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Purpose: The aim of the present study was to analyze the effect of different eccentric tempos on eccentric kinetics and kinematics and the subsequent concentric performance when performing countermovement jumps against different loads. Methods: After 1-repetition-maximum assessment and 2 familiarization sessions, 13 well-trained participants performed, in randomized order, 12 sets (4 tempos × 3 loads) of 4 repetitions of the loaded countermovement-jump exercise. The eccentric tempos analyzed were 5 and 2 seconds, as fast as possible, and accelerated (ie, without pause between repetitions), while the loads used were 30%, 50%, and 70% of 1-repetition maximum. Several kinetic and kinematic variables during both phases were recorded by linking a linear position transducer to the barbell. Results: The eccentric work was greater in the accelerated condition despite no changes in the eccentric depth. The peak and mean propulsive velocities were greater in the as-fast-as-possible and accelerated conditions. Correlation analysis showed that, compared with the 5-second condition, the increased concentric performance in the accelerated condition was related to the difference in eccentric work performed in the last 100 milliseconds of the eccentric phase (r >.770). Conclusions: Contrary to current practices, the current study highlights the need for performing the eccentric phase of loaded countermovement jumps, a common exercise performed by athletes for both training and evaluation purposes, as fast as possible. This allows not only a greater eccentric work but also improved concentric performance. [ABSTRACT FROM AUTHOR]

Analysis of variability in physiological time series has been shown to be an indicator of the state of the organism. Although there is evidence of the usefulness of analysis of the amount and/or structure of variability (complexity) in cycling actions, there is limited knowledge about its application in resistance exercise. The aim of this study is to find out whether variability in acceleration signals can be an indicator of intensity level in a squat task. For this purpose, an experimental design was developed in which the following participated seventy-two participants (age = 25.7 ± 4.4 years; height = 169.2 ± 9.8 cm; body mass = 67.7 ± 11.2 kg; ratio 1RM/body mass = 1.4 ± 0.3). They performed four repetitions of back squat at loads of 10%, 30%, 50%, 70%, and 90% of 1RM. Acceleration during the exercise was recorded using an inertial measurement unit (IMU) and a force platform. The variability of the movement was then analyzed using Standard Deviation (SD), Detrended Fluctuation Analysis (DFA), Fuzzy Entropy (FuzzyEn), and Sample Entropy (SampEn). For the IMU and for the force platform, significant effects were observed in all variables (p < 0.001). In pairwise comparisons, IMU showed a significant increase in motor complexity with increasing intensity, among most intensities, in DFA, FuzzyEn and SampEn. Differences in force platform were more limited, and only DFA detected differences between most intensities. The results suggest that measures of signal and acceleration variability may be a useful indicator of the relative intensity at which a squat exercise is performed. [ABSTRACT FROM AUTHOR]

Resistance training programs play a crucial role in optimizing soccer performance. The aim of this study is to compare performance outcomes in sport-specific tasks after implementing two different flywheel resistance training (FRT) programs: variable intensity (VI) and constant intensity (CI). Seventeen (n = 17) amateur footballers were divided into VI and CI groups with the same training volume. For the VI group, a decrease in inertial load was implemented every four sessions, whereas the CI group maintained a constant load during the entire program. After different familiarization sessions and testing (sprint, change of direction, jump, one-repetition maximum and flywheel strength variables), ten sessions of FRT were performed over 5 weeks. Both groups showed similar improvements in the one-repetition maximum (p < 0.01) but the CI group had significant improvements in the 10-m sprint (p = 0.04; ES = 0.72), emphasizing the potential benefits of medium inertial loads to maximize power and specificity in sport tasks. However, no significant differences were observed in the countermovement jump, change of direction and 30-m sprint, possibly attributed to neuromuscular fatigue from a high-volume training schedule and friendly matches. The study highlights the importance of considering training load distribution in FRT programs. The findings emphasize the need for complementary training to maximize the jump and change of direction abilities and caution against high-volume training and friendly match scenarios. In conclusion, FRT programs, whether varying in intensity or not, can yield medium-term performance improvements for soccer players. [ABSTRACT FROM AUTHOR]

BACKGROUND: Body tilt changes could affect the intensity/difficulty of core stability exercises, but there is still a lack of knowledge about its impact. OBJECTIVE: To analyse the trunk muscles activation during prone plank exercises at different body tilts. METHODS: Twenty-four young adults who performed recreational gymnastic activities participated in this study. Electromyography activity of the rectus abdominis (RA), external oblique (EO), internal oblique (IO) and erector spinae (ES) was recorded during the performance of six variations of the prone plank exercise (planking with feet supported on the ground [conventional horizontal position] and planking with feet supported on wall bars at five different heights increasing the angle tilt) and an inverted position exercise. RESULTS: The RA, EO and IO activation in all prone plank variations were higher than those observed in the conventional prone plank. In addition, the coefficient of variation of the muscle activation increased with the declination angle, reaching the highest values in the inverted position for the RA and ES muscles. CONCLUSION: The results seem to indicate that the body tilt variation could be used as an easy and inexpensive strategy for modulating the neuromuscular demands and the motor control challenge during planking exercises. [ABSTRACT FROM AUTHOR]

