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Relationships Between Concentric and Eccentric Strength and Countermovement Jump Performance in Resistance Trained Men
Abstract
The purpose of this study was to investigate the relationships between concentric and eccentric peak force (PF) and countermovement jump (CMJ) performance in resistance-trained men. Subjects were 12 men (mean ± SD; age: 25.4 ± 3.5 years; height: 177.2 ± 4.5 cm; mass: 84.0 ± 10.1 kg). The subjects were tested for concentric and eccentric PF using the Exerbotics squat device. Subjects then completed 3 CMJs to allow for the calculation of peak power (PP), peak ground reaction force (PGRF) and jump height (JH). Correlations between the variables of interest were calculated using Pearson product moment correlation coefficients. A large relationship was found between absolute concentric PF and absolute CMJ PP (r = 0.66, p < 0.05). Absolute eccentric PF had a very large relationship with absolute CMJ PP and CMJ JH (r = 0.74, p < 0.01 and r = 0.74, p < 0.001 respectively). In addition absolute eccentric PF was found to have a moderate relationship with relative CMJ PP (r = 0.58, p < 0.05). Relative eccentric PF was had a very large relationship with relative CMJ PP and CMJ JH (r = 0.73, p < 0.001 and r = 0.79, p < 0.001 respectively). Based on these findings strength and conditioning coaches and athletes who wish to enhance CMJ performance may wish to include exercises, which enhance lower body eccentric strength within their training.
... For instance, there are substantial differences in the relationships between CMJ jump height and peak/mean force (R 2 < 0.01-0.60), 63 60 These discrepancies may be a product of methodological differences such as verbal instructions,, 24,77 measurement equipment (e.g., position transducer verses force plate), fatigue levels, 48,78 or countermovement depth. 70,79 Most importantly, these differences may have resulted from the method of analysis and/or metric calculation. ...
... 78 For example, volleyball, basketball, and football athletes demonstrated rather low relationships between CMJ jump height and mean concentric force (R 2 = 0.08 to 0.32), 81 whereas track and field and recreational athletes demonstrate much stronger relationships (R 2 = 0.59-0.71). 63,64 Thus, it is possible that different athlete groups present with different relationships between metrics, and in turn, different domains of strength. This can only be tested, however, by employing research with consistent testing procedures and metric calculation methods across populations. ...
... Of the few available reports, RSI-modified 94,104-106 and RFD 107 measured in a CMJ appear to be independent from early (RFD, force < 0.15 s) isometric, peak absolute and relative isometric, and RSI measured in a drop jump r = 0.22-0.46. 43,63,94,[104][105][106][107] There were no studies identified in this review that compared CMJ timing metrics to measures derived from loaded ballistic tasks. Overall, it appears that timing variables from an unloaded ballistic task are unique from many other dynamic and isometric tasks, yet there remains insufficient evidence to fully recognize this group of metrics as a unique domain of force expression. ...
Maximal strength of the lower body is important for many athletic tasks and demands. Lower body extensor strength, defined as maximal expressions of force in the vertical plane, can be measured in several different ways, using a wide range of tests and metrics. Although there have been investigations into the interrelationships between lower body strength and force measures, there is no known analysis or synthesis of these data that focuses on classifying variables into groups based on statistical similarity and/or distinction. This information is important to consider in an environment where many measurement options exist for diagnosing lower body characteristics. Understanding the overlap and distinction of these analysis methods and metrics will inform parsimonious, yet comprehensive, assessment of the lower body. It was therefore the purpose of this review to explore and summarize the commonality (i.e., r, R ² , component loading) between metrics from weightbearing, multi-joint lower body strength tests that are presented in the current literature, with the aim to group metrics into distinct domains of strength expression. The results of this review suggest that five unique domains of lower body extensor strength are present in athletes and trained populations: 1) reactive dynamic, 2) unloaded dynamic, 3) loaded dynamic, 4) early isometric, and 5) maximal isometric. Despite these findings, there are considerable limitations and gaps in the literature, and it is suggested that additional empirical investigations be conducted to better understand this concept of lower body strength domains.
