Changes in muscle coactivation during running: a comparison between two techniques, forefoot vs rearfoot

Introduction: Surface electromyography has been a technique used to describe muscle activity during running. However, there is little literature that analyses the behaviour of muscle coactivation in runners, describing the effect between two techniques associated with the initial contact, such as the use of rearfoot (RF) and forefoot (FF). Material and method: The purpose of this study was to compare muscle coactivation levels developed in the lower limb during two running techniques, FF vs RF. Fourteen amateur runners were evaluated (eight men, six women; age= 23.21 ± 3.58 years, mass= 63.89 ± 8.13 kg, height= 1.68 ± 0.08m). Surface electromyography was used to measure muscle activity during both running techniques evaluated on a treadmill, considering the muscle pairs: Rectus femoris- Biceps femoris (RFe-BF), Lateral Gastrocnemius–Tibialis Anterior (LG-TA), and Medial Gastrocnemius - Tibialis Anterior (MG-TA). These were calculated in three windows considering ten running cycles (0-5%, 80-100%, and 0-100%). To compare FF vs RF t-student test for paired data was used. Results: It was observed significant differences in the MG-TA pair (FF= 18.42 ± 11.84% vs RF = 39.05 ± 13.28%, p = 0.0018 during 0-5%, and RFe-BF pair (FF = 42.38 ± 18.11% vs RF = 28.37 ± 17.2%, p = 0.0331) during 80-100% of the race. Conclusion: Our findings show that the behaviour of muscle coactivation is different between FF vs RF techniques if we analyze little windows in the running cycle. This could be associated with an increase in the joint stability between these short intervals, represented in the initial and final regions of the running cycle.

Detection of epimuscular myofascial forces by Golgi tendon organs

Skeletal muscles embed multiple tendon organs, both at the proximal and distal ends of muscle fibers. One of the functions of such spatial distribution may be to provide locally unique force feedback, which may become more important when stresses are distributed non-uniformly within the muscle. Forces exerted by connections between adjacent muscles (i.e. epimuscular myofascial forces) may cause such local differences in force. The aim of this exploratory study was to investigate the effects of mechanical interactions between adjacent muscles on sensory encoding by tendon organs. Action potentials from single afferents were recorded intra-axonally in response to ramp-hold release (RHR) stretches of a passive agonistic muscle at different lengths or relative positions of its passive synergist. The tendons of gastrocnemius (GAS), plantaris (PL) and soleus (SO) muscles were cut from the skeleton for attachment to servomotors. Connective tissues among these muscles were kept intact. Lengthening GAS + PL decreased the force threshold of SO tendon organs (p = 0.035). The force threshold of lateral gastrocnemius (LG) tendon organs was not affected by SO length (p = 0.371). Also displacing LG + PL, kept at a constant muscle–tendon unit length, from a proximal to a more distal position resulted in a decrease in force threshold of LG tendon organs (p = 0.007). These results indicate that tendon organ firing is affected by changes in length and/or relative position of adjacent synergistic muscles. We conclude that tendon organs can provide the central nervous system with information about local stresses caused by epimuscular myofascial forces.

A Pilot Study of Muscle Force between Normal Shoes and Bionic Shoes during Men Walking and Running Stance Phase Using Opensim

The original idea for bionic shoes (BSs) involves combining the function of unstable foot conditions and the structure of the human plantar. The purpose of this study was to investigate the differences between the normal shoes (NS) and the BS during the stance phases of walking and running. A total of 15 Chinese males from Ningbo University were recruited for this study (age: 24.3 ± 2.01 years; height: 176.25 ± 7.11 cm, body weight (BW): 75.75 ± 8.35 kg). The participants were asked to perform a walking and running task. Statistical parametric mapping (SPM) analysis was used to investigate any differences between NSs and BSs during the walking and running stance phases. The results demonstrated that there were significant differences found (21.23–28.24%, p = 0.040; 84.47–100%, p = 0.017) in hip extension and flexion between the NS and the BS during the walking stance phase. There were no significant differences found in ankle and moment during the running stance phase. Significant differences were found in the rectus femoris (5.29–6.21%; p = 0.047), tibialis anterior (14.37–16.40%; p = 0.038), and medial gastrocnemius (25.55–46.86%; p < 0.001) between the NS and the BS during the walking stance phase. Significant differences were found in rectus femoris (12.83–13.10%, p = 0.049; 15.89–80.19%, p < 0.001), tibialis anterior (15.85–18.31%, p = 0.039; 21.14–24.71%, p = 0.030), medial gastrocnemius (80.70–90.44%; p = 0.007), and lateral gastrocnemius (11.16–27.93%, p < 0.001; 62.20–65.63%, p = 0.032; 77.56–93.45%, p < 0.001) between the NS and the BS during the running stance phase. These findings indicate that BSs are more efficient for muscle control than unstable shoes and maybe suitable for rehabilitation training.

