Search Results (1,055)

Background: Small-sided games (SSG) and running-based high-intensity interval training (HIIT) are commonly used in soccer conditioning to improve aerobic fitness and performance. Although both modalities induce high cardiovascular stress, their acute neuromuscular, perceptual, and cognitive responses remain incompletely understood when examined within the same cohort. This study compared the acute physical, psychophysiological, and cognitive responses to SSG and Tabata-type HIIT in amateur male soccer players. Methods: Thirty-two male amateur players (n = 32; age: 20.53 ± 1.65 years) completed a counterbalanced within-subject crossover design. Participants performed a 4v4 SSG protocol and a running-based Tabata-HIIT protocol (8 × 20 s, 10 s recovery) on separate days (48 h apart). Countermovement jump (CMJ), squat jump (SJ), 20-m sprint, agility t-test, heart rate, perceived exertion (Borg CR-10), mental effort, and cognitive performance (d2 test) were assessed pre- and post-exercise. Parametric variables were analyzed using 2 × 2 repeated-measures ANOVA (time × protocol; η²p), and non-parametric data were analyzed using Friedman and Wilcoxon tests (r) (p < 0.05). Results: Both protocols elicited similar cardiovascular responses (~90% HR_max). A significant protocol × time interaction was observed for CMJ (p < 0.001), showing a decline after Tabata-HIIT, whereas performance was maintained after SSG. No inter-protocol differences were found for SJ, sprint, or agility. Perceived exertion and mental effort during recovery were higher following Tabata-HIIT (p < 0.05). Cognitive performance improved after both protocols (p < 0.001), with no between-protocol differences. Conclusions: Despite comparable cardiovascular load, Tabata-HIIT was associated with greater acute neuromuscular and perceptual strain, whereas SSG preserved neuromuscular performance. Perceptual and mental responses may therefore differ despite similar physiological intensity, which may inform soccer training prescription. Full article

Understanding knee kinematics during gait is essential for the design of prostheses, orthoses, and biomimetic mechanisms. In many biomechanical analyses, tibiofemoral motion is simplified to the sagittal plane, allowing the locus of the instantaneous center of rotation (ICR) to describe joint kinematics derived from the instantaneous axis of rotation (IAR). However, it remains unclear whether ICR trajectories obtained from simplified flexion–extension tasks can represent those observed during gait. This study analyzes the sagittal-plane trajectory of the tibiofemoral ICR during gait swing, standing swing, seated swing, and squat. Motion data from 21 healthy participants were captured using videogrammetry, and the instantaneous axis of rotation (IAR) was computed from homogeneous transformation matrices using the Mozzi–Chasles theorem. Sagittal-plane ICR trajectories were derived and compared within subjects across tasks. Significant differences were found between gait and all other movements in both trajectory shape and spatial position. The shape metric (S), which quantifies differences in trajectory geometry, showed mean values ranging from 0.82 to 1.04 with very large effect sizes (Cohen’s d = 2.90 to 4.47, p < 0.0001). The centroid distance metric (M), which measures the overall spatial displacement between trajectories, indicated positional differences ranging from 8.15 mm to 12.37 mm between trajectories also showing very large effect sizes (Cohen’s = 1.72–3.40, p < 0.0001). Additionally, the mean deviation of the IAR from the sagittal plane ranged from 14° to 18° during gait, whereas smaller deviations were observed in non–weight-bearing swing movements. These results demonstrate that tibiofemoral ICR trajectories are task-dependent and that simplified flexion–extension tasks do not fully reproduce the knee kinematics observed during gait. Consequently, the use of gait-derived ICR trajectories, together with their variability, provides a more suitable basis for the design and optimization of polycentric mechanisms, enabling the development of devices that more closely replicate real biomechanics and are potentially better adapted to the user. Full article

