Evaluating the Effects of Consecutive Phases of Plyometric Jump Training on Athletic Performance in Male Soccer Players: The Effect of Training Frequency and Volume Manipulations.

ABSTRACT: Moran, J, Vali, N, Tallent, J, Howe, L, Clemente, FM, Chaabene, H, and Ramirez-Campillo, R. Evaluating the effects of consecutive phases of plyometric jump training on athletic performance in male soccer players: The effect of training frequency and volume manipulations. J Strength Cond Res 38(6): 1082-1089, 2024-This 14-week, 2-phase study aimed to determine the relative effects of 1 day or 2 days of volume-matched plyometric training on athletic performance (10- and 40-m sprints, change of direction [COD], and vertical jump [VJ]) in male soccer players (phase 1). The objective of phase 2 was to determine the relative effects of higher- and lower-volume plyometric training protocols in maintaining any previously attained increases in athletic performance from phase 1. A randomized parallel-group trial design was utilized. In phase 1, subjects ( n = 24; mean age: 19.5 ± 1.2 years; mean height: 179.7 ± 7.1 cm; mean weight: 69.8 ± 6.9 kg) were randomly allocated to 1 of 2 groups to receive either 1 day or 2 days of volume- and intensity-matched plyometric training for a 7-week period. For the second 7-week period (phase 2), half of each group was randomized into either a lower-volume or higher-volume plyometric training group. In phase 1, both the 1-day group and the 2-day group attained comparably significant ( p < 0.001) increases in performance in all fitness tests ranging from effect sizes (ESs) ( d ) of 0.4 (95% confidence interval: 0.11 to 0.70) for 10-m sprint to 1.51 (0.42-2.60) for VJ. There were no significant differences between the performance increases in the 2 groups. In phase 2, neither group increased or decreased performance, maintaining all previously attained increases with only trivial ESs observed (-0.02 [-0.58 to 0.53] to 0.11 [-0.38 to 0.61]). Increases in 10- and 40-m sprint speed, COD speed, and VJ height can be achieved and maintained with as little as 1 plyometric training session per week. Sessions can include 120 jumps to induce increases of the reported magnitudes, with 60 jumps to maintain these increases thereafter, in male soccer players.

Slow-Speed Compared With Fast-Speed Eccentric Muscle Actions Are Detrimental to Jump Performance in Elite Soccer Players In-Season.

PURPOSE: To examine the effect of fast- versus slow-speed eccentric-muscle-action resistance training on lower-body strength, vertical jump height, sprint speed, and change-of-direction performance in elite soccer players during a competitive season. METHODS: Twenty-two elite soccer players, from a single team, were randomly assigned to groups that undertook either 1- (fast speed) or 4-second (slow speed) eccentric resistance training during the in-season period. A 5-week program was conducted during an elite top-division European League soccer season. Performance measures including predicted 1-repetition-maximum back squat, countermovement jump, 20-m sprint, and change of direction were tested before and after the intervention period. Total match and training running distance and muscle soreness were also recorded during each week of the intervention. RESULTS: An analysis of covariance showed significant group effects (P = .01) for countermovement jump with a greater jump height in the 1-second fast-speed group postintervention (95% CI, 1.1-6.9 cm). Despite an overall increase in 1-repetition maximum pretraining to posttraining (95% CI, 10.0-15.3 kg, effect size 0.69), there were no significant differences (P > .05) between groups after the intervention. Similarly, there were no differences between groups for change of direction, 20-m sprint, or muscle soreness. CONCLUSION: Faster eccentric muscle actions may be superior for increasing movements in elite soccer players in-season.

Improved Ankle Mobility After a 4-Week Training Program Affects Landing Mechanics: A Randomized Controlled Trial.

