The Influence of Maturity Status on Drop Jump Kinetics in Male Youth.

ABSTRACT: Kumar, NTA, Radnor, JM, Oliver, JL, Lloyd, RS, CSCSD, Pedley, JS, Wong, MA, and Dobbs, IJ. The influence of maturity status on drop jump kinetics in male youth. J Strength Cond Res 38(1): 38-46, 2024-The aim of this study was to examine the effects of maturity status on drop jump (DJ) kinetics in young male athletes (categorized as early-pre-peak height velocity [PHV] [<-2.51 years], late-pre-PHV [-1.99 to -1.00 years], circa-PHV [-0.50 to 0.50 years], and post-PHV [>1.00 years]). All athletes performed a DJ from a 30-cm box onto force plates with performance variables (jump height, ground contact time, and reactive strength index) and absolute and relative kinetic variables during the braking and propulsive phases assessed. Subjects were categorized into GOOD (no impact-peak and spring-like), MODERATE (impact-peak and spring-like), or POOR (impact-peak and not spring-like) stretch-shortening cycle (SSC) function. The post-PHV group exhibited significantly greater values for most absolute kinetic variables compared with early-pre-PHV, late-pre-PHV, and circa-PHV (p < 0.05). The differences observed between consecutive maturity groups were similar in magnitude for most absolute variables (Cohen's d = 0.53-1.70). Post-PHV male athletes outperform their less mature counterparts during a DJ, and this may be attributed to the growth and maturity-related structural and motor control strategy changes that occur in children. Stretch-shortening cycle function in boys seems to improve with maturity status reflected by a greater number of post-PHV participants displaying GOOD SSC function (65.8%) and a greater number of early-pre-PHV participants displaying POOR SSC function (54.4%). However, a number of mature boys displayed POOR SSC function (17.8%), suggesting that the development of SSC function is not exclusively related to maturation.

Effects of Training Frequency During a 6-Month Neuromuscular Training Intervention on Movement Competency, Strength, and Power in Male Youth.

BACKGROUND: Youth populations benefit from neuromuscular training; however, the extent to which training frequency, baseline fitness, and maturity status moderate the response to long-term neuromuscular training in male youth remains unclear. HYPOTHESIS: Twice-weekly training (G2x) would induce larger improvements in movement competency and strength and power kinetics compared with once-weekly training (G1x). Maturity status and baseline fitness would also moderate the training response in strength and power kinetics. STUDY DESIGN: Nonrandomized, repeated-measures design. LEVEL OF EVIDENCE: Level 3. METHODS: Ninety-five male athletes of varying maturity status (pre- or post-peak height velocity) were divided into G2x, G1x, or control (CON) groups. Training groups received G2x or G1x for 28 weeks. Back squat assessment (BSA) movement competency and isometric mid-thigh pull (IMTP), squat jump (SJ), and countermovement jump (CMJ) kinetics were measured pre- and postintervention. RESULTS: The G2x achieved significantly greater adaptations in BSA total score, IMTP allometrically scaled peak force (PFallo), IMTP peak rate-of-force development (PRFD), SJ PFallo and PRFD compared with G1x and CON (P < 0.05; d = 0.3-0.9). Baseline fitness, training frequency and maturity status were significant predictors of IMTP PFallo (R2 = 27.5%) and PRFD (R2 = 42.9%), while a combination of training frequency and baseline fitness explained a small amount of variance in SJ PFallo (R2 = 12.2%) and SJ PRFD (R2 = 6.5%). There were no significant predictors of CMJ kinetics. CONCLUSION: G2x achieved significantly larger improvements in movement competency, isometric strength and concentric jump variables compared with G1x, with the training response greater in those youth with lower baseline fitness and more advanced maturity status. CLINICAL RELEVANCE: Exposure to neuromuscular training twice-weekly elicits a greater response than G1x in young male athletes. Practitioners should take maturity status, training frequency, and baseline fitness levels of young male athletes into account when interpreting testing data, as these variables appear to moderate training responsiveness.

