Countermovement Jump Performance Research Articles

Influence of musculoskeletal injury history on countermovement jump performance in rugby players

ObjectiveTo 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). MethodsThirty 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. ResultsRugby 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 with 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. ConclusionsThere 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.

Impact of temperature on physical and cognitive performance in elite female football players during intermittent exercise.

There is limited research on female football players, especially related to their physical and cognitive performance under different climactic conditions. We analyzed the impact of a hot environmental temperature on physical performance and anticipation in elite female football players during a fatigue-inducing intermittent protocol. Elite female players (n = 21) performed the countermovement jump (CMJ) and responded to filmed sequences of offensive play under two distinct environmental temperatures (i.e., mild environment temperature- 20°C and 30% rh versus hot environment temperature- 38°C and 80% rh), interspersed by 1-week interval. Linear mixed models were used. CMJ performance declined following the intermittent protocol on both temperature conditions (p < 0.05). Moreover, there were significant main effects for protocol on CMJ speed (m/s) (p = 0.001; ηp 2 = 0.12), CMJ power (p = 0.002; ηp 2 = 0.11), and CMJ Heightmax (p = 0.002; ηp 2 = 0.12). After performing the intermittent protocol, exposure to a hot temperature caused a greater decline in anticipation accuracy (mild temperature = 64.41% vs. hot temperature = 53.44%; p < 0.001). Our study shows impaired performance in elite female football players following an intermittent protocol under hot compared with mild environmental conditions. We report decreased performance in both CMJ and anticipation performance under hotter conditions. The results reveal that exposure to hot temperatures had a negative effect on the accuracy of their anticipatory behaviors. We consider the implication of the work for research and training interventions.

Monitoring bar velocity to quantify fatigue in resistance training.

We analyzed the effects of load magnitude and bar velocity variables on sensitivity to fatigue. Seventeen resistance-trained men (age=25.7±4.9 years; height=177.0±7.2 cm; body mass=77.7±12.3 kg; back-squat 1RM=145.0±33.9 kg; 1RM/body mass=1.86) participated in the study. Pre- and post-exercise changes in the mean propulsive velocity (MPV) and peak velocity (PV) in the back-squat at different intensities were compared with variations in the countermovement jump (CMJ). CMJ height decreased significantly from pre- to post-exercise (∆%=-7.5 to -10.4; p<0.01; ES=0.37 to 0.60). Bar velocity (MPV and PV) decreased across all loads (∆%=-4.0 to -12.5; p<0.01; ES=0.32 to 0.66). The decrease in performance was similar between the CMJ, MPV (40% and 80% 1RM; p=1.00), and PV (80% 1RM; p=1.00). The magnitude of reduction in CMJ performance was greater than MPV (60% 1RM; p=0.05) and PV (40% and 60% 1RM; p<0.01) at the post-exercise moment. Low systematic bias and acceptable levels of agreement were only found between CMJ and MPV at 40% and 80% 1RM (bias=0.35 to 1.59; ICC=0.51 to 0.71; CV=5.1% to 8.5%). These findings suggest that the back-squat at 40% or 80% 1RM using MPV provides optimal sensitivity to monitor fatigue through changes in bar velocity.

The Association of Age, Sex, and BMI on Lower Limb Neuromuscular and Muscle Mechanical Function in People with Multiple Sclerosis

(1) Background: The countermovement jump (CMJ) on a force plate could be a sensitive assessment for detecting early lower-limb muscle mechanical deficits in the early stages of multiple sclerosis (MS). CMJ performance is known to be influenced by various anthropometric, physiological, and biomechanical factors, mostly investigated in children and adult athletes. Our aim was to investigate the association of age, sex, and BMI with muscle mechanical function using CMJ to provide a comprehensive overview of lower-limb motor function in people with multiple sclerosis (pwMS). (2) Methods: A cross-sectional study was conducted with pwMS (N = 164) and healthy controls (N = 98). All participants performed three maximal CMJs on a force plate. Age, sex, and BMI were collected from all participants. (3) Results: Significant age, sex, and BMI effects were found for all performance parameters, flight time, and negative and positive power for pwMS and HC, but no significant interaction effects with the group (pwMS, HC) were detected. The highest significant effects were found for sex on flight time (η2 = 0.23), jump height (η2 = 0.23), and positive power (η2 = 0.13). PwMS showed significantly lower CMJ performance compared to HC in middle-aged (31–49 years), with normal weight to overweight and in both women and men. (4) Conclusions: This study showed that age, sex, and BMI are associated with muscle mechanical function in pwMS and HC. These results may be useful in developing reference values for CMJ. This is a crucial step in integrating CMJ into the diagnostic assessment of people with early MS and developing individualized and effective neurorehabilitative therapy.

