Countermovement Jump Performance Research Articles

Phase-Specific Verbal Cue Effects on Countermovement Jump Performance.

Krzyszkowski, J, Chowning, LD, and Harry, JR. Phase-Specific Verbal Cue Effects on Countermovement Jump Performance. J Strength Cond Res 36(12): 3352-3358, 2022-The aim of this study was to determine whether countermovement vertical jump (CMVJ) phase-specific cues can improve jump performance and phase-specific force-time characteristics. Twenty-nine subjects (14 males and 15 females) performed 15 total CMVJ trials (5 per condition) while being provided with a control and phase-specific (unloading phase and eccentric braking phases) foci of attention. Jump height, reactive strength index-modified, countermovement depth, time-to-takeoff, and CMVJ subphase force-time characteristics were compared between each phase-specific verbal cues and the control condition using paired samples t-tests ( α = 0.05) and Cohen's d effect sizes ( d ; large >1.2). Female ( d = 0.242; p = 0.012) and male ( d = 1.96; p = 0.047) subjects achieved greater jump heights in the control condition compared with the unloading phase condition. Females demonstrated a faster unloading phase, less unloading force, greater unloading yank, and greater braking force during the unloading condition, as well as greater eccentric braking force during the eccentric braking condition compared with the control condition ( p ≤ 0.014; d ≥ 0.242). Males exhibited less body mass unloading, greater unloading yank, faster eccentric braking time, greater eccentric braking force, and greater eccentric braking yank for both the unloading and eccentric braking conditions compared with the control condition ( p ≤ 0.047; d ≥ 0.196). Collectively, these results suggest that phase-specific foci of attention do not acutely improve jump performance but can enhance phase-specific force-time characteristics in recreationally active individuals. Specifically, practitioners should consider using an eccentric braking phase instruction for individuals need to improve eccentric braking force generation.

The influence of age on the recovery from worksite resistance exercise in career firefighters.

To examine the changes in indirect markers of muscle damage in young and older firefighters following a feasible worksite resistance exercise routine. Nineteen young (25.5±3.4years) and 19 older male career firefighters (50.3±3.5years) completed pre-testing, an acute bout of resistance exercise, and post-testing at 24, 48, and 72h post-exercise at their fire station. Prior to all testing, firefighters completed a work-related fatigue (WRF) questionnaire to account for potential unanticipated differences in previous shift workloads. Testing included perceived muscle soreness, ultrasonography to quantify muscle size and echo intensity (EI) of the vastus lateralis (VL) and biceps brachii (BB), countermovement jump (CMJ) height and velocity, upper body (UB) peak force (PF), lower body (LB) PF and rapid force, and electromyographic (EMG) amplitude of the VL. The resistance training session included 3 sets of 8-10 repetitions of a deadlift, shoulder press, lunge, and upright row exercise at 80% 1-RM. All recovery variables were analyzed using a linear mixed model, controlling for WRF. There was no interaction (age × time) for any of the variables and a similar training volume were completed between groups (P≥0.171). Muscle soreness, CMJ height and velocity, UB PF, LB rapid force and EMG amplitude at later time intervals (100-200ms), and VL and BB muscle size were altered from baseline (P≤0.044) for 48, 24, 48, 72, and 72h post-exercise, respectively. Young firefighters exhibited greater CMJ height and velocity, LB PF, LB rapid force (200ms), and lower VL EI values than the older firefighters (P≤0.047). Age did not influence the recovery from an acute bout of worksite resistance exercise in firefighters. However, UB muscle strength, CMJ performance, and LB rapid force production were reduced 24-72h post-exercise. Appropriately scheduled and chronic on-duty resistance training may mitigate these decrements.

Impact of Low Volume Velocity-Controlled vs. Repetition to Failure Resistance Training Session on Measures of Explosive Performance in a Team of Adolescents Basketball Players.

