Juan A. Párraga-Montilla

Changes in balance ability, power output, and stretch-shortening cycle utilisation after two high-intensity intermittent training protocols in endurance runners

Purpose This study aimed to describe the acute effects of 2 different high-intensity intermittent trainings (HIITs) on postural control, countermovement jump (CMJ), squat jump (SJ), and stretch-shortening cycle (SSC) utilisation, and to compare the changes induced by both protocols in those variables in endurance runners. Methods Eighteen recreationally trained endurance runners participated in this study and were tested on 2 occasions: 10 runs of 400 m with 90 s recovery between running bouts (10 × 400 m), and 40 runs of 100 m with 30 s recovery between runs (40 × 100 m). Heart rate was monitored during both HIITs; blood lactate accumulation and rate of perceived exertion were recorded after both protocols. Vertical jump ability (CMJ and SJ) and SSC together with postural control were also controlled during both HIITs. Results Repeated measures analysis revealed a significant improvement in CMJ and SJ during 10 × 400 m (p < 0.05), whilst no significant changes were observed during 40 × 100 m. Indexes related to SSC did not experience significant changes during any of the protocols. As for postural control, no significant changes were observed in the 40 × 100 m protocol, whilst significant impairments were observed during the 10 × 400 m protocol (p < 0.05). Conclusion A protocol with a higher number of shorter runs (40 × 100 m) induced different changes in those neuromuscular parameters than those with fewer and longer runs (10 × 400 m). Whereas the 40 × 100 m protocol did not cause any significant changes in vertical jump ability, postural control or SSC utilisation, the 10 × 400 m protocol impaired postural control and caused improvements in vertical jumping tests.

Foot strike pattern in preschool children during running: sex and shod–unshod differences

Abstract Purpose: This study aims to determine the foot strike patterns (FSPs) and neutral support (no inversion [INV]/eversion [EVE] and no foot rotation) in preschool children, as well as to determine the influence of shod/unshod conditions and sex. Methods: A total of 1356 children aged 3–6 years (673 boys and 683 girls) participated in this study. A sagittal and frontal-plane video (240 Hz) was recorded using a high-speed camcorder to record the following variables: rearfoot strike (RFS), midfoot strike (MFS), forefoot strike (FFS), inversion/ eversion (INV/EVE) and foot rotation on initial contact. Results: There were no between-sex significant differences in both shod and unshod conditions in RFS. In the unshod condition, there was a significant reduction (p < 0.001) of RFS prevalence in both boys (shod condition = 44.2% vs. 34.7% unshod condition) and girls (shod condition = 48.5% vs. 36.1% unshod condition). As for neutral support, there were no between-sex differences in both shod and unshod conditions or in the shod–unshod comparison. Conclusion: In preschool children, no between-sex differences were found in relation to prevalence of RFS and neutral support (no INV/EVE). Shod running alters FSP of running barefoot, producing a significant increase of RFS prevalence.

Physiological and Neuromuscular Response to a Simulated Sprint-Distance Triathlon: Effect of Age Differences and Ability Level.

Abstract García-Pinillos, F, Cámara-Pérez, JC, González-Fernández, FT, Párraga-Montilla, JA, Muñoz-Jiménez, M, and Latorre-Román, PÁ. Physiological and neuromuscular response to a simulated sprint-distance triathlon: effect of age differences and ability level. J Strength Cond Res 30(4): 1077–1084, 2016—This study aimed to describe the acute impact of a simulated sprint-distance triathlon at physiological and neuromuscular levels and to determine whether age and athletic performance influenced the response in triathletes. Nineteen triathletes performed a sprint-distance triathlon under simulated conditions. Cardiovascular response was monitored during the race. Rate of perceived exertion along with muscular performance parameters (countermovement jump [CMJ], squat jump [SJ], and handgrip strength test [HS]) were tested at pre- and posttest and during every transition, while a 20-m sprint test (S20m) was performed before and after the race. Blood lactate was recorded postrace. A repeated measures analysis of variance showed that the neuromuscular response—in terms of CMJ, SJ, and HS—was unchanged (p ≥ 0.05), while S20m performance was impaired at posttest (p < 0.001). A linear regression analysis showed that &Dgr;CMJ predicted the overall race time (R 2 = 0.226; p = 0.046). In addition, 2 cluster analyses (k-means) were performed by grouping according to athletic performance and age. Between-group comparison showed no significant differences in the impact of the race at either the physiological or the neuromuscular level. The results showed that muscular performance parameters were not impaired throughout the race despite high levels of fatigue reported. However, despite maintaining initial levels of muscle force after the race, the fatigue-induced changes in S20m were significant, which could reinforce the need to train sprint ability in endurance athletes. Finally, despite the differences in ability level or in age, the acute physiological and neuromuscular responses to a simulated sprint-distance triathlon were similar.

Minimum time required for assessing step variability during running at submaximal velocities

This study aimed to determine the minimum time required for assessing spatiotemporal variability during continuous running at different submaximal velocities and, thereby, the number of steps required. Nineteen trained endurance runners performed an incremental running protocol, with a 3-min recording period at 10, 12, 14 and 16 km/h. Spatiotemporal parameters (contact and flight times, step length and step frequency) were measured using the OptoGait system and step variability was considered for each parameter, in terms of within-participants standard deviation (SD) and coefficient of variation (CV%). Step variability was considered over six different durations at every velocity tested: 0-10 s, 0-20 s, 0-30 s, 0-60 s, 0-120 s and 0-180 s. The repeated measures ANOVA revealed no significant differences in the magnitude of the four spatiotemporal parameters between the recording intervals at each running velocity tested (p ≥ 0.05, ICC > 0.90). The post-hoc analysis confirmed no significant differences in step variability (SD and CV% of each spatiotemporal parameter at any velocity tested) between measurements. The Bland-Altman limits of agreement method showed that longer recording intervals yield smaller systematic bias, random errors, and narrower limits of agreement, regardless of running velocity. The results suggest that the duration of the recording period required to estimate spatiotemporal variability plays an important role in the accuracy of the measurement, regardless of running velocity (10-16 km/h).

