Comparison of Metabolic Power and Energy Cost of Submaximal and Sprint Running Efforts Using Different Methods in Elite Youth Soccer Players: A Novel Energetic Approach.

Sprinting is a decisive action in soccer that is considerably taxing from a neuromuscular and energetic perspective. This study compared different calculation methods for the metabolic power (MP) and energy cost (EC) of sprinting using global positioning system (GPS) metrics and electromyography (EMG), with the aim of identifying potential differences in performance markers. Sixteen elite U17 male soccer players (age: 16.4 ± 0.5 years; body mass: 64.6 ± 4.4 kg; and height: 177.4 ± 4.3 cm) participated in the study and completed four different submaximal constant running efforts followed by sprinting actions while using portable GPS-IMU units and surface EMG. GPS-derived MP was determined based on GPS velocity, and the EMG-MP and EC were calculated based on individual profiles plotting the MP of the GPS and all EMG signals acquired. The goodness of fit of the linear regressions was assessed by the coefficient of determination (R2), and a repeated measures ANOVA was used to detect changes. A linear trend was found in EMG activity during submaximal speed runs (R2 = 1), but when the sprint effort was considered, the trend became exponential (R2 = 0.89). The EMG/force ratio displayed two different trends: linear up to a 30 m sprint (R2 = 0.99) and polynomial up to a 50 m sprint (R2 = 0.96). Statistically significant differences between the GPS and EMG were observed for MP splits at 0-5 m, 5-10 m, 25-30 m, 30-35 m, and 35-40 m and for EC splits at 5-10 m, 25-30 m, 30-35 m, and 35-40 m (p ≤ 0.05). Therefore, the determination of the MP and EC based on GPS technology underestimated the neuromuscular and metabolic engagement during the sprinting efforts. Thus, the EMG-derived method seems to be more accurate for calculating the MP and EC in this type of action.

Match demands of female team sports: a scoping review.

This scoping review aimed to characterize and quantify the external load demands of professional female team sports, in terms of total distance [TD], moderate-speed [MSR] and high-speed running [HSR], sprint, accelerations [ACC], and decelerations [DEC]. A search was conducted in PubMed, Scopus, and Web of Science until 15/04/2023. The Risk of Bias Assessment Tool for Nonrandomized Studies (RoBANS) was used. Eighty-six articles were eligible for inclusion in this review, with 40 in soccer, 23 in rugby (6 rugby union, 3 rugby league, and 14 rugby sevens), 8 in field hockey, 8 in basketball, 6 in handball, and 1 in futsal. Soccer is the most investigated sport, and players perform ~9500 m TD, of which ~580 m is performed in HSR, and with a great number of ACC, DEC, and sprints. Rugby league and union players cover a greater distance (~5450 m) when compared to rugby sevens (~1550 m); however, rugby sevens is more demanding in terms of high-intensity actions. Field hockey players perform ~5400 m TD with high-intensity and sprint actions. Women's indoor sports are less studied, and basketball players cover ~5300 m TD, of which 7% is performed in MSR. Handball players perform ~3500 m TD and cover ~423 m in MSR and ~141 m in HSR, and futsal players perform ~5 m × min-1 in HSR and they do a great number of high-intensity activities (HSR, ACC, and DEC). Considering the high physical demands experienced by female athletes, professionals could use the present results for training and return to competition schedules.

Pupillometry as a new window to player fatigue? A glimpse inside the eyes of a Euro Cup Women's Basketball team.

