International Sport Forum of the Strength & Conditioning Society (SCS) and the European Sport Nutrition Society (ESNS)

On behalf of the Strength & Conditioning Society (SCS) and the European Sport Nutrition Society (ESNS), we are pleased to present the abstracts of the 2019 International Sport Forum on Strength & Conditioning & Nutrition, which took place in Madrid, Spain from November 15th–16th 2019. The meeting provided evidence-based education to advance the science and practice on the fields of sport nutrition, training, rehabilitation and performance. It also disseminated cutting-edge sport nutrition and strength and conditioning research, promoted the translation of basic science into the field and fostered the future of the field by providing young practitioners and researchers with the opportunity to present their findings through oral and poster communications, the abstracts of which can be found in this Special Issue of Sports. Renowned international and national speakers provided comprehensive updates, workshops and insights into novel scientific topics covering various areas of sport nutrition and strength and conditioning science. We were fortunate to have a wide range of speakers and presenters from all areas—strength training, conditioning to prevent injuries and improve performance, nutrition and supplementation for fitness and high-performance sports. A data-flash and poster session allowed for the presentation of the latest results of current research. Most importantly, the meeting provided ample opportunities to bring people together to discuss practical questions related to training and nutrition and plan scientific projects. With cutting-edge research and best practice in mind, this joint conference was an important means to pursue the missions of the SCS and ESNS. Rather than being a single event, the forum in Madrid was the starting point for a series of regular meetings on Strength & Conditioning & Nutrition to be held worldwide, so make sure to visit the websites of the SCS and ESNS and follow us on social media to receive updates and connect with our members. We proudly look back on an exciting, inspiring and informative meeting in Madrid!


Abstract:
The most commonly performed warm-up is arguably a short bout of sub-maximal exercise, e.g.,~60-70% maximum oxygen uptake (VO 2max ). However, it has been proposed that the addition of brief, task-specific bursts of high-intensity exercise to this standard warm-up would provide further ergogenic benefits. This effect, known as post-activation potentiation (PAP), is thought to facilitate a greater force production capacity. The aim of this study was to analyze the performance and physiological effects of different warm-up protocols on endurance performance. Fifteen male cyclists (35 ± 9 years; VO 2max : 66.4 ± 6.8 mL·kg·min-1) participated on this randomized study. They performed a 20-min cycling time-trial preceded by either no warm-up, a standard-warmup (10 min at 60% VO 2max ) or a warm-up designed to elicit PAP (five minutes at 60% VO 2max followed by three 10-s all-out sprints interspersed with a 90-s rest). Performance (jump ability, power output (PO)), perceptual (rating of perceived exertion (RPE)) and physiological (VO2, muscle oxygenation (SmO2), heart rate variability (HRV), blood lactate and skin temperature) responses were measured. An enhanced jump ability (p < 0.001) was observed after standard-warmup (9.7 ± 4.7%) and PAP-warmup (12.9 ± 6.5%), but not with no-warmup (−1.9 ± 4.8%, p = 0.074). Both standard-warmup (−7.9 ± 14.2%, p = 0.027) and PAP-warmup (−20.3 ± 24.7%, p = 0.006)-but not no-warmup (−1.7 ± 10.5%, p = 0.366)-resulted in a decreased HRV. Participants started the trial (minutes 0-3) at a higher PO and VO2 with PAP-warmup compared to the other conditions (p < 0.05), but no differences were overall found for the mean PO, RPE, VO2 or SmO2 during the trial (all p > 0.05). Warming-up enhanced neuromuscular performance (i.e., jumping) and induced a shift towards sympathetic modulation. The inclusion of brief sprints resulted in a higher initial intensity during the subsequent time trial.
Keywords: performance; preconditioning; exercise Abstract: Lower-limb asymmetries in muscle function may increase the risk of falls among older women. However, no data are available in men. The purpose of this study was to clear whether this effect is sex-specific and to assess the relationship between muscle asymmetries and other measures of physical function. Participants (thirty-three well-functioning older volunteers) completed a force-velocity relationship test and a 1-RM test in the unilateral leg press exercise (Technogym, Italy) with a linear position transducer mounted (Chronojump, Spain) to assess maximum dynamic strength, maximum muscle power and movement velocity. Physical function was assessed by means of the SPPB. Lower-limb asymmetry (%) was calculated for both 1-RM and Pmax. No differences were found between 1-RM and Pmax asymmetry values. Furthermore, no sex-related differences were identified for 1-RM or Pmax asymmetry values. Finally, no associations were found between physical function and asymmetry outcomes. Both maximal muscle strength and power muscular asymmetries were similar in elderly men and women. Asymmetries in muscle function were not related to other measures of physical function in healthy older adults. Abstract: Unlike today-when most runners use modern shoes with cushioning and support-people in the past would run either barefoot or simple shoes. The aim of this study was to analyze the influence of footwear on running spatiotemporal parameters, foot-strike pattern and foot pronation velocity in amateur runners using the RunScribe™ foot pods. A total of 51 healthy subjects, 34 men and 17 women, (age: 27.84 ± 7.01 years; height: 172.88 ± 7.92 cm; body mass: 67.89 ± 10.9 kg; 10 km time: 47.85 ± 6.87 min) run at a self-selected comfortable velocity under the shod and unshod condition on a treadmill. Data were recorded using the RunScribe™ sensor (triaxial accelerometer and gyroscope) over three min for both conditions and mean values analyzed. Maximum pronation velocity, contact time, flight time, step frequency, stride length and foot-strike pattern (1) were compared between measures by using ANOVA and Cramer's V analyses. Significant differences were found between shod and unshod conditions for all the variables analyzed-CT (p < 0.001), FT (p < 0.001), SF (p < 0.001), SL (p < 0.001) MPV (p < 0.001) and FSP (v < 0.2). Running spatiotemporal parameters and running kinematics, in terms of MPV and FSP, differ between footwear conditions within the same subjects.

