Are Young Female Basketball Players Adequately Prepared for a Force-Velocity Jumping and Sprinting Assessment?

PURPOSE: The aim of this study was to explore the interday reliability of mechanical variables obtained from the horizontal and vertical force-velocity (FV) profiles in adolescent female basketball players. If found to be reliable, the associations between FV parameters (theoretical maximal force, velocity, and power), squat jump (SJ) height, 30-m sprint, and change of direction (COD) times were evaluated. METHODS: After familiarization, SJ against incremental loads, 30-m sprint, and 505-COD tests were obtained twice in 36 adolescent female basketball players (age = 15.4 [1.2] y). RESULTS: Reliability for vertical FV parameters was unacceptable, whereas 505-COD times and FV horizontal parameters (except for theoretical maximal power) showed a moderate to high reliability. 505-COD time was correlated with FV horizontal parameters (range: r = -.821, -.451), and a large association was observed with both SJ height (r = -.678, -.600) and 30-m sprint time (r = .813, .858). CONCLUSIONS: Due to low levels of strength, our athletes were not adequately prepared to obtain a reliable vertical FV profile. Practitioners can expect acceptable reliability of the horizontal FV profile. Given the association between COD performance and SJ height and 30-m sprint time, we encouraged practitioners with limited equipment at their disposal to use COD and/or 30-m sprint tests.

Effects of a six-week multimodal training programme on the sprinting ability of adolescent rugby sevens players.

This study evaluated the effects of 6-week multimodal training on the sprinting performance and biomechanics of adolescent rugby players. Twenty-four players were assigned to control group (CG) or intervention group (IG). For 6 weeks, CG maintained their training routine, while IG completed a training programme consisting of unresisted sprints, as well as heavy-resisted sprints, running technique drills and lumbopelvic stability. Before and after, sprint performance, horizontal force-velocity profile (FV-h), sprinting kinematics and spatiotemporal data were obtained. After the training, IG reduced the 0-5 m (p = 0.044), 0-10 m (p = 0.046) and 25-30 m (p = 0.035) split times compared with CG. In FV-h, IG displayed a higher maximal theoretical horizontal force (p = 0.035) and ratio of force (p = 0.048) than CG. Regarding kinematic and spatiotemporal variables, only IG improved step length (p < 0.001), step rate (p = 0.005) and distance between knees (p = 0.048) compared with baseline, but there were no between-group differences. Six weeks of multimodal training improved sprinting acceleration and mechanical variables of force application during sprinting of adolescent rugby players. Although IG improved some biomechanical variables compared with baseline, these changes were similar to those observed in CG.

Comparison of kinematics and kinetics between unassisted and assisted maximum speed sprinting.

Producing comparable/greater ground reaction forces (GRFs) at faster running speeds is beneficial for sprint performance, and assisted sprint training is used to induce faster running speed conditions. This study aimed to demonstrate the characteristics of assisted sprinting at the maximal speed phase and investigate acute differences to control sprinting. Fifteen sprinters completed control and assisted (5 kg) sprints over force platforms. Assisted sprinting increased running speed (9.3% mean difference), while propulsive mean force (-4.3%) and impulse (-12.4%) decreased, suggesting that running speed improvements were caused primarily by assisted pulling force rather than improvements in anteroposterior force production of athletes. In addition, vertical mean force increased (4.2%), probably due to braking mean force (34.2%) and impulse (32.5%) increases. Magnitude of control trial maximum speed was achieved earlier (during acceleration) in assisted trials, and net anteroposterior (includes both braking and propulsive components) mean force (67.2%) and impulse (67.9%) increased at this matched speed, suggesting that assisted sprints could be used to practice producing greater GRFs at comparable speeds. Running speed improvement by pulling force was associated with contact time decreases (r = -.565), suggesting that shortening contact time may be important for effective assisted sprinting.

Microdosing Sprint Distribution as an Alternative to Achieve Better Sprint Performance in Field Hockey Players.