... A recent meta-analysis indicates that only a limited number of studies have explored the correlation between MES and vertical jumping performance [12]. For instance, Bridgeman et al. [13] utilized an Exerbotics squat machine (eSQ; Exerbotics, LLC, Tulsa, OK, USA) to measure MES during two repetitions of a squat, with the ECC phase lasting for 4 s each. They observed a significant positive correlation between MES and CMJ JH in strength trained athletes (r = 0.73, p <0.001). ...
... These correlations likely stem from the strong positive relationships observed between MES and MIS metrics and JH in both CMJ and DJ. Additionally, our findings on the positive correlations between MES and CMJ JH and DJ RSI are in line with existing literature [12][13][14][15]. Furthermore, our findings regarding the significant positive correlations between MIS, RSImod, and CMJ JH are also partially supported by previous studies [16][17][18][19]. ...
Maximal eccentric (MES) and isometric (MIS) muscle strength may enhance vertical jump performance by facilitating preloading and reducing energy loss during the eccentric (ECC) phase of the stretch-shortening cycle (SSC). However, the contributions of ECC and isometric (ISO) strength to the countermovement (CMJ) and depth jump (DJ) remain unclear due to variability in assessment methods (e.g., dynamometry, isometric mid-thigh pull) and the limited range of metrics examined in prior research. The aim of this study was to assess correlations between multi-joint lower extremity MES and MIS, obtained using a seated multi-joint isokinetic dynamometer, and 13 vertical ground reaction force (GRF) measures derived from the performance of three maximal effort DJs and CMJs. Twenty-five healthy young adults participated in this study (age = 21.9 ± 2.9 years). Pearson r correlation coefficients were used to assess the statistical significance (α = 0.05) of the relationships between absolute (N) and body mass normalized (BN) maximal strength measures and vertical jumping metrics. Moderate-to-strong positive correlations were identified between MES and MIS with broad performance metrics in CMJ and DJ, including reactive strength index (r = 0.45–0.53, p < 0.05), modified reactive strength index (r = 0.41–0.62, p < 0.05), and jump height (r = 0.59–0.75, p < 0.05). Moderate-to-strong positive correlations were also observed between MES and MIS with CON work (r = 0.58–0.71, p < 0.05) and CON peak power (r = 0.44–0.71, p < 0.05) for both the CMJ and DJ. In contrast, moderate-to-strong negative correlations were observed between MES and MIS with ECC work (r = 0.42–0.62, p < 0.005) and ECC peak power (r = 0.45–0.60, p < 0.05). These findings suggest that enhanced neuromuscular efficiency and joint stiffness in stronger musculature reduce energy absorption during the eccentric phase, minimizing mechanical deformation and preserving elastic energy for concentric propulsion. Combined, MES and MIS optimize force application, energy utilization, and control, which are crucial for maximizing jump height. These findings underscore the role of MES and MIS in influencing jumping performance across both the ECC and CON phases of the SSC. This insight is valuable for practitioners designing training programs aimed at improving vertical jumping ability.
... Notably, significant associations between lower extremity eccentric isokinetic torque and unilateral CMJ (Alves et al., 2022) and CoD performance (Chaabene et al., 2018) have been observed. Due to the eccentric movement mechanics in FW squats and its association to both CMJ and CoD, this may provide an effective approach to improve eccentric, i.e., braking activities (Maroto-Izquierdo et al., 2019;Norrbrand et al., 2008), which are essential skills of both CMJ and CoD movements (Bridgeman et al., 2018;Bright et al., 2023;Chaabene et al., 2018). Despite the similarities in physical requirements between FW squats, CoD and CMJ, to our knowledge, there is a lack of information about how these exercises may be related to each other. ...
... When performing FW squats at an appropriate tempo, the eccentric phase of the squat is accentuated, forcing the participant to perform the eccentric phase supramaximally and begin the concentric portion of the squat in a favourable muscle activation state (Spudić et al., 2020a). An accentuated eccentric phase of the movement was also found to be a prerequisite for CMJ (Alves et al., 2022;Bridgeman et al., 2018) and CoD performance (Chaabene et al., 2018). Moreover, the extent of eccentric contractions expression varies among different sports. ...
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.