The Stretch-Shortening Cycle (SSC) is a fundamental neuromuscular mechanism that enhances explosive performance by storing and releasing elastic energy, particularly through the Achilles tendon. While tendon stiffness and neuromuscular coordination are known to influence SSC efficiency, the role of ankle joint mobility in this context remains unclear. This study aimed to investigate the relationship between ankle dorsiflexion range of motion and SSC contribution during vertical jump performance in trained adults. Twenty-seven physically active participants (19 males, 8 females) were assessed for ankle dorsiflexion using the Leg Motion system and performed both Squat Jump (SJ) and Countermovement Jump (CMJ) on a force platform. SSC contribution was calculated as the difference between CMJ and SJ heights, expressed in both absolute (centimeters) and relative (percentage) terms. Participants were categorized into high and low mobility groups based on the median dorsiflexion value (13 cm). Statistical analyses, including Pearson correlation (r = −0.262, p = 0.186), linear regression (R² = 0.069), and independent t-tests, showed no significant association between ankle mobility and SSC contribution. No meaningful performance differences were observed between the two groups in CMJ, SJ, or SSC metrics. These findings suggest that ankle dorsiflexion does not independently predict SSC utilization in vertical jumping among trained individuals. Other factors such as tendon stiffness, explosive strength, and neuromuscular coordination may play a more decisive role. Future research should include dynamic mobility assessments and more diverse populations to better understand the interplay of these variables. Full article

The purpose of this study was to examine differences between squat variations performed with a traditional barbell (TRAD) and a safety squat bar (SSB) in university athletes, focusing on mean propulsive velocity (MPV), peak velocity (PV), and velocity loss (VL). Nineteen university athletes participated in a randomized crossover repeated-measures design. Participants performed squat exercises with both barbell types at 65% and 85% of one-repetition maximum (1RM) across multiple testing sessions. Neuromuscular performance indicators were assessed using a linear velocity transducer. Two-way repeated-measures ANOVA revealed significant main effects of barbell type and load for MPV and PV (all p < 0.05). Higher MPV values were observed with the SSB at both loading intensities, whereas higher PV values were observed only at 85% 1RM. For VL, a significant main effect of barbell type was found (p = 0.013), with no significant effect of load (p = 0.155) or interaction (p = 0.507). In conclusion, the SSB elicited higher movement velocities compared with the traditional barbell. These findings suggest that barbell selection may influence velocity-based performance outcomes during squat exercise. However, due to the cross-sectional design, these results should be considered preliminary. Full article

Introduction: Circuit resistance training is widely used to enhance physical performance. However, the acute-performance- and fatigue-related effects of exercise order and volume in circuit training, particularly between upper and lower limbs, remain unclear. Objectives: This study examined acute velocity-based responses to different exercise orders and volumes during full-body circuit resistance training. Methods: Thirty resistance-trained adults completed four circuit protocols: alternating exercises with maximal repetitions per exercise (A1), grouped exercises with maximal repetitions per exercise (G1), alternating exercises with 50% of maximal repetitions in the first round (A2), and grouped exercises with 50% of maximal repetitions in the first round (G2). Mean propulsive velocity (MPV) in the bench press and squat at 60% 1RM was assessed before and after each circuit. Results: A significant main effect of Time was observed for both bench press and squat MPV (p < 0.001), with no Intervention × Time interactions. Alternating configurations showed larger effect sizes, indicating greater velocity loss. Under equal volume, upper limbs exhibited greater performance decline than lower limbs. Conclusions: Although exercise order did not result in statistically significant differences, alternating configurations induced a greater magnitude of fatigue-related performance decline than grouped configurations, particularly in upper-body exercises. Full article

Muscle size and architecture’s contribution to force and power production in young female acrobatic gymnasts (ACROs) remains unclear. This cross-sectional study examined the associations between quadriceps muscle size and architecture and strength–power performance in young elite female ACROs. Twenty base athletes (12–18 years) underwent ultrasound assessment of rectus femoris (RF) and vastus lateralis (VL) cross-sectional area (CSA), VL muscle volume, VL fascicle length, and VL pennation angle. Participants were additionally classified as pre/mid-pubertal (Tanner stages 1–3) and post-pubertal (Tanner stages 4–5) for descriptive analyses. Performance testing included one-repetition maximum (1RM) squat and hang power clean (HHPC), squat power (Pmax), and countermovement jump (CMJ). In adjusted (Tanner stage and height) linear regression models, VL CSA at 35% and 50% of femur length was positively associated with 1RM squat (β = 2.38–2.31 kg·cm⁻²; p = 0.031–0.011) and Pmax (β = 45.75–38.43 W·cm⁻²; p < 0.001). No associations were observed for CMJ, HHPC, or RF variables. Mid-thigh VL size appears to be an independent predictor of squat strength and power in ACRO. Full article

