shoulders during more varied functional tasks. Full article

Aim: The aim of this study was to determine the influence of squat depth during an isometric conditioning activity on the magnitude and time course of acute changes in countermovement jump (CMJ) performance. Methods: In a parallel-group design, twenty-four resistance-trained males performed three 4-s maximal voluntary contractions using either a maximal-depth squat or a half-squat (~90° knee angle). CMJ height was assessed before the conditioning activity and at 3, 6, 9, and 12 min post-activation. Data were analyzed using a two-way mixed-model ANOVA, and simple linear regression analyses were performed to examine whether relative strength, training experience, and weekly training volume were associated with the magnitude of CMJ performance changes. Results: A significant main effect of time was observed for CMJ performance (F = 7.81, p < 0.001, ηp² = 0.26). Post hoc comparisons showed significantly greater CMJ performance at 6 min (p < 0.001; ES = 0.96) and 9 min (p = 0.008; ES = 0.80) compared with baseline. In addition, CMJ performance at 6 min (p = 0.021; ES = 0.71) and 9 min (p = 0.028; ES = 0.69) was significantly greater than at 3 min post-activation, whereas no significant differences were observed between baseline and 3 min or 12 min. No significant main effect of squat depth (F = 0.003, p = 0.958, ηp² < 0.001) or time × squat depth interaction (F = 0.58, p = 0.650, ηp² = 0.03) was found. Conclusions: These findings indicate that squat depth during maximal isometric conditioning activity did not significantly influence either the magnitude or the temporal pattern of post-activation changes in CMJ performance. Greater CMJ values were observed 6–9 min after the conditioning activity, suggesting that, within the tested protocol, recovery timing may be of greater practical importance than squat depth when implementing isometric conditioning strategies to enhance jump performance. Full article

This two-step design used the unilateral bench press to examine the effect of breast cancer surgery on upper-limb muscle activation under low and moderate fatigue conditions. First, we studied the proper method to normalize the activation values obtained during dynamic contractions. For that, the muscle activation was relativized to the maximal value obtained during (i) an isometric contraction (ISO_Norm), and the concentric phase of the (ii) repetition maximum load (1RM_Norm), and (iii) the first three repetitions of an 80% 1RM set (Max80%_Norm). The normalization method with the lowest inter-subject variability was further used to compare the muscle activation of the affected and non-affected sides of twelve women who underwent unilateral breast surgery (eight mastectomies and four lumpectomies). Both sides were tested using dynamic sets at 60 and 80% of their 1RM until reaching 40% velocity loss (VL). Repetitions completed at each %1RM were then divided into two groups: low fatigue (first half of repetitions) and moderate fatigue (second half of repetitions). On results, the ISO_Norm and the Max80%_Norm showed the highest (mean CV = 32.9%) and lowest (mean CV = 12.9%) inter-subject variability, respectively. The affected side showed higher activation for the deltoid and triceps (Δ = 6.9 to 15.9%) but lower for the pectoralis (Δ = −5.7 to −13.2%) against 60% 1RM. These differences were lower and without a consistent trend against 80% 1RM. Between-side comparisons were not significant for either 60% 1RM (p > 0.270) or 80% 1RM (p > 0.500). Although these results should be interpreted with caution due to the small and heterogeneous sample, our analyses did not reveal meaningful differences in upper-limb muscle activation following breast cancer surgery. Full article

(1) Background: Handgrip strength (HGS) is a widely used indicator of neuromuscular function, with predictive values for health and performance outcomes. The aim of this study was to evaluate the intraday and interday reliability of maximal and explosive handgrip force–time metrics using the Kinvent K-Grip handheld dynamometer. (2) Methods: Thirty-four participants performed three maximal voluntary isometric contractions per hand across two testing days. Force–time data were analysed for peak force (PF), mean force (MF), peak rate of force development (RFD), time-specific RFD, impulse, and forces at fixed time points. Reliability was assessed using intraclass correlation coefficients (ICCs), standard error of measurement (SEM), minimal detectable change (MDC), and coefficient of variation (CV%). (3) Results: The device demonstrated excellent relative and absolute reliability for PF and MF across both days (ICC > 0.97; CV < 6%; MDC ≈ 5 kg). Later-phase explosive metrics (F250 and Imp200) showed good-to-excellent relative reliability (ICC = 0.88-0.99; CV = 4–14%), although with variable absolute reliability (MDC F250 ≈ 4–8 kg, MDC Imp200 ≈ 1 kg·s). For early-phase metrics, relative reliability was only moderate to good (ICC = 0.67–0.88) and characterised by a high degree of variability (CV = 15–22%). (4) Conclusions: The K-Grip handheld dynamometer is a reliable tool for cross-sectional assessments and for tracking larger maximal strength and later-phase force improvements at fixed time points. Early-phase explosive metrics are less suitable for monitoring intervention effects due to high measurement error and fatigue sensitivity. Full article