Residual Effects of Same Day Lower Extremity Strength Training on Countermovement Jump Performance in Collegiate Women Athletes.

Balancing of strength programming intensity with sport demands is necessary to avoid excessive workloads that could inhibit performance. To expand previous jump height focused literature, this study evaluated whether countermovement jump (CMJ) movement strategies, including eccentric characteristics, might reveal CMJ execution strategy shifts to achieve similar afternoon CMJ height following a morning resistance training session (RTS). Fifteen collegiate women's soccer and volleyball athletes (18-24 years, 73.6 ± 8.4 kg, 1.74 ± 0.19 m) participating in an offseason RTS completed five CMJs during two afternoon sessions (48 h apart), one 4-6 h post morning RTS, and one on a rest day. The RTS consisted of 2 sets of 10 repetitions at 70-80% 1RM for the back squat, the front squat, and the forward lunge. Vertical ground reaction forces were recorded from which 13 outcome measures describing elements of the eccentric and concentric CMJ phases were computed. No significant differences in jump height (p = 0.427, d = 0.17) or outcome measures (p = 0.091-0.777, d = -0.07-0.21) between sessions with exception of a significant concentric phase time decrease (p = 0.026, d = 0.23) following the RTS were identified. Given the magnitude of the mean concentric phase time change (0.01 s), the result likely has limited practical meaning. As these results confirm previous CMJ height literature, practitioners have further evidence that a morning RTS does not interfere or enhance afternoon CMJ performance in athletic women.

Biomechanical load quantification of national and regional soccer players with an inertial sensor setup during a jump, kick, and sprint task: assessment of discriminative validity

Training load quantification methods may help optimize soccer performance. However, whole-body indicators potentially underestimate biomechanical load. A new inertial sensor setup allows joint-specific biomechanical load quantification. Good discriminative validity further supports the use of this method, and therefore the purpose of this study is to assess the discriminative validity of this method during soccer-specific activities. Twelve national and sixteen regional soccer players wore an inertial sensor setup and performed countermovement jumps, soccer kicks, and 30 m sprints. Between-group differences in angular acceleration-based biomechanical load indicators Knee Load, Hip Load, and performance were assessed using MANOVAs and Cohen’s effect sizes. Furthermore, relationships with performance were explored. National players showed higher Knee Load during jumping (mean difference: 0.11 A.U., ES = 0.93, p = 0.02), kicking (mean difference: 1.94 A.U., ES = 0.94; p = 0.02), and almost during sprinting (mean difference: 12.85, ES = 0.77; p = 0.05). Hip Load did not differ between groups across all tasks, although national players outperformed regional players on all tests. Significant relationships between Knee Load (rjump = 0.41, rkick = 0.65), Hip Load (rjump = 0.42), and performance were observed with 95% confidence intervals ranging from trivial to large. The results confirm discriminative validity of Knee Load for jumping and kicking, but not for sprinting and Hip Load in general. The confidence intervals of the established relationships suggest that the biomechanical loads might not entirely explain between-group differences in performance. The results can be used as reference values for biomechanical load quantification in the field.

Effects of focal vibration on changes in sports performance in amateur athletes: A randomized clinical trial.

The aim of this study was to evaluate the effectiveness of a focal vibration protocol added to an activation protocol with active muscle contractions and to see what repercussions it has on sprint, countermovement jump (CMJ), and lower limb isometric strength. A double-blind randomized clinical trial was conducted in the Functional Anatomy Laboratory and the sample consisted of 70 athletes. The main outcome measures were knee extension force, CMJ, sprint, and surface electromyography. Repeated-measures analysis of variance revealed significant improvements. They were found in the within-group analysis for the Experimental Group in the isometric extension force (p < 0.001; η2 = 0.368), CMJ (p < 0.001; η2 = 0.301) and 30 m sprint (p < 0.001; η2 = 0.376). In the electromyography, there are changes in the Sham Group in all muscles, in CMJ and Sprint tests, and no differences in the Experimental Group, except for the RF muscle. In the between-group analysis, statistically significant differences were found only in favor of the Experimental Group in CMJ (p = 0.017; η2 = 0.81) and 30 m sprint (p < 0.001; η2 = 0.152). These results confirm a significant improvement in the sprint, CMJ performance, and quadriceps strength, after a focal vibration protocol, added to a muscle active contraction, compared to a focal vibration sham protocol. Therefore, our results suggest that the focal vibration can be a very useful tool in sports involving high-powered actions.

