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Cross-education has been studied extensively with adults, examining the training effects on contralateral homologous muscles. There is less information on the cross-education effects on contralateral heterologous muscles and scant information comparing these responses between adults and youth. The objective was to compare cross-education training effects in male youth and adults to contralateral homologous and heterologous muscles. Forty-two male children (10-13-years) and 42 adults (18-21-years) were tested before and following an 8-week unilateral, dominant or nondominant arm, chest press (CP) training program or control group (14 subjects each). Unilateral testing assessed dominant and nondominant limb strength with leg press and CP 1 repetition maximum (1RM), knee extensors, elbow extensors (EE), elbow flexors, and handgrip maximum voluntary isometric contraction (MVIC) strength and shot put distance and countermovement jump height. Upper-body tests demonstrated large magnitude increases, with children overall exceeding adults (p = 0.05- p < 0.0001, η² : 0.51, 10.4 ± 11.1%). The dominant trained limb showed significantly higher training adaptations than the nondominant limb for the adults with CP 1RM ( p = 0.03, η² : 0.26, 6.7 ± 11.5%) and EE ( p = 0.008, η² : 0.27, 8.8 ± 10.3%) MVIC force. Unilateral CP training induced significantly greater training adaptations with the ipsilateral vs. contralateral limb ( p = 0.008, η² : 0.93, 27.8 ± 12.7%). In conclusion, children demonstrated greater training adaptations than adults, upper-body strength increased with no significant lower-body improvements, and ipsilateral training effects were greater than contralateral training in adults. [ABSTRACT FROM AUTHOR]

The present work described the enhanced photodegradation of the Congo Red (CR) dye under visible light irradiation. The co-doped ceria (Ce0.7La0.15Ca0.15O2−δ) was prepared by the colloidal solution combustion synthesis way using colloidal silica as a template. The characterization of the as-synthesized cerium oxide (CeO2, known as ceria) nanoparticles was assessed by diffraction, scanning electron microscopy, Raman spectroscopy, differential thermal analysis, thermοgravimetric analysis, ultraviolet (UV)–visible spectroscopy, and photoluminescence measurements. It revealed the cubic spinel structure with space group Fd-3 m (JCPDS card No. 34-0394), average size between 23 and 92 nm, and bandgap energy from 2.69 to 2.73 eV. The photodegradation of the CR dye under solar irradiation allowed studying the photocatalytic activities of the prepared ceria. After 180 min of light irradiation with the ceria 2 catalyst, CR absorbance was almost nil. The highest degradation rate ∼13.7 × 10−4 min−1 was recorded using co-doped ceria prepared with adding 1.0 ml of colloidal silica. This exciting activity can be attributed to the smallest particle size ∼23 nm, the smallest lattice parameter a = 5.4511 Å, and the catalyst's highest bandgap ∼2.73 eV. Based on the investigation, ceria 2 nanoparticles have many possible uses in wastewater cleaning agent. Ceria 2 catalysts might be ideal for photocatalyst materials, UV filters, and photoelectric devices. [ABSTRACT FROM AUTHOR]

Purpose: Whereas cross-education has been extensively investigated with adults, there are far fewer youth investigations. Two studies suggested that children had greater global responses to unilateral knee extensor fatigue and training, respectively, than adults. The objective of this study was to compare global training responses and cross-education effects after unilateral elbow flexion (EFlex) and leg press (LP) training. Methods: Forty-three prepubertal youths (aged 10–13 y) were randomly allocated into dominant LP (n = 15), EFlex (n = 15) training groups, or a control (n = 13). Experimental groups trained 3 times per week for 8 weeks and were tested pretraining and posttraining for ipsilateral and contralateral 1-repetition maximum LP; knee extensor, knee flexors, elbow flexors; and handgrip maximum voluntary isometric contractions (MVIC), and countermovement jump. Results:In comparison to no significant changes with the control group, dominant elbow flexors training demonstrated significant (P <.001) improvements only with ipsilateral and contralateral upper body testing (EFlex MVIC [15.9–21.5%], EFlex 1-repetition maximum [22.9–50.8%], handgrip MVIC [5.5–13.8%]). Dominant LP training similarly exhibited only significant (P <.001) improvements for ipsilateral and contralateral lower body testing (LP 1-repetition maximum [59.6–81.8%], knee extensor MVIC [12.4–18.3%], knee flexor MVIC [7.9–22.3%], and countermovement jump [11.1–18.1%]). Conclusions: The ipsilateral and contralateral training adaptations in youth were specific to upper or lower body training, respectively. [ABSTRACT FROM AUTHOR]

