Eccentric Phase Research Articles

Impact of a 20-Week Resistance Training Program on the Force–Velocity Profile in Novice Lifters Using Isokinetic Two-Point Testing

Objectives: This study aimed to assess the impact of a 20-week resistance training program on force–velocity (F-V) parameters using an isokinetic two-point method and comparing one-repetition maximum (1-RM) methods in novice lifters. Methods: Previously untrained individuals completed a supervised, three-session weekly resistance training program involving concentric, eccentric, and isometric phases, repeated every 2 to 4 weeks. Isokinetic dynamometry measured the strength of elbow flexors/extensors at 60°/s and 150°/s, and knee flexors/extensors at 60°/s and 240°/s at Baseline, 3 months, and 5 months. F-V parameters, including maximal theoretical force (F0) and the F-V slope, were calculated. Participants also performed 1-RM tests for the upper and lower limbs. Repeated measures ANOVA with effect size (η2 > 0.14 as large) was used to analyze changes in F-V parameters and repeated measures correlation was used to test their association with 1-RM outcomes. Results: Eighteen male participants (22.0 ± 3.4 years) were analyzed. F0 significantly increased for all muscle groups (η2 = 0.423 to 0.883) except elbow flexors. F-V slope significantly decreased (steeper) for knee extensors and flexors (η2 = 0.348 to 0.695). Knee extensors showed greater F0 gains and steeper F-V slopes than flexors (η2 = 0.398 to 0.686). F0 gains were associated with 1-RM changes (r = 0.38 to 0.83), while F-V slope changes correlated only with lower limb 1-RM (r = −0.37 to −0.68). Conclusions: The 20-week resistance training program significantly increased F0 and shifted the F-V profile towards a more “force-oriented” state in knee muscles. These changes correlated with improved 1-RM performance. Future studies should include longer follow-ups and control groups.

Change-of-Direction Performance and Its Deficits in Relation to Countermovement-Jump Height and Phase-Specific Performance Among Female Athletes.

Jump and linear sprint performances both correlate with pro-agility performance. However, correlation does not imply causation, and potential confounders may affect the correlation. Therefore, this study aimed to determine the relationship between change-of-direction (COD) performance and COD deficits (COD-D) in linear-sprint and countermovement-jump (CMJ)-related performance using multiple stepwise linear-regression models. The study included 42 female national-level intercollegiate athletes. The 10- and 20-m linear-sprint and pro-agility times, COD-D, CMJ height, and phase-specific force production and rate of force development during eccentric unloading, eccentric braking, and the concentric phases of CMJ were measured. Stepwise linear-regression analyses were used to predict the factors related to COD and COD-D. CMJ height was the sole predictor in the 10-m pro-agility model (adjusted R2 = .234, P = .001). Modified Reactive Strength Index (standardized coefficient, -.710) and the lowest center-of-mass depth during the CMJ (standardized coefficient, .323) were predictors in the 20-m pro-agility model (adjusted R2 = .330, P < .001). For the 10- and 20-m COD-D models, the rate of force development at 30 and 60milliseconds, respectively, during the concentric phase was the only predictor of performance (adjusted R2 = .183, P = .003 and .237, P = .001, respectively). These results suggest that athletes should concentrate on improving their CMJ height, increasing their ability to lower their center of mass more deeply, and increasing their instantaneous force-production abilities immediately after the eccentric braking phase of CMJ to improve their COD performance.

The Influence of Eccentric Muscle Actions on Concentric Muscle Strength: An Exception to the Principle of Specificity?