This study examined the short-term effects (post 6 h and 24 h) of two equated (70% of 1 repetition maximum (1-RM)) low volume resistance exercise protocols: (i) velocity-controlled (VC) and (ii) repetition to failure (RTF) on upper and lower body performance in competitive adolescent male basketball players. Following a randomized, counterbalanced design, ten participants (age: 16 ± 0.5 years) completed either VC or RTF separated by 72 h. VC consisted of 4 sets of 5 explosive repetitions (≥90% of the maximum velocity). RTF involved 2 sets of 10-RM (with no velocity control). Measurements of 20-m sprint, countermovement jump (CMJ) and medicine ball toss (MBT) were collected before (baseline), post 6 h and 24 h after either VC or RTF. Increases of CMJ post 6 h (VC, +6.7%; RTF, +2.4%) and MBT post 24 h (VC, +4.6%; RTF, +4.2%) were observed after both VC and RTF. Only VC potentiated CMJ after 24 h (+2.0 ± 2.3%). No other changes or differences between protocols were observed. Performing a low volume exercise protocol, either VC or RTF, induced similar potentiation effects on the vertical jump (post 6 h) and medicine ball toss (post 24 h) in adolescent basketball players. Only the VC protocol was still effective to potentiate CMJ performance after 24 h.

Position-dependent morning-to-evening variability in physical performances in elite male handball players

ABSTRACT TThis study aims to assess: (i) the morning -to- evening variability in body temperature, ball throwing velocity (BTV), shooting address, explosive lower-body power, strength power, and the repeated sprint ability (RSA) among male handball players; and (ii) the diurnal variations according to players’ positions. Twenty-two participants assigned in players of thefront line (FL; N=11) and rear line (RL; N=11) completed assessments at 8:00 a.m. and 6:00 p.m., on two occasions dispersed throughout one week. Diurnal variations in BTV (p < 0.001), 1-RM Back Half Squat test (p < 0.001), and the counter movement jump (CMJ) test (p < 0.01) were recorded in the whole population. Specifically, morning -to- evening variabilities in BTV were noted in the FL (p < 0.05) and RL players (p < 0.001), with greater values observed in RL (p < 0.001). Significant variations were also observed in the 1-RM back half squat at RL (p < 0.01), and in CMJ (p < 0,01) and RSA (p < 0.05) at FL players. In conclusion, diurnal variations were higher in the evening compared to morning hours in players of RL in BTV and the explosive lower-body power, and in players of FL in CMJ and RSA performances.

Weekly Variations of Short-Duration Maximal Jumping Performance in Soccer Players: Exploring Relationships With Accumulated Training Load and Match Demands.

Purpose: The aim of this study was 2-fold: (1) to analyze variations of short-duration maximal jumping performance in players exposed to a match and those who were not and (2) to analyze the relationships between changes in the short-duration maximal jumping performance and different accumulated training load and match demands measures.Methods: Twenty-four professional soccer players (age: 20.3 ± 1.7 years) were monitored daily for their training load and match demands over 6 weeks. In addition, they performed a weekly short-duration maximal jumping performance test (72 h after the last match).Results: Negative moderate correlations were found between percentage of change of countermovement jump (CMJ) height and Acummulated training load (ATL) of total distance (TD), high metabolic load (HML), accelerations (ACC), and decelerations (DEC) (r = −0.38, p = 0.004; r = −0.33, p = 0.013; r = −0.39, p = 0.003; and r = −0.30, p = 0.026). No correlations were found for match load (ML). TD, HML, ACC, and DCC (r = 0.27, r = 0.25, r = 0.31, and r = 0.22, respectively) were used to predict the percentage of change of CMJ height.Conclusion: Match participation has negative effects on CMJ performance. The ATL of HML, ACC, DCC, and TD have a significant influence on both CMJ measures changes. Also, the ATL values of those metrics are the best predictors of the percentage changes of CMJ performance.

Effects of Mental Fatigue Induced by Social Media Use on Volleyball Decision-Making, Endurance, and Countermovement Jump Performance.

