3-Dimensional Biomechanics of Noncontact Anterior Cruciate Ligament Injuries in Male Professional Soccer Players.

BACKGROUND: The understanding of noncontact anterior cruciate ligament (ACL) injury causation in soccer has improved over the past decades. Bidimensional video analyses have significantly augmented our awareness, representing to date the only practical method to describe injury biomechanics. However, the extent of the problem continues to raise serious concerns. PURPOSE: To advance our understanding of the causal pathways leading to ACL injury with a large-scale reconstruction of 3-dimensional (3D) whole-body joint kinematics of injuries that occurred to male elite soccer players, as well as to compare the joint angle time course among situational patterns. STUDY DESIGN: Descriptive laboratory study. METHODS: A total of 33 consecutive noncontact and indirect contact ACL injuries that occurred in 6 national and 2 international professional leagues (seasons 2020-2021 to 2022-2023 until December 2022) were analyzed: (1) multiview noncoaxial television images were inspected; (2) multiple camera views were taken from 400 ms before the initial ground contact to 200 ms after the injury frame; (3) a size-matched pitch was modeled and used to calibrate cameras; (4) a 3D skeletal model was adjusted to fit the player's pose in each frame/view; and (5) poses were interpolated, and Euler joint angles were extracted. RESULTS: The authors reconstructed the 3D lower limb joint kinematic curves preceding and during ACL injuries in 33 cases; notably, a sudden external (up to 5°) and then internal knee rotation was observed after the initial contact and before the injury frame. The overall kinematics at injury were knee moderately flexed (45.9°± 21.7°), abducted (4.3°± 5.1°), and externally rotated (3.0°± 6.4°); trunk shallowly flexed (17.4°± 12.5°) and rotated and tilted toward the injured side; and hip flexed (32.0°± 18.7°), abducted (31.1°± 12.0°), and slightly internally rotated (6.6°± 12.2°). Variable behaviors were observed at the ankle level. CONCLUSION: Via reconstruction of the sequence of whole-body joint motion leading to injury, we confirmed the accepted gross biomechanics (dynamic valgus trend). This study significantly enriches the current knowledge on multiplanar kinematic features (transverse and coronal plane rotations). Furthermore, it was shown that ACL injuries in male professional soccer players manifest through distinct biomechanical footprints related to the concurrent game situation. CLINICAL RELEVANCE: Interventions aimed at reducing ACL injuries in soccer should consider that environmental features (ie, situational patterns) affect injury mechanics.

Muscle activation while running on the ground compared to artificial turf in males with pronated and supinated feet.

BACKGROUND: Running on different surfaces, including natural and artificial surfaces, requires different gait mechanics, especially in individuals with foot deformity. RESEARCH QUESTION: How muscle activity change during running on the ground and artificial turf in males with pronated and supinated feet? METHODS: In this quasi-experimental study, we assessed a cohort of young male subjects, classified as healthy (n = 10), and with pronated (n = 10) or supinated (n = 10) feet. An electromyographic system was used to record lower limb muscle activity while running on the ground and artificial turf at constant speed (3.2 m/s). RESULTS: Results demonstrated significant main effects of the "surface" factor for vastus medialis activity during the loading phase (p = 0.040, η2 =0.147). Paired comparison revealed significantly greater vastus medialis activity while running on artificial grass with respect to the ground. A significant effect of the "group" factor was found for medial gastrocnemius during loading phase (p = 0.020, η2 =0.250). Paired-wise comparison revealed significantly lower medial gastrocnemius activity in the pronated and supinated feet groups than in the healthy group. SIGNIFICANCE: The healthy group may possess better neuromuscular control, allowing them to effectively coordinate the activation of the medial gastrocnemius with other muscles involved in running. Based on these findings, running on artificial turf is useful when the runner would like to strengthen vastus medialis muscle. The runner should carefully choose the running surface according to his/her state and training session goal.

Speed Effects on the Accuracy of Heart Rate as Oxygen-Uptake Indicator in Short-Distance Shuttle Running.

