Epimuscular myofascial force transmission: A historical review and implications for new research. International society of biomechanics Muybridge award lecture, Taipei, 2007

Journal of Biomechanics

2016

a b s t r a c tSkeletal muscles of the rat anterior crural compartment are mechanically connected by epimuscular myofascial connections, but the relevance for mechanical muscle function within physiological ranges of joint motion is unclear. We evaluated the net effect at the ankle joint of epimuscular myofascial connections between tibialis anterior (TA) and extensor digitorum longus (EDL) muscles in the rat (n ¼ 8) and determined which anatomical structures may mediate such epimuscular mechanical interactions. We assessed (1) effects of knee angle (i.e. changes in EDL length and position relative to TA) and interactions of knee angle with fasciotomy and proximal EDL tenotomy on TA ankle moment and (2) the effect of knee angle on TA and EDL ankle moment summation. Knee angle was varied between 60°and 130°. Ankle angle was kept constant (90°). TA and EDL were excited individually and simultaneously (TA&EDL). The mathematical sum of individual TA and EDL moments was compared with the moment exerted by TA&EDL to assess the extent of non-additive ankle moment summation. Magnitude of TA ankle moment was not affected by knee angle, but frontal plane moment direction was. However, dissections indicated that this was not caused by the compartmental fascia or EDL length changes. Moment summation was non-additive in magnitude ( þ1.1 7 1.1% mean7 s.d.) and frontal plane direction. The latter was affected by knee angle and ranged from þ 0.27 0.3°at 60°to þ1.1 7 0.6°at 130°. As the net effects found were very limited, we conclude that myofascial connections between muscles in the anterior crural compartment have limited mechanical relevance during normal movement.

Section: Effects Of Epimuscular Myofascial Connections On Ta Ankle Momentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Limited mechanical effects of intermuscular myofascial connections within the intact rat anterior crural compartment

Tijs

Journal of Biomechanics

2016

“…Such differences, in turn, can be the result of differential activation levels, asynchronous patterns of activation and differences in pennation angle, or a consequence of joint angle changes as the two neighboring muscles span different joints and have different moment arms. To date, a number of in situ studies have reported mechanical effects of changes in muscle relative position (reviewed in Huijing, 2009). More recently, ultrasound studies have reported displacements between SO and GAS in humans, but only for passive muscle conditions during isolated knee movements or selective electrical stimulation of targeted muscles at fixed joint angles (Bojsen-Moller et al, 2010;Finni et al, 2015;Oda et al, 2007;Tian et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Longitudinal and transversal displacements between triceps surae muscles during locomotion of the rat

Bernabei

Journal of Experimental Biology

2017

The functional consequences of differential muscle activation and contractile behavior between mechanically coupled synergists are still poorly understood. Even though synergistic muscles exert similar mechanical effects at the joint they span, differences in the anatomy, morphology and neural drive may lead to non-uniform contractile conditions. This study aimed to investigate the patterns of activation and contractile behavior of triceps surae muscles, to understand how these contribute to the relative displacement between the one-joint soleus (SO) and two-joint lateral gastrocnemius (LG) muscle bellies and their distal tendons during locomotion in the rat. In seven rats, muscle belly lengths and muscle activation during level and upslope trotting were measured by sonomicrometry crystals and electromyographic electrodes chronically implanted in the SO and LG. Length changes of muscle-tendon units (MTUs) and tendon fascicles were estimated based on joint kinematics and muscle belly lengths. Distances between implanted crystals were further used to assess longitudinal and transversal deformations of the intermuscular volume between the SO and LG. For both slope conditions, we observed differential timing of muscle activation as well as substantial differences in contraction speeds between muscle bellies (maximal relative speed 55.9 mm s −1 ). Muscle lengths and velocities did not differ significantly between level and upslope locomotion, only EMG amplitude of the LG was affected by slope. Relative displacements between SO and LG MTUs were found in both longitudinal and transversal directions, yielding an estimated maximal length change difference of 2.0 mm between their distal tendons. Such relative displacements may have implications for the force exchanged via intermuscular and intertendinous pathways.

“…These studies have shown that, parallel to the path in which the force of a muscle is transmitted to the skeleton via its origin and insertion, connective tissue linkages located at the epimysium of a muscle transmit force to surrounding structures (Huijing, 2009;Maas and Sandercock, 2010). This so-called epimuscular myofascial force transmission suggests that muscles cannot be seen as independent actuators and that the classical view of a pure myotendinous transmission of skeletal muscle force may not be valid.…”

Section: Introductionmentioning

confidence: 99%

No functionally relevant mechanical effects of epimuscular myofascial connections between rat ankle plantar flexors

Tijs

Journal of Experimental Biology

2015

Triceps surae muscles are mechanically connected by the shared Achilles tendon and by epimuscular myofascial connections. We aimed to assess the effects of proximal lengthening of gastrocnemius and plantaris muscles, imposed by changes in knee angle, on the magnitude and direction of the 3D ankle moment exerted by the soleus muscle and the mechanical interaction between ankle plantar flexor muscles during co-activation of gastrocnemius muscle, in the rat (N=9). Ankle angle was kept constant (90 deg), whereas knee angle was varied between 60 deg and 130 deg. At each knee angle, the soleus muscle was excited individually as well as simultaneously with the gastrocnemius muscle (SO+GA). The mathematical sum of individual soleus and gastrocnemius ankle moments was compared with the ankle moment exerted by SO+GA to assess nonlinear summation. Knee angle did not affect the magnitude of the soleus ankle moment (P=0.695). Moment directions in the transverse (P=0.050) and frontal (P=0.008) planes were affected by knee angle, but dissection indicated that this was not caused by length changes of the two-joint synergistic muscles. Nonlinear summation was found in the magnitude (−1.4±1.9%, mean±s.d., P<0.001) and in the frontal plane vector direction of the ankle moment (0.13±0.23 deg, P=0.003); however, the extent did not change with knee angle. Although contraction of SO+GA increased the length of the Achilles tendon compared with its length at rest, this was not dependent on the knee angle (P=0.649). Despite the fact that intermuscular force transmission per se cannot be excluded, we conclude that, in vivo, the mechanical effects of epimuscular myofascial connections between rat ankle plantar flexors are not functionally relevant.