The specificity of the Loughborough Intermittent Shuttle Test for recreational soccer players is independent of their intermittent running ability

Intra- and inter-limb strength imbalance and asymmetry in soccer: A comparison of elite senior and junior players

Evaluation of muscle strength imbalance can be an important element in optimizing the training process of soccer players. The purpose of the study was to examine isokinetic peak torque (PT) and total work (TW) exerted by both knee extensors (quadriceps or Q) and flexors (hamstrings or H), intra-limb imbalance and the magnitude and direction of inter-limb asymmetry in top elite senior (n = 109) and junior (n = 74) soccer players. An isokinetic dynamometry was used to measure maximum peak torque of quadriceps (PT-Q) and hamstrings (PT-H) at an angular velocity of 60° ·s-1, as well as the total work for extensors (TW-Q) and flexors (TW-H) at an angular velocity of 240° ·s-1 in the dominant (DL) and non-dominant leg (NDL) during concentric muscle contraction. Intra-limb imbalance and inter-limb asymmetries were calculated using a standard equation. Statistical analysis using t-test and Mann-Whitney U-test revealed: (a) no differences (p > 0.05) between groups for PT-Q and PT-H, (b) greater strength levels (p < 0.05) for TW-Q and TW-H of senior players than juniors, and (c) no differences (p > 0.05) between groups for intra-limb imbalance and inter-limb asymmetry. Additionally, Pearson's chi-kwadrat (χ2) analysis showed no differences (p > 0.05) between groups for intra-limb imbalance and inter-limb asymmetry in relation to the 'normative' values accepted in the literature that indicate an increase in the risk of knee injury. This study shows that isokinetic assessment can be an important tool to identify imbalances/asymmetries and to develop strategies to reduce the risk of muscle injury.

Effects of Combined Horizontal Plyometric and Change of Direction Training on Anaerobic Parameters in Youth Soccer Players

The aim of this study is to investigate whether the combination of soccer training, plyometric training (PT), and change of direction (COD) exercises would enhance anaerobic performance to a greater extent than training on its own in youth U17 soccer players. Twenty youth players participated in this study. Players were randomly separated into two groups: the control group (CG, n = 9) and the intervention group (EX), which performed extra PT and COD exercises (EX, n = 11). The duration of the training program was six weeks. Sprint 10 m, 30 m, countermovement jump (CMJ), single leg countermovement jump (CMJ right and left), squat jump (SJ), 505 test, and Illinois agility test were measured pre and post of the training program. The performance in the 505 test improved for the EX group (right leg: p = 0.031, left leg: p = 0.004). In addition, Illinois test performance increased in the EX group (2.9%, p = 0.019). The performances of the two groups differed significantly in the Illinois agility test (p = 0.001). This study supports that a short-term combined program of PT and COD exercises can improve change of direction ability in youth U17 soccer players. The lack of effect of the intervention program on sprint and jump performance may be due to the type and volume of plyometric exercises used. The results reflect the training principle of specialization of stimulus. The improvement in performance was presented in tests that had similar characteristics to training stimuli.

The Effect of Spinal Asymmetries on Physical Fitness Parameters in Young Elite Soccer Players

The purpose of the study was to examine the effect of spinal asymmetries on specific physical fitness parameters in young elite soccer players. Fifty male soccer players, all members of the under 17 (U17) and 15 (U15) National teams of Cyprus, were initially evaluated for thoracic kyphosis, lumbar lordosis and scoliosis asymmetries. Based on the spinal asymmetries’ initial evaluation, soccer players were categorized into the asymmetry group (AG) and normal group (NG) per spinal asymmetry. Hamstring and lower-back flexibility, countermovement jump (CMJ) and lower body isokinetic maximum force were evaluated between AG and NG. CMJ with arm swing was lower in kyphotic posture AG compared with the NG (AG: 41.70 ± 3.59 cm, NG: 44.40 ± 4.34 cm; p = 0.028). Single leg CMJ was lower in both legs in scoliotic posture AG compared with the NG (right: AG: 17.42 ± 1.86 cm, NG: 19.16 ± 2.42 cm, p = 0.008, left: AG: 17.54 ± 1.33 cm, NG: 19.97 ± 2.91 cm; p = 0.002). Sit-and-reach flexibility was lower in scoliotic posture AG (AG: 20.44 ± 5.76 cm, NG: 24.82 ± 6.83 cm; p = 0.024) and higher in lordotic posture AG (AG: 25.95 ± 6.59 cm, NG: 21.73 ± 6.45 cm; p = 0.04) both compared with the NG. No significant difference was found for quadriceps and hamstrings concentric peak torque between the AG and NG (p > 0.05). The current study revealed that kyphotic and scoliotic posture asymmetries deteriorate neuromuscular explosiveness performance and diminish lower limbs’ flexibility in young International-level soccer players.