Keywords
Keywords: barefoot; kinetics; pronation velocity; sensors; wearables Funding: This research received no external funding.

Acknowledgments:
The authors would like to thank all participants.

Influence of Oral Contraceptives and the Menstrual Cycle on Endurance Performance in Competitive Handball Players
Christoph Triska 1,2, *, Patricia Haider 1 , Claudia Vidotto 3 , Barbara Wessner 1 and Astrid Reif 1 1 Centre for Sport Science and University Sports, University of Vienna, Vienna, Austria 2 Austrian Institute of Sport Medicine, Vienna, Austria 3 Labor Vidotto, Vienna, Austria * Correspondence: christoph.triska@univie.ac.at; Tel.: +43-1-4277-48867 Abstract: Recently, assessing the effects of different phases of the menstrual cycle on strength and endurance performance has gained interest in scientific works. Changes in the female hormones during the menstrual cycle are suggested to influence endurance as well as strength and speed abilities. When using a monophasic combination pill as an oral contraceptive two different phases can be described: (1) high estradiol and gestagen concentration during 21 days of taking the pill and (2) low estradiol and gestagen concentration during 7 days of absence of the pill. Therefore, the aim of this study was to assess differences in endurance performance, i.e., . VO 2 and heart rate (HR) at 2.78 m·s −1 ; absolute und relative . VO 2max ; HR max ; maximal blood lactate concentration (La); maximal aerobic speed (MAS) between phase 1-represented by high concentrations in estradiol and gestagen-and phase 2-represented by low concentrations in estradiol and gestagen. Eight competitive female handball players (age: 24.6 ± 3.6 yrs; body mass: 66.0 ± 4.0 kg; body stature: 1.68 ± 0.05 m) volunteered to participate in this study. Participants were reported to the laboratory on two occasions. One test was conducted on Day 2 or Day 3 of the menstrual cycle (phase 2) and the other on day 16 or 17 of the menstrual cycle (phase 1). The order of the test was randomized. Before each test 7 mL venous blood samples were taken in order to analyze for hormonal concentration and the body mass of the participants was measured. A graded exercise test on a motorized treadmill (Saturn, h/p/cosmos, Traunstein, Germany) starting at 1.67 m·s −1 with an increment of 0.28 m·s −1 every 1 min was used to assess endurance performance. Throughout the test respiratory gases were measured breath-by-breath using a mobile gas analyzer (MetaMax3B-R3, Cortex Biophysik GmbH, Leipzig, Germany). Immediately and three min after terminating the treadmill test 20 µL blood samples were taken from the earlobe in order to assess [La max ] and subsequently analyzed (Biosen S_Line, Barleben, Germany). HR was measured using a heart rate sensor (H7, Polar Electro Oy, Kempele, Finland) connected to the gas analyzer. Differences between phases were assessed using a paired-samples t-test and effect sizes were evaluated using the Cohen's d. Significance was accepted as p < 0.05. No significant differences were found for . VO 2 and HR at 2.78 m·s −1 , absolute and relative . VO 2max , HR max , [La max ], MAS and body mass (p = 0.178 − 1.000), and the effect sizes were of a small order (d = 0.03 − 0.28). Significant differences, however, were found for gestagen and estradiol concentrations between the phases (p < 0.05). The findings of this study demonstrate statistically insignificant differences in endurance exercise performance within the menstrual cycle in handball players taking a monophasic combination pill. Therefore, the monthly bleeding has no detrimental nor beneficial effects in handball players.