Background: This study examined the associations between dynamic maximum strength (front squat [FS] and clean [CL]), lower-limb vertical force–velocity (F–V) profile characteristics, and both absolute and scaled measures of competitive weightlifting performance in trained weightlifters. Methods: Fourteen competitive male weightlifters (age: 27.6 ± 4.2 years; height: 1.74 ± 0.05 m; body mass: 85.1 ± 6.7 kg; body fat: 11.7 ± 2.8%) completed three testing sessions separated by 48–72 h, including 1-RM assessment in the FS and CL, as well as vertical countermovement jump trials to determine individual force–velocity profile parameters (F₀, V₀, and Pmax). Official competition results obtained within the same competitive season were recorded for the snatch (SN), clean and jerk (C&J), total (TOT), and Sinclair score. Participants were additionally divided into higher and moderate jump performance groups using a median split of unloaded countermovement jump height. Results: Very strong correlations were found between 1-RM strength (FS and CL) and weightlifting performance, with CL showing the strongest associations with SN (r = 0.82), C&J (r = 0.93), and TOT (r = 0.94). Among F–V parameters, V₀ and Pmax were significantly associated with competitive outcomes (r = 0.63–0.70), whereas F₀ was not. V₀ was significantly associated with SN (r = 0.69), C&J (r = 0.63), and TOT (r = 0.70), while F₀ showed trivial-to-small associations (r = 0.08–0.28). When participants were divided using a median split of CMJ height, higher jumpers exhibited greater V₀ (3.02 ± 0.30 vs. 2.61 ± 0.23 m·s⁻¹, p = 0.014, g = 1.4) and relative Pmax (32.44 ± 2.65 vs. 27.28 ± 1.06 W·kg⁻¹, p = 0.001, g = 2.4), despite similar F₀ (p = 0.67). Higher jumpers also demonstrated superior SN (p = 0.016, g = 1.4), C&J (p = 0.041, g = 1.1), TOT (p = 0.018, g = 1.4), and Sinclair scores (p = 0.001, g = 2.1). Conclusions: In trained weightlifters, performance was strongly associated with maximal strength, while velocity- and power-oriented characteristics (V₀ and Pmax) were also associated with performance outcomes. In contrast, F₀ showed no meaningful associations with performance within this sample. These findings suggest that, among already strength-trained athletes, the ability to express force at higher contraction velocities may be associated with differences in competitive performance. Full article

To investigate how knee joint protector design affects the biomechanical characteristics of knee motion under various activities, this pilot study (n = 5) examined how knee joint protector design modulates knee biomechanics across walking, jogging, squatting, and sit-to-stand tasks using optical motion capture and AnyBody musculoskeletal modeling (FullBody_GRFPrediction). We quantified knee flexion kinematics, model-estimated joint reaction forces and moments, and model-estimated muscle activity of eight lower-limb muscles under four conditions with different levels of structural constraint: no protector (Pro.off), a conventional sleeve-type protector (Pro.a), a segmented support protector (Pro.b), and a wrapping fixation protector (Pro.c). The biomechanical protective performance of the knee joint protector was task- and phase-dependent. The results showed that Pro.a optimized muscle activation. Pro.b increased sagittal-plane design but increased joint loading and muscle activity. Pro.c induced noticeable distal compensation along the kinetic chain. The findings revealed that protector effects were task-dependent. Dynamic tasks mainly affected coronal-plane stability parameters, whereas quasi-static tasks more clearly altered sagittal load distribution. In this study, biomechanical protective performance is defined as reduced knee joint loading without disproportionate increases in model-estimated muscle activity or excessive loss of functional knee flexion range. Under this definition, greater structural constraint did not consistently produce a more favorable biomechanical profile. These results provide a feasibility baseline for task-specific protector evaluation and motivate confirmatory studies with larger cohorts and experimental validation. This study provides theoretical and methodological insights to guide future design and optimization of knee joint protectors. Full article

