RESUMO
BACKGROUND: Although the studies of barefoot running have intensified, it is still missing longitudinal work analyzing the effects of barefoot running on the phases of plantar support. The objective of this research was to analyze the modifications undergone by the Total Foot Contact (TFC) phase and its Flat Foot Phase (FFP) in subjects beginning the practice of barefoot running, in its acute and chronic effects. METHODS: A total of 28 subjects were divided into the Barefoot Group (BFGr) (n = 16) and the Shod Group (SHGr) (n = 12), evaluated before (Baseline) and after running for 20 min at 3.05 m·s-1 (Post 20 min Running), and at the end of a running training protocol with an 8-week long progressive volume (Post-8-week Training). The dynamic plantar support was measured with a baropodoscope. The duration of TFC (ms), the moment at which the FFP occurred, the maximum surface of TFC (MSTFC) (cm2), the FFP surface (SFFP) (cm2), the peak pressure of TFC (PP°TFC) (kg·cm-2), and the peak pressure of FFP (PP°FFP) (kg·cm-2) were recorded. The 3 × 2 ANOVA analysis was made to determine the effects and interactions that the condition produced (Shod/Barefoot), and the time factor (Baseline/Post 20 min Running/Post-8-week Training). RESULTS: The condition factor caused more significant effects than the time factor in all the variables. Duration of TFC in BFGr showed significant differences between the Baseline and Post-8-week Training (p = 0.000) and between Post-20-min Running and Post-8-week Training (p = 0.000), with an increasing trend. In the moment at which the FFP occurred a significant increase (p = 0.029) increase was found in Post-20 min Running (48.5%) compared to the Baseline (42.9%). In MSTFC, BFGr showed in Post-8-week Training values significantly higher than the Baseline (p = 0.000) and than Post-20-min Running (p = 0.000). SHGr presented a significant difference between the Baseline and Post-8-week Training (p = 0.040). SFFP in BFGr modified its values with an increasing trend (p = 0.000). PP°TFC in BFGr showed a significant decrease (p = 0.003) in Post-8-week Training (1.9 kg·cm-2) compared to the Baseline (2.4 kg·cm-2). In PP°FFP significant decreases were recorded in BFGr and between Post-8-week Training and Baseline (p = 0.000), and Post-8-week Training and Post 20 min Running (p = 0.035). CONCLUSIONS: The adaptation took place after the 8-week training. The adaptations to running barefoot were characterized by causing an increase of the foot's plantar support in TFC and in FFP, as well as a decrease of the plantar pressure peak in both phases. Also, there is an increased duration of the TFC and FFP, which may be related to an acquired strategy to attenuate the impacts of the ground's reaction forces.
RESUMO
La carrera descalza ha sido ampliamente estudiada últimamente, pero poco se sabe de cambios anatómicos que produce en el pie. El objetivo de este estudio fue determinar estos cambios producidos de forma aguda y a largo plazo en sujetos que entrenan a pie descalzo. 29 sujetos divididos en dos grupos: Barefoot (BFGr) (n=17) y Shod (SGr) (n=12), realizaron un protocolo de efecto agudo consistente en correr durante 20 min sobre treadmill a 3.1 m/s y un protocolo de entrenamiento de 8 semanas de carrera de resistencia con aumento progresivo de volumen. BFGr realizó todas las sesiones a pie descalzo. Al finalizar cada protocolo se midió Foot Length (FL), Forefoot Width (FW), Hindfoot Width (HW), Navicular Height (NH), Arch Index (AI) y Maximum Surface (MS). Se efectuó ANOVA 3x2 para comprobar los efectos que el tiempo y la condición de calzado produjo. La condición de calzado produjo efectos significativos sobre todas las variables (FL: p=0.000, η2p=0.997; FW: p=0.000, η2p=0,997; HW: p=0.000, η2p= 0,994; NH: p=0.000, η2p=0.953; AI: p=0.000, η2p=0.898; MS: p=0.000, η2p=0.983) y el factor tiempo sobre AI (p=0.012, η2p=0.152) y MS (p=0.000, η2p=0.259). Hubo interacción significativa Tiempo x Condición en FW (p=0.036, η2p= 0.116) y NH (p=0.019, η2p= 0.143). MS aumentó luego del protocolo de efecto agudo (p=0.000) y a largo plazo (p=0.001) en BFGr. El porcentaje de sujetos con pie normal aumentó en BFGr y con pie plano aumentó en SGr. El entrenamiento de carrera a pie descalzo produce efectos, principalmente luego de un período de adaptación de 8 semanas, tendientes a un aumento armónico en la superficie de apoyo plantar con tendencia a una disminución relativa del área del mediopié, lo cual se tradujo en una disminución de sujetos con arco plantar de tipología plana.