The principle of specificity suggests that the largest changes in strength occur when training resembles the specific strength test. A one-repetition maximum (1RM) test, which tests the maximal concentric strength, is commonly used as a surrogate for strength adaptation. When separating muscle actions into concentric or eccentric phases, multiple lines of evidence suggest that eccentric muscle actions possess several distinct physiological properties compared with concentric actions. In accordance, there are instances where the increases in 1RM strength test were similar between eccentric-only and concentric-only resistance training. This is at odds with the principle of specificity which suggests that individuals who trained with concentric actions would be expected to have an advantage in that specific task. Although the mechanistic reasons why eccentric-biased training carries over to maximal concentric strength remains to be elucidated, the lack of discernible differences in strength gains with eccentrically-biased training (e.g., eccentric-only and accentuated eccentric training) may imply that the effects of eccentric loading in training are transferable to concentric strength. Our review revisits the role of eccentric loading in enhancing concentric maximal muscle strength. We also speculate on potential physiological factors (i.e., molecular and neural factors) that may differentiate the effects of eccentric and concentric resistance training on the changes in muscle strength. Currently, the majority of the studies investigating the changes in strength have been conducted using isokinetic eccentric training. This is important as there is a viewpoint that the magnitude of chronic adaptations with different modalities of eccentric exercises (i.e., isotonic, isokinetic, and isoinertial training) may also differ from each other. While it has been suggested that eccentric action has a greater transferable capacity for strength adaptations compared to concentric actions, future investigations are warranted to investigate with different modalities of eccentric exercises. There also remains a host of unanswered questions related to the role of eccentric action for maximal concentric strength. For example, future studies may examine whether the eccentric action would be additive when the training is already maximally loaded during the concentric action for increasing concentric maximal strength. We suggested a few different designs that could be used to answer some of these questions in future studies.

Effects of 6-Week Weighted-Jump-Squat Training With and Without Eccentric Load Reduction on Explosive Performance.

To compare the effects of 6-week barbell weighted-jump-squat (WJS) training with and without eccentric load reduction on explosive performance. Twenty well-trained male athletes were randomly assigned to either an experimental group (n = 10) or a control group (n = 10). Participants completed 12 WJS training sessions (6 sets of 5 repetitions of barbell back squat at 30% of 1-repetition maximum[1RM]) twice a week over a 6-week period. While thecontrol group used 0% eccentric loading (ie,traditional WJS), theexperimental group utilized a 50% eccentric loading reduction with a mechanical braking unit (ie,eccentric load set at 15% of 1RM). Performance assessments, including countermovement jump, 20-m sprint, standing long jump, and 1RM barbell back squat, were conducted both before (pretests) and after (posttests) the intervention. Both theexperimental group and thecontrol group demonstrated a significant increase in countermovement-jump height (+6.4% [4.0%] vs +4.9% [5.7%]; P < .001) and peak power output (+2.3% [2.7%] vs +1.9% [5.1%]; P = .017), faster 20-m sprint times (+9.4% [4.8%] vs +9.2% [5.5%]; P < .001), longer standing long jump (+3.1% [2.5%] vs +3.0% [3.3%]; P < .001), and higher 1RM back squat (+6.4% [4.0%] vs +4.9% [5.7%]; P < .001) from pretests to posttests. However, there was no significant condition × time interaction for any variable (all P ≥ .294). Both WJS training methods, with and without load reduction in the eccentric phase, effectively enhance explosive performance. Nevertheless, athletes in later stages of injury rehabilitation or intense training may find reducing eccentric load a more tolerable strategy for achieving similar performance gains compared with traditional isoinertial loading.

Residual Performance and Biomechanical Asymmetries During Jumping Tasks in Female Athletes at 9 Months After Anterior Cruciate Ligament Reconstruction.

Biomechanics and anterior cruciate ligament injury mechanisms differ in males and females. There is a need for more data on between-limb biomechanical differences after anterior cruciate ligament reconstruction (ACLR) in females. To explore biomechanical asymmetries throughout the kinetic chain during the single-legged (SL) and double-legged (DL) countermovement jump (CMJ) and drop jump (DJ) in female athletes after ACLR. Descriptive laboratory study. Kinematic and kinetic between-limb differences were analyzed during the SL and DL CMJ and DJ in 67 female athletes 9 months after ACLR. Biomechanical and performance asymmetries between limbs during the jumps and isokinetic strength testing were analyzed with statistical parametric mapping. The entire stance phase was used for the paired t tests of the biomechanical variables, with Cohen d effect sizes of significant portions of the stance phase (reported as % of stance) calculated in a point-by-point manner. Decreased vertical ground-reaction force, internal knee abduction moment, knee internal rotation angle, hip external rotation angle, internal ankle eversion, and external rotation moments were seen in the ACLR limb during all 4 vertical jump tests. The greatest number and highest value of differences were found during the DLDJ, with asymmetries having medium to large effect sizes. They tended to appear more frequently in the concentric phase (50% to 100% of stance) during the SLCMJ and DLCMJ and in the eccentric (0% to 49% of stance) and concentric (50% to 100% of stance) phase during the SLDJ and DLDJ. For the SLCMJ, SLDJ, and quadriceps strength, performance asymmetries of >15% were detected but not for change of direction. The findings suggest that return-to-play testing in female athletes should examine the entire stance phase and include assessments of kinetic and kinematic variables throughout the kinetic chain. Greater deficits were highlighted in the DJ than in the CMJ, and greater performance asymmetries were evident in the SL tasks, with greater kinetic and kinematic and compensatory strategies evident in the DL tests. Biomechanical analysis focusing on contralateral compensation strategies and sex-specific interventions are necessary before return to play.

