Eccentric Utilization Ratio Research Articles

A007: Neuromuscular Factors Affecting Lower Extremity Explosive Strength of Male Track and Field Athletes

Objective: To investigate the neural and muscular factors affecting the explosive power of the lower limbs in college athletes by testing the neuromuscular function (H reflex) and explosive performance of male sprinting and long jump athletes. Methods: H-reflex, countermovement jump (CMJ), squat jump (SJ) and one repetition maximum(1RM) tests were performed on male track and field college athletes using electromyography evoked potential and three-dimensional dynamometer. Test data of Hmax/Mmax, H-index, peak countermovement jump force and vertical stiffness of male college athletes were obtained. The Pearson's correlation coefficient was used to analyze the relationship between neuromuscular function and explosive performance in male sprint and long jump athletes. Results: H-index was significantly and positively correlated (r=0.65, p＜0.05) with rate of force development(RFD); Hmax/Mmax was not significantly correlated with RFD and reactive strength index-modified(RSImod)in male athletes. CMJ peak force was significantly correlated with RFD (r=0.83, p ＜0.01) and RSImod (r=0.85 , p ＜0.01) were significantly and positively correlated. Vertical stiffness was significantly and positively correlated with RFD (r=0.64, p＜0.05) and RSImod (r=0.73, p＜0.05).1RM, eccentric utilization ratio (EUR) was not significantly correlated with RFD and RSImod. Conclusion: The neuromuscular factors affecting explosive lower limb strength in male collegiate athletes were H-index, CMJ peak force, and vertical stiffness. These results suggest that athletes who performed better in explosive strength showed faster nerve conduction velocity, greater lower limb muscle strength and vertical stiffness. There was also a strong correlation between lower limb muscle strength and nerve conduction velocity and vertical stiffness.

The impact of flywheel resistance squat training on lower limb strength in female college basketball players.

This study compared the effects of Flywheel Resistance Squat Training (FRST) vs. Traditional Resistance Squat Training (TRST) on lower body strength in female collegiate basketball players. Nineteen participants were randomly assigned to either the FRST group (n = 9) or the TRST group (n = 10) through a random number draw. Both groups underwent a 6-week intervention with training sessions conducted twice a week. The FRST group utilized an inertia of 0.075 kg ·m2, while another group trained at 80% of their one-repetition maximum (1RM). Each training session consisted of 4 sets of 8 repetitions with a 3-minute rest between sets. Both groups performed standardized warm-ups and stretches before and after each training session. The effectiveness of the training methods was assessed through the Countermovement Jump (CMJ), Reactive Strength Index (RSI), Eccentric Utilization Ratio, Running Vertical Jump, and 1RM squat. The FRST and TRST groups showed differences within groups in both CMJ and 1RM squat (p < 0.01), with the FRST group demonstrating moderate effect sizes in CMJ (Hedges' g = 0.59) and 1RM (Hedges' g = 1.01). However, there were no differences between groups (p > 0.05). The Eccentric Utilization Ratio showed a small effect size (p = 0.78; ). Additionally, Reactive Strength Index and Running Vertical Jump exhibited low test-retest reliability. The two groups did not exhibit a statistically significant difference. Nonetheless, both FRST and TRST demonstrated positive effects on 1RM squat and CMJ performance compared to baseline values for each method. Therefore, flywheel resistance training can be considered an effective alternative to traditional resistance training for enhancing strength levels in female basketball players.

Is larger eccentric utilization ratio associated with poorer rate of force development in squat jump? An exploratory study

ABSTRACT This exploratory study examines the relationship between the eccentric utilization ratio (EUR) and the rate of force development (RFD) in squat jumps (SJ). EUR, a key metric in sports science, compares performance in countermovement jumps (CMJ) and squat jumps (SJ). The study hypothesizes that a higher EUR is associated with a poorer RFD in SJ. Basketball and soccer players, long-distance runners, alongside physical education students (209 men; age: 23.2 ± 4.95 years and 104 women; age: 22.7 ± 4.42 years) participated. The EUR was calculated from jump height, peak force and peak power. The results indicated a small to moderate but significant negative correlation between EUR based on peak force or peak power and RFD in SJ (r = –.41 and −.27), suggesting that a higher EUR might be linked to a diminished ability to rapidly develop force in SJ. Thus, a higher EUR may not indicate superior athletic performance.