Intra- and Inter-Limb Strength Asymmetry in Soccer: A Comparison of Professional and Under-18 Players

(1) Background: the present study examined the isokinetic peak torque exerted by both knee extensors and flexors, anterior–posterior imbalance and the magnitude and direction of inter-limb asymmetry in professional and academy soccer players. (2) Methods: one hundred soccer players (professional = 50, elite academy = 50) volunteered to take part in this investigation. An isokinetic dynamometer was used to measure the knee extensor (quadriceps) and flexors muscle (hamstrings) torques of the limbs as well as inter-limb asymmetries—using a standard percentage difference equation. (3) Results: professional players exhibited significantly greater (effect size [ES] = large) strength levels in the quadriceps and hamstrings under both testing conditions, significantly higher (small to moderate) intra-limb ratio values for 60°·s⁻¹ but not for the 300°·s⁻¹ test condition, significantly (small to moderate) lower inter-limb asymmetry values for all test conditions, with the exception of the hamstrings at 60°·s⁻¹ and the direction of asymmetry was poor to slight, indicating that limb dominance was rarely the same between groups. (4) Conclusions: this study shows that isokinetic assessments, i.e., peak torque exerted by both knee extensors and flexors and intra-limb ratio, and the subsequent inter-limb asymmetry, i.e., magnitude and direction, can differentiate between professional and academy soccer players.

Effect of Postactivation Potentiation After Medium vs. High Inertia Eccentric Overload Exercise on Standing Long Jump, Countermovement Jump, and Change of Direction Performance

ABSTRACT

Beato, M, De Keijzer, KL, Leskauskas, Z, Allen, WJ, Dello Iacono, A, and McErlain-Naylor, SA. Effect of postactivation potentiation after medium vs. high inertia eccentric overload exercise on standing long jump, countermovement jump, and change of direction performance. J Strength Cond Res 35(9): 2616-2621, 2021-This study aimed to evaluate the postactivation potentiation (PAP) effects of an eccentric overload (EOL) exercise on vertical and horizontal jumps and change of direction (COD) performance. Twelve healthy physically active male subjects were involved in a crossover study. The subjects performed 3 sets of 6 repetitions of EOL half squats for maximal power using a flywheel ergometer. Postactivation potentiation using an EOL exercise was compared between a medium (M-EOL) vs. high inertia (H-EOL) experimental condition. Long jump (LJ) was recorded at 30 seconds, 3, and 6 minutes after both EOL exercises and compared with baseline values (control). The same procedure was used to assess countermovement jump (CMJ) height and peak power and 5-m COD test (COD-5m). A fully Bayesian statistical approach to provide probabilistic statements was used in this study. Long jump performance reported improvements after M-EOL and H-EOL exercise (Bayes factor [BF10] = 32.7, strong; BF10 = 9.2, moderate), respectively. Countermovement jump height (BF10 = 135.6, extreme; BF10 > 200, extreme), CMJ peak power (BF10 > 200, extreme; BF10 = 56.1, very strong), and COD-5m (BF10 = 55.7, very strong; BF10 = 16.4, strong) reported improvements after M-EOL and H-EOL exercise, respectively. Between analysis did not report meaningful differences in performance between M-EOL and H-EOL exercises. The present outcomes highlight that PAP using an EOL (M-EOL and H-EOL) improves LJ, CMJ height, CMJ peak power, and COD-5m in male athletes. The optimal time window for the PAP effect was found for both EOL conditions from 3 to 6 minutes. However, M-EOL and H-EOL produce similar PAP effect on LJ, CMJ, and COD-5m tasks.

Loaded Plyometrics and Short Sprints with Change-of-Direction Training Enhance Jumping, Sprinting, Agility, and Balance Performance of Male Soccer Players

This project investigated effects of 8 weeks of biweekly loaded combined plyometric and short sprint with change-of-direction training an in-season regimen of young soccer players. An experimental (n = 17, age: 16.5 ± 0.5 years, body mass: 64.5 ± 5.2 kg, height: 1.73 ± 0.07 m,) and control group (n = 17, age: 16.7 ± 0.5 years, body mass: 65.6 ± 4.8 kg, height: 1.74 ± 0.07 m) were tested pre- and post-intervention for squat-jump (SJ), countermovement-jump (CMJ), and five-jump test (5JT), 10 m and 30 m sprint performance, change-of-direction ability, and dynamic balance performance. The experimental group (EG) outperformed the control group (CG) over 8 weeks in jumping (p < 0.001; d = 0.98–1.17), 10 m sprinting (p < 0.001; d = 0.94), change-of-direction ability (p < 0.001; d = 1.24), and dynamic balance performance (p < 0.001; d = 0.53–0.74). We conclude that adding biweekly loaded plyometric with short sprints and change-of-direction training to habitual training improves athleticism of young soccer players. Therefore, loaded plyometric with short sprints and change-of-direction training should be implemented as a part of research-informed soccer training.

Associations Between Variations in Accumulated Workload and Physiological Variables in Young Male Soccer Players Over the Course of a Season

This study sought to analyze the relationship between in-season training workload with changes in aerobic power (VO_{2m ax} ), maximum and resting heart rate (HR _max and HR _rest ), linear sprint medium (LSM), and short test (LSS), in soccer players younger than 16 years (under-16 soccer players). We additionally aimed to explain changes in fitness levels during the in-season through regression models, considering accumulated load, baseline levels, and peak height velocity (PHV) as predictors. Twenty-three male sub-elite soccer players aged 15.5 ± 0.2 years (PHV: 13.6 ± 0.4 years; body height: 172.7 ± 4.2 cm; body mass: 61.3 ± 5.6 kg; body fat: 13.7% ± 3.9%; VO_{2m ax} : 48.4 ± 2.6 mL⋅kg^-1⋅min^-1), were tested three times across the season (i.e., early-season (EaS), mid-season (MiS), and end-season (EnS) for VO_{2m ax} , HR _max , LSM, and LSS. Aerobic and speed variables gradually improved over the season and had a strong association with PHV. Moreover, the HR _max demonstrated improvements from EaS to EnS; however, this was more evident in the intermediate period (from EaS to MiS) and had a strong association with VO_{2m ax} . Regression analysis showed significant predictions for VO_{2m ax} [F _{( 2, 20)} = 8.18, p ≤ 0.001] with an R ² of 0.45. In conclusion, the meaningful variation of youth players' fitness levels can be observed across the season, and such changes can be partially explained by the load imposed.