Test–Retest Reliability of Concentric and Eccentric Muscle Strength in Knee Flexion–Extension Controlled by Functional Electromechanical Dynamometry in Female Soccer

In the field of sports performance, sports medicine, and physical rehabilitation, there is a great interest in the development of protocols and reliable techniques and instruments for the evaluation of strength produced by athletes. In the last ten years, women’s football has increased its popularity and participation in numerous countries, which has contributed to players developing more professionally and requiring more specific muscle strength training to improve their performance. The aim of this study was to analyze the absolute and relative test–retest reliabilities of peak muscle strength in knee flexion (FLE) and extension (EXT) controlled using a functional electromechanical dynamometer (FEMD) in a group of seventeen professional female soccer players (age = 18.64 ± 0.62 years; weight = 54.72 ± 7.03 kg; height = 1.58 ± 0.04 m; BMI = 21.62 ± 2.70 kg/m2). Peak muscle strength was measured with knee flexion (FLE) and extension (EXT) movements at a speed of 0.4 m·s−1 unilaterally in a concentric phase (CON) and an eccentric phase (ECC). No significant mean differences were found in the test–retest analysis (p &gt; 0.05; effect size &lt; 0.14), and high reliability was reported for peak muscle strength assessments in both the CON (ICC) = 0.90–0.95) and the ECC (ICC = 0.85–0.97). Furthermore, stable repeatability was presented for extension in the CON (CV = 7.39–9.91%) and ECC (CV = 8.65–13.64). The main findings of this study show that peak muscle strength in knee flexion and extension in CON and ECC is a measure with acceptable absolute reliability and extremely high relative reliability using the FEMD in professional female soccer players.

Investigating patellar motion using weight-bearing dynamic CT: normative values and morphological considerations for healthy volunteers

BackgroundPatellar instability is a well-known pathology in which kinematics can be investigated using metrics such as tibial tuberosity tracheal groove (TTTG), the bisect offset (BO), and the lateral patellar tilt (LPT). We used dynamic computed tomography (CT) to investigate the patellar motion of healthy subjects in weight-bearing conditions to provide normative values for TTTG, BO, and LPT, as well as to define whether BO and LPT are affected by the morphology of the trochlear groove.MethodsDynamic scanning was used to acquire images during weight-bearing in 21 adult healthy volunteers. TTTG, BO, and LPT metrics were computed between 0° and 30° of knee flexion. Sulcus angle, sulcus depth, and lateral trochlear inclination were calculated and used with the TTTG for simple linear regression models.ResultsAll metrics gradually decreased during eccentric movement (TTTG, -6.9 mm; BO, -12.6%; LPT, -4.3°). No significant differences were observed between eccentric and concentric phases at any flexion angle for all metrics. Linear regression between kinematic metrics towards full extension showed a moderate fit between BO and TTTG (R2 0.60, β 1.75) and BO and LPT (R2 0.59, β 1.49), and a low fit between TTTG and LPT (R2 0.38, β 0.53). A high impact of the TTTG distance over BO was shown in male participants (R2 0.71, β 1.89) and patella alta individuals (R2 0.55, β 1.91).ConclusionWe provided preliminary normative values of three common metrics during weight-bearing dynamic CT and showed the substantial impact of lateralisation of the patella tendon over patella displacement.Relevance statementThese normative values can be used by clinicians when evaluating knee patients using TTTG, BO, and LPT metrics. The lateralisation of the patellar tendon in subjects with patella alta or in males significantly impacts the lateral displacement of the patella.Key PointsTrochlear groove morphology had no substantial impact on motion prediction.The lateralisation of the patellar tendon seems a strong predictor of lateral displacement of the patella in male participants.Participants with patella alta displayed a strong fit between the patellar lateral displacement and tilt.TTTG, BO, and LPT decreased during concentric movement.Concentric and eccentric phases did not show differences for all metrics.Graphical