Changes in eccentric utilization ratio, reactive strength index and leg stiffness in highly trained sprinters between training phases

Purpose: To determine changes in eccentric utilization ratio (EUR), reactive strength index (RSI), squat jump (SJ) and countermovement jump (CMJ) parameters in elite sprinters from the preparation phase to the competition (indoor) phase.Methods:Ten elite-level sprinters (n=10) were examined. All sprinters performed the SJ, CMJ and 10/5 rebound jump (RJ) tests. Body composition analysis was assessed using dual X-ray absorptiometry (DXA) method. A paired t-test was performed to determine statistical significance.Results:SJ height and relative peak power increased significantly from 43.10 ± 6.1 cm to 46.30 ± 5.7 cm (P= .013, Cohen’s d= .98) and from 52.62 ± 4.5 W·kg BM-1 to 55.55 ± 4.5 W·kg BM-1 (P= .017, d= .92) respectively. CMJ height and relative peak power increased significantly from 46.78 ± 6.1 cm to 49.18 ± 5.5 cm (P= .039, d= .76) and from 55.53 ± 4.1 W·kg BM-1 to 57.92 ± 4.0 W·kg BM-1 (P= .024, d= .86) respectively. No significant differences were observed in RJ performance parameters.Conclusions:SJ and CMJ height, flight time and peak power output per body mass increased in elite sprinters from the preparation to the competition phase while RSI, EUR and leg stiffness (LS) values did not. SJ and CMJ performance can be used as markers of training phase changes in elite sprinters. EUR should be used cautiously to determine training status in elite sprinters since sprint training encompasses reactive strength training all year round. Reactive strength levels via RSI and stiffness levels should be assessed individually in each training phase to determine whether the measured value of these parameters is satisfactory to optimize competition readiness. LS levels should not be compared to general guidelines but rather individually to the athletes’ sprint performance and then training should be adjusted accordingly.

Comparing autoregulatory progressive resistance exercise and velocity-based resistance training on jump performance in college badminton athletes.

Jumping ability has been identified as a key factor that influences the performance of badminton athletes. Autoregulatory progressive resistance exercise (APRE) and velocity-based resistance training (VBRT) are commonly used approaches to enhance muscle strength and have been shown to accurately monitor the development of explosive power to improve jumping ability. This study aims to investigate the effects of APRE and VBRT on badminton athletes' jumping ability and to provide practical insights into improving their jumping performance during competitions. Upon completing familiarization and pretesting, 18 badminton athletes were included and completed the training intervention (age, 21.4 ± 1.4 years; stature, 170.1 ± 7.3 cm; body mass, 65.9 ± 12 kg); they were randomly divided into the APRE group (n = 9) and VBRT group (n = 9). Jumping performance was assessed during the countermovement jump (CMJ), squat jump (SJ), and drop jump (DJ) via SmartJump, with CMJ 's and SJ's jump height, eccentric utilization ratio (EUR), and reactive strength index (RSI). All participants then completed a 4-week in-season resistance training intervention. (1) The results of the within-group indicated that only the CMJ (pre: 41.56 ± 7.84 vs post: 43.57 ± 7.85, p < 0.05) of the APRE group had significant differences, whereas the SJ, EUR, and RSI were not significantly different (p > 0.05). (2) The results of the intergroups revealed that all indicators had no significant differences (p > 0.05), but APRE had a moderate effect size on the improvement of the CMJ (η2 = 0.244) and EUR (η2 = 0.068) when compared with VBRT. The results showed that, compared to VBRT, APRE can effectively improve the performance of the reactive athletes' lower limb explosive power in the CMJ in a shorter period of time. The findings indicate that APRE may be useful for coaches seeking to improve the CMJ performance of athletes in the short term.

Lower Limb Unilateral and Bilateral Strength Asymmetry in High-Level Male Senior and Professional Football Players.