ABSTRACT: Howe, LP, Bampouras, TM, North, JS, and Waldron, M. Improved ankle mobility after a 4-week training program affects landing mechanics: a randomized controlled trial. J Strength Cond Res 36(7): 1875-1883, 2022-This study examined the effects of a 4-week ankle mobility intervention on landing mechanics. Twenty subjects with restricted ankle dorsiflexion range of motion (DF ROM) were allocated to either a strength training only (n = 9) or a strength training and ankle mobility program (n = 11). Subjects performed a weight-bearing lunge test and bilateral drop-landings before and after the intervention. Normalized peak vertical ground reaction force (vGRF), time to peak vGRF, and loading rate were calculated, alongside sagittal-plane initial contact angles, peak angles, and sagittal-plane joint displacement for the ankle, knee, and hip. Frontal-plane projection angles were also calculated. After the intervention, only the strength and mobility group improved ankle DF ROM (mean difference = 4.1°, effect size [ES] = 1.00, p = 0.002). A one-way analysis of covariance found group effects for ankle joint angle at initial contact (p = 0.045), ankle (p < 0.001) and hip joint angle at peak flexion (p = 0.041), and sagittal-plane ankle (p < 0.001) and hip joint displacement (p = 0.024) during bilateral drop-landings. Post hoc analysis revealed that the strength and mobility group landed with greater ankle plantarflexion at initial contact (mean difference = 1.4 ± 2.0°, ES = 0.46) and ankle dorsiflexion at peak flexion (mean difference = 6.3 ± 2.9°, ES = 0.74) after the intervention, resulting in a greater ankle joint displacement (mean difference = 7.7 ± 4.0°, ES = 1.00). However, the strength training only group landed with increased peak hip flexion (mean difference = 14.4 ± 11.0°, ES = 0.70) and hip joint displacement (mean difference = 8.0 ± 6.6°, ES = 0.44) during post-testing. The findings suggest that changes in landing strategies following the performance of a strength training program are specific to whether restrictions in ankle mobility are considered as part of the intervention.

Restrictions in Ankle Dorsiflexion Range of Motion Alter Landing Kinematics But Not Movement Strategy When Fatigued.

CONTEXT: Ankle dorsiflexion range of motion (DF ROM) has been associated with a number of kinematic and kinetic variables associated with landing performance that increase injury risk. However, whether exercise-induced fatigue exacerbates compensatory strategies has not yet been established. OBJECTIVES: (1) Explore differences in landing performance between individuals with restricted and normal ankle DF ROM and (2) identify the effect of fatigue on compensations in landing strategies for individuals with restricted and normal ankle DF ROM. DESIGN: Cross-sectional. SETTING: University research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twelve recreational athletes with restricted ankle DF ROM (restricted group) and 12 recreational athletes with normal ankle DF ROM (normal group). MAIN OUTCOME MEASURE(S): The participants performed 5 bilateral drop-landings, before and following a fatiguing protocol. Normalized peak vertical ground reaction force, time to peak vertical ground reaction force, and loading rate were calculated, alongside sagittal plane initial contact angles, peak angles, and joint displacement for the ankle, knee, and hip. Frontal plane projection angles were also calculated. RESULTS: At the baseline, the restricted group landed with significantly less knee flexion (P = .005, effect size [ES] = 1.27) at initial contact and reduced peak ankle dorsiflexion (P < .001, ES = 1.67), knee flexion (P < .001, ES = 2.18), and hip-flexion (P = .033, ES = 0.93) angles. Sagittal plane joint displacement was also significantly less for the restricted group for the ankle (P < .001, ES = 1.78), knee (P < .001, ES = 1.78), and hip (P = .028, ES = 0.96) joints. CONCLUSIONS: These findings suggest that individuals with restricted ankle DF ROM should adopt different landing strategies than those with normal ankle DF ROM. This is exacerbated when fatigued, although the functional consequences of fatigue on landing mechanics in individuals with ankle DF ROM restriction are unclear.

Physiological Responses to Linear and Nonlinear Soccer-specific Match Simulations and Their Effects on Lower-Limb Muscle Fatigue.