Purpose: Despite the accuracy of heart rate (HR) as an indicator of the aerobic engagement has been evaluated in several intermittent on-court activities, its validity as an oxygen uptake (V˙O2) indicator during shuttle running over short paths remains uncertain. Moreover, it is unclear whether speed may affect such validity. This study evaluated the HR ability in estimating the V˙O2 during 5-m shuttle running at different speeds. Methods: V˙O2 and HR of 12 physically active young men were recorded during an incremental forward running (FW) protocol and a 5-m shuttle test at 50%, 60%, and 75% of maximal aerobic speed (MAS). Slope and intercept of the relationship between HR and V˙O2 (HR/V˙O2) were individually determined, in both protocols. The HR measured during the shuttle test was used in the FW HR/V˙O2 to estimate V˙O2 at each shuttle speed. A paired Student's t-test compared slopes and intercepts of the two HR/V˙O2. A two-way RM-ANOVA and an equality test examined, respectively, the differences and the equality between measured and estimated V˙O2. Lastly, a Bland-Altman plot described the accuracy and precision of the estimated V˙O2 at each shuttle intensity. Results: Slopes and intercepts of the HR/V˙O2 appeared not different between FW and shuttle running. At 50%MAS, HR underestimated the V˙O2 (~7%), whereas returned accurate values at the two higher velocities, although with high variability (±18%). Conclusions: When using HR as V˙O2 indicator during shuttle running over short paths, a separated analysis of the HR validity as V˙O2 indicator is recommended especially when administering different exercise intensities.

Technical Differences over the Course of the Match: An Analysis of Three Elite Teams in the UEFA Champions League.

The purpose of this study was to evaluate the evolution of technical performance indicators over the course of football matches in the UEFA Champions League. Three elite football teams were the sample of the present study and were analyzed throughout four consecutive seasons within the previously mentioned competition. Data from 15 min periods were collected from Wyscout and elaborated. The effects of match location and competition stage were analyzed on nine technical indicators, including ball possession and variables related to offense and goal scoring. The effects of independent variables were assessed both independently and combined. The results showed a significant increase in the frequency of occurrence and accuracy of most of the parameters towards the end of the match. The effect of match location was generally significant with higher rates for teams playing at home. Differences were noted between the two stages of the competition with higher values in the technical indicators registered during the group stage. The existence of significant differences between the initial and final periods of football games was suggested by the results. The so-called home advantage was confirmed. Different team approaches between longer stages (e.g., group stage) and elimination games (i.e., knockout phase) were suggested by the results.

Associations Between Cognitive Function and ACL Injury-Related Biomechanics: A Systematic Review.

CONTEXT: Does lower baseline cognitive function predispose athletes to ACL injury risk, especially when performing unplanned or dual-task movements? OBJECTIVE: To evaluate the association between cognitive function and biomechanics related to ACL injuries during cognitively challenging sports movements. DATA SOURCES: PubMed (MEDLINE), Web of Science, Scopus, and SciELO databases were searched; additional hand searching was also conducted. STUDY SELECTION: The following inclusion criteria had to be met: participants completed (1) a neurocognitive test, (2) a cognitively challenging sport-related task involving lower limbs, and (3) a biomechanical analysis. The following criteria determined exclusion from the review: studies involving participants with (1) recent or current musculoskeletal injuries; (2) recent or current concussion; (3) ACL surgical reconstruction, reviews of the literature, commentary or opinion articles, and case studies. STUDY DESIGN: Systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocols (PRISMA-P) statement and registered at the International Prospective Register of Systematic Reviews (PROSPERO). LEVEL OF EVIDENCE: Level 3. DATA EXTRACTION: Two of authors independently extracted data and assessed the methodological quality of the articles with the Downs and Black and ROBINS-I checklists, to assess methodological quality and risk of bias, respectively. RESULTS: Six studies with different methodologies and confounding factors were included in this review. Of these 6 studies, 3 were ranked as high-quality, 3 demonstrated a low risk of bias, 2 a moderate risk, and 1 a severe risk. Five studies found a cognitive-motor relationship, with worse cognitive performance associated with increased injury risk, with 1 study reporting the opposite directionality for 1 variable. One study did not identify any interaction between cognitive function and biomechanical outcomes. CONCLUSION: Worse cognitive performance is associated with an increased injury risk profile during cognitively challenging movements.

Motion characteristics of Under-15, Under-17 and Under-19 Italian youth women soccer matches.