Analysis of Fitness Status Variations of Under-16 Soccer Players Over a Season and Their Relationships With Maturational Status and Training Load

The purposes of this study were (i) to analyze the variations in maximal oxygen consumption (VO_2max), maximal heart rate (HR_max), heart rate at rest, acceleration, maximal speed, agility, anaerobic sprint test (RAST) of peak power (RPP), RAST of minimum power, RAST of average power (RAP), and RAST of fatigue index (RFI) during the competitive season, using maturation status and accumulated training load as covariates, and (ii) to describe the differences between responders and non-responders in relation to baseline levels. Twenty-three elite players from the same team competing in the national under-16 competitions were evaluated for 20 weeks in period 1 (before league), middle (mid league), and period 2 (after league). The VO_2max (p = 0.009), maximal speed (p = 0.001), RPP (p < 0.001), RAP (p < 0.001), and RFI (p < 0.001) significantly changed across the assessment periods. Interestingly, using accumulated training load and maturation status as covariates revealed no statistical significance (p > 0.05). When analyzing responders and non-responders, only HR_max (between periods 1 and 2) showed no differences between the groups. As a conclusion, it can be seen that accumulated training load and maturation status play an important role in the differences observed across the season. Thus, coaches should consider the importance of these two factors to carefully interpret fitness changes in their players and possibly adjust training decisions according to the maturation level of the players.

A 1-Minute Re-warm Up at High-Intensity Improves Sprint Performance During the Loughborough Intermittent Shuttle Test

Although a 3- to 7-min re-warm up (RW) elicits performance and physiological benefits after half-time (HT), a time-efficient and feasible RW protocol is required for the use of an RW in the athletic setting. This study aimed to investigate the effect of a 1-min RW at high-intensity on the performance and physiological responses during the Loughborough Intermittent Shuttle Test (LIST). In a randomized and counterbalanced cross-over design, 12 male amateur intermittent team sports players (soccer, basketball, handball, and lacrosse; age, 22 ± 2 years; height, 1.70 ± 0.08 m; body mass, 65.1 ± 8.3 kg; body mass index, 22.4 ± 1.9 kg m⁻²; VO_2max, 53.5 ± 4.5 ml kg⁻¹ min⁻¹) performed the LIST. The LIST comprised two 45-min halves separated by a 15-min HT. Each half comprised repetitions of exercise cycles consisting of 3 × 20-m walking, 1 × 20-m maximal sprint, 3 × 20-m jogging, and 3 × 20-m running. During the HT, the participants were assigned to a control trial (CON; 15-min seated rest) or an RW trial (1-min running at 90% of the maximal oxygen uptake after a 14-min seated rest). Compared to the CON, the RW prevents reductions in sprint performance at the fourth and sixth periods of the LIST (fourth: 2.4%, p = 0.002, d = 1.68, sixth: 3.6%, p = 0.012, d = 1.74) and a decrement of gastrointestinal temperature during HT (0.5°C, p = 0.010, d = 1.41). Moreover, the RW decreased the electromyogram amplitude of maximal voluntary contraction (MVC) after HT (12%, p = 0.017, d = 1.12) without a decrease of maximal voluntary contraction force, suggesting an increased neuromuscular efficiency (9%, p = 0.048, d = 0.58). The RW also increased the mean heart rate in the initial part of the second half (4 bpm, p = 0.016, d = 0.38). In conclusion, the RW improved sprint performance, core temperature, muscle activation, and heart rate in the second half of the LIST. The findings suggest that the RW should be recommended for intermittent team sports players when longer RWs are not possible.

Testing protocol affects the velocity at VO2max in semi-professional soccer players

To compare three different protocols to assess the velocity associated with the maximal oxygen uptake (V_max) in soccer players. Sixteen semi-professional soccer players performed three maximum incremental tests on treadmill: two continuous protocols [1 km·h^-1·min^-1 (CP1); and 1 km·h^-1 every 2 min (CP2)], and one discontinuous (DP) protocol to determine V_max, maximum oxygen uptake (VO_2max) and oxygen cost of running (i.e., the slope of the VO₂ vs velocity relationship at submaximal exercise). V_max was higher in CP1> CP2> DP (19.4 ± 1.7, 17.4 ± 1.2, 16.1 ± 1.1 km·h^-1 for CP1, CP2, and DP, respectively; P < 0.05 ES: 0.09 to 3.36). No difference in VO_2max was found between CP1, CP2 and DP (P > 0.05). Oxygen cost of running showed between-protocol differences (CP1> CP2> DP; P < 0.05; ES: 0.28 to 3.30). V_max was higher when determined using continuous vs discontinuous protocols due to the greater overestimation in oxygen cost of running. Such differences in V_max should be considered to optimize acute physiological responses during high-intensity running activities.

Sustained Passing Performance of Elite and Subelite Female Soccer Players Following a Female Match-Specific Exercise Protocol

PURPOSE

This study examined the maintenance of passing performance following soccer-specific high-intensity intermittent exercise in elite (n = 9) and subelite (n = 11) Western Australian female soccer players (19.5 [2.5] y).

