Effects of resistance training at different intensities of load on cross-education of muscle strength.

The objectives of this study were to 1) compare the extent of cross-transfer of muscle strength of high- versus low-load unilateral resistance training performed with external pacing of the movement (URTEP) and 2) compare the time course of the 2 approaches. Fifty subjects were randomized to 1 of the following 3 groups: G80 [2 sets at 80% and 2 sets at 40% of 1 repetition maximum (1RM), 1 concentric second and 3 eccentric seconds controlled by a metronome]; G40 (4 sets at 40% of 1RM, 1 s and 3 s controlled by a metronome); or control group. At week 1, the G80 increased the elbow flexion 1RM (P < 0.05) in contralateral arm. At week 4, both G80 and G40 increased the elbow flexion 1RM (P < 0.05) in contralateral arm. However, a greater 1RM gain was observed in the G80 than in the G40 (P < 0.05). Thus, although higher-load URTEP seems to enhance the cross-education effect when compared with lower-load URTEP, the cross-education of dynamic strength can be achieved in the 2 approaches after 4 weeks. Many patients would benefit from cross-education of muscle strength through URPEP, even those who are unable to exercise with high loads and in short periods of immobilization. Novelty: Unilateral resistance training promotes cross-education of dynamic muscle strength. However, higher-load resistance training enhances the effects of cross-education of muscle strength.

Efeitos de diferentes protocolos de pré-ativação antagonista contralateral sobre o desempenho de repetições múltiplas / Effects of diferent protocols of pre-activation antagonist contralateral on the performance of multiple repetitions

: A educação cruzada corresponde a uma adaptação neural em que ocorre melhoria de desempenho do membro não treinado após um período de prática unilateral do membro contralateral. A co-ativação da musculatura antagonista também corresponde a um fenômeno neural que pode limitar a produção de força e estratégias de como a pré-ativação procuram melhorar o desempenho. A combinação de ambos pode resultar em aumento de desempenho n o treinamento de força. O objetivo do estudo foi investigar os efeitos de diferentes protocolos de pré-ativação antagonista contralateral sobre o desempenho de repetições múltiplas. Quinze mulheres treinadas realizaram a pré-ativação da musculatura antagonista contralateral de forma unilateral em quatro protocolos distintos: no protocolo preferido e não preferido flexor-extensor era realizado a CF do membro preferido ou não e em seguida a CE do membro contralateral. No protocolo p referido e não preferido extensor-flexor era realizado a CE do membro preferido ou não preferido e em seguida a CF do membro contralateral. Eram realizadas t rês séries usando cargas máximas de dez repetições com intervalo de dois minutos. Em relação à CE, verificou-se volume de treinamento (VTT) significativamente maior no protocolo flexor-extensor (23,5s). Quanto a CF, verificou-se resultado significativamente maior no protocolo extensor-flexor (10,6%; 22,2%). Em relação ao TST, foi significativamente maior no protocolo extensor-flexor para ambos os membros (23,2s.; 23,9s.). Não houve diferença significativa para percepção subjetiva de esforço. A pré-ativação antagonista contralateral permitiu um aumento no VTT e no TST em ambos os protocolos na CE e CF sendo um a possível alternativa para tal objetivo....(AU)

: The cross education corresponds a neural adaptation in which the performance improvement of the utrained limb o ccurs aft er a period of unilateral practice by the contralateral limb. The co-activation of the antagonistic also corresponds a neural phenomenon t hat can limit the muscle strength and strategies like as pre-activation seek to improve performance. The combination of both can result in increased resistance training performance. The aim of the study was to investigate the effects of diferente protoco ls o s p re- activation antago nist contralateral on the performance of repetitions. Fifteen trained women performed pre-activation of thecontralateral antagonist musculature unilateral in four diferente protocols: in the preferred and not preferred flexor-extensor protocol, the LC of the preferred or non-preferred lim was performed and then the LE of the contralaterals limb. In the preferred and not preferred extensor-flexor protocol, the LE of preferredor non-preferred limb was performed and then the LC of the contralateral limb. Three sets were performed usin g m ax imum lo ads of tem repetitions with and interval of two minutes. In the LE, there was a significantly higher training v o lume (VTT) in th e flex or -extensor protocol (14,9%; 16,9%). About time under tension (TST), LE a significant increase in TST was identified in the non-preferred m em ber of the flexor extensor protocol (23,5s.). As for LG, there was a significantly higher result in the extensor-flexor protocol (10,6%; 2 2,2%). In relation to TST, it was significantly higher in the extensor-flexor protocol for both members (23,2s; 2 3,9s). There was no significant difference for subjective perception of effort. The controlateral antagonista pre-activation provided na increase in the VTT and the TST in both protocols in LE and LC, being a possible alternative for this objective....(AU)

Contralateral effects of eccentric resistance training on immobilized arm.