Differences in Sprint Mechanical Force-Velocity Profile Between Trained Soccer and Futsal Players

PURPOSE To compare the sprint mechanical force-velocity (F-V) profile between soccer and futsal players. A secondary aim was, within each sport, to study the differences in sprint mechanical F-V profile between sexes and players of different levels. METHODS A total of 102 soccer players (63 men) and 77 futsal players (49 men) who were competing from the elite to amateur levels in the Spanish league participated in this investigation. The testing procedure consisted of 3 unloaded maximal 40-m sprints. The velocity-time data recorded by a radar device were used to calculate the variables of the sprint acceleration F-V profile (maximal theoretical force [F0], maximal theoretical velocity [V0], maximal power [Pmax], decrease in the ratio of horizontal to resultant force [DRF], and maximal ratio of horizontal to resultant force [RFpeak]). RESULTS Futsal players showed a higher F0 than soccer players (effect size [ES] range: 0.11-0.74), while V0 (ES range: -0.48 to -1.15) and DRF (ES range: -0.75 to -1.45) was higher for soccer players. No significant differences were observed between soccer and futsal players for Pmax (ES range: -0.43 to 0.19) and RFpeak (ES range: -0.49 to 0.30). Men and high-level players presented an overall enhanced F-V profile compared with women and their lower-level counterparts, respectively. CONCLUSIONS The higher F0 and lower V0 of futsal players could be caused by the games specific demands (larger number of accelerations but over shorter distances than in soccer). These results show that the sprint mechanical F-V profile is able to distinguish between soccer and futsal players.

LOAD THAT MAXIMIZES POWER OUTPUT IN COUNTERMOVEMENT JUMP

Introduccion: Uno de los principales problemas que los preparadores fisicos enfrentan es el hecho de como objetivamente cuantificar y monitorear la carga de entrenamiento real utilizada por los atletas con el fin de optimizar el rendimiento. Es bien conocido que el rendimiento en actividades deportivas de caracter explosivo esta determinado en gran medida por la potencia mecanica. Objetivo: Este estudio analizo la altura en la que se genera la maxima potencia y la carga correspondiente con la que se consigue, en un grupo de deportistas de atletismo del sexo masculino entrenados en el test de salto con contramovimiento (SCM) con cargas progresivas (SCMc). Metodos: Cincuenta atletas hombres velocistas y saltadores de nivel nacional realizaron el test de SCM, incrementando las cargas hasta la altura de 16 cm. La carga relativa con la que se alcanzo la maxima potencia (Pmax) se determino utilizando una plataforma de fuerza sincronizada con un codificador lineal y estimando la potencia mediante la potencia pico, la potencia media y el tiempo de vuelo en el SCM. Resultados: La carga con la que la potencia maxima no mas existia fue en la altura de 19,9 ± 2,35, con referencia al 99,1 ± 1% de la potencia maxima. La carga con la que se alcanza la potencia maxima en todos los casos ha sido con aquella con la que el atleta salta una altura de aproximadamente 20 cm. Conclusion: Estos resultados destacan la importancia de considerar la altura alcanzada en SCM con carga extra en lugar de la potencia, puesto que la potencia maxima siempre se alcanza a la misma altura. Es muy recomendable priorizar el empleo de la altura alcanzada en el test SCMc, ya que parece ser un indicador valido del potencial neuromuscular real de un individuo proporcionando una informacion valida para entrenadores y preparadores fisicos para evaluar la condicion de rendimiento de nuestros atletas y cuantificar y monitorear las cargas de entrenamiento, solamente midiendo la altura del salto en el ejercicio de SCMc.

Kinematic alterations after two high-intensity intermittent training protocols in endurance runners

Purpose This study aimed to evaluate running kinematic characteristics during the early and late stages of 2 high-intensity intermittent training (HIIT) protocols with similar external load but different average running pace, as well as to compare the fatigue-induced changes during both HIIT protocols at a kinematic level. Methods Eighteen endurance runners were tested on a track on 2 occasions: 10 runs of 400 m with 90–120 s recovery between running bouts (10 × 400 m), and 40 runs of 100 m with 25–30 s recovery between running bouts (40 × 100 m). Heart rate was monitored during both protocols; blood lactate accumulation and rate of perceived exertion were recorded after both exercises. A high-speed camera was used to measure sagittal-plane kinematics at the first and last runs during both HIIT protocols. The dependent variables were spatial-temporal parameters (step length and contact and flight time), joint angles during support (relative angles of the hip, knee, and ankle), and foot strike pattern. Results High levels of exhaustion were reached by the athletes during both workouts (blood lactate accumulation >12 mmol/L, rate of perceived exertion >15; peak heart rate (HRpeak) > 176 bpm). A within-protocol paired t test (first vs. last run) revealed no significant changes (p ≥ 0.05) in kinematic variables during any of the HIIT sessions. A between-protocol comparison with the first run of each protocol revealed the effect of running speed on kinematics: +2.44 km/h during the 40 × 100 m: shorter contact and flight time (p  ≤  0.01) and longer step length (p = 0.001); greater hip flexion (p = 0.031) and ankle extension (p = 0.001) at initial contact; smaller knee and ankle flexion (p < 0.001) at midstance; and greater hip extension at toe-off (p < 0.001). Conclusion HIIT sessions including runs for 15–90 s and performed at intensity above the velocity associated with maximal oxygen uptake did not consistently perturb the running kinematics of trained endurance runners.