... Isometric strength training has been shown to induce greater improvements in joint angle specific strength compared to dynamic based strength training (Bridgeman et al. 2018;Folland et al. 2005;Jones and Rutherford 1987;Kanehisa and Miyashita 1983;Kordi et al. 2020). Furthermore, floor-based dynamic jump performance has also shown improvements following isometric strength interventions (Bimson et al. 2017;Bogdanis et al. 2014). ...
The purpose of this study was to assess the effects of a 6‐week isometric training intervention on time of flight (ToF) in elite youth level gymnasts. Fourteen nationally elite youth gymnasts (10 females and 4 males; age = 15 ± 2 years; mass = 55.0 ± 8.2 kg and stature = 163.7 ± 6.5 cm) were recruited. Seven gymnasts in the intervention (INT) group performed a 6‐week isometric squat strength‐training programme, replacing heavy maximal lower limb exercises with three isometric exercises. Seven gymnasts in the control (CON) group performed a standardised strength programme. All gymnasts performed habitual trampoline training. Pre‐ and post‐testing included cycling peak power output, isometric strength, countermovement jumps and 20‐maximum ToF jump tests. Changes in ToF were greater for the INT group (+0.83 s; 2.8%) compared to the CON group (+0.06 s; +0.2%), with a significant group × time interaction effect on ToF (p = 0.021). The change in isometric squat peak force at 150° in the INT group (+379 N; 22.4%) was different to the change in the CON group (+78 N; 5.0%), with a significant group × time interaction effect (p = 0.032). The isometric intervention provided a sport‐specific training stimulus that was better than traditional heavy maximal resistance training alone for improving isometric strength and ToF in elite trampoline gymnasts.
... and dynamic squatting (r 5 0.66-0.84) (4,21). The results from this study suggest that peak propulsive power might be a valuable metric to monitor weekly during CMJ tests, especially in mesocycles with a congested match schedule. ...
Rebelo, A, Loturco, I, Pereira, JR, Martinho, DV, Valente-dos-Santos, J, and Broek, GV. Impact of congested match schedules on countermovement jump metrics in elite volleyball players. J Strength Cond Res XX(X): 000-000, 2024-The aim of this study was to assess the impact of a congested match schedule on various countermovement jump (CMJ) metrics recorded across the braking, transfer, propulsive, and flight phases of the CMJ. Fourteen male elite volleyball players were monitored across 7 microcycles, with CMJ assessments conducted at 14 time points using portable force plates. Repeated measures analysis of variance with Bonferroni post hoc tests and coefficient of variation (CV) analysis were used to analyze the data. The CVs for all metrics indicated a moderate variability between microcycles and low variability between the beginning and end of the weeks. Significant variability was observed in key performance metrics, including peak propulsive power (p < 0.001, partial eta squared [ηp2] = 0.336), peak propulsive velocity (p = 0.005, ηp2 = 0.207), propulsive phase duration (p = 0.008, ηp2 = 0.197), and jump momentum (p = 0.019, ηp2 = 0.225), across microcycles. These findings indicate that these CMJ metrics may be used as sensitive indicators of fatigue and performance changes during intense training and competitive periods. The total score of athleticism, calculated by averaging a set of standardized scores from multiple tests or repeated measures of the same test, for the propulsive and flight phases, proved to be particularly useful in providing a comprehensive view of the neuromuscular status. This emphasizes the importance of recording and analyzing a range of CMJ metrics to optimize training and recovery strategies in elite volleyball players.
... Performing FW squats with a delayed braking action in the first third of the eccentric phase allows for a greater eccentric load compared to the concentric load, thereby achieving eccentric overload (Beato et al., 2024;Martínez-Hernández, 2024). This may provide an effective approach to improving eccentric muscle strength capabilities (Maroto-Izquierdo et al., 2019;Norrbrand et al., 2008), which are essential for countermovement jump (CMJ) height and other key sport performance variables (Bridgeman et al., 2018;Bright et al., 2023;Chaabene et al., 2018). Additionally, the capability of flywheel (FW) devices to combine concentric and eccentric contractions allows stored elastic energy generated during the eccentric phase to be released in the subsequent concentric contraction, acutely enhancing force and power output (Berg & Tesch, 1998;Vogt & Hoppeler, 2014). ...