Test-retest reliability of lower limb muscle strength, jump and sprint performance tests in elite female team handball players.

This study aimed to assess the reliability of lower limb muscle function (knee extensor/flexor peak torque, rate of torque development (RTD), impulse, and countermovement jump (CMJ) performance) and sprint performance (acceleration capacity). CMJ performance was evaluated on a force plate. MVIC, RTD and impulse variables were investigated using a portable isometric dynamometer and sprint performance was assessed with dual-beam photocells in elite female athletes. CMJ test variables maximal vertical jump height, peak and mean power, concentric work, and body center of mass displacement demonstrated good-to-excellent test-retest correlations between Test 1 and Test 2 (ICC ≥ 0.70, CWw-s = 3.4-11.0%). Peak MVIC torque for the knee extensors and flexors demonstrated excellent test-retest correlations (both ICC = 0.84) along with CVw-s values of 6.8 and 6.0%, respectively. Late-phase (0-100ms, 0-200ms) RTD for the knee flexors demonstrated excellent test-retest correlations (ICC = 0.89-0.91, CVw-s = 4.8-8.5%). Sprint times at 10- and 20-m demonstrated excellent test-retest reproducibility (ICC = 0.83 and ICC = 0.90, respectively) with CVw-s values of 1.9 and 1.5%. For 5-m sprint times, test-retest reproducibility was good (ICC = 0.71) with CVw-s of 2.8%. Sprint testing performed while dribbling a handball improved (p < 0.05) from test to retest at 5-, 10- and 20-m. In conclusion, the force plate, the mobile isometric dynamometer, and dual-beam photocells provide reproducible tools for field-based testing of countermovement jump performance, knee extensor and flexor strength and sprint performance.

Dose-Response Effect of an Inertia Flywheel Postactivation Performance Enhancement Protocol on Countermovement Jump Performance.

The purpose of this study was to investigate the dose-response effect of a high-load, 6-repetition, maximum effort inertial flywheel (IFw) squat postactivation performance enhancement (PAPE) protocol on countermovement jump (CMJ) performance metrics. Thirteen subjects completed 5 squat testing sessions: 1 session to determine back-squat 6-repetition maximum, 1 session to determine 6-repetition maximum IFw load, and 3 sessions to investigate the dose-response effect of an IFw PAPE protocol set at the load determined in the second session. In the IFw PAPE sessions, subjects completed either 1, 2, or 3 sets of IFw squats, then performed 5 CMJs over 12minutes (1, 3, 6, 9, and 12min post-IFw). All CMJ tests were conducted on a force platform where CMJ performance outcomes and impulse variables were calculated. There was no main time or volume effect for jump height, contact time, reactive strength index, peak force, or any of the impulse variables. A main time effect was identified for flight time (P = .006, effect size = 0.24) and peak power (P = .001, effect size = 0.28). The lack of change in jump height may indicate that too much fatigue was generated following this near-maximal IFw squat protocol, thereby reducing the PAPE effect.

Nocturnal Smartphone Use Affects Sleep Quality and Cognitive and Physical Performance in Tunisian School-Age Children.