This study sought to assess the relationship between different jumping asymmetries and associated performance variables in high-level male senior and professional football players. Nineteen football players with at least 12 years of training experience (23.2 ± 3.1 years of age; 75.2 ± 4.8 kg of body mass and 181 ± 0.06 cm of height) participated in this study performing countermovement jump (CMJ), squat jump (SJ), single-leg CMJ and drop jump (DJ), associated performance variable eccentric utilization ratio (EUR), stretch-shortening cycle (SSC), bilateral deficit (BLD), and limb symmetry index (LSI) were determined. High correlations were observed between different methodologies of jump tests and associated performance indicators (SSC, BLD, EUR), except LSI. Moreover, CMJ and SJ results were different (p < 0.05), but no differences were found between interlimb in CMJ (p = 0.19) and DJ (p = 0.14). Between the same limbs and different jumps differences were detected in CMJ and DJ (p < 0.01), and it has also been found that the laterality effect size on strength was small in CMJ (ES = 0.30) and DJ (ES = 0.35). LSI between CMJ and DJ was not different despite higher mean values in CMJ, and although mean BLD was positive (>100%), the results highlight the need for individual evaluation since eight players scored negatively. An in-depth and accurate analysis of performance in preseason screening jump tests should be considered, aiming to detect injury risk, specifically evaluating different jumping test methodologies, and determining jumping associated performance variables for each test, namely EUR, SSC, BLD, and LSI. Specific muscle-strengthening exercises could be implemented based on this study results and outcomes, aiming to reduce injury risks and lower extremity asymmetries and to enhance individual football performance in high-level male senior and professional football players. Sports institutions should pay special attention regarding potential health problems in athletes exposed to daily high training loads.

The Relationship of Anthropometric and Physical Performance Characteristics on Competitive Success in Amateur, Elite, and Professional Rodeo Athletes.

Oranchuk, DJ, Gullett, LK, Kicia, M, Thome, B, and Game, A. The relationship of anthropometric and physical performance characteristics on competitive success in amateur, elite, and professional rodeo athletes. J Strength Cond Res 37(7): 1495-1506, 2023-Reference anthropometric and physical performance qualities can improve understanding of sporting needs and streamline preparation and rehabilitation programs. However, these data and their relationships with competitive success are absent in rodeo athletes. We hypothesized that riding performance would be most correlated with hip adductor, neck, and grip strength, whereas jump, reactive strength index (RSI), and change of direction abilities would best predict bull-fighting performance. Forty-three amateur ( n = 9), professional ( n = 23), or internationally ranked ( n = 11) male rodeo athletes (bareback = 9, bull riders = 16, saddle bronc = 7, bullfighters = 11) (26.8 ± 5.6 years) volunteered for this study. Anthropometrics included body mass, height, and body fat percentage. Performance measures included isometric hip adduction and abduction, neck flexion and extension, handgrip strength, squat and countermovement jump heights, eccentric utilization ratio, reactive strength index, change of direction, bike sprints, and several pneumatic power measures. Bullfighters were taller and heavier than bull riders (effect size [ES] = 0.84-0.87, p = 0.008-0.017). Bull riders were leaner than bullfighters (ES = 0.74, p = 0.012). Fighters had greater RSI than riders (ES = 0.73-1.47, p < 0.001-0.030). Competitive level of rodeo riders ( n = 32) correlated with age, rodeo experience (ρ = 0.37-0.43, p = 0.013-0.049), bent-leg abduction (ρ = 0.43, p = 0.014), straight-leg hip adduction and abduction (ρ = 0.49-0.56, p < 0.001-0.005), neck flexion force (ρ = 0.43, p = 0.016), and rotational power (ρ = 0.50, p = 0.004). The competitive level of the fighters correlated with age (ρ = 0.64, p = 0.036) and time trial performance (ρ = -0.76, p = 0.006). This is the first study providing normative and correlational strength and power performance data in a rodeo population. These data highlight the need for more event-specific physical preparation. Riders should focus their physical preparation on hip and neck strength and rotational power. Bullfighters should prioritize stiffness and anaerobic power.

The effects of velocity-based versus percentage-based resistance training on athletic performances in sport-collegiate female basketball players.