BACKGROUND: Despite the constant development of women's football, few studies to date addressed the physical requirements of youth female soccer players in regional (specific) contexts. This research characterized the activity profiles of élite Italian U15, U17 and U19 female games. METHODS: Sixty players (U15, N.=18; U17, N.=20; U19, N.=22) from a high-level club in North-East Italy were involved. Players were equipped with a 10-Hz GPS device. Forty-six games were monitored (9 vs. 9 for U15, 11 vs. 11 for U17-U19) and the following dependent variables were extracted: total distance, equivalent distance, normalized distance (m/min) in six speed and metabolic power ranges. Total high-speed (>14.1 km/h) and total high-power (>18 W) distances were computed based on thresholds parametrized to the young female athlete. A multivariate general linear model was fit to analyze the effect of age category, match periods and their interaction. RESULTS: Some game parameters increased with age, especially from U15 to U17. Among them: total distance (5.5 km, 7.8 km, and 8.8 km for U15, U17, U19), distance at very-high (18-22 km/h) and maximum (>22 km/h) speed, distance at high power (18-31.5 W). Normalized distance was ~90 m/min and comparable among age groups. A reduction of very-high (31.5-49.5 W) and maximum power (>49.5 W) distance was observed in U15 matches, and of high-power distance in U17 and U19. CONCLUSIONS: These findings quantify the physical demands of Italian youth female match-play. These data support evidence-based training planning, set a reference for players approaching higher playing standards, and could suggest informed redesign of playing formats.

Video analysis of Achilles tendon rupture in male professional football (soccer) players: injury mechanisms, patterns and biomechanics.

Background: Achilles tendon rupture (ATR), while rare in football, is a severe career-threatening injury associated with long-layoff times. To date, no study has documented ATR's mechanism in professional football players. Aim: To describe the mechanisms, situational patterns and gross biomechanics (kinematics) of ATR injuries in professional male football players. Methods: Eighty-six (n=86) consecutive ATR injuries in professional football players during official matches were identified. Sixty (70%) injury videos were identified for mechanism and situational pattern, with biomechanical analysis feasible in 42 cases. Three independent reviewers evaluated the injury videos. Distribution of ATR during the season, the match play and on the field were also reported. Results: Fifty (n=50, 83%) injuries were classified as non-contact and 10 (17%) as indirect contact. ATRs are injuries occurring during accelerations; three main situational patterns were identified: (1) forward acceleration from standing (n=25, 42%); (2) cross-over cutting (n=15, 25%) and (3) vertical jumping (n=11, 18%). Biomechanically, ATR injuries were consistent with a multiplanar loading at the injury frame consisting of a slightly flexed trunk (15.5°), extended hip (-19.5°), early flexed knee (22.5°) and end-range dorsiflexed (40°) ankle in the sagittal plane and foot pronation; 27 (45%) ATRs occurred in the first 30 min of effective match time. Conclusions: All ATRs in professional football were either non-contact (83%) or indirect contact (17%) injuries. The most common situational patterns were forward acceleration from standing, cross-over cutting and vertical jumping. Biomechanics was consistent and probably triggered by a multiplanar, although predominantly sagittal, loading of the injured Achilles tendon.

Foot dominance and ball approach angle affect whole-body instep kick kinematics in soccer players.

Past investigations provided limited information regarding instep kicking kinematics in soccer. It is unclear how foot dominance and ball approach angle impact whole-body kinematics and consequently the ball velocity. We aimed to analyse the effects of the ball approach angle and the foot used on the whole-body kinematics of soccer players performing an instep kick. Twenty-four soccer players performed maximal instep kicks, using the dominant and non-dominant feet, with the ball stationary or rolling from four different directions. Whole-body motion was recorded during the kicking action and kinematic time-series were extracted and resampled to 200 points equally divided into kicking and follow-through phases. 1-D statistical parametric mapping two-way ANOVA tested for the effect of ball condition and foot dominance. Ball approach angle affected most of the swinging and support limb variables and some upper body variables. Performance-related variables such as CoM, foot, and shank velocities were reduced when the ball approached posteriorly. The linear and angular velocities of the swinging limb, and CoM vertical position, were higher when kicking with dominant foot. Based on these findings, as a practical implication, coaches should vary ball approach angles and the foot used during kicking drills to improve technical effectiveness in various situations.

The three-dimensional reconstruction of an Achilles tendon rupture in a professional football player reveals a multiplanar injury mechanism.

