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    Lower limb muscle fatigability is not associated with changes in movement strategies for balance control in the upright stance. Sant'Anna do Carmo Aprigio Patricia,Ramathur Telles de Jesus Igor,Porto Carla,Lemos Thiago,de Sá Ferreira Arthur Human movement science BACKGROUND:Fatigue is a distressing symptom inversely related to postural stability in adults with neuromuscular and systemic diseases. However, there is no information about the effects of lower limb muscles fatigability on the movement strategies for balance control in the upright standing. METHODS:This study enrolled 41 healthy subjects (female/male: 22/19; age 23 ± 3 years; body mass index 25.4 ± 3.7 kg/m). Participants underwent posturography and surface electromyography of the gastrocnemius medialis muscle during a sustained, fatiguing voluntary contraction of the gastrocnemius preceded and followed by quiet standing (120 s). Amplitude of electromyograms and fatigability were evaluated using the root mean square (RMS) value and both the RMS and spectral median frequency (f) slopes. Balance control was evaluated using the center-of-pressure elliptic area (Area) and average velocity (Vavg). Movement strategies for balance control were evaluated using the number of high-density regions (nHDR) and spatial patterns of the three-dimensional statokinesigram. RESULTS:Mean time to muscle fatigability was 258 ± 190 s. Area and Vavg but not nHDR increased after the fatiguing task. Single-centered spatial patterns were predominant in both tasks (pre-fatigue: n = 22/41; post-fatigue: n = 19/41), with no evidence of an association between the spatial patterns and tasks (γ = 0.237, 95%CI = [-0.338; 0.542]). CONCLUSIONS:Lower limb muscle fatigability increases postural instability, but it is not associated with changes in movement strategies for balance control in the upright stance. 10.1016/j.humov.2020.102588
    Comparison of core neuromuscular control and lower extremity postural stability in athletes with and without shoulder injuries. Pontillo Marisa,Butowicz Courtney M,Ebaugh David,Thigpen Charles A,Sennett Brian,Silfies Sheri P Clinical biomechanics (Bristol, Avon) BACKGROUND:The kinetic chain theory is widely used as a rationale for the inclusion of core stability training in athletes. Core stability (muscle capacity and neuromuscular control) impairments may result in less than optimal performance and abnormal force dissipation to the shoulder complex that could lead to shoulder injuries. However, a paucity of literature exists to support this relationship, and no previous studies have investigated the relationship between isolated core neuromuscular control and shoulder injuries. Additionally, lower extremity postural stability has been associated with athletic function and may also be associated with shoulder injuries. The purpose of this study was to compare biomechanical measures of isolated core neuromuscular control and lower extremity postural stability between athletes with and without non-traumatic shoulder injuries. METHODS:Eighty athletes (55 males, age: 21.2 ± 3.3 years, 40 with a current shoulder injury) completed biomechanical measures of isolated core neuromuscular control and lower extremity postural stability. Athletes were matched by age, gender, body mass index, and sport type. MANOVAs were used to assess differences between measures of core neuromuscular control and lower extremity postural stability between groups. FINDINGS:There were no statistically significant differences between athletes with and without shoulder injuries for the static core neuromuscular control measures, F(4,75) = 0.45, P = 0.78, η = 0.02; dynamic core neuromuscular control measures, F(4,75) = 0.81, P = 0.52, η = 0.04; or lower extremity postural stability measures, F(8,61) = 0.85, P = 0.56, η = 0.10. INTERPRETATION:Although core stability is widely incorporated in rehabilitation of athletes with shoulder injuries, athletes with current non-traumatic shoulder injuries may not present with impairments in core neuromuscular control or lower extremity postural stability. 10.1016/j.clinbiomech.2019.11.008
    The Effects of Tai Chi Chuan Versus Core Stability Training on Lower-Limb Neuromuscular Function in Aging Individuals with Non-Specific Chronic Lower Back Pain. Zou Liye,Zhang Yanjie,Liu Yang,Tian Xiaopei,Xiao Tao,Liu Xiaolei,Yeung Albert S,Liu Jing,Wang Xueqiang,Yang Qing Medicina (Kaunas, Lithuania) : For this paper, we aimed to investigate the effects of Tai Chi Chuan (TCC) versus the Core Stability Training (CST) program on neuromuscular function (NF) in the lower extremities among aging individuals who suffered from non-specific chronic lower back pain (NLBP). Regarding the design, during a 12-week intervention, a single-blinded randomized controlled trial was used to compare two intervention groups with a control group on the parameters of NF. : Forty-three Chinese community-dwellers were randomly assigned into two intervention groups (three sessions per week, with each session lasting 60 min in TCC and CST) and a control group. The patient-based Visual Analogue Scale (VAS) was used to measure the level of perceived pain, while parameters of NF as primary outcomes were measured by the Biodex System 3 Isokinetic Dynamometer. : For the knee joint, we observed significant differences in the endurance of left extension at a speed of 60°/s: (1) between TCC and control groups ( < 0.01); (2) between CST and control groups ( < 0.01). For the ankle joint, significant differences between CST and control groups were observed on the peak torque of left dorsiflexion ( < 0.05) and the endurance of the left plantar flexion at a speed of 60°/s ( < 0.05). In addition, we observed a significant difference between TCC and control groups in the endurance of the right plantar flexion ( < 0.05). : Chen-style TCC and CST were found to have protective effects on NF in aging individuals with NLBP, while alleviating non-specific chronic pain. 10.3390/medicina55030060