Introduction: The study compared the effects of 6-week (2 sessions/week) velocity-based resistance training (VBRT) and percentage-based resistance training (PBRT) on athletic performance in Sport-College female basketball players. Methods: Fifteen participants were assigned to the VBRT (n = 8) or PBRT (n = 7) groups. The load in VBRT group were determined through the sessional target velocity and velocity loss monitoring, whereas PBRT group used a fixed-load based on percentage of 1-repetition maximum (1RM). Both groups completed intervention that involved the free weight back squat and bench press using the same relative load (linear periodization from 65% to 95% 1RM). Training loads data was continuously recorded. Measurements at baseline (T0) and post-training (T2) included 1RM, countermovement-jump (CMJ), squat-jump (SJ), eccentric-utilization-ratio (EUR), drop-jump height and reactive-strength-index (DJ, DJ-RSI), plyometric-push-up (PPU), 505 change-of-direction (COD), 10-m、20-m sprint (T-10、T-20), 17 × 15m drill-lines (17-drill), Hexagon agility, and functional movement screen (FMS). A mid-term (T1) assessment was included to investigate the short-term effects of both methods and the fluctuation of personalized 1RM. Results: No between-group differences were observed at T0 for descriptive variables (p > 0.05). Both groups showed significant improvement in strength gains for back squat and bench press, but VBRT showed likely to very likely favorable improvements in CMJ, SJ, EUR, DJ-RSI, Hexagon and COD among athletic performance. The VBRT showed likely to very likely improvements in 17-drill and DJ, while PBRT showed unclear effects. The lifted weights adjusted by VBRT method were higher than prescribed by PBRT (p < 0.05) for the same subjects. Conclusion: Compared with fixed-load PBRT, VBRT enhanced power and athletic performance despite similar strength gains. VBRT can be regarded as a more functional resistance-training method under linear periodization.

Change of Direction Deficit: A Promising Method to Measure a Change of Direction Ability in Adolescent Basketball Players.

The aims of this study were to determine the relationship between vertical jumping performance, linear speed, change of direction speed (CODs) time and the COD deficit (CODD) in adolescent basketball players and to analyze the CODD between faster and slower players based on linear speed performance. Thirty-eight male basketball players (age: 15.47 ± 0.51 years; body height: 185.19 ± 5.67 cm; body mass: 71.87 ± 7.29 kg) completed countermovement jumps (CMJ) with and without an arm swing, squat jumps (SJs), linear sprints at 20 m with split times at 5 and 10 m, the pro-agility test and the zig-zag tests. Furthermore, the CODD was calculated as the difference between the 20 m linear speed result and CODs time in both COD tests. Pearson and Spearman analyses were used to determine the correlations between power-speed-related variables and the CODD. Moreover, independent t-tests and Cohen's d effect size (ES) were used to analyze the differences between the faster and slower players in the CODD. Moderate to strong significant negative correlations were observed between the CODD in the pro-agility test and linear speed at 5 m, 10 m, and 20 m (r = -0.55 to -0.46), while moderate negative significant correlation was found between the zig-zag CODD and SJs (r = -0.37) as well as small positive significant correlation between the CODD in the zig-zag test and the eccentric utilization ratio (EUR) (r = 0.23). Additionally, faster basketball players displayed significantly higher CODD values performing the pro-agility test. In summary, these findings underline the complexity of COD performance and the importance of remodeling traditional training programs in basketball players.

Effects of flywheel resistance training on the running economy of young male well-trained distance runners.

The study aimed to investigate the effect of flywheel accentuated eccentric loading (AEL) training on the running economy (RE) of young male well-trained distance runners. Twenty-two runners participated and were randomly assigned to the flywheel (FG, n = 12) and the control group (CG, n = 10). Traditional endurance training was performed in both groups three times a week for 6-week, while traditional resistance and flywheel AEL training was added to the CG and FG respectively. Subjects performed the incremental exercise test, squat jump, and countermovement jump (CMJ) before and after training. The results showed that 1) the RE at 65% of peak oxygen consumption (VO2peak), 75% VO2peak, and 85% VO2peak improved significantly after 6weeks of training (p < 0.01, Effect size (ES) = 0.76; p < 0.01, ES = 1.04; p < 0.01, ES = 1.85) in FG, and the RE of 85% VO2peak in FG was significantly lower than CG (p < 0.05, ES = 0.30); 2) in post-training, both squat jump (p < 0.01, ES = 0.73) and CMJ (p < 0.01, ES = 1.15) performance, eccentric utilization ratio (p < 0.04, ES = 0.44), the rate of force development (RFD) of squat jump (p < 0.05, ES = 0.46), and CMJRFD (p < 0.01, ES = 0.66) were significantly improved in FG. And there are no significant differents in CG group because it was maintain training for our participants. Our findings showed that 1) flywheel AEL training improves the muscles' explosive strength and other neuromuscular functions, and improves the athlete's running economy under 65%, 75%, and 85% VO2peak, which potentially increases endurance performance. 2) Flywheel AEL training can improve the height, RFD, and the eccentric utilization ratio of squat jump and CMJ, and other lower limb elastic potential energy indicators of the young male, well-trained distance runners.

