Effects of Strength Training Associated With Whole-Body Vibration Training on Running Economy and Vertical Stiffness.

Running economy (RE) is defined as the energy cost to maintain a submaximal running velocity and seems to be affected by individual's neuromuscular characteristics, such as stiffness level. Both resistance training (RT) and whole-body vibration training added to RT (WBV + RT) have been shown to influence those characteristics. Thus, it is conceivable that RT and WBV + RT could also affect RE. The objective of this study was to investigate if a 6-week training period of RT and WBV + RT influences RE and vertical stiffness (VS). Fifteen recreational runners were divided into RT or WBV + RT groups. Running economy, VS, and lower-limb maximum dynamic strength (1 repetition maximum [1RM] half-squat) were assessed before and after the 6-week training period. There was a main time effect for 1RM, but no other statistically significant difference was observed. Neither conventional RT nor RT performed on a WBV platform improved VS and RE in recreational long distance runners. It is possible that movement velocity was rather low, and utilization of stretch-shortening cycle might have been compromised, impairing any expected improvement in RE.

Influence of strength training background on postactivation potentiation response.

The aim of this study was to evaluate the influence of the subjects' level of maximal dynamic strength and training background on postactivation potentiation (PAP). A group of 23 subjects, composed of power track-and-field athletes (PT = 8), bodybuilders (BB = 7), and physically active subjects (PA = 8), participated in the study. Maximal dynamic strength (1 repetition maximum test) was assessed in the leg press exercise for subjects' characterization. Their countermovement vertical jump (CMJ) performance was assessed before and after 2 different conditioning activity (CA) protocols (1 or 3 maximum voluntary isometric contractions [MVICs] of 5-second duration in the leg press exercise) or after control (no CA), performed on separate days. No significant differences among groups were found for CMJ height or take-off velocity after any of the CA protocols (p ≤ 0.05). However, individual analysis showed that some subjects increased performance in response to the CA, despite their previous training history. We concluded that subjects' level of maximal dynamic strength and training background have no influence on PAP manifestation. Our data suggest that coaches should individually identify the athletes that are PAP responders before introducing MVICs as part of their warm-up routines.

Effect of eccentric exercise velocity on akt/mtor/p70(s6k) signaling in human skeletal muscle.

It has been suggested that muscle tension plays a major role in the activation of intracellular pathways for skeletal muscle hypertrophy via an increase in mechano growth factor (MGF) and other downstream targets. Eccentric exercise (EE) imposes a greater amount of tension on the active muscle. In particular, high-speed EE seems to exert an additional effect on muscle tension and, thus, on muscle hypertrophy. However, little is known about the effect of EE velocity on hypertrophy signaling. This study investigated the effect of acute EE-velocity manipulation on the Akt/mTORCI/p70(S6K) hypertrophy pathway. Twenty subjects were assigned to either a slow (20°·s(-1); ES) or fast EE (210°·s(-1); EF) group. Biopsies were taken from vastus lateralis at baseline (B), immediately after (T1), and 2 h after (T2) the completion of 5 sets of 8 repetitions of eccentric knee extensions. Akt, mTOR, and p70(S6K) total protein were similar between groups, and did not change postintervention. Further, Akt and p70(S6K) protein phosphorylation were higher at T2 than at B for ES and EF. MGF messenger RNA was similar between groups, and only significantly higher at T2 than at B in ES. The acute manipulation of EE velocity does not seem to differently influence intracellular hypertrophy signaling through the Akt/mTORCI/p70S6K pathway.

Intermittent exercise as a conditioning activity to induce postactivation potentiation.