Chaouachi, A, Ben Othman, A, Chaouachi, M, Hechmi, A, Farthing, JP, Granacher, U, and Behm, DG. Comparison of cross-education and global training effects in adults and youth after unilateral strength training. J Strength Cond Res 36(8): 2121–2131, 2022—Youth strength training research examining contralateral, homologous (cross-education), and heterologous (global training) effects after unilateral training have provided mixed results and the relationship to adults has not been compared. The objective was to compare adult and youth cross-education and global training effects on dominant and nondominant limb testing. Initially, 15 men and 15 prepubertal boys volunteered for each unilateral chest press (CP), handgrip training, and control groups (n = 89). Individuals trained their dominant limb 3 times per week for 8 weeks and had their dominant and nondominant limbs tested for CP and leg press 1 repetition maximum (1RM), handgrip, knee extension and flexion, and elbow extension and flexion maximum voluntary isometric contractions (MVICs). Adult CP training gains were significantly greater than youth with lower-body testing (p = 0.002–0.06), whereas youth CP training gains exceeded adults with upper-body tests (p = 0.03–0.07). Training specificity was evident with greater CP 1RM increases with CP vs. handgrip training for both youth (p < 0.0001) and adults (p < 0.0001). Handgrip training elicited greater gains in handgrip MVICs compared with other strength tests (p < 0.0001). In conclusion, only contralateral CP 1RM showed a training advantage for unilateral CP over unilateral handgrip training. Adults showed greater gains with lower-body testing, whereas youth showed greater gains with upper-body testing. [ABSTRACT FROM AUTHOR]

Dellal, A, Keller, D, Carling, C, Chaouachi, A, Wong, DP, and Chamari, K. Physiologic effects of directional changes in intermittent exercise in soccer players. J Strength Cond Res 24(12): 3219-3226, 2010--The aim of the present study was to compare the physiologic impact of intermittent exercise in specific shuttle running (IS), which requires 180 [degrees] directional changes, and traditional in-line (IL) running. Ten elite male adult soccer players performed different intermittent exercises according to their maximal aerobic velocity (v[??][O.sub.2]max): 30-30 seconds at 100% (30 s of runs at 100% of v[??][O.sub.2]max alternated with 30-s recovery period), 105%, and 110% of v[??][O.sub.2]max with active recovery, 15-15 seconds at 105%, 110%, and 115% of v[??][O.sub.2]max, and 10-10 seconds at 110%, 115%, and 120% of v[??][O.sub.2]max with passive recovery. Each exercise was performed in the IL and IS format in a randomized order. Heart rate (HR) expressed in percentage of HR reserve (HRres), postexercise blood lactate concentration [La], and ratings of perceived exertion (RPE) were recorded. The different 30-30 seconds showed significantly higher HRres responses in IS compared with IL (p < 0.01 ). The [La] and RPE results indicated higher values in IS. In conclusion, the physiologic impact of specific IS is substantially higher than in traditional IL. The changes of direction induce an increase in the anaerobic metabolism solicitation and consequently create different responses compared with traditional IL running. This information can aid coaches in the design of intermittent training programs using classical (IL) or a specific form (IS) of running to induce different physiologic responses. KEY WORDS intermittent exercise, football, fitness training, anaerobic metabolism, 180 [degrees], turning