The Effect of Aquatic Plyometric Training on Jump Performance Including a Four-week Follow-up in Youth Female Volleyball Players.

This study aimed to analyze the effect of aquatic plyometric training (APT) on jump performance in volleyball players. Twelve female athletes (16.6 ± 0.9 years) were assessed through the following jump tests: spike height (SH), squat jump (SJ), countermovement jump (CMJ) and CMJ with an arm swing (CMJA). Jump height in each test and the eccentric utilization ratio (EUR) were the outcome measures. APT consisted of sets of drop jumps for 6 weeks (2 sessions/week) at a water depth of 0.75 m. Tests were performed at the beginning of a five-week pre-season period, before and after APT, and four weeks later for the follow-up. Repeated measures ANOVAs were used to analyze data and Hedges’ g to estimate effect size (ES). Performance of all jumps did not change from baseline to Pre-APT. Performance improved in SH (p < 0.001, ES: 1.09), the SJ (p = 0.045, ES: 0.76) and the CMJA (p < 0.001, ES: 0.78) after APT when compared to Pre-APT. No changes were observed after the follow-up period. In conclusion, including six weeks of APT in the training routine of youth volleyball players improved performance of a sport-specific task (SH), the SJ and CMJA, with gains preserved after a four-week follow-up.

Heart Rate Variability And Its Association With The Autonomic Response During Jump Performance In Female Soccer Players

Heart rate variability (HRV) has been established as a valid index for examining cardiac autonomic modulation. The eccentric utilization ratio (EUR) is a novel index examining the stretch shortening cycle and is calculated by dividing the jump height of both the squat jump and counter movement jump. The reactive strength index (RSI) is another assessment examining the autonomic response of a muscle contraction when performing a drop jump test. Currently, there remains a paucity of inquiry around the association between heightened cardiac vagal modulation and improvement in jump performance when utilizing the stretch shortening cycle. PURPOSE: To examine the association between cardiac vagal modulation using rMSSD and jump performance assessments utilizing the stretch shortening cycle in healthy female collegiate soccer players. METHODS: Seventeen healthy female collegiate soccer players with an age of (mean ± SD) 18.5 ± 0.75 yr, a weight of 57.3 ± 9.2 kg, a height of 165.4 ± 7.2 cm, and a body fat % of 23.2 ± 7.4 volunteered as participants. HRV was analyzed in the supine position after a 10-min stabilization period. R-R intervals were recorded over 60-seconds using the Polar Team Pro® chest strap and were exported into Kubios HRV 3.4 (University of Kuopio, Kuopio, Finland) for HRV analyses. Each participant performed three separate squat jumps, counter movement jumps and drop jumps with their hands placed on their hips. Jump performance was assessed using a force plate (Hawkin Dynamics Force Plate, ME, USA). The highest jump was included for each analysis. Normality of each data set was examined using a Shapiro-Wilk’s test for normality (p > 0.05). Linear regression (R2) was utilized to examine the association between rMSSD and both EUR and RSI. This study was approved by and followed the recommendation of the Research Ethics Review board at Langara College. RESULTS: No significant associations were observed between rMSSD and both EUR (R2 = 0.004, p = 0.74) and RSI (R2 = 0.001, p = 0.87). CONCLUSION: HRV may not be suitable for examining the autonomic response when utilizing the stretch shortening cycle during jump performance testing. This investigation was funded by the Langara College ARC-1 grant.