Uddin, N, Jeffries, O, Read, P, Howe, L, Patterson, S, and Waldron, M. Physiological responses to linear and nonlinear soccer-specific match simulations and their effects on lower-limb muscle fatigue. J Strength Cond Res 34(11): 3232-3240, 2020-The aims of this study were to: (a) investigate the effects of linear and nonlinear soccer simulations on lower-limb muscle function and physiological responses and (b) evaluate the relationship between match-running demands and changes in lower-limb muscle function. In a repeated-measures cross-over design, 8 participants completed either a linear or nonlinear adapted Loughborough Intermittent Shuttle Test (LIST) on 2 occasions. The movement of players was tracked with a global positioning system, while lower-limb muscle function tests and physiological measurements were performed before and every 15 minutes during the simulation. There were no differences in distance covered, yet high-speed running (p = 0.007), accelerations (p = 0.008), and decelerations (p = 0.015) were higher in the linear LIST. Mean heart rate (p = 0.001) and ratings of perceived exertion (p = 0.013) were higher in the nonlinear LIST. Peak landing forces (p = 0.017) and jump height (p = 0.001) were reduced between baseline and 90 minutes but were not different between conditions. Changes in peak landing forces from baseline to half-time (r = -0.57, n = 16, p = 0.022) and full-time (r = -0.58, n = 16, p = 0.019) were related to high-speed running. Hamstring force was unaffected by time (p = 0.448) but was reduced in the linear LIST (p = 0.044). Protocols posing different external and internal demands elicited similar levels of fatigue across simulations. Hamstring function was not an effective indicator of fatigue, but our results highlight the greater demands placed on this muscle group when higher-speed running is performed.

WITHIN-SESSION RELIABILITY FOR INTER-LIMB ASYMMETRIES IN ANKLE DORSIFLEXION RANGE OF MOTION MEASURED DURING THE WEIGHT-BEARING LUNGE TEST.

BACKGROUND: The identification of asymmetrical inter-limb ankle dorsiflexion range of motion (DF ROM) has the potential to influence the course of treatment during the rehabilitation process, with limitations in ankle DF ROM potentially increasing injury risk. However, reliability for methods to identify ankle DF ROM asymmetries remain under described in the literature. PURPOSE: To determine the reliability of the trigonometric calculation method for measuring ankle DF ROM during the weight-bearing lunge test (WBLT) for both a single limb and the symmetry values. The secondary purpose was to establish values of ankle DF ROM asymmetry and identify the influence of leg dominance on ankle DF ROM. STUDY DESIGN: Cross-sectional study. METHODS: Ankle DF ROM was measured bilaterally in 50 healthy and recreationally active participants (28 men, 22 women, age = 22 ± 4 years, height = 172.8 ± 10.8 cm, body mass 71.5 ± 15.1 kg), using the trigonometric measurement method during the WBLT. Each ankle was measured twice in a single testing session to establish within-session reliability. RESULTS: Values are presented for asymmetries in DF ROM. No differences were identified between the dominant and non-dominant limb (p = 0.862). Within-session reliability for measuring a single limb was classified as 'good' (ICC = 0.98) with a minimal detectable change value of 1.7 °. For measuring ankle DF ROM asymmetry, reliability was established as 'good' (ICC = 0.85) and a minimal detectable change value of 2.1 ° was determined. CONCLUSIONS: Although symmetry in ankle DF ROM may not be assumed, the magnitude of asymmetry may be less than previously reported in a population of recreationally active individuals. Discrepancies between previous research and the findings of the present study may have been impacted by differences in measurement methods. Furthermore, clinicians should be aware that the error associated with measures of asymmetry for ankle DF ROM during the WBLT is greater than that of a single limb. LEVEL OF EVIDENCE: 2b.

Restricted Unilateral Ankle Dorsiflexion Movement Increases Interlimb Vertical Force Asymmetries in Bilateral Bodyweight Squatting.

Crowe, MA, Bampouras, TM, Small, K, and Howe, LP. Restricted unilateral ankle dorsiflexion movement increases interlimb vertical force asymmetries in bilateral bodyweight squatting. J Strength Cond Res 34(2): 332-336, 2020-The purpose of this study was to investigate the effect of unilateral restrictions in ankle-dorsiflexion range of motion (DF-ROM) on interlimb vertical ground reaction force (vGRF) asymmetries. Twenty healthy and physically active volunteers (age 23 ± 3 years; height 1.72 ± 0.1 m; mass 74.9 ± 20.3 kg) performed 3 barefoot bodyweight squats (control condition) and with a 10° custom-built forefoot wedge under the right foot to artificially imitate ankle DF-ROM restriction (wedge condition). Force data were used to calculate the mean asymmetry index score for the upper descent phase, lower descent phase, lower ascent phase, and upper ascent phase during the bilateral squat. Significant differences were found for comparisons for each phase between conditions, with effect sizes ranging between 0.7 and 1.1. Asymmetry index scores indicated that for all phases, the unrestricted limb in the wedge condition produced greater vGRF. Therefore, interlimb differences in ankle DF-ROM can cause interlimb asymmetries in vGRF during bilateral squatting. As such, athletes with asymmetrical squat mechanics should be screened for interlimb differences in ankle DF-ROM to ascertain whether it is a contributing factor.