Introduction: The implementation of optimal sprint training volume is a relevant component of team sport performance. This study aimed to compare the efficiency and effectiveness of two different configurations of within-season training load distribution on sprint performance over 6 weeks. Methods: Twenty male professional FH players participated in the study. Players were conveniently assigned to two groups: the experimental group (MG; n = 11; applying the microdosing training methodology) and the control group (TG; n = 9; traditional training, with players being selected by the national team). Sprint performance was evaluated through 20 m sprint time (T20) m and horizontal force−velocity profile (HFVP) tests before (Pre) and after (Post) intervention. Both measurements were separated by a period of 6 weeks. The specific sprint training program was performed for each group (for vs. two weekly sessions for MG and TG, respectively) attempting to influence the full spectrum of the F-V relationship. Results: Conditional demands analysis (matches and training sessions) showed no significant differences between the groups during the intervention period (p > 0.05). No significant between-group differences were found at Pre or Post for any sprint-related performance (p > 0.05). Nevertheless, intra-group analysis revealed significant differences in F0, Pmax, RFmean at 10 m and every achieved time for distances ranging from 5 to 25 m for MG (p < 0.05). Such changes in mechanical capabilities and sprint performance were characterized by an increase in stride length and a decrease in stride frequency during the maximal velocity phase (p < 0.05). Conclusion: Implementing strategies such as microdosed training load distribution appears to be an effective and efficient alternative for sprint training in team sports such as hockey.

Longitudinal Effects of Traditional and Rest Redistribution Set Configurations on Explosive-Strength and Strength-Endurance Manifestations.

ABSTRACT: Janicijevic, D, González-Hernández, JM, Jiménez-Reyes, P, Márquez, G, and García-Ramos, A. Longitudinal effects of traditional and rest redistribution set configurations on explosive-strength and strength-endurance manifestations. J Strength Cond Res 37(5): 980-986, 2023-This study aimed to compare the long-term effects of resistance training programs based on traditional and rest redistribution set configurations on explosive-strength and strength-endurance performance of lower-body and upper-body muscles. Thirty physically active men were randomly assigned to a traditional group (TRG: 6 sets of 5 repetitions with 3 minutes of interset rest) or a rest redistribution group (RRG: 30 sets of 1 repetition with 31 seconds of interrepetition rest). The training program lasted 6 weeks (2 sessions·wk -1 ), and in each training session, the squat and bench press exercises were performed with maximal concentric effort against approximately the 75% of the 1 repetition maximum. Before and after training, explosive-strength performance (peak velocity reached at submaximal loads during the countermovement jump and bench press throw) and strength-endurance performance (mean set velocity of 10 repetitions using both traditional and cluster sets in the squat and bench press) were assessed. Significant improvements in all dependent variables were observed after training for both the TRG ( p ≤ 0.004; effect size [ES] = 0.63-3.06) and RRG ( p ≤ 0.001; ES = 0.58-3.23). The magnitude of the changes was comparable for both groups with the only exception of the larger improvements observed in the RRG for the bench press mean set velocity using both traditional (ES = 0.77) and cluster (ES = 0.82) set configurations. Traditional and rest redistribution set configurations are equally effective to improve lower-body explosive strength, lower-body strength endurance, and upper-body explosive strength, whereas rest redistribution set configurations could induce greater adaptations in upper-body strength endurance.

A New Index to Evaluate Running Coordination Based on Notational Analysis.