The Optimal Time Window for Complex Training in Order to Increase Repeated Sprint Ability in Professional Ice Hockey Players

ABSTRACT&#x0D; The goal of this study was to investigate the post-activation performance enhancement (PAPE) and optimal time window following complex training (CT) to increase ice-hockey player skating speed and endurance. Ten professional ice-hockey players (age= 19.8±1.23 years, height= 1.8± 0.06 m, weight= 83.37±4.79 Kg,) from the American Hockey League (AHL, n=7) and the National Hockey League (NHL, n=3) were assigned randomly into two groups. Both groups completedthe same CT training protocol, designed to induce post-activation potentiation (PAP). One group completed the training 8 hours prior to testing (8HPT), and the other 4 hours (4HPT) before testing. The CT PAP training protocol consisted of 3 sets of 5 repetitions of trap high bar deadlifts superset with 6 box jumps on a 20-inch plyometric box. The effect of CT PAP training on performance was assessed using the following testing: the countermovement jump (CMJ), the static squat jump (SSJ), the stationary broad jump (BJ), reactive strength index (RSI), eccentric utilization ratio (EUR), the double leg incremental drop jump tests (DJ), and on ice 40 meter sprint time during the Peterson On-Ice repeated shift Test (POIT). Results showed significant improvements for both groups for the after CT PAP training for the SJ (4HPT: p= 0.04), BJ (8HPT: p= 0.02; 4HPT: p=0.03), POIT (8HPT: Sprint 4, 5, 6, 8: p&lt;0.05; 4HPT: Sprint 2, 3: p&lt;0.05), POIT total sprint time (8HPT: p= 0. 01), mean 40-meter sprint time (8HPT: Sprint 1, 2, 3, 4, 5, 6 and 8: p&lt;0.05; 4HPT: Sprint 2, 3, 4, 5, 6 and 7: p&lt;0.05), and total 40 meter sprint time (8HPT and 4HPT: Sprint 2 p= 0.03). However, no significant difference (p≥0.05) was found following CT PAP training for the CMJ, DJ, and RPE. Thus, the present study suggests that PAP has a greater effect on jumping and on ice-hockey repeated sprint performance when completed 8 hours before. Nonetheless, CT PAP training appears to be beneficial to improve the rate of force development and performance when performed more than 4 hours before the competition in professional North-American ice-hockey players. The present protocol and timing window can be utilized by strength and conditioning specialists to improve on-ice repeated sprint performance of professional ice-hockey players.

Interrelationship between specific high-intensity intermittent efforts ability with aerobic capacity and slow stretch-shortening cycle utilization in taekwondo athletes

BACKGROUND: In taekwondo the ability to repeat high-intensity efforts is characteristic of the sport. The Frequency speed of kick test (FSKT) is frequently used to assess this ability, although its influence on aerobic capacity and dynamic strength characteristics has received less attention in the literature. OBJECTIVE: To examine the relationship between specific high-intensity intermittent efforts with aerobic capacity and slow stretch-shortening cycle utilization in taekwondo athletes. METHODS: Nineteen taekwondo male athletes were assessed by squat jump (SJ), countermovement jump (CMJ), 20-meter shuttle run (20MSR), and frequency speed of kick test multiple (FSKTMULT). From the FSKTMULT, total kicks and kick decrement index [KDI] were calculated. Additionally, from both jump tests, the slow stretch-shortening cycle utilization (Slow SSC Utilization) was determined from the eccentric utilization ratio [EUR], pre-stretch augmentation [PSA], and reactive strength index [RSI]. RESULTS: There were positive and significant correlations between total kicks with 20MSR (r= 0.85; p= 0.00) and SJ (r= 0.66; p&lt; 0.05). The multiple regression model demonstrated that total kicks where significantly influenced by 20MSR (R2= 71%; p= 0.00). Additionally, only EUR and RSI explained total kicks performance to a greater proportion (R2= 76%). CONCLUSIONS: The FSKTMULT total kicks performance is positively correlated and influenced by aerobic capacity and slow SSC utilization.

Low-Load Blood Flow Restriction Squat as Conditioning Activity Within a Contrast Training Sequence in High-Level Preadolescent Trampoline Gymnasts.