Assessing lower extremity stiffness in countermovement jumps: a critical analysis of the differences between calculation methods

ABSTRACT Introduction: Stiffness (k) describes a material’s resistance to deformation and is useful for understanding neuromuscular function, performance, and injury risk. The aim of this study is to compare the lower limb stiffness method (k LLS ), which uses only force plate data, with methods combining force plate and motion capture data to calculate stiffness during the eccentric phase of a countermovement. Material and Methods: Twelve resistance-trained males: age 24.9 (4.4) years, height 1.81 (0.05) m, weight 88.2 (14) kg) performed three maximal effort countermovement jumps (CMJ). Data were collected synchronously using three-dimensional (3D) kinematic and kinetic data (dual force plate setup). Lower limb stiffness (z), joint stiffness (x, y, and z), and leg stiffness (linear, sagittal plane, and 3D) were calculated for the eccentric phase of all CMs. Results: k LLS showed high concurrent validity with strong correlations to kinetic-kinematic methods (r = 0.90-0.97, p < 0.05). A linear mixed model revealed no significant differences in k-values between k LLS and leg stiffness, indicating high concurrent validity. Discussion: k LLS offers valid and valuable information affecting performance, injury risk, and return-to-sport decisions. Conclusion: The findings suggest that k LLS is a valid method for calculating stiffness in CMJs and equal to 3D leg stiffness.

Are there differences in the kinetic parameters of the vertical jump performed by beach volleyball players on different types of sand?

Beach volleyball (BV) is an intermittent sport characterised by short-duration and highly demanding activities with low intensity periods. Establishing if players' jump ability is influenced by sand granulometry is a useful information for sport scientists, coaches and players. This study aimed to assess the possible differences in the kinetics parameters of the vertical jump on different types of sand performed by BV players. Twelve elite female players performed six countermovement jumps (CMJs) in three different surface conditions (fine sand, reference, coarse sand) in a random counterbalanced order (216 jumps). A generalised mixed model approach detected differences for CMJ model in total duration (p: 0.016), eccentric phase duration (p: 0.007), concentric phase duration (p: 0.011), time to peak power (p: < 0.001), time to peak force (p: 0.014), maximum rate force development concentric phase (p: 0.004), maximum velocity (p: 0.028) and peak power eccentric (p: 0.018). Coarse sand decreases the time spent jumping compared to fine sand, without a penalty to jump height. Coaches and athletes should take this information into account to enhance their understanding of practice strategies and game conditions. One might anticipate a faster pace in games played on coarse sand and a slower pace on fine sand.

Effect of Different Breathing Patterns on Heart Rate and Blood Pressure Response to Resisted Exercises in Females Within the Age Group of 25 to 35 Years

Introduction: Blood pressure and heart rate increases in individuals while performing heavy resisted exercises but acquiring different breathing patterns during exercise shows its effect on blood pressure and heart rate, it may or may not exaggerate. Inhalation or exhalation when coupled with concentric phase of resisted exercise may or may not show similar blood pressure response as compare to inhalation or exhalation when coupled with eccentric phase of resisted exercise whereas Valsalva maneuver can exaggerate the blood pressure response. Objective: To study the inhalation, exhalation and Valsalva maneuver on systolic, diastolic blood pressure and heart rate. Research Design: Quasi experimental. Methodology: 30 female subjects were taken which were asked to do a set of bicep curls with 3 different patterns of breathing with each pattern performed on a separate day. Then the recordings were taken and calculated to see in which pattern of breathing blood pressure and heart rate rises. Result: ANOVA was used and the result showed that diastolic blood pressure increases while exhalation coupled with the concentric phase and inhalation coupled with the eccentric Phase but there is a marked increase in diastolic blood pressure during Valsalva maneuver as compared to the inhalation coupled with the concentric phase and exhalation coupled with the eccentric phase. The result showed that the change in the blood pressure due to the different breathing patterns were significant p&gt;0.05 Conclusion: It is concluded that Valsalva maneuver exaggerates the blood pressure response. Keywords: resisted exercises, Valsalva maneuver, exhalation. breathing patterns.