This study aimed to investigate the effects of an 8-week resistance training using flywheel (FW) device on countermovement jump (CMJ) performance and resting stiffness of the vastus lateralis (VL) muscle. Physically active adults were randomly assigned to a training intervention group (T; n = 18) and a control group (C; n = 13), which received no intervention. Jump performance variables and ultrasound- assessed resting VL shear modulus were measured before and after the intervention. Analysis of covariance revealed statistically significant group differences in jump height (T = +9%; C = -3%), rate of force development (T = +32%; C = +4%), peak power (T = +9%; C = -1%), and peak force (T = +7%; C = -1%). Jump performance improved only in the training group (all CMJ variables p < 0.05). Conversely, no significant changes within groups were observed in the resting shear wave modulus results (p > 0.05). VL stiffness decreased in the training group (−4%) and increased in the control group (+6%). Our results suggest that resistance training using FW device with individually allocated high-load FW inertia induces significant improvements in jump performance, which are not underpinned by changes in VL muscle stiffness.
... Quantifying stiffness during the eccentric part of a countermovement jump (CMJ) may therefore provide valuable information regarding the neuromusculotendon function of the athlete, in particular in relation to the stretch shortening cycle. In addition, CMJ performance is highly correlated to isokinetic and isometric strength of the ankle, knee and hip (Nuzzo et al., 2008) and especially closed chain eccentric strength (Bridgeman et al., 2018) and may be used as an indication of the athlete's overall strength. ...
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 (kLLS), 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: kLLS 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 kLLS and leg stiffness, indicating high concurrent validity. Discussion: kLLS offers valid and valuable information affecting performance, injury risk, and return-to-sport decisions. Conclusion: The findings suggest that kLLS is a valid method for calculating stiffness in CMJs and equal to 3D leg stiffness.
... Implementation of resistance training methods such as flywheel training is likely to enhance jumping performance and mechanical power [13,19,43,45]. Improvements in power and jump performance are likely to be associated with enhanced stretch-shortening cycle function and optimized ability to repeatedly perform high-intensity eccentric actions [77,78]. The most up to date evidence (considered moderate and high quality) amongst male populations highlights that flywheel training interventions of 5-24 weeks enhance jumping performance [45]. ...
Background
Flywheel resistance training has become more integrated within resistance training programs in a variety of sports due to the neuromuscular, strength, and task-specific enhancements reported with this training.
Objective
This paper aimed to present the consensus reached by internationally recognized experts during a meeting on current definitions and guidelines for the implementation of flywheel resistance training technology in sports.
Methods
Nineteen experts from different countries took part in the consensus process; 16 of them were present at the consensus meeting (18 May 2023) while three submitted their recommendations by e-mail. Prior to the meeting, evidence summaries were developed relating to areas of priority. This paper discusses the available evidence and consensus process from which recommendations were made regarding the appropriate use of flywheel resistance training technology in sports. The process to gain consensus had five steps: (1) performing a systematic review of systematic reviews, (2) updating the most recent umbrella review published on this topic, (3) first round discussion among a sample of the research group included in this consensus statement, (4) selection of research group members—process of the consensus meeting and formulation of the recommendations, and (5) the consensus process. The systematic analysis of the literature was performed to select the most up-to-date review papers available on the topic, which resulted in nine articles; their methodological quality was assessed according to AMSTAR 2 (Assessing the Methodological Quality of Systematic Review 2) and GRADE (Grading Recommendations Assessment Development and Evaluation). Statements and recommendations scoring 7–9 were considered appropriate.
Results
The recommendations were based on the evidence summary and researchers’ expertise; the consensus statement included three statements and seven recommendations for the use of flywheel resistance training technology. These statements and recommendations were anonymously voted on and qualitatively analyzed. The three statements reported a score ranging from 8.1 to 8.8, and therefore, all statements included in this consensus were considered appropriate. The recommendations (1–7) had a score ranging from 7.7 to 8.6, and therefore, all recommendations were considered appropriate.
Conclusions
Because of the consensus achieved among the experts in this project, it is suggested that practitioners and researchers should adopt the guidelines reported in this consensus statement regarding the use of flywheel resistance technology in sports.
