Factors Affecting Force Loss With Prolonged Stretching

Abstract

The purpose of this study was to investigate factors underlying the force loss occurring after prolonged, static, passive stretching. Subjects were tested before and 5-10 min following 20 min of static, passive stretching of the quadriceps (N = 12) or a similar period of no stretch (control, N = 6). Measurements included isometric maximal voluntary contraction (MVC) force, surface integrated electromyographic (iEMG) activity of the quadriceps and hamstrings, evoked contractile properties (twitch and tetanic force), and quadriceps inactivation as measured by the interpolated twitch technique (ITT). Following stretching, there was a significant 12% decrement in MVC with no significant changes in the control group. Muscle inactivation as measured by the ITT and iEMG increased by 2.8% and 20.2%, respectively. While twitch forces significantly decreased 11.7%, there was no change in tetanic force post-stretch. Although possible increases in muscle compliance affected twitch force, a lack of tetanic force change would suggest that post-stretch force decrements are more affected by muscle inactivation than changes in muscle elasticity. Key Words: antagonist, electromyography, maximum voluntary contraction, muscle activation, twitch, tetanus

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“…Several factors, which probably play a negative or positive role in sprint and CMJ, have been previously reported such as neural inhibition (Behm et al 2001), mechanical factors (Nelson and Sidaway 2002), reduced muscle temperature after SS (Mohr et al 2004) and reduced blood flow (Poole et al 1997). However, the precise mechanism that leads to stretch-induced sprint impairment is still not clear (Behm et al 2001). Regarding the CMJ, Kubo et al (2007) reported that prestretch augmentation of both CMJ and Drop Jumps (DJ) was related to tendon stiffness.…”

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“…The literature describes another possibility. Static stretching of stretched muscle reduces EMG (Behm, Button, & Butt, 2001), motoneuronal excitability (H-reflex activity) (Behm et al, 2013), muscle spindle type I and II afferents output (Guissard, Duchateau, & Hainaut, 1988), and corticospinal pathways by group II and IV muscle afferents inputs (Amann et al, 2013). This can influence central drive of the working muscles and potentially of non-exercised muscle as well (Amann et al, 2013).…”

Alongamento Intermitente E Contínuo Aumentam a Amplitude De Movimento E Reduzem a Força Dos Flexores De Punho

“…Diversos esportes e atividades recreativas utilizam os membros superiores no suporte ou transferência de força, e associam tais atividades à prática do alongamento como aquecimento ou mesmo como parte do processo de treinamento, visando o aumento da amplitude de movimento (ADM) (ex: judô, jiu-jitsu, basebol, ginástica olímpica, entre outros) [1][2][3][4][5] .…”

“…Entretanto, dependendo da forma como o alongamento é empregado no treinamento, este pode afetar diferentes sistemas biológicos como o neurofisiológico, hormonal, celular e mecânico, e influenciar de forma positiva ou negativa a resposta do tecido a estímulos subsequentes como a produção de força, potência ou o padrão de ativação muscular [4][5][6][7][8][9] . Diversos estudos demonstram efeitos deletérios na produção de força após exercícios de alongamento estático 5,6,10-13 e redução da atividade muscular após os exercícios de alongamento 8,14 , os quais podem estar relacionados à ajustes em diferentes mecanismos como os de inibição neural e/ou de alteração tecidual na unidade músculo-tendínea 5,6,[15][16][17] .…”