Background: Passive movement-based recovery strategies may support post-exercise recovery without additional metabolic demand. Objective: To examine the acute effects of passive foot flexions during recovery on isometric task performance after repeated exercise. Methods: Fourteen physically active men completed two randomized crossover sessions—passive rest and passive foot flexions—separated by a 7-day washout. Each session included a sustained static isometric plantar flexion task at 75% of maximal voluntary contraction (MVC), a 15 min recovery period, and a repeated isometric task. Work capacity was assessed as holding time. Cardiovascular, autonomic, and peripheral responses were recorded throughout the protocol. Results: Baseline holding time did not differ between the conditions. During the repeated isometric task, holding time was significantly longer following passive foot flexions compared to passive rest (67.7 ± 10.4 s vs. 52.9 ± 9.7 s; p < 0.05), with a large effect size (d ≈ 1.5). Passive foot flexions were associated with a greater increase in parasympathetic modulation, reflected by higher root mean square of successive differences (RMSSD) during recovery and altered muscle oxygenation dynamics, including faster post-exercise re-oxygenation. For both conditions, heart rate and systolic and diastolic blood pressure exhibited similar exercise–recovery patterns with no between-condition differences. Only minor changes in muscle stiffness were observed following the passive foot flexions. Conclusions: Passive foot flexions may support short-term recovery between repeated isometric efforts, particularly with respect to holding time and RMSSD. Full article

Background/Objectives: We investigated whether ingestion of caffeine (~1 h before) was beneficial to subsequent morning (07:30 h), mood, strength and cognitive measures. Methods: Fourteen recreationally active males were recruited and completed six sessions: (i) one repetition maximum (1RM) for bench press and back squat; (ii) two familiarization sessions of strength measures; (iv) three experimental conditions administered in a double-blinded, randomized counterbalanced design order, either caffeine (Caffeine [CAFF], 300 mg or 2.8–4.3 mg/kg body weight), placebo (Placebo [PLAC]) ingested at 06:30 h, or no-pill control (No Pill [NoPill]). For each experimental session, on arrival at the laboratory, rectal and skin temperature were measured as well as a battery of cognitive performance through a battery of tests (trail-making test, Rey’s auditory verbal learning test, and Stroop word–colour interference test). Thereafter, maximum voluntary contraction on an isometric chair (MVC) without and with stimulation was conducted, and three repetitions were performed at 40, 60 and 80% of 1RM for bench press and back squat. Average power (AP), average velocity (AV), peak velocity (PV), mean propulsive velocity (MPV), average acceleration (RDV), displacement (D) and time-to-peak velocity (tPV) were recorded using MuscleLab linear encoders. Rating of perceived exertion and effort was asked after each set (RPE). The data was analysed using a general linear model with repeated measures. Results: MVC peak-force values with and without stimulation showed a significant increase in the CAFF condition compared to values for NoPill and with stimulation PLAC conditions (stim: Δ9.0 and 8.7%; no stim: 8.3%; p < 0.05; η²_p = 0.33 and 0.42). Greater muscle % activation was achieved for the CAFF than the other conditions (~6%, p ≤ 0.042; η²_p = 0.33). In the non-stimulated MVC, RPE was perceived as easier (4.8%, p = 0.04). AV and MPV values were higher in both bench press (Δ3.3 and 4.6%) and back squat (Δ7.7 and 9.2%) in CAFF than the PLAC condition (p = 0.031; η²_p = 0.24 and 0.23 and 0.24 and 0.32). CAFF improved auditory total recall compared to NoPill (9.5%, p = 0.040; η²_p = 0.22). Conclusions: Early morning ingestion of caffeine improved MVC to levels observed by others in the evening, as well as some aspects of bench press, back squat and recall performance. Caffeine ingestion had no effect on core temperature, mood, tiredness, alertness or other measures of cognitive performance. Full article