Effects of a 4-Week Neuromuscular Training Program on Movement Competency During the Back-Squat Assessment in Pre- and Post-Peak Height Velocity Male Athletes.

ABSTRACT: Dobbs, IJ, Oliver, JL, Wong, MA, Moore, IS, Myer, GD, and Lloyd, RS. Effects of a 4-week neuromuscular training program on movement competency during the back-squat assessment in pre- and post-peak height velocity male athletes. J Strength Cond Res 35(10): 2698-2705, 2021-The back-squat assessment (BSA) is a novel movement screen to detect functional deficits; however, its sensitivity to detect meaningful changes in movement competency after exposure to short-term neuromuscular training remains unclear. Twenty-six pre- and 22 post-peak height velocity (PHV) males were divided into experimental (EXP) and control groups (CON) and performed the BSA before and after a twice weekly, 4-week neuromuscular training intervention. Intra-rater reliability was determined by rating both EXP group's baseline BSA on 3 separate sessions. Intraclass correlation coefficient (ICC) revealed very strong agreement for BSA total score in pre-PHV (ICC ≥ 0.81) and post-PHV (ICC ≥ 0.97) groups across all sessions, but systematic bias was evident in the pre-PHV group for sessions 1-2. Analysis of kappa values for BSA individual criteria showed greater variability for pre-PHV (K ≥ 0.31) than post-PHV (K ≥ 0.62) across sessions. At baseline, there were no differences in total score between the EXP and CON cohorts (p > 0.05). There were significant within-group improvements in total score for the EXP pre-PHV (5.0 to 3.0, effect size [ES] = 0.68) and post-PHV (2.0 to 1.0, ES = 0.82) cohorts, with no changes in total score for either CON groups (p > 0.05). Hip position was the criterion with the greatest improvement for both the EXP pre-PHV (12.0 to 7.0) and post-PHV (7.0 to 0.0) groups. The BSA seems to be a reliable screening tool for measuring movement competency in youth male athletes and was sensitive to adaptations in movement competency after neuromuscular training.

Movement competency and measures of isometric and dynamic strength and power in boys of different maturity status.

An understanding of how movement competency, strength, and power interact with natural growth and maturation is required in order to determine meaningful changes with developing athletes. Isometric and dynamic testing in youth athletes provides insight into the natural development of the force-velocity (F-V) spectrum. Two-hundred and six young male athletes, aged 9-17 years of age, were grouped according to stage of maturation based on their maturity offset which was determined as number of years from peak height velocity (PHV). All participants performed the back-squat assessment (BSA), isometric mid-thigh pull (IMTP), countermovement jump (CMJ), and squat jump (SJ) tests. Absolute and scaled force-time variables were collected from the IMTP, CMJ, and SJ. No significant differences were observed between maturational groups for squat movement competency (P > .05). One-way ANOVA with Bonferroni post-hoc analysis revealed that increasing maturity led to significant, moderate to large increases in allometrically scaled peak force (PFallo ) for all tests (P < .05). Multiple stepwise linear regression models revealed IMTP PFallo significantly predicted 34.8% and 41.3% of variance in SJ and CMJ jump height, respectively (P < .05). Natural growth and maturation induces positive adaptations to movement competency as well as isometric and dynamic strength and power. Trends from the IMTP, SJ, and CMJ tests indicate the largest differences in strength, and power may occur around the adolescent growth spurt despite the large variation in rates of change within the circa-PHV group.

Effects of a 12-Week Training Program on Isometric and Dynamic Force-Time Characteristics in Pre- and Post-Peak Height Velocity Male Athletes.