Postactivation potentiation (PAP) is defined as a short-term increase in voluntary muscle activation following a previous conditioning activity (CA). Controversy about PAP is mostly attributed to the characteristics of the CA and the training status of the subjects. While some studies have found that PAP can be induced by series of 5-10 second maximal voluntary isometric contractions or near maximal dynamic contractions (e.g., 3-5 repetition maximum), others have failed to do so. On the other hand, some studies suggest that intermittent contractions can also induce PAP. However, even though PAP was observed, its duration was not taken into account, leaving ground for further investigations. The purpose of this study was threefold: (a) to verify if PAP can progressively enhance performance of voluntary actions throughout a set of intermittent contractions; (b) to verify PAP duration when induced by an intermittent contractions protocol; and (c) to verify if PAP effects were reproducible in different sessions when induced by intermittent contractions. Ten physically active men, not engaged in strength training, underwent 5 randomized experimental sessions, during which they performed a set of 10 unilateral knee extensions (KE) (1 every 30 seconds) at 60 degrees x s(-1) in an isokinetic dynamometer. Peak torque was evaluated over the 10 unilateral KE and at the randomized intervals of 4, 6, 8, 10, and 12 minutes post CA. Peak torque was potentiated 1.3 (+/-0.79) N x m per unilateral KE, and the potentiation effect persisted for 12 minutes after the last contraction. These findings were reproduced in all 5 experimental sessions. Thus, intermittent conditioning activities seem to be an effective way to produce PAP. However, these activities should be tested in a more real world situation to verify the applicability as a warm-up routine.

Efeitos do treinamento com plataformas vibratórias / Effects of training with vibratorys platforms

Esta revisão de literatura teve como objetivo dispor informações sobre as adaptações produzidas pelo treinamento de vibração quando realizado através de plataformas vibratórias. Em consulta a base de dados Medline encontramos 25 artigos originais sobre o tema. Após uma análise criteriosa desses estudos constatamos que grande parte deles foi realizada com delineamento experimental inapropriado. Sendo assim, 13 artigos foram excluídos e, esta revisão foi baseada em 12 estudos. Em relação aos efeitos agudos e crônicos da vibração em jovens encontramos resultados controversos, o que nos permite afirmar que ainda não existem dados suficientes na literatura que comprovem a eficiência dessa estratégia nessas condições. Por outro lado, em se tratando da população idosa, parece que o treinamento de vibração pode melhorar o equilíbrio, a agilidade e a marcha. Além disso, o treinamento de vibração pode ser tão eficiente quanto o treinamento de força convencional na melhora da força e da potência. No entanto, essas conclusões ainda não podem ser consideradas definitivas, uma vez que esses resultados foram encontrados em apenas dois estudos.

The purpose of this review was to investigate the adaptations of vibration training using vibration platforms. Literature search was performed using the Medline database (25 original studies). However, the analysis of the experimental designs revealed that only 12 studies met the criteria to be included in our review. Regarding the acute and chronic effects of vibration training in young population, results were controversial and its efficiency has yet to be proven under such conditions. On the other hand, in the elderly, it seems that vibration training can improve balance, agility and gait. Moreover, vibration training seems to be as efficient as conventional strength training in the improvement of strength and power for this population. However, further evidence is still needed in order to establish such conclusions, once these results had been found in two studies only.

Potencialização: a influência da contração muscular prévia no desempenho da força rápida / Potentiation: the influence of previous muscle contraction on speed-strength performance

A ampliação da força decorrente de uma atividade prévia é conhecida como potencialização. Neste estudo investigouse a potencialização da força rápida, avaliada por meio dosalto vertical (SV), causada por atividades do ciclo alongamento-encurtamento e ações isométricas máximas. Dezoito jovens do sexo masculino foram divididos em trêsgrupos: Salto em Profundidade (SP,n=6), Isometria Máxima(IM,n=6) e Controle (CON,n=6). O grupo SP foi submetido a 4 x 5 saltos (40 cm). O grupo IM realizou 3 contrações isométricas máximas de 5 segundos de duração. O desempenho no SV foi avaliado no aparelho Ergojump, pré e nos intervalos de 5, 10 e 15 minutos pós-tratamento. ANOVA demonstrou não haver diferenças significantes no SV entre os grupos e intervalos de tempo. O grupo SP sofreuuma queda média no desempenho de 1,6 cm (41,2 ± 2,6 cm pré para 39,6 ± 2,6 cm pós). O grupo IM também teve queda de 1,4cm (41,6 ± 4,6 cm pré para 40,2 ± 4,5 cm pós) e o grupoCON diminui 1,0 cm (40,8 ± 4,6 cm pré para 39,8 ± 4,6 cmpós). Assim, não foi possível esclarecer qual tipo de ação muscular é mais eficiente em desencadear a potencialização. O nível de experiência dos sujeitos em treinamento de forçapode ter sido um importante fator na ausência da potencialização.

Intensification of strength due to a previous activity is known as potentiation. In this study we investigated quick strength potentiation, evaluated through vertical jump (VJ) performance, caused by activities of the stretch-shortening cycle and maximum isometric contractions...