Background
Conflicting results have been reported regarding the effects of resistance exercise training with eccentric (lengthening muscle) versus concentric (shortening muscle) contractions on changes in muscle mechanical function assessed by different contraction modes.
Objective
The main objective of this systematic review with meta-analyses was to compare effectiveness of maximal isokinetic eccentric-only and concentric-only strength training for changes in maximal voluntary eccentric (MVCECC), concentric (MVCCON), and isometric contraction (MVCISO) strength in healthy adults.
Methods
We conducted a systematic search in PubMed, SPORTDiscus, and Google Scholar from February to March 2024 for studies that met the following criteria: (1) randomized controlled trials; (2) inclusion of eccentric-only and concentric-only strength training groups; (3) use of an isokinetic dynamometer for training and testing; (4) reporting changes over time in MVCCON and MVCECC; and (5) using healthy adult participants. The certainty of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation approach. A multilevel random-effects model meta‑analyses with robust variance estimation were performed in Rstudio software using metaphor and clubSandwich packages. Moreover, sensitivity analysis was performed, excluding the highly influential studies. The potential moderating role of sex, training status and age of the participants, muscles, velocity in training and testing, initial MVCECC, MVCCON, and MVCECC/MVCCON ratio, and training-related variables such as number of repetitions per set, number of sets, number of sessions per week, and duration of the training protocol were also assessed.
Results
Twenty-seven studies matched with the criteria, and overall 162 study results were identified and included in the meta-analyses. Greater effects on MVCECC was found after eccentric-only versus concentric-only training (Hedge’s g: 1.51; 27% vs. 10%; p < .05). However, no differences were evident between the training modalities for changes in MVCCON (Hedge’s g: − 0.10; 13% vs. 14%, p = .726) and MVCISO (Hedge’s g: − 0.04; 18% vs. 17%; p = .923). The subgroup analyses showed smaller effect of eccentric-only than concentric-only training on MVCCON when eccentric-only training was performed at higher velocities than the velocities of MVCCON testing (Hedge’s g: − 0.99; p < .05). Meta-regressions showed that the longer the training period, the greater the superior effect of eccentric over concentric training on MVCECC.
Conclusions
Eccentric-only strength training is more effective for improving MVCECC, but both concentric-only and eccentric-only training provide similar effects on improving MVCCON and MVCISO. Further studies are necessary to investigate the mechanisms underpinning the superior effect of eccentric-only training.
Objective: To examine whether musculoskeletal injury history is a factor that influences countermovement jump (CMJ) performance in rugby players and to compare CMJ performance between player’s position (forwards or backs). Methods: Thirty rugby players (15 with an injury history and 15 without an injury history) performed the CMJ using an inertial sensor (Baiobit®) to evaluate kinematic (Jump Height, Velocity and Phase duration) and kinetic data (rate of force development [RFD], impact peak [IP], take-off force and Stiffness]. The group comparison was performed with an independent t-test, and the association between CMJ performance, sociodemographic variables and injury history was investigated with Pearson’s correlation test. Results: Rugby players with and without history of musculoskeletal injury differed in age and playing experience, but there was no difference in CMJ performance between groups. Jump height of uninjured players was positively correlated take-off force and RFD and negatively correlated with concentric phase duration and RFD. Injured players demonstrated a negative correlation between take-off force and IP. Compared to backs, forwards were heavier and taller, showed greater IPs and were more likely to have an injury history. Conclusions: There were no differences in CMJ performance between rugby players with and without an injury history. Forwards showed greater IPs and were more likelier to have an injury history than backs.
The aim of this study was to investigate the test-retest reliability of a novel multi-joint isokinetic squat device. The subjects in this study were 10 strength-trained athletes. Each subject completed three maximal testing sessions to assess peak concentric and eccentric force (N) over a three-week period utilising the Exerbotics squat device. Mean differences between eccentric and concentric force across the trials were calculated. Intraclass correlation coefficients (ICC) and coefficients of variation (CV) for the variables of interest were calculated using an excel reliability spread sheet. Between trials 1-2 an 11.0% and 2.3% increase in mean concentric and eccentric force respectively was reported. Between trials 2-3 a 1.35% increase in the mean concentric force production and a 1.4% increase in eccentric force production was reported. The mean concentric peak force CV and ICC across the three trials was 10% (7.6 - 15.4) and 0.95 (0.87 - 0.98) respectively. Whilst the mean eccentric peak force CV and ICC across the trials was 7.2% (5.5 - 11.1) and 0.90 (0.76 - 0.97) respectively. Based on these findings it is suggested that the Exerbotics squat device shows good test-re-test reliability. Therefore practitioners and investigators may consider its use to monitor changes in concentric and eccentric peak force.