The purpose of this study was to determine the relationship between squat loads and 2 bilateral and 2 unilateral stepping lower-body exercises in predominantly unilateral movement elite athletes (Karate). Equations to predict loads for lower-body exercises based on the squat load were also determined. Fourteen male elite Karate athletes (age = 22.6 [+ or -] 1.2 years) performed 6 repetition maximum (RM) of the following free-weight bilateral exercises: back half squat, deadlift, leg press and unilateral stepping exercises, lunge; and step-up. Results showed that 6RM squat load was significantly (p < 0.001) correlated with deadlift (r = 0.86), leg press (r = 0.76), lunge (r = 0.86), and step-up (r = 0.92). Linear regression showed that the 6RM squat load was a significant predictor for deadlift, leg press, lunge, and step-up ([R.sup.2] range from 0.57 to 0.85, p < 0.001). The following 6RM prediction equations were determined: (a) Deadlift = squat load (1.12)-16.60 kg, (b) Leg press = squat load (1.66) + 16.10 kg, (c) Lunge = squat load (0.61) + 9.39 kg, and (d) step-up = squat load (0.85)-10.36 kg. Coaches and fitness professionals can use the 6RM squat load as a time effective and accurate method to predict training loads for both bilateral and unilateral lower-body exercises with quadriceps as the prime mover. Load prescriptions for unilateral exercises should take into account the type of athletic population. KEY WORDS load estimates, resistance strength unilateral, bilateral

The ability to perform high-intensity intermittent exercise (i.e., Yo-Yo Intermittent Recovery Test [Yo-Yo IR1]) and to repeat sprints with relatively short recovery times (i.e., 20- to 30-seconds, relatively short time interval [repeated sprint ability (RSA)]) has been shown to be relevant fitness variables in soccer. However, though they potentially share common features, it is not known whether these 2 abilities are associated. The aim of this study was to examine the relationships between Yo-Yo IR1 and RSA performances in elite soccer players. Twenty-three soccer players (age 19 [+ or -] 1 years, height 181 [+ or -] 5.7 cm, body mass 73.2 [+ or -] 4.1 kg, %body fat 11 [+ or -] 2.4) performed the Yo-Yo IR1 and a test for RSA (7 x 30 m with 25-second recovery). Results were 2,289 [+ or -] 409 m, 31.21 [+ or -] 1.13 seconds, and 4 [+ or -] 2.1% for Yo-Yo IR1, total sprint time, and sprint decrement, respectively. Yo-Yo IR1 showed a significant and moderate relationship with sprint decrement (r = -0.44, p = 0.04). Splitting the sample into Best and Worst Yo-Yo IR1 performers according to median score (2,320 m), the Best group showed lower RSA total time (30.69 [+ or -] 0.99 vs. 31.79 [+ or -] 1.06, p < 0.05) and speed decrement (2.90 [+ or -] 0.86 vs. 5.09 [+ or -] 2.42, p < 0.01) compared to the Worst group. Sprint-time deterioration over 30 m occurred earlier (from the second sprint on) in the Yo-[Yo.sub.worst] compared with in the Yo-[Yo.sub.Best] group (from the fourth sprint on, p < 0.001). Intermittent high-intensity endurance is poorly associated with RSA performance ([r.sup.2] = 0.19). Consequently, coaches and strength and conditioning professionals should consider both Yo-Yo IR1 and RSA in their testing batteries. A Yo-Yo IR1 performance [greater than or equal to] 2,320 m could be considered as a reasonable indicator of physical fitness in elite soccer. Relatively short time interval test protocols similar to the present study should consist of at least 5 sprint bouts. KEY WORDS association football, field testing, performance analysis, fitness

