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To investigate the status of dental caries and assess the effectiveness of dental caries prevention interventions in children from 3 to 5-year-old in Hue City, Vietnam.The subjects were 464 children and their direct caregivers at some kindergartens in Hue City from June 2020 to October 2021. The study included two consecutive phases: the first one was a cross-sectional study to identify the rate of dental caries and related factors in the studied kindergartens, and phase 2 was a controlled comparative interventional study for a period of 12 months.The mean of decayed, missing, filled, and DMFT index was 8.25, 0.09, 0.48, and 8.82, respectively, with no statistically significant difference in these figures between the living areas. The multivariable logistic regression model revealed some factors related to dental caries, including age, frequency of toothbrushing per day, parent-assisted toothbrushing, and eating and drinking sweets. Results showed the effectiveness of a community-based intervention for preventing dental caries, gingivitis, and plaque in the intervention group, compared to the control group.The rate of dental caries among Vietnamese children was remarkably high. A comprehensive intervention to prevent early childhood dental caries was effective and might be considered a necessary program in healthcare prophylaxis.This intervention was consistent with the guidelines of WHO and based on evidences of related factors of dental caries identified in a previous cross-sectional study.

Although previous research has investigated the training-specific adaptations to training in adults, there is a paucity of research aimed at investigating these adaptations in adolescent athletes. As such, adolescent athletes’ training-specific adaptations from three different training interventions were investigated in this study. Sixteen adolescent athletes participated in this study, whereby eight performed both training interventions and eight the non-training control. Pre- and post-testing was performed for each intervention with the testing battery: ultrasonography of the vastus lateralis and lateral gastrocnemius, countermovement jump, squat jump, and isometric mid-thigh pull. The resistance training group had large significant increases in isometric mid-thigh pull relative peak force ( p

Background: Surfing is a high skill sport that requires a considerable amount of time in a variety of ocean conditions to help develop the fundamental techniques. Objective: The purpose of this study was to investigate the effect of four weeks of detraining on strength, power, and sensorimotor ability in adolescent surfers. Methods: Nineteen adolescent surfers (13.8 A 1.7 y, 53.6 A 10.8 kg and 165.1 A 8.9 cm) participated in four weeks of detraining (surfing participation maintained but resistance training ceased) following seven weeks of periodized resistance training. Maximal isometric strength, power, and sensorimotor ability pre-test results were determined from the conclusion (post-test) of the first seven-week training block while post-test results were measured at the start (pre-test) of a second seven-week training block. Results: Four weeks of detraining significantly decreased the following variables: Vertical jump height by -5.26%, (p=0.037, d= 0.40), vertical jump peak velocity by -3.73% (p=0.001, d= 0.51), isometric strength by -5.5%, (p=0.012, d= 0.22), and relative isometric strength by -7.27% (p=0.003, d= 0.47). Furthermore, sensorimotor ability worsened, with a significant increase of 61.36% (p=0.004, d= 1.01), indicating that athletes took longer to stabilize from a dynamic landing task. Conclusions: This demonstrates that surfing, in the absence of resistance training, is not a sufficient training stimulus to maintain physical characteristics. Adolescent surfers with a relatively low training age should avoid cessation of resistance training and strive to maintain consistent resistance training in conjunction with surf training in order to avoid negative decrements in physical characteristics that are associated with surfing performance.

This study investigated the correlations with anthropometry, upper extremity strength, and surfboard paddling performance in recreational and competitive surfers. Twenty-nine recreational and competitive male surfers were assessed for height, mass, relative arm span, relative seated height, relative biacromial width, and skinfolds (Sum7). The upper extremity strength variables assessed were the relative 1RM pull up and 1RM dip. The surfboard paddling variables assessed were a 15 m sprint-paddling test and a 400 m endurance-paddling water-based test. Pearson correlation analysis and independent t-tests were used to compare differences between groups and determine the significant correlations between variables. Sum7 and relative arm span were correlated with speed in all paddling efforts meanwhile the sprint-paddling ability was correlated with the upper extremity strength. Significant differences between competitive and recreational surfers exist in relative arm span and endurance paddle performance. The strong relationships between the physical variables can be used by sports coaches and support staff to influence talent identification, training, and nutrition programs.

Purpose:To identify whether there are any significant differences in the lower-body muscle structure and countermovement-jump (CMJ) and squat-jump (SJ) performance between stronger and weaker surfing athletes.Methods:Twenty elite male surfers had their lower-body muscle structure assessed with ultrasonography and completed a series of lower-body strength and jump tests including isometric midthigh pull (IMTP), CMJ, and SJ. Athletes were separated into stronger (n = 10) and weaker (n = 10) groups based on IMTP performance.Results:Large significant differences were identified between the groups for vastus lateralis (VL) thickness (P = .02, ES = 1.22) and lateral gastrocnemius (LG) pennation angle (P = .01, ES = 1.20), and a large nonsignificant difference was identified in LG thickness (P = .08, ES = 0.89). Furthermore, significant differences were present between the groups for peak force, relative peak force, and jump height in the CMJ and SJ (P < .01−.05, ES = 0.90−1.47) and eccentric peak velocity, as well as vertical displacement of the center of mass during the CMJ (P < .01, ES = 1.40−1.41).Conclusion:Stronger surfing athletes in this study had greater VL and LG thickness and LG pennation angle. These muscle structures may explain their better performance in the CMJ and SJ. A unique finding in this study was that the stronger group appeared to better use their strength and muscle structure for braking as they had significantly higher eccentric peak velocity and vertical displacement during the CMJ. This enhanced eccentric phase may have resulted in a greater production and subsequent utilization of stored elastic strain energy that led to the significantly better CMJ performance in the stronger group.

