Isokinetic profiling of elite youth footballers: informing selection of a practicable and efficacious isokinetic screening test.

Isokinetic dynamometry represents the clinical gold standard for strength assessment but testing lack consensus. Elite youth male football players (n = 28) completed 20 repetitions (analysed as four epochs) of eccentric knee flexor (eccKF) and concentric knee extensor (conKE) trials at 60, 180 and 270°âˆ™s-1, quantifying peak torque (PT) and functional range (FR). There was a significant (P < 0.001) main effect for fatigue and angular velocity in conKE PT; eccKF PT was not significant across epoch (P = 0.35) and velocity (P = 0.12) and a velocity x epoch interaction highlighted more repetitions were required to elicit fatigue as velocity increased. FR decreased with fatigue (P < 0.001) and velocity (P < 0.01) in conKE and eccKF, indicative of a narrowing of the strength curve. Clinical interpretation advocates an isokinetic test comprising at least 15 reps at a velocity ≥ 180°âˆ™s-1 and analysis beyond the peak of the strength curve (PT) to inform clinical reasoning and individualized exercise prescription.

Within- and between-day loading response to ballet choreography.

Overuse pathologies are prevalent in ballet injury. Ten amateur ballet dancers (age: 23.20 ± 3.08 years) completed a progressive 5-stage choreographed routine on two consecutive days. Tri-axial accelerometers positioned at C7 and the dominant and non-dominant lower-limb were used to calculate accumulated PlayerLoadTM (PLTOTAL) and uni-axial contributions of the anterior-posterior (PLAP), medial-lateral (PLML), and vertical (PLV) planes. PLTOTAL increased significantly (p = 0.001) as a function of exercise duration within-trial, however there was no significant change between trials (p = 0.18). PLTOTAL at C7 was significantly (p = 0.001) lower than both lower-limbs, with no bilateral asymmetry evident (p = 0.97). Planar contributions to PLTOTAL were significantly greater in PLV than PLAP and PLML (p = 0.001). PlayerLoadTM demonstrated within-trial sensitivity to the progressive routine, however no residual fatigue effect was observed between trials. The results of this study suggest that accelerometers have efficacy in athlete monitoring and injury screening protocols, however unit placement should be considered for practical interpretation.

Isokinetic ankle eversion and inversion strength profiling of female ballet dancers.

Ankle injuries are highly prevalent in ballet, with strength highlighted as a primary risk factor. To profile ankle strength, fourteen female ballet dancers (age: 19.29 ± 1.59 years) completed an isokinetic testing protocol comprising concentric eversion (CONEV) and inversion (CONINV), and, eccentric inversion (ECCINV) trials at four angular velocities (30° · s-1, 60° · s-1, 90° · s-1, 120° · s-1) for both the dominant and non-dominant limb. In addition to Peak Torque (PT) and the corresponding Dynamic Control Ratios (DCRs), angle-specific derivatives of strength (AST) and Functional Range (FR) were calculated. There was no evidence of any significant bilateral strength asymmetry (p = 0.90) across all metrics, and no significant interactions with limb and contraction mode or velocity. A significant main effect for contraction mode (p = 0.001) highlighted greater ECCINV strength - which was maintained with increasing isokinetic velocity - in contrast to reductions in CONEV and CONINV strength. Specifically, dancers are ECCINV dominant at angular velocities greater than 60° · s-1, which is likely to be characteristic of most functional tasks. The lack of bilateral asymmetry may be attributed to dance training interventions that facilitate bilateral development, but ipsilateral mode and velocity-specific asymmetries have implications for injury risk and the training needs of female ballet dancers.

The Influence of Soccer Playing Surface on the Loading Response to Ankle (P)Rehabilitation Exercises.