To investigate the effects of implementing low-load blood flow restriction exercises (LL-BFRE) instead of high-load exercises (HL-RE) in a contrast training program on strength and power performance of high-level young gymnasts. Fifteen high-level pre-pubescent trampoline gymnasts (national level, Tanner Stage II, intermediate experience in strength training) were divided into two groups to complete the same structure of a ten-week contrast strength training program differing only in the configuration of the first resistance exercise of the contrast sequence. The LL-BFRE group (n = 7, four girls, 13.9 ± 0.4 y) performed the first resistance exercise of the contrast with LL-BFRE (20%–30% 1RM, perceived pressure of 7 on a scale from 0 to 10). The HL-RE group (n = 8, four girls, 13.8 ± 0.5 y) trained the first resistance exercise of the contrast sequence with moderate-to-high load (60%–85% 1RM). Before and after the training period, isometric mid-thigh pull (IMTP), squat jump (SJ), counter movement jump (CMJ), and drop-jump (DJ) were performed to evaluate the effect of the intervention on strength and power capacities as primary outcomes. Changes in participants’ anthropometric measures, muscle mass, left and right thigh girth, IMTP relative to bodyweight (IMTP-R), eccentric utilization ratio (EUR), and reactive strength index (RSI) were assessed as secondary outcomes. There was no significant interaction (p > 0.05) between group x time in any power and strength outcome, although SJ and EUR showed a trend to significant interaction (p = 0.06 and p = 0.065, respectively). There was an overall effect of time (p < 0.05) in all power and strength variables (CMJ, SJ, EUR, DJ, RSI, IMTP, and IMTP-R). There was a significant interaction in muscle mass (MM) [β = 0.57 kg, 95% CI = (0.15; 0.98), t13 = 2.67, p = 0.019], revealing that participants in LL-BFRE increased their muscle mass (6.6 ± 3.1%) compared to HL-RE (3.6 ± 2.0%). Anthropometric variables did not present any group or interaction effect. However, there was a time effect (p < 0.05). Implementing LL-BFRE in place of HL-RE as a conditioning activity in a contrast training sequence might be equally effective in improving lower-body strength and power in preadolescent trampoline gymnasts.

A Brief Review of Selected Biomechanical Variables for Sport Performance Monitoring and Training Optimization

Traditional neuromuscular tests (e.g., jumping and sprinting tasks) are useful to assess athletic performance, but the basic outcomes (e.g., jump height, sprint time) offer only a limited amount of information, warranting a more detailed approach to performance testing. With a more analytical approach and biomechanical testing, neuromuscular function can be assessed in-depth. In this article, we review the utility of selected biomechanical variables (eccentric utilization ratio, force–velocity relationship, reactive strength index, and bilateral deficit) for monitoring sport performance and training optimization. These variables still represent a macroscopic level of analysis, but provide a more detailed insight into an individual’s neuromuscular capabilities, which can be overlooked in conventional testing. Although the aforementioned “alternative” variables are more complex in biomechanical terms, they are relatively simple to examine, with no need for additional technology other than what is already necessary for performing the conventional tests (for example, even smartphones can be used in many cases). In this review, we conclude that, with the exception of the eccentric utilization ratio, all of the selected variables have some potential for evaluating sport performance.

Questionable Utility of the Eccentric Utilization Ratio in Relation to the Performance of Volleyball Players.

The difference between squat jump (SJ) and countermovement jump (CMJ), termed eccentric utilization ratio (EUR), is frequently suggested as an outcome that can be used in athletic training design. Unlike performance in SJ and CMJ, which is associated with sports performance, the association between EUR and sports performance is almost unexplored. This study aimed to investigate whether EUR is associated with performance in approach jump, linear sprint and change of direction (CoD) tasks in volleyball players. Forty-five male volleyball players performed SJ, CMJ, 25 m linear sprint, approach jump and two CoD tasks (505 test and modified T-test). EUR was calculated based on jump height, peak power, peak force and average power. SJ and CMJ variables showed moderate to high correlation with approach jump performance (r = 0.42–0.70), small correlation with modified T-test (r = 0.33–0.40) and small to moderate correlation with sprint time (r = 0.35–0.49). EUR showed only small associations with performance variables (r = 0.31–0.34). In all linear regression models with performance outcomes as dependent variables, the CMJ height was always the only statistically significant predictor. Our results support the recent arguments that the EUR offers limited insight into the neuromuscular capabilities of athletes.