Keywords: team-sports; contraception; female athletes
Funding: This research received no external funding.

Effects of Caffeine Ingestion on Physical Performance in Elite Women Handball Players: A Randomized, Controlled Study
reps/ 10 s rest each 2 reps/one min rest inter-sets at 30-50% F0; and HIIT: combining habitual and

Comparison of the Load-Velocity Relationship between Men and Women in Bench Press Exercise
Pedro J. Cornejo-Daza 1, *, Simon Walker 2 , Keijo Häkkinen 2 and Fernando Pareja-Blanco 1 1 Physical Performance & Sports Research Center, Faculty of Sport Sciences, Universidad Pablo de Olavide, Sevilla, España 2 Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland * Correspondence: pjcordaz@gmail.com Abstract: The objective was to examine the differences between load-velocity relationships in men and women in bench press (BP) exercise, comparing three velocity variables: mean velocity (MV), mean propulsive velocity (MPV) and peak velocity ( Abstract: In the field of physical exercise and fitness, the term of "muscular toning" is used to refer to obtaining "stiffness in the skeletal fibers" following exercise and/or load in strength training (resistance, hypertrophy and maximum strength). This term has no scientific basis in the literature, but is still used by coaches, doctors, athletes, instructors and gym users as synonymous with neuromuscular adaptations. (1) Background: This aim of this study was to define the term "muscle toning" due to the lack of scientific evidence in the field of exercise and sports sciences. (2) Methods: This literature review includes 30 scientific articles indexed in databases such as Pubmed, NCBI and academic google, using search terms or keywords such as: muscle toning, muscle strength, muscle strength, hypertrophy and strength resistance; (3) Results: No scientific articles were found in the databases consulted that defined the term "muscle toning". Within the selection process, physiological adaptations are reaffirmed as in an increase in nerve impulses from the central nervous system to the peripheral one, thus achieving an increase in the sarcoplasmic content and myofibrillar size, which are generated by the training of the patient's strength, but that differ from the term used in question; (4) Conclusions: There is no objective definition of the concept "muscle toning". Adaptations of neuromuscular order are established, but do not define the use of the term within the field of physical exercise and fitness, but that claim to argue fibrillar growth, strength gain and sometimes an increase in size are defined as hypertrophy.
Keywords: muscular toning; skeletal fibers; resistance; hypertrophy; maximum strength Funding: This research received no external funding. strength and body mass index of celiac women before and after an intervention of three months of dislocations and area 95% (A95). An experimental device with two coupled load cells was developed to measure force variability (FV) and maximal force (MF). In this experiment, to determine FV, the volunteers remained seated with parallel feet and performed MF attempts or maintained isometric plantar flexion force for 20 s, at relative intensities of 5% and 10% of the MF. Asymmetry indices were calculated from the dominant leg variability (DLV) and the non-dominant leg variability (NDLV) with the following equation: AFV = [NDLV-DLV/0.5*(NDLV + DLV)] × 100. Results: Pearson's correlation test did not indicate significant associations between the asymmetries on both intensities (5% and 10% of the MF) and the center of pressure displacement variables Conclusion: Postural control of older adults is not associated with the symmetry of the force variability and with the symmetry of maximal force of the PFM.