ECCENTRIC TRAINING AND ECCENTRIC MUSCULAR CONTRACTIONS FOCUS ON ACTIVE LENGTHENING WHILE LOADED. WHEN COMPARED WITH CONCENTRIC MOVEMENTS, ECCENTRIC ACTIONS YIELD GREATER FORCE LEVELS WITH CONCOMITANT LOWER NEUROMUSCULAR ACTIVATION LEVELS. ECCENTRIC TRAINING IS MAINLY INCORPORATED INDIRECTLY BY STRENGTH AND CONDITIONING AND FITNESS PROFESSIONALS LEADING TO IT BEING OFTEN UNDERUSED AND UNDERVALUED. ECCENTRIC TRAINING CAN READILY BE INCORPORATED INTO A TRAINING PROGRAM ALONG WITH THE USE OF NONTRADITIONAL EXERCISES FOR ALL POPULATIONS. THIS ARTICLE EXAMINES THE SCIENCE OF ECCENTRIC TRAINING AND EXTENDS THIS SCIENCE BY FOCUSING ON PRACTICAL RECOMMENDATIONS. SUGGESTED PROGRESSIONS ARE PROVIDED DEPENDING ON TRAINING BACKGROUND ALONG WITH CASE STUDY SCENARIOS.
This study assessed markers of muscle damage and training adaptations to eccentric-overload flywheel resistance exercise (RE) in men and women.
Dynamic strength (1 RM), jump performance, maximal power at different percentages of 1 RM, and muscle mass in three different portions of the thigh were assessed in 16 men and 16 women before and after 6 weeks (15 sessions) of flywheel supine squat RE training. Plasma creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations were measured before, 24, 48 and 72 h after the first and the last training session.
After training, increases in 1 RM were somewhat greater (interaction P < 0.001) in men (25 %) than in women (20 %). Squat and drop jump height and power performance at 50, 60, 70 and 80 % of 1 RM increased after training in both sexes (P < 0.05). Power improvement at 80 % of 1 RM was greater (interaction P < 0.02) in men than women. Muscle mass increased ~5 % in both groups (P < 0.05). CK increased in men after the first training session (P < 0.001), whereas the response in women was unaltered. In both sexes, LDH concentration was greater after the first training session compared with basal values (P < 0.05). After the last session, CK and LDH remained at baseline in both groups.
These results suggest that although improvements in maximal strength and power at high loads may be slightly greater for men, eccentric-overload RE training induces comparable and favorable gains in strength, power, and muscle mass in both men and women. Equally important, it appears muscle damage does not interfere with the adaptations triggered by this training paradigm.
This study examined the linearity of the electromyographic (EMG) amplitude versus concentric and eccentric squat force relationships for monoarticular and biarticular thigh muscles. Fourteen resistance-trained men (mean ± SD age = 22 ± 2 years; estimated thigh muscle cross sectional area = 221.9 ± 22.7 cm²) performed concentric and eccentric squats using a novel testing device from 10% to 90% of their maximum average force. Surface EMG signals were detected from the right vastus lateralis, rectus femoris, and biceps femoris. Linear regression was used examine the relationships between EMG amplitude and force, and repeated measures analyses of variance were utilized to assess differences among the muscles. Moderate-to-high coefficients of determination were found for the vastus lateralis for both concentric and eccentric testing (r = 0.587-0.992). For the biceps femoris, the mean linear slope coefficient was significantly greater for concentric versus eccentric testing (0.044 vs. 0.013 µV RMS · N, p = 0.002, effect size = 1.44). Whereas EMG amplitude for the vastus lateralis and rectus femoris increased with changes in eccentric force output, the electrical activity of the biceps femoris remained stable. These results demonstrated that the EMG amplitude versus force relationships for the vastus lateralis were linear despite the fact that force production during the squat is related to the activation of muscles that must simultaneous function as agonists and antagonists. Our findings for eccentric force testing are in agreement with investigations showing reduced hip extensor activity during concurrent extension at the hip and knee joints.
