bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Differences Between Adolescents and Adults During Two Landing Phases of a Drop Jump Task
Authors: Moir Gavin L. , Munford Shawn N. , Snyder Brandon W. , Davis Shala E. 
Published: August 2020

Abstract
Moir, GL, Munford, SN, Snyder, BW, and Davis, SE. Mechanical differences between adolescents and adults during two landing phases of a drop jump task. J Strength Cond Res 36(4): 1090–1098, 2022—The mechanical differences between the first and second landing phases of a drop jump (DJ) task performed by adolescent and adult male players were investigated. Eleven adolescent basketball players (age: 16.5 ± 0.7 years) and 11 resistance-trained adults (age: 22.3 ± 1.9 years) performed DJs from a height of 0.40 m. Force plates and a 3-dimensional motion analysis system were used to determine mechanical variables, including landing velocity, normalized vertical stiffness, normalized peak impact force, and work as well as mechanical characteristics of the hip, knee, and ankle joints during the absorption phase of each landing. The adolescents produced greater peak impact forces (mean difference [

Diff] = 42 N·kg0.67; effect size [ES] = 1.15) and vertical stiffness (

Diff = 126 N·kg0.67·m−1; ES = 1.28) during shorter absorption phases (

Diff = 0.09 seconds; ES = 2.67) compared with the adults, despite their lower landing velocities (

Diff = 0.21 m·s−1; ES = 1.37). Furthermore, the adolescents generated greater peak extensor joint moments at the lower-body joints compared with the adults (

Diff = 2.3 N·m·kg0.67; ES = 1.17), but they did not effectively modulate the energy absorbed by the joint moments in response to the changing demands of the landing tasks. The assessment of the biomechanical characteristics of the 2 landing phases associated with a DJ task revealed that adolescent male basketball players adopt neuromuscular strategies that may increase the risk of incurring musculoskeletal injuries compared with resistance-trained adults.
Ergogenic Effects of 8 Days of Sceletium Tortuosum Supplementation on Mood, Visual Tracking, and Reaction in Recreationally Trained Men and Women
Authors: Hoffman Jay R. , Markus Irit , Dubnov-Raz Gal , Gepner Yftach 
Published: August 2020

Abstract
Hoffman, JR, Marcus, I, Dubnov-Raz, G, and Gepner, Y. Ergogenic effects of 8 days of Sceletium tortuosum supplementation on mood, visual tracking, and reaction in recreationally trained men and women. J Strength Cond Res 34(9): 2476–2481, 2020—Sceletium tortuosum (ST) is a South African plant that has been reported to promote a sense of well-being in healthy individuals and used in treating people with anxiety, stress, or depression. These studies have been conducted in middle-aged and older adults, but no investigations have been performed in a healthy, young adult population. Thus, the purpose of this study was to examine the effect of 8 days of ST extract (25-mg) supplementation on changes in reactive agility, visual tracking, and mood. Sixty recreationally trained men (n = 48) and women (n = 12), between 20 and 35 years, were randomly assigned to 1 of 2 groups: ST or placebo (PL). Subjects were tested on 2 occasions: before supplementation and 2-hours after supplementation on day 8. Subjects completed a subjective questionnaire to assess alertness and energy using a visual analog scale (VAS). In addition, subjects completed the Profile of Mood States questionnaire and performed reactive agility and visual tracking assessments. Significant improvements were noted for ST in complex reactive performance that required subjects to respond to repeated visual stimuli with a cognitive load compared with PL. However, no significant changes were noted between the groups in either VAS or total mood score. In addition, no differences were observed in simple reaction assessments. The results of this study demonstrate an ergogenic benefit in complex reactive tasks that include a cognitive load. However, in this subject population studied, no benefits in mood were observed.
Countermovement Jump Standards in Rugby League: What is a “Good” Performance?
Authors: McMahon John J. , Lake Jason P. , Dos'Santos Thomas , Jones Paul A. , Thomasson Michael L. , Comfort Paul 
Published: August 2020