A rapidly emerging area of interest in high-pressure environments is that of pupillometry, where handheld quantitative infrared pupillometers (HQIPs) are able to track psycho-physiological fatigue in a fast, objective, valid, reliable, and non-invasive manner. However, the application of HQIPs in the context of athlete monitoring is yet to be determined. Therefore, the main aim of this pilot study was to examine the potential usefulness of a HQIP to monitor game-induced fatigue inside a professional female basketball setting by determining its (1) test-retest repeatability, (2) relationship with other biomarkers of game-induced fatigue, and (3) time-course from rested to fatigued states. A non-ophthalmologic practitioner performed a standardized Pupil Light Reflex (PLR) test using a medically graded HQIP among 9 professional female basketball players (2020-2021 Euro Cup) at baseline, 24-h pre-game (GD-1), 24-h post-game (GD+1) and 48-h post-game (GD+2). This was repeated over four subsequent games, equalling a total of 351 observations per eye. Two out of seven pupillometrics displayed good ICCs (0.95-0.99) (MinD and MaxD). Strong significant relationships were found between MaxD, MinD, and all registered biomarkers of game-induced fatigue (r = 0.69-0.82, p < 0.05), as well as between CV, MCV, and cognitive, lower-extremity muscle, and physiological fatigue markers (r = 0.74-0.76, p < 0.05). Three pupillometrics were able to detect a significant difference between rested and fatigued states. In particular, PC (right) (F = 5.173, η2 = 0.115 p = 0.028) and MCV (right) (F = 3.976, η2 = 0.090 p = 0.049) significantly decreased from baseline to GD+2, and LAT (left) (F = 4.023, η2 = 0.109 p = 0.009) significantly increased from GD-1 to GD+2. HQIPs have opened a new window of opportunity for monitoring game-induced fatigue in professional female basketball players. However, future research initiatives across larger and heterogenous samples, and longer investigation periods, are required to expand upon these preliminary findings.

Lifestyle behaviors clusters in a nationwide sample of Spanish children and adolescents: PASOS study.

BACKGROUND: Youth is a vulnerable period. To classify lifestyle behaviors and its relationship with health-related outcomes of Spanish children and adolescents. METHODS: Cross-sectional study including 3261 children aged 7.5-17.5 y (52.8% females). Physical activity (PA), screen-time, sleep time, adherence to Mediterranean diet (MD), weight status (WS) by validated methods. Cluster analysis was run considering chronological age. RESULTS: Six clusters were identified: C1: high screen time, low adherence to MD and sleep time (n = 431,13.20%); C2: high WS, medium adherence to MD,high sleep time, and low screen time (n = 466,14.30%); C3: young group with low screen time and high PA, adherence to MD and sleep (n = 537,16.40%); C4: worst profile regarding adherence to MD, PA, WS and sleep time (n = 609,18.70%); C5: low screen time and PA, high sleep time (n = 804,24.70%); C6: high PA and screen time, low WS (n = 414,12.70%). Mean absolute values were statistically different among PA levels, screen and sleep time, adherence to MD, age, and WS (all p < 0.001). CONCLUSIONS: The most prevalent pattern was low levels of PA, MD, and screen time, and high sleep time. The second most prevalent was characterized by very low levels of PA, sleep time, and adherence to MD, and high screen time, and WS in adolescents. IMPACT STATEMENT: The main identified lifestyle behavior was poor physical activity, low adherence to Mediterranean Diet and high screen and sleep time. Children should increase physical activity levels, adherence to Mediterranean diet, decrease screen and sleep the appropriate hours per day. Families, schools, and medical communities must work together to gloss over present and future diseases. Sleep time had not been previously included in cluster analysis with physical activity, sedentary behaviors, obesity, and nutritional status, thus the present data open a new perspective in Spanish population. Health policies should focus on promoting physical activity, Mediterranean diet, adequate sleep and reducing screen time.

Mixed Training Programs Applied to Young Soccer Players: Effects on Speed-Power Abilities.

We compared the effects of two 4-week strength-power-speed training protocols on physical performance of young soccer players. Twenty-three highly trained under-20 soccer players were randomly allocated to two mixed-training groups: 1) "traditional" (TRAD: n=11), comprising vertically oriented strength-power exercises and linear sprints; or 2) "multidirectional" (MULTI: n=12), combining vertically and horizontally oriented strength-power exercises, linear sprints, and change-of-direction (COD) drills. Squat jump (SJ) and countermovement jump, 2) linear sprint, COD speed, and 3) jump-squat (JS) and hip-thrust (HT) power tests were performed pre- and post-training. Differences were determined using a two-way ANOVA with repeated measures and "target scores" were used to detect real changes in performance. No group-time interactions were found for any of the variables (p>0.05). Significant increases (p<0.05) in 20-m sprint velocity, JS- and HT-power were found in both groups, and in SJ in TRAD. Individual analyses revealed a greater number of meaningful changes in zig-zag velocity in MULTI while most players in TRAD displayed meaningful increases in SJ height. In conclusion, both training protocols resulted in similar adaptations but, at the individual level, it appears that MULTI protocol is superior to improve COD ability while TRAD should be preferred to maximize vertical jumping capabilities during short soccer pre-seasons.