Surfing is a dynamic sport and is performed in a highly unstable and changing environment, making balance a vital characteristic for surfers. It might be expected that repeated practice of particular movements in a specific stance, such as surfing, would lead to specific balance adaptations. This study investigated dynamic balance within surfers while also evaluating the influence of stance. Balance was assessed using the Biodex Stability System in an upright bipedal stance in 20 adult male surfers (age 24.10 ± 2.40 years, mass 74.95 ± 8.26 kg, height 177.11 ± 6.13 cm). Three 20-second balance trials were performed, and the degree and direction of tilt from horizontal were recorded. Results indicated that regular stance surfers spent a significantly ( p

The purpose of the present study was to determine whether any relationships were present between lower-body muscle structure and, lower-body strength, variables measured during a countermovement jump (CMJ) and squat jump (SJ), and eccentric leg stiffness, in adolescent athletes. Thirty junior male (n = 23) and female (n = 7) surfing athletes (14.8 ± 1.7 y; 1.63 ± 0.09 m; 54.8 ± 12.1 kg) undertook lower-body muscle structure assessment with ultrasonography and performed a; CMJ, SJ and an isometric mid-thigh pull (IMTP). In addition, eccentric leg stiffness was calculated from variables of the CMJ and IMTP. Moderate to very large relationships (r = 0.46-0.73) were identified between the thickness of the vastus lateralis (VL) and lateral gastrocnemius (LG) muscles, and VL pennation angle and; peak force (PF) in the CMJ, SJ and IMTP. Additionally, moderate to large relationships (r = 0.37-0.59) were found between eccentric leg stiffness and; VL and LG thickness, VL pennation angle, and LG fascicle length, with a large relationship (r = 0.59) also present with IMTP PF. These results suggest that greater thickness of the VL and LG were related to improved maximal dynamic and isometric strength, likely due to increased hypertrophy of the extensor muscles. Furthermore, this increased thickness was related to greater eccentric leg stiffness, as the associated enhanced lower-body strength likely allowed for greater neuromuscular activation, and hence less compliance, during a stretch-shortening cycle.

The purpose of this study was to determine whether any significant associations were present between lower-body strength and power, and the performance of turning and aerial manoeuvres in elite surfing athletes. Eighteen competitive male surfers performed a battery of physical tests (countermovement jump (CMJ), squat jump (SJ), and isometric mid-thigh pull (IMTP)) during a single session, in addition to having their performance of turning and aerial manoeuvres ranked from highest to lowest. Significant associations were identified between turning manoeuvre ranking and; peak force in the CMJ, SJ and IMTP (ϱ=−0.737, p

This study aimed to describe the impact forces, accelerations and ankle range of motion in five different landing tasks that are used in training and testing for competitive surfing athletes, to assist coaches in the prescription of landing task progression and monitoring training load. Eleven competitive surfing athletes aged 24 ± 7 years participated, and inertial motion sensors were fixed to the anterior aspect of the feet, mid-tibial shafts, sacrum and eighth thoracic vertebrae on these athletes. Three tasks were performed landing on force plates and two tasks in a modified gymnastics set-up used for land-based aerial training. Peak landing force, resultant peak acceleration and front and rear side ankle dorsiflexion ranges of motion during landing were determined. The peak acceleration was approximately 50% higher when performing aerial training using a mini-trampoline and landing on a soft-density foam board, compared to a similar landing off a 50 cm box. Furthermore, the ankle ranges of motion during the gymnastic type landings were significantly lower than the other landing types (P ≤ 0.05 and P ≤ 0.001), for front and rear sides, respectively. Conclusively, increased task complexity and specificity of the sport increased the tibial peak acceleration, indicating greater training load.

The purpose of this study was to develop and evaluate a drop-and-stick (DS) test method and to assess dynamic postural control in senior elite (SE), junior elite (JE), and junior development (JD) surfers. Nine SE, 22 JE, and 17 JD competitive surfers participated in a single testing session. The athletes completed 5 drop-and-stick trials barefoot from a predetermined box height (0.5 m). The lowest and highest time-to-stabilization (TTS) trials were discarded, and the average of the remaining trials was used for analysis. The SE group demonstrated excellent single-measures repeatability (ICC = .90) for TTS, whereas the JE and JD demonstrated good single-measures repeatability (ICC .82 and .88, respectively). In regard to relative peak landing force (rPLF), SE demonstrated poor single-measures reliability compared with JE and JD groups. Furthermore, TTS for the SE (0.69 ± 0.13 s) group was significantly (P = .04) lower than the JD (0.85 ± 0.25 s). There were no significant (P = .41) differences in the TTS between SE (0.69 ± 0.13 s) and JE (0.75 ± 0.16 s) groups or between the JE and JD groups (P = .09). rPLF for the SE (2.7 ± 0.4 body mass; BM) group was significantly lower than the JE (3.8 ± 1.3 BM) and JD (4.0 ± 1.1 BM), with no significant (P = .63) difference between the JE and JD groups. A possible benchmark approach for practitioners would be to use TTS and rPLF as a qualitative measure of dynamic postural control using a reference scale to discriminate among groups.

Purpose:To determine whether a previously validated performance-testing protocol for competitive surfers is able to differentiate between Australian elite junior surfers selected (S) to the national team and those not selected (NS).Methods:Thirty-two elite male competitive junior surfers were divided into 2 groups (S = 16, NS = 16). Their age, height, body mass, sum of 7 skinfolds, and lean-body-mass ratio (mean ± SD) were 16.17 ± 1.26 y, 173.40 ± 5.30 cm, 62.35 ± 7.40 kg, 41.74 ± 10.82 mm, 1.54 ± 0.35 for the S athletes and 16.13 ± 1.02 y, 170.56 ± 6.6 cm, 61.46 ± 10.10 kg, 49.25 ± 13.04 mm, 1.31 ± 0.30 for the NS athletes. Power (countermovement jump [CMJ]), strength (isometric midthigh pull), 15-m sprint paddling, and 400-m endurance paddling were measured.Results:There were significant (P ≤ .05) differences between the S and NS athletes for relative vertical-jump peak force (P = .01, d = 0.9); CMJ height (P = .01, d = 0.9); time to 5-, 10-, and 15-m sprint paddle; sprint paddle peak velocity (P = .03, d = 0.8; PV); time to 400 m (P = .04, d = 0.7); and endurance paddling velocity (P = .05, d = 0.7).Conclusions:All performance variables, particularly CMJ height; time to 5-, 10-, and 15-m sprint paddle; sprint paddle PV; time to 400 m; and endurance paddling velocity, can effectively discriminate between S and NS competitive surfers, and this may be important for athlete profiling and training-program design.