Abstract
McMahon, JJ, Lake, JP, Dos'Santos, T, Jones, PA, Thomasson, ML, and Comfort, P. Countermovement jump standards in rugby league: what is a “good” performance? J Strength Cond Res 36(6): 1691–1698, 2022—The countermovement jump (CMJ) is considered an important test in rugby league, and the force platform is the recommended tool for assessing CMJ performance in this cohort. Because of inconsistent methods applied across previous studies, there is currently a lack of understanding of what constitutes a “good” CMJ performance, with respect to the typical CMJ metrics that are reported for rugby league players. The purpose of this study was, therefore, to produce a scale of reference values for the jump height (JH), reactive strength index modified (RSImod), and mean (PPmean) and peak (PPpeak) propulsion power (relative to body mass) for top-level senior rugby league players competing in the global “forward” and “back” positional groups. One hundred four players (55 forwards and 49 backs) from the top 2 tiers of English rugby league performed 3 CMJs on a force platform at the beginning of pre-season training. The JH, RSImod, PPmean, and PPpeak were calculated using criterion methods, and a scale of norm-referenced values (percentiles) was produced for each positional group. The backs outperformed the forwards for each CMJ metric reported, thus supporting the production of position-specific norm-referenced values. When each positional group was separated into quartile subgroups, the respective JH, RSImod, PPmean, and PPpeak values were mostly largely and significantly different both within and between positions. The presented scale of reference values can, therefore, be used to determine the performance standards of rugby league forwards and backs with respect to the most commonly reported CMJ-derived variables for this cohort.
Effect of Divergent Solar Radiation Exposure With Outdoor Versus Indoor Training in the Heat: Implications for Performance
Authors: O'Connor Fergus K. , Doering Thomas M. , Minett Geoffrey M. , Reaburn Peter R. , Bartlett Jonathan D. , Coffey Vernon G. 
Published: August 2020

Abstract
O'Connor, FK, Doering, TM, Minett, GM, Reaburn, PR, Bartlett, JD and Coffey, VG. Effect of divergent solar radiation exposure with outdoor versus indoor training in the heat: implications for performance. J Strength Cond Res 36(6): 1622–1628, 2022—The aim of this study was to determine physiological and perceptual responses and performance outcomes when completing high-intensity exercise in outdoor and indoor hot environments with contrasting solar radiation exposure. Seven cyclists and 9 Australian Football League (AFL) players undertook cycling trials in hot conditions (≥30 °C) outdoors and indoors. Cyclists completed 5 × 4 minutes intervals (∼80% peak power output [PPO]) with 2 minutes recovery (∼40% PPO) before a 20-km self-paced ride. Australian Football League players completed a standardized 20 minutes warm-up (∼65% mean 4-minute power output) then 5 × 2 minutes maximal effort intervals. Heart rate (HR), PO, ratings of perceived exertion (RPE), thermal comfort (TC), and thermal sensation (TS) were recorded. Core (Tc) and skin temperature (Tsk) were monitored in cyclists alone. In both studies, ambient temperature, relative humidity, and solar radiation were monitored outdoors and matched for ambient temperature and relative humidity indoors, generating different wet bulb globe temperature (WBGT) for cyclists, but the similar WBGT for AFL players through higher relative humidity indoors. The statistical significance was set at p ≤ 0.05. Cyclists' HR (p = 0.05), Tc (p = 0.03), and Tsk (p = 0.03) were higher outdoors with variable effects for increased RPE, TS, and TC (d = 0.2–1.3). Power output during intervals was not different between trials, but there were small-moderate improvements in cyclists' PO and 20-km time indoors (d = 0.3–0.6). There was a small effect (d = 0.2) for AFL players' mean PO to increase outdoors for interval 4 alone (p = 0.04); however, overall there were small-moderate effects for lower RPE and TS indoors (d = 0.2–0.5). Indoor training in hot conditions without solar radiation may promote modest reductions in physiological strain and improve performance capacity in well-trained athletes.
Anaerobic Threshold in Stand-up Paddle: Comparison Between Direct and Alternative Methods
Authors: Balikian Pedro , Marinho Alisson H. , Gomes de Araujo Gustavo , Prado Eduardo S. , Mendes Eduardo V. , Ryan Geraldes Amândio A. 
Published: August 2020