METHODS

A total of 20 participants completed the Loughborough Soccer Passing Test (LSPT) prior to, during, and following 90 minutes of a modified, female-specific, individualized exercise protocol (Loughborough Intermittent Shuttle Test [LIST]) to simulate 2 halves of a soccer match. Performance in the LSPT was calculated by adding "raw time" to the accumulated "penalty time" for each test.

RESULTS

Elite players recorded greater distances (t58 = 4.671, P < .001, effect size [ES] = 1.21) and higher derived VO2max values (t58 = 4.715, P < .001, ES = 1.20) for the LIST exercise protocol over the subelite players. The total performance times for each LSPT were longer in the subelites in comparison with the elites, with a very large ES difference seen in post-LIST1 (t18 = -6.64, P < .001, ES = 2.99) and post-LIST2 (t18 = -9.143, P < .001, ES = 4.12). No between-groups differences were identified for "raw time" at any time point. Hence, all reported LSPT performance differences are attributed to "penalty time."

CONCLUSION

These data suggest that elite players can sustain their passing performance more efficiently throughout match play that can subelite female soccer players. These findings may contribute to future talent-identification testing by helping to distinguish between elite- and subelite-level players through sustained passing performance. Coaches may also use this information to better inform best-practice training methods through modification of male soccer-specific high-intensity intermittent exercise to a female cohort.

The Training of Short Distance Sprint Performance in Football Code Athletes: A Systematic Review and Meta-Analysis

Background

Short-sprint (≤ 20 m) performance is an important quality for success in the football codes. Therefore, developing an evidence base for understanding training methods to enhance short-sprint performance is key for practitioners. However, current systematic reviews are limited by (1) a lack of focus on football code athletes, (2) a lack of consideration of all training modalities and (3) a failure to account for the normal training practices undertaken by intervention groups within their analysis. Therefore, this review aimed to (1) conduct a systematic review of the scientific literature evaluating training interventions upon short-sprint performance within football code athletes, (2) undertake a meta-analysis to assess the magnitude of change of sport-sprint performance following training interventions and (3) identify how moderator variables affect the training response.

Methods

A systematic search of electronic databases was conducted. A random-effects meta-analysis was performed to establish standardised mean difference with 95% confidence intervals. This identified the magnitude and direction of the individual training effects of intervention subgroups (primary, secondary, combined-specific, tertiary and combined training methods) on short-sprint performance while considering moderator variables (i.e., football code, sex, age, playing standard, phase of season).

Results

121 studies met the inclusion criteria, totalling 3419 athletes. Significant improvements (small-large) were found between pre- and post-training in short-sprint performance for the combined, secondary, tertiary and combined-specific training methods. No significant effect was found for primary or sport only training. No individual mode was found to be the most effective. Between-subgroup analysis identified that football code, age, playing standard and phase of season all moderated the overall magnitude of training effects.

Conclusions

This review provides the largest systematic review and meta-analysis of short-sprint performance development methods and the only one to assess football code athletes exclusively. Practitioners can apply combined, secondary and tertiary training methods to improve short-sprint performance within football code athletes. The application of sport only and primary methods does not appear to improve short-sprint performance. Regardless of the population characteristics, short-sprint performance can be enhanced by increasing either or both the magnitude and the orientation of force an athlete can generate in the sprinting action.

Trial Registration

OSF registration https://osf.io/kshqn/.

Electronic supplementary material

The online version of this article (10.1007/s40279-020-01372-y) contains supplementary material, which is available to authorized users.

Match-Play Temporal and Position-Specific Physical and Physiological Demands of Senior Hurlers

Young, D, Beato, M, Mourot, L, and Coratella, G. Match-play temporal and position-specific physical and physiological demands of senior hurlers. J Strength Cond Res 34(6): 1759-1768, 2020-The aims of the current study were to examine the temporal differences in match-running performances and heart rate (HR) in elite senior hurling players between halves of play and field positions. Global positioning systems (10 Hz) and HR monitors were used to collect data from 48 players over 18 games. Running performances (total distance [TD], relative distance, high-speed running [HSR], sprint efforts [SE], mean length of sprints, and sprint distance [SD]) and HR values (HRmean and HRpeak) were assessed. Decrements in TD (p = 0.009, effect size [ES] = -0.15), relative distance (p = 0.009, ES = -0.18), HSR (p = 0.001, ES = -0.28), SE (p = 0.001, ES = -0.23), SD (p = 0.001, ES = -0.24), HRmean (p < 0.001, ES = -0.38), and HRpeak (p < 0.001, ES = -0.21) were found between halves. Half backs showed between-half decrements in all metrics (p < 0.05) except SD (p = 0.130, ES = -0.26). Midfielders (p < 0.001, ES = -0.68) and half forwards (p < 0.001, ES = -0.79) experienced second-half decrements in HSR. No decrements (p > 0.05) in running performances were found between halves for full backs. HRmean was lower in full backs (p = 0.007, ES = -0.46) and half backs (p = 0.001, ES = -0.76) in the second half. Coaches should consider the specific HSR between-half temporal decrements in half backs, midfielders, and half forwards, and customize training program design to minimize these decrements.