Myotendinous Thermoregulation in National Level Sprinters after a Unilateral Fatigue Acute Bout-A Descriptive Study.

In the last decade there has been a growing interest in infrared thermography in the field of sports medicine in order to elucidate the mechanisms of thermoregulation. The aim of this study was to describe bilateral variations in skin temperature of the anterior thigh and patellar tendon in healthy athletes and to provide a model of baseline tendon and muscle thermoregulation in healthy sprinters following a unilateral isokinetic fatigue protocol. Fifteen healthy national-level sprinters (eleven men and four women), with at least 3 years of athletic training experience of 10-12 h/week and competing in national-level competitions, underwent unilateral isokinetic force testing and electrostimulation in which their body temperature was measured before, during, and after the protocol using an infrared thermographic camera. ANOVA detected a significant difference in the time × side interaction for patellar temperature changes (p ≤ 0.001) and a significant difference in the time/side interaction for quadriceps temperature changes (p ≤ 0.001). The thermal challenge produces homogeneous changes evident in quadriceps areas, but not homogeneous in tendon areas. These data show that metabolic and blood flow changes may depend on the physical and mechanical properties of each tissue. Future research could be conducted to evaluate the predictive value of neuromuscular fatigue in the patellar tendon and quadriceps after exercise in order to optimize post-exercise recovery strategies.

Body surface profile in ambient and hot temperatures during a rectangular test in race walker champions of the World Cup in Oman 2022.

There is current interest in infrared thermography as a method to assess changes in body surface temperature to determine thermoregulatory mechanisms, especially in endurance sports. The aim of this study was to evaluate the effect of two environmental temperatures (17 and 28°C) on body surface temperature in different anterior and posterior aspects of the body during a rectangular test in international walkers of the Spanish National Team. Three international walkers performed a rectangular test, where body temperature was measured at rest, and after the 5th, 10th and 15th run using an infrared thermographic camera in room temperatures at 17 and 28°C. In addition, oxygen consumption was measured simultaneously. ANOVA detected a group × time interaction in the chest and abdomen (right and left), left back and right calf (p = < 0.05), with a trend in the right hamstring (p = 0.053) when comparing 17°C and 28°C. ANOVA detected no significant group × time interaction (p = 0.853) but there was a significant group effect (p = 0.022). The eleven degrees increase in ambient temperature (17 to 28°C) produces changes in almost all anatomical zones, but not homogeneously in international walkers during a rectangular test. This indicates that metabolic and blood flow changes are different depending on the anatomical zone measured.

Relationship Between Athlete-Reported Outcome Measures and Subsequent Match Performance in Team Sports: A Systematic Review.

ABSTRACT: Sansone, P, Rago, V, Kellmann, M, and Alcaraz, PE. Relationship between athlete-reported outcome measures and subsequent match performance in team sports: A systematic review. J Strength Cond Res 37(11): 2302-2313, 2023-Athlete-reported outcome measures (AROMs; e.g., fatigue, stress, readiness, recovery, and sleep quality) are commonly implemented in team sports to monitor the athlete status. However, the relationship between AROMs and match performance indicators is unclear and warrants further investigation. This systematic review examined the relationship between precompetitive AROMs and subsequent match performances of team sport athletes. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, 3 (PubMed, Scopus, and Web of Science) databases were systematically searched to retrieve studies investigating the effects or association of AROMs and match: (a) technical-tactical performance (match-related statistics), (b) physical performance, (c) physiological and (d) perceptual demands, and (e) other measures of performance in adult team sport athletes. Quality assessment of included studies was performed using a modified Black and Downs checklist. Fifteen articles representing 289 team sport athletes were included. Mean quality of included studies was 7.6 ± 1.0 (of 11). Across the included studies, 22 AROMs parameters were used, and 16 different statistical approaches were identified. Approximately 11 of 15 studies used nonvalidated AROMs. Overall, associations or effects of AROMs were found consistently for match-related statistics (7/9 studies), whereas results were unclear for physical performances (3/7 studies), perceptual demands (1/2 studies), or other measures of performance (2/4 studies). Considering the importance of key match-related statistics for success in team sports, this review suggests that monitoring precompetitive AROMs has potential to provide valuable information to coaches. However, it is indispensable to validate AROMs questionnaires and to uniform data collection and statistical procedures before substantiated indications to practitioners can be made.