Achilles tendon rupture (ATR) is a rare although very serious injury for football players; currently, studies on ATR in football are scant. This case report intends to firstly describe the situational pattern and three-dimensional mechanism of the ATR injury occurred to a professional football player during the last UEFA 2020 Championship. To reconstruct the full 3D joint kinematics throughout the injury action, the model-based image-matching technique was used. The key findings were: (i) ATR injury combined a sudden ankle dorsiflexion action with an internal plantarflexion moment while performing a crossover cut at high speed; (ii) a multi-planar loading occurred during the push-off phase.Level of evidence V.

Players at home: Physical activity and quality of life in 12-17 years-old football (soccer) players during the Covid-19 lockdown.

Background: Aggressive preventive actions were required to face the Covid-19 outbreak. However, from March 2020 on, many healthy youth football players have seen their sporting activities disrupted by the restrictions on outdoor exercise.This study describes physical activity and quality of life during April 2020 lockdown of young people participating in organized football. Methods: 1163 young football players aged 12-17 years (185 girls) completed a web-based questionnaire including the Youth Physical Activity and the Youth Quality of Life-Short Form Questionnaires; information on lifestyle and football-specific activity were also collected. Differences according to sex, urban/rural context and élite/non-élite club level were tested using a 2 × 2 × 2 MANOVA (age considered as a covariate). Results: We found that: (i) on average, exposure to football accounted for 3.2 hours/week, was higher in élite clubs and changed in nature, being mainly performed individually; 19% of participants practiced football <1 hour/week; (ii) only 56% of the participants reported 7 or more hours/week of moderate-to-vigorous physical activity, which decreased with age and changed according to the geographical context; (iii) perceived quality of life was lower in youth playing for non-elite clubs and in older girls; (iv) coaches, rather that official initiatives, were the primary source of football exercises practiced at home. Conclusion: A status of limited physical activity emerged; this might lead to deconditioning and susceptibility to injuries when football could restart. Governing bodies, football Associations and clubs could exploit these results to take informed decisions and support evidence-based interventions during and after the Covid-19 pandemic.

Lower limbs muscle activation during instep kick in soccer: effects of dominance and ball condition.

Muscle activation has been studied in soccer players kicking stationary balls with the dominant foot. This study evaluated swinging and support limb muscle activation during the instep kick using different feet and ball approach conditions.Vastus medialis (VM), biceps femoris (BF), gastrocnemius medialis (GM) and tibialis anterior (TA) activations were evaluated during maximal instep kicks with both feet and the ball in five conditions (n = 18): stationary (STAT), approaching anteriorly (ANT), posteriorly (POST), laterally (LAT) and medially (MED). A repeated-measures two-way ANOVA compared activations between feet and ball conditions throughout the kicking (0-100%) and follow-through phases (101-200%). Close to ball contact (81-124%), non-dominant support GM had greater activation than the dominant one. The LAT and MED conditions differed within the cycle in the swinging VM (0-21%; 191-200%), BF (13-70%; 121-161%), GM (22-82%; 121-143%) and TA (0-32%; 55-97%; 186-200%) and in support VM (0-81%), BF (6-24%; 121-161%) and GM (24-87%). Players require greater support GM activation to stabilize the ankle during non-dominant kicks. Muscle activation differences between LAT and MED indicate that the kicking strategies are altered when kicking balls approaching from different directions.

An osteometric and 3D analysis of the atlanto-occipital joint: An initial screening method to exclude crania and atlases in commingled remains.

OBJECTIVES: The anatomical features of the atlanto-occipital joint can be potentially useful in re-associating or excluding crania to atlases in commingled remains. This study investigated whether linear measurements and the 3-dimensional (3D) surface of occipital condyles and articular facets of atlases can represent valid insights for this purpose. METHODS: The variations among eight corresponding linear distances were analyzed in a sample of 150 individuals through six supervised machine learning techniques attempting to develop classifiers able to identify elements belonging to the same individual. Furthermore, a 3D analysis was conducted on the articular surfaces through superimpositions of 3D models of corresponding and non-corresponding crania and atlases obtained by using respectively stereophotogrammetry and laser scanning. This analysis investigated differences in terms of point-to-point distances (Root Mean Square, RMS) of superimposed 3D surfaces. RESULTS: None of the six machine learning techniques were able to correctly detect a satisfying percentage of correspondent pairs in the overall sample by using the linear variables. The 3D analysis of the articular surfaces found RMS values over 0.53 mm only for superimposed non-corresponding surfaces, which sets a threshold value to identify 32% of incorrect pairs. DISCUSSION: The re-association of cranium to atlas proved to be challenging and hardly possible when considering only metric variables. However, the 3D geometry of the articular surfaces represents a valid variable for this purpose and 3D analyses pave the way for an initial exclusion of incorrect re-associations, thus should not be considered as a re-association method per se, but as an exclusionary screening technique.