Nocturnal smartphone use emits blue light, which can adversely affect sleep, leading to a variety of negative effects, particularly in children. Therefore, the present study aimed to determine the effect of acute (AC) (one night) and repeated (RC) (five nights) nocturnal smartphone exposure on sleep, cortisol, and next-day performance in Tunisian children. Thirteen participants (seven girls and six boys, age 9 ± 0.6, height 1.32 ± 0.06, weight 34.47 ± 4.41) attended six experimental nights. The experiment started with a baseline night (BL) with no smartphone exposure, followed by repeated sessions of nocturnal smartphone exposure lasting 90 minutes (08:00 pm-09:30 pm). Actigraphy; salivary cortisol; the Stroop test (selective attention); choice reaction time (CRT); N-back (working memory); counter-movement jump (CMJ), composed of flight time (time spent in the CMJ flight phase) and jump height; and a 30 m sprint were assessed the morning after each condition. Both AC and RC shortened total sleep time (TST) (p < 0.01), with a greater decrease with RC (-46.7 min, ∆% = -9.46) than AC (-28.8 min, ∆% = -5.8) compared to BL. AC and RC significantly increased waking after sleep onset (3.5 min, ∆% = 15.05, to 9.9 min, ∆% = 43.11%) and number of errors made on the Stroop test (1.8 error, ∆% = 74.23, to 3.07 error, ∆% = 97.56%). Children made 0.15 and 0.8 more errors (∆% = 6.2 to 57.61%) and spent 46.9 s and 71.6 s more time on CRT tasks (∆% = 7.22 to 11.11%) with AC and RC, respectively, compared to BL. The high-interference index of the Stroop task, CMJ performance, and 30 m sprint speed were only altered (p < 0.01) following RC (0.36, Δ% = 41.52%; -34 s, Δ% = -9.29%, for flight time and -1.23 m, -8.72%, for jump height; 0.49 s, Δ% = 6.48, respectively) when compared to BL. In conclusion, one- or five-night exposure to smartphones disturbed the children's sleep quality and their performance, with more pronounced effects following RC.

Influence of different verbal cue types on countermovement jump performance in youth female athletes

Although external (EXT) verbal cues have been shown to improve jump performance, limited research has been conducted in youth athletes. Therefore, the purpose of this study was to investigate how different EXT verbal cue types influenced countermovement jump (CMJ) performance in youth athletes. Ten young trained female athletes (16.80 ± 0.60 years) performed the CMJ using four different EXT verbal cues including external-distal (DIST), external-proximal (PROX), analogy (ANA) and holistic (HOL) as well as a neutral cue (CON). Jump height, reactive strength index modified (RSIMOD), countermovement depth, jump time and force-time measures from eccentric and concentric CMJ subphases were measured. No significant differences between cue types were found for RSIMOD. ANA resulted in significantly higher jump height compared to CON ( g = 0.37). PROX significantly increased jump time ( g = 0.60), concentric time ( g = 0.47) and braking time ( g = 0.52), as well as significantly decreasing eccentric braking mean force ( g = 0.43) and eccentric braking rate of force development ( g = 0.59) compared to CON. Countermovement depth significantly increased when using PROX ( g = 0.60), HOL ( g = 0.46) and ANA ( g = 0.51) compared to CON. These results suggest that compared to a neutral cue, EXT verbal cues result in similar CMJ performance in trained youth athletes. However, PROX verbal cues appear to result in reduced performance in many CMJ force-time measures.

Fat-free mass mediates the association between body mass and jump height in healthy young adults.

The countermovement jump (CMJ) is a reliable and valid test of lower-extremity (LE) muscle power and neuromuscular performance. Body mass is positively associated with CMJ performance in young adults, warranting the examination of the influence of body composition on jump height (JH). This study examined the mediation effects of body composition on CMJ performance in young adults. The hypothesis was that fat-free mass and percent fat mass would significantly mediate the association between body mass with JH in young adults. Healthy young adults (N.=81; 47 female; mean age 25.1±3.4) completed this study and underwent body composition assessment using a bioelectrical impedance analysis device. Participants performed three CMJ trials to measure average JH using an electronic jump mat. Mediation analysis models were performed to examine the hypothesis of this study. The mediation analyses indicated that the indirect effects of fat-free mass on the association between body mass with JH were significant (indirect effect [IE]=-0.23, 95% CI -0.315, 0.767; IE=0.76, 95% CI 0.334, 1.272; respectively), after controlling for sex and percent fat mass. The association between body mass with JH in young adults with normal BMI was mediated by fat-free mass. Clinicians, trainers, and coaches should potentially target increasing fat-free mass when improving LE power and neuromuscular performance in rehabilitation and sports settings in this population, but further studies are needed.

The repeated bout effect of traditional resistance training on cycling efficiency and performance.