THE EXERCISE TECHNIQUE FOR THE SINGLE-LEG SQUAT AND THE ASSOCIATED PROGRESSIONS ARE OUTLINED IN THIS ARTICLE. FIVE PROGRESSIONS ARE DESCRIBED, WITH INFORMATION PROVIDED TO ASSIST THE STRENGTH AND CONDITIONING COACH TO SELECT THE BEST MODALITY FOR EACH INDIVIDUAL ATHLETE.

Watkins, CM, Barillas, SR, Wong, MA, Archer, DC, Dobbs, IJ, Lockie, RG, Coburn, JW, Tran, TT, and Brown, LE. Determination of vertical jump as a measure of neuromuscular readiness and fatigue. J Strength Cond Res 31(12): 3305-3310, 2017-Coaches closely monitor training loads and periodize sessions throughout the season to create optimal adaptations at the proper time. However, only monitoring training loads ignores the innate physiological stress each athlete feels individually. Vertical jump (VJ) is widely used as a measure of lower-body power, and has been used in postmatch studies to demonstrate fatigue levels. However, no pretraining monitoring by VJ performance has been previously studied. Therefore, the purpose of this study was to determine the sensitivity of VJ as a measure of readiness and fatigue on a daily sessional basis. Ten healthy resistance-trained males (mass = 91.60 ± 13.24 kg; height = 179.70 ± 9.23 cm; age = 25.40 ± 1.51 years) and 7 females (mass = 65.36 ± 12.29 kg; height = 162.36 ± 5.75 cm; age = 25.00 ± 2.71 years) volunteered to participate. Vertical jump and BRUNEL Mood Assessment (BAM) were measured 4 times: pre-workout 1, post-workout 1, pre-workout 2, and post-workout 2. Workout intensity was identical for both workouts, consisting of 4 sets of 5 repetitions for hang cleans, and 4 sets of 6 repetitions for push presses at 85% 1 repetition maximum (1RM), followed by 4 sets to failure of back squats (BSs), Romanian deadlift, and leg press at 80% 1RM. The major finding was that VJ height decrement (-8.05 ± 9.65 cm) at pre-workout 2 was correlated (r = 0.648) with BS volume decrement (-27.56 ± 24.56%) between workouts. This is important for coaches to proactively understand the current fatigue levels of their athletes and their readiness to resistance training.

Purpose:Appropriate and valid testing protocols for evaluating the physical performances of surfing athletes are not well refined. The purpose of this project was to develop, refine, and evaluate a testing protocol for use with elite surfers, including measures of anthropometry, strength and power, and endurance.Methods:After pilot testing and consultation with athletes, coaches, and sport scientists, a specific suite of tests was developed. Forty-four competitive junior surfers (16.2 ± 1.3 y, 166.3 ± 7.3 cm, 57.9 ± 8.5 kg) participated in this study involving a within-day repeated-measures analysis, using an elite junior group of 22 international competitors (EJG), to establish reliability of the measures. To reflect validity of the testing measures, a comparison of performance results was then undertaken between the EJG and an age-matched competitive junior group of 22 nationally competitive surfers (CJG).Results:Percent typical error of measurement (%TEM) for primary variables gained from the assessments ranged from 1.1% to 3.0%, with intraclass correlation coefficients ranging from .96 to .99. One-way analysis of variance revealed that the EJG had lower skinfolds (P = .005, d = 0.9) than the CJG, despite no difference in stature (P = .102) or body mass (P = .827). The EJG were faster in 15-m sprint-paddle velocity (P < .001, d = 1.3) and had higher lower-body isometric peak force (P = .04, d = 0.7) and superior endurance-paddling velocity (P = .008, d = 0.9).Conclusions:The relatively low %TEM of these tests in this population allows for high sensitivity to detect change. The results of this study suggest that competitively superior junior surfers are leaner and possess superior strength, paddling power, and paddling endurance.

Coyne, JOC, Tran, TT, Secomb, JL, Lundgren, LE, Farley, ORL, Newton, RU, and Sheppard, JM. Maximal strength training improves surfboard sprint and endurance paddling performance in competitive and recreational surfers. J Strength Cond Res 31(1): 244-253, 2017-Upper-body (UB) strength has very high correlations with faster surfboard paddling speeds. However, there is no research examining the effects of improving UB strength has on surfboard paddling ability. This study aimed to determine the influence that improvements in UB closed-kinetic chain maximal strength have on surfboard paddling in both competitive and recreational surfers. Seventeen competitive and recreational male surfers (29.7 ± 7.7 years, 177.4 ± 7.4 cm, 76.7 ± 9.9 kg) participated in a repeated-measures, parallel control study design. Anthropometry; 5-, 10-, and 15-m sprint; and 400-m endurance surfboard paddling tests along with pull-up and dip 1 repetition maximum strength tests were assessed pre- and postintervention. Subjects in the training group performed 5 weeks of maximal strength training in the pull-up and dip. Differences between the training and control groups were examined postintervention. The training group increased their speed over the 5-, 10-, and 15-m sprint, whereas the control group became slower (d = 0.71, 0.51, and 0.4, respectively). The training group also displayed faster endurance paddling performance compared with the control group (d = 0.72). Short-term exposure to maximal strength training elicits improvements in paddling performance measures. However, the magnitude of performance increases seems to be dependent on initial strength levels with differential responses between strong and weaker athletes. Although a longer maximal strength training period may have produced more significant paddling improvements in stronger subjects, practitioners are unlikely to have any more than 5 weeks in an uninterrupted block with competitive surfing athletes. This study reveals that a "threshold" level of maximal strength that if possessed, short-term maximal strength training may only provide little improvement in paddling performance.