Load-Velocity Relationship of Full-Squat Exercise in U-15 Soccer Players
P. García-González * and J. A. Velasco University Pablo de Olavide, Sevilla, Spain; joseavel2@hotmail.com * Correspondence: pgargon5@alu.upo.es Abstract: Maximum repetition (1RM) has been used as the main control parameter in resistance training for years. However, recent studies have proposed the movement velocity as a practical and useful alternative. The purpose of this study was to analyze the relationship between the mean propulsive velocity (VMP), and the relative load expressed as a percentage of the maximum repetition (%1RM) in U-15 soccer players. Nine young male soccer players performed a progressive test until reaching their maximum repetition in the full squat exercise. Bar velocity was measured by a linear velocity transducer. A strong relationship between VMP and %1RM was found (R 2 = 0.96). Prediction equations to estimate load from velocity were obtained. Velocity values for the 1RM are considerably higher than in bench press exercise and slightly higher than in pull-up exercise. VMP values obtained for each %1RM are lower than other values obtained in previous studies which focused on the full squat exercise. Because of these subjects are slower, it is recommended to use the equations provided in this study for the full squat exercise training in U-15 soccer players.
Keywords: resistance training; muscle strength; athletic performance; velocity-based training; bar velocity Funding: This research received no external funding.

Paul McKeown *, Phil Price and Daniel Cleather
Faculty of Sport, Health & Science, St Mary's University, Waldegrave Road, Strawberry Hill, Twickenham, TW1 4SX, UK; phil.price@stmarys.ac.uk (P.P.); daniel.cleather@stmarys.ac.uk (D.C.) * Correspondence: pmckeown@coachingperformance.co.uk Abstract: Individuals who are unsatisfied in terms of their basic psychological needs of autonomy, competence and relatedness are considered more likely to suffer from unwanted stress. Unwanted stress has been observed to increase the likelihood of sporting injury among adolescents. To further examine these concepts, 121 rugby union players aged between 14-18 years were asked to complete a basic psychological needs satisfaction in general survey 2 days prior to playing competitive rugby matches. A Mann-Whitney U test showed that players who received injuries during their games were significantly more likely to have recorded lower relatedness survey scores than the uninjured players (µinj = 41.56 ± 5.61 and µuninj = 46.24 ± 5.47, respectively, U = 237, p < 0.01). To better understand what particular relatedness factors were affecting this population, a deviant case analysis was conducted with a range of high and low relatedness scoring participants. The interviewees highlighted how perceived levels of team cohesion and social support could affect a player's feelings of relatedness and their likelihood of incurring match injuries. These findings could help justify the use of BPN surveys within schools and rugby clubs as an inexpensive method to identify individuals who report low levels of relatedness satisfaction and intervene to help avoid the associated elevated risk of injury. Abstract: Sled towing has been shown to be an effective tool to enhance the physical qualities in youth soccer players. The aim of this study was to evaluate the impact of a six-week sled towing intervention on muscular strength, speed and power in elite youth soccer players of differing maturity status' (pre-, circa-, post-PHV). Method: A total of 73 male elite youth soccer players aged 12-18 years (pre-PHV n = 25; circa-PHV n = 24; post-PHV n = 24) were recruited for this study from professional soccer academy. Data collection consisted of anthropometric and physical qualities which were collected at the start of the intervention (T1) and at the end of the six-week intervention (T2). Physical qualities were assessed using 10-and 30-m sprint speed, countermovement jump for lower limb power and isometric mid-thigh pull for lower limb strength. The training intervention consisted of six weeks of resisted sled towing (FH Pro Mini Speed Sledge Team Series), two sessions per week with a total of 12 sessions during the competitive season. Each session consisted of 10 sprints over 20-m distance. To model pairwise differences between pre and post-scores within each maturation group, Bayesian regression models were fitted using a Student-t distribution (Haff, & Aas, 2008). Probability values of a change being greater than 0 (p > 0 or <0) were provided with a standardized effect size calculated from the posterior estimates and again the uncertainty illustrated with lower and upper 95% HDIs. Results: There were no significant changes in pre-to post-performance measures following the six-week intervention for any of the maturation groups. It appears that loadings of 10-30% BM do not induce performance changes in elite youth soccer players over a range of performance measures.