Comparison of the Asymmetries in Foot Posture and Properties of Gastrocnemius Muscle and Achilles Tendon Between Patients With Unilateral and Bilateral Knee Osteoarthritis Patients

Background: Asymmetrical foot posture and properties alterations of the gastrocnemius muscle (GM) and Achilles tendon (AT) were observed in knee osteoarthritis (KOA). We aimed to investigate the inter-limbs asymmetries in foot posture and the properties of GM and AT and explore the association between them.Methods: A total of 62 subjects with unilateral or bilateral KOA were included in this study: 30 patients with unilateral pain and 32 patients with bilateral pain were assigned to the bilateral group (BG) and unilateral group (UG), respectively. The relatively serious leg (RSL) and relatively moderate leg (RML) were judged according to the severity of symptoms assessed by using visual analogue scale (VAS) motion. Foot posture and asymmetrical foot posture scores were assessed based on Foot Posture index (FPI-6). Subsequently, all the participants received an assessment for properties of GM and AT, including tone/tension (Hz), stiffness (N/m), and elasticity. We calculated the asymmetry index of AT (Asy-AT) in both legs and the difference of muscle properties between medial and lateral gastrocnemius (D-MLG) in the ipsilateral limb.Results: Asymmetry of foot posture was categorized into three types including normal, asymmetry, and severe asymmetry. The percentage of subjects classified as normal was higher in the BG (62.5%) than in the UG (36.67%), p &lt; 0.05. Tension of AT and tone of lateral gastrocnemius (LG) in RSL were higher than those in RML (15.71 ± 0.91 vs. 15.23 ± 1.01; 25.31 ± 2.09 vs. 23.96 ± 2.08, p &lt; 0.01 and p &lt; 0.01, respectively), and stiffness of AT in the RSL was higher than that in RML (676.58 ± 111.45 vs. 625.66 ± 111.19, p &lt; 0.01). Meanwhile, a positive relationship was found between ipsilateral FPI and tone of MG and LG in the left leg (0.246 per degree, 95% CI: −0.001, 0.129; p = 0.054 and 0.293 per degree, 95% CI: −0.014, 0.157; p = 0.021, respectively) and right leg (0.363 per degree, 95% CI: 0.033, 0.146; p = 0.004 and 0.272 per degree, 95% CI: 0.007, −0.144; p = 0.032, respectively). Moreover, a positive link was observed between asymmetrical FPI scores and K/L grade (0.291 per degree, 95% CI: 0.018, 0.216; p = 0.022). Furthermore, a significantly greater Asy-AT(tension) was detected in the UG than that in the BG (UG vs. UG: 8.20 ± 5.09% vs. 5.11 ± 4.72%, p &lt; 0.01). Additionally, an increased asymmetrical FPI score (i.e., more severe asymmetry) was significantly associated with increases in Asy-AT(tension) and Asy-AT(stiffness) (0.42 per degree, 95% CI: 0.533, 1.881; p = 0.001 and 0.369 per degree, 95% CI: 0.596, 2.82; p = 0.003, respectively).Conclusions: The stiffness and tension of AT and the tone of LG in RSL were higher than those in RML in KOA patients, and inter-limbs foot posture and tension of AT were more asymmetrical in unilateral KOA patients compared to patients with bilateral KOA. Notably, foot posture, as an important biomechanical factor, was significantly associated with properties of GM, AT, and K/L grade in KOA patients.

Does different activation between the medial and the lateral gastrocnemius during walking translate into different fascicle behavior?

The functional difference between the medial gastrocnemius (MG) and lateral gastrocnemius (LG) during walking in humans has not yet been fully established. Although evidence highlights that the MG is activated more than the LG, the link with potential differences in mechanical behavior between these muscles remains unknown. In this study, we aimed to determine whether differences in activation between the MG and LG translate into different fascicle behavior during walking. Fifteen participants walked at their preferred speed under two conditions: 0% and 10% incline treadmill grade. We used surface electromyography and B-mode ultrasound to estimate muscle activation and fascicle dynamics in the MG and LG. We observed a higher normalized activation in the MG than LG during stance, which did not translate into greater MG normalized fascicle shortening. However, we observed significantly less normalized fascicle lengthening in the MG than LG during early stance, which matched with the timing of differences in activation between muscles. This resulted in more isometric behavior of the MG, which likely influences the muscle-tendon interaction and enhances the catapult-like mechanism in the MG compared to the LG. Nevertheless, this interplay between muscle activation and fascicle behavior, evident at the group level, was not observed at the individual level as revealed by the lack of correlation between the MG-LG differences in activation and MG-LG differences in fascicle behavior. The MG and LG are often considered as equivalent muscles but the neuromechanical differences between them suggest that they may have distinct functional roles during locomotion.

