Electromyographic changes of agonist and antagonist calf muscles during maximum isometric induced fatigue

The purpose of this study was to examine electromyographic changes of the agonist and antagonist muscles during fatigue. Nine healthy, untrained subjects exerted a maximum voluntary heel lifting contraction with their dominant limb. The EMG activity over the soleus and the tibialis anterior muscles was recorded during the contraction. The results showed that the torque output during heel lifting and the soleus EMG activity decreased, whereas the tibialis anterior EMG revealed a small but non-significant decrease. However, the ratio of the tibialis anterior to the soleus EMG increased significantly at the end of the fatigue protocol, a fact that reveals that the decrease rate of the antagonist's activity was significantly lower than the decrease rate of the agonist activity. It is concluded that during a maximal fatigue protocol, both the agonist and antagonist muscle activity may decline, however, the slower rate of antagonist's activity decrease relative to the agonist's activity is a finding that requires further investigation. This finding may reflect a higher level of agonist and antagonist muscle co-activation and probably a relatively higher opposing torque from the antagonist muscles at the end of the fatigue session.     

Plantar flexion torque as a function of time of day

The possible peripheral and/or central origin in the mechanisms responsible for day-time fluctuation in maximal torque of the triceps surae muscle were investigated with a special emphasis on antagonist muscle coactivation. Eleven healthy male subjects (physical education students) took part in this investigation. The electromechanical properties of the plantar flexor muscles were recorded at two different times of day: between 06:00 h and 08:00 h in the morning and between 17:00 h and 19:00 h in the evening. To investigate peripheral mechanisms, the posterior tibial nerve was stimulated at rest, using percutaneous electrical stimuli, to evoke single twitch, double twitch, and maximal tetanic contraction (100 Hz). Maximal voluntary contraction of the plantar flexors was also assessed by means of the relative electromyographic activity of respective agonist and antagonist muscles (soleus, gastrocnemius medialis, gastrocnemius lateralis, and tibialis anterior). A double twitch was delivered during maximal voluntary plantar flexion to record muscle activation (i.e., interpolated twitch technique). The coactivation level of the tibialis anterior muscle during plantar flexion was calculated. The results indicated a significant decrease in maximal voluntary muscle torque of triceps surae in the evening as compared with the morning (-7.0 %; p < 0.05). Concerning the central command, when extrapolated by the twitch interpolation technique, the decrease in mean activation level of -6.8 % was consistent with the fluctuation in torque (-7.0 %). Soleus muscle electromyographic activity (normalized to the M-wave) showed a significant decline (21.6 %; p < 0.001). Moreover, individual changes in MVC percentage were significantly related to those of normalized electromyographic activity of the soleus muscle (r = 0.688; p < 0.01). Thus, it indicated that the subject's capacity to activate the soleus muscle was affected by the time of day. The coactivation level in the tibialis anterior muscle during plantar flexion did not change significantly in the evening. Concerning peripheral mechanisms, we observed a decrease in maximal M-wave amplitude for soleus and gastrocnemii, associated with unchanged single twitch and tetanus torque. To conclude, impairment in soleus muscle central command seemed to be the mechanism in the origin of torque failure. Such information would be of importance in the investigation of day-time fluctuations in complex motor task performances implicating the triceps surae muscle.     

Comparison of muscle activity during walking in subjects with and without diabetic neuropathy

The purpose of this study was to compare muscle activity and joint moments in the lower extremities during walking between subjects with diabetic neuropathy (DN) and control subjects. Tests were performed on nine subjects with DN, and nine age, gender, and weight-matched controls. Onset and cessation times of lower extremity electromyographic (EMG) activity and joint moments were determined. Results demonstrated that subjects with DN had less ankle mobility, slower walking speeds, longer stance phases, and lower peak ankle dorsiflexion, ankle plantar flexion, and knee extension moments than control subjects. Onset times with respect to heel-strike (HS) for the soleus, medial gastrocnemius, and medial hamstring muscles were significantly earlier during the gait cycle (GC) in subjects with DN than in control subjects. The cessation times of soleus, tibialis anterior, vastus medialis, and medial hamstring muscles were significantly prolonged in subjects with DN. Subjects with DN showed more co-contractions of agonist and antagonist muscles at the ankle and knee joints during stance phase compared with control subjects. These gait changes and co-contractions may allow subjects with DN to adopt a safer, more stable gait pattern to compensate for diminished sensory information from the ankle and the foot. The premature activation of soleus and medial gastrocnemius muscles in subjects with DN could be contributing to abnormal forefoot plantar pressure distribution. Additional research is needed to clarify the relationship between the premature activation of triceps surae muscles and the forefoot plantar pressure parameters in subjects with DN.     