Background: Self-myofascial release (SMFR) is a treatment whose main benefits are enhanced recovery and increased flexibility without impairing athletic performance. Previous research has often targeted the posterior myofascial chain (superficial back line, SBL), which runs from the plantar fascia to the posterior cranium and is commonly linked to hamstring-related outcomes. However, its potential influence on knee extensor force production remains unclear and would likely be indirect. Many SMFR tools have entered the market in recent years, with Auramat^® being one of them, yet it has not been investigated to date. Therefore, this study aimed to determine the effects of Auramat^® (AUR) on posterior-chain flexibility and knee extensor (KE) function and to compare them with those of a traditional warm-up (TW). Methods: This study was a randomised, counterbalanced, cross-over design where 20 recreationally active participants (12 males, 8 females; age = 27.20 ± 4.98 years) attended the laboratory 3 times over a 2-week period. The first week consisted of a familiarisation session during which participants performed several tests. In the second week, the groups that were randomly assigned at AUR or TW conditions performed the two intervention protocols separated by 48 h. The pre-post ratings of perceived exertion (RPE), maximal voluntary isometric contraction (MVIC), straight leg raise test (SLRT) and rate of force development (RFD) were measured. All tests were performed on the dominant limb. Results: There was no significant difference in RFD and MVIC for conditions (p = 0.91), time (p = 0.24), or condition × time (p = 0.41). Both conditions improved posterior chain flexibility (p ≤ 0.01) with a larger effect in TW (d = 2.03; ↑ 7.81%) compared to the AUR condition (d = 0.89; ↑ 3.69%). RPE for TW showed significant higher RPE values compared to the AUR condition (p ≤ 0.01; ES = 2.32; TW = 4.3 ± 1.45 vs. AUR = 1.55 ± 0.82). Conclusions: Both SMFR with AUR and TW increased flexibility without any significant reduction in KE force production. Practitioners may use TW in a session where the aim is an increase in flexibility and AUR when the time is limited and the increase in fatigue can be relevant, due to the lower RPE reported. In any case, these results should be taken with caution since even the AUR was more time-efficient; the findings are preliminary owing to the small sample and absence of a control condition. Full article

This study investigated how varying body positions (seated, prone, supine) and knee joint angles (90°, 120°, 150°) influence the bilateral deficit (BD) in isometric hamstring strength. Thirty physically active participants (15 males, 15 females) performed unilateral and bilateral maximal voluntary isometric contractions (MVICs) across the tested position × angle conditions. Peak force (Fmax) and rate of force development (RFD) measures (RFDmax, RFD50 ms, and RFD200 ms) were recorded. Results indicated that the seated position elicited a greater bilateral deficit (i.e., lower BD ratios) than the prone and supine positions, with differences that were more pronounced at more extended knee angles. These findings underscore the importance of considering position- and angle-specific influences when assessing BD in hamstring strength. Clinicians and researchers should standardize testing protocols to ensure accurate evaluation and data interpretation. From an applied standpoint, the results support the development of resistance-training strategies aimed at enhancing hamstring function at long muscle lengths—an approach relevant to both performance optimization and injury prevention. Full article

Resistance training machines are designed to provide either constant or variable resistance, with the latter intended to generate a machine resistive torque (MRT) that mirrors the natural fluctuations in human torque capability (HTC) across joint angles. Yet, achieving a precise match between MRT and HTC remains a persistent challenge. This study aimed to validate a novel variable-cam resistance system, the Variable Moment Arm Cam^® (VMAC^®), by examining torque output and muscle activation during leg extension across the full range of motion (100–0°), using repeated testing and direct comparison with an isokinetic dynamometer. Twenty-two young men completed four randomized sessions, two on the variable-cam system and two on the dynamometer, each separated by 72–96 h. Torque and muscle activity were recorded during six isometric contractions at 100°, 80°, 60°, 40°, 20°, and 0°. The variable-cam system produced torque and activation patterns broadly comparable to the dynamometer, with acceptable agreement across angles. Validity was highest at 60°, aligning with the region of peak torque, whereas greater variability emerged at the extremes of flexion and extension. Muscle activation profiles were similar between devices, though more variable than torque, underscoring the inherent complexity of neuromuscular assessment. Full article