Ankle dorsiflexion range of motion is associated with kinematic but not kinetic variables related to bilateral drop-landing performance at various drop heights.

Limited evidence is available concerning ankle dorsiflexion range of motion (DF ROM) and its relationship with landing performance from varying drop heights. The aim of this investigation was to determine the relationship between ankle DF ROM and both kinetic and kinematic variables measured during bilateral drop-landings from 50%, 100% and 150% of countermovement jump height. Thirty-nine participants were measured for their ankle DF ROM using the weight-bearing lunge test, after which five bilateral drop-landings were performed from 50%, 100% and 150% of maximal countermovement jump height. Normalized peak vertical ground reaction force (vGRF), time to peak vGRF and loading rate was calculated for analysis, alongside sagittal-plane initial contact angles, peak angles and joint displacement for the hip, knee and ankle. Frontal-plane projection angles were also calculated. Ankle DF ROM was not related to normalized peak vGRF, time to peak vGRF or loading rate (P > 0.05), regardless of the drop height. However, at drop heights of 100% and 150% of countermovement jump height, there were numerous significant (P < 0.05) moderate to large correlations between ankle DF ROM and initial contact angles (r = -0.34 to -0.40) and peak angles (r = -0.42 to -0.52) for the knee and ankle joint. Knee joint displacement (r = 0.39-0.47) and frontal-plane projection angle (r = 0.37-0.40) had a positive relationship with ankle DF ROM, which was consistent across all drop heights. Ankle DF ROM influences coordination strategies that allow for the management of vGRF during bilateral drop-landings, with alterations in alignment for the knee and ankle joints at both initial contact and peak angles.

Effects of Small-Sided Game Variation on Changes in Hamstring Strength.

Madison, G, Patterson, SD, Read, P, Howe, L, and Waldron, M. Effects of small-sided game variation on changes in hamstring strength. J Strength Cond Res 33(3): 839-845, 2019-Small-sided games (SSGs) are commonly used by soccer practitioners to condition players. This form of exercise can result in fatigue, potentially exposing the muscle to injury risk. The purpose of this study was to determine the effects of SSG variations on hamstring torque in semiprofessional soccer players. In a counterbalanced cross-over design, 10 male semiprofessional soccer players took part in both small relative area (3 vs. 3; 300 m) and large relative area (4 vs. 4; 1000 m) SSGs. The games comprised 6 × 4-minute bouts, with 90-second recovery. Both movement and heart rate responses were monitored by global positioning systems (GPS) and hamstring isometric torque was measured pre-training and post-training using a NordBord. There were differences (p < 0.05) between the small and large relative area games for peak hamstring force decrement (5.78 N and -13.62 N, respectively) and mean hamstring force decrement at 90° (11.11 N and -4.78 N, respectively). The number of accelerations was related to (r = 0.46, p = 0.039) reduced hamstring peak torque at 90°. In conclusion, larger relative area SSGs elicited the greatest internal and external loads, resulting in decrements in hamstring force. The number of accelerations performed in the session increases the likelihood of hamstring fatigue and can be controlled with the relative pitch area.

Effects of Strength Training on Postpubertal Adolescent Distance Runners.