Evolution of the Velocity Loss and the Glycolytic Involvement throughout Two
intervention period. Weight and height were measured to calculate BMI. A body composition analyzer was used to estimate fat mass (FM) and total lean mass (TLM) both in kg. Relative skeletal muscle mass (kg) (RMM) described by Janssen et al. and fat mass percentage (FM%) were calculated. A t-Student's test was performed to evaluate differences between groups before the intervention and ANOVA for repeated measures in order to compare differences before and after the six months within and between groups. No differences between groups nor group by time interaction were found before the intervention in any variable (all p > 0.05). Only increases in TLM and RMM and a reduction of the FM% were observed within the TRAIN group (TLM 45.6 ± 8.0 kg vs. 46.3 ± 8.3 kg; RMM 17.3 ± 4.7 kg vs. 17.72 ± 4.8 kg and FM% 37.4 ± 6.4% vs. 36.5 ± 6.4; pre-and post-evaluation, respectively). In conclusion, as changes are small, studies should study which factors are associated with bigger changes among these participants and the optimal doses of this exercise.
Keywords: frailty; elder; multicomponent training; body composition Funding: The Elderly EXERNET Multicenter Study was supported by University of Zaragoza (UZ 2008-BIO-01), Centro Universitario de la Defensa de Zaragoza (UZCUD2017-BIO-01), Ministerio de Economía, Industria y Competitividad (DEP2016-78309-R) and Fondos FEDER. AMF received a Grant DGA 2017/2018. The authors are also grateful to all the collaborators and volunteers whose cooperation and dedication made this study possible. Abstract: Endurance tasks involving cycling or running time to exhaustion (TTE) or submaximal isometric tasks to volitional failure, spinal excitability decline as the motoneurons become progressively resistant to activation and the contractile capacity of the muscle fibers is reduced. Transcranial direct current stimulation (tDCS) is a technique that can transiently modulate the activity of a targeted brain area, and consequently, change exercise performance. The purpose of the present systematic review was to analyze the effect of anodal-tDCS on cycling or running TTE, time trial (TT) and sprint performance. We performed systematic literature in the Medline, SPORTDiscus and Science Direct databases. We included only randomized controlled trials with healthy people (18-50 years), in which a tDCS protocol was applied before cycling or running task. A sub-group analysis revealed a positive effect of a-tDCS on TTE (SMD = 0.32; 90% CI = 0.08, 0.56; p = 0.03), but not on TT (p = 0.95) or sprint (p = 0.43) performance. Enhancement in TTE performance could be related to a rise in cortical excitability, which increases output during exercise-thus reducing the supraspinal fatigue. Our results indicated that following a-tDCS can improve cycling and running performance. Contradictory results among studies may be related to the tDCS setup.

Keywords: tDCS; time to task failure; endurance
Funding: This research received no external funding.

Balance Exercise Improves Postural Sway, but Not Visual Feedback Regulation of Body Position
Böhmerová L'ubica *, Luptáková Jana, Schickhofer Peter, Šálová Sabína and Hamar Dušan * Faculty of Sport and Physical Education, Comenius University Bratislava, Bratislava, Slovakia; jana.luptakova@uniba.sk (L.J.); sab.salova@gmail.com (S.S.) * Correspondence: lubica.bohmerova@uniba.sk (B.L.); dusan.hamar@gmail.com (H.D) Abstract: This paper deals with the effect of exercise on an unstable surface on postural sway and visual feedback regulation of body position. A group of eight floorball players (mean age 17.0 ± 1.1 years, body height 176.7 ± 9.5 cm and weight 68.7 ± 7.4 kg) underwent a six-week training program consisting of exercises using fit-ball, BOSU-balance board and wobble board performed for 30 min twice per week. The control group consisted of eight male floorball players (mean age 18.0 ± 0.9 years, height 179.2 ± 4.4 cm, weight 73.0 ± 10.6 kg). Postural sway was assessed by means of the spring-based stabilographic system FiTRO angle sway check, which registers and samples the center of pressure (COP) at the rate of 100 Hz. The mean velocity of COP from 30 s stands was employed as a parameter of postural sway with and without visual control. Visual feedback regulation of body position with visual control was evaluated by means of FiTRO sway check. Subjects must performed corrective movements of the body in a horizontal plane in order to keep the COP displayed on the screen as close as possible to the flowing curve. As a parameter of visual feedback regulation of body position, a mean distance from COP to the flowing curve during the 30-s test was employed. Results showed that in contrast to the control subjects, the experimental group improved significantly postural sway under stable conditions, eyes open (from 19.2 ± 10.0 mm.s −1 to 13.9 ± 4.9 mm.s−1 and closed eyes 38.7 ± 16.4 mm.s−1 to 30.1 ± 12.7 mm.s−1). The index of feedback regulation of body position has changed only nonsignificantly, from 38.9 ± 3.0 to 39.6 ± 2.6 mm. It can be concluded that a six-week balance training improves postural sway, however, does not significantly affect visual feedback regulation of body position.