Intramuscular pressure and torque during isometric, concentric and eccentric muscular activity

Intramuscular pressures, electromyography (EMG) and torque generation during isometric, concentric and eccentric maximal isokinetic muscle activity were recorded in 10 healthy volunteers. Pressure and EMG activity were continuously and simultaneously measured side by side in the tibialis anterior and soleus muscles. Ankle joint torque and position were monitored continuously by an isokinetic dynamometer during plantar flexion and dorsiflexion of the foot. The increased force generation during eccentric muscular activity, compared with other muscular activity, was not accompanied by higher intramuscular pressure. Thus, this study demonstrated that eccentric muscular activity generated higher torque values for each increment of intramuscular pressure. Intramuscular pressures during antagonistic co-activation were significantly higher in the tibialis anterior muscle (42–46% of maximal agonistic activity) compared with the soleus muscle (12–29% of maximal agonistic activity) and was largely due to active recruitment of muscle fibers. In summary, eccentric muscular activity creates higher torque values with no additional increase of the intramuscular pressure compared with concentric and isometric muscular activity.     

Delayed influence of stretch-shortening cycle fatigue on large ankle joint position coded with static positional signals

This study examines the static position sense from the ankle joint following a unilateral exhaustive stretch-shortening cycle (SSC)-type exercise involving mostly the triceps surae muscle group. Fatigue effects were quantified within the exercised and non-exercised leg through a maximal isometric voluntary plantarflexion test (MVC) performed immediately before (Pre) and after the SSC exercise, and repeated 2 (D2) and 8 (D8) days later. The static position sense test consisted in active reproductions with the non-exercised ankle of two target dorsiflexed positions (small and large) previously maintained with either the non-exercised (control procedure) or the exercised ankle (fatigue procedure). This test was carried out at Pre, D2, and D8. At D2, the MVC test revealed significant decreases in voluntary soleus muscle activity and peak plantarflexion force. The position sense test showed no error in reproduction accuracy in the control procedure. In contrast, the fatigue procedure revealed an overestimation of the large dorsiflexed position, only, with an associated increase of the agonist tibialis muscle activity. In agreement with the antagonist (stretched) muscle influence on the position sense, this overestimation is mostly attributed to potential SSC fatigue effects on ascending proprioceptive afferents issued from the exercised/inflamed antagonist muscles.     

Alteration of proton diffusivity associated with passive muscle extension and contraction

PURPOSE: To determine whether passive muscle extension and contraction affect the proton diffusivity of the muscle. MATERIALS AND METHODS: Five male subjects were examined. The fractional anisotropy (FA), and primary (lambda(1)), secondary (lambda(2)), and tertiary eigenvalues (lambda(3)) of the right tibialis anterior and medial gastrocnemius muscles were compared between conditions of passive plantar flexion and passive dorsiflexion of the ankle joint. RESULTS: In the tibialis anterior, FA, and lambda(1) at dorsiflexion decreased significantly (P < 0.01 and P < 0.01, respectively) compared to those at plantar flexion, but lambda(3) at dorsiflexion increased significantly (P = 0.02). In the gastrocnemius, FA and lambda(1) at dorsiflexion increased significantly (P < 0.01 and P < 0.01, respectively) compared to those at plantar flexion, but lambda(3) at dorsiflexion decreased significantly (P < 0.01). The lambda(2) value showed no significant change in either the tibialis anterior or medial gastrocnemius. CONCLUSION: The results indicate that passive muscle extension and contraction associated with passive joint movement would affect the proton diffusivity of the muscle. This alteration of proton diffusivity is probably associated with microscopic structural changes of the muscle.     

