Sprinting is a key component for many individual and team sports. Therefore, to enhance sprint performance, various training methods are widely used by coaches and practitioners, including maximum sprint speed and resisted sprint training. Resisted sprinting with sled towing is a method that has recently received considerable attention from the sport science community. However, to date, no consensus exists regarding its acute and chronic effects in team sport athletes. This narrative review aimed to (a) review and analyze the mechanics of sprinting under unresisted and resisted conditions with a specific focus on team sport disciplines; (b) provide a thorough and applied discussion on the importance of considering acute and chronic effects of sled loading on technique, electromyographic activity, and force production, as well as on the role of muscle architecture and neural factors in sled training; (c) analyze the effects of increasing sled loads during acceleration and maximum velocity phases on contact and flight phases, while concomitantly examining kinetic, kinematic, and neuromuscular aspects, because all these factors affect each other and cannot be properly understood in isolation.

This study assessed the validity of 5-m (TG5) and 10-m (TG10) split times measured with timing gates to estimate maximum sprint speed (MSS) against a criterion measure radar gun (RG) during the maximum velocity phase of a 30-m sprint. Nineteen amateur rugby players performed two 30-m sprints. The timing gates were placed at the starting line and at 5-, 10-, 20-, 25- and 30-m. In addition, a RG was used to measure instantaneous velocity. Both trials per participant were used selected as references. MSS obtained from TG10, TG5 and RG showed high intraclass correlation coefficients (0.971–0.978), low coefficients of variation (1.14–1.70%) and smallest detectable changes ( 0.926, p < 0.001). In conclusion, MSS obtained from TG5, TG10 and RG presented good intra-session reliability. However, practitioners should be aware that substantial differences exist between TG10 and RG. For the assessment of MSS in team-sport athletes, it is recommended the use of TG5 for more accurate estimations when a gold standard criterion is not available.

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 (K _leg ), 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 K _leg 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, K _leg , 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).

The Argentine Rugby Union is a top-tier rugby nation (ranked 8th according to World Rugby), with the Buenos Aires Rugby Union being the largest competitive league. To date, the training practices of Argentinian rugby strength and conditioning coaches have not yet been documented and analyzed. We used an online survey to characterize the training and testing strategies commonly implemented by Argentinian rugby strength and conditioning coaches, which could serve as a guideline for coaching education programs. Thirty-five rugby strength and conditioning coaches (age: 42.0 ± 8.9 years; professional experience: 16.8 ± 8.3 years) working across 35 clubs (from a total of 40 clubs) participated in the study. The survey consisted of eight sections: 1) background information; 2) strength-power development; 3) speed training; 4) plyometrics; 5) flexibility training; 6) physical testing; 7) technology use; and 8) programming. Overall, Argentinian strength and conditioning coaches did not frequently use periodization strategies to structure programs, reported a progressive reduction in training loads across the season, and prescribed primarily Olympic weightlifting and squat as resistance exercises during different training periods. The analyses of speed training revealed high utilization of form-running, plyometrics, and sport-specific movements. Our results also indicated that physical testing and technology may be affected by the economic difficulties of Argentinian clubs. This study presents new information regarding the training methods adopted by Argentinian rugby strength and conditioning coaches, while providing them with new insights to improve their professional practices. Practitioners from different countries working in competitive rugby leagues can use the information provided here to examine their own practices and implement evidence-based programs for elite rugby players.

The aim of this study was to explore the anthropometric profile and evaluate physical fitness variables of the members of the Chile women’s national football team based on their playing positions. Fifty football players participated in this study, which was carried out during the period of training for the France 2019 Women’s World Cup and the Japan 2020 Olympic Games. Body composition and physical condition (muscular strength, sprint, agility, and aerobic fitness) were assessed. The goalkeepers showed greater weight (p < 0.001), height (p = 0.002), and %Fat (p = 0.010) compared to the rest of the playing positions. There were also differences between positions in relative strength (RS) (p = 0.001), running speed at 10 and 30 m (T10 and T30, respectively), agility (AGI) (p < 0.001), and yo-yo test (MYYR1) (p < 0.001). RS, T10, T30, and countermovement jump (CMJ) were significantly correlated (p ≤ 0.05) with anthropometric variables (p ≤ 0.05). MYYR1 was also significantly correlated with anthropometric variables (p ≤ 0.05). In conclusion, goalkeepers show greater weight and height, as well as worse results in MYYR1, AGI, T10, T30, and RS compared to the rest of the players. Forwards present better performance in running speed and agility. Better performance in physical condition is associated with better body composition values (greater muscle mass and lower fat mass). Greater relative strength indicates greater performance in explosive actions. Therefore, to meet the demands of high competition, it is important to establish ideal profiles in anthropometry and physical condition variables based on the playing position.

Span>The purpose of this study was to investigate the interval in which male rugby union players reach maximum speed in a 50 m sprint according to age categories and playing positions. This study also aimed to establish the optimal distance for the assessment of sprint speed and to compare the differences in anthropometrics, sprint and sprint momentum according to the age and playing position. Three hundred amateur rugby players performed anthropometric and physical fitness tests (10, 20, 30, 40 and 50 m sprint times, acceleration, velocity, and sprint momentum) during the in-season period. Participants from different age categories (under 14's (U14), under 16's (U16), under 18's (U18) and Seniors) and positions (forwards and backs) volunteered to participate in this study. Results revealed that most of the U14 and U16 players (58.2% and 55.3%, respectively) reached maximum speed in the interval between 20 and 30 m with lower sprint speed than U18 players and Seniors (44% and 49%, respectively). Comparisons between each interval showed significant differences for all U14 and U16 forwards, suggesting the fastest interval was between 20-30 m. No significative differences were found for U16 backs, U18 and Seniors, between sprint times in the 20-30 m and 30-40 m intervals. In addition, between-group comparisons, demonstrated significant (p < 0.001) differences in U14 when compared to U16, U18 and Seniors in anthropometric variables, sprint times and sprint momentum. In conclusion, this study suggests that the optimal distance for the assessment of sprint speed of rugby players is 30 m and that body mass, sprint momentum and sprint speed clearly discriminate between players of different age categories and playing positions.