Does External Load Reflect Acute Neuromuscular Fatigue and Rating of Perceived Exertion in Elite Young Soccer Players?

ABSTRACT: Martínez-Serrano, A, Freitas, TT, Franquesa, X, Enrich, E, Mallol, M, and Alcaraz, PE. Does external load reflect acute neuromuscular fatigue and rating of perceived exertion in elite young soccer players? J Strength Cond Res 37(3): e1-e7, 2023-This study aimed to analyze the acute and residual effects of increased high-speed running (HSR) demands during an in-season training microcycle in young elite soccer players on localized neuromuscular fatigue (NMF) of the knee extensors (KE), posterior chain muscles, and rating of perceived exertion (RPE). Thirty-four elite young soccer players (age = 17.1 ± 0.8 years) were assessed in 2 consecutive days at different time points (baseline, POST-activation gym-based session, POST-small-sided game [SSG], POST-training 1 [TR1], POST-6H, POST-24H, POST-preventive gym-based session, and POST-training 2 [TR2]). Neuromuscular fatigue of the KE and posterior chain muscles was measured with a maximum voluntary isometric contraction (MVIC). External (total distance, number of accelerations or decelerations, and HSR distance) and internal (RPE) load was assessed during the SSG, TR1, and TR2 sessions. Players were divided through a median split, into "HIGH" or "LOW" group according to the training demands. The alpha level was set at p ≤ 0.05. A 2-way mixed effects model ANOVA showed a significant decreased in 90:20 MVIC after TR1 in the "HIGH" HSR group ( p = 0.037; effect size [ES] = 0.45). No significant differences in RPE were found after TR1 ( p = 0.637; ES = 0.58) and TR2 ( p = 0.109; ES = 0.62) when comparing the "HIGH" HSR group with the "LOW" HSR group. Assessing player's force production capabilities can be an effective strategy to detect NMF when HSR demands are acutely increased. Special caution should be taken when prescribing the training load of the training session based solely on RPE, as NMF might be present.

Neuromuscular Performance Changes in Elite Futsal Players Over a Competitive Season.

ABSTRACT: Spyrou, K, Alcaraz, PE, Marín-Cascales, E, Herrero-Carrasco, R, Cohen, DD, and Freitas, TT. Neuromuscular performance changes in elite futsal players over a competitive season. J Strength Cond Res 37(5): 1111-1116, 2023-A professional futsal season imposes a great amount of physiological and mechanical stress on players. The main aim of this study was to examine the changes in neuromuscular performance qualities across the season. Ten professional male players performed a 10-m sprint, standing long jumps (SLJs), and countermovement jumps (CMJs) during the competitive season (i.e., every ∼5 weeks from September to January). A one-way repeated measures ANOVA with post hoc pairwise comparisons and effect sizes (ESs) were used to analyze potential differences among these assessments. A significant and large decline was found in concentric peak power ( p = 0.040; ES = 1.24). A nonsignificant and moderate decrease was observed in sprint ability ( p = 0.155; ES = 1.03), CMJ height ( p = 0.175; ES = 1.00), and SLJ distance ( p = 0.164; ES = 1.03). Regarding other CMJ kinetic variables, nonsignificant and moderate changes were found. In summary, considering the neuromuscular performance tests and variables assessed, only concentric peak power in CMJ decreased significantly across the season; however, nonsignificant decrements were observed in sprinting time, SLJ, CMJ height, and other kinetic metrics. CMJ variables during the jump-land cycle should be incorporated alongside more traditional measures (e.g., jump height) to monitor performance during the season.

Physical Demands of Elite Male and Female 3 × 3 International Basketball Matches.