Parsonage, JR, Secomb, JL, Tran, TT, Farley, ORL, Nimphius, S, Lundgren, L, and Sheppard, JM. Gender differences in physical performance characteristics of elite surfers. J Strength Cond Res 31(9): 2417-2422, 2017-The purpose of this study was to describe and compare the gender differences in physical performance characteristics of elite surfers. Twenty competitive female surfers (CFS) and 20 competitive male surfers (CMS) performed a battery of physical performance tests: squat jump (SJ), isometric midthigh pull (IMTP), 15-m sprint paddle, and 400-m endurance paddle during a single testing session. All performance measures were significantly different between CFS and CMS (p < 0.01). Specifically, CMS produced greater peak force production (28.5%) and jumped higher (27.7%) in the SJ and produced greater normalized peak force during the IMTP (18.9%) compared with CFS. For paddling performance, CMS were faster over 5, 10, and 15 m (12.4%, 9.7%, and 10.9%), possessed a higher peak paddling velocity (11.3%), and recorded faster paddle times over 400 m (11.8%). The results of this study suggest that CMS exhibit superior physical performance characteristics than CFS, in relation to both the lower and upper body. Strength and conditioning practitioners should therefore implement a structured and periodized program to facilitate strength qualities that underpin surfing performance for all participants, but as highlighted in the current investigation, female surfers may have a greater window for adaptation and therefore vast benefit of targeting their underdeveloped physical qualities.

There has been much investigation into the use of music as an ergogenic aid to facilitate physical performance. However, previous studies have primarily focused on predetermined music and aerobic exercise. The purpose of this study was to investigate the effects of self-selected music (SSM) vs. those of no music (NM) on the mood and performance of the athletes performing bench press and squat jump. Twenty resistance trained collegiate men completed 2 experimental conditions, one while listening to SSM and the other with NM. The subjects reported their profile of mood states (POMS) and rating of perceived exertion (RPE) before and after performing 3 sets to failure of the bench press at 75% 1 repetition maximum (1RM) and 3 reps of the squat jump at 30% 1RM. Statistical analyses revealed no differences in squat jump height or relative ground reaction force, but the takeoff velocity (SSM-2.06 ± 0.17 m·s(-1); NM-1.99 ± 0.18 m·s(-1)), rate of velocity development (SSM-5.92 ± 1.46 m·s(-2); NM-5.63 ± 1.70 m·s(-2)), and rate of force development (SSM-3175.61 ± 1792.37 N·s(-1); NM-2519.12 ± 1470.32 N·s(-1)) were greater with SSM, whereas RPE (SSM-5.71 ± 1.37; NM-6.36 ± 1.61) was greater with NM. Bench press reps to failure and RPE were not different between conditions. The POMS scores of vigor (SSM-20.15 ± 5.58; NM-17.45 ± 5.84), tension (SSM-8.40 ± 3.99; NM-6.07 ± 3.26), and fatigue (SSM-8.65 ± 4.49; NM-7.40 ± 4.38) were greater with SSM. This study demonstrated increased performance during an explosive exercise and an altered mood state when listening to SSM. Therefore, listening to SSM might be beneficial for acute power performance.

The purpose of this study was to develop and validate a regression equation to estimate peak power (PP) using a large sample of athletic youths and young adults. Anthropometric and vertical jump ground reaction forces were collected from 460 male volunteers (age: 12-24 years). Of these 460 volunteers, a stratified random sample of 45 subjects representing 3 different age groups (12-15 years [n = 15], 16-18 years [n = 15], and 19-24 years [n = 15]) was selected as a validation sample. Data from the remaining 415 subjects were used to develop a new equation ("Novel") to estimate PP using age, body mass (BM), and vertical jump height (VJH) via backward stepwise regression. Independently, age (r = 0.57), BM (r = 0.83), and VJ (r = 0.65) were significantly (p0.05) correlated with PP. However, age did not significantly (p = 0.53) contribute to the final prediction equation (Novel): PP (watts) = 63.6 × VJH (centimeters) + 42.7 × BM (kilograms) - 1,846.5 (r = 0.96; standard error of the estimate = 250.7 W). For each age group, there were no differences between actual PP (overall group mean ± SD: 3,244 ± 991 W) and PP estimated using Novel (3,253 ± 1,037 W). Conversely, other previously published equations produced PP estimates that were significantly different than actual PP. The large sample size used in this study (n = 415) likely explains the greater accuracy of the reported Novel equation compared with previously developed equations (n = 17-161). Although this Novel equation can accurately estimate PP values for a group of subjects, between-subject comparisons estimating PP using Novel or any other previously published equations should be interpreted with caution because of large intersubject error (±600 W) associated with predictions.

Vertical jumping ability is a critical skill for success in many sports. Previous studies have reported conflicting results on the effects of heavy-load, light-load, contrast, or plyometric training to improve vertical jump height. A novel jump training method, using assistance via elastic cords or an absolute weight, has received little attention. These studies, using an overspeed paradigm, support assistance as an effective training method compared with free or overload jump training. However, there is a lack of investigation and standardization related to the critical assisted jump training variables of frequency, intensity (assistance level), volume, and rest. Therefore, the purpose of this review was to provide an overview of assisted jump training, associated variables, and potential benefits to enhance vertical jump height.