Dobbs, IJ, Oliver, JL, Wong, MA, Moore, IS, and Lloyd, RS. Effects of a 12-week training program on isometric and dynamic force-time characteristics in pre- and post-peak height velocity male athletes. J Strength Cond Res 34(3): 653-662, 2020-Literature shows that training children and adolescents can enhance strength and power irrespective of their stage of development; however, the development of the kinetic variables that underpin strength and power performance are typically unreported in youth training studies. Twenty-four pre- and 14 post-peak height velocity (PHV) male athletes were divided into maturity-specific experimental (EXP) and control groups (CON), with the EXP groups completing a twice-weekly, 12-week training program. Force-time characteristics during the isometric midthigh pull (IMTP), countermovement jump, and squat jump tests were quantified at both baseline and after the completion of the 12-week program. Alpha level was set at p < 0.05. No changes in total score for back-squat assessment were observed in any group (p > 0.05). Analysis of IMTP data revealed that only the post-PHV EXP group significantly increased absolute isometric peak force (PFabs) and peak rate of force development within the IMTP after training. Both EXP groups displayed significant increases in isometric PF at time epochs 0-90, 0-150, 0-200, and 0-250 ms. Data from the dynamic tests indicated that the pre-PHV EXP cohort improved concentric qualities as reflected by increased squat jump height and countermovement jump concentric power. There were no significant changes for any variables across all tests within either CON group (p > 0.05). Maturity-related differences in response to short-term training affects the kinetic variables associated with strength and power performance, but not movement competency in young male athletes.

No Effect of Assisted Hip Rotation on Bat Velocity.

Softball and baseball are games that require multiple skill sets such as throwing, hitting and fielding. Players spend a copious amount of time in batting practice in order to be successful hitters. Variables commonly associated with successful hitting include bat velocity and torso rotation. The concept of overspeed bodyweight assistance (BWA) has shown increases in vertical jump and sprint times, but not hip rotation and batting. The purpose of this study was to examine the effects of assisted hip rotation on bat velocity. Twenty-one male and female recreational softball and baseball players (15 males, age 23.8 ± 3.1yrs; height 177.67 ± 6.71cm; body mass 85.38 ± 14.83kg; 6 females, age 21.5 ± 2.1yrs; height 162.20 ± 9.82cm; body mass 60.28 ± 9.72kg) volunteered to participate. Four different BWA conditions (0%, 10%, 20%, and 30%) were randomly applied and their effects on bat velocity were analyzed. Subjects performed three maximal effort swings under each condition in a custom measurement device and average bat velocity (MPH) was used for analysis. A mixed factor ANOVA revealed no interaction (p=0.841) or main effect for condition, but there was a main effect for sex where males had greater bat velocity (43.82±4.40 - 0% BWA, 41.52±6.09 - 10% BWA, 42.59±7.24 - 20% BWA, 42.69±6.42 - 30% BWA) than females (32.57±5.33 - 0% BWA, 31.69±3.40 - 10% BWA, 32.43±5.06 - 20% BWA, 32.08±4.83 - 30% BWA) across all conditions Using the concept of overspeed training with assisted hip rotation up to 30% BWA did not result in an increase in bat velocity. Future research should examine elastic band angle and hip translation at set-up.

Effects of Starting Stance on Base Running Sprint Speed in Softball Players.

Speed is a crucial aspect in softball, and can be the difference between winning and losing. Base stealing is a method used to produce runs. There has been debate over which starting position is the most advantageous to maximize acceleration and speed to reach the next base the fastest. The purpose of this study was to examine the effect of different starting stances on acceleration and speed phases in collegiate softball players. Seventeen healthy NCAA Division I women's softball players (age = 19.9 ± 1.3yrs, height = 167.0 ± 5.4cm, mass = 74.8 ± 14.1kg) volunteered to participate. Three maximum 45 ft sprints, with one minute rest, were performed (with splits at 15, 30 and 45ft) for each of three starting stances (front foot on the base, back foot on the base, and cross over stance). A 1×3 repeated measures ANOVA for total time demonstrated that front foot on the base was significantly faster (2.51 ± 0.18s) than back foot on the base (2.70 ± 0.19s) and the cross over step (2.66 ± 0.23s). For all three splits, front foot on the base was also significantly faster (0.96 ± 0.07s, 0.81 ± 0.06s, and 0.73 ± 0.06s) than back foot on the base (1.10 ± 0.13s, 0.84 ± 0.05s, and 0.75 ± 0.43s) and cross over step (1.04 ± 0.09s, 0.84 ± 0.06s, and 0.75 ± 0.07s). The decrease in time for front foot on the base was probably the result of using the base to push against, like a sprinter's block, to produce greater horizontal force to accelerate faster and reach a greater top speed. Coaches should teach their softball athletes to stand with their front foot on the base when base running.