This study compared the effects of contralateral eccentric-only (ECC) and concentric-/eccentric-coupled resistance training (CON-ECC) of the elbow flexors on immobilized arm. Thirty healthy participants (18-34 y) were randomly allocated to immobilization only (CTRL; n = 10), immobilization and ECC (n = 10), or immobilization and CON-ECC group (n = 10). The non-dominant arms of all participants were immobilized (8 h·day-1 ) for 4 weeks, during which ECC and CON-ECC were performed by the dominant (non-immobilized) arm 3 times a week (3-6 sets of 10 repetitions per session) with an 80%-120% and 60%-90% of one concentric repetition maximum (1-RM) load, respectively, matching the total training volume. Arm circumference, 1-RM and maximal voluntary isometric contraction (MVIC) strength, biceps brachii surface electromyogram amplitude (sEMGRMS ), rate of force development (RFD), and joint position sense (JPS) were measured for both arms before and after immobilization. CTRL showed decreases (P < .05) in MVIC (-21.7%), sEMGRMS (-35.2%), RFD (-26.0%), 1-RM (-14.4%), JPS (-87.4%), and arm circumference (-5.1%) of the immobilized arm. These deficits were attenuated or eliminated by ECC and CON-ECC, with greater effect sizes for ECC than CON-ECC in MVIC (0.29: +12.1%, vs -0.18: -0.1%) and sEMGRMS (0.31:17.5% vs -0.15: -5.9%). For the trained arm, ECC showed greater effect size for MVIC than CON-ECC (0.47 vs 0.29), and increased arm circumference (+2.9%), sEMGRMS (+77.9%), and RDF (+31.8%) greater (P < .05) than CON-ECC (+0.6%, +15.1%, and + 15.8%, respectively). The eccentric-only resistance training of the contralateral arm was more effective to counteract the negative immobilization effects than the concentric-eccentric training.

Cross-education: evidências, mecanismos, implicações para a reabilitação e aplicações práticas / Cross-education: evidences, mechanisms, implications for practical rehabilitation and application

O treinamento de força gera adaptações no sistema neuromuscular. Nesta perspectiva, o "cross-education" surge como um fenômeno caracterizado por adaptações neurais e pelo aumento da capacidade de geração de força voluntária do membro oposto ao não treinado, que ocorre como resultado do treinamento de força unilateral. Sendo assim, o presente estudo tem como objetivo fornecer informações sobre o fenômeno cross-education, apresentando suas evidências, mecanismos, implicações para a reabilitação e aplicações práticas. Neste trabalho, foi realizado um levantamento bibliográfico sobre o cross-education nas bases de dados disponíveis na Internet. As fontes de informações eletrônicas foram acessadas nas bases de dados do Pubmed, periódicos da CAPES e Lilacs. Para a busca de informações foram utilizadas as seguintes expressões: muscle strength, unilateral exercise, cross-education. A pesquisa inclui trabalhos publicados entre os anos de 1997 a 2015. Os estudos mostraram que o cross-education é caracterizado por adaptações neurais assim como por alterações no SNC que possibilitam a transferência de força para o membro contralateral, imobilizado ou não imobilizado. Conforme os resultados, este fenômeno parece ser importante para a reabilitação, à medida que ao realizarmos o treinamento de um membro isolado, podemos obter repercussões no membro contralateral. No entanto, mais pesquisas são necessárias para investigar as evidências e os mecanismos relacionados ao cross-education, assim como seus efeitos crônicos. Consequentemente, estudos complementares sobre esse fenômeno serão importantes para analisar a reabilitação de indivíduos com alguma lesão dos membros e as suas diversas aplicações práticas.