Quadriceps and Gastrocnemii Anatomical Cross-Sectional Area and Vastus Lateralis Fascicle Length Predict Peak-Power and Time-To-Peak-Power

Purpose: The current study investigated the role of quadriceps and gastrocnemii size and vastus lateralis and gastrocnemius medialis muscle architecture in peak-power and time-to-peak-power exerted in an all-out Wingate test. Twenty-one amateur cyclists were recruited. Methods: Quadriceps and gastrocnemii anatomical cross-sectional area (ACSA), and vastus lateralis and gastrocnemius medialis pennation angle and fascicle length were measured using ultrasound. Relative peak-power (normalized per body mass) and time-to-peak-power were measured during a 30s all-out test. Results: Relative peak-power was correlated with quadriceps ACSA (r = 0.896, p < .001), gastrocnemii ACSA (r = 0.811, p < .001), vastus lateralis (r = 0.787, p < .001) and gastrocnemius medialis pennation angle (r = 0.638, p < .003). Multiple regression revealed that quadriceps and gastrocnemii ACSA accounted for 85% (R²= 0.85) of peak-power variance. Time-to-peak-power showed very large (r = -0.868, p < .001) and large correlation (r = -0.680, p = .001) with VL and GM fascicle length, respectively. Multiple regression analysis revealed that VL fascicle length explained 75% (R²= 0.75) of the time-to-peak-power variance. Conclusions: Quadriceps and gastrocnemii ACSA largely explained relative peak-power in an all-out Wingate test. Vastus lateralis fascicle length was the main predictor of the time-to-peak-power. Muscle architecture characteristics seem to be involved in the power generating capacity.

Short-Term Repeated-Sprint Training (Straight Sprint Vs. Changes of Direction) in Soccer Players

Repeated-sprint training (RST) is considered a critical training method in team sports. It is well known that RST effects may depend on several variables such as the duration of the protocol and repeated-sprint methodology. Few studies have evaluated very short-term protocols and compared different RST modalities. The aim of this study was to compare the effectiveness of 2 week RST including straight sprints or changes of direction (CODs) on physical performance in a sample of soccer players. This study used a randomised pre-post parallel group trial design. The participants were assigned to either an RST group using straight sprints (RST-SS = 18 players) or an RST group using CODs (RST-COD = 18 players). The protocols were: 3 sets of 7 x 30 m sprints for the RST-SS and 7 x 20 + 20 m (one COD of 180°) for the RST-COD, with 20 s and 4 min recovery between sprints and sets, respectively. The following evaluations were performed: 10 and 20 m sprint, agility test, repeated sprint test (RSTbest and RSTmean), and Yo-Yo Recovery Level 1. After the training period, the RST-SS did not report any performance variation, while the RST-COD showed improvements in the 10 m sprint and RSTbest (effect size = 0.70 and 0.65, respectively). The between-group analysis did not report any statistical difference between the RST-SS and the RST-COD. In conclusion, this study did not support the utilisation of a very short-term RST protocol with soccer players, however, the RST-COD presented some additional benefits in sprint performance compared to the RST-SS.

Effects of in-season enhanced negative work-based vs traditional weight training on change of direction and hamstrings-to-quadriceps ratio in soccer players

The present study investigated the effects of in-season enhanced negative work-based training (ENT) vs weight training in the change of direction (COD), sprinting and jumping ability, muscle mass and strength in semi-professional soccer players. Forty male soccer players participated in the eight-week, 1 d/w intervention consisting of 48 squat repetitions for ENT using a flywheel device (inertia=0.11 kg·m^-2) or weight training (80%1 RM) as a control group (CON). Agility T-test, 20+20 m shuttle, 10 m and 30 m sprint, squat jump (SJ) and countermovement jump (CMJ), lean mass, quadriceps and hamstrings strength and the hamstrings-to-quadriceps ratio were measured. Time on agility T-test and 20+20 m shuttle decreased in ENT (effect-size =-1.44, 95% CI -2.24/-0.68 and -0.75, -1.09/-0.42 respectively) but not in CON (-0.33, -0.87/0.19 and -0.13, -0.58/0.32). SJ and CMJ height increased in both ENT (0.71, 0.45/0.97 and 0.65, 0.38/0.93) and CON (0.41, 0.23/0.60 and 0.36, 0.12/0.70). Overall, quadriceps and hamstrings strength increased in both ENT and CON (0.38/0.79), but the hamstrings-to-quadriceps ratio increased in ENT (0.31, 0.22/0.40) but not in CON (0.03, -0.18/0.24). Lean mass increased in both ENT (0.41, 0.26/0.57) and CON (0.29, 0.14/0.44). The repeated negative actions performed in ENT may have led to improvements in braking ability, a key point in COD performance. Semi-professional soccer players may benefit from in-season ENT to enhance COD and the negative-specific adaptations in muscle strength and hamstrings-to-quadriceps ratio.