CONTEXT: Contemporary synthetic playing surfaces have been associated with an increased risk of ankle injury in the various types of football. Triaxial accelerometers facilitate in vivo assessment of planar mechanical loading on the player. OBJECTIVE: To quantify the influence of playing surface on the PlayerLoad elicited during footwork and plyometric drills focused on the mechanism of ankle injury. DESIGN: Repeated-measures, field-based design. SETTING: Regulation soccer pitches. PARTICIPANTS: A total of 15 amateur soccer players (22.1 [2.4] y), injury free with ≥6 years competitive experience. INTERVENTIONS: Each player completed a test battery comprising 3 footwork drills (anterior, lateral, and diagonal) and 4 plyometric drills (anterior hop, inversion hop, eversion hop, and diagonal hop) on natural turf (NT), third-generation artificial turf (3G), and AstroTurf. Global positioning system sensors were located at C7 and the mid-tibia of each leg to measure triaxial acceleration (100 Hz). MAIN OUTCOME MEASURES: PlayerLoad in each axial plane was calculated for each drill on each surface and at each global positioning system location. RESULTS: Analysis of variance revealed a significant main effect for sensor location in all drills, with PlayerLoad higher at mid-tibia than at C7 in all movement planes. AstroTurf elicited significantly higher PlayerLoad in the mediolateral and anteroposterior planes, with typically no difference between NT and 3G. In isolated inversion and eversion hopping trials, the 3G surface also elicited lower PlayerLoad than NT. CONCLUSIONS: PlayerLoad magnitude was sensitive to unit placement, advocating measurement with greater anatomical relevance when using microelectromechanical systems technology to monitor training or rehabilitation load. AstroTurf elicited higher PlayerLoad across all planes and drills and should be avoided for rehabilitative purposes, whereas 3G elicited a similar mechanical response to NT.

The Influence of Playing Surface on the Loading Response to Soccer-Specific Activity.

CONTEXT: The influence of playing surface on injury risk in soccer is contentious, and contemporary technologies permit an in vivo assessment of mechanical loading on the player. OBJECTIVE: To quantify the influence of playing surface on the PlayerLoad elicited during soccer-specific activity. DESIGN: Repeated measures, field-based design. SETTING: Regulation soccer pitches. PARTICIPANTS: Fifteen amateur soccer players (22.1 [2.4] y), injury free with ≥6 years competitive experience. INTERVENTIONS: Each player completed randomized order trials of a soccer-specific field test on natural turf, astroturf, and third-generation artificial turf. GPS units were located at C7 and the mid-tibia of each leg to measure triaxial acceleration (100 Hz). MAIN OUTCOME MEASURES: Total accumulated PlayerLoad in each movement plane was calculated for each trial. Ratings of perceived exertion and visual analog scales assessing lower-limb muscle soreness were measured as markers of fatigue. RESULTS: Analysis of variance revealed no significant main effect for playing surface on total PlayerLoad (P = .55), distance covered (P = .75), or postexercise measures of ratings of perceived exertion (P = .98) and visual analog scales (P = .61). There was a significant main effect for GPS location (P < .001), with lower total loading elicited at C7 than mid-tibia (P < .001), but with no difference between limbs (P = .70). There was no unit placement × surface interaction (P = .98). There was also a significant main effect for GPS location on the relative planar contributions to loading (P < .001). Relative planar contributions to loading in the anterioposterior:mediolateral:vertical planes was 25:27:48 at C7 and 34:32:34 at mid-tibia. CONCLUSIONS: PlayerLoad metrics suggest that playing surface does not influence mechanical loading during soccer-specific activity (not including tackling). Clinical reasoning should consider that PlayerLoad magnitude and axial contributions were sensitive to unit placement, highlighting opportunities in the objective monitoring of load during rehabilitation.

Physical Response to a Simulated Period of Soccer-Specific Fixture Congestion.

Page, RM, Marrin, K, Brogden, CM, and Greig, M. Physical response to a simulated period of soccer-specific fixture congestion. J Strength Cond Res 33(4): 1075-1085, 2019-The aim of this study was to assess the physiological, perceptual, and mechanical measures associated with the completion of a simulated period of short-term soccer-specific fixture congestion. Ten male semiprofessional soccer players completed 3 trials of a treadmill-based match simulation, with 48 hours interspersing each trial. A repeated measures general linear model identified significantly (p = 0.02) lower knee flexor peak torque (PT) recorded at 300°·s in the second (141.27 ± 28.51 N·m) and third trials (139.12 ± 26.23 N·m) when compared with the first trial (154.17 ± 35.25 N·m). Similarly, muscle soreness (MS) and PT data recorded at 60°·s were significantly (p ≤ 0.05) different in the third trial (MS = 42 ± 25 a.u; PT60 = 131.10 ± 35.38 N·m) when compared with the first trial (MS = 29 ± 29 a.u; PT60 = 145.61 ± 42.86 N·m). Significant (p = 0.003) differences were also observed for mean electromyography (EMGmean) of bicep femoris between the third trial (T0-15 = 126.36 ± 15.57 µV; T75-90 = 52.18 ± 17.19 µV) and corresponding time points in the first trial (T0-15 = 98.20 ± 23.49 µV; T75-90 = 99.97 ± 39.81 µV). Cumulative increases in perceived exertion, heart rate, oxygen consumption, blood lactate concentrations, EMGmean, and PlayerLoad (PL) were recorded across each trial. Muscle soreness and PT were also significantly different after trial. There were, however, no significant main effects or interactions for the salivary immunoglobulin A and the medial-lateral PL metrics. These data suggest a biomechanical and muscular emphasis with residual fatigue, with implications for injury risk and the development of recovery strategies.