Strength Training generates adaptations in neuromuscular system. Within this perspective "cross-education" emerges as a phenomenon featured by neural adaptations and by the increase of the capacity to generate volunteer strength of the opposite member to the non-trained one that occurs as a result of the unilateral strength training. Hence, the present study has as its objective provide information about the cross-education phenomenon, presenting its evidences, mechanisms, implications for practical rehabilitation and applications. In this paper a bibliographic survey about the cross-education has been made with data available on the internet. The electronic sources of information were accessed in the data base from Pubmed, from CAPES journals and Lilacs. For the search of information the following expressions were used: muscle strength, unilateral exercise, cross-education. The research includes papers published between the years of 1997 to 2015. Studies showed that cross-education is featured by neural adaptations so as by alterations at the SNC that enable the transference of strength to the contralateral limb, fixed or not fixed. According to its results, this phenomenon seems to be essential to rehabilitation, because as we train the static member we can obtain repercussions in the subordinate member. However, more research is necessary to investigate evidences and the mechanisms related to cross-education, as well as its chronic effects. As a result, complementary studies about this phenomenon will be important to analyze the rehabilitation of people with any member injuries and its many practical applications.

Unilateral plantar flexors static-stretching effects on ipsilateral and contralateral jump measures.

The aim of this study was to evaluate the acute effects of unilateral ankle plantar flexors static-stretching (SS) on the passive range of movement (ROM) of the stretched limb, surface electromyography (sEMG) and single-leg bounce drop jump (SBDJ) performance measures of the ipsilateral stretched and contralateral non-stretched lower limbs. Seventeen young men (24 ± 5 years) performed SBDJ before and after (stretched limb: immediately post-stretch, 10 and 20 minutes and non-stretched limb: immediately post-stretch) unilateral ankle plantar flexor SS (6 sets of 45s/15s, 70-90% point of discomfort). SBDJ performance measures included jump height, impulse, time to reach peak force, contact time as well as the sEMG integral (IEMG) and pre-activation (IEMGpre-activation) of the gastrocnemius lateralis. Ankle dorsiflexion passive ROM increased in the stretched limb after the SS (pre-test: 21 ± 4° and post-test: 26.5 ± 5°, p < 0.001). Post-stretching decreases were observed with peak force (p = 0.029), IEMG (P<0.001), and IEMGpre-activation (p = 0.015) in the stretched limb; as well as impulse (p = 0.03), and jump height (p = 0.032) in the non-stretched limb. In conclusion, SS effectively increased passive ankle ROM of the stretched limb, and transiently (less than 10 minutes) decreased muscle peak force and pre-activation. The decrease of jump height and impulse for the non-stretched limb suggests a SS-induced central nervous system inhibitory effect. Key pointsWhen considering whether or not to SS prior to athletic activities, one must consider the potential positive effects of increased ankle dorsiflexion motion with the potential deleterious effects of power and muscle activity during a simple jumping task or as part of the rehabilitation process.Since decreased jump performance measures can persist for 10 minutes in the stretched leg, the timing of SS prior to performance must be taken into consideration.Athletes, fitness enthusiasts and therapists should also keep in mind that SS one limb has generalized effects upon contralateral limbs as well.

Unilateral balance training enhances neuromuscular reactions to perturbations in the trained and contralateral limb.

The aim of this study was to investigate the effect of unilateral balance training on the reactive recovery of balance for both trained and untrained limbs. Twenty-three subjects were randomly assigned to either a control group (CG) or a training group (TG). The latter performed six weeks of balance training for the right leg. The pre- and post-training measurements were based on single leg standing posture on a moveable force platform which moved 6 cm anteriorly. TG subjects were tested on the trained (TR) and untrained leg (UTR), whereas CG subjects were tested on the right leg (CTR). The center of pressure trajectory length (CPLEN) and average speed (CPSPD) as well as onsets of muscular activation and time to peak (EMGTP) from lower limb muscles were calculated and compared by a 2-way ANOVA (three legs×two training status). Muscular onsets were reduced after training for TR (∼19 ms, p<0.05) and UTR (∼17 ms, p<0.05) with no significant changes for CTR. No effects of training for CPLEN and medial-lateral CPSPD were found. Furthermore, the EMGTP of UTR was predominantly greater before training (∼17 ms, p<0.05). However, after training the EMGTP was similar among limbs. These results suggest that concomitant with improved balance recovery and neuromuscular reactions in TR, there is also a cross-education effect in UTR, which might be predominantly related to supraspinal adaptations shared between interconnected structures in the brain.