Monitoring Fatigue During Intermittent Exercise With Accelerometer-Derived Metrics

The aim of this study was to assess the sensitivity of accelerometer-derived metrics for monitoring fatigue during an intermittent exercise protocol. Fifteen university students were enrolled in the study (age 20 ± 1 years). A submaximal intermitted recovery test (Sub-IRT) with a duration of 6 min and 30 s (drill 1) was performed. In order to increase the participants’ fatigue, after that, a repeated sprint protocol (1×6 maximal 20 m sprints) was performed. Following that, participants repeated the Sub-IRT (drill 2) to evaluate the external and internal training load (TL) variations related to fatigue. Apex 10 Hz global navigation satellite system (GNSS) units were used to collect the variables total distance (TD), high metabolic distance (HMD), relative velocity (RV), average metabolic power (MP), heart rate maximal (HRmax) and mean (HRmean), muscular (RPEmus) and respiratory rating of perceived exertion (RPEres), dynamic stress load (DSL), and fatigue index (FI). A Bayesian statistical approach was used. A likelihood difference (between drill 1 and drill 2) was found for the following parameters: TD (BF₁₀ = 0.33, moderate per H₀), HMD (BF₁₀ = 1.3, anecdotal), RV (BF₁₀ = 0.29, moderate per H₀), MP (BF₁₀ = 1.3, anecdotal), accelerations (BF₁₀ = 1.6, anecdotal ), FI (BF₁₀ = 4.7, moderate), HRmax (BF₁₀ = 2.2, anecdotal), HRmean (BF₁₀ = 4.3, moderate), RPEmus (BF₁₀ = 11.6, strong), RPEres (BF₁₀ = 3.1, moderate), DSL (BF₁₀ = 5.7, moderate), and DSL•m⁻¹ (BF₁₀ = 4.3, moderate). In conclusion, this study reports that DSL, DSL•m⁻¹, and FI can be valid metrics to monitor fatigue related to movement strategy during a standardized submaximal intermittent exercise protocol.

Effects of Plyometric and Directional Training on Physical Fitness Parameters in Youth Soccer Players

PURPOSE

To investigate whether the combination of a soccer training session, plyometric training, and change-of-direction (COD) exercises would enhance soccer ability to a greater extent than training on its own in youth soccer players.

METHODS

Thirty-one youth players participated in this study (age: 12 [0.8] y). Players were randomly separated into 2 groups: a control group (CG, n = 14) and an intervention group that performed extra plyometric training and COD exercises (intervention group, n = 17). The duration of the training program was 6 wk. Players' performances in sprint (10 and 30 m), countermovement jump, squat jump, long jump, multiple 5-bound, T-test, and Yo-Yo Intermittent Endurance Test 1 were measured before and after the training program.

RESULTS

Players' performance in acceleration, T-test, and long jump improved in both groups (P = .03, P = .002, and P = .001, respectively). Squat-jump performance increased in the intervention group (15.2%, P = .003) and slightly decreased in the control group (P = .003). The performances of the 2 groups differed significantly in squat jump and long jump (P = .003 and P = .038, respectively).

CONCLUSIONS

This study indicates that a short-term combined program of plyometric training and COD exercises can improve jumping ability, acceleration, and endurance parameters in youth soccer players. The small training effect could be explained when taking into account the level of the participants, the duration of the program, and the low volume of COD exercises used.

Match-Play Demands of Elite U17 Hurlers During Competitive Matches

Young, D, Mourot, L, Beato, M, and Coratella, G. Match-play demands of elite U17 hurlers during competitive matches. J Strength Cond Res 34(7): 1982-1989, 2020-The current study aimed to quantify the match-play workload in elite male under 17 hurlers, measuring the differences between the first and second halves and between positions. Global positioning system (10-Hz) and heart rate monitors were used to collect data from 76 players during 18 matches. Players' total distance (TD), relative distance (RD), high-speed running (HSR), the number and length of sprints, and the total sprint distance (TSD) was 6,483 ± 1,145 m, 108 ± 19 m·min, 583 ± 215 m, 18 ± 6, 15 ± 3 m, and 272 ± 77 m, respectively. Peak and mean heart rate were 194 ± 8 b·min and 167 ± 4 b·min, respectively. Decrements in TD (p < 0.001, effect size [ES] = 0.72), RD (p < 0.001, ES = 0.72), HSR (p < 0.001, ES = 0.55), the number of sprints (p < 0.001, ES = 0.57), mean length of sprint (p < 0.011, ES = 0.25), TSD (p < 0.001, ES = 0.69), mean heart rate (p < 0.001, ES = 0.35), and peak heart rate (p < 0.001, ES = 0.52) were found between halves. Largely-to-very largely greater TD, RD, and HSR were covered by midfielders, half-backs, and half-forwards compared with full-backs and full-forwards. No between-position difference was found in peak and mean heart rate. The current results are the first to highlight the differences in external and internal position-specific workload in elite male under 17 hurlers. Coaches need to consider the position-specific demands and between-half drop-off to prepare young hurlers appropriately to repeat the match-play performances of competition.

Effect of ramp slope on different methods to determine lactate threshold in semi-professional soccer players

The present study aimed to investigate the effect of stage duration in incremental protocols on lactate threshold (LT), determined by different methods. Sixteen semi-professional soccer-players performed a 4-min stage incremental discontinuous (DP) and two maximal incremental running continuous (1 km h^-1· min^-1, CP1; and 1 km h^-1·2 min^-1 CP2) protocols. Blood-lactate concentration [La^-] was measured at baseline and during the protocols. LT was determined using D_MAX, D_MAX-MOD, 4-mM⋅L^-1, Δ1-mM⋅L^-1 and Log-Log methods. Log-Log showed no difference in LT between CP1, CP2 and DP. Conversely, LT was determined at higher velocity in CP1 than CP2 for D_MAX (15.2 ± 0.5 vs 14.4 ± 1.2 km⋅h^-1, P = 0.002), D_MAX-MOD (16.0 ± 0.5 vs 14.7 ± 1.3 km⋅h^-1, P < 0.001), 4-mM⋅L^-1 (15.5 ± 1.4 vs 14.4 ± 1.2 km⋅h^-1, P < 0.001), Δ1-mM⋅L^-1 (15.5 ± 1.3 vs 14.4 ± 1.2 km⋅h^-1, P < 0.001). Higher LT in CP1 than DP for D_MAX (15.2 ± 0.5 vs 13.0 ± 1.0 km⋅h^-1, P < 0.001) and D_MAX-MOD (16.0 ± 0.5 vs 13.6 ± 1.6 km⋅h^-1, P < 0.001) was found (P < 0.001). Log-Log resulted in shorter but accurate protocols to determine LT.