Tran, TT, Brown, LE, Coburn, JW, Lynn, SK, Dabbs, NC, Schick, MK, Schick, EE, Khamoui, AV, Uribe, BP, and Noffal, GJ. Effects of different elastic cord assistance levels on vertical jump. J Strength Cond Res 25(12): 3472-3478, 2011-Currently, little research has been conducted using body weight reduction (BWR) as a means to enhance vertical jump. The purpose of this study was to determine the effects of different elastic cord assistance levels on vertical jump height (JH), takeoff velocity (TOV), relative ground reaction force (rGRF), relative impact force (RIF), and descent velocity (DV). Thirty recreationally trained college men and women (M = 15, W = 15) completed 3 testing sessions consisting of 5 conditions: 0, 10, 20, 30, and 40% BWR. In all BWR conditions, the subjects wore a full body harness while being attached to 2 elastic cords suspended from the ceiling and a linear velocity transducer. They then performed 3 maximal countermovement jumps with arm swing on a force plate. The results indicated no interaction of condition by sex for any variable; however, there was a significant (p0.05) main effect for condition for each variable. The JH significantly increased across all conditions (0%: 43.73 ± 1.62 cm, 40%: 64.77 ± 2.36 cm). The TOV at 30% (2.73 ± 0.34 m·s) was significantly greater than that at 0% (2.59 ± 0.39 m·s) and 10% (2.63 ± 0.34 m·s), whereas that at 40% (2.79 ± 0.43 m·s) was significantly greater than that at0, 10, and 20%. The rGRF at 30% (18.62 ± 4.35 N·kg) was significantly greater than that at0, 10, and 20%, whereas that at 40% (21.38 ± 5.21 N·kg) was significantly greater than in all conditions. The RIF at 20, 30, and 40% (40%: 61.60 ± 18.53 N·kg) was significantly greater than that at 0% (44.46 ± 9.12 N·kg). The DV at 20% (2.61 ± 0.31 m·s) was significantly greater than at 10%, whereas those at 30 and 40% (2.8 ± 0.41 m·s) were significantly greater than at 0, 10, and 20%. These results demonstrate that using different elastic cord levels to reduce body weight appears effective for increasing ascent and descent force and velocity variables. Future research should investigate greater BWR% and chronic training.

Introduction: Box jumps and depth jumps might elicit post activation potentiation, which can increase vertical jump performance. Aim: The purpose of this study was to compare the potentiating effects of a depth jump vs. a box jump warm-up on vertical jump performance. Methods: Eight collegiate and nine club female volleyball players participated on three testing days separated by 48 hours. Participants performed three pre-test countermovement vertical jumps with arm-swing then completed three experimental conditions in random order: control (no intervention), box jump (onto a box), and depth jump (stepping off a box with immediate maximal rebound). They then performed three post-test jumps. Results: Analysis revealed no significant (P < 0.05) interactions, but there was a main effect for time with all scores decreasing: vertical jump height (pre-34.31 ± 5.89cm; post-33.17 ± 5.86cm), relative ground reaction force (pre-24.18 ± 3.66N/kg; post-23.53 ± 3.66N/kg), and take-off velocity (pre-2.53 ± 0.29m/s; post-2.49 ± 0.30 m/s). Conclusions: It was concluded that using 10 depth or box jump warm-ups at the box height used in this study, with 10 minutes rest is not recommended to increase subsequent vertical jump performance in female collegiate volleyball players.

Starting stance plays an important role in influencing short-distance sprint speed and, therefore, the ability to reach a ball during sport play. The purpose of this study was to evaluate 4 different starting stances on sprint time. Twenty-six male and female collegiate volleyball players volunteered to participate in 1 testing session. Each subject performed 3 15-ft sprint trials at each of 4 different starting stances (P-parallel, FS-false step, S-staggered, and SFS-staggered false step) in random order. Analysis of variance revealed that there was no significant interaction of sex by stance, but there were main effects for sex (men were faster than women) and stance. The FS (1.18 ± 0.10 seconds), S (1.16 ± 0.07 seconds), and SFS (1.14 ± 0.06 seconds) stances were faster than the P (1.25 ± 0.09 seconds) stance, and the SFS stance was faster than the FS stance. This indicates that starting with a staggered stance (regardless of stepping back) produced the greatest sprinting velocity over the initial 15 feet. Although taking a staggered stance seems counterproductive, the resultant stretch-shortening cycle action and forward body lean likely increase force production of the push-off phase and place the total body center of mass ahead of the contacting foot, thereby, decreasing sprint time.

Whole-body vibration (WBV) may enhance human performance via augmented muscular strength and motor function if used before performance. Because warm-up is a crucial aspect of preparation for performance, it remains unknown if WBV may enhance bat speed. The purpose of this study was to investigate the effect of WBV warm-up on bat speed. Eleven National Collegiate Athletic Association division I and 11 recreationally trained female softball players volunteered to participate. Subjects randomly performed 3 different warm-up conditions consisting of WBV alone, dry swings alone (DS), and WBV with dry swings (WBVDS). Whole-body vibration was performed on a pivotal vibration platform at a frequency of 25 Hz and an amplitude of 13 mm for one 30-second bout. Thirty seconds after each warm-up condition, 5 maximal bat swings were recorded. There was no significant (p0.05) difference between groups by training status, and there was no significant (p0.05) difference between WBV (42.39 +/- 9.83 mph), DS (40.45 +/- 11.00 mph), or WBVDS (37.98 +/- 12.40 mph) conditions. These results indicate that WBV warm-up may be used in place of DS to achieve similar bat speeds. Future research should investigate different combinations of WBV warm-up using various frequencies, durations, amplitudes, and rest times.