Iliocapsularis: Technical application of fine-wire electromyography,and direction specific action during maximum voluntary isometric contractions

The iliocapsularis muscle of the anterior hip may play an important role in hip function, but no electromyographic (EMG) recordings have been made. This muscle provides the most substantial muscular attachment to the anterior hip capsule and is hypothesised to have a dynamic role to limit capsular impingement and to augment joint stability. Current understanding of the function of iliocapsularis is based on limited cadaveric and radiographic studies. Located deep over the hip joint it would require intramuscular fine-wire EMG to evaluate its activity directly with limited cross-talk from overlying muscles. The primary aim of this study was to describe a new technique for insertion of intramuscular EMG electrodes into iliocapsularis and to report its activation during different directions of hip maximum voluntary isometric contraction (MVIC). Fifteen healthy volunteers (10 M, mean age (SD) 22 (2) years) who were free from hip pain were recruited for electrode insertion and to perform MVIC’s in six directions at 0° and three directions at 90° of hip flexion. Intramuscular electrodes were successfully inserted into the iliocapsularis muscle with guidance from real-time ultrasound imaging. The greatest muscle activity occurred during resisted hip flexion at 90° (Median (IQR); 100.0 (1.2) % MVIC) and lowest activity during hip extension, 0° (0.5 (0.3) % MVIC). These findings have implications for our understanding of iliocapsularis’ functional role. This paper provides the first report of intramuscular electrode insertion into iliocapsularis with guided technical instructions for future EMG investigations in other populations and tasks.     

Changes in muscle activity in children with hemiplegic cerebral palsy while walking with and without ankle–foot orthoses

We compared the electromyographic (EMG) signals of lower extremity muscle groups in 10 children with hemiplegic cerebral palsy (CP) while walking barefoot and in a hinged ankle–foot orthosis (HAFO). All children had excessive plantarflexion and initial toe-contact on the affected side when walking barefoot, a typical gait pattern for hemiplegic patients. The patients walked with a physiological heel–toe gait pattern when wearing the HAFO. The peak activity of the tibialis anterior muscle was reduced by 36.1% at initial contact and loading response phase and by 57.3% just after toe-off when using a HAFO. The decrease in activity was thought to result from the change in gait pattern from a toe-gait to a heel–toe gait as well as the use of a HAFO. The HAFO also slightly decreased muscle activity in the proximal leg muscles mainly during swing phase, improved stride length, decreased cadence, improved walking speed, increased peak hip flexion, improved kinematics in loading response phase at the knee, and reduced the excessive ankle plantarflexion.     

Changes in muscle activity in children with hemiplegic cerebral palsy while walking with and without ankle-foot orthoses

We compared the electromyographic (EMG) signals of lower extremity muscle groups in 10 children with hemiplegic cerebral palsy (CP) while walking barefoot and in a hinged ankle–foot orthosis (HAFO). All children had excessive plantarflexion and initial toe-contact on the affected side when walking barefoot, a typical gait pattern for hemiplegic patients. The patients walked with a physiological heel–toe gait pattern when wearing the HAFO. The peak activity of the tibialis anterior muscle was reduced by 36.1% at initial contact and loading response phase and by 57.3% just after toe-off when using a HAFO. The decrease in activity was thought to result from the change in gait pattern from a toe-gait to a heel–toe gait as well as the use of a HAFO. The HAFO also slightly decreased muscle activity in the proximal leg muscles mainly during swing phase, improved stride length, decreased cadence, improved walking speed, increased peak hip flexion, improved kinematics in loading response phase at the knee, and reduced the excessive ankle plantarflexion.     

Serratus anterior muscle activity during selected rehabilitation exercises

The purpose of this study was to document the electromyographic activity and applied resistance associated with eight scapulohumeral exercises performed below shoulder height. We used this information to design a continuum of serratus anterior muscle exercises for progressive rehabilitation or training. Five muscles in 20 healthy subjects were studied with surface electrodes for the following exercises: shoulder extension, forward punch, serratus anterior punch, dynamic hug, scaption (with external rotation), press-up, push-up plus, and knee push-up plus. Electromyographic data were collected from the middle serratus anterior, upper and middle trapezius, and anterior and posterior deltoid muscles. Each exercise was partitioned into phases of increasing and decreasing force and analyzed for average and peak electromyographic amplitude. Resistance was provided by body weight, an elastic cord, or dumbbells. The serratus anterior punch, scaption, dynamic hug, knee push-up plus, and push-up plus exercises consistently elicited serratus anterior muscle activity greater than 20% maximal voluntary contraction. The exercises that maintained an upwardly rotated scapula while accentuating scapular protraction, such as the push-up plus and the newly designed dynamic hug, elicited the greatest electromyographic activity from the serratus anterior muscle.     