This study examined the repeated bout effect of two resistance training bouts on cycling efficiency and performance. Ten male resistance-untrained cyclists (age 38 ± 13years; height 180.4 ± 7.0cm; weight 80.1 ± 10.1; kg; VO2max 51.0 ± 7.6ml.kg-1.min-1) undertook two resistance training bouts at six-repetition maximum. Blood creatine kinase (CK), delayed-onset of muscle soreness (DOMS), counter-movement jump (CMJ), squat jump (SJ), submaximal cycling and time-trial performance were examined prior to (Tbase), 24 (T24) and 48 (T48) h post each resistance training bout. There were significantly lower values for DOMS (p = 0.027) after Bout 2 than Bout 1. No differences were found between bouts for CK, CMJ, SJ and submaximal cycling performance. However, jump height (CMJ and SJ) submaximal cycling measures (ventilation and perceived exertion) were impaired at T24 and T48 compared to Tbase (p < 0.05). Net efficiency during submaximal cycling improved at Bout 2 (23.8 ± 1.2) than Bout 1 (24.3 ± 1.0%). There were no changes in cycling time-trial performance, although segmental differences in cadence were observed between bouts and time (i.e. Tbase vs T24 vs T48; p < 0.05). Cyclists improved their cycling efficiency from Bout 1 to Bout 2 possibly due to the repeated bout effect. However, cyclists maintained their cycling completion times during exercise-induced muscle damage (EIMD) in both resistance training bouts, possibly by altering their cycling strategies. Thus, cyclists should consider EIMD symptomatology after resistance training bouts, particularly for cycling-specific technical sessions, regardless of the repeated bout effect.

Post-Activation Performance Enhancement of Punch Force and Neuromuscular Performance in Amateur Boxing: Toward a More Individualized and "Real-World" Approach.

Finlay, MJ, Greig, M, Bridge, CA, and Page, RM. Post-activation performance enhancement of punch force and neuromuscular performance in amateur boxing: Toward a more individualized and "real-world" approach. J Strength Cond Res XX(X): 000-000, 2023-Previous research on post-activation performance enhancement has been applied in several sporting settings, although this is lacking in a boxing setting. This study explored the effectiveness of 2 upper-body conditioning activities in improving punch-specific performance during an amateur boxing-simulated bout. On 3 separate occasions, 10 male senior elite amateur boxers performed the following conditioning activities before a boxing-specific simulation protocol: isometric (ISO) punch, elastic resistance (ER) punch, and a control trial. Boxers performed maximal punches against a vertically mounted force plate, and countermovement jumps (CMJ) at baseline, before round 1, after each round, and 4 minutes after the simulation. Both conditioning activities, but not the control trial, produced small worthwhile increases (effect size ≥ 0.20; equal to or greater than the smallest worthwhile change) in punch force, although worthwhile increases in rate of force development were limited to the cross during the ISO trial. No group-based improvements in CMJ performance were observed. Individual analysis revealed that 6 boxers improved punch-specific performance to the greatest extent in the ISO trial; in contrast, only 1 boxer did so in the ER trial. Three boxers exhibited similar performance increases across trials. In conclusion, both conditioning activities may be applied to an amateur boxer's warm-up to acutely enhance punch-specific performance. The ISO conditioning activity seems most effective; however, the interindividual variability suggests a need for protocols to be individualized to each athlete. The conditioning activities in the present study may be applied to sparring, competitive bouts, or to other combat sports.