We studied the effects of repeated inducements of mental fatigue (MF) from using social media on smartphones immediately before training sessions by young male volleyball athletes, focusing specifically on their decision-making, endurance, and countermovement jump performance (CMJ). We pair-matched 24 participants according to their decision-making abilities and then, randomly assigned them to one of two 4-week block training groups: control (CON) and smartphone use (SMA). For a 30-minute period before each training session, the CON group watched TV and the SMA group used social media apps on smartphones. We found a significant group x time interaction effect for decision making (attack, p = 0.03; passing, p = 0.02) during training blocks. More specifically, only the CON group improved their decision making (attack, p = 0.03; passing, p = 0.02). Both groups significantly improved their CMJ performance (p = .01), with no significant group x time interaction effect for CMJ (p = 0.91). Neither group significantly improved their endurance (p = 0.56). We concluded that 30-minutes of repetitive social media app use on a smartphone immediately before 4-weeks of volleyball training sessions negatively affected decision-making in young male volleyball athletes.

Does Footwear Influence Countermovement Jump Parameters Used To Monitor Performance In Collegiate Basketball Players?

The countermovement jump (CMJ) is frequently used in team sports to monitor short- and long-term changes in neuromuscular performance. Practical relevance in longitudinal changes may be subtle, requiring detailed and consistent testing protocols to limit error and allow for detection of meaningful change. Collegiate basketball players often wear different types of shoes depending upon the training activity, potentially influencing CMJ performance outcomes. PURPOSE: To evaluate the influence of footwear on key CMJ performance variables used for routine monitoring strategies in a cohort of women’s collegiate basketball players. METHODS: 11 NCAA female basketball players performed three CMJs in sport- (S), training- (T), and olympic weightlifting (WL) shoes, in a randomized order in the same testing session. One-way repeated measures analyses of variance were used to discern differences in Concentric Mean Force (ConcMF), Eccentric Mean Force (EccMF), Jump Height (JH) and Reactive Strength Index Modified (RSIMod) during the CMJ among shoe conditions, with significant set at p ≤ 0.05. Effects sizes (Cohen’s d) were calculated for pairwise comparisons and interpreted as trivial (0-0.19), small (0.20-0.49), medium (0.50-0.79) and large (≥0.80). RESULTS: Significant differences were detected among shoe-types for ConcMF (T = 1650.1 ± 182.4; S = 1645.1 ± 188.2; WL = 1616.6 ± 164, p = 0.008), EccMF (T = 808.6 ± 84.2; S = 810.1 ± 85.5; WL = 812.5 ± 83.9, p < 0.001), JH (T = 28.2 ± 3.3; S = 28.2 ± 3.4; WL = 27.3 ± 2.7, p = 0.004) and RSIMod (T = 0.45 ± 0.06; S = 0.44 ± 0.06; WL = 0.42 ± 0.05, p = 0.001). Post-hoc pairwise comparisons revealed T exhibited significantly greater ConcMF (p = 0.018, d = 0.19), EccMF (p = 0.002, d = 0.05), JH (p = 0.040, d = 0.32) and RSIMod (p = 0.004, d = 0.49) compared to WL. Similarly, S demonstrated significantly greater EccMF (p = 0.014, d = 0.03), JH (p = 0.035, d = 0.33) and RSIMod (p = 0.032, d = 0.40) compared to WL. No significant differences and only trivial effects appeared between S and T (p > 0.05, d < 0.1). CONCLUSION: These findings suggest footwear significantly influences CMJ performance. Practically, controlling for footwear between S and T shoes may not be necessary when using the CMJ for routine athlete monitoring. However, WL shoes appear to significantly influence the CMJ, resulting in decreases in performance.

Neuromuscular Performance Following Back-to-Back Simulated Games In Women’s Collegiate Basketball Players