Comparative effects of single vs. double weekly plyometric training sessions on jump, sprint and change of directions abilities of elite youth football players

BACKGROUND

Plyometrics are widely implemented as training methodology for enhancing functional sports performance. Although several studies have analyzed the plyometrics effects due to training plans with a frequency of 2-3 times a week, few of them provided evidence supporting an equal efficiency of similar training programs implementing lower training frequency such as one training session a week.

METHODS

Twenty-one players (elite academy, Switzerland) were included in the current study (mean±SD; age 17±0.8 years, weight 70.1±6.4 kg, height 177.4±6.2 cm). This study used a randomised pre-post parallel group trial design. The participants were assigned to either a low-volume plyometric training group (LPG=10 participants) or a high-volume plyometric training group (HPG=11 participants). A long jump test, a single-leg triple hop test, sprint (10, 30 and 40 m) and 505 change of directions test were performed.

RESULTS

Exercise-induced meaningful changes in performance for both LPG and HPG occurred after the training. LPG and HPG reported improvements in long jump (ES=1.0 and 0.77), triple hop right (ES=0.32 and 0.28), triple hop left (ES=0.46 and 0.32), 10 m sprint (ES=0.62 and 1.0).

CONCLUSIONS

Both LPG and HPG are effective training modalities inducing benefits in jump and sprint tests for elite young football players. Fitness coaches and sports scientists could integrate their training plans with the protocols described in this study.

Specific Adaptations in Performance and Muscle Architecture After Weighted Jump-Squat vs. Body Mass Squat Jump Training in Recreational Soccer Players

Coratella, G, Beato, M, Milanese, C, Longo, S, Limonta, E, Rampichini, S, Cè, E, Bisconti, AV, Schena, F, and Esposito, F. Specific adaptations in performance and muscle architecture after weighted jump-squat vs. body mass squat jump training in recreational soccer players. J Strength Cond Res 32(4): 921-929, 2018-The aim of the present study was to compare the effects of weighted jump-squat training (WJST) vs. body mass squat jump training (BMSJT) on quadriceps' muscle architecture, lower-limb lean-mass (LM) and muscle strength, performance in change of direction (COD), and sprint and jump in recreational soccer players. Forty-eight healthy soccer players participated in an offseason randomized controlled trial. Before and after an 8-week training intervention, vastus lateralis pennation angle, fascicle length, muscle thickness, LM, squat 1RM, quadriceps and hamstrings isokinetic peak torque, agility T-test, 10-and 30-m sprints, and squat-jump (SJ) were measured. Although similar increases were observed in muscle thickness, fascicle length increased more in WJST (Effect size [ES] = 1.18, 0.82-1.54) than in BMSJT (ES = 0.54, 0.40-0.68), and pennation angle increased only in BMSJT (ES = 1.03, 0.78-1.29). Greater increases in LM were observed in WJST (ES = 0.44, 0.29-0.59) than in BMSJT (ES = 0.21, 0.07-0.37). The agility T-test (ES = 2.95, 2.72-3.18), 10-m (ES = 0.52, 0.22-0.82), and 30-m sprints (ES = 0.52, 0.23-0.81) improved only in WJST, whereas SJ improved in BMSJT (ES = 0.89, 0.43-1.35) more than in WJST (ES = 0.30, 0.03-0.58). Similar increases in squat 1RM and peak torque occurred in both groups. The greater inertia accumulated within the landing phase in WJST vs. BMSJT has increased the eccentric workload, leading to specific eccentric-like adaptations in muscle architecture. The selective improvements in COD in WJST may be related to the increased braking ability generated by the enhanced eccentric workload.

The Yo-Yo Intermittent Tests: A Systematic Review and Structured Compendium of Test Results

Background: Although Yo-Yo intermittent tests are frequently used in a variety of sports and research studies to determine physical fitness, no structured reference exists for comparison and rating of test results. This systematic review of the most common Yo-Yo tests aimed to provide reference values for test results by statistical aggregation of published data.

Methods: A systematic literature search for articles published until August 2017 was performed in MEDLINE, Web of Science, SPORTDiscus and Google Scholar. Original reports on healthy females and males ≥16 years were eligible for the analysis. Sub-maximal test versions and the Yo-Yo Intermittent Recovery Level 1 Children's test (YYIR1C) were not included.

Results: 248 studies with 9,440 participants were included in the structured analysis. The Yo-Yo test types most frequently used were the Yo-Yo Intermittent Recovery Level 1 (YYIR1, 57.7%), the Yo-Yo Intermittent Recovery Level 2 (YYIR2, 28.0%), the Yo-Yo Intermittent Endurance Level 2 (YYIE2, 11.4%), and the Yo-Yo Intermittent Endurance Level 1 (YYIE1, 2.9%) test. For each separate test, reference values (global means and percentiles) for sports at different levels and both genders were calculated.