The aim of this study was 1) to define a new index to describe running coordination, named % of coordination, and 2) to examine whether it could represent an order parameter in relation to running velocity. Twelve international middle-distance athletes (six males and six females) performed three trials at easy, 5000 m pace and sprint velocities while filmed from a lateral view at 240 Hz. Notational analysis of six lower-limb key events corresponding to touchdown, mid-stance and flight phases was performed with high values of intra- (maximum standard deviation = 7 ms) and inter-operator (maximum systematic bias = 6 ms) reliability. Running velocity manipulations resulted in substantial and progressive increases in stride length, stride frequency (all p's < 0.001) and % of coordination (p < 0.001; η²p = 0.77), while duty factor showed a progressive reduction (p < 0.001, R2c = 0.86). However, % of coordination depended on the stride phase (p < 0.001; η²p = 0.78), with greater time gaps between key events in touchdown and mid-stance than in the flight phase. Results confirmed that % of coordination can illustrate changes in movement organisation, representing an easy tool for evaluating the running technique of competitive athletes.

Optimal mechanical force-velocity profile for sprint acceleration performance.

The aim was to determine the respective influences of sprinting maximal power output ( P H max ) and mechanical Force-velocity (F-v) profile (ie, ratio between horizontal force production capacities at low and high velocities) on sprint acceleration performance. A macroscopic biomechanical model using an inverse dynamics approach applied to the athlete's center of mass during running acceleration was developed to express the time to cover a given distance as a mathematical function of P H max and F-v profile. Simulations showed that sprint acceleration performance depends mainly on P H max , but also on the F-v profile, with the existence of an individual optimal F-v profile corresponding, for a given P H max , to the best balance between force production capacities at low and high velocities. This individual optimal profile depends on P H max and sprint distance: the lower the sprint distance, the more the optimal F-v profile is oriented to force capabilities and vice versa. When applying this model to the data of 231 athletes from very different sports, differences between optimal and actual F-v profile were observed and depend more on the variability in the optimal F-v profile between sprint distances than on the interindividual variability in F-v profiles. For a given sprint distance, acceleration performance (<30 m) mainly depends on P H max and slightly on the difference between optimal and actual F-v profile, the weight of each variable changing with sprint distance. Sprint acceleration performance is determined by both maximization of the horizontal power output capabilities and the optimization of the mechanical F-v profile of sprint propulsion.

Influence of Hurdling Clearance on Sprint Mechanical Properties in High-Level Athletes.

ABSTRACT: Jiménez-Reyes, P, Casado, A, González, JE, and Rodríguez-Fernández, C. Influence of hurdling clearance on sprint mechanical properties in high-level athletes. J Strength Cond Res 36(3): 827-831, 2022-Short hurdling races are sprint races in which athletes must also clear 10 hurdles. Assessing the force-velocity (F-V) profile in sprinting has been found useful for implementing individualized training programs and determining the mechanical effectiveness in force application. This study therefore compared the sprint mechanical F-V profile between flat and hurdle conditions to distinguish which mechanical capacity (i.e., maximum force [F0], maximum velocity [V0], or maximum power [Pmax]) is required to optimize performance in hurdling races. Twenty-two athletes (10 men and 12 women, aged: 22.4 ± 3.6 years old) competing at the national and elite performance levels conducted 2 maximal sprints of 40 m in both flat and hurdle conditions. F0, V0, FVslope, Pmax, and decrease and maximal ratio of horizontal force (DRF and RFpeak, respectively) were assessed for each condition. A higher F0 (effect size [ES] = 1.69) and a lower V0 (ES = 2.08), DRF (ES = 3.15) and RFpeak (ES = 1.31) were found in the hurdle condition than in the flat condition. No significant differences were observed between conditions for Pmax (ES = 0.01). These results support the potential of using the F-V profile to monitor sprint mechanics to optimize specific and individualized sprint training programs for hurdlers and sprinters. Coaches of hurdlers should thus consider implementing in their training routines exercises that were found to be effective on the development of F0, such as heavy load resisted sprints.

Individual Adaptation Kinetics Following Heavy Resisted Sprint Training.