The bench press exercise exists in multiple forms including the machine and free weight bench press. It is not clear though how each mode differs in its effect on muscle activation. The purpose of this study was to compare muscle activation of the anterior deltoid, medial deltoid, and pectoralis major during a Smith machine and free weight bench press at lower (70% 1 repetition maximum [1RM]) and higher (90% 1RM) intensities. Normalized electromyography amplitude values were used during the concentric phase of the bench press to compare muscle activity between a free weight and Smith machine bench press. Participants were classified as either experienced or inexperienced bench pressers. Two testing sessions were used, each of which entailed either all free weight or all Smith machine testing. In each testing session, each participant's 1RM was established followed by 2 repetitions at 70% of 1RM and 2 repetitions at 90% of 1RM. Results indicated greater activation of the medial deltoid on the free weight bench press than on the Smith machine bench press. Also, there was greater muscle activation at the 90% 1RM load than at the 70% 1RM load. The results of this study suggest that strength coaches should consider choosing the free weight bench press over the Smith machine bench press because of its potential for greater upper-body muscular development.

High-force activities have demonstrated postactivation potentiation (PAP) and may enhance performance in athletes; however, the efficacy of high-force activities to generate PAP in recreationally trained men remains unclear. The purpose of this study was to investigate the effect of high-force back squat volume on vertical jump (VJ) height, ground reaction force (GRF), impulse (IMP), and takeoff velocity (TOV) in recreationally trained men. Sixteen recreationally trained men (age 24.56 +/- 2.10 years, height 174.53 +/- 8.54 cm, mass 84.59 +/- 14.75 kg, and 1 repetition maximum [1RM] back squat 124.71 +/- 17.58 kg) with at least 1 year of back squat experience completed 5 testing sessions separated by a minimum of 72 hours' rest. On session 1, subjects completed VJ testing without a potentiating exercise intervention (control condition) in a test-retest fashion (3 VJs, 5 minutes seated rest, and 3 more VJs) and performed 1RM back squat testing. Subjects completed the subsequent 4 testing sessions in a test-retest fashion (3 VJs, experimental condition, 5 minutes seated rest, and 3 more VJs) in random order. The 4 experimental conditions required subjects to perform the back squat using a load of 85% 1RM with volumes of 1 x 2, 1 x 3, 1 x 4, or 1 x 5. Analysis of variance revealed no significant (p0.05) condition by time interactions for any dependent variable; however, there were significant (p0.05) main effects for time for GRF (pre 2,123.74 +/- 422.86 N,post 2,094.53 +/- 390.99 N) and IMP (pre 210.88 +/- 100.97 Nxs,post 204.63 +/- 106.14 Nxs) but not for VJ or TOV. These results suggest that 85% 1RM back squat volume assignments do not produce a VJ potentiation response in recreationally trained men.

Purpose:To develop and evaluate a multifactorial model based on landing performance to estimate injury risk for surfing athletes.Methods:Five measures were collected from 78 competitive surfing athletes and used to create a model to serve as a screening tool for landing tasks and potential injury risk. In the second part of the study, the model was evaluated using junior surfing athletes (n = 32) with a longitudinal follow-up of their injuries over 26 wk. Two models were compared based on the collected data, and magnitude-based inferences were applied to determine the likelihood of differences between injured and noninjured groups.Results:The study resulted in a model based on 5 measures—ankle-dorsiflexion range of motion, isometric midthigh-pull lower-body strength, time to stabilization during a drop-and-stick (DS) landing, relative peak force during a DS landing, and frontal-plane DS-landing video analysis—for male and female professional surfers and male and female junior surfers. Evaluation of the model showed that a scaled probability score was more likely to detect injuries in junior surfing athletes and reported a correlation of r = .66, P = .001, with a model of equal variable importance. The injured (n = 7) surfers had a lower probability score (0.18 ± 0.16) than the noninjured group (n = 25, 0.36 ± 0.15), with 98% likelihood, Cohen d = 1.04.Conclusions:The proposed model seems sensitive and easy to implement and interpret. Further research is recommended to show full validity for potential adaptations for other sports.

The purpose of this study was to determine whether any relationships were present between lower-body muscle structure and strength and power qualities. Fifteen elite male surfing athletes performed a battery of lower-body strength and power tests, including countermovement jump (CMJ), squat jump (SJ), isometric midthigh pull (IMTP), and had their lower-body muscle structure assessed with ultrasonography. In addition, lower-body muscle-tendon complex (MTC) stiffness and dynamic strength deficit (DSD) ratio were calculated from the CMJ and IMTP. Significant relationships of large to very large strength were observed between the vastus lateralis (VL) thickness of the left (LVL) and right (RVL) leg and peak force (PF) (r = 0.54-0.77, p < 0.01-0.04), peak velocity (PV) (r = 0.66-0.83, p < 0.01), and peak jump height (r = 0.62-0.80, p < 0.01) in the CMJ and SJ, as well as IMTP PF (r = 0.53-0.60, p = 0.02-0.04). Furthermore, large relationships were found between left lateral gastrocnemius (LG) pennation angle and SJ and IMTP PF (r = 0.53, p = 0.04, and r = 0.70, p < 0.01, respectively) and between LG and IMTP relative PF (r = 0.63, p = 0.01). Additionally, large relationships were identified between lower-body MTC stiffness and DSD ratio (r = 0.68, p < 0.01), right (LG) pennation angle (r = 0.51, p = 0.05), CMJ PF (r = 0.60, p = 0.02), and jump height (r = 0.53, p = 0.04). These results indicate that greater VL thickness and increased LG pennation angle are related to improved performance in the CMJ, SJ, and IMTP. Furthermore, these results suggest that lower-body MTC stiffness explains a large amount of variance in determining an athlete's ability to rapidly apply force during a dynamic movement.