Whole-body kinematics during a simulated sprint in flat-water kayakers.

Success in sprint kayaking depends on the propulsive power generated by trunk, pelvis, shoulder and lower limb movements. However, no studies have examined whole-body kinematics over a simulated distance. We aimed to study the changes in movement patterns of kayakers performing a 500-m kayak sprint. Eleven young K1 sprint kayakers (three females; age: 16.5 ± 1.9 years, height: 174.1 ± 7.1 cm and weight: 66.1 ± 6.2 kg) performed an incremental test on a kayak ergometer to assess their Peak Oxygen Uptake (V̇O2peak). They then performed a 500-m sprint trial on the same ergometer, and the positions of 40 reflective markers were recorded to assess whole-body kinematics. Joint angles over time were computed for the trunk and right shoulder, hip, knee, and ankle. Changes of joint kinematics during the test were assessed with Statistical Parametric Mapping, calculating at each time node the linear regression between joint angles waveforms and the time of the rowing cycle, p < .05. Cardiometabolic responses confirmed that the participants achieved a maximal effort (V̇O2 and HR reached 99 ± 11% and 94 ± 6% of peak values, respectively). Paddle velocity negatively correlated with sprint time. The shoulder (elevation, rotation and flexion), trunk (lateral flexion and rotation) and hip (abduction) angles significantly changed over time in different phases of the stroke cycle during the simulated sprint. No significant differences over time were found for knee and ankle flexion. A high-intensity sprint may affect the shoulder, trunk and hip kinematics of kayak paddling. The kinematic analysis of kayakers' paddling during simulated metabolic-demanding tasks can provide useful insights to coaches and athletes.

Injury Burden in Professional European Football (Soccer): Systematic Review, Meta-Analysis, and Economic Considerations.

OBJECTIVE: We performed a systematic review and meta-analysis to evaluate the injury burden and the related economic cost in European professional male football players. DATA SOURCES: Multiple database research was performed up to August 5, 2022 (PubMed, EMbase, Scopus, Cochrane Library), including only studies that reported severity in the number of days of absence for each injury, incidence reported in the number of injuries/1000 hours, or reported number of injuries and exposure time and adult male football players, professionals from European clubs. Two reviewers extracted data and assessed paper quality with the Strengthening the Reporting of Observational Studies in Epidemiology statement and the Newcastle-Ottawa Scale. MAIN RESULTS: Twenty-two studies have reported incidence, severity, and burden of injuries in professional football. The highest injury burden was found for ligament-joint injuries (37.9 days/1000 hours; 222 397 €/1000 hours) and for muscle injuries (34.7 days/1000 hours; 203 620 €/1000 hours). Injury locations with high burden were knee injuries (34.8 days/1000 hours; 20 4206 €/1000 hours)-mainly anterior cruciate ligament injuries (14.4 days/1000 hours; 84 499 €/1000 h)-followed by thigh injuries (25.0 days/1000 hours; 146 700 €/1000 hours), hamstrings injuries (15.4 days/1000 hours; 90 367 €/1000 hours), hip-and-groin injuries (16.1 days/1000 hours; 94 475 €/1000 hours), primarily adductor muscles injuries (9.4 days/1000 hours; 55 159€/1000 hours), and ankle injuries (13.1 days/1000 h; 76 871 €/1000 hours) with ankle sprains (7.4 days/1000 hours; 43 423 €/1000 hours). CONCLUSIONS: Being exposed to injury risk has serious consequences for individual and club performance and economy. This review identified the most relevant targets in injury management, compared their injury data with reference values, and provided economic evidence when trying to gain buy-in from the key decision makers.

Kinematic patterns during walking in children: Application of principal component analysis.