Does the short-term learning effect impact vertical jump performance assessment on a portable force plate system?

One of the reoccurring questions that arises during the countermovement vertical jump (CVJ) assessment is whether the learning effect has an impact on the accuracy of the results obtained. Thus, the purpose of the present investigation was to examine the impact of the short-term learning effect on the assessment of lower-body neuromuscular performance characteristics when performed on a portable one-dimensional force plate system. Sixteen recreationally active college-age males volunteered to participate in the present study. Each participant completed four sets of three non-consecutive CVJs with no arm swing throughout a single day. Besides strong verbal encouragement, participants were constantly instructed to focus on pushing the ground as explosively as possible. Fourteen force-time metrics were selected for CVJ performance analysis purposes: eccentric and concentric peak and mean force and power, eccentric and concentric duration, contraction time, jump height, reactive strength index-modified, and countermovement depth. Repeated measures multivariate analysis of variance was used to examine statistically significant differences across four testing time points (p < 0.05). The results indicate an absence of any meaningful differences across four testing time points in force-time metrics of interest during both eccentric and concentric phases of the CVJ. Moreover, no differences were observed in CVJ outcome metrics such as countermovement depth, suggesting that the movement strategy tends to remain consistent. Overall, these findings reveal that CVJ test repeatability is not affected by the short-term learning effect and that data are stable at least within the scope of this study and within this population.

Increased force and elastic energy storage are not the mechanisms that improve jump performance with accentuated eccentric loading during a constrained vertical jump.

Accentuated eccentric loading (AEL) involves higher load applied during the eccentric phase of a stretch-shortening cycle movement, followed by a sudden removal of load before the concentric phase. Previous studies suggest that AEL enhances human countermovement jump performance, however the mechanism is not fully understood. Here we explore whether isolating additional load during the countermovement is sufficient to increase ground reaction force, and hence elastic energy stored, at the start of the upward movement and whether this leads to increased jump height or power generation. We conducted a trunk-constrained vertical jump test on a custom-built device to isolate the effect of additional load while controlling for effects of squat depth, arm swing, and coordination. Twelve healthy, recreationally active adults (7 males, 5 females) performed maximal jumps without AEL, followed by randomised AEL conditions prescribed as a percentage of body mass (10%, 20%, and 30%), before repeating jumps without AEL. No significant changes in vertical ground reaction force at the turning point were observed. High load AEL conditions (20% and 30% body weight) led to slight reductions in jump height, primarily due to decreased hip joint and centre of mass work. AEL conditions did not alter peak or integrated activation levels of the knee extensor muscles. The constrained movement task used here, which excluded potential contributions of trunk motion, arm swing, rate of descent, squat depth, and point of load application, allows the conclusion that increased elastic energy return is not the primary mechanism for potentiating effects of AEL on jump performance.

The effect of resistance training focused on eccentric phase and interval exercises in young football players