CrossFit is characterized by being a standardized training program that improves physical performance through the provision of several stimuli regardless of the participant's strength level. This study aimed to compare the acute response in total repetitions as a measurement of performance, jump ability, physiological demand (heart rate and blood lactate), and perceived effort considering the participants' strength level with individualized intensity in CrossFit. Thirty-five participants were assessed and asked to participate on two separate days in a standardized and relative 'As Many Repetitions As Possible' (AMRAP) CrossFit circuit. Both AMRAPs comprised strength, gymnastic and aerobic exercises, although only strength was individualized according to the participant's level. Before the statistical analysis, participants were allocated to higher- or lower-strength groups following the one-repetition maximum-bodyweight ratio in the push press exercise. Results support the existence of a strong relationship between strength level and total repetitions in both AMRAPs. In addition, differences in total repetitions and rate of perceived exertion between strength groups are discarded when AMRAP intensity is individualized while physiological demand and jump ability are maintained. Thus, the higher-strength participants may benefit from similar responses with a lower number of repetitions. Therefore, CrossFit trainers should be encouraged to prescribe strength tasks based on the percentage of 1RM for every training. [ABSTRACT FROM AUTHOR]

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Flywheel resistance training is a very useful method to optimize athletic performance. However, research assessing the different loading conditions hypothesis during flywheel resistance training is scarce. The aim of this study was to assess the influence of the loading conditions used during flywheel resistance exercise on improvements in athletic performance. Twenty nine (29) athletes were randomly assigned to three different flywheel resistance training groups: vertical-directed exercises (VR), horizontal-directed exercises (HR) and a mixed group (MIX). Performance assessment included one repetition maximum (1-RM) in the half-squat exercise, countermovement jump (CMJ) performance and change of direction (COD) ability (5-0-5 agility test). For the 1-RM squat, significant improvements were found in the VR (p = 0.011) and MIX groups (p = 0.015). All groups showed significant increases in CMJ height (p < 0.05), and significant decreases in 5-0-5 time with the non-dominant leg (p < 0.05). As regards 5-0-5 with the dominant leg, the VR (p = 0.004) and MIX groups (p = 0.001) showed significant decreases in 5-0-5 time. Non-significant group × time interactions were noted. In conclusion, all groups showed similar improvements in 1-RM squat, jumping and COD performance. However, the inclusion of vertical-directed exercises seems to optimize increases in 1-RM squat. [ABSTRACT FROM AUTHOR]

To assess the influence of age and skill level on handball throwing kinematics and performance, 126 participants were distributed into groups according to their skill level (elite or recreational) and age group (U12, U16 or +18). Each participant performed three sets of 10 throws, aiming to hit a target (40 × 40 cm) located in the right corner of the goal. During testing, kinematic data were recorded and throwing performance (accuracy and velocity) was measured. Results showed greater throwing velocity in the elite compared to recreational groups, whereas no differences were found for throwing accuracy. The elite U16 and +18 groups displayed higher segment velocities (hand, arm and pelvis) than the recreational groups. The participation of proximal segments was higher in older groups, showing the more skilled players (U16 and +18) greater pelvis velocities (1.62–1.75 vs 1.02–1.22 m/s). The increased velocity of the distal joints (hand peak velocity: 13.56 ± 1.65 vs 10.67 ± 1.98 m/s) are responsible for the difference in throwing velocity between the elite and recreational U12 groups. Several correlations were found between joint kinematics and throwing velocity. Coaches could use these results during training, to optimise specific throwing training. [ABSTRACT FROM AUTHOR]