ABSTRACT: Ferioli, D, Conte, D, Rucco, D, Alcaraz, PE, Vaquera, A, Romagnoli, M, and Rampinini, E. Physical demands of elite male and female 3×3 international basketball matches. J Strength Cond Res 37(4): e289-e296, 2023-This study aimed to (1) characterize the physical demands of 3 × 3 basketball games during live playing time and ball possession and (2) assess the differences in physical demands between male and female players. Following an observational design, video footage from 27 games of the International Basketball Federation 3 × 3 World Cup 2019 were analyzed from 104 international 3 × 3 basketball players ( n = 52 male and n = 52 female players) resulting in a total of 216 (104 male and 112 female) individual game samples. Manual frame-by-frame time-motion analyses determined the relative frequency (n·min -1 ) and duration (%) for several physical demands at different intensities, according to sex, during the live playing time and in ball possession phases. Linear mixed models for repeated measures and effect size (ES) analyses revealed small non-significant differences in the intermittent profile of 3 × 3 basketball games according to sex (total movements per minute, male = 39.3 (38.6-40.1); female = 40.2 (39.5-41.0), estimated marginal means with 95% confidence intervals). Female competitions had significantly greater number of low-intensity activities (LIA, small ES) and high-intensity activities (HIA, small ES) performed per minute over longer games ( small ES), whereas male players had more recovery activities ( small ES). During ball possession, male players spent a larger amount of time performing LIA ( small ES) than female players, who displayed both the greatest number of HIA and the highest percentage of playing time performed at high intensity ( small ES). Overall, these findings suggest that basketball coaches should design sex-specific training sessions based on the specific match demands.

Interrelationships Between Multiple Speed Tests in Youth Soccer: Are Players Equally Efficient at Performing Different Sprint and Change of Direction Tasks?

ABSTRACT: Freitas, TT, Pereira, LA, Alcaraz, PE, Cadore, EL, Grazioli, R, Azevedo, PHSM, Jeffreys, I, and Loturco, I. Interrelationships between multiple speed tests in youth soccer: Are players equally efficient at performing different sprint and COD tasks? J Strength Cond Res 37(4): 848-853, 2023-We investigated the relationships between linear and multidirectional sprint tests in elite young soccer players, using different speed measurements and their associated deficits. Twenty-three under-17 and 17 under-16 soccer players performed, on the same day, 17-m linear sprint (with 10-m split times), curve sprints for "good" and "weak" sides (CSGS and CSWS, respectively), and zigzag and 505 change of direction (COD) tests. The Pearson's product moment test was used to determine the relationships among the tested variables. Significance level was set at p < 0.05. Large and very large significant correlations were observed between CSGS and CSWS and 10-m ( r = 0.73 and r = 0.53, respectively; p < 0.0001) and 17-m sprint velocity ( r = 0.84 and r = 0.74, respectively; p < 0.0001). Moderate and significant associations were identified between zigzag and 17-m sprint performances ( r = 0.40; p = 0.02). No significant relationships were found between 505 performance and 17-m sprint velocity and between the different COD tasks ( p > 0.05). Significant correlations were observed between sprint performance at 10- and 17-m and both CS and COD deficits ( r values ranging from 0.37 to 0.54; p < 0.05). In general, higher linear sprinting velocities were associated with superior performances in smoother multidirectional tasks (i.e., CS and zigzag tests) but not in more aggressive COD maneuvers (i.e., 505). Faster athletes in linear actions presented greater CS and COD deficits. No associations were detected between the different COD measurements, supporting the notion that the technical and mechanical demands of COD actions are angle and velocity dependent. From a practical perspective, comprehensive speed testing batteries (i.e., incorporating linear sprints, CS, and different COD assessments) should be administered to young soccer players, to better understand their ability to change direction and sprint over multiple trajectories.

Strength Deficit in Elite Young Rugby Players: Differences Between Playing Positions and Associations With Sprint and Jump Performance.