Abstract
Balikian, P, Gomes de Araujo, G, Prado, ES, Ryan Geraldes, AA, Marinho de Lima, AH, and Mendes, EV. Anaerobic threshold in stand-up paddle: comparison between direct and alternative methods. J Strength Cond Res 36(7): 1896–1900, 2022—The purpose of this study was to test the validity of alternative protocols, mean velocity during 30 minutes of continuous effort (V30min) and critical velocity (CV), to estimate the anaerobic threshold in stand-up paddle (SUP). Eight athletes performed: 3 maximal efforts at 400-, 500-, and 800-m distances to determine CV values, using the distance-time relationship; 3 efforts at 85, 90, and 100% of maximal 500-m effort to determine the velocity related to 3.5 mmol·L−1 of lactate, assumed as the onset of blood lactate accumulation (OBLA) and; a 30-minute continuous effort to determine the V30min. All evaluations were separated by 48 hours, with the athletes using their own boards and paddles in the water. No differences were observed between the OBLA (2.35 ± 0.13 m·s−1) and alternative methods (CV: 2.42 ± 0.20 m·s−1; p = 0.10 and V30min: 2.32 ± 0.13 m·s−1; p = 0.63). Although strong correlations were observed between the OBLA and alternative methods (CV: r = 0.84 and V30min: r = 0.94), the limits of agreement were higher in CV (±0.23 m·s−1) than V30min (±0.08 m·s−1). These results demonstrate that both the CV and V30min are valid to estimate the OBLA. In view of the specificity of SUP and the high levels of agreement, the use of the V30min is recommended to prescribe training intensities.
Muscle Activity, Leg Stiffness, and Kinematics During Unresisted and Resisted Sprinting Conditions
Authors: Zabaloy Santiago , Carlos-Vivas Jorge , Freitas Tomás T. , Pareja-Blanco Fernando , Loturco Irineu , Comyns Thomas , Gálvez-González Javier , Alcaraz Pedro E. 
Published: August 2020

Abstract
Zabaloy, S, Carlos-Vivas, J, Freitas, TT, Pareja-Blanco, F, Loturco, I, Comyns, T, Gálvez-González, J, and Alcaraz, PE. Muscle activity, leg stiffness and kinematics during unresisted and resisted sprinting conditions. J Strength Cond Res 36(7): 1839–1846, 2022—This study aimed to compare muscle activity, leg stiffness, and kinematics (contact and flight time [FT], stride length and frequency, and trunk angle [TA]) of unloaded sprinting to resisted sprint (RST) using different loads. Twelve male rugby players (age: 23.5 ± 5.1 years; height: 1.79 ± 0.04 m; body mass 82.5 ± 13.1 kg) performed 30-m sprints using different loading conditions (0, 10, 30 and 50% of velocity loss—Vloss—from the maximum velocity reached under unloaded condition). Muscle activity from 4 muscles (biceps femoris long head, rectus femoris [RF], gluteus medius and gastrocnemius), leg stiffness (Kleg), and kinematics were measured during the acceleration and maximum velocity (Vmax) phases of each sprint. Heavier loads led to significantly lower biceps femoris long head activation and higher rectus femoris activity (p < 0.01–0.05). Significant reductions in Kleg were observed as loading increased (p < 0.001–0.05). Kinematic variables showed substantial changes with higher loads during the acceleration and Vmax phase. In conclusion, the heavier the sled load, the higher the disruptions in muscle activity, Kleg, and kinematics. When coaches and practitioners intend to conduct resisted sprint training sessions without provoking great disruptions in sprint technique, very-heavy sled loads (greater than 30% Vloss) should be avoided. However, heavy sled loads may allow athletes to keep specific positions of the early acceleration phase for longer time intervals (i.e., first 2–3 strides during unresisted sprints).
Isometric Mid-thigh Pull Kinetics: Sex Differences and Response to Whole-Body Vibration
Authors: Merrigan Justin J. , Dabbs Nicole C. , Jones Margaret T. 
Published: August 2020

Abstract
Merrigan, JJ, Dabbs, NC, and Jones, MT. Isometric mid-thigh pull kinetics: Sex differences and response to whole-body vibration. J Strength Cond Res 34(9): 2407–2411, 2020—The purpose was to investigate whether whole-body vibration's (WBV's) effect on force-time characteristics is dependent on time and sex. Subjects (men, n = 18; women, n = 18) performed a static quarter squat with WBV (frequency: 30 Hz; amplitude: 2–4 mm) and without for 5 × 30 seconds repetitions (1:1, WBV:rest). Next, they performed 2 sets of 3 repetitions of the isometric mid-thigh pull (IMTP) with 3 minutes of intraset rest and 5 minutes of interset rest. Peak force (PF) and rate of force development (RFD) from 0 to 50, 0 to 150, and 0 to 250 milliseconds (RFD50, RFD150, and RFD250) were analyzed (p < 0.05). A significant effect of condition existed for PF (p = 0.019) and RFD from 0 to 250 seconds (p = 0.031). In women, RFD was moderately affected immediately post-WBV (p = 0.070; d = 0.49). Yet in men, the effect of WBV on RFD existed 15 minutes after exposure (p = 0.017; d = 0.36). In absolute terms men produced more PF than women (1,008.6 ± 289.7 N; p < 0.001). All RFD bands were greater in men than those of women (RFD50, 5,519.3 ± 2,927.2 N·s−1; RFD150, 3,361.4 ± 1,385.3 N·s−1; RFD250, 2,505.7 ± 867.1 N·s−1; p < 0.05). However, relative to fat-free mass, PF in men (40.1 ± 7.2 N·kg−1) was not different from women (37.7 ± 6.4 N·kg−1; p = 0.284). The same was true for RFD150 (21.1 ± 24.1 N·kg−1·s−1; p = 0.084) and RFD250 (10.9 ± 14.1 N·kg−1·s−1; p = 0.128). Yet, RFD50 remained greater in men (139.1 ± 33.6 N·kg−1·s−1) than that of women (86.8 ± 34.5 N·kg−1·s−1; p = 0.034). Current WBV protocols resulted in trivial to moderate effects on IMTP forces, which may be dependent on sex and time. Finally, it is recommended that women complete movements with the intent to move weight quickly to improve early RFD.
Effectiveness of a 2-Week Strength Training Learning Intervention on Self-selected Weight-Training Intensity
Authors: Glass Stephen C. , Ahmad Sabrina , Gabler Taylor 
Published: August 2020