Background: A main goal of programming is to structure the optimal variations in training factors to optimize athletes' adaptations. Nevertheless, it remains unknown the optimal programming model leading to greater neuromuscular adaptations. Purpose: The aim of the present study was to assess the influence of three different magnitudes of variability within resistance training programs on performance adaptations. Methods: Forty participants were assigned to three different groups differing in the frequency of change in training contents: a weekly model (WM; n = 12), a daily model (DM; n= 14), and a session model (SM; n = 14). The training intervention lasted for six weeks, performing two sessions per week of back-squat exercise. Total training load (volume and intensity) of the six-week intervention was equated for all groups. Maximum dynamic strength (1RM) in the back-squat, countermovement (CMJ) and squat jump (SJ) were measured pre- and post-training intervention. Results: All groups showed significant increases (p<.05) in 1RM, with the SM showing greater increases than the WM (20.5 vs 13.6%; p=.022). Although not reaching statistical significance, the magnitude of the increases in CMJ tended to be greater for DM and SM group (9.5% and 8.1%, respectively,) than in the WM (4.4%). All groups showed similar increases in the SJ (7.7–9.9%). Conclusions: The results of the present study suggest that the use of more frequent stimuli variations within resistance training programming is a key factor to achieve concomitant increases in strength and jumping performance. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the reliability and validity of vertical and horizontal jump tests in football players with cerebral palsy (FPCP) and to analyze the jump performance differences between current International Federation for Cerebral Palsy Football functional classes (ie, FT5-FT8).Methods: A total of 132 international parafootballers (25.8 [6.7] y; 70.0 [9.1] kg; 175.7 [7.3] cm; 22.8 [2.8] kg⋅m-2; and 10.7 [7.5] y training experience) participated in the study. The participants were classified according to the International Federation for Cerebral Palsy Football classification rules, and a group of 39 players without cerebral palsy was included in the study as a control group. Football players' vertical and horizontal jump performance was assessed. Results: All the tests showed good to excellent relative intrasession reliability scores, both in FPCP and in the control group (intraclass correlation = .78-.97, SEM < 10.5%). Significant between-groups differences (P < .001) were obtained in the countermovement jump, standing broad jump, 4 bounds for distance, and triple hop for distance dominant leg and nondominant leg. The control group performed higher/farther jumps with regard to all the FPCP classes, obtaining significant differences and moderate to large effect sizes (ESs) (.85 < ES < 5.54, P < .01). Players in FT8 class (less severe impairments) had significantly higher scores in all the jump tests than players in the lower classes (ES = moderate to large, P < .01). Conclusions: The vertical and horizontal jump tests performed in this study could be applied to the classification procedures and protocols for FPCP. [ABSTRACT FROM AUTHOR]

Purpose: To analyze the effects of different inertial loads on power production and power maintenance, as well as the number of sessions required for proper familiarization during the flywheel quarter-squat. Methods: Twenty-four high-level handball players attended 4 testing sessions consisting of 4 sets of 10 repetitions using 4 different inertial loads (0.025, 0.050, 0.075, and 0.100 kg⋅m²). In addition, a 5th set of 15 repetitions was performed. Both concentric and eccentric peak power and the eccentric: concentric ratio were recorded. Results: The results showed the need to perform 3 sessions for a proper familiarization (ie, outcomes stabilization). The inertial load of 0.025 kg⋅m² led to greater concentric peak power compared with the other inertial loads (from likely to most likely greater values). Both 0.025 and 0.050 kg⋅m² inertial loads entailed greater eccentric peak power compared with 0.075 and 0.100 kg⋅m² (most likely greater). Conversely, the 0.025-kg⋅m² inertial load showed a lower eccentric: concentric ratio, presenting negative effects (most likely lower values) compared with the inertial loads of 0.050, 0.075, and 0.100 kg⋅m². Participants were able to perform 5-12 repetitions per set without significant peak power output decrements. Conclusions: This study highlights the importance of performing at least 3 sessions to obtain a stable measure during flywheel squat exercise. Lower inertial loads (0.025 kg⋅m²) are the better option for eliciting high concentric peak power output values. In contrast, medium to high inertial loads are more appropriate to achieve greater eccentric overload values. [ABSTRACT FROM AUTHOR]

This systematic review and meta-analysis aimed to assess the effect of using weightlifting movement and their derivatives in training on vertical jump, sprint times, and maximal strength performance. Thirty-four studies were used for meta-analysis with a moderate quality on the PEDro scale. Meta-analysis showed positive effects of weightlifting training, especially when combined with traditional resistance training on countermovement jump performance, sprint times, and one-repetition maximum squat (ES = 0.41, ES = −0.44, and ES = 0.81, respectively). In conclusion, results revealed the usefulness of weightlifting combined with traditional resistance training in improving sprint, countermovement jump and maximal strength performance. [ABSTRACT FROM AUTHOR]

The aim of this study consists of the application of an experimental protocol that allows information to be obtained about the visual search strategies elaborated by swimming coaches. 16 swimming coaches participated. The Experienced group (n=8) had 16.1 yr. (SD=8.2) of coaching experience and at least five years of experience in underwater vision. The Nonexperienced group in underwater vision (n = 8) had 4.2 yr. (SD = 4.0) of coaching experience. Participants were tested in a laboratory environment using a video-projected sample of the crawl stroke of an elite swimmer. This work discusses the main areas of the swimmer's body used by coaches to identify and analyse errors in technique from overhead and underwater perspectives. In front-underwater videos, body roll and mid-water were the locations of the display with higher percentages of fixation time. In the side-underwater slow videos, the upper body was the location with higher percentages of visual fixation time and was used to detect the low elbow fault. Side-overhead takes were not the best perspectives to pick up information directly about performance of the arms; coaches attended to the head as a reference for their visual search. The observation and technical analysis of the hands and arms were facilitated by an underwater perspective. Visual fixation on the elbow served as a reference to identify errors in the upper body. The sideunderwater perspective may be an adequate way to identify correct knee angles in leg kicking and the alignment of a swimmer's body and leg actions.