ABSTRACT: Zabaloy, S, Giráldez, J, Fink, B, Alcaraz, PE, Pereira, LA, Freitas, TT, and Loturco, I. Strength deficit in elite young rugby players: Differences between playing positions and associations with sprint and jump performance. J Strength Cond Res 36(4): 920-926, 2022-The aims of this study were twofold: to compare the strength-related performance between young forwards and backs rugby players and to examine the correlations between strength deficit (SDef), strength parameters, and sprint and jump performance. Fifty-seven male rugby players (mean ± SD: age, 17.4 ± 1.3 years) performed anthropometric and body composition assessments, vertical jumps, 30-m sprint, and squat (SQ) and bench press (BP) 1-repetition maximum tests (1RM SQ and BP). The differences in the tested variables between positions were analyzed through an independent t-test. A Pearson's correlation coefficient was used to assess the relationships among the variables. Significant differences were observed for anthropometric and body composition measures and jump and sprint performance between positions (p < 0.05; effect size [ES]: 0.60-1.34), except for 5-m velocity (p = 0.080; ES: 0.57). Backs demonstrated higher relative 1RM than forwards in both exercises (p = 0.009 and p = 0.008; ES = 0.88 and 0.91, for SQ and BP, respectively). In addition, backs demonstrated lower SDef from 70 to 90% 1RM (p < 0.048) but small-to-moderate nonsignificant lower SDef against lighter loads compared with forwards (50-60% 1RM). Overall, SDef across all loads (r: -0.378 to -0.529) and 1RM SQ (r: 0.504 to -0.590) were significantly related to sprint performance. Therefore, young rugby players who present lower magnitudes of SDef and superior 1RM SQ performance tend to be faster in linear sprints.

Percentage-Based Change of Direction Deficit: A New Approach to Standardize Time- and Velocity-Derived Calculations.

ABSTRACT: Freitas, TT, Pereira, LA, Alcaraz, PE, Azevedo, PHSM, Bishop, C, and Loturco, I. Percentage-based change of direction deficit: a new approach to standardize time- and velocity-derived calculations. J Strength Cond Res 36(12): 3521-3526, 2022-Change of direction (COD) efforts are crucial in team sports, and an extensive body of research has been devoted to investigating this complex and multifaceted skill. Most studies have assessed players' ability to change direction by reporting completion time or average velocity in different COD tasks. However, it has been argued that these variables may not accurately portray an athlete's true capability to quickly change direction. In this context, new metrics such as the COD Deficit (CODD) have been proposed to provide complementary information on the efficiency to change direction. The current literature presents 2 different CODD computations: time-derived and velocity-derived calculations. Despite both being consistent and representing the same phenomenon, the decision of using one or the other may produce different outcomes, thus influencing coaches' decisions and training strategies. To overcome this issue, we propose a new approach to the computation of the CODD, based on the difference in percentage between linear sprint and COD abilities, in an attempt to standardize the estimation of this variable and simplify the evaluation of COD performance.

Change-of-Direction Ability, Linear Sprint Speed, and Sprint Momentum in Elite Female Athletes: Differences Between Three Different Team Sports.

ABSTRACT: Freitas, TT, Pereira, LA, Alcaraz, PE, Comyns, TM, Azevedo, PHSM, and Loturco, I. Change-of-direction ability, linear sprint speed, and sprint momentum in elite female athletes: differences between three different team sports. J Strength Cond Res 36(1): 262-267, 2022-The aim of this study was to compare the performance of elite female players from 3 different sports in linear sprint and change-of-direction (COD) tests and examine their efficiency for changing direction through the calculation of the COD deficit (i.e., the difference in velocity between a linear sprint and a COD task of equal distance). One hundred fifty-four elite players (rugby, n = 40, national team members; soccer, n = 57 and handball n = 57, first division players from the respective Brazilian National Championships) were assessed in the 20-m linear sprint and Zigzag COD tests. A one-way analysis of variance with a Tukey post hoc was used to detect between-sport differences. Female rugby sevens players achieved faster sprint velocities than handball (20-m: 6.21 ± 0.24 m·s-1; 6.07 ± 0.27 m·s-1, respectively; p < 0.05) and soccer players (5-m: 4.71 ± 0.26 m·s-1 vs. 4.51 ± 0.20 m·s-1; and 20-m: 6.08 ± 0.19 m·s-1; p < 0.05) and exhibited the greatest COD deficits (2.95 ± 0.25 m·s-1; 2.69 ± 0.19 m·s-1; 2.82 ± 0.17 m·s-1, for rugby, handball, and soccer, respectively; p < 0.05). Handball players outperformed all other athletes in the Zigzag test (3.38 ± 0.15 m·s-1; 3.26 ± 0.10 m·s-1; 3.26 ± 0.10 m·s-1, for handball, rugby, and soccer, respectively; p < 0.05) but presented the lowest COD deficits (p < 0.05). Furthermore, soccer players displayed inferior sprint momentum when compared with the other sports (p < 0.05). Linear sprint and COD ability differ significantly among elite female athletes from different team sports, with handball players exhibiting a greater COD speed and efficiency to change direction, with respect to their maximum sprint velocity. The between-sport differences observed suggests that specific training and game demands may affect both sprint and COD performance.