How Postactivation Performance Enhancements Affect Semi-Tethered Swimming Kinetics
Francisco Cuenca-Fernández *, Jesús Juan Ruiz-Navarro and Raúl Arellano Aquatics Lab, Department of Physical Education and Sports, Faculty of Sport Sciences, University of Granada, Granada, Spain * Correspondence: cuenca@ugr.es; Tel.: +34-627320795 Abstract: The aim of this study was to test if muscular performance is elevated in semi-tethered swimming tests by using a specific dry-land warm-up based on post-activation performance enhancements (denoted PAPE). Ten competitive swimmers conducted two tests to compare the effects of a PAPE warm up on an arm-stroke dry-land test and on a semi-tethered swimming test. Statistical differences between the variables collected through an adapted linear encoder were determined using a paired Student's t-test. The experimental warm-up caused a positive effect on the dry-land test and a detrimental effect on the swimming test. Although improvements in performance were registered in dry-land conditions as a consequence of PAPE effect, these potentiated effects were not transferred into the water-the swimming time was longer (p = 0.014), the distance covered was shorter (p = 0.001) and the swimming power and velocity was lower (p = 0.001). Surprisingly-although the semi-tethered swimming procedure used in this study was not designed as a conditioning exercise to induce PAPE, but as a testing tool to assess the variations on performance as a consequence of it-the analysis of the effects obtained after this kind of protocol suggest a positive a battery of tests: lactate concentration, countermovement jump (CMJ), 20 m sprint (T20 m) and isokinetic knee extension and flexion contractions; at two different time-points: pre-exercise (PRE) and post-exercise (POST). Results revealed significant increases in blood lactate for all loading conditions, however, as sled loadings increased, higher blood lactate concentrations and increments in sprint times during training session were observed. Concerning the mechanical response, significant decreases in CMJ height from PRE to POST were found for all loading conditions. In addition, significant decreases in T20 m performance from PRE to POST were observed for 0% (P = 0.05) and 80% (P = 0.02). No significant differences from PRE to POST were observed for the isokinetic knee extension and flexion contractions. The loss of performance induced during training and the blood lactate concentration were significantly higher as the load increased, indicating that the higher is the load employed during resisted sprint training, the higher is the mechanical and metabolic fatigue produced. On the other hand, concerning the mechanical responses, fatigue in CMJ after the training protocol was similar for all loading conditions. Still, 20-m sprint performance was negatively affected only for 0% and 80%, likely due to different mechanisms: the increase in T20 m for 0% was due to a significant increase in the maximum velocity phase T1020 m, whereas the 80% load did not increase significantly in that phase.

Keywords: omega index; soccer; omega 3
Funding: This research received no external funding.