Although lower-body strength is correlated with sprint performance, whether increases in lower-body strength transfer positively to sprint performance remain unclear. This meta-analysis determined whether increases in lower-body strength (measured with the free-weight back squat exercise) transfer positively to sprint performance, and identified the effects of various subject characteristics and resistance-training variables on the magnitude of sprint improvement. A computerized search was conducted in ADONIS, ERIC, SPORTDiscus, EBSCOhost, Google Scholar, MEDLINE and PubMed databases, and references of original studies and reviews were searched for further relevant studies. The analysis comprised 510 subjects and 85 effect sizes (ESs), nested with 26 experimental and 11 control groups and 15 studies. There is a transfer between increases in lower-body strength and sprint performance as indicated by a very large significant correlation (r = −0.77; p = 0.0001) between squat strength ES and sprint ES. Additionally, the magnitude of sprint improvement is affected by the level of practice (p = 0.03) and body mass (r = 0.35; p = 0.011) of the subject, the frequency of resistance-training sessions per week (r = 0.50; p = 0.001) and the rest interval between sets of resistance-training exercises (r = −0.47; p ≤ 0.001). Conversely, the magnitude of sprint improvement is not affected by the athlete’s age (p = 0.86) and height (p = 0.08), the resistance-training methods used through the training intervention, (p = 0.06), average load intensity [% of 1 repetition maximum (RM)] used during the resistance-training sessions (p = 0.34), training program duration (p = 0.16), number of exercises per session (p = 0.16), number of sets per exercise (p = 0.06) and number of repetitions per set (p = 0.48). Increases in lower-body strength transfer positively to sprint performance. The magnitude of sprint improvement is affected by numerous subject characteristics and resistance-training variables, but the large difference in number of ESs available should be taken into consideration. Overall, the reported improvement in sprint performance (sprint ES = −0.87, mean sprint improvement = 3.11 %) resulting from resistance training is of practical relevance for coaches and athletes in sport activities requiring high levels of speed.

Whole-body vibration (WBV) may potentiate vertical jump (VJ) performance via augmented muscular strength and motor function. The purpose of this study was to evaluate the effect of different rest intervals after WBV on VJ performance. Thirty recreationally trained subjects (15 men and 15 women) volunteered to participate in 4 testing visits separated by 24 hours. Visit 1 acted as a familiarization visit where subjects were introduced to the VJ and WBV protocols. Visits 2-4 contained 2 randomized conditions per visit with a 10-minute rest period between conditions. The WBV was administered on a pivotal platform with a frequency of 30 Hz and an amplitude of 6.5 mm in 4 bouts of 30 seconds for a total of 2 minutes with 30 seconds of rest between bouts. During WBV, subjects performed a quarter squat every 5 seconds, simulating a countermovement jump (CMJ). Whole-body vibration was followed by 3 CMJs with 5 different rest intervals: immediate, 30 seconds, 1 minute, 2 minutes, or 4 minutes. For a control condition, subjects performed squats with no WBV. There were no significant (p > 0.05) differences in peak velocity or relative ground reaction force after WBV rest intervals. However, results of VJ height revealed that maximum values, regardless of rest interval (56.93 ± 13.98 cm), were significantly (p < 0.05) greater than the control condition (54.44 ± 13.74 cm). Therefore, subjects' VJ height potentiated at different times after WBV suggesting strong individual differences in optimal rest interval. Coaches may use WBV to enhance acute VJ performance but should first identify each individual's optimal rest time to maximize the potentiating effects.

Development of core muscle strength and power to improve sport performance has been a controversial issue yielding mixed results. The purpose of this study was to investigate the relationship between two core field tests emphasizing power and measures of sport performance. Participants were twenty healthy, recreationally active males (age 23.40±1.88 yrs, height 174.63±5.81 cm, mass 76.08±7.67 kg). Participants were tested on four performance variables (40-yd sprint, shuttle run [5-10-5], vertical jump, and 1RM back squat) and two core field tests (front abdominal power throw [FAPT] and side abdominal power throw [SAPT]). Results demonstrated significant moderate correlations between the FAPT and 1RM back squat (r=.652) and relative back squat (r=.509). No other significant correlations were found. Results indicate that although the FAPT and SAPT tests are easy to perform in the field, most, but not all, performance measures were unrelated to core power. In order to properly assess the core and its role in human performance, it is necessary to evaluate sport-specific muscle actions and movements., Razvijanje mišićne jakosti i snage trupa kako bi se unaprijedila sportska izvedba i uspješnost jest kontroverzan znanstveni i stručni problem istraživanje kojega daje miješane rezultate. Cilj je ovoga istraživanja bilo utvrđivanje povezanosti između dva terenska testa za procjenu snage trupa i pokazatelja sportske uspješnosti. Uzorak ispitanika činilo je 20 zdravih, rekreativno aktivnih muškaraca (dob 23,40±1,88 godina, tjelesna visina 174,63±5,81 cm, tjelesna masa 76,08±7,67 kg). Sportska uspješnost ispitanika procijenjena je četirima testovima (sprint na 40 jarda, shuttle run: 5-10-5 jarda, vertikalni skok i maksimalni stražnji čučanj), a snaga njihova trupa (core) procijenjena je dvama terenskim testovima (eksplozivno bacanje medicinke prema naprijed – FAPT, i eksplozivno bacanje medicinke strance – SAPT). Rezultati analiza su pokazali značajne umjerene korelacije između FAPT i maksimalnoga stražnjega čučnja (r=,652) i relativnoga stražnjega čučnja (r=,509). Nisu utvrđene značajne korelacije između ostalih testova. Rezultati pokazuju da, iako je terenske testove FAPT i SAPT vrlo lako provoditi, većina, ali ne i sve varijable koje procjenjuju sportsku uspješnost nisu u korelaciji sa snagom trupa procijenjenom navedenim testovima. Da bi se adekvatno procijenila snaga trupa i njena uloga u sportskoj izvedbi i uspješnosti, potrebno je vrednovati sportu svojstvene mišićne akcije i kretnje.