Castagna, C, Manzi, V, Impellizzeri, F, Chaouachi, A, Ben Abdelkrim, N, and Ditroilo, M. Validity of an on-court lactate threshold test in young basketball players. J Strength Cond Res 24(9): 2434-2439, 2010--The aim of this study was to assess the criterion validity of a submaximal field test (Intermittent Shuttle-Running Test [ISRT]) for lactate threshold (LT) detection in young basketball players. Fourteen basketball players (age 15.3 [+ or-] 0.6 years, height 182 [+ or-] 4.6 cm, and body mass 71.6 [+ or-] 6.3 kg) were submitted in random order and on separate occasions, to ISRT (20-m shuttle running for 4 minutes at 9, 10 and 11 km x [h.sup.1]) and to a treadmill intermittent progressive test (criterion validity, TM) devised for the assessment of LT (4-minute stages at 8, 10, 12, 14 km x [h.sup.-1]). Blood-lactate concentrations [La]b were assessed taking earlobe blood samples at rest and immediately after each of the 4-minute running steps considered for ISRT and TM. Lactate threshold was considered as the running speed attained at 1 mmol x [L.sup.-1] [La]b above resting levels. Results showed that speed at LT during ISRT and TM was significantly related (r = 0.82, p < 0.001). However, speed at LT during the ISRT showed to be significantly lower than the speed at LT during TM (10.1 [+ or-] 1.7 vs. 12 [+ or-] 2.3 km x [h.sup.-1], p < 0.001). During ISRT, players attained 80 [+ or-] 4.7, 87 [+ or-] 4.4, and 92 [+ or -] 3.0% of maximal heart rate (HR) at 9, 10, and 11 km x [h.sup.-1], respectively. This study results show that ISRT may be used as a valid field test to assess submaximal aerobic fitness in young team-sport players. Continuous 20-m shuttle running performed at 11 km x [h.sup.1] revealed to elicit HR in the range of those reported to induce aerobic-fitness development in trained subjects. In light of study finding, ISRT may be considered in testing batteries for basketball players to complement anaerobic fitness and agility. KEY WORDS submaximal testing, team sports, anaerobic capacity

The objective of the present study was to investigate the effects of static and dynamic stretching alone and in combination on subsequent agility, sprinting, and jump performance. Eight different stretching protocols: (a) static stretch (SS) to point of discomfort (POD); (b) SS less than POD (SS KEY WORDS flexibility, stretch sequence, stretch intensity

The purpose of the present study was to compare the physical attributes of elite men's basketball players according to age and specific individual positional roles. Forty-five players from 3 national basketball teams (Under-18 years, Under-20 years, and Senior) were measured for anthropometry (height, body mass, percentage body fat), explosive power (5 jumps and vertical jump), speed (5-m, 10-m, and 30-m sprint), agility (T-test), strength (bench press and squat 1 repetition maximum [1RM]), and intermittent high-intensity endurance performance (Yo-Yo intermittent recovery test [Yo-Yo IR1]). Data on match frequency, training routines, and playing experience were also collected. Under-18 players were significantly (p < 0.05) shorter and lighter than both Senior and Under-20 players but showed higher (p < 0.05) percentage body fat. Under-20 and Senior players were faster and had better explosive-power and agility (p < 0.05) performances than Under-18 players. Bench press and squat 1RMs were higher in Senior players (p < 0.05) compared with the other groups. There were significant difference in the Yo-Yo IR1 performance among groups (Senior > Under-20 > Under-18, p < 0.05). Centers and power forwards were the tallest and the heaviest (p < 0.05). The Yo-Yo IR1 performance was higher (p < 0.01) in point guards than in centers. Point guards showed also better agility and 5- and 10-m performances. Power forwards and centers were stronger than the rest of players' positions in the bench press 1RM (p < 0.01). These results showed the existence of age and positional role differences in fitness performance in men's basketball. Differences were particularly evident in intermittent high-intensity endurance and agility performance. Sprint training possibly should be individualized when dealing with positional roles in elite men's basketball. Strength and conditioning coaches should use Yo-Yo IR1 to assess specific endurance in players of different age and positional role. Key Words team sports, physical fitness, strength, agility, explosive power, sprinting