Muscle Activity, Leg Stiffness, and Kinematics During Unresisted and Resisted Sprinting Conditions.

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).

Acute Effects of Progressive Sled Loading on Resisted Sprint Performance and Kinematics.

ABSTRACT: Pareja-Blanco, F, Pereira, LA, Freitas, TT, Alcaraz, PE, Reis, VP, Guerriero, A, Arruda, AFS, Zabaloy, S, De Villarreal, ES, and Loturco, I. Acute effects of progressive sled loading on resisted sprint performance and kinematics. J Strength Cond Res 36(6): 1524-1531, 2022-We examined the effects of 5 loading conditions (0, 20, 40, 60, and 80% of body-mass [BM]) on resisted sprint performance and kinematics in male rugby players over different distances. Ten players from the Brazilian National Team (20.1 ± 3.3 years; 88.7 ± 18.8 kg; 178.3 ± 6.2 cm) performed 20-m sprints under the 5 loading conditions. Sprint times in 5, 10, and 20 m were recorded. Stride length (SL), and hip, knee, and ankle angles were measured using an eight-sensor motion analysis system. The kinematic parameters were calculated over the different distances. Heavier loads led to significantly greater velocity loss (p < 0.001-0.05). Significant reductions in SL were also observed when comparing 0% BM and all resisted sprints in all assessed distances (p < 0.001-0.05, effect size [ES]: 1.35-4.99). Very heavy (80% BM) sled load provoked significantly greater decreases in SL than the rest of loading conditions (p < 0.01-0.05). Important kinematic alterations were observed for all loading conditions and sprint distances when compared with 0% BM (ES: 0.76-1.79, for hip-angle; 0.20-1.40, for knee-angle; and 0.73-1.88, for ankle-angle). Moreover, 80% BM induced significantly higher hip flexion, lower knee flexion, and higher ankle dorsiflexion than 20% BM condition at 5-10 and 10-20 m distances (p < 0.05). Lighter sled loads (<40% BM) seem to be more adequate to improve speed ability without provoking drastic changes in the unloaded sprinting technique, whereas heavier loads may be more suitable for optimizing horizontal force production and thus, acceleration performance.

External match load and the influence of contextual factors in elite futsal.

Quantifying external load during futsal competition can provide objective data for the management of the athlete's performance and late-stage rehabilitation. This study aimed to report the match external load collected via wearable technology according to time periods (i.e., halves) and contextual factors (i.e., team's ranking, match result, and location) in elite futsal. Nine professional male players used a GPS-accelerometer unit during all games of the 2019-2020 season. Player load (PL), PL·min-1, high-intensity acceleration (ACCHI), deceleration (DECHI), explosive movements (EXPL-MOV), and change of direction (CODHI) data were collected. On average, players displayed values of: total PL 3868 ± 594 a.u; PL·min-1: 10.8 ± 0.8 a.u; number of ACCHI: 73.3 ± 13.8, DECHI: 68.6 ± 18.8, EXPL-MOV: 1165 ± 188 and CODHI: 173 ± 29.1. A moderate and significant decrease was found in the 2nd half for total PL (p = 0.03; ES = 0.52), PL·min-1 (p = 0.001; ES = 1.16), DECHI (p = 0.001; ES = 0.83), and EXPL-MOV (p = 0.017; ES = 0.58) compared to the 1st half. Small and nonsignificant differences were found between contextual factors. In summary, this study indicates that futsal players are exposed to high-intensity mechanical external loads, and perform a great number of ACCHI, DECHI, EXPL-MOV and CODHI, without being influenced by the team ranking, result and match location. Coaches and sports scientists are advised to implement speed-power, DEC, and COD activities in the training sessions, and may use these reference values to design specific training and return-to-play plans.