PURPOSE: To examine the effects of back-to-back simulated games on neuromuscular performance in collegiate women’s basketball players. METHODS: Eight NCAA women’s basketball players engaged in two consecutive simulated games separated by 24 hours. Participants performed the countermovement jump (CMJ) before (Pre-Game 1 = PreG1; Pre-Game 2 = PreG2) and after (Post-Game 1 = PostG1; Post-Game 2 = PostG2) each simulated game and 48 hours (Post-Game 2 = 48Post) after PostG2. Internal (iTL) and external training load(s) (eTL) were captured during each game. A paired t-test was used to examine game differences in iTL and eTL. One-way repeated measures analyses of variance were used to detect differences in Concentric Mean Force (ConcMF), Jump Height (JH), Contraction Time (CT), and Reactive Strength Index-Modified (RSIMod), with significance set at p ≤ 0.05. Cohen’s d effect sizes were calculated for pairwise comparisons and interpreted as trivial (0-0.19), small (0.20-0.49), medium (0.50-0.79), and large (≥0.80). RESULTS: No significant differences were detected in eTL volume (PlayerLoad (PL), p = 0.074) or intensity (PL/min = 0.379), but significantly greater iTL was observed in G1 compared to G2 with greater Training Impulse (p = 0.002) and average heart rate (p = 0.001). Significant differences appeared across time in ConcMF (p = 0.007), JH (p = 0.001), and RSIMod (p = 0.050), but not CT (p = 0.356). Pairwise comparisons revealed significant decreases in JH from PreG1(28.3 ± 4.2) to PostG2 (25.8 ± 3.03 cm, p = 0.036, d = 0.69). While not significant (p > 0.05) a large effect for decreases in JH was observed from PreG1 to 48Post (p = 0.082, d = 0.8). ConcMF significantly decreased from PostG1 (1730.1 ± 177.3 N) to 48Post (1636.9 ± 131.6 N, p = 0.05, d = 0.41). RSIMod displayed significant reductions at 48Post (0.435 ± 0.12) compared to both PreG1 (0.50 ± 0.12, p = 0.001, d = 0.58) and PostG2 (0.46 ± 0.10, p = 0.015, d = 0.43). While not significant RSIMod displayed a moderate decrease from PreG1 to PostG1 (d = 0.43). CONCLUSIONS: These data suggest back-to-back gameplay suppresses CMJ performance with large deficits in JH and explosiveness (RSIMod) manifesting 48 hours after the completion of play. Interestingly, it appears deficits in explosiveness may result from a change in gross output (JH) rather than alterations in movement strategy (CT).

The Influence of Injury History on Countermovement Jump Performance and Movement Strategy in Professional Soccer Players: Implications for Profiling and Rehabilitation Foci.

Professional soccer players who have sustained a lower limb injury are up to 3× more likely to suffer a reinjury, often of increased severity. Previous injury has been shown to induce compensatory strategies during neuromuscular screening tests, which might mask deficits and lead to misinterpretation of readiness to play based on task outcome measures. To investigate the influence of previous injury in professional soccer players on countermovement jump (CMJ) performance and movement strategy. Cross-sectional. Professional soccer club competing in the English Championship (tier 2). Patients (or Other Participants): Outfield players with a minimum of 6 years as a professional. Players were categorized as previously injured (n = 10) or not injured (n = 10). All players completed double- and single-leg CMJ trials. CMJ performance was quantified as jump height and flight time:contraction time ratio. CMJ movement strategy was quantified as force-time history, differentiating eccentric and concentric phases and CMJ depth. Double-leg CMJ was not sensitive to previous injury in performance or movement strategy. In contrast, single-leg CMJ performance was impaired in players with previous injury, who generated significantly lower eccentric and concentric peak force and rate of force development, and a deeper countermovement. Impaired single-leg CMJ performance was also evident in the nonaffected limb of previously injured players, suggesting cross-contamination. Hierarchical ordering revealed that the eccentric phase of the CMJ contributed little to performance in previously injured players. In noninjured players, the eccentric rate of force development and concentric peak force were able to account for up to 89% of the variation in CMJ performance. Single-leg CMJ is advocated for player profiling, being more sensitive to previous injury, and negating the opportunity for interlimb compensation strategies. Movement strategy deficits in previously injured players suggest rehabilitation foci specific to eccentric force development.

The mobility limitation in healthy older people is due to weakness and not slower muscle contractile properties.