Effects of Static and Dynamic Balance after Nine weeks of Whole-Body Vibration vs. Unstable-Surface Training in Postmenopausal Women
Nuria Del Cerro 1, *, Jacobo A. Rubio-Arias 2 and Pedro E. Alcaraz Abstract: During the postmenopausal stage in women, there is a bone demineralization that increases health expenditure due to fractures caused by falls. Thus, there is a growing need to create training protocols focused on one of the main factors that cause falls: loss of balance that leads to functional instability. The aim of this study was to analyze the effects of training in whole body vibration vs. unstable surface in the prevention of falls on the static and dynamic balance. We conducted a quasi-experimental design intra-and inter-subject with a control group of 39 sedentary postmenopausal women (58.8 ± 1.6 years). Participants were divided into three experimental groups and control group (G4). The experimental groups performed an incremental training, WBV (G1), unstable surface (G2) and floor (G3), for nine weeks three sessions/week. All participants maintained a static position of semi-squat and performed ankle plantar flexion. The only significant differences were observed between the groups G3 and G4. A decrease in the projection area in static balance was related to an improvement of the functional stability of the subject, and therefore, had more effect on postural control than any disturbance before the fall. Reducing the minimum contact time in dynamic balance is related to the speed of walk and a more reactive step and an improved ability to recover any disturbance of the postural stability. Therefore, the results obtained identify the motor pattern performed during training as a recommended exercise to reduce the projection area in static balance and the contact time in dynamic balance. Abstract: To investigate the relationship of the response to postactivation potentiation (PAP) with scores of physical fitness, 24 professional male soccer players undertook tests of agility, muscular power, aerobic capacity and body composition. Conditioning activities (CA) were performed consisting of plyometrics exercises and sprints with sled towing. In the first and second sessions, body composition, agility, power and aerobic capacity were assessed. At the third session, countermovement jumps (CMJ) were performed with one, three and five min after the execution of the CA. Significant differences were found for CMJ height one, three and five min after the conditioning activity compared to baseline values (3.58%, 5.10%, 5.48%, respectively). There was a significant positive correlation between the level of general physical fitness and PAP (CMJ height increase) 5 min post (r = 0.73). When the athletes were divided into groups with higher and lower physical fitness, the CA caused a significant increase in CMJ height in both groups, but a significant difference (p < 0.05) was observed at all times after PAP induction, with better performance in higher versus lower fitness level. The results suggest that a plyometrics exercises associated with sled towing sprints as a conditioning activity results in an increase in CMJ performance in athletes and that physical fitness directly influences the PAP occurrence, with higher fit players demonstrating an enhanced PAP response.

Keywords
Keywords: postactivation potentiation; physical conditioning; performance; plyometrics Funding: This research received no external funding.

Acute Effects of Cluster Training on Muscle Oxygen Saturation and Movement Velocity during Bench Press Exercise
Ismael Martínez-Guardado *, Alberto Mostazo-Guerra, Adrián González-Custodio, Guillermo Olcina and Rafael Timón GAEDAF Research Group, Faculty of Sport Science, University of Extremadura, Cáceres, Spain * Correspondence: imartinezg@unex.es Abstract: This study evaluates changes in muscle oxygen saturation and movement velocity comparing a traditional training with a cluster configuration during a barbell bench press exercise. A randomized crossover design was performed and 10 trained individuals (age: 24.1 ± 3.3; height: 173.3 ± 5.7; IMC: 22.9 ± 1.3) performed two resistance-training sessions under different protocols separated by at least 72 h: traditional (4 × 6 repetitions at 85% of 1RM with 120 s of recovery between sets) and cluster (4 × 2 + 2 + 2 repetitions at 85% of 1RM with 15 s of inter-set recovery and 90 s between sets). Physical performance was assessed by quantifying movement velocity using a linear position transducer that was fixed to the bar and muscle oxygenation level of the chest was evaluated using a portable NIRS device. No significant differences were found between training protocols. However, the accumulated muscular fatigue caused a higher loss of velocity (p < 0.05) in the 3rd (0.31 ± 0.09 m/s) and 4th (0.27 ± 0.09 m/s) set compared to the 1st (0.37 ± 0.07 m/s) and 2nd (0.33 ± 0.08 m/s) set, only in the traditional protocol. Although no significant differences were found between trainings, the proposed cluster protocol attenuated the velocity loss, which may have caused less fatigue during an upper body exercise.

Keywords: resistance exercise; intra-set rest; fatigue
Funding: This research was funded by the Government of Extremadura with funding from the European Regional Development Fund, Grant Number GR18003.