Abstract
Glass, SC, Ahmad, S, and Gabler, T. Effectiveness of a 2-week strength training learning intervention on self-selected weight-training intensity. J Strength Cond Res 34(9): 2443–2448, 2020—The purpose of this study was to determine the effectiveness of an imposed (IM) vs. self-selected (SS) 2-week strength training intervention on SS resistance training intensity. Subjects 18–40 years (SS n = 10 and IM n = 10) were provided resistance training orientation (chest press, leg press, triceps extension, bicep curl, and shoulder press). On 6 different training days, subjects completed 2 sets on each machine while blinded to the load. The SS group SS loads without any intensity or effort feedback. Load, repetitions, and ratings of perceived exertion (RPE) were recorded. The IM group was encouraged to lift to fatigue, and if they exceeded 12 repetitions, subsequent load was increased (goal-attain 70% one repetition maximum [1RM]). After training, SS and IM SS loads and repetitions for all lifts, plus 3 novel lifts (pec fly, leg extension, and shoulder raise). One repetition maximum was assessed last. Comparisons between groups were made using 2-way analysis of variance. There were significant main effects for % 1RM for the condition and day (day 1 IM = 57.2 ± 12.0%, SS = 47.2 ± 13.7% and day 6 IM = 74.7 ± 10.8%, SS = 66.2 ± 13.4%). There were significant effects across days for reps (day 1 IM = 10.8 ± 4.8, SS = 12.3 ± 4.0 and day 6 IM = 9.3 ± 3.6, SS = 10.0 ± 3.0) and RPE (day 1 = 15.4 ± 2.0 and day 6 = 16.5 ± 1.9). For both SS and IM post-training SS loads exceeded 60% 1RM. However, among the novel lifts, only the pec fly was greater than 60% 1RM (pec fly 63.0 ± 11.0%, leg extension 39.8 ± 12.5%, and shoulder raise 53.1 ± 12.8%). Two weeks of supervised resistance training resulted in both IM and SS self-selecting loads greater than 60% 1RM. There were no differences after 2-weeks of training between IM load and SS load groups.
Performance Differences Between the Arched and Flat Bench Press in Beginner and Experienced Paralympic Powerlifters
Authors: Ribeiro Neto Frederico , Dorneles Jefferson R. , Luna Rafael M. , Spina Murilo A. , Gonçalves Carlos W. , Gomes Costa Rodrigo R. 
Published: August 2020

Abstract
Neto, FR, Dorneles, JR, Luna, RM, Spina, MA, Gonçalves, CW, and Gomes Costa, RR. Performance differences between the arched and flat bench press in beginner and experienced Paralympic powerlifters. J Strength Cond Res 36(7): 1936–1943, 2022—The present study aimed to verify the differences of the total load, trajectory of the barbell in the sagittal plane, and mean velocity of the barbell between the arched and flat techniques of the bench press in beginner (BG) and experienced (EG) Paralympic powerlifters. Twenty beginners (age: 34.4 years; experience: 3.3 months) and 23 experienced (age: 35.5 years; experience: 9.8 months) Paralympic powerlifters were selected from a Rehabilitation Hospital Network and a Paralympic sports center. Subjects were assessed in the one-maximum repetition test of the bench press exercise using the flat and arched bench press techniques (48–72-hour interval between sessions). Maximum strength, trajectory of the barbell in the sagittal plane, and mean velocity of the barbell were measured to compare the techniques and the groups. The total load corrected with the Haleczko formula was significantly higher in EG compared with BG (∆ = 21.1%; effect sizes [ES] = 0.39, p ≤ 0.05). There were no significant differences for all analyzed outcomes comparing the arched and flat techniques. During the eccentric phase of the bench press, all assessed differences ranged from −16.6 to 23.1% and presented ES of trivial to moderate. On the concentric phase, the assessed differences ranged from −20.7 to 13.9% and presented ES of trivial to moderate. The total load, trajectory of the barbell in the sagittal plane, and mean velocity of the barbell were not significantly different between the arched and flat techniques for experienced and beginner powerlifting athletes during both the eccentric and concentric phase of the movement. However, further analyses are essential to determine the best technique for athletes.
Performing Soccer-Specific Training With Blood Flow Restriction Enhances Physical Capacities in Youth Soccer Players
Authors: Hosseini Kakhak Seyed A. , Kianigul Mojtaba , Haghighi Amir-Hossein , Nooghabi Mehdi Jabbari , Scott Brendan R. 
Published: August 2020