The maximal power generating capacity of a muscle declines with age and has a negative impact on the performance of daily life activities. As muscle power is the product of force and velocity, we recruited 20 young (10 men, 10 women: 20–31 years) and 20 older (10 men, 10 women: 65–86 years) people to investigate which of these components contributes to the lower power and performance in old age. After determination of the maximal isometric knee extension torque (MVC), they performed a countermovement jump (CMJ) in 1) the normal situation (normal), 2) with an extra load of 15% body weight (loaded) and 3) 15% lower body weight (unloaded with a pulley system), and a timed up-and-go test (TUG) in the normal or loaded condition. The TUG and CMJ performance was lower in old than young participants (p<0.001). Below a critical CMJ peak power of ~23.7 W·kg-1 TUG showed a progressive decrease. The CMJ take-off velocity (Voff) in the normal condition was lower in old than young participants (p<0.001). However, the Voff vs. body weight/MVC relationship of the normal, loaded and unloaded data combined was similar in the old and young participants and fitted the Hill equation (R2 = 0.396). This indicates that 1) only when peak power drops below a critical threshold TUG becomes impaired and 2) there was no evidence for intrinsic slowing of the muscle contractile properties in older people, but rather the older people were working on a slower part of the force-velocity relationship due to weaker muscles.

Playing videogames or using social media applications on smartphones causes mental fatigue and impairs decision-making performance in amateur boxers

This study aimed to analyze the effect of playing videogames and using social media applications on smartphones on decision-making and countermovement jump (CMJ) performance in amateur boxers. Twenty one boxers were enrolled in the study and were randomly assigned to all three experimental conditions [smartphone (30SMA), videogame (30VID), and control (CON)]. CMJ was measured before and 30-min after each experimental condition. The athletes ran simulated combat recorded for decision-making analysis. The boxers watched coaching videos (CON), used social media applications on smartphones (30SMA), and played video games (30VID) for 30 min just before the combat simulation. Both attack and defense decision-making performance were worse in both 30SMA and 30VID conditions compared to the CON condition (p = 0.001). Regarding CMJ, despite no condition effect (p = 0.96) been obtained, a time effect (p = 0.001) was observed; So, it was found a decrease in CMJ performance after all experimental conditions (p = 0.001), with no difference between them. Using social media applications on smartphones and playing video game impairs decision-making performance in amateur boxers, with no harms for CMJ performance.

The Association Between Alterations in Redox Homeostasis, Cortisol, and Commonly Used Objective and Subjective Markers of Fatigue in American Collegiate Football.

To assess associations between a free oxygen radical test (FORT), free oxygen radical defense test (FORD), oxidative stress index, urinary cortisol, countermovement jump (CMJ), and subjective wellness in American college football. Twenty-three male student athlete American college football players were assessed over 10 weeks: off-season conditioning (3wk), preseason camp (4wk), and in season (3wk). Assessments included a once-weekly FORT and FORD blood sample, urinary cortisol sample, CMJ assessment including flight time, reactive strength index modified and concentric impulse, and a daily subjective wellness questionnaire. Linear mixed models analyzed the effect of a 2 within-subject SD change in the predictor variable on the dependent variable. The effects were interpreted using magnitude-based inference and are presented as standardized effect size (ES) ± 90% confidence intervals. Small negative associations were observed between FORT-flight time, FORT-fatigue, FORT-soreness (ES range = -0.30 to -0.48), FORD-sleep (ES = 0.42 ± 0.29), and oxidative stress index soreness (ES = 0.56 ± 0.29). Small positive associations were observed between FORT-cortisol (ES = 0.36 ± 0.35), FORD-flight time, FORD reactive strength index modified and FORD-soreness (0.37-0.41), oxidative stress index concentric impulse (ES = 0.37 ± 0.28), and with soreness-concentric impulse, soreness-flight time, and soreness reactive strength index modified (0.33-0.59). Moderate positive associations were observed between cortisol-concentric impulse and cortisol-sleep (0.57-0.60). FORT/FORD was associated with CMJ variables and subjective wellness. Greater amounts of subjective soreness were associated with decreased CMJ performance, increased FORT and cortisol, and decreased FORD.