Eccentric (ECC) exercise is classically used to improve muscle strength and power in healthy subjects and athletes. Due to its specific physiological and mechanical properties, there is an increasing interest in employing ECC muscle work for rehabilitation and clinical purposes. Nowadays, ECC muscle actions can be generated using various exercise modalities that target small or large muscle masses with minimal or no muscle damage or pain. The most interesting feature of ECC muscle actions is to combine high muscle force with a low energy cost (typically 4- to 5-times lower than concentric muscle work) when measured during leg cycle ergometry at a similar mechanical power output. Therefore, if caution is taken to minimize the occurrence of muscle damage, ECC muscle exercise can be proposed not only to athletes and healthy subjects, but also to individuals with moderately to severely limited exercise capacity, with the ultimate goal being to improve their functional capacity and quality of life. The first part of this review article describes the available exercise modalities to generate ECC muscle work, including strength and conditioning exercises using the body's weight and/or additional external loads, classical isotonic or isokinetic exercises and, in addition, the oldest and newest specifically designed ECC ergometers. The second part highlights the physiological and mechanical properties of ECC muscle actions, such as the well-known higher muscle force-generating capacity and also the often overlooked specific cardiovascular and metabolic responses. This point is particularly emphasized by comparing ECC and concentric muscle work performed at similar mechanical (i.e., cycling mechanical power) or metabolic power (i.e., oxygen uptake, [Formula: see text]). In particular, at a similar mechanical power, ECC muscle work induces lower metabolic and cardiovascular responses than concentric muscle work. However, when both exercise modes are performed at a similar level of [Formula: see text], a greater cardiovascular stress is observed during ECC muscle work. This observation underlines the need of cautious interpretation of the heart rate values for training load management because the same training heart rate actually elicits a lower [Formula: see text] in ECC muscle work than in concentric muscle work. The last part of this article reviews the documented applications of ECC exercise training and, when possible, presents information on single-joint movement training and cycling or running training programs, respectively. The available knowledge is then summarized according to the specific training objectives including performance improvement for healthy subjects and athletes, and prevention of and/or rehabilitation after injury. The final part of the article also details the current knowledge on the effects of ECC exercise training in elderly populations and in patients with chronic cardiac, respiratory, metabolic or neurological disease, as well as cancer. In conclusion, ECC exercise is a promising training modality with many different domains of application. However, more research work is needed to better understand how the neuromuscular system adapts to ECC exercise training in order to optimize and better individualize future ECC training strategies.
: Research has demonstrated a clear relationship between absolute and relative strength and sprint and jump performance in adult athletes; however, this relationship in younger athletes has been less extensively studied. The aim of this study, therefore, was to determine the relationships between strength, sprint and jump performances in well trained youth soccer players. Thirty four young male soccer players (17.2 ± 0.6 years, body mass 72.62 ± 7.42 kg; height 179.27 ± 6.58 cm) performed a predicted maximal squat test, twenty metre sprints, squat jumps and countermovement jumps. Absolute strength showed the strongest correlations with 5m sprint times (r -0.596, p<0.001, power = 0.99), squat jump height (r 0.762, p<0.001, power = 1.00) and CMJ height (r 0.760, p<0.001, power = 1.00), whereas relative strength demonstrated the strongest correlation with 20m sprint times (r -0.672, p<0.001, power = 0.99). The results of this study illustrates the importance of developing high levels of lower body strength in order to enhance sprint and jump performance in youth soccer players, with stronger athletes demonstrating superior sprint and jump performances.
