Differential displacement of the human soleus and medial gastrocnemius aponeuroses during isometric plantar flexor contractions in vivo

Abstract

. Differential displacement of the human soleus and medial gastrocnemius aponeuroses during isometric plantar flexor contractions in vivo. J Appl Physiol 97: 1908 -1914, 2004. First published June 25, 2004 doi:10.1152/ japplphysiol.00084.2004.-The human triceps surae muscle-tendon complex is a unique structure with three separate muscle compartments that merge via their aponeuroses into the Achilles tendon. The mechanical function and properties of these structures during muscular contraction are not well understood. The purpose of the study was to investigate the extent to which differential displacement occurs between the aponeuroses of the medial gastrocnemius (MG) and soleus (Sol) muscles during plantar flexion. Eight subjects (mean Ϯ SD; age 30 Ϯ 7 yr, body mass 76.8 Ϯ 5.5 kg, height 1.83 Ϯ 0.06 m) performed maximal isometric ramp contractions with the plantar flexor muscles. The experiment was performed in two positions: position 1, in which the knee joint was maximally extended, and position 2, in which the knee joint was maximally flexed (125°). Plantarflexion moment was assessed with a strain gauge load cell, and the corresponding displacement of the MG and Sol aponeuroses was measured by ultrasonography. Differential shear displacement of the aponeurosis was quantified by subtracting displacement of Sol from that of MG. Maximal plantar flexion moment was 36% greater in position 1 than in position 2 (132 Ϯ 20 vs. 97 Ϯ 11 N ⅐ m). In position 1, the displacement of the MG aponeurosis at maximal force exceeded that of the Sol (12.6 Ϯ 1.7 vs. 8.9 Ϯ 1.5 mm), whereas in position 2 displacement of the Sol was greater than displacement of the MG (9.6 Ϯ 1.0 vs. 7.9 Ϯ 1.2 mm). The amount and "direction" of shear between the aponeuroses differed significantly between the two positions across the entire range of contraction, indicating that the Achilles tendon may be exposed to intratendinous shear and stress gradients during human locomotion. triceps surae; Achilles tendon; ultrasound; connective tissue mechanical properties; tendon shear strain; intratendinous stress THE HUMAN TRICEPS SURAE muscle-tendon structure is intricate in constitution and function, with three separate muscle compartments that merge via their aponeuroses into a common tendon to ultimately insert on the calcaneus. The combined forces generated by the triceps surae muscles during locomotion are transmitted to the Achilles tendon and may reach 1,400 -2,600 N during walking and 3, 100 -5,330 N during running (13, 15, 34). It has been suggested that these large forces imposed on the tendon contribute to various loading-related pathologies such as tendinopathy (19), although the exact etiology remains largely intangible. Consequently, a more detailed understanding of the intrinsic contraction properties of the multipart triceps surae structure may contribute to the development of future treatment paradigms and/or prophylactic intervention models.Information on the mechanical properties and function of the aponeurosis and tendon have tradition...

Redundancy or heterogeneity in the electric activity of the biceps brachii muscle? Added value of PCA-processed multi-channel EMG muscle activation estimates in a parallel-fibered muscle

“…Estimates of muscle activation based on conventional bipolar EMG, however, have limitations (Farina et al, 2004;Staudenmann et al, 2006). Importantly, activity can be heterogeneous within muscles during voluntary contractions, as was shown with multi-channel EMG (Eriksson et al, 1984;Holtermann et al, 2005;Staudenmann et al, 2005Staudenmann et al, , 2009avan Zuylen et al, 1988, Vieira et al, 2011Wolf et al, 1998), as well as with ultrasound imaging (Bojson-Moller et al, 2004;Darby et al, 2012;Finni et al, 2003;Pappas et al, 2002). Thus information obtained by a single bipolar EMG will not be representative for the entire muscle and consequently muscle activation estimates derived from multi-channel EMG (collecting from different parts of the muscle) are superior to those derived from a single bipolar EMG (Staudenmann et al, 2010).…”

Influência de posições do joelho no torque e atividade mioelétrica do tríceps sural na flexão plantar isométrica máxima

“…A redução do torque durante a exão plantar com o joelho em exão de 90º, encontrada no presente estudo, é amplamente rati cada na literatura [12][13][14][15] . As alterações nos padrões de ativação mioelétrica dos…”

“…Durante a flexão da articulação do joelho os músculos GNs perdem eficiência mecânica por se afastarem do comprimento favorável em direção a um encurtamento [12][13][14] , representado pela parte ascendente da curva torque ângulo 1 . Nesta condição, a contribuição dos GNs para a produção de torque na flexão plantar seria menor em contração voluntária isométrica máxima (CVIM), resultando em menores valores de torque do que os obtidos com o joelho em extensão.…”

“…O SOL, por outro lado, não sofre alteração de seu comprimento com a variação do ângulo do joelho e, portanto, sua contribuição para o torque de exão plantar deve ser similar. Não há consenso na literatura sobre a participação de cada músculo do TS nesta redução de torque [12][13][14][15] .…”

Imaging Studies of the Mechanical and Architectural Characteristics of the Human Achilles Tendon in Normal, Unloaded and Rehabilitating Conditions

“…The same general principles of in vivo tendon testing have often been applied with the aim of characterizing the mechanical behavior of the human tendon in different in-vivo situations and conditions. The results obtained vary greatly (Arampatzis et al 2005;Bojsen-Møller et al 2004;Kubo et al 2002Kubo et al , 2004Maganaris and Paul 2002;Muramatsu et al 2001;Reeves et al 2005). In young sedentary adults, for example, the tendon stiffness, Young's modulus and mechanical hysteresis values are ~ 17-760 Nm/mm, 0.3-1.4 GPa, and 11-19%, respectively (for a review see Maganaris et al 2008).…”