Diagnosis and Control for the Second Degree of Lateral Gastrocnemius Muscle Tear in High-School Soccer Player: A Case Report

This case study presents the epidemiology, etiology, diagnostic criteria, therapeutic intervention and modification, and rehabilitation of a lateral gastrocnemius tear in high school male soccer player. The patient injured his left gastrocnemius during soccer practice without contact. His injured leg was controlled with heel pad for equine to reduce the stress on injured gastrocnemius muscle for the initial of two weeks. The patient returned to regular practice 8 weeks after injury.

Diagnosis and Control for the Second Degree of Lateral Gastrocnemius Muscle Tear in High-School Soccer Player: A Case Report

This case study presents the epidemiology, etiology, diagnostic criteria, therapeutic intervention and modification, and rehabilitation of a lateral gastrocnemius tear in high school male soccer player. The patient injured his left gastrocnemius during soccer practice without contact. His injured leg was controlled with heel pad for equine to reduce the stress on injured gastrocnemius muscle for the initial of two weeks. The patient returned to regular practice 8 weeks after injury.

Easy Surgical Approach of the Posterolateral Corner of the Knee

Background: The anatomy of the posterolateral corner (PLC) of the knee is complex. The approach of the PLC can be a challenging and stressful surgical time. Indications: The indications are posterolateral meniscal repair, open lateral meniscus allograft transplantation, posterolateral tibial plateau fracture, and PLC reconstruction for grade III sprains. Technique Description: The skin incision is straight, realized with the knee positioned at 90° of flexion, passing slightly posterior to the lateral epicondyle, anterior to the fibular head (FH), and ending on Gerdy’s tubercle. The subcutaneous tissues are dissected posteriorly so as to expose the FH and the biceps femoris (BF) tendon. The aponeurosis of the peroneus muscles is incised vertically opposite to the anterior side of the FH. The common fibular nerve is exposed at the neck of the fibula. Metzenbaum scissors are then inserted subaponeurotically, posteriorly, and parallel to the BF tendon, superficially to the nerve. An incision is made opposite the scissor’s blades, freeing the common fibular nerve. The BF tendon is spread forward and the lateral gastrocnemius is pulled posteriorly. Metzenbaum scissors are inserted in a closed position between the lateral gastrocnemius and the posterolateral joint capsule, and then spread to create a triangular door with a proximal base. The base consists of the BF tendon, the posterior side of the lateral gastrocnemius, and the anterior side of the posterolateral joint capsule. A counter-angled Hohmann retractor can now be applied against the posterior tibial plateau to retract the lateral gastrocnemius posteriorly and medially, exposing the PLC of the knee. Results: Noble structures are easily exposed and protected. The common fibular nerve is dissected and reclined posteriorly, and the popliteus vessels are reclined posteriorly and medially, protected by the lateral gastrocnemius. Passing under the BF tendon allows a better vision of the PLC along with less constraint than passing above, as the working window is further away from the femoral insertion of the lateral gastrocnemius. Discussion/Conclusion: The present surgical approach allows a simple, safe, and reproducible exposure of the PLC of the knee.

Estimation of maximal muscle electromyographic activity from the relationship between muscle activity and voluntary activation

Maximal muscle activity recorded with surface electromyography (EMG) is an important neurophysiological measure. It is frequently used to normalize EMG activity recorded during passive or active movement. However, the true maximal muscle activity cannot be determined in people with impaired capacity to voluntarily activate their muscles. Here we determined whether maximal muscle activity can be estimated from muscle activity produced during submaximal voluntary activation. Twenty-five able-bodied adults (18 males, mean age 29 years, range 19-64 years) participated in the study. Participants were seated with the knee flexed 90° and the ankle in 5° of dorsiflexion from neutral. Participants performed isometric voluntary ankle plantarflexion contractions at target torques, in random order: 1, 5, 10, 15, 25, 50, 75, 90, 95, 100% of maximal voluntary torque. Ankle torque, muscle activity in soleus, medial and lateral gastrocnemius muscles, and voluntary muscle activation determined using twitch interpolation were recorded. There was a strong loge-linear relationship between measures of muscle activation and muscle activity in all three muscles tested. Linear mixed models were fitted to muscle activation and loge-transformed EMG data. Each 1% increase in muscle activation increased muscle activity by a mean of 0.027 ln(mV) [95% CI 0.025 to 0.029 ln(mV)] in soleus, 0.025 ln(mV) [0.022 to 0.028 ln(mV)] in medial gastrocnemius, and 0.028 ln(mV) [0.026 to 0.030 ln(mV)] in lateral gastrocnemius. The relationship between voluntary muscle activation and muscle activity can be described with simple mathematical functions. In future, it should be possible to normalize recorded muscle activity using these types of functions.