Dimensionality Reduction Differentiates Sensitive Force-Time Characteristics from Loaded and Unloaded Conditions throughout Competitive Military Training

The purpose was to evaluate neuromuscular fatigue’s effect on unloaded and loaded countermovement jump (CMJ) force-time characteristics during high-intensity tactical training. Eighteen male and sixteen female Marines completed two maximal effort CMJs, in unloaded (PVC pipe) and loaded (10 kg weight vest and 20 kg barbell) conditions, prior to, and 24, 48, and 72 h after starting the 4-day event. The top three variables from three principal components (PC) were analyzed using mixed-effects modeling (PC1—concentric mean power, eccentric peak force, and modified reactive strength index; PC2—countermovement depth, eccentric mean power, and eccentric mean velocity; PC3—braking duration, jump height, peak power). Metrics from PC1 and PC3 were reduced across training and from both loading conditions. Metrics from PC2 were similarly affected by external loading but were less influenced by training-induced fatigue. Jump performances with the barbell and with shallower countermovement depths did not change throughout training. Thus, 20 kg loaded CMJs are stable neuromuscular measures suitable for tracking chronic training adaptations. Monitoring unloaded and 10 kg loaded CMJ performances, along with movement strategies (i.e., countermovement rates and depth), may help identify moments of accumulated fatigue to inform training and recovery adjustments and improve the sustainability of personnel.

Does Footwear Influence Countermovement Jump Parameters Used to Assess Performance in Collegiate Basketball Players?

Background: The countermovement jump (CMJ) is used to monitor short- and long-term changes in neuromuscular performance, where practically relevant alteration may be subtle, requiring detailed and consistent testing protocols to limit error and allow detection of meaningful change. Collegiate basketball players often wear different types of footwear depending upon the training activity, potentially influencing CMJ performance outcomes. Objective: This study evaluated the influence of footwear on key CMJ variables used for routine performance assessments in a cohort of 11 NCAA women’s collegiate basketball players. Method: In a cross-over repeated measures study design, players performed three CMJs in Basketball-, Training-(Trainers), and Olympic Weightlifting (WL) shoes, in a randomized order during one testing session. One-way repeated measures analyses of variance (p ≤ .05) and effect sizes (Cohen’s d) were used to discern differences in CMJ variables among shoe conditions. Results: WL demonstrated greater Eccentric Mean Force (p ≤ .014, d ≥ 0.03) and lower Flight Time:Contraction Time (p ≤ .029, d ≥ 0.31), Jump Height (p ≤ .040, d ≥ 0.32), and Reactive Strength Index-Modified (p ≤ .032, d ≥ 0.40) than both Basketball and Trainers. Additionally, WL exhibited lower Concentric Mean Force (p = .018, d = 0.19), Concentric Mean Power (p = .008, d = 0.29), Eccentric Peak Force (p = .050, d = 0.19), and Flight Time (p = .036, d = 0.31) compared to Trainer. No significant differences and only trivial effects appeared between Basketball and Trainers (p &gt; 0.05, d &lt; 0.1). Conclusion: These findings suggest footwear significantly influences CMJ performance. WL shoes appear to negatively impact CMJ performance; however, Basketball and Trainers appear to exert negligible effects that should allow clinicians and practitioners to feel confident about measurement and data quality when performing short- and long-term CMJ measurements in either Basketball or Trainers.

Examination of the Sprinting and Jumping Force-Velocity Profiles in Young Soccer Players at Different Maturational Stages.

The aim was to determine the relationships among components of the force-velocity (F-V) profiles in jumping and sprinting, with both biological and chronological ages in 89 young soccer players belonging to categories from U10 to U18. Participants performed countermovement jumps (CMJ) and 20-m sprint tests. F-V components assessed were associated with both maturity offset and chronological age, using correlation and multiple linear regression analyses. Horizontal (i.e., maximal theoretical force [F0] and velocity [V0], maximal power [Pmax] and F-V slope) and vertical (i.e., [F0] and [Pmax]) F-V components displayed very large correlations (i.e., 0.79 ≤ r ≤ 0.92) with both chronological age and maturity offset. The combination of sprinting Pmax and training experience and jumping F0 and training experience explained up to 94% of the variances in maturity offset and chronological age. Furthermore, similar correlations were found between sprinting and jumping performances, and components of the F-V profiles, and both maturity offset and chronological age. Identification of vertical jump and sprint mechanical determinants may assist in strengthening those components of the F-V profile which are weaker throughout the training process. Sprinting and jumping capabilities can be indistinctly monitored with respect to their chronological age or maturity offset in young soccer players.