Recovery and stress monitoring in elite ice hockey: A longitudinal pilot-study

Introduction&#x0D; Young athletes in high-level sports experience a greater risk for injury and illness during phases of increased training and competitive load. When recovery is too sparse under these circumstances, psychological and physical health problems could emerge. These are referred to as nonfunctional overreaching or overtraining syndrome, OTS (Daly et al., 2022; Jones et al., 2017; Kiely, 2018). OTS is typically characterized by a reduction in athletic performance that lasts for several weeks to months, accompanied with mood and sleep disturbances, feelings of depression, respiratory tract infections, weight loss, and other symptoms. The prevalence of this condition is high with approxymately 10-20 % of young adult and about 29 % of young athletes from various sports beeing affected (Matos et al., 2011). To our knowledge, no scientifically valid and reliable measurement system currently exists, which would allow the preventive, early diagnosis of overreaching states that might lead to OTS (Weakley et al., 2022). The aim of this study is to develop and evaluate a multiparameter measurement system to assess the recovery and stress state of high-level athletes.&#x0D; Methods&#x0D; Twenty-five male ice hockey players from the highest level Swiss leagues at their respective age group participated (i.e., National League, NL, n = 11, age = 24.8 ± 4.1 years and U20, n = 14, age = 18.5 ± 1.5 years). Over 5-10 weeks during the in-season (i.e., competition phase) measurements were performed on 10 separate days, either after 1 day of passive recovery (T1) or after a day with match/intensive training (T2). The measurement battery included counter movement jump (CMJ), heart rate variability (HRV), executive functions (EF), tympanic temperature (Temp), and Stress Recovery Short Scale (SRSS).&#x0D; Results&#x0D; Independent Student’s t-tests showed significant differences (p &lt; 0.05) between timepoints T1 and T2 for CMJ (peak power per body mass), HRV (sympathic and parasympatic indexes), and SRSS (recovery, stress, total score); but not for CMJ (jump height), EF and Temp.&#x0D; Discussion/Conclusion&#x0D; We conclude that various measurment parameters, including CMJ performance, HRV indices, and subjective ratings of recovery and stress could provide valuable feedback for athletes, coaches, and medical staff regarding a potential overreaching or OTS state.&#x0D; References&#x0D; Daly, E., Pearce, A. J., Esser, P., &amp; Ryan, L. (2022). Evaluating the relationship between neurological function, neuromuscular fatigue, and subjective performance measures in professional rugby union players. Frontiers in Sports and Active Living, 4, Article 1058326. https://doi.org/10.3389/fspor.2022.1058326&#x0D; Jones, C. M., Griffiths, P. C., &amp; Mellalieu, S. D. (2017). Training load and fatigue marker associations with injury and illness: A systematic review of longitudinal studies. Sports Medicine, 47(5), 943-974. https://doi.org/10.1007/s40279-016-0619-5&#x0D; Kiely, J. (2018). Periodization theory: Confronting an inconvenient truth. Sports Medicine, 48(4), 753-764. https://doi.org/10.1007/s40279-017-0823-y&#x0D; Matos, N. F., Winsley, R. J., &amp; Williams, C. A. (2011). Prevalence of nonfunctional overreaching/overtraining in young English athletes. Medicine &amp; Science in Sports &amp; Exercise, 43(7), 1287-1294. https://doi.org/10.1249/MSS.0b013e318207f87b&#x0D; Weakley, J., Halson, S. L., &amp; Mujika, I. (2022). Overtraining syndrome symptoms and diagnosis in athletes: Where is the research? A systematic review. International Journal of Sports Physiology and Performance, 17(5), 675-681. https://doi.org/10.1123/ijspp.2021-0448

Kinetic Analysis, Potentiation, and Fatigue During Vertical and Horizontal Plyometric Training: An In-Depth Investigation Into Session Volume.

To investigate vertical and horizontal jump kinetic performance following a low-volume plyometric stimulus with progressively increased session jump volume. Sixteen academy rugby players (20.0 [2.0]y; 103.0 [17.6]kg; 184.3 [5.5]cm) volunteered for this study. Vertical and horizontal jump sessions were conducted 1 week apart and consisted of a 40-jump low-volume plyometric stimulus using 4 exercises, after which volume was progressively increased to 200 jumps, using countermovement jump (CMJ) for vertical sessions and horizontal broad jump (HBJ) for horizontal sessions. Jump performance was assessed via force-plate analysis at baseline (PRE-0), following the low-volume plyometric stimulus (P-40), and every subsequent 10 jumps until the end of the session (P-50, P-60, P-70, . . . P-200). The low-volume stimulus was effective in potentiating HBJ (2% to 5%) but not CMJ (0% to -7%) performance (P < .001). The HBJ performance enhancements were maintained throughout the entire high-volume session, while CMJ realized small but significant decrements (-5% to -7%) in jump height P-50 to P-80 before recovering to presession values. Moreover, increases in eccentric impulse (5% to 24%; P < .001) in both sessions were associated with decreased or maintained concentric impulse, indicating a breakdown in performance-augmenting mechanisms and less effective power transfer concentrically after moderate volumes. Practitioners should consider kinetic differences between HBJ and CMJ with increasing volume to better inform and understand session dosing strategies.