The relationship between vertical stiffness during bilateral and unilateral hopping tests performed with different strategies and vertical jump performances

ABSTRACT Vertical stiffness has been highlighted as a potential determinant of performance and may be estimated across a range of different performance tasks. The aim of the current study was to investigate the relationship between vertical stiffness determined during 9 different hopping tests and performance of vertical jumps. Twenty healthy, active males performed vertical hopping tests with three different strategies (self-selected, maximal, and controlled) and three different limb configurations (bilateral, unilateral preferred, and unilateral non-preferred), resulting in nine different variations, during which vertical stiffness was determined. In addition, participants performed squat jump (SQJ) and countermovement jump (CMJ) during which jump height, CMJ stiffness, and eccentric utilization ratio (EUR) were determined. Vertical stiffness in bilateral and unilateral preferred tasks performed with a self-selected and maximal, but not controlled, strategy was associated with stiffness in the CMJ (r = 0.61–0.64; p < 0.05). However, stiffness obtained during unilateral preferred and non-preferred hopping with self-selected strategy was negatively associated with performance in SQJ and CMJ tasks (r = −0.50 to −0.57; p < 0.05). These findings suggest that high levels of vertical stiffness may be disadvantageous to static vertical jumping performance. In addition, unilateral hopping with a self-selected strategy may be the most appropriate task variation if seeking to determine relationships with vertical jumping performance. Highlights Stiffness obtained during unilateral hopping with a preferred strategy was negatively associated with vertical jumping performances Stiffness obtained during hopping with preferred and maximal strategies was associated with stiffness obtained during a countermovement jump In this population, hopping stiffness may therefore be reflective of an individual's countermovement jump strategy High levels of stiffness may be disadvantageous to static-start vertical jumping

Physiological Predictors of Maximal Incremental Running Performance.

PurposeThe aim of this study was to verify whether physiological components [vertical jumps (Squat Jump – SJ and Countermovement Jump – CMJ), eccentric utilization ratio (EUR) of vertical jumps, running economy (RE), metabolic cost (CMET), first and second ventilatory threshold (VT1 and VT2) maximal oxygen uptake (VO2MAX)] can predict maximal endurance running performance.MethodsTwenty male runners performed maximal vertical jumps, submaximal running at constant speeds, and maximal incremental running test. Before, we measured anthropometric parameters (body mass and height) and registered the training history and volume. SJ and CMJ tests were evaluated prior to running tests. Initially, the oxygen uptake (VO2) was collected at rest in the orthostatic position for 6 min. Soon after, a 10-min warm-up was performed on the treadmill at 10 km⋅h–1, followed by two 5-min treadmill rectangular tests at 12 and 16 km⋅h–1 monitored by a gas analyzer. After that, the runners performed a maximal incremental test, where the VT1, VT2, and VO2MAX were evaluated, as well as the maximum running speed (vVO2MAX). Thus, RE and CMET were calculated with data obtained during rectangular running tests. Multivariate stepwise regression analyses were conducted to measure the relationship between independent variables (height and power of SJ and CMJ, EUR; RE and CMET 12 and 16 km⋅h–1; VT1, VT2, and VO2MAX), as predictors of maximal running performance (vVO2MAX), with significance level at α = 0.05.ResultsWe found that VO2MAX and RE at 16 km⋅h–1 predict 81% of performance (vVO2MAX) of endurance runners (p < 0.001).ConclusionThe main predictors of the maximal incremental running test performance were VO2MAX and RE.

Lower Extremity Stiffness in Collegiate Distance Runners Pre- and Post-Competition

Previous evidence has suggested that there is a relationship between leg stiffness and improved running performance. The purpose of this investigation was to determine how leg stiffness of runners was influenced in the 24 and 48 hour period following a cross country race. Twenty-two collegiate cross-country runners (13 males, 9 females, 19.5 ± 1.4 yr) were recruited and participated in the study. Leg stiffness was assessed 24 hours before and after a race as well as 48 hours post-race. Three jumping protocols were conducted: 1) a static jump, 2) a countermovement jump, and 3) a vertical hopping test. Two embedded force plates (1000 Hz) were utilized to measure ground reaction forces for each test and a metronome was utilized to maintain hopping frequency (2.2 Hz). A significant main effect was found for a static jump, a countermovement jump and leg stiffness. Leg stiffness was significantly reduced 24 hours post-race (pre-race 36.84 kN·m-1, 24h post 33.11 kN·m-1, p < 0.05), but not 48 hours post-race (36.30 kN·m-1). No significant differences were found in post-hoc analysis for the squat jump, countermovement jump height and the eccentric utilization ratio. Following a cross-country race, leg stiffness significantly declined in a group of collegiate runners in the immediate 24 hours post-race, but returned to baseline 48 hours post-race. Sport scientists and running coaches may be able to monitor leg stiffness as a metric to properly prescribe training regiments.