The cardiovascular system, strength, speed, and agility are essential for a football player to perform better. For this purpose, finding the best and shortest way has always been a challenge. Therefore, this study aims to examine the effect of resistance training focused on eccentric phase and interval exercises on strength, agility, speed, and cardio strength in young football players.40 young football players are divided into two groups. The control group (CG) received only typical football exercises (by their coach), and the experimental group (EG) experienced eccentric exercises combined with interval aerobic training. To measure strength, agility, speed, and cardio strength, the Squat test, T-test, 60-meter sprint, and Cooper test were performed, respectively. To compare pre and post-test, paired sample t-test was utilized, and compare the two groups ANCOVA and Quade Nonparametric Analysis of Covariance test were used. The paired sample t-test showed a significant difference between pre and post-test in strength and cardiac strength in both groups. However, no significant difference was observed in speed and agility in CG. However, in EG, there was a significant difference between the pre and post-test in speed and agility variables. Also, according to the ANCOVA and Quade Nonparametric ANCOVA results, there was a significant difference between CG and EG in all variables. Eccentric and interval aerobic training could be more effective than typical football exercises on strength, cardio, speed, and agility. Football players can use the present program training to improve the essential physical factors. Keywords: Strength, Agility, Sprint, Male.

Relationship between Countermovement Jump and Sprint Performance in Professional Football Players.

Objectives: The aim of this study was to assess the relationship between the countermovement jump (CMJ) and sprint performance of professional football players, and to determine which strength and speed elements assessed by the CMJ translate into effective running. Methods: The research sample comprised 87 male professional football players (age 23.7 ± 4.20 years; body mass 82.33 ± 6.56 kg; body height 1.86 ± 0.05 m) who performed the CMJ on a dual-force platform, as well as the 30 m sprint test. The time and velocity of the run were recorded by photocells at 0, 5, 10, and 30 m of the distance. Results: No significant differences were noted in the time or velocity of the sprint over the initial 5 m between the groups of football players with a higher and lower braking rate of force development (RFD) in the CMJ (p > 0.05). However, at subsequent intervals (5-10 m and 10-30 m), players with a higher braking RFD achieved significantly better time and velocity than those with a lower RFD. Significant correlations in the group with a lower braking RFD between the CMJ and sprint variables occurred in the propulsion phase of the CMJ and most of them were in the first interval (0-5 m). In the group with a higher braking RFD, significant relationships were visible in both the propulsion (concentric) and braking (eccentric) phases of the CMJ, mainly during the second and third intervals of the sprint test. Conclusions: The noted observations may suggest that the relationship between strength and running performance is more complex than previously indicated, and that higher strength in the CMJ does not fully correlate with better sprinting. Therefore, it has been hypothesized that training aimed at generally increasing strength may not always be fully beneficial for running performance in football players and hence specific training guidelines are suggested for targeted strengthening of the required muscle performance characteristics. This may possibly contribute to reducing the unnecessary muscle overload during both training and matches, thereby preventing sports-related injuries.

Force–velocity–power profiling in flywheel squats: Differences between sports and association with countermovement jump and change of direction performance

ABSTRACT The objectives of our study were 1) to examine whether the force-velocity-power (FvP) outcomes in the concentric and eccentric phases of flywheel (FW) squats differ among sports disciplines and 2) to investigate the association between FvP outcome variables and two key sport-performance indicators: countermovement jump height (CMJ) and change of direction (CoD) time involving 90° or 180° turns. Tests were performed by 469 athletes from five different sport disciplines and physical education students. Our results showed that FvP outcomes, when measured during the eccentric phase of the FW squat, effectively differed between athletes from different sports. However, during the concentric phase of the squat, only for the slope variable differences between sports were found. Contrary to our hypothesis, there were no statistically significant correlations between FW squat FvP outcomes and CMJ or CoD test results. These results suggest that FvP outcomes derived from FW squats may lack external validity and cannot be reliably used as a predictor of athletes’ jumping and agility performance. The paper discusses possible reasons for the larger differences between sports in eccentric FvP outcomes, as well as the absence of correlations between FvP outcomes and functional tests.

Relationships between sprint skating performance and insole plantar forces in national-level hockey athletes