The aim of this study was to examine the training load (TL) profile of professional elite level basketball players during the crucial parts of the competitive season (pre-play-off finals). Subjects were 8 full-time professional basketball players (age 28 [+ or -] 3.6 years, height 199 [+ or -] 7.2 cm, body mass 102 [+ or -] 11.5 kg, and body fat 10.4 [+ or -] 1.5%) whose heart rate (HR) was recorded during each training session and their individual response to TL monitored using the session-rate of perceived exertion (RPE) method (200 training sessions). The association between the session-RPE method and training HR was used to assess the population validity of the session-RPE method. Significant relationships were observed between individual session-RPE and all individual HR-based TL (r values from 0.69 to 0.85; p < 0.001). Coaches spontaneously provided a tapering phase during the competitive weeks irrespective of the number of games played during it (i.e., 1 or 2 games). The individual weekly players' TL resulted in being not significantly different from each other (p > 0.05). Elite male professional basketball imposes great physiological and psychological stress on players through training sessions and official competitions (1-2 per week). Consequently, the importance of a practical and valid method to assess individual TL is warranted. In this research, we demonstrated that session-RPE may be considered as a viable method to asses TL without the use of more sophisticated tools (i.e., HR monitors). The session-RPE method enabled the detection of periodization patterns in weekly planning in elite professional basketball during the crucial part of the competitive season (1 vs. 2 weekly fixtures model). Key Words periodization, team sports, conditioning, fitness assessment, heart rate

This study examined the effect of concurrent muscular strength and high-intensity running interval training on professional soccer players' explosive performances and aerobic endurance. Thirty-nine players participated in the study, where both the experimental group (EG, n = 20) and control group (CG, n = 19) participated in 8 weeks of regular soccer training, with the EG receiving additional muscular strength and high-intensity interval training twice per week throughout. Muscular strength training consisted of 4 sets of 6RM (repetition maximum) of high-pull, jump squat, bench press, back half squat, and chin-up exercises. The high-intensity interval training consisted of 16 intervals each of 15-second sprints at 120% of individual maximal aerobic speed interspersed with 15 seconds of rest. EG significantly increased (p [less than or equal to] 0.05) 1RM back half squat and bench press but showed no changes in body mass. Within-subject improvement was significantly higher (p [less than or equal to] 0.01) in the EG compared with the CG for vertical jump height, 10-m and 30-m sprint times, distances covered in the Yo-Yo Intermittent Recovery Test and maximal aerobic speed test, and maximal aerobic speed. High-intensity interval running can be concurrently performed with high load muscular strength training to enhance soccer players' explosive performances and aerobic endurance. KEY WORDS football, combined training, weight training, periodization, intermittent

The aim of the present study was to evaluate the influence of the Ramadan intermittent fast (RIF) on aerobic and anaerobic exercise performance in elite judo athletes (Judokas) maintaining their usual training loads. Physical performance tests (squat jump [SJ]), counter-movement jump [CMJ], 30-second repeated jump, 30-m sprint, and the multistage fitness test) and fatigue scores were measured in 15 elite Judokas on 4 occasions: before Ramadan (T1), at the beginning of Ramadan (T2), at the end of Ramadan (T3) and 3 weeks after Ramadan. Results showed that 30-m sprint performance, multistage shuttle run test, SJ, and CMJ did not change during Ramadan. However, average power during the 30-second repeated jump test was slightly lower at the end of Ramadan (22.4 [+ or -] 2.3 W/kg; P < 0.05) than before Ramadan (23.4 [+ or -] 2.3 W/kg). There was a minor reduction of 1.3 kg in body mass and an increase in total fatigue scores (T2, 19 [+ or -] 5; T3, 16 [+ or -] 4; both P < 0.05) during Ramadan in comparison with the control period (T1, 12 [+ or -] 3). These results show that the RIF has little effect on aerobic performance and on very short duration sprinting and jumping test performance in elite Judokas. Additionally, experienced athletes can maintain both sufficient energy intake and normal training loads during the RIF. The slight reduction in the 30-second jump test may be associated with reduced central drive and body mass. Collectively, these results suggest that the RIF has little effect on the performance of experienced Judokas, but Muslim athletes who train during the RIF should carefully periodize their training load and monitor their food intake and fatigue levels to avoid performance decrements. KEY WORDS Islamic fasting, sports, exercise, nutrition