Direct evidence of the anterior cruciate ligament-hamstring reflex arc in humans

It has been emphasized that the anterior cruciate ligament plays an important role in the proprioceptive feedback system. The anterior cruciate ligament-hamstring reflex has been revealed in animal experiments, but it has not been established in humans. The purpose of this study was to demonstrate direct evidence of the anterior cruciate ligament-hamstring reflex arc. Nine knees in nine healthy subjects were investigated. The anterior cruciate ligament was stimulated by the use of wire electrodes inserted using an arthroscopic technique. Electromyographic signals from the biceps femoris and the semitendinosus muscles were recorded with surface electrodes. The change in electromyographic activity was analyzed after electrical stimulation in the normal knee condition, and again after intraarticular sensation had been interrupted with a local anesthetic. After electrical stimulation, subjects demonstrated increased electromyographic activity of the hamstring muscles in the normal knee condition. This response indicates the existence of an anterior cruciate ligament-hamstring reflex arc. Conversely, there was no change in activity for the hamstring muscle in the anesthetized knee because the afferent impulse from the neural elements of the anterior cruciate ligament had been removed.     

Electromyographic and kinematic analysis of cutting maneuvers. Implications for anterior cruciate ligament injury

The objective of this study was to qualitatively characterize quadriceps and hamstring muscle activation as well as to determine knee flexion angle during the eccentric motion of sidestep cutting, cross-cutting, stopping, and landing. Fifteen healthy collegiate and recreational athletes performed the four movements while knee angle and electromyographic activity (surface electrodes) of the vastus lateralis, vastus medialis obliquus, rectus femoris, biceps femoris, and medial hamstring (semimembranosus/semitendinosus) muscles were recorded. The results indicated that there is high-level quadriceps muscle activation beginning just before foot strike and peaking in mid-eccentric motion. In these maneuvers, the level of quadriceps muscle activation exceeded that seen in a maximum isometric contraction. Hamstring muscle activation was submaximal at and after foot strike. The maximum quadriceps muscle activation for all maneuvers was 161% maximum voluntary contraction, while minimum hamstring muscle activity was 14%. Foot strike occurred at an average of 22 degrees of knee flexion for all maneuvers. This low level of hamstring muscle activity and low angle of knee flexion at foot strike and during eccentric contraction, coupled with forces generated by the quadriceps muscles at the knee, could produce significant anterior displacement of the tibia, which may play a role in anterior cruciate ligament injury.     

A model for lever-arm length calculation of the flexor and extensor muscles at the ankle

A sagittal-plane mathematical model of joint mobility, including the mechanical effect of the extensor retinacula, was used to predict the lever arm lengths of the main flexor and extensor muscles of the human ankle over the range of movement. In plantarflexion, the centre of rotation lies posteriorly and distally, maximising the lever arm of the tibialis anterior. The action of the gastrocnemius and soleus is maximised in dorsiflexion. Traditional calculation of ankle joint moment based on a fixed centre of rotation is acceptable only in exercises such as level walking with a limited range of motion about the neutral position. The present model with a moving centre is particularly advised in exercises which take the joint nearer to the extremes of sagittal motion.     

The soleus muscle acts as an agonist for the anterior cruciate ligament. An in vitro experimental study

BACKGROUND: Although the quadriceps muscles are known antagonists for the anterior cruciate ligament and the hamstring muscles are known agonists, the influence of the calf muscles on knee stability is not well understood. HYPOTHESIS: The soleus muscle acts as an anterior cruciate ligament agonist and the gastrocnemius muscle acts as an anterior cruciate ligament antagonist. STUDY DESIGN: Controlled laboratory study. METHODS: Six cadaveric knees were tested with individual and combined activation of the gastrocnemius and soleus muscles to determine the influence of simulated muscle contraction on tibiofemoral motion. RESULTS: At all flexion angles, applying the soleus muscle force tended to translate the tibia posteriorly, whereas applying the gastrocnemius muscle force tended to translate the tibia anteriorly. Applying the soleus and gastrocnemius muscle forces together also tended to translate the tibia anteriorly. The average anterior and posterior tibial translations were greatest at 50 degrees of flexion. CONCLUSIONS: The soleus muscle is capable of acting as an agonist for the anterior cruciate ligament and the gastrocnemius muscle can act as an antagonist. CLINICAL RELEVANCE: A better understanding of the agonistic behavior of the soleus muscle on the anterior cruciate ligament may lead to the development of training and rehabilitation strategies that could reduce the incidence of injury and improve function in both patients with anterior cruciate ligament deficiency and patients who have undergone anterior cruciate ligament reconstruction.     