ABSTRACT: Morin, JB, Capelo-Ramirez, F, Rodriguez-Pérez, MA, Cross, MR, and Jimenez-Reyes, P. Individual adaptation kinetics following heavy resisted sprint training. J Strength Cond Res 36(4): 1158-1161, 2022-The aim of this study was to test individual adaptation kinetics to a high-resistance sprint training program designed to improve maximal horizontal power (Pmax), and compare the group and individual results of a classical "pre-post" analysis, and a "pre-peak" approach. Thirteen male and 9 female trained sprinters had their 30-m sprint performance and mechanical outputs assessed 1 week before (PRE), and one (POST, W1), 2 (W2), 3 (W3) and 4 (W4) weeks after a 10-week training block (10 repetitions of 20-m resisted sprints at the load associated to the apex of their velocity-power relationship: i.e., 90 ± 10% body mass on average (range: 75-112%). We observed clearly different outcomes on all variables for the PRE-POST vs. PRE-PEAK analyses. The PRE-PEAK analysis showed a larger (almost double) increase in Pmax (9.98 ± 5.27% on average, p < 0.01) than the PRE-POST (5.39 ± 5.87%, p < 0.01). Individual kinetics of post-training adaptations show that peak values were not captured in the POST (W1) assessment (generally observed at W3 and W4). Finally, the week of greatest Pmax output differed strongly among subjects, with most subjects (7/22) peaking at W4. In conclusion, after a 10-week high-resistance sprint training block, a classical 1-week-PRE to 1-week-POST assessment could not capture peak adaptation, which differed among athletes. Adopting a similar approach in practice or research should improve insight into the true effects of training stimuli on athletic capabilities.

Gender-Specific Association of the Sprint Mechanical Properties With Change of Direction Performance in Basketball.

ABSTRACT: Baena-Raya, A, Jiménez-Reyes, P, Romea, ES, Soriano-Maldonado, A, and Rodríguez-Pérez, MA. Gender-specific association of the sprint mechanical properties with change of direction performance in basketball. J Strength Cond Res 36(10): 2868-2874, 2022-We evaluated the gender-specific associations between the mechanical variables derived from the horizontal force-velocity (FV) profile (i.e., theoretical maximal force [ F0 ], velocity [ V0 ], maximal power output [ Pmax ], peak ratio of the effective horizontal component [ RFpeak ], and the force application technique index [ DRF ]) and the change of direction (COD) performance for basketball players. Seventy-one players (23 women and 48 men) were assessed for the horizontal FV profile and COD using the modified 505 and V-cut tests. The FV profile parameters were significantly higher for the men than those for the women. The F0 , RFpeak , and Pmax were strongly associated with performance in the 505 test (women rrange = -0.72 to -0.82; men: rrange = -0.67 to -0.75; p < 0.001) and the V-cut test (women rrange = -0.68 to -0.76; men rrange = -0.45 to -0.50; p < 0.001), as well as with a lower COD deficit (women rrange = 0.58 to 0.75 ( p < 0.01); men rrange = 0.49 to 0.54; all p < 0.001). For the women, a 1 N·kg -1 increase of the F0 was associated with -0.20 seconds and -0.56 seconds in the 505 and V-cut tests, respectively, and 0.16 seconds for the COD deficit. In the men, it was associated with -0.13 seconds and -0.37 seconds in the 505 and V-cut tests, respectively, and 0.10 seconds for the COD deficit. F0 , RFpeak , and Pmax are the most determinant sprint mechanical properties to successfully COD and reduce the COD deficit. The horizontal FV profile assessment is recommended for diagnosing and prescribing a training program for basketball players.

Response of Muscle Damage Markers to an Accentuated Eccentric Training Protocol: Do Serum and Saliva Measurements Agree?