Validity and Reliability of Surface Electromyography Measurements from a Wearable Athlete Performance System.

The Athos ® wearable system integrates surface electromyography (sEMG ) electrodes into the construction of compression athletic apparel. The Athos system reduces the complexity and increases the portability of collecting EMG data and provides processed data to the end user. The objective of the study was to determine the reliability and validity of Athos as compared with a research grade sEMG system. Twelve healthy subjects performed 7 trials on separate days (1 baseline trial and 6 repeated trials). In each trial subjects wore the wearable sEMG system and had a research grade sEMG system's electrodes placed just distal on the same muscle, as close as possible to the wearable system's electrodes. The muscles tested were the vastus lateralis (VL), vastus medialis (VM), and biceps femoris (BF). All testing was done on an isokinetic dynamometer. Baseline testing involved performing isometric 1 repetition maximum tests for the knee extensors and flexors and three repetitions of concentric-concentric knee flexion and extension at MVC for each testing speed: 60, 180, and 300 deg/sec. Repeated trials 2-7 each comprised 9 sets where each set included three repetitions of concentric-concentric knee flexion-extension. Each repeated trial (2-7) comprised one set at each speed and percent MVC (50%, 75%, 100%) combination. The wearable system and research grade sEMG data were processed using the same methods and aligned in time. The amplitude metrics calculated from the sEMG for each repetition were the peak amplitude, sum of the linear envelope, and 95th percentile. Validity results comprise two main findings. First, there is not a significant effect of system (Athos or research grade system) on the repetition amplitude metrics (95%, peak, or sum). Second, the relationship between torque and sEMG is not significantly different between Athos and the research grade system. For reliability testing, the variation across trials and averaged across speeds was 0.8%, 7.3%, and 0.2% higher for Athos from BF, VL and VM, respectively. Also, using the standard deviation of the MVC normalized repetition amplitude, the research grade system showed 10.7% variability while Athos showed 12%. The wearable technology (Athos) provides sEMG measures that are consistent with controlled, research grade technologies and data collection procedures.

Repeated Plyometric Exercise Attenuates Blood Glucose in Healthy Adults.

Plyometric exercise is popular in commercial exercise programs aiming to maximize energy expenditure for weight loss. However, the effect of plyometric exercise on blood glucose is unknown. The purpose of this study was to investigate the effect of relatively high intensity plyometric exercise on blood glucose. Thirteen subjects (6 females age= 21.8 ± 1.0 yrs.; height= 163.7 ± 7.8 cm; mass= 60.8 ± 6.7 kg and 7 males age= 22.0 ± 2.6 yrs.; height= 182.3 ± 3.6 cm; mass= 87.4 ± 12.5 kg) volunteered to participate. Subjects completed two random conditions on two separate days, consisting of either five sets of 10 maximal effort countermovement squat jumps (SJ) with 50 seconds' rest between sets or quiet sitting (SIT) for the time equated to the SJ duration (~4min). Immediately after each condition, subjects drank 75g of anhydrous glucose (CHO) in 100ml of water. Blood glucose measurements were taken via finger prick pre and immediately post SJ or SIT, and 5, 15, 30, and 60 min post. A 2×6 (condition × time) ANOVA revealed a significant interaction where SJ blood glucose was lower at 15 (114.0 ± 14.6 mg/dl) and 30 (142.1 ± 22.5 mg/dl) min compared to SIT (15min 130.8 ± 14.0 mg/dl and 30min 159.3 ± 21.0 mg/dl). The current plyometric protocol attenuated CHO-induced blood glucose at 15 and 30 min. This may be due to increased physiological stress applied to the muscles, thus increasing muscular glucose uptake.