Effects of Adding Small Combat Games to Regular Taekwondo Training on Physiological and Performance Outcomes in Male Young Athletes.

This study investigated the effect of area sizes (4 × 4, 6 × 6, and 8 × 8 m) and effort-pause ratios (free combat vs. 1:2) variation on the physiological and perceptive responses during taekwondo combats (Study 1). In a second study, the effects on physical performance of 8 weeks of small combat-based training added to regular taekwondo training were investigated (Study 2). In random order, 32 male taekwondo athletes performed six (i.e., two effort-to-pause ratios × three area sizes conditions) different 2-min taekwondo combats (Study 1). Thereafter (Study 2), they were randomly assigned to three experimental groups (4 × 4, 6 × 6, and 8 × 8 m) and an active control group (CG). Regarding Study 1, blood lactate concentration [La] before and after each combat, mean heart rate (HRmean) during each combat, and rating of perceived exertion (CR-10) immediately after each combat were assessed. Regarding Study 2, progressive specific taekwondo (PSTT) to estimate maximum oxygen consumption (VO2max), taekwondo-specific agility, and countermovement jump (CMJ) tests were administered before and after 8 weeks of training. Study 1 results showed that 4 × 4 m elicited lower HRmean values compared with 6 × 6 m (d = −0.42 [small], p = 0.030) and free combat induced higher values compared with the 1:2 ratio (d = 1.71 [large], p < 0.001). For [La]post, 4 × 4 m area size induced higher values than 6 × 6 m (d = 0.99 [moderate], p < 0.001) and 8 × 8 m (d = 0.89 [moderate], p < 0.001) and free combat induced higher values than 1:2 ratio (d = 0.69 [moderate], p < 0.001). Higher CR-10 scores were registered after free combat compared with 1:2 ratio (d = 0.44 [small], p = 0.007). For Study 2, VO2max increased after training [F (1, 56) =30.532, p < 0.001; post-hoc: d = 1.27 [large], p < 0.001] with higher values for 4 × 4 m compared with CG (d = 1.15 [moderate], p = 0.009). Agility performance improved after training [F (1, 56) = 4.419, p = 0.04; post-hoc: d = −0.46 [small], p = 0.04] and 4 × 4 m induced lower values in comparison with 6 × 6 m (d = −1.56 [large], p = 0.001) and CG (d = −0.77 [moderate], p = 0.049). No training type influenced CMJ performance. Smaller area size elicited contrasting results in terms of metabolic demand compared with larger sizes (i.e., lower HRmean but higher [La] and CR-10), whereas free combat induced variables' consistently higher values compared with imposed 1:2 ratio (Study 1). Taekwondo training is effective to improve VO2max and agility (Study 2), but small combat training modality should be investigated further.

Analyses of Countermovement Jump Performance in Time and Frequency Domains.

This study aimed to analyze counter-movement jump (CMJ) performance in time and frequency domains. Fortyfour Division I American football players participated in the study. Kinetic variables were collected from both dominant and non-dominant legs using two force plates. Normalized peak power, normalized net impulse, and normalized peak force significantly correlated with jump height (r = .960, r = .998, r = .725, respectively with p < .05). The mean frequency component was significantly correlated with CMJ performance (r = .355 with p < .05). The reliability of the frequency variables was higher than the time domain variables. Frequency domain variables showed weaker correlations with jump height compared with time domain variables. Frequency domain analysis provides frequency components, which represent the rate of energy transmission from the eccentric phase to the end of the push-off phase. Frequency component information may provide additional information for the analyses of CMJ performance for athletes.

Performing Repetitions to Failure in Lower-Limb Single-Joint Exercise Does Not Reduce Countermovement Jump Performance in Trained Male Adults.