The aim of this study was to examine the aerobic fitness and lower-limbs explosive-power abilities of Italian regional-level amateur basketball players. Participants were basketball players playing successfully at a senior (S, n = 11) and junior (J, n = 11) regional level. Players maximal oxygen uptake ([Vo.sub.2]max) was assessed with them wearing a portable gas analyzer (K4[b.sup.2], COSMED, Rome, Italy) during an exercise mode-specific multistage fitness test (yo-yo endurance test [Yo-Yo]). Knee extensors and plantar flexors explosive power was assessed with countermovement jump (CMJ) and stiff-leg jumps (SL), respectively. Jumps were performed using a switch mat connected to a computer (Muscle Lab, Bosco System, Rome, Italy). Jumps' fly (FT) and contact times (CT) were used for jump performances calculations. Stiff-Leg FT versus CT ratio (SL/CT) was considered as representative of lower-leg explosive power, whereas SL/CMJ x 100 was considered as sign of the explosive-power balance between lower and upper leg muscles. Players' [Vo.sub.2]max was 60.88 [+ or -] 6.26 and 50.33 [+ or -] 3.98 mL x [kg.sup.-1] x [min.sup.-1] for J and S, respectively (p < 0.05). A significant difference was found in SL/CT between S and J players. Yo-Yo performance was not significantly different between groups (2,055 [+ or -] 267 and 2,020 [+ or -] 174 m for S and J, respectively, p > 0.05). Lower-leg explosive power showed to be positively related to distance covered during Yo-Yo. Study results showed that 50 mL x [kg.sup.-1] x [min.sup.-1] is a sufficient [Vo.sub.2]max value for competing at a regional level. Calf explosive power should be considered to improve sport-specific running performance in basketball using plyometrics and whole body lifts. KEY WORDS team sports, maximal aerobic power, jumping ability, shuttle run test

The aims of this study were to examine the relationship between squat 1 repetition maximum (1RM) and basketball-relevant tests and the variables that influence agility (T-test) in elite male professional basketball players (n = 14, age 23.3 [+ or -] 2.7 years, height 195.6 [+ or -] 8.3 cm, body mass 94.2 [+ or -] 10.2 kg). T-test performance was significantly related to body mass (r = 0.58, p = 0.03) and to percentage of body fat (r = 0.80, p < 0.001). A significant negative correlation was observed between t-test and 5-jump test performance (r = -0.61, p = 0.02). Squat 1RM was significantly related to 5-, 10-, and 30-m sprint times. Stepwise correlation analysis showed percentage of body fat was the best single predictor factor (p < 0.05) of agility. Squat 1 RM performance was the best single predictor of 5-m and 10-m sprint times (p < 0.05). In light of the present study's findings, agility should be regarded as a per se physiological ability for elite basketball players. Consequently, basketball-specific agility drills should be stressed in elite basketball training. Given the association between squat 1RM performance and short sprint times, squat exercises should be a major component of basketball conditioning. KEY WORDS field test, team sports, squat performance, vertical jump