Background: The back squat is a key strength and conditioning exercise used to develop lower-limb strength and power, yet little is known about how movement velocity influences its acute performance-enhancing effects, such as improvements in countermovement jump height and power. The present study examined the acute effects of slow (v_slow) versus fast (v_fast) eccentric-phase velocity during back squats performed withmaximal concentric velocity on subsequent countermovement jump (CMJ) performance, using a randomized, crossover design. Methods: Fourteen male subjects (age = 22.9 ± 1.9 years; height = 1.8 ± 0.1 m; mass = 76.4 ± 8.3 kg) visited the laboratory on two separate days and completed a comprehensive task-specific warm-up followed by three v_slow or v_fast back squats at 70% of one-repetition maximum. Three CMJs were performed before and 30 s, 4 min, 8 min, and 12 min after the interventions. Jump height, peak power, kinetic energy, maximum knee angle, and knee angular velocities in both eccentric (downward) and concentric (upward) phases were recorded. Results: No significant (p > 0.05) between-condition differences were detected in any measure. Compared to pre-intervention, significant increases (collapsed data) were detected in jump height (6.0%; d = 0.68–0.83), power (3.6–6%; r = 0.32–0.38), and kinetic energy (5.0–8.0%; d = 0.62–0.86) at 30 s and 4 min. Conclusions: Given the lack of between-condition differences, the eccentric movement velocity of moderate conditioning back squats with maximal concentric velocity exercises does not appear to influence subsequent jump performance enhancements. Thus, either conditioning activity can be used to improve subsequent jump performance. However, as performance was enhanced only at 30 s and 4 min post-intervention, the window of opportunity is narrow, and timing should be carefully considered when including such activities in pre-competition routines. Full article

The closed kinetic chain is an essential movement method for humans in daily life, and is also important as a training method. However, there have been few studies focusing on the hip adductor muscles. We used electromyography to measure the muscle activity of the hip adductor muscles during walking and standing movements as part of daily living activities, as well as bicycle ergometer exercise and squats. Concerning the role of the adductor muscles, they are thought to stabilize the pelvis during the unilateral support phase when walking, and to act as hip extension and hip alignment adjustment during cycle ergometer exercise. By using electromyography and inertial sensors, the results of this study showed that wearable technologies can be used to quantify neuromuscular function during closed kinetic chain movements. The results serve as a reference for the development of rehabilitation devices, assistive technologies, and computational models that need the simulation of hip joint mechanics. Linking muscle activity data to engineering-based strategies enables precise musculoskeletal assessment and intervention beyond biological observation. Full article

Tibial torsion significantly influences knee biomechanics, yet its interaction with ACL reconstruction history in elite alpine skiers remains under-investigated. In this cross-sectional observational study, we analyzed 20 elite alpine skiers (7 ACL-reconstructed, 13 non-injured) using a markerless motion capture system during dynamic tasks (Squat, Single-Leg Squat, Lunge). Static tibial torsion was assessed via the Transmalleolar Axis and Thigh–Foot Angle. The results revealed a critical divergence in biomechanical strategies based on tibial alignment (p < 0.05). Skiers with rotational deformity adopted a pattern we describe as a “Stiffness Strategy”, characterized by suppressed knee valgus and hip rotation, but relied on excessive ankle dorsiflexion (39.5°)—a compensatory mechanism that may become limited when constrained by rigid ski boots. In contrast, ACL-reconstructed skiers with normal alignment exhibited what we term an “Instability Strategy”, showing dynamic valgus collapse and persistent asymmetry. These findings suggest that “one-size-fits-all” rehabilitation may be insufficient. We propose that injury prevention protocols may benefit from incorporating anatomical screening, focusing on decoupling mobility for skiers with tibial torsion and enhancing dynamic stability for those with normal alignment. Full article

Swallowing is a critical marker of neurological and emotional health. The ability to monitor it continuously and non-invasively, especially through smart ear-worn devices, holds significant promise for clinical applications. Despite this potential, no public audio datasets currently support reliable swallowing sound detection. Existing datasets focus primarily on speech and breathing, offering limited coverage and lacking detailed annotations for swallowing events. To address this gap, we introduce an in-ear audio dataset specifically designed to capture a wide range of verbal and non-verbal sounds. It includes comprehensive labeling focused on swallowing. The dataset was collected from 34 healthy adults (14 females and 20 males) between the ages of 20 and 29. Each participant performed a series of predefined tasks involving both non-verbal and verbal events. Non-verbal tasks included swallowing, clicking, forceful blinking, touching the scalp, and physical movements such as squatting or walking in place. Verbal tasks consisted of speaking (e.g., describing an image). Recordings were conducted in both quiet and noisy environments to better reflect real-world conditions. Data were captured using a combination of in-/outer-ear microphones, a chest belt to record electrocardiogram (ECG), respiration and acceleration signals, and an ultrasound probe to track tongue movement, which served as a reference for swallowing annotation. All signals were precisely synchronized. To ensure high data quality, the recordings were reviewed using both algorithmic analysis and manual inspection. Swallowing events were identified based on ultrasound signals and validated by an expert to guarantee accurate labeling. As a proof of concept that in-ear audio supports swallow classification, we fine-tune a fully connected neural network on YAMNet embeddings plus zero-crossing rate (ZCR) features. Across the completed folds, the model reaches an F1 score of 0.875 ± 0.013. Full article