Conclusions: Our analysis provides evidence that Yo-Yo intermittent tests reference values differ with respect to the type and level of sport performed.The presented results may be used by practitioners, trainers and athletes to rate Yo-Yo intermittent test performance levels and monitor training effects.

The effect of two different speed endurance training protocols on a multiple shuttle run performance in young elite male soccer players

There is not enough evidence on the impact of different speed endurance training regimes on footballers' ability to perform multiple shuttle run performance. This study examined the effect of 4 weeks of speed endurance maintenance (SEM) and speed endurance production (SEP) training on the 5-meter multiple shuttle run test (5-m MST) performance in young elite soccer players. A parallel two-groups, longitudinal design was used. Fifteen players were divided to either SEM (8 repetitions of 20-s all-out sprint interspersed with 40 s of recovery) or SEP (8 repetitions of 20-s all-out bout interspersed with 120 s of recovery) training group. SEM improved the ability to tolerate fatigue and maintained the performance development during the 5-m MST while SEP increased only the 1^st sprint showing, simultaneously, an increased fatigue index and performance decrement. The selection of which training regimes to prioritize should be based on the players' characteristics and individual game requirements Abbreviations: SEP: Speed Endurance Production; SEM: Speed Endurance Maintenance; PRE: Baseline; POST: End of experimental protocol; 5-m MST: 5-meters Multiple Shuttle Run Test; TD: Total Distance; FI: Fatigue Index; MSTdec: Percentage Decrement Score; BMI: Body Mass Index.

Effects of Plyometric and Directional Training on Speed and Jump Performance in Elite Youth Soccer Players

Beato, M, Bianchi, M, Coratella, G, Merlini, M, and Drust, B. Effects of plyometric and directional training on speed and jump performance in elite youth soccer players. J Strength Cond Res 32(2): 289-296, 2018-Soccer players perform approximately 1,350 activities (every 4-6 seconds), such as accelerations/decelerations and changes of direction (CODs) during matches. It is well established that COD and plyometric training have a positive impact on fitness parameters in football players. This study analyzed the effect of a complex COD and plyometric protocol (CODJ-G) compared with an isolated COD protocol (COD-G) training on elite football players. A randomized pre-post parallel group trial was used in this study. Twenty-one youth players were enrolled in this study (mean ± SD; age 17 ± 0.8 years, mass 70.1 ± 6.4 kg, and height 177.4 ± 6.2 cm). Players were randomized into 2 different groups: CODJ-G (n = 11) and COD-G (n = 10), training frequency of 2 times a week more than 6 weeks. Sprint 10, 30, and 40 m, long jump, triple hop jump, and 505 COD test were considered. Exercise-induced within-group changes in performance for both CODJ-G and COD-G: long jump (effect size [ES] = 0.32 and ES = 0.26, respectively) and sprint 10 m (ES = -0.51 and ES = -0.22, respectively), after 6 weeks of training. Moreover, CODJ-G reported substantially better results (between-group changes) in long jump test (ES = 0.32). In conclusion, this study showed that short-term protocols (CODJ-G and COD-G) are important and able to give meaningful improvements on power and speed parameters in a specific soccer population. CODJ-G showed a larger effect in sprint and jump parameters compared with COD-G after the training protocol. This study offers important implications for designing COD and jumps training in elite soccer.

Correlation between quadriceps and hamstrings inter-limb strength asymmetry with change of direction and sprint in U21 elite soccer-players

The aim of this study was to investigate the relationship between in quadriceps and hamstrings inter-limb strength asymmetry and change of direction, sprinting and jumping abilities in U21 elite soccer players. Twenty-seven soccer players volunteered for this study. Isokinetic quadriceps and hamstrings peak torque was measured at high and low angular velocities, both in concentric and eccentric modalities. Performance in agility T-test, 20 + 20 m shuttle-test, 10 m and 30 m sprint, squat jump (SJ) and counter-movement jump (CMJ), were measured. Overall, time on agility T-test and 20 + 20 m shuttle-test was moderately and positively correlated with the quadriceps and hamstrings inter-limb eccentric peak torque asymmetry, both at high and low angular velocities. In addition, time on 10 m and 30 m sprints was moderately and positively correlated with the hamstrings inter-limb high-velocity concentric peak torque asymmetry. SJ and CMJ showed trivial to small correlations with hamstrings and quadriceps inter-limb peak torque asymmetry. The present results provide further information insight the role of lower-limb muscle strength balance in COD, sprinting and jumping performance.

Reliability of internal and external load parameters in recreational football (soccer) for health

There is limited research focussed around the analysis of internal and external load parameters during football health programmes. The aim of this study was to assess the reliability of internal and external load parameters in this activity. Thrity subjects were enrolled (mean ± SDs; age = 43 ± 3 years, weight = 84 ± 14 kg, height = 176 ± 7 cm, BMI = 27.1 ± 3, VO₂max = 40.7 ± 3.4 ml^.kg^.min^-1). The football matches (five a-side) took place on an artificial grass outdoor field (pitch size of 36 × 18.5 m). Participants completed the match (60 min) and replicated the same match a week later. The analysis took into account several parameters: heart rate (HR), total distance (TD), high speed running (HSR), number of accelerations (>2 m^.s^-2) and metabolic power (MP). We found a good score of reliability in several parameters: TD (ICC = 0.66), accelerations (ICC = 0.62), mean HR (ICC = 0.82), HSR (ICC = 0.77) and MP (ICC = 0.66). The results reported in this study revealed good scores of absolute reliability and small/trivial effect size.