Practices of strength and conditioning coaches in Brazilian elite soccer.

Brazil is the leading global exporter of soccer players, with approximately 2,000 international transfers to different clubs per year. Although Brazilian players compete in the most prestigious soccer leagues worldwide, the habitual training methods, strategies, and routines of Brazilian soccer strength and conditioning coaches (SCCs) are undocumented. This study used a standard online survey to collect and characterize the strength and conditioning practices of Brazilian soccer SCCs. Forty-nine SCCs (age: 40.4 ± 7.5 years; professional experience: 15.3 ± 7.5 years) working in Brazilian professional soccer teams participated in this study. The survey consisted of eight sections: 1) background information; 2) muscular strength-power development; 3) speed training; 4) plyometrics; 5) flexibility training; 6) physical testing; 7) technology use; and 8) programing. Results indicated that training and testing practices of Brazilian SCCs are strongly affected by the congested fixture schedules, extensive traveling distances, and socio-economic disparities between different regions of the country. We describe all these different strategies and methods in detail, providing a comprehensive view and a critical examination of Brazilian soccer strength and conditioning practices. Brazilian SCCs and professional soccer organizations can use the findings from this study to develop training strategies and customize education programs. Practitioners from other countries can use this information to design training programs closely tailored to the background of Brazilian athletes, which may support their adaptation to different competitive scenarios and game demands, such as those found in the most important soccer leagues worldwide.

Validity, reliability, and calibration of the physical activity unit 7 item screener (PAU-7S) at population scale.

BACKGROUND: Validation of self-reported tools, such as physical activity (PA) questionnaires, is crucial. The aim of this study was to determine test-retest reliability, internal consistency, and the concurrent, construct, and predictive validity of the short semi-quantitative Physical Activity Unit 7 item Screener (PAU-7S), using accelerometry as the reference measurement. The effect of linear calibration on PAU-7S validity was tested. METHODS: A randomized sample of 321 healthy children aged 8-16 years (149 boys, 172 girls) from the nationwide representative PASOS study completed the PAU-7S before and after wearing an accelerometer for at least 7 consecutive days. Weight, height, and waist circumference were measured. Cronbach alpha was calculated for internal consistency. Test-retest reliability was determined by intra-class correlation (ICC). Concurrent validity was assessed by ICC and Spearman correlation coefficient between moderate to vigorous PA (MVPA) derived by the PAU-7S and by accelerometer. Concordance between both methods was analyzed by absolute agreement, weighted kappa, and Bland-Altman statistics. Multiple linear regression models were fitted for construct validity and predictive validity was determined by leave-one-out cross-validation. RESULTS: The PAU-7S overestimated MVPA by 18%, compared to accelerometers (106.5 ± 77.0 vs 95.2 ± 33.2 min/day, respectively). A Cronbach alpha of 0.76 showed an acceptable internal consistency of the PAU-7S. Test-retest reliability was good (ICC 0.71 p < 0.001). Spearman correlation and ICC coefficients of MVPA derived by the PAU-7S and accelerometers increased from 0.31 to 0.62 and 0.20 to 0.62, respectively, after calibration of the PAU-7S. Between-methods concordance improved from a weighted kappa of 0.24 to 0.50 after calibration. A slight reduction in ICC, from 0.62 to 0.60, yielded good predictive validity. Multiple linear regression models showed an inverse association of MVPA with standardized body mass index (ß - 0.162; p < 0.077) and waist to height ratio (ß - 0.010; p < 0.014). All validity dimensions were somewhat stronger in boys compared to girls. CONCLUSION: The PAU-7S shows a good test-retest reliability and acceptable internal consistency. All dimensions of validity increased from poor/fair to moderate/good after calibration. The PAU-7S is a valid instrument for measuring MVPA in children and adolescents. TRIAL REGISTRATION: Trial registration number ISRCTN34251612 .