Effects of Six-Week Integrative Neuromuscular Warm-Up vs. FIFA11+ on Inter-Limb Asymmetries in Young Football Players
J. Marco-Tomàs 1,2 , J. V. Beltrán-Garrido 1 , D. Romero-Rodríguez 3 and M. Madruga-Parera 1,2,3, * 1 University School of Health and Sport (EUSES), University of Rovira Virgili, Amposta, Spain 2 reQsport, Return to Play and Sports Training Center, Barcelona, Spain 3 University School of Health and Sport (EUSES), University of Girona, Girona, Spain * Correspondence: marcmparera@gmail.com; Tel.: +34-972-405-130 Abstract: The aim of this study was to compare the efficacy of two warm-up programs: integrative neuromuscular training (INT) and FIFA11+ on change of direction inter-limb asymmetries (COD ASY ) and change of direction deficit inter-limb asymmetries (CODD ASY ). Five young soccer teams (mean ± SD; age = 10.72 ± 0.72 years) were randomly allocated in either INT (n = 25) or FIFA11+ warm-up program (n = 19). Each group underwent two 20-min sessions per week for 6 weeks. A double 180 • COD and 20-m sprint test were measured, and COD ASY and CODD ASY were computed prior to and at the end of the program. Neither INT nor FIFA11+ warm-up program affected COD ASY (p = 1.000 and p = 0.145, respectively). On the other hand, FIFA11+ warm-up program increased the CODD asymmetries (p = 0.002), while INT warm up program did not affect this variable (p = 0.443).

Keywords: neuromuscular control; imbalances; motor skills
Funding: This research received no external funding.

Effects of Different Ranges of Loads with the Same Mean Relative Intensity on Physical Performance
Juan Sánchez-Valdepeñas 1, *, Javier Riscart-López 1,3 , Juan A. León-Prados 1,2 and Fernando Pareja-Blanco 1,2 1 Physical Performance and Athletic Research Center, Pablo de Olavide University, Seville, Spain 2 Department of Sports and Computing, Sport Faculty, Pablo de Olavide University, Seville, Spain 3 Department of Physical Education and Sports, University of Seville, Seville, Spain * Correspondence: juan_valdemate@hotmail.com Abstract: The effect of loading intensities during resistance training on physical performance has been analyzed without equalizing the efforts between ranges of load. The aim of this study was to analyze the effects on sprint, jump and squat strength gains by different ranges of loads (from 50 to 85% 1RM (R 50-85 , n = 12), from 55 to 75% 1RM (R 55-75 , n = 12) and from 60 to 70% 1RM (R 60-70 , n = 10)) with the same mean relative intensity (65% 1RM). Subjects followed an eight-week (twice per week) velocity-based training program using full squat. Pre-and post-training assessments included: 20-m sprint (T 10 , T 20 and T 10-20 (s)), countermovement jump height (CMJ (cm)) and a progressive loading tests in the SQ exercise (1RM (kg), average velocity attained against all absolute loads common to pre and post (AV, (m·s −1 )). R 60-70 showed significant differences in T 20 and T 10-20 (p ≤ 0.01 and p ≤ 0.001) and R 55-75 in T 20 (p ≤ 0.01) whereas R 50-85 attained significantly greater improvements than R 60-70 in AV (p ≤ 0.05). For that, ranges with low relative intensities could be better to improve sprint and ranges with heavier intensities could be more beneficial to improve squat performance in the entire range of loads (AV).
Keywords: velocity-based training; range of load; mean relative intensity Funding: This research received no external funding.

Monitoring Wellness and External Load during a Major International Field Hockey Tournament
Patricia Varón 1 , Esther Morencos 1 and Blanca Romero-Moraleda 2, * 1 Faculty of Health Sciences, Universidad Francisco de Vitoria, Madrid, Spain; patricia.varon@ufv.es (P.V.); esther.morencos@ufv.es (E.M.) 2 Departamento de Educación Física, Deporte y Motricidad Humana, Universidad Autónoma de Madrid, Madrid, Spain * Correspondence: blanca.romero@uam.es Abstract: Field hockey consists of high-speed running, superimposed on low-speed periods of running where technical and tactical components are intertwined with changes of direction. World-class hockey tournaments often require the athletes to play an average of 5-8 games across a 10-12-day period, with limited recovery time. Time-motion analyses were conducted to assess whether the congested playing schedule and accumulated fatigue can result in reduced playing intensity across a tournament. The aim of the current observational study was to analyze the internal and external load of elite female field hockey players during a world class hockey tournament. Sixteen female field hockey outfield players' external load (GPS) and internal load (psycho-metric questionnaire) data were recorded in all the competitive matches (7). The overall physical output showed no determined pattern throughout