ABSTRACT: González-Hernández, JM, Jiménez-Reyes, P, Cerón, JJ, Tvarijonaviciute, A, Llorente-Canterano, FJ, Martínez-Aranda, LM, and García-Ramos, A. Response of muscle damage markers to an accentuated eccentric training protocol: do serum and saliva measurements agree? J Strength Cond Res 36(8): 2132-2138, 2022-This study aimed (a) to examine the acute and delayed responses of 3 muscle damage biomarkers: creatine kinase (CK), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) to an accentuated eccentric training protocol in serum, and (b) to explore the changes of these biomarkers in saliva and compare them with serum. Sixteen resistance-trained university students (10 men [age = 26.6 ± 4.8 years, full squat one repetition maximum [1RM] = 103.4 ± 14.4 kg] and 6 women [age = 22.7 ± 1.4 years, full squat estimated 1RM = 68.3 ± 10.5 kg]) completed an accentuated eccentric strength training protocol with the full squat exercise consisting of 8 sets of 10 repetitions against the 120% estimated 1RM load with 5 minutes of interset rest. The activity of muscle damage biomarkers (CK, AST, and LDH) was measured in serum and saliva before training (Pre), 24 hours after training (Post24), and 96 hours after training (Post96). In serum, lower values of the 3 muscle damage markers were observed at Pre compared to Post24 and Post96, whereas no significant differences were observed between Post24 and Post96 for any analyte. In saliva, there was a significant increase in men at Post96 compared with Pre in CK. The correlations between the measurements in serum and saliva ranged from trivial to small ( r = -0.034 to 0.212). These results suggest that the measurement of muscle damage markers in serum and saliva do not provide the same information in the conditions of our study.

Seasonal Changes in the Sprint Acceleration Force-Velocity Profile of Elite Male Soccer Players.

ABSTRACT: Jiménez-Reyes, P, Garcia-Ramos, A, Párraga-Montilla, JA, Morcillo-Losa, JA, Cuadrado-Peñafiel, V, Castaño-Zambudio, A, Samozino, P, and Morin, J-B. Seasonal changes in the sprint acceleration force-velocity profile of elite male soccer players. J Strength Cond Res 36(1): 70-74, 2022-This study aimed to describe the seasonal changes in the sprint force-velocity (Fv) profile of professional soccer players. The sprint Fv profile of 21 male soccer players competing in the first division of the Spanish soccer league was evaluated 6 times: preseason 1 (September 2015), in-season 1 (November 2015), in-season 2 (January 2016), in-season 3 (March 2016), in-season 4 (May 2016), and preseason 2 (August 2016). No specific sprint capabilities stimuli other than those induced by soccer training were applied. The following variables were calculated from the velocity-time data recorded with a radar device during an unloaded sprint: maximal force (F0), maximal velocity (v0), Fv slope, maximal power (Pmax), decrease in the ratio of horizontal-to-resultant force (DRF), and maximal ratio of horizontal-to-resultant force (RFpeak). F0 (effect size [ES] range = 0.83-0.93), Pmax (ES range = 0.97-1.05), and RFpeak (ES range = 0.56-1.13) were higher at the in-seasons 2 and 3 compared with both preseasons (p ≤ 0.006). No significant differences were observed for v0, Fv slope, and DRF (p ≥ 0.287). These results suggest that relevant Fv profile variables may be compromised (F0 more compromised than v0) toward the end of the competitive season when specific sprint stimuli are not systematically applied.

Removal of 142Pr from nuclear purity water using hydroxyapatite.

The adsorption of praseodymium using hydroxyapatite was evaluated. The hydroxyapatite (HAP) was characterized by X-ray diffraction (JCPDS 01-04-3708), scanning electron microscopy, BET specific surface area (54.2 m2/g), and point of zero charge (6.5). Adsorption kinetics and isotherms were evaluated at pH of 3 and 142Pr was determined using a gamma spectrometer. The adsorption of praseodymium was fast (1 min of contact) with an adsorption capacity of 1.68 mg/g and the data were best adjusted to the pseudo-second-order model, whereas the data of adsorption isotherm were best adjusted to the Langmuir model with a maximum adsorption capacity of 39.16 ± 0.20 mg/g. The thermodynamic parameters indicated that a physicochemical mechanism took place in the adsorption of praseodymium by HAP (adsorption enthalpy = 31.65 kJ/mol), the randomness of the system increased (adsorption entropy = 0.16 kJ/mol), and according with Gibbs free energy, the adsorption process was spontaneous at high temperature. The praseodymium in the hydroxyapatite is stable, it could not be desorbed using different solutions (ammonium sulfate, calcium chloride, sodium chloride, hydrochloric acid, and sodium hydroxide).