Walking while resisting a perturbation: Effects on ankle dorsiflexor activation during swing and potential for rehabilitation

Motor control studies have shown that when walking is performed while resisting a perturbation applied to the lower limb, the muscle activation pattern can be temporarily modified. The objective of the present study is to validate if such an approach, targeting the ankle, could specifically promote an increased activation of the ankle dorsiflexor muscles that are of key importance for the rehabilitation of foot drop.

Methods

12 adults, with no gait deficit, walked on a treadmill for three periods of 5 min: before, during and after exposure to a torque perturbation applied by a robotized ankle-foot orthosis that tended to plantarflex the ankle during the swing phase. Spatiotemporal gait parameters, ankle and knee kinematics, and the electromyographic activity of five lower limb muscle groups were recorded.

Results

The perturbation initially caused a deviation of the ankle towards plantarflexion. This movement error was rapidly reduced and associated with a large increase (78.2%; p < 0.001) in tibialis anterior (ankle dorsiflexor; TA) activation, specifically in the stance-to-swing burst. This increase carried over to post-perturbation walking, gradually disappearing over several strides. Interestingly, these aftereffects led to an increase in peak ankle dorsiflexion of approximately 7° during the swing phase.

Conclusions

Walking while resisting a torque perturbation applied at the ankle during swing promotes an increase in TA muscle activation that carries over after perturbation removal, leading to an increased ankle dorsiflexion. Training based on this approach may have the potential of improving the gait of persons with foot drop.     

Tibialis anterior volumes and areas in ACL-injured limbs compared with unimpaired

PURPOSE: Past research has shown that subjects with ACL injuries show activation differences and atrophy in the muscles that cross the knee, including the gastrocnemii, which predominately act at the ankle. However, it is not known how the other ankle muscles that do not cross the knee are affected. We focused on the two muscles that control the ankle, the soleus and tibialis anterior muscles, to see how they were affected by an ACL injury. We hypothesized that the ankle muscles of subjects with ACL injuries that did not require surgery (copers) would be more like normals and that the muscles of subjects with ACL injuries who required surgery to return to normal activity (noncopers) would atrophy. METHODS: Twenty-seven subjects were divided into three even categories: unimpaired subjects, copers, and noncopers. Axial spin-echo T1-weighted MRI images were used to digitally reconstruct the tibialis anterior and the soleus. We used the digitally reconstructed muscles to determine the peak cross-sectional area and volume of each muscle. RESULTS: The copers' tibialis anterior muscles were similar to the unimpaired subjects, but, surprisingly, the noncoper's tibialis anterior muscles of the injured leg were larger than those of their uninjured legs (P < 0.05). In the soleus, the results showed a trend of not being affected. CONCLUSION: The increase in size of the tibialis anterior in noncopers may have been caused by altered gait patterns in noncopers. We believe this is due to either an ankle-stiffening strategy during heel strike or from the inversion of the foot causing external rotation of the tibia as a stabilizing technique for the knee.     

Combining muscle morphology and neuromotor symptoms to explain abnormal gait at the ankle joint level in cerebral palsy

BackgroundIndividuals with spastic cerebral palsy (CP) have neuromotor symptoms contributing towards their gait patterns. However, the role of altered muscle morphology alongside these symptoms is yet to be fully investigated.Research questionTo what extent can medial gastrocnemius and tibialis anterior volume and echo-intensity, plantar/dorsiflexion strength and selective motor control, plantarflexion spasticity and passive ankle dorsiflexion explain abnormal ankle gait.MethodIn thirty children and adolescents with spastic CP (8.6 ± 3.4 y/mo) and ten typically developing peers (9.9 ± 2.4 y/mo), normalised muscle volume and echo-intensity were estimated. Both cohorts also underwent three-dimensional gait analysis, whilst for participants with spastic CP, plantar/dorsi-flexion strength and selective motor control, plantarflexion spasticity and maximum ankle dorsiflexion were also measured. The combined contribution of these parameters towards five clinically meaningful features of gait were evaluated, using backwards multiple regression analyses.ResultsWith respect to the typically developing cohort, the participants with spastic CP had deficits in normalised medial gastrocnemius and tibialis anterior volume of 40% and 33%, and increased echo-intensity values of 19% and 16%, respectively. The backwards multiple regression analyses revealed that the combination of reduced ankle dorsiflexion, muscle volume, plantarflexion strength and dorsiflexion selective motor control could account for 12–62% of the variance in the chosen features of gait.SignificanceThe combination of altered muscle morphology and neuromotor symptoms partly explained abnormal gait at the ankle in children with spastic CP. Both should be considered as important measures for informed treatment decision-making, but further work is required to better unravel the complex pathophysiology.     