PURPOSE: Strength training activities have consistently been shown to improve running economy (RE) and neuromuscular characteristics, such as force-producing ability and maximal speed, in adult distance runners. However, the effects on adolescent (<18 yr) runners remains elusive. This randomized control trial aimed to examine the effect of strength training on several important physiological and neuromuscular qualities associated with distance running performance. METHODS: Participants (n = 25, 13 female, 17.2 ± 1.2 yr) were paired according to their sex and RE and randomly assigned to a 10-wk strength training group (STG) or a control group who continued their regular training. The STG performed twice weekly sessions of plyometric, sprint, and resistance training in addition to their normal running. Outcome measures included body mass, maximal oxygen uptake (V˙O2max), speed at V˙O2max, RE (quantified as energy cost), speed at fixed blood lactate concentrations, 20-m sprint, and maximal voluntary contraction during an isometric quarter-squat. RESULTS: Eighteen participants (STG: n = 9, 16.1 ± 1.1 yr; control group: n = 9, 17.6 ± 1.2 yr) completed the study. The STG displayed small improvements (3.2%-3.7%; effect size (ES), 0.31-0.51) in RE that were inferred as "possibly beneficial" for an average of three submaximal speeds. Trivial or small changes were observed for body composition variables, V˙O2max and speed at V˙O2max; however, the training period provided likely benefits to speed at fixed blood lactate concentrations in both groups. Strength training elicited a very likely benefit and a possible benefit to sprint time (ES, 0.32) and maximal voluntary contraction (ES, 0.86), respectively. CONCLUSIONS: Ten weeks of strength training added to the program of a postpubertal distance runner was highly likely to improve maximal speed and enhances RE by a small extent, without deleterious effects on body composition or other aerobic parameters.

The acute effects of ankle mobilisations on lower extremity joint kinematics.

INTRODUCTION: Previous investigations have identified compensatory movement strategies (CMS) within the lower extremity or lumbopelvic complex during closed chain exercises may be associated with a loss of ankle dorsiflexion range of motion (ROM). The aim of this study was to investigate the acute effects of ankle mobilisations on proximal joint kinematics during a movement task that demands a high amount of ankle dorsiflexion ROM. METHODS: Eight healthy males (mean (SD) age 25 (4) years) demonstrating side-to-side asymmetry during the weight-bearing lunge test (WBLT) and CMS during the single-leg step-down exercise were accepted for this study. Participants completed five repetitions of a single-leg step-down, both before and after an ankle mobilisation intervention aimed at improving joint athrokinematics. A Vicon motion capture system recorded 3D joint and segment kinematics of the ankle, knee, hip and pelvis. A paired samples t-test was used to identify significant changes of lower extremity joint kinematics during the single-leg step-down, before and after mobilisation. RESULTS: Following the mobilisation intervention, statistically significant gains in ankle dorsiflexion ROM were identified during the WBLT [mean difference 2.425 (0.9377) centimeters, t = -7.315, p < 0.01]. No evidence was found of altered joint kinematics during the single-leg step-down. CONCLUSION: These findings indicate that increases in ankle dorsiflexion ROM do not automatically integrate into functional movement tasks.

The effects of acute branched-chain amino acid supplementation on recovery from a single bout of hypertrophy exercise in resistance-trained athletes.

This study investigated the effects of acute branched-chain amino acid (BCAA) supplementation on recovery from exercise-induced muscle damage among experienced resistance-trained athletes. In a double-blind matched-pairs design, 16 resistance-trained participants, routinely performing hypertrophy training, were randomly assigned to a BCAA (n = 8) or placebo (n = 8) group. The BCAAs were administered at a dosage of 0.087 g/kg body mass, with a 2:1:1 ratio of leucine, isoleucine, and valine. The participants performed 6 sets of 10 full-squats at 70% 1-repetition maximum to induce muscle damage. All participants were diet-controlled across the study. Creatine kinase, peak isometric knee-extensor force, perceived muscle soreness, and countermovement jump (CMJ) height were measured immediately before (baseline) and at 1 h, 24 h, and 48 h postexercise. There were large to very large time effects for all measurements between baseline and 24-48 h. Between-group comparisons, expressed as a percentage of baseline, revealed differences in isometric strength at 24-h (placebo ∼87% vs. BCAA ∼92%; moderate, likely), CMJ at 24 h (placebo ∼93% vs. BCAA ∼96%; small, likely), and muscle soreness at both 24 h (placebo ∼685% vs. BCAA ∼531%; small, likely) and 48 h (placebo ∼468% vs. BCAA ∼350%; small, likely). Acute supplementation of BCAAs (0.087 g/kg) increased the rate of recovery in isometric strength, CMJ height, and perceived muscle soreness compared with placebo after a hypertrophy-based training session among diet-controlled, resistance-trained athletes. These findings question the need for longer BCAA loading phases and highlight the importance of dietary control in studies of this type.