The aim of our study was to assess the interday test-retest reliability (focussing on the separate contribution of systematic and random error) of selected 10-trial mean ground reaction force (GRF) parameters and GRF symmetry indices measured during running. Ten competitive male heel-strike runners (aged, 26.2 ± 5.7 years) performed 10 successful running trials across the force platform at a constant velocity of 4.0 m · s -1 ± 10% wearing their customary running footwear. The testing procedure was repeated under similar conditions 1 week later. The results showed no statistically significant differences between the means of Test 1 and Test 2 for most GRF parameters and symmetry indices, indicating non-significant systematic error. Correlation coefficients ranged from 0.73 to 0.99 for GRF parameters. Random error was small, with SE(meas) less than 10% of the Test 1 mean value for almost all GRF parameters. Symmetry indices displayed correlation coefficients ranging from -0.44 to 0.91. Based on these and the size of the SE(meas), the symmetry indices displayed variable reliability, with the most reliable being those associated with peak vertical active force and peak horizontal propulsive force.
AN ECCENTRIC MUSCLE ACTION IS DESCRIBED AS A MUSCULAR CONTRACTION OCCURRING WHILE THE MUSCLE IS SIMULTANEOUSLY LENGTHENING. ECCENTRIC MUSCLE ACTIONS CAN BE IMPLEMENTED BY THE STRENGTH AND CONDITIONING SPECIALIST IN A VARIETY OF WAYS TO ACHIEVE A NUMBER OF GOALS FROM INCREASING STRENGTH AND POWER PRODUCTION TO PREVENTION AND REHABILITATION OF INJURY. THE PHYSIOLOGIC RATIONALE AS WELL AS THE LOADING PARAMETERS FOR THESE VARIOUS FORMS OF “ECCENTRIC TRAINING” WILL BE BRIEFLY DISCUSSED IN THIS REVIEW.
Previous research has demonstrated the importance of both dynamic and isometric maximal strength and rate of force development (RFD) in athletic populations. The purpose of this study was to examine the relationships between measures of isometric force (PF), RFD, jump performance and strength in collegiate football athletes. The subjects in this study were twenty-two men [(mean ± SD):age 18.4 ± 0.7 years; height 1.88 ± 0.07 m; mass 107.6 ± 22.9 kg] who were Division I college football players. They were tested for PF using the isometric mid thigh pull exercise. Explosive strength was measured as RFD from the isometric force-time curve. The one repetition maximum (1RM) for the squat, bench press and power clean exercises were determined as measures of dynamic strength. The two repetition maximum (2RM) for the split jerk was also determined. Vertical jump height and broad jump was measured to provide an indication of explosive muscular power. There were strong to very strong correlations between measures of PF and 1RM (r = 0.61 - 0.72, p < 0.05). The correlations were very strong between the power clean 1RM and squat 1RM (r = 0.90, p < 0.05). There were very strong correlations between 2RM split jerk and clean 1RM (r = 0.71, p < 0.05), squat 1RM (r = 0.71, p < 0.05), bench 1RM (r = 0.70, p < 0.05) and PF (r = 0.72, p < 0.05). There were no significant correlations with RFD. The isometric mid thigh pull test does correlate well with 1RM testing in college football players. RFD does not appear to correlate as well with other measures. The isometric mid thigh pull provides an efficient method for assessing isometric strength in athletes. This measure also provides a strong indication of dynamic performance in this population.
Reports 3 errors in the original article by K. O. McGraw and S. P. Wong (Psychological Methods, 1996, 1[1], 30–46). On page 39, the intraclass correlation coefficient (ICC) and r values given in Table 6 should be changed to r = .714 for each data set, ICC(C,1) = .714 for each data set, and ICC(A,1) = .720, .620, and .485 for the data in Columns 1, 2, and 3 of the table, respectively. In Table 7 (p. 41), which is used to determine confidence intervals on population values of the ICC, the procedures for obtaining the confidence intervals on ICC(A,k) need to be amended slightly. Corrected formulas are given. On pages 44–46, references to Equations A3, A,4, and so forth in the Appendix should be to Sections A3, A4, and so forth. (The following abstract of this article originally appeared in record 1996-03170-003.). Although intraclass correlation coefficients (ICCs) are commonly used in behavioral measurement, psychometrics, and behavioral genetics, procedures available for forming inferences about ICC are not widely known. Following a review of the distinction between various forms of the ICC, this article presents procedures available for calculating confidence intervals and conducting tests on ICCs developed using data from one-way and two-way random and mixed-effect analysis of variance models. (PsycINFO Database Record (c) 2012 APA, all rights reserved)