Effect of vibration-induced postural illusion on anticipatory postural adjustment of voluntary arm movement in standing humans.

We investigated the contribution of sensory signals arising from muscle proprioceptive receptors to anticipatory postural adjustments (APAs). During vibration applied to ankle (tibialis anterior; TA, soleus; Sol) or neck muscles, subjects generally describe having illusory sensations of whole-body movement, namely, whole-body movement in a backward and forward direction induced by vibration of the Sol or TA, respectively, and the front or back surface of the neck muscles, respectively. Preceding electromyographic (EMG) activity of the ipsilateral biceps femoris (BFi) muscle induced by rapid voluntary arm movement and the typical phenomenon of APA were changed dependent on these illusory whole-body movements, with preceding EMG activities of BFi appearing earlier in vibration applied to TA and later in vibration applied to Sol muscle. In vibration applied to the back surface of neck muscle, preceding EMG activities of BFi appeared earlier, as with vibration applied to TA. On the contrary, in vibration applied to the front surface of neck muscles, preceding EMG activities of BFi appeared later, as with vibration applied to Sol. Based on these results, we discuss changes in the central processing of proprioceptive signals used for coding of the spatial orientation of the body and its contribution to postural stabilization.     

胫骨前肌疲劳时比目鱼肌诱发肌电图H波的变化及其机制探讨

为了解主动肌疲劳时拮抗肌脊髓运动神经元兴奋性变化的规律 ,本研究采用踝关节背屈运动形式 ,对胫骨前肌 (主动肌 )疲劳状态下的比目鱼肌 (拮抗肌 )诱发肌电图H波成分进行了观察。并以压迫阻断胫骨前肌Ⅰa类神经纤维传导的方法 ,对比目鱼肌H波变化机制进行了分析探讨。结果发现 :(1)胫骨前肌疲劳后 ,比目鱼肌H波明显受到抑制 ,与安静时比较呈非常显著性差异 ;(2 )胫骨前肌Ⅰa类神经纤维传导被阻断后 ,比目鱼肌H波的抑制现象没有解除。表明 ,胫骨前肌疲劳时比目鱼肌H波被抑制的原因 ,可能是由于主动肌内的代谢产物激活了Ⅲ·Ⅳ类神经纤维的感受器 ,Ⅲ·Ⅳ类神经纤维的传入冲动增加 ,使Ⅰa抑制性中间神经元被激活 ,导致拮抗肌脊髓运动神经元的兴奋性受到了抑制     

Maximal shortening velocity during plantar flexion: Effects of pre‐activity and initial stretching state

We investigated the effects of the initial length of the muscle‐tendon unit (MTU ) and muscle pre‐activation on muscle‐tendon interactions during plantarflexion performed at maximal velocity. Ultrasound images of gastrocnemius medialis were obtained on 11 participants in three conditions: (a) active plantarflexion performed at maximal velocity from three increasingly stretched positions (10°, 20°, and 30° dorsiflexion), (b) passive plantarflexion induced by a quick release of the ankle joint from the same three positions, and (c) pre‐activation, which consisted of a maximal isometric contraction of the plantarflexors at 10° of dorsiflexion followed by a quick release of ankle joint. During the active condition at maximal velocity, initial MTU stretch positively influenced ankle joint velocity (+15.3%) and tendinous tissues shortening velocity (+37.6%) but not the shortening velocity peak value reached by muscle fascicle. The muscle fascicle was shortened during the passive condition; however, its shortening velocity never exceeded peak velocity measured in the active condition. Muscle pre‐activation resulted in a considerable increase in ankle joint (+114.7%) and tendinous tissues velocities (+239.1%), although we observed a decrease in muscle fascicle shortening velocity. During active plantarflexion at maximal velocity, initial MTU length positively influences ankle joint velocity by increasing the contribution of tendinous tissues. Although greater initial stretch of the plantarflexors (ie, 30° dorsiflexion) increased the passive velocity of the fascicle during initial movement, its peak velocity was not affected. As muscle pre‐activation prevented reaching the maximal muscle fascicle shortening velocity, this condition should be used to characterize tendinous tissues rather than muscle contractile properties.