Background/Objectives: Recent guidelines have emphasized the importance of early mobilization and rehabilitation of patients following cardiac surgery. However, studies on the optimal targets and prescription methods for phase I cardiac rehabilitation (CR) are lacking. This study aimed to evaluate the feasibility and utility of an early phase 1 submaximal cardiopulmonary exercise test (CPET) using a recumbent ergometer in patients who have undergone cardiac surgery. Methods: Twenty ambulatory patients who underwent cardiac surgery between December 2021 and February 2023 were referred to the CR department on the fifth postoperative day, and a CR program was initiated. The program was conducted five times a week, with hour-long sessions consisting of warm-up exercises, resistance training, aerobic exercises, and a cool-down period. A recumbent ergometer-based submaximal CPET was performed approximately nine days after the surgery, prior to discharge. Participants initiated the test at 0 W, and the workload was increased by 20 W after 2 min. During the test, researchers evaluated parameters including submaximal peak values of oxygen consumption (VO₂), metabolic equivalents of task, respiratory exchange ratio (RER), blood pressure, heart rate (HR), and rating of perceived exertion (RPE). The grip strength test, 6 min walk test (6MWT), Korean Activity Scale/Index (KASI), EuroQol-5 dimension (EQ-5D), and short-form 36-item health survey (SF-36) values were also measured prior to discharge. Results: Twenty patients (75% male, average age 62.50 ± 1.99 years) underwent CPET at a median of 9.0 (8.0; 12.5) days postoperative. The average exercise duration of the CPET was 411.75 ± 168.25 s. During the test, their submaximal peak VO₂ was 12.32 ± 0.75 mL/kg/min (corresponding to 46.65 ± 2.08% of VO₂ max). The submaximal peak RER was 1.01 (0.98–1.12), and the submaximal peak RPE was 15.00 ± 0.51. Furthermore, the submaximal peak HR was 111.8 ± 3.76 beats/min (equivalent to 70.95 ± 2.09% of age-predicted maximal HR). After adjustment for age and sex, statistically significant positive correlations were observed between the submaximal peak VO₂ and 6MWT, squat endurance test, KASI, EQ-5D, and the physical component summary (PCS) of the SF-36 questionnaire. The 6MWT, squat endurance test, KASI, and PCS of SF-36 showed a correlation coefficient (r) of 0.522 (p = 0.026), 0.628 (p = 0.005), 0.586 (p = 0.011), and 0.546 (p = 0.019), respectively. No significant cardiac events, such as ST elevation/depression or hemodynamic instability, were observed during the test. Conclusions: Our findings suggest that performing recumbent ergometer-based CPET during early phase 1 CR is safe and feasible. These results highlight the potential of recumbent ergometer-based CPET as a valuable tool for guiding the appropriate prescription of early CR programs following hospital discharge in patients undergoing cardiac surgery. 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

This study aims to investigate the gender differences in lower limb strength among Chinese national rugby team athletes, as well as the relationship between these variables. Twenty-seven athletes underwent countermovement jump (CMJ) and one-repetition maximum (1RM) squat tests, with relative strength calculated through bodyweight normalization. Results showed that male athletes had significantly higher CMJ height (p = 0.005) and absolute squat 1RM values (p < 0.001) compared to female athletes; male and female athletes showed significant differences in relative strength (p < 0.001). Correlation analysis indicated a positive relationship between CMJ height and absolute squat strength (p = 0.002), but no significant association with relative strength. The findings suggest a significant sex-based disparity in absolute lower limb strength among athletes of the Chinese national rugby team, with relative strength levels also exhibiting variations. When developing training programs, coaches and athletes should consider gender-specific differences in absolute strength. Full article