The purpose of this study was to examine the influence of the sequence order of high-intensity endurance training and circuit training on changes in muscular strength and anaerobic power. Forty-eight physical education students (ages, 21.4 [+ or -] 1.3 years) were assigned to 1 of 5 groups: no training controls (C, n = 9), endurance training (E, n = 10), circuit training (S, n = 9), endurance before circuit training in the same session, (E+S, n = 10), and circuit before endurance training in the same session (S+E, n = 10). Subjects performed 2 sessions per week for 12 weeks. Resistance-type circuit training targeted strength endurance (weeks 1-6) and explosive strength and power (weeks 7-12). Endurance training sessions included 5 repetitions run at the velocity associated with [Vo.sub.2]max ([Vo.sub.2]max) for a duration equal to 50% of the time to exhaustion at [Vo.sub.2]max; recovery was for an equal period at 60% [Vo.sub.2]max. Maximal strength in the half squat, strength endurance in the 1-leg half squat and hip extension, and explosive strength and power in a 5-jump test and countermovement jump were measured pre-and post-testing. No significant differences were shown following training between the S+E and E+S groups for all exercise tests. However, both S+E and E+S groups improved less than the S group in 1 repetition maximum (p < 0.01), right and left 1-leg half squat (p < 0.02), 5-jump test (p < 0.01), peak jumping force (p < 0.05), peak jumping power (p < 0.02), and peak jumping height (p < 0.05). The intrasession sequence did not influence the adaptive response of muscular strength and explosive strength and power. Circuit training alone induced strength and power improvements that were significantly greater than when resistance and endurance training were combined, irrespective of the intrasession sequencing. KEY WORDS plyometric training, combined training, interval training, interference effect

Purpose: To examine differences between ground-reaction-force (GRF)-based parameters collected from 5 types of plyometric push-ups. Between-trials reliability and the relationships between parameters were also assessed. Methods: Thirty-seven highly active commando soldiers performed 3 trials of 5 variations of the plyometric push-up in a counterbalanced order: standard countermovement push-up (SCPu), standard squat push-up (SSPu), kneeling countermovement push-up (KCPu), kneeling squat push-up (KSPu), and drop-fall push-up (DFPu). Vertical GRF was measured during these exercises using a portable Kistler force plate. The GRF applied by the hands in the starting position (initial force supported), peak GRF and rate of force development during takeoff, flight time, impact force, and rate of force development impact on landing were determined. Results: During standard-position exercises (SCPu and SSPu) the initial force supported and impact force were higher (P < .001) than with kneeling exercises (KCPu, KSPu, and DFPu). The peak GRF and rate of force development during takeoff were higher (P < .001) in the countermovement push-up exercises ([CMP] SCPu, KCPu, and DFPu) than squat push-up exercises ([SP] SSPu and KSPu). Furthermore, the flight time was greater (P < .001) during kneeling exercises than during standard-position exercises. A significant relationship (P < .01) between impact force and the rate of force development impact was observed for CMP and SP exercises (r = .83 and r = .62, respectively). The initial force supported was also negatively related (P < .01) to the flight time for both CMP and SP (r = -.74 and r = -.80, respectively). It was revealed that the initial force supported and the peak GRF during takeoff had excellent reliability; however, other parameters had poor absolute reliability. Conclusions: It is possible to adjust the intensity of plyometric push-up exercises and train athletes' muscle power by correctly interpreting GRF-based parameters. However, caution is required as some parameters had marginal absolute reliability. [ABSTRACT FROM AUTHOR]

Balance, strength and power relationships may contain important information at various maturational stages to determine training priorities. Purpose: The objective was to examine maturity-specific relationships of static/dynamic balance with strength and power measures in young male athletes. Method: Soccer players (N = 130) aged 10-16 were assessed with the Stork and Y balance (YBT) tests. Strength/power measures included back extensor muscle strength, standing long jump (SLJ), countermovement jump (CMJ), and 3-hop jump tests. Associations between balance with strength/power variables were calculated according to peak-height-velocity (PHV). Results: There were significant medium-large sized correlations between all balance measures with back extensor strength (r = .486-.791) and large associations with power (r = .511-827). These correlation coefficients were significantly different between pre-PHV and circa PHV as well as pre-PHV and post-PHV with larger associations in the more mature groups. Irrespective of maturity-status, SLJ was the best strength/power predictor with the highest proportion of variance (12-47%) for balance (i.e., Stork eyes opened) and the YBT was the best balance predictor with the highest proportion of variance (43-78%) for all strength/power variables. Conclusion: The associations between balance and muscle strength/power measures in youth athletes that increase with maturity may imply transfer effects from balance to strength/power training and vice versa in youth athletes. [ABSTRACT FROM AUTHOR]