Determination of Vertical Jump as a Measure of Neuromuscular Readiness and Fatigue.

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.

Sled Towing Acutely Decreases Acceleration Sprint Time.

Wong, MA, Dobbs, IJ, Watkins, C, Barillas, SR, Lin, A, Archer, DC, Lockie, RG, Coburn, JW, and Brown, LE. Sled towing acutely decreases acceleration sprint time. J Strength Cond Res 31(11): 3046-3051, 2017-Sled towing is a common form of overload training in sports to develop muscular strength for sprinting. This type of training leads to acute and chronic outcomes. Acute training potentially leads to postactivation potentiation (PAP), which is when subsequent muscle performance is enhanced after a preload stimulus. The purpose of this study was to determine differences between rest intervals after sled towing on acute sprint speed. Twenty healthy recreationally trained men (age = 22.3 ± 2.4 years, height = 176.95 ± 5.46 cm, mass = 83.19 ± 11.31 kg) who were currently active in a field sport twice a week for the last 6 months volunteered to participate. A maximal 30-meter (m) baseline (BL) body mass (BM) sprint was performed (with splits at 5, 10, 20, and 30 m) followed by 5 visits where participants sprinted 30 m towing a sled at 30% BM then rested for 2, 4, 6, 8, or 12 minutes. They were instructed to stand still during rest times. After the rest interval, they performed a maximal 30-m post-test BM sprint. Analysis of variance (ANOVA) revealed that post sled tow BM sprint times (4.47 ± 0.21 seconds) were less than BL times (4.55 ± 0.18 seconds) on an individualized rest interval basis. A follow-up 2 × 4 ANOVA showed that this decrease occurred only in the acceleration phase over the first 5 m (BL = 1.13 ± 0.08 seconds vs. Best = 1.08 ± 0.08 seconds), which may be the result of PAP and the complex relationship between fatigue and potentiation relative to the intensity of the sled tow and the rest interval. Therefore, coaches should test their athletes on an individual basis to determine optimal rest time after a 30-m 30% BM sled tow to enhance acute sprint speed.

Acute Effects of Eccentric Overload on Concentric Front Squat Performance.

Munger, CN, Archer, DC, Leyva, WD, Wong, MA, Coburn, JW, Costa, PB, and Brown, LE. Acute effects of eccentric overload on concentric front squat performance. J Strength Cond Res 31(5): 1192-1197, 2017-Eccentric overload is used to enhance performance. The purpose of this study was to investigate the acute effects of eccentric overload on concentric front squat performance. Twenty resistance-trained men (age = 23.80 ± 1.82 years, height = 176.95 ± 5.21 cm, mass = 83.49 ± 10.43 kg, 1 repetition maximum [1RM] front squat = 131.02 ± 21.32 kg) volunteered. A dynamic warm-up and warm-up sets of front squat were performed. Eccentric hooks were added to the barbell. They descended for 3 seconds, until eccentric hooks released, and performed the concentric phase as fast as possible. There were 3 randomly ordered conditions with the concentric phase always at 90% 1RM and the eccentric phase at 105, 110, and 120% of 1RM. Two repetitions were performed for each condition. A repeated measures analysis of variance was used to determine differences. For peak velocity, there were main effects for time and condition (p < 0.05), where post (1.01 ± 0.10 m·s) was greater than pre (0.96 ± 0.11 m·s) and 120% (1.03 ± 1.11 m·s) was greater than 105% (0.99 ± 0.13 m·s). For peak power, there was a main effect for condition where 120% (2,225.00 ± 432.37 W) was greater than 105% (2,021.84 ± 563.53 W). For peak ground reaction force, there were main effects for time and condition, where post was greater than pre and 120% was greater than 105%. For the rate of force development, there was no interaction or main effects. Eccentric overload enhanced concentric velocity and power; therefore, it can be used by strength coaches and athletes during the power phase of a training program. It can also be used to prescribe supramaximal loads and could be a tool to supplement the clean exercise because the front squat is a precursor.