The Influence of Circadian Variation on Etiological Markers of Ankle Injury.

Context: Clinical and functional assessments are performed regularly in sporting environments to screen for performance deficits and injury risk. Circadian rhythms have been demonstrated to affect human performance; however, the influence of time of day on a battery of multiple ankle injury risk factors has yet to be established within athletic populations. Objectives: To investigate the influence of circadian variation on a battery of tests used to screen for ankle etiological risk factors. Design: Randomized crossover design. Setting: University laboratory. Participants: A total of 33 semiprofessional soccer players (age = 24.9 [4.4] y; height = 1.77 [0.17] m; body mass = 75.47 [7.98] kg) completed 3 randomized experimental trials (07∶00, 12∶00, and 19∶00 h). Main Outcome Measures: Trials involved the completion of a standardized test battery comprising the Biodex Stability System, Star Excursion Balance Test, isokinetic inversion: eversion ratio, joint position sense, and a drop-landing inversion cutting maneuver. Results: Repeated measures analysis of variance revealed significantly (P < .05) lower values for all Biodex Stability System indicia; overall stability index (1.10 [0.31] a.u.), anterior-posterior (0.76 [0.21] a.u.), and mediolateral (0.68 [0.23]) at 12∶00 hours when compared with 07∶00 hours (1.30 [0.45] a.u.; 0.96 [0.26] a.u.; 0.82 [0.40] a.u.), respectively. However, no significant (P ≥ .05) main effects for time of day were reported for any other test. Conclusions: Circadian influence on ankle etiological risk factors was task dependent, with measures of proprioception, strength, and Star Excursion Balance Test displaying no circadian variation, indicating no association between time of day and markers of injury risk. However, the Biodex Stability System displayed improved performance at midday, indicating postural stability tasks requiring unanticipated movements to display a time of day effect and potential increased injury risk. Consequently, time of testing for this task should be standardized to ensure correct interpretations of assessments and/or interventions.

Biomechanical and Physiological Response to a Contemporary Soccer Match-Play Simulation.

The intermittent activity profile of soccer match play increases the complexity of the physical demands. Laboratory models of soccer match play have value in controlled intervention studies, developed around manipulations of the activity profile to elicit a desired physiological or biomechanical response. Contemporary notational analyses suggest a profile comprising clusters of repeat sprint efforts, with implications for both biomechanical and physiological load. Eighteen male soccer players completed a 90-minute treadmill protocol based on clusters of repeat sprint efforts. Each 15-minute bout of exercise was quantified for uniaxial (medial-lateral [PLML], anterior-posterior [PLAP], and vertical [PLV]) and triaxial PlayerLoad (PLTotal). The relative contributions of the uniaxial PlayerLoad vectors (PLML%, PLAP%, and PLV%) were also examined. In addition to rating of perceived exertion, the physiological response comprised heart rate, blood lactate concentration, and both peak and average oxygen consumption. Triaxial PlayerLoad increased (p = 0.02) with exercise duration (T0-15 = 206.26 ± 14.37 a.u. and T45-60 = 214.51 ± 14.97 a.u.) and remained elevated throughout the second half. This fatigue effect was evident in both the PLML and PLAP movement planes. The mean relative contributions of PLV%:PLAP%:PLML% were consistent at ∼48:28:23. The physiological response was comparable with match play, and a similar magnitude of increase at ∼5% was observed in physiological parameters. Changes in PlayerLoad might reflect a change in movement quality with fatigue, with implications for both performance and injury risk, reflecting observations of match play. The high frequency of speed change elicits a 23% contribution from mediolateral load, negating the criticism of treadmill protocols as "linear."

Effect of Kinesiology Tape on Tri-Axial Accelerometry During the Dance Aerobic Fitness Test.