The effect of countermovement on force production capacity depends on extension velocity: A study of alpine skiers and sprinters.

In jumping, countermovement increases net propulsive force and improves performance. We aimed to test whether this countermovement effect is velocity specific and examine the degree to which this varies between athletes, sports or performance levels. Force-velocity profiles were compiled in high-level skiers (N= 23) and sprinters (N= 30), with their performance represented in their overall world ranking and season-best 100 m time, respectively. Different ratios between force-velocity variables were computed from squat and countermovement jumps (smaller = less effect): jump height (CRh), maximum power (CRP), force (CRF), and velocity (CRv). Countermovement effect differed per velocity (inverse relationship between CRF and CRv, rs = -0.74, p< .001), and variation force-velocity profiles with countermovement. Skiers exhibited smaller CRF (rrb = -0.675, p< .001), sprinters smaller CRv (rrb = 0.426, p= .008), and "moderate" velocity conditions did not differentiate groups (CRP or CRh, p> .05). 33% of the variance in skiers' performance level was explained by greater maximum force and a lower CRF (i.e., high explosiveness at low-velocities without countermovement), without an association for sprinters. Countermovement effect appears specific to movement velocity, sport and athlete level. Consequently, we advise sports-specific assessment, and potentially training to reduce the countermovement effect per the relevant velocity.

Step-to-Step Kinematic Validation between an Inertial Measurement Unit (IMU) 3D System, a Combined Laser+IMU System and Force Plates during a 50 M Sprint in a Cohort of Sprinters.

The purpose was to compare step-by-step kinematics measured using force plates (criterion), an IMU only and a combined laser IMU system in well-trained sprinters. Fourteen male experienced sprinters performed a 50-m sprint. Step-by-step kinematics were measured by 50 force plates and compared with an IMU-3D motion capture system and a combined laser+IMU system attached to each foot. Results showed that step kinematics (step velocity, length, contact and flight times) were different when measured with the IMU-3D system, compared with force plates, while the laser+IMU system, showed in general the same kinematics as measured with force plates without a systematic bias. Based upon the findings it can be concluded that the laser+IMU system is as accurate in measuring step-by-step kinematics as the force plate system. At the moment, the IMU-3D system is only accurate in measuring stride patterns (temporal parameters); it is not accurate enough to measure step lengths (spatial) and velocities due to the inaccuracies in step length, especially at high velocities. It is suggested that this laser+IMU system is valid and accurate, which can be used easily in training and competition to obtain step-by step kinematics and give direct feedback of this information during training and competition.

Resistance Training to Failure vs. Not to Failure: Acute and Delayed Markers of Mechanical, Neuromuscular, and Biochemical Fatigue.