Abstract
Hosseini Kakhak, SA, Kianigul, M, Haghighi, AH, Nooghabi, MJ, and Scott, BR. Performing soccer-specific training with blood flow restriction enhances physical capacities in youth soccer players. J Strength Cond Res 36(7): 1972–1977, 2022—This study investigated the effect of soccer training with blood flow restriction (BFR) on physical performance in youth athletes. Nineteen semiprofessional soccer players were randomly assigned to either normal soccer training (ST; n = 9) or soccer training with BFR (STBFR; n = 10). Both groups performed identical activities during a 6-week preseason training phase, either with or without lower limb BFR. Training included soccer-specific drills, small-sided games, plyometrics, and continuous running. Before and after the intervention, players were assessed for leg extension strength and endurance, countermovement jump performance, 40-yd sprint time, change-of-direction (COD) ability, aerobic endurance, and soccer-specific endurance (while dribbling a ball). Significantly larger improvements were observed in the STBFR compared with the ST group for tests of muscular endurance (74.8 ± 34.1% vs. 4.0 ± 14.6%), COD (8.1 ± 3.7% vs. 2.8 ± 4.7%), and aerobic (54.1 ± 19.6% vs. 24.7 ± 27.2%) and soccer-specific endurance (58.4 ± 19.6% vs. 22.7 ± 10.2%). Main effects for time were observed for maximal strength, jumping, and sprinting performance (p < 0.001) but with no group and time interaction. These findings demonstrate that team sport training with BFR can enhance physical qualities that are related to performance in youth soccer players. This application of BFR may improve the adaptive responses of muscles, without having to dedicate additional training time to muscular qualities.
Load Centralization Does Not Affect the Kinetic and Kinematic Output of Countermovement Jumps
Authors: Tredrea Matthew S. J. , Middleton Kane J. , Bourne Matthew N. , Carey David L. , Scanlan Aaron T. , Dascombe Ben J. 
Published: August 2020

Abstract
Tredrea, MSJ, Middleton, KJ, Bourne, MN, Carey, DL, Scanlan, AT, and Dascombe, BJ. Load centralization does not affect the kinetic and kinematic output of countermovement jumps. J Strength Cond Res 36(4): 1084–1089, 2022—This study aimed to compare the kinetics, kinematics, and performance of countermovement jumps (CMJs) when completed with 2 different loading conditions (centralized or peripheral) across increasing loads. Seventeen subjects (12 men and 5 women) randomly completed 2 series of CMJs with increasing loads separated by a 30-minute rest period between conditions. Subjects were loaded with either a weighted vest (centralized) or straight barbell (peripheral). A randomized, counterbalanced crossover design was used with incremental loads of 10, 20, 30, 40, and 50% of body mass added to the vest or barbell. Measures of peak force, acceleration, velocity, and power were calculated across each subphase of the CMJs. No significant differences were observed in kinetic or kinematic variables between loading conditions. Within each condition there were significant reductions (p < 0.05) in peak concentric velocity and acceleration, as well as significant increases (p < 0.05) in peak force when the external load increased. Furthermore, braking and propulsive phase duration significantly increased (p < 0.05) and jump height significantly decreased (p < 0.05) as the external load increased. Countermovement jump performance was similar in both central and peripheral loading, whereas increasing load significantly affected jump height, force, velocity, and acceleration variables irrespective of load position. The training stimulus from an external load placed centrally or peripherally is similar regardless of where it is positioned; however, from a practical perspective, a weighted vest may provide a more mobile and safer alternative than a barbell.