BackgroundSprint skating is essential for competitive success in hockey. Previous studies have highlighted various measures of lower-body strength and power as key factors influencing sprint performance. However, while these studies have indicated a significant association between the ability to exert greater force and impulse into the ice surface, and the capacity to achieve faster sprint skating speeds, the direct relationship between these factors remains largely inferred. Research questionWhat are the relationships between insole plantar force variables, sprint skating performance, and their association with physical capacity measures, in national-level male hockey athletes? MethodsAthletes (n=13) performed 25 m sprint skating trials with insole force sensors and completed: ankle dorsiflexion and hip abduction range-of-motion (ROM), countermovement jump (CMJ), seated single-leg jump, and 10–5 repeated-hop test (RHT) assessments. ResultsRelationships were assessed using Kendall’s Tau rank correlations (τ), with significant relationships identified between mean relative weight acceptance impulse [WAI] and 0–5 m (τ=0.47) and total distance (τ=0.46) times. Additionally, significant associations were observed between mean relative WAI and: CMJ relative eccentric deceleration impulse (τ=0.44), CMJ eccentric peak velocity (τ=-0.46) and RHT concentric impulse (τ=-0.56). Finally, significant relationships were identified between mean relative PI for all strides and the 10–20 m split, with peak velocity (PV) (τ=-0.58 to −0.73); and between ankle dorsiflexion ROM and PV (τ=-0.57). SignificanceAthletes with faster initial acceleration and overall sprint performance times demonstrated lower relative WAI during their strides and employed a jump strategy that optimized concentric impulse with a rapid eccentric phase. To attain a high PV the athletes appeared to require a stride that maximized glide and minimized vertical force, with greater ankle dorsiflexion ROM potentially facilitating this.

Changes in Countermovement Vertical Jump Force-Time Metrics During a Game in Professional Male Basketball Players.

Cabarkapa, D, Johnson, QR, Cabarkapa, DV, Philipp, NM, Eserhaut, DA, and Fry, AC. Changes in countermovement vertical jump force-time metrics during a game in professional male basketball players. J Strength Cond Res 38(7): 1326-1329, 2024-As technology within elite basketball advances and is more available to sporting organizations, novel approaches for assessing and addressing athletic performance during practice or competition are being continuously explored. The aim of this investigation was to examine changes in neuromuscular performance during live basketball play. Eight professional male basketball players volunteered to participate in this study. The testing procedures were conducted during a pre-tournament camp over a span of 2 days. During the first day, the athletes were familiarized with the testing procedures, and baseline measurements were obtained. Using a uni-axial force plate system sampling at 1,000 Hz, each athlete performed 3 countermovement vertical jumps (CVJ) without an arm swing before proceeding with their regular training activities. During the second day of the pre-tournament camp, the athletes repeated identical CVJ testing procedures before the start of the first quarter and post-first, second, third, and fourth quarter of a simulated 5-on-5 basketball game. Repeated-measures testing design was used to examine statistically significant differences in various force-time metrics of interest in comparison to the baseline levels (p < 0.05). Besides a trivial decrease in eccentric mean force, the findings of this study revealed no statistically significant changes in any force-time metrics of interest within both eccentric and concentric phases of the CVJ (i.e., mean and peak force and power, jump height, impulse, velocity, and contraction time). Thus, we can conclude that these variables were not sensitive to acute fatigue, suggesting that the neuromuscular performances of professional male basketball players tend to remain unchanged throughout a 5-on-5 simulated game.

Impact of arm technique and elastic force on vertical jump performance in physical education students: a convergent validation study

Background and Study Aim. Vertical jump performance is crucial for athletes in many sports. However, the optimal techniques for maximizing jump height and efficiency for both students and professional soccer players require more effective solutions. This study aimed to investigate the influence of various vertical jump techniques, focusing on arm swing and elastic force utilization, and to evaluate the extent of the impact that each modification has on biomechanical characteristics and performance outcomes. Materials and methods. Ten first-grade Sport Science students and ten professional soccer players from F.C. Malisevo participated in the study. The participants performed a series of jumps, including the Countermovement Jump (CMJ), Squat Jump (SJ), and Abalakov jump (ABL), while being recorded on an iPhone 13 Pro at 240 frames per second. Data analysis was conducted using the My Jump 3 app and SPSS 26 software. Descriptive statistics and one-way ANOVA were employed for comparative analysis. The Independent Samples T-test was used to compare differences in jump performance between the groups. Results. Significant differences in jump performance and force production were observed between SP and PES, with professional athletes demonstrating superior neuromuscular capabilities and better utilization of elastic energy. However, within each group, no significant differences were found between the different jump techniques, suggesting that arm swing and elastic force contribute similarly to overall jump height. Arm swing contributed 11.0% to jump performance in PES and 12.0% in SP, while the influence of elastic force stored in tendons during the eccentric phase was 7.0% in PES and 6.0% in SP. Conclusions. Specialized training significantly enhances jump performance, as evidenced by differences in CMJ, SJ, and ABL between SP and PES. Arm swing and elastic force utilization play crucial roles in vertical jumping, with professional athletes potentially leveraging arm mechanics more effectively. The study validates the reliability of the My Jump 3 app for measuring jump performance across diverse athletic backgrounds.