Validity and reliability of a single-beam sensor for assessment of jump performance

This study aimed to establish the validity and reliability of a single-beam sensor for assessment of jump performance. Thirty-four male and female university students (age: 21.47 ± 0.98 years; height: 173.97 ± 9.32 cm; weight: 70.03 ± 10.63 kg) executed three trials of countermovement jump (CMJ) and three trials of squat jump (SJ), respectively. CMJ and SJ were simultaneously recorded using a force platform (reference) and single- beam jump sensor (Jump Pro). The flight time (FT) and jump height (JH) for both jumps were utilized for analyses. Results revealed the following for FT in CMJ performance: 1) Pearson’s correlation coefficient (r) with lower limit (LL) and upper limit (UL) = 0.90 (0.82, 0.94); 2) Typical error of estimate (TEE) with LL and UL = 0.03 (0.01, 0.02); 3) Bland-Altman estimate = 0.05; and 4) Intraclass correlation coefficient (ICC) = 0.80. On the other hand, JH in CMJ posted: 1) r = 0.96 (0.94, 0.98); 2) TEE = 2.07 (1.73, 2.62); 3) Bland-Altman estimate = 4.00; and 4) ICC = 0.71. In regards to FT in SJ, r = 0.96 (0.94, 0.98), TEE = 0.02 (0.01, 0.02), Bland-Altman estimate = 0.03, and, ICC = 0.88. Further, JH in SJ exhibited r = 0.96 (0.94 – 0.98), TEE = 1.84 (1.53, 2.32), Bland-Altman estimate = 3.55, and ICC = 0.86. These findings support Jump Pro as a valid and reliable tool for measurement of CMJ and SJ performances.

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.

Countermovement-Jump and Pull-Up Performance Before and After a Swimming Race in Preparatory and Competitive Phases of a Swimming Season.

Monitoring performance athletes' training responses can be efficiently completed at competitive events. This study aimed to explore the changes in swimming, countermovement-jump (CMJ), and pull-up (PU) performance following training across a competitive phase, as well as immediately before and after each race. Fourteen well-trained male sprint/middle-distance swimmers (height 179 [7]cm, mass 70 [8]kg, age 18 [2]y), from 3 regional training groups, completed CMJ and PU tests before and after the national competitions in October and May, when race performance was also assessed. Swimming race performance was significantly improved from before the national competitions in October to after the national competitions in May (1.8% [3.2%], P = .044, d = 0.60, moderate effect). Although there were no significant changes in PU velocity, CMJ performance significantly improved from before the national competitions in October to after the national competitions in May (mean difference 2.29cm, P = .004, d = 3.52) and showed before-to-after race decreases (mean difference -1.64cm, P = .04, d = 2.28). Swimming performance and CMJ performance improved as the season progressed, although these improvements were not directly correlated. PU performance did not appear to be sensitive to training or race-induced fatigue, in contrast to CMJ, in this group of male swimmers.

Somatotype and Body Composition of Indian Male and Female Swimmers, and their Relationship to Countermovement Jump Performance

Introduction: The aim of this study was:1) to ascertain the anthropometric characteristics of Indian swimmers and 2) to investigate the potential association between these characteristics and countermovement jump metrics. Method: Forty-two national level Indian swimmers (18 females and 24 males) who regularly compete in national and/or international competitions, took part in the study. Anthropometric measurements were performed for body mass, stature, 8 skinfold sites, 3 girths, and 2 breadths. Somatotypes, body fat %, fat mass and lean body mass for all athletes were also calculated. A CMJ test was performed to measure vertical jump height, peak power output, and relative peak power output. Results: The Pearson correlation analysis of body composition variables and CMJ measures revealed a very large negative association between body fat percent and vertical jump height (R = - 0.726; p = 0.000) and between body fat percent and relative peak power (R = -0.757; p = 0.000); a large negative association between body fat percent and peak power (R = - 0.577; p = 0.000) and between fat mass and relative peak power (R = -0.560, p = 0.000); a moderately negative association between fat mass and vertical jump height (R = -0.490, p = 0.001); a very large positive association between lean body mass and peak power (R = 0.862, p = 0.000); and a large positive association between lean body mass and vertical jump height (R = 0.599, p = 0.000) and a large positive association between lean body mass and relative peak power (R = 0.530, p = 0.000); and a moderately positive association between BMI and peak power (R = 0.413, p = 0.007). Conclusion: There are significant differences in anthropometric characteristics when analyzing the anthropometric characteristics of Indian swimmers which could be attributed to the specific demands of each event. Anthropometric characteristics and body composition differences influence swim performance and vary according to gender, age and maturation status. A robust and significant positive correlation exists between lean body mass and vertical jump height suggesting that an enhancement of an individual's lean mass seems to have a positive impact on lower body power production in swimmers. Individualised training plans that focus on lower limb strength will have a potential positive effect on swim performance.