Performing repetitions to failure (RF) is a strategy that might acutely reduce neuromuscular performance, as well as increase the rating of perceived exertion (RPE) and the internal training load (ITL) during and after a resistance training (RT) session. Thus, this study aimed to analyze the acute effects of RF or repetitions not to failure (RNF) on countermovement jump (CMJ) performance and the ITL in trained male adults. Eleven men performed two experimental protocols in randomized order (RF vs. RNF). Under the RF condition, participants performed three sets of the leg extension exercise using 100% of the 10RM load and rest intervals of 180-s between sets. Under the RNF condition, participants were submitted to six sets of five repetitions with the same intensity and an 80-s rest interval between sets in the same exercise. The CMJ test was analyzed before and following (15-s and 30-min, respectively) each experimental session. The ITL was evaluated by multiplying the RPE and the total session time, 30-min after the protocol. No main effect or interaction time vs. condition was found for CMJ performance (p > 0.05). In contrast, the ITL showed higher values under the RF condition (p = 0.003). Therefore, even though RF-induced a greater ITL, our results suggest that adopting this strategy in one single-joint exercise for the lower limbs does not seem sufficient to reduce CMJ height.

Accentuated Eccentric Loading is Superior to Traditional Loading for Improving Acute Countermovement Jump Performance in Adult, Resistance-Trained Males.

Clinical Scenario: Traditional loading (TL) is a common technique to employ when engaging in countermovement jumps (CMJ). Accentuated eccentric loading (AEL) is a newer modality that is being explored for acute CMJ performance. Focused Clinical Question: In adult, resistance-trained males, will AEL have a superior impact on acute CMJ performance compared to TL? Summary of Key Findings: The literature was searched for studies that examined the influence of AEL on acute CMJ performance compared to a TL protocol. TL was defined as any loading condition that utilized an equivalent resistance during both the eccentric and concentric contractions. Three studies met the inclusion and exclusion criteria, and were identified and included in the critically appraised topic. Each of the 3 studies found that various AEL conditions were either equal to or better than TL when examining subsequent CMJ performance. In no specific CMJ outcome measure was TL deemed to have a greater impact than AEL. Clinical Bottom Line: AEL provides more favorable acute CMJ performance than TL in adult, resistance-trained males. Strength of Recommendation: Consistent findings from 2 randomized crossover studies and one repeated-measured design investigation suggest level 2b evidence to support AEL as an ideal protocol for acute CMJ performance.

Impulse-Based Dynamic Strength Index: Considering Time-Dependent Force Expression.

Haischer, MH, Krzyszkowski, J, Roche, S, and Kipp, K. Impulse-based dynamic strength index: considering time-dependent force expression. J Strength Cond Res 35(5): 1177-1181, 2021-The dynamic strength index (DSI) is a useful tool to assess an athlete's capacity to effectively use maximum strength during dynamic tasks. Although DSI is traditionally calculated based on peak forces, the ability to express force over time (i.e., impulse) is a better predictor of dynamic performance. The purpose of this study was to investigate the association between DSI calculated based on peak force (fDSI) and impulse (iDSI). Nineteen female collegiate lacrosse players performed countermovement jumps (CMJs) and isometric midthigh pulls (IMTPs). Peak force and impulse were extracted from CMJ and IMTP force-time data. Countermovement jump impulse was calculated by integrating force over the concentric movement time, whereas IMTP impulse was calculated by integrating force over the CMJ-matched movement time. Ratios between CMJ and IMTP peak force and impulse were used to calculate fDSI and iDSI, respectively. A moderate positive correlation existed between iDSI and fDSI (ρ = 0.644 [0.283-0.840], p = 0.003). Based on thresholds established in the literature, the 2 indices suggest conflicting training recommendations for 37% of athletes. Because impulse is a better predictor of dynamic performance, iDSI may represent a more valid method for assessing an athlete's capacity to effectively use maximum strength during dynamic tasks. Practitioners and researchers may want to consider augmenting current training and research practices with an impulse-based DSI.