Differences in anthropometric and vertical jump force-time characteristics between U16 and U18 female basketball players.

Considering the importance of body composition and lower-body strength and power for basketball players' on-court performance, as well as a lack of sports science research focused on female athletes, the purpose of the present investigation was to record the anthropometric and countermovement vertical jump (CMJ) characteristics of top-tier U16 and U18 female basketball players and examine between-group differences in the aforementioned tests. Thirty-two athletes who were a part of the national basketball academy volunteered to participate in the present investigation. Following the body composition assessment conducted via a segmental multifrequency bioimpedance analyzer, athletes performed three CMJs while standing on a force plate system sampling at 1000 Hz. Independent t-test and Mann-Whitney U-test were used to examine between-group differences. The findings reveal significant differences in body composition and lower-body neuromuscular performance characteristics between female basketball players ages 16 and 18. Although no differences were observed in muscle and body fat percentages, the U18 group had significantly greater height, overall body mass (both muscle and fat mass), as well as greater segmental fat-free mass (trunk, both legs and arms), intracellular and extracellular water, and body mass index when compared to their U16 counterparts. On the other hand, the U18 group demonstrated longer eccentric, concentric, and braking phase duration, as well as overall contraction time when compared to the U16 players. In addition, the U18 athletes exhibited higher eccentric mean force and power, concentric impulse, peak power, and mean and peak force.

Effects of unstable load vs stable load on muscle activation and bar velocity during a bench press

Unstable load (UL) resistance exercises have gained popularity due to the potential to increase strength and neural development compared to traditional resistance exercises (Costello, 2022, J Strength Cond Res, 36, 881-887). It is assumed that training with an UL will increase the recruitment and activation of stabilising muscles, which is beneficial for daily activities and sport performance Kohler et al. (2010, J Strength Cond Res, 24, 313-321). Despite the recent increase in popularity, there is a limited amount of research that has been conducted using a UL and its impact on primary mover muscle activity. The purpose of this study was to investigate if a UL increases muscle activity of primary movers (pectoralis major sternocostal head [PEC] and triceps brachii long head [TRI]) during a bench press compared to a stable load (SL), measured via a Biopac electromyography (EMG) device. Additionally, bar velocity (m/s) using a GymAware device was compared between both UL and SL conditions. Following ethical approval, thirteen resistance-trained males were recruited (age = 21 ± 2 years; height = 178 ± 3 cm; mass = 79 ± 12 kg). Participants attended a familiarisation session, where 1RM and EMG maximum voluntary contraction (MVC) were determined. Following this, participants took part in a randomized crossover design at pre-determined loads. For the SL trial, participants performed 3 sets of 8 repetitions at 65% 1RM using a standard Olympic barbell. The US trial followed an identical protocol; however, an earthquake bar was loaded with 50% 1RM. The two-way repeated measures ANOVA revealed a significant interaction effect for the PEC activation, where there was an increase during UL but not SL condition (P = 0.001, ŋ2 = 0.633). No difference was found in the TRI between conditions (P &gt; 0.05). There was a significant 17% loss in velocity in the UL condition (P = 0.022, ŋ2 = 0.273). A significant difference was revealed in the eccentric phase for the UL condition (P = 0.001, ŋ2 = 0.473). In conclusion, muscle activation was increased in the pectoralis major muscle during the UL compared to SL resistance training. There was also an increase in velocity loss during the UL. In addition, the time of the eccentric phase was significantly longer during the UL condition. Therefore, despite the reduction in intensity, a UL may elicit greater activation of primary movers when compared to traditional resistance training alone.