The relative displacements of body segments during walking can be reduced to a small number of multi-joint kinematic patterns, pmk, through Principal Component Analysis (PCA). These patterns were extracted from two groups of children (n = 8, aged 6-9 years, 4 males, and n = 8, aged 10-13 years, 4 males) and 7 adults (21-29 years, 1 male), walking on a treadmill at various velocities, normalized to body stature (adimensional Froude number, Fr). The three-dimensional coordinates of body markers were captured by an optoelectronic system. Five components (pm1 to pm5) explained 99.1% of the original dataset variance. The relationship between the variance explained ("size") of each pmk and the Fr velocity varied across movement components and age groups. Only pm1 and pm2, which described kinematic patterns in the sagittal plane, showed significant differences (at p < 0.05) across pairs of age groups. The time course of the size of all the five components matched various mechanical events of the step cycle at the level of both body system and lower limb joints. Such movement components appeared clinically interpretable and lend themselves as potential markers of neural development of walking.

Machine Learning-Based Estimation of Ground Reaction Forces and Knee Joint Kinetics from Inertial Sensors While Performing a Vertical Drop Jump.

Nowadays, the use of wearable inertial-based systems together with machine learning methods opens new pathways to assess athletes' performance. In this paper, we developed a neural network-based approach for the estimation of the Ground Reaction Forces (GRFs) and the three-dimensional knee joint moments during the first landing phase of the Vertical Drop Jump. Data were simultaneously recorded from three commercial inertial units and an optoelectronic system during the execution of 112 jumps performed by 11 healthy participants. Data were processed and sorted to obtain a time-matched dataset, and a non-linear autoregressive with external input neural network was implemented in Matlab. The network was trained through a train-test split technique, and performance was evaluated in terms of Root Mean Square Error (RMSE). The network was able to estimate the time course of GRFs and joint moments with a mean RMSE of 0.02 N/kg and 0.04 N·m/kg, respectively. Despite the comparatively restricted data set and slight boundary errors, the results supported the use of the developed method to estimate joint kinetics, opening a new perspective for the development of an in-field analysis method.

Validation and Reliability of a Novel Vagus Nerve Neurodynamic Test and Its Effects on Heart Rate in Healthy Subjects: Little Differences Between Sexes.

BACKGROUND: The vagus nerve (VN), also called the pneumogastric nerve, connects the brainstem to organs contained in the chest and abdomen. Physiologically, VN stimulation can rapidly affect cardiac activity and heart rate (HR). VN neuropathy can increase the risk of arrhythmias and sudden death. Therefore, a selective test of VN function may be very useful. Since peripheral neurodynamic tests (NDT) are reliable for the assessment of neuropathies in somatic nerves, we aimed to validate a novel NDT to assess VN activity, namely, the VN-NTD. METHODS: In this cross-sectional double-blind, sex-balanced study, 30 participants (15 females) completed a checklist of autonomic dysfunction symptoms. During the VN-NDT administration, HR and symptoms (i.e., mechanical allodynia) were monitored in parallel to a real-time ultrasonography imaging (USI) and motion capture analysis of the neck. The VN-NDT impact on HR and its accuracy for autonomic symptoms reported in the last 7 days were tested. RESULTS: The VN-NDT induced a significant HR reduction of about 12 and 8 bpm in males and females [t(1, 119) = 2.425; p < 0.017; ηp 2 = 0.047, 95% confidence interval (CI): 0.93-9.18], respectively. No adverse events were observed during VN-NDT. A substantial interexaminer agreement between the evaluators in symptoms induction by VN-NDT was detected [F(1, 119) = 0.540; p = 0.464; ηp 2 = 0.005, low effect]. Notably, mechanical allodynia accuracy for gastrointestinal dysfunctions was excellent (p < 0.05; 95% CI: 0.52-0.73; p < 0.001; 95% CI: 0.81-0.96). CONCLUSIONS: The novel VN-NDT is a valid and accurate test capable of detecting VN activation with high sensitivity. Data provided are suitable for both sexes as a hallmark of HR variation due to VN normal response. The proposed VN-NDT may be reliable as daily routine neurological examination tests for the evaluation of neuropathic signs related to neuroinflammation of the VN. CLINICAL TRIAL REGISTRATION: www.ClinicalTrials.gov, identifier NCT04192877.

Spatiotemporal gait parameter changes due to exposure to vertical whole-body vibration.