Barefoot running has been studied extensively recently, but little is known of the anatomical changes that take place in the foot. The objective of this study was to determine the acute and chronic changes that are produced in subjects who train barefoot. 29 subjects divided into two groups, Barefoot (BFGr) (n=17) and Shod (SGr) (n=12), followed an acute effect protocol which consisted in running during 20 min on a treadmill at 3.1 m/s, and an eight-week long chronic effect protocol covering eight weeks of resistance running with progressively increasing volume. BFGr did all the sessions barefoot. At the end of each protocol Foot Length (FL), Forefoot Width (FW), Hindfoot Width (HW), Navicular Height (NH), Arch Index (AI), and Maximum Surface (MS) were measured. ANOVA 3x2 was run to verify the effects caused by time and the shod condition produced. Shod/ Unshod factor caused significant effects on all the variables (FL: p=0.000, η2p=0.997; FW: p=0.000, η2p=0,997; HW: p=0.000, η2p= 0,994; NH: p=0.000, η2p=0.953; AI: p=0.000, η2p=0.898; MS: p=0.000, η2p=0.983), and the time factor on AI (p=0.012, η2p=0.152) and MS (p=0.000, η2p=0.259). There was a significant Time x Condition interaction in FW (p=0.036, η2p=0.116) and NH (p=0.019, η2p= 0.143). MS increased after the acute (p=0.000) and the chronic (p=0.001) protocols in the BFGr. The percentage of subjects with normal feet increased in the BFGr and that with flat feet increased in SGr. Barefoot running training causes effects, mainly after an adaptation period of eight weeks, tending to a harmonic surface increase on the support plantar area, with a relative decrease of the midfoot area, which meant a decrease of subjects with plantar arch of flat type.
Assuntos
Humanos , Masculino , Feminino , Adulto Jovem , Pressão , Corrida/fisiologia , Pé/anatomia & histologia , Sapatos , Fatores de Tempo , Adaptação Fisiológica , Antropometria , Reprodutibilidade dos Testes , Análise de VariânciaRESUMO
PURPOSE: Countermovement jump (CMJ) and maximum running speed over a distance of 20 m were evaluated for examination of the concurrent fatigue and postactivation potentiation (PAP) in endurance athletes after an incremental field running test. METHODS: Twenty-two endurance athletes performed two attempts of CMJ on a force plate and maximum running speed test before and following the Université de Montréal Track Test (UMTT). RESULTS: The results showed an improvement in CMJ height (3.6%) after UMTT that correlated with the increment in peak power (3.4%), with a concurrent peak force loss (-10.8%) that correlated with peak power enhancement. The athletes maintained their 20 m sprint performance after exhaustion. Cluster analysis reinforced the association between CMJ and peak power increments in responders with a reported correlation between peak power and sprint performance increments (r = .623; P = .041); nonresponders showed an impairment of peak force, vertical stiffness, and a higher vertical displacement of the center of mass during the countermovement that correlated with lactate concentration (r = -0.717; P = .02). CONCLUSIONS: It can be suggested that PAP could counteract the peak force loss after exhaustion, allowing the enhancement of CMJ performance and the maintenance of sprint ability in endurance athletes after the UMTT. From these results, the evaluation of CMJ after incremental running tests for the assessment of muscular adaptations in endurance athletes can be recommended.