Post-activation potentiation (PAP) has been shown to improve acute power performance. Depth jumps might elicit PAP resulting in improved vertical jump. The purpose of this study was to compare different volumes of depth jumps with rebound as a warm-up for vertical jumping. Seventeen collegiate women soccer players (age: 18.94±.74 yrs, height: 169.35±5.25 cm, mass: 66.07±6.42 kg) volunteered to participate in five testing sessions separated by at least 48 hours. Each subject warmed up on the cycle ergometer, then performed three pre-test countermovement jumps followed by 0, 3, 6, 9, or 12 depth jumps with rebound in random order. Box height was set at the level of the lateral femoral condyle for each subject. Subjects then rested for ten minutes followed by three post-test countermovement jumps. Dependent variables were Vertec vertical jump height (VJ) and relative ground reaction force (rGRF) measured by a force plate. ANOVA revealed no significant interactions but there was a main effect for time for VJ with pre-test (41.02±4.50 cm) being greater than post-test (40.42±4.30 cm). There were no main effects for rGRF (pre- 24.07±2.48 N/kg; post- 23.73±2.60 N/kg). These results suggest that the volume, box height and/or rest time used in this study were insufficient to elicit PAP and not only failed to increase vertical jump performance but resulted in a decrease. Therefore, it is suggested that collegiate women soccer players do not use depth jumps at knee height with these volumes and rest times as a warm-up in an effort to increase vertical jump performance., Dokazano je da postaktivacijska potencijacija (PAP) poboljšava akutnu eksplozivnu izvedbu. Dubinski skokovi mogu izazvati PAP koja može rezultirati poboljšanjem izvedbe vertikalnih skokova. Cilj je ovoga istraživanja bio usporediti učinke izvedbe različitih volumena dubinskih skokova s odrazom koji su se koristili kao sadržaj zagrijavanja za vertikalno skakanje. Sedamnaest sveučilišnih nogometašica (dobi 18,94±0,74 godina, tjelesne visine: 169,35±5,25 cm, tjelesne mase: 66,07±6,42 kg) dobrovoljno je sudjelovalo u istraživanju koje je uključivalo 5 testiranja s najkraćim razdobljem odmora između različitih volumena od 48 sati. Svaka ispitanica zagrijala se na bicikl ergometru, izvela tri skoka s pripremom prije provedbe testiranja te nakon toga 0, 3, 6, 9 ili 12 dubinskih skokova s odrazom nasumičnim redoslijedom. Visina sanduka s kojega se izvodio saskok bio je podešen na visinu lateralnoga femoralnoga kondila za svaku ispitanicu. Ispitanice su se nakon izvedbe dubinskih skokova odmorile 10 minuta te su nakon odmora ponovno izvodile tri skoka s pripremom. Zavisne varijable bile su visina vertikalnoga skoka (VJ) i relativna sila reakcije podloge (rGRF) izmjerena pomoću tenziometrijske platforme. Analizom varijance nije utvrđena statistički značajna razlika pri izvedbi različitih volumena dubinskih skokova, ali je utvrđena statistički značajna razlika u prosječnoj visini skoka pri čemu je rezultat u inicijalnom testiranju (41,02±4,50 cm) bio veći od rezultata zabilježenoga u finalnom testiranju (40,42±4,30 cm). Nije utvrđena značajna razlika u relativnoj sili reakcije podloge (pre-24,07±2,48 N/kg; post-23,73±2,60 N/kg). Dobiveni rezultati sugeriraju da volumen predopterećenja, visina sanduka i/ili vrijeme oporavka koje se koristilo u ovom istraživanju nije bilo dovoljno da bi se izazvala PAP te zbog toga ne samo da nije zabilježeno povećanje visine skoka, već je navedeni protokol predopterećenja rezultirao smanjenjem visine vertikalnoga skoka. Zbog toga se predlaže da sveučilišne nogometašice za zagrijavanje ne koriste dubinske skokove s odrazom u visini svojih koljena u ovom volumenu i vremenu oporavka kao vježbu predopterećenja za povećanje izvedbe vertikalnih skokova.

Previous research has investigated the force-time curve characteristics of isometric and dynamic muscle actions; however, few studies have addressed their relationship to dynamic exercise velocity-time variables. The purpose of this study was to investigate relationships between velocity-time characteristics (high pull and vertical jump peak velocity and rate of velocity development [HPPV, HPRVD, VJPV, VJRVD]), force-time characteristics (isometric peak force [IsoPF], body mass adjusted isometric peak force [IsoPF/BM], isometric rate of force development at different millisecond windows [IsoRFD50-250], dynamic peak force [HPPF], body mass adjusted dynamic peak force [HPPF/BM]), and vertical jump height (VJHeight). Nineteen recreationally trained men (age 23.89 ± 2.92 yr; height 176.32 ± 7.06 cm; mass 78.76 ± 16.50 kg) completed 2 testing sessions. The first session consisted of 3 isometric mid-thigh pulls on a force plate with each repetition held for 3 seconds. On the second testing session, subjects completed 3 dynamic mid-thigh high pulls with 30% IsoPF followed by 3 vertical jumps on a force plate. The HPRVD correlated with IsoRFD50 (r = 0.52) and IsoRFD100 (r = 0.49). The HPPV correlated with IsoPF/BM (r = -0.60), IsoRFD50 (r = 0.56), and IsoRFD100 (r = 0.56). The VJHeight correlated with IsoPF/BM (r = 0.61), whereas VJPV correlated with IsoPF/BM (r = 0.62). These correlations suggest that explosive isometric force production within 50 to 100 milliseconds may influence the ability to accelerate an implement or body and attain high velocity, albeit in a moderate fashion. In addition, body mass adjusted strength may positively influence vertical jump parameters.