OBJECTIVES: Kinesiology tape (KT) is thought to provide greater mechanical support during physical activity, however, there is a paucity of research investigating its application in dance. The study aimed to determine whether KT reduces PlayerLoad (PL) during the Dance Aerobic Fitness Test (DAFT) in addition to examining the relative sensitivity of accelerometer site locations.
Methods: University-level dancers (N = 11; age 18 ± 0.45 years, height 168.17 ± 12.25 cm, body mass 57.50 ± 9.91 kg) participated in two trials of the DAFT protocol in two conditions: no tape (NT) and kinesiology tape (KT). Global positioning systems (GPS) and accelerometer units were attached onto the seventh vertebra (C7) at the mid-scapula region and lower limb (LL) located at the midgastrocnemius of the dominant leg calculating measurements of triaxial (PLTotal) and uniaxial measures (anteroposterior [PLAP], mediolateral [PLML], and vertical [PLV]) measures of PlayerLoad during the DAFT.
Results: No significant main effect was observed for the taping condition in all measures of PlayerLoad (P > 0.10). A significant main effect (p < 0.01) was observed for unit location and time, with greater loading at the LL compared to C7 and during each consequent stage of the DAFT. No significant (p > 0.52) location*taping, nor location*taping*time (p > 0.36) interactions were observed for all variables measured.
Conclusions: Kinesiology tape does not reduce loading patterns in healthy dancers during a fatigue protocol. However, triaxial accelerometers provide adequate sensitivity when detecting changes in loading, suggesting the LL may be deemed as a more relevant method of monitoring training load in dancers.

Use of Triaxial Accelerometry During the Dance Aerobic Fitness Test: Considerations for Unit Positioning and Implications for Injury Risk and Performance.

Injury incidence in dance is high, in large part due to the frequency of repetitive and complex movements that require the lower limb to absorb and utilize extreme forces. The aim of this study was to quantify the biomechanical demands of the Dance Aerobic Fitness Test (DAFT) via triaxial accelerometry and utilize it to compare loading at the cervical spine and distal aspect of the lower limb. University dancers (N = 26; age: 20.0 ± 1.5 years; height: 1.61 ± 0.08 m; body mass: 58.40 ± 6.20 kg) completed two trials (one familiarization and one experimental) of the DAFT, consisting of five incremental levels of dance performance. Micromechanical electrical systems (MEMS) accelerometry was used to calculate total accumulated PlayerLoad (PLTotal) and it's uniaxial (anteroposterior [PLAP], mediolateral [PLML], and vertical [PLV]) components for each level. MEMS units were positioned at cervical vertebra 7 (C7) and the center of gastrocnemius (LL). There was a significant main effect for each level, with loading increasing in relation to exercise duration. There was also a significant main effect for anatomical placement, with higher PLTotal (C7 = 41.05 ± 7.31 au; LL = 132.58 ± 35.70), PLAP (C7 = 12.96 ± 2.89 au; LL = 47.16 ± 13.18 au), and PLML (C7 = 10.68 ± 2.15; LL = 46.29 ± 12.62 au) at LL when compared to C7, with the converse relationship for PLV (LL = 20.05 ± 3.41 au; C7 = 44.89 ± 11.22 au). Significant interactions were displayed for all PL metrics. It is concluded that triaxial PlayerLoad was sensitive enough to detect increased loading associated with increases in exercise intensity, while lower limb accelerometer placement detected higher loading in all planes. The specificity in anatomical placement has practical implications, with lower limb accelerometry recommended to assess movement strategies in that location.

The biomechanical and physiological response to repeated soccer-specific simulations interspersed by 48 or 72 hours recovery.

PURPOSE: To assess the residual fatigue response associated with the completion of two successive soccer-specific exercise protocols (SSEP). METHODS: Twenty male soccer players were pair-matched before completing SSEPs, interspersed by either 48 or 72 h. Outcome variables were measured every 15 min, and comprised uni-axial measures of PlayerLoad, mean (HR) and peak heart rate (HRpeak), blood lactate concentration, mean and peak (V˙O2peak) oxygen consumption, and rating of perceived exertion (RPE). RESULTS: No significant (P > 0.05) group interactions were identified for any outcome variables. Uni-axial (and total) PlayerLoad exhibited a significant (P < 0.05) main effect for time, with the exception of the relative contribution of medial lateral PlayerLoad™. Total PlayerLoad during the final 15 min (222.23 ± 15.16 a.u) was significantly higher than all other time points. All other outcome variables also exhibited a significant main effect for time, with HR, HRpeak and V˙O2peak also exhibiting significantly higher values in the first trial. There was also a significant (P = 0.003) trial*time interaction for RPE. CONCLUSIONS: With equivalence at baseline, there was no difference in the fatigue response associated with two SSEPs interspersed by either 48 or 72 h recovery. The current study has implications for the design and micro management of training and competition schedules.