ABSTRACT: González-Hernández, JM, García-Ramos, A, Colomer-Poveda, D, Tvarijonaviciute, A, Cerón, J, Jiménez-Reyes, P, and Márquez, G. Resistance training to failure vs. not to failure: acute and delayed markers of mechanical, neuromuscular, and biochemical fatigue. J Strength Cond Res 35(4): 886-893, 2021-This study aimed to compare acute and delayed markers of mechanical, neuromuscular, and biochemical fatigue between resistance training sessions leading to or not to failure. Twelve resistance-trained men completed 2 sessions that consisted of 6 sets of the full-squat exercise performed against the 10 repetitions maximum load. In a randomized order, in one session the sets were performed to failure and in the other session the sets were not performed to failure (5 repetitions per set). Mechanical fatigue was quantified through the recording of the mean velocity during all repetitions. The neuromuscular function of the knee extensors was assessed through a maximal voluntary contraction and the twitch interpolation technique before training, immediately after each set, and 1, 24, and 48 hours post-training. Serum creatine kinase (CK) and aspartate aminotransferase (AST) were measured before training and 1, 24, and 48 hours post-training to infer muscle damage. Alpha was set at a level of 0.05. A higher velocity loss between sets was observed during the failure protocol (-21.7%) compared with the nonfailure protocol (-3.5%). The markers of peripheral fatigue were generally higher and long lasting for the failure protocol. However, the central fatigue assessed by the voluntary activation was comparable for both protocols and remained depressed up to 48 hours post-training. The concentrations of CK and AST were higher after the failure protocol revealing higher muscle damage compared with the nonfailure protocol. These results support the nonfailure protocol to reduce peripheral fatigue and muscle damage, whereas the central fatigue does not seem to be affected by the set configuration.

Concurrent Validity and Reliability of a Low-Cost Dynamometer to Assess Maximal Isometric Strength in Neck Movements.

OBJECTIVE: This study aimed to evaluate the concurrent validity and reliability of a low-cost digital dynamometer to assess maximal isometric strength in neck movements. METHODS: Twelve recreationally active participants (6 women, 6 men; age: 24.1 ± 3.4 years; height: 1.71 ± 0.06 m; weight: 64.6 ± 11.7 kg) performed neck flexion, extension, and lateral flexion, and maximal isometric strength was simultaneously measured using an isokinetic dynamometer (gold standard) and a digital dynamometer to evaluate the concurrent validity of the latter. One week later, all the participants repeated 3 trials of each neck movement (3 minutes apart) registered only with the digital dynamometer. The first and second trial were guided by tester 1 and the third trial was guided by tester 2. RESULTS: The concurrent validity of the digital dynamometer showed a nearly perfect correlation between both devices (r > 0.986, P < .001), with Bland-Altman plots showing absolute agreement. Intertester and intratester reliability were nearly perfect for all neck movements (intraclass correlation coefficient > 0.86). CONCLUSION: The low-cost digital dynamometer showed valid and reliable measurements of maximal isometric strength in neck movements.

Effects of two drop-jump protocols with different volumes on vertical jump performance and its association with the force-velocity profile.

PURPOSE: This study aimed to evaluate the changes in countermovement jump (CMJ) height after two drop-jump (DJ) protocols with different volumes, and to explore the possibility of predicting the changes in CMJ height based on the vertical force-velocity (F-v) profile. METHOD: Thirty-four male athletes (age: 21.9 ± 2.0 years) were tested on three occasions. The F-v profile during the CMJ exercise was determined in the first session. Two DJ protocols (low-volume [1 set of 5 DJ trials from a 30 cm height] and high-volume [3 sets of 5 DJ trials from a 30 cm height]) were randomly performed during the second and third sessions, and the unloaded CMJ height was evaluated before (Pre), 4 min (Post4), 8 min (Post8), and 12 min (Post12) after the DJ protocol. RESULTS: CMJ height was significantly higher at Post4 (2.5 cm [95% confidence interval (CI) = 2.0-3.0 cm]; ES = 0.35), Post8 (2.1 cm [95% CI = 1.4-2.8 cm]; ES = 0.29) and Post12 (2.2 cm [95% CI = 1.4-3.0 cm]; ES = 0.30) compared to Pre. The only significant interaction (protocol × time) was caused by a higher increment in CMJ height at Post4 for the low-volume (8.1 ± 3.7%) compared to the high-volume (5.8 ± 3.9%) protocol. The F-v profile did not explain a significant part of the change in CMJ height (variance explained < 10%). CONCLUSIONS: These results suggest that low-volume DJ protocols could be more efficient to acutely increase CMJ performance, while the change in CMJ height was not affected by the F-v profile.