BACKGROUND: Vertical whole-body vibration (vWBV) during work, recreation, and transportation can have detrimental effects on physical and mental health. Studies have shown that lateral vibration at low frequencies (<3 Hz) can result in changes to spatiotemporal gait parameters. There are few studies which explore spatiotemporal gait changes due to vertical vibration at higher frequencies (> 3 Hz). This study seeks to assess the effect of vWBV on spatiotemporal gait parameters at a greater range of frequencies (≤ 30 Hz). METHODS: Stride Frequency (SF), Stride Length (SL), and Center of Pressure velocity (CoPv) was measured in seven male subjects (23 ± 4 years, 1.79 ± 0.05 m, 73.9 ± 9.7 kg) during In-Place Walking and nine male subjects (29 ± 7 years, 1.78 ± 0.07 m, 77.8 ± 9.9 kg; mean ± SD) during Treadmill Walking while exposed to vWBV. Load cells measured ground reaction forces during In-Place Walking and sensorized insoles acquired under-foot pressure during Treadmill Walking. Statistical tests included a one-way repeated-measures ANOVA, post-hoc two way paired T-tests, statistical power (1-ß), correlation (R2), and effect size (Cohen's d). RESULTS: While statistical significance was not found for changes in SF, SL, or Mean CoPv, small to large effects were found in all measured spatiotemporal parameters of both setups. During Treadmill Walking, vWBV was correlated with a decrease in SF (R2 = 0.925), an increase in SL (R2 = 0.908), and an increase in Mean CoPv (R2 = 0.921) and Max CoPv (R2 = 0.952) with a significant increase (p < 0.0083) in Max CoPv at frequencies of 8 Hz and higher. SIGNIFICANCE: Study results demonstrated that vWBV influences spatiotemporal gait parameters at frequencies greater than previously studied.

Fatigue Induced by Repeated Changes of Direction in Élite Female Football (Soccer) Players: Impact on Lower Limb Biomechanics and Implications for ACL Injury Prevention.

BACKGROUND: The etiology of Anterior Cruciate Ligament (ACL) injury in women football results from the interaction of several extrinsic and intrinsic risk factors. Extrinsic factors change dynamically, also due to fatigue. However, existing biomechanical findings concerning the impact of fatigue on the risk of ACL injuries remains inconsistent. We hypothesized that fatigue induced by acute workload in short and intense game periods, might in either of two ways: by pushing lower limbs mechanics toward a pattern close to injury mechanism, or alternatively by inducing opposed protective compensatory adjustments. AIM: In this study, we aimed at assessing the extent to which fatigue impact on joints kinematics and kinetics while performing repeated changes of direction (CoDs) in the light of the ACL risk factors. METHODS: This was an observational, cross-sectional associative study. Twenty female players (age: 20-31 years, 1st-2nd Italian division) performed a continuous shuttle run test (5-m) involving repeated 180°-CoDs until exhaustion. During the whole test, 3D kinematics and ground reaction forces were used to compute lower limb joints angles and internal moments. Measures of exercise internal load were: peak post-exercise blood lactate concentration, heart rate (HR) and perceived exertion. Continuous linear correlations between kinematics/kinetics waveforms (during the ground contact phase of the pivoting limb) and the number of consecutive CoD were computed during the exercise using a Statistical Parametric Mapping (SPM) approach. RESULTS: The test lasted 153 ± 72 s, with a rate of 14 ± 2 CoDs/min. Participants reached 95% of maximum HR and a peak lactate concentration of 11.2 ± 2.8 mmol/L. Exercise duration was inversely related to lactate concentration (r = -0.517, p < 0.01), while neither%HR max nor [La-] b nor RPE were correlated with test duration before exhaustion (p > 0.05). Alterations in lower limb kinematics were found in 100%, and in lower limb kinetics in 85% of the players. The most common kinematic pattern was a concurrent progressive reduction in hip and knee flexion angle at initial contact (10 players); 5 of them also showed a significantly more adducted hip. Knee extension moment decreased in 8, knee valgus moment increased in 5 players. A subset of participants showed a drift of pivoting limb kinematics that matches the known ACL injury mechanism; other players displayed less definite or even opposed behaviors. DISCUSSION: Players exhibited different strategies to cope with repeated CoDs, ranging from protective to potentially dangerous behaviors. While the latter was not a univocal effect, it reinforces the importance of individual biomechanical assessment when coping with fatigue.