Influence of Rest Intervals After Assisted Sprinting on Bodyweight Sprint Times in Female Collegiate Soccer Players.

Nealer, AL, Dunnick, DD, Malyszek, KK, Wong, MA, Costa, PB, Coburn, JW, and Brown, LE. Influence of rest intervals after assisted sprinting on bodyweight sprint times in female collegiate soccer players. J Strength Cond Res 31(1): 88-94, 2017-Speed is a crucial element an athlete must possess to be successful. In soccer, the ability to accelerate faster than your opponent can result in being first to reach a ball on a breakaway or stopping a counter attack. A unique way to train explosive movements is to evoke postactivation potentiation (PAP) in the working muscles. Traditionally, an overload stimulus with a long rest period is used, but a model using an overspeed stimulus with shorter rest periods is less understood. Therefore, the purpose of this study was to determine the acute effects of varied rest intervals after assisted sprinting on bodyweight sprint time. Twenty-four female soccer players were split into 2 groups: recreational (n:11; age:20 ± 1.67 year; ht:162.30 ± 4.35 cm; mass:61.02 ± 8.78 kg) and collegiate athletes (n:13; age:19.76 ± 0.83 year; ht:166.85 ± 5.98 cm; mass:61.23 ± 3.77 kg). All participants attended 5 separate sessions, performed a dynamic warm up, then executed one 20 m sprint (with 5 m splits) at 30% bodyweight assistance (BWA). They then rested for 30 seconds, 1, 2, or 4 minutes in random order, followed by one bodyweight sprint with no BWA. Baseline sprint times were measured without BWA on the initial session of testing. Results revealed no difference in sprint time for the full 20 m distance in either group. However, sprint time was significantly decreased for the 0-5 m split only for the athletes after 1 minute (1.15 ± 0.06 second) and 2 minute (1.16 ± 0.06 second) rest compared with baseline (1.21 ± 0.04 second). Therefore, trained athletes should rest 1 or 2 minutes after 30% BWA supramaximal sprinting for increased bodyweight sprint speed.

Acute Effects of Static vs. Ballistic Stretching on Strength and Muscular Fatigue Between Ballet Dancers and Resistance-Trained Women.

Lima, CD, Brown, LE, Wong, MA, Leyva, WD, Pinto, RS, Cadore, EL, and Ruas, CV. Acute effects of static vs. ballistic stretching on strength and muscular fatigue between ballet dancers and resistance-trained women. J Strength Cond Res 30(11): 3220-3227, 2016-Stretching is used to increase joint range of motion, but the acute effects can decrease muscle strength. However, this may depend on the population or mode of stretching. The purpose of this study was to compare the acute effects of static vs. ballistic stretching on strength and muscular fatigue between ballet dancers and resistance-trained women. Fifteen resistance-trained women (age 23.8 ± 1.80 years, mass 67.47 ± 7.77 kg, height 168.30 ± 5.53 cm) and 12 ballet dancers (age 22.8 ± 3.04 years, mass 58.67 ± 5.65 kg, height 168.00 ± 7.69 cm) performed 5 days of testing. The first day was control (no stretching), whereas the other 4 days were static or ballistic stretching in a counterbalanced order. Range of motion, strength, and fatigue tests were also performed. Both groups demonstrated a significant decrease in hamstrings strength after static (102.71 ± 2.67 N·m) and ballistic stretching (99.49 ± 2.61 N·m) compared with control (113.059 ± 3.25 N·m), with no changes in quadriceps strength. For fatigue, only ballet dancers demonstrated a decrease from control (71.79 ± 4.88%) to ballistic (65.65 ± 8.19%), but no difference with static (65.01 ± 12.29%). These findings suggest that stretching decreases hamstrings strength similarly in ballet dancers and resistance-trained women, with no differences between modes of stretching. However, ballistic stretching only decreased muscular fatigue in ballet dancers, but not in resistance-trained women. Therefore, no stretching should be performed before strength performance. However, ballistic stretching may decrease acute muscular fatigue in ballet dancers.