Effects of Combining Running and Practical Duration Stretching on Proprioceptive Skills of National Sprinters.

Romero-Franco, N, Párraga-Montilla, JA, Molina-Flores, EM, and Jiménez-Reyes, P. Effects of combining running and practical duration stretching on proprioceptive skills of national sprinters. J Strength Cond Res 34(4): 1158-1165, 2020-Practical duration stretching after aerobic activities is a recommended component of the first part of warm-up because of its effects on performance. However, its effects on proprioceptive skills are unknown. This study aimed to analyze the effects of running and practical duration static stretching (SS) and dynamic stretching (DS) on postural balance and the joint position sense (JPS) of national sprinters. Thirty-two national sprinters were randomly classified into a SS group (n = 11), DS group (n = 11), or control group (n = 10). Static stretching performed 5 minutes of running and short-duration (20 seconds) static stretches; DS performed 5 minutes of running and short-duration dynamic (20 seconds) stretches; and the control group performed 5 minutes of running. Before and after the intervention, unipedal static postural balance and knee JPS were evaluated. Static stretching exhibited a more centralized center of pressure in the medial-lateral plane for unipedal static postural balance in right-leg support after stretching (p = 0.005, d = 1.24), whereas DS showed values further from the center after stretching for the same unipedal support compared with baseline (p = 0.042, d = 0.49), and the control group remained stable (p > 0.05). Joint position sense did not show significant differences in any group (p > 0.05). In conclusion, combining running and practical duration SS may be beneficial for right-leg postural stabilization, whereas DS may be partly and slightly deleterious. Both SS and DS combined with running and running alone have neutral effects on knee JPS. Sports professionals should consider running and practical duration SS as part of the warm-up of sprinters to partly improve unipedal static postural balance.

Mechanical, Metabolic, and Perceptual Acute Responses to Different Set Configurations in Full Squat.

González-Hernández, JM, García-Ramos, A, Castaño-Zambudio, A, Capelo-Ramírez, F, Marquez, G, Boullosa, D, and Jiménez-Reyes, P. Mechanical, metabolic, and perceptual acute responses to different set configurations in full squat. J Strength Cond Res 34(6): 1581-1590, 2020-This study aimed to compare mechanical, metabolic, and perceptual responses between 2 traditional (TR) and 4 cluster (CL) set configurations. In a counterbalanced randomized order, 11 men were tested with the following protocols in separate sessions (sets × repetitions [interrepetition rest]): TR1: 3 × 10 [0 seconds]; TR2: 6 × 5 [0 seconds]; CL1: 3 × 10 [10 seconds]; CL2: 3 × 10 [15 seconds]; CL3: 3 × 10 [30 seconds]; CL4: 1 × 30 [15 seconds]. The exercise (full squat), number of repetitions (30), interset rest (5 minutes), and resistance applied (10 repetition maximum) was the same for all set configurations. Mechanical fatigue was quantified by measuring the mean propulsive velocity during each repetition and the change in countermovement jump height observed after each set and after the whole training session. Metabolic and perceptual fatigue were assessed via the blood lactate concentration and the OMNI perceived exertion scale measured after each training set, respectively. The mechanical, metabolic, and perceptual measures of fatigue were always significantly higher for the TR1 set configuration. The 2 set configurations that most minimized the mechanical measures of fatigue were CL2 and CL3. Perceived fatigue did not differ between the TR2, CL1, CL2, and CL3 set configurations. The lowest lactate concentration was observed in the CL3 set configuration. Therefore, both the CL2 and CL3 set configurations can be recommended because they maximize mechanical performance. However, the CL2 set configuration presents 2 main advantages with respect to CL3 (a): it reduces training session duration, and (b) it promotes higher metabolic stress, which, to some extent, may be beneficial for inducing muscle strength and hypertrophy gains.