    Impaired Core Stability as a Risk Factor for the Development of Lower Extremity Overuse Injuries: A Prospective Cohort Study. De Blaiser Cedric,De Ridder Roel,Willems Tine,Vanden Bossche Luc,Danneels Lieven,Roosen Philip The American journal of sports medicine BACKGROUND:Core stability has been suggested to influence lower extremity functioning and might contribute to the development of lower extremity overuse injuries. However, prospective studies to investigate this relationship are limited. PURPOSE:To research the role of different components of core stability as risk factors for the development of lower extremity overuse injuries. STUDY DESIGN:Cohort study; Level of evidence, 2. METHODS:A total of 142 first-year physical education students participated in this study. They were tested in 2015 and were prospectively followed for 1.5 years by means of a multilevel injury registration method. Three participants were excluded owing to physical complaints during testing. As such, 139 participants were included in the statistical analysis. At baseline, dynamic postural control, isometric core and hip muscle strength, core muscle endurance, core neuromuscular control and proprioception, and functional movement were measured for all participants. Competing risk regression analyses were performed to identify significant contributors to the development of lower extremity overuse injuries. RESULTS:During the follow-up period, 34 (24%) of the 139 participants developed a lower extremity overuse injury. Significant predictive effects for an overuse injury were found for an increased side-by-side difference in dynamic postural control ( P = .038), decreased isometric hip extension:flexion strength ratio ( P = .046), and decreased abdominal core muscle endurance ( P = .032). CONCLUSION:This study identified measures for dynamic postural control, core muscle strength, and core muscle endurance as significant risk factors for the development of overuse injuries after statistical model building. However, core neuromuscular control and proprioception and functional movement might not allow clinicians to identify patients at risk. These accessible, reliable screening tools could be used in clinical practice with regard to screening and injury prevention for overuse injuries. Injury prediction based on this model needs to be done with caution given the low relative predictive accuracy (53%). 10.1177/0363546519837724
    Electromyographic patterns of tibialis posterior and related muscles when walking at different speeds. Murley George S,Menz Hylton B,Landorf Karl B Gait & posture The effect of walking speed on superficial lower limb muscles, such as tibialis anterior and triceps surae, is well established. However, there are no published data available for tibialis posterior - a muscle that plays an important role in controlling foot motion. The purpose of this study was to characterise the electromyographic timing and amplitude of selected lower limb muscles across five walking speeds. Thirty young adults were instructed to walk barefoot while electromyographic activity was recorded from tibialis posterior and peroneus longus via intramuscular electrodes, and medial gastrocnemius and tibialis anterior via surface electrodes. At faster walking speeds, peak electromyographic amplitude increased systematically during the contact and midstance/propulsion phases. Changes in the time of peak amplitude were also observed for tibialis posterior, tibialis anterior and peroneus longus activity; however, these were muscle and phase specific. During contact phase, peak electromyographic amplitude for tibialis posterior and peroneus longus was similar across very slow to slow walking speeds. During midstance/propulsion phase, peak electromyographic amplitude for tibialis posterior and medial gastrocnemius was similar across very slow to slow walking speeds. These findings may reflect a relatively higher than expected demand for peroneus longus and tibialis posterior to assist with medio-lateral foot stability at very slow speeds. Similarly, peak amplitude of medial gastrocnemius was also relatively unchanged at the very slow speed, presumably to compensate for the reduced forward momentum. The data presented in this study may serve as a reference for comparing similarly matched participants with foot deformity and/or pathological gait. 10.1016/j.gaitpost.2014.01.018
    Effects of selective strengthening of tibialis posterior and stretching of iliopsoas on navicular drop, dynamic balance, and lower limb muscle activity in pronated feet: A randomized clinical trial. Alam Farhan,Raza Shahid,Moiz Jamal Ali,Bhati Pooja,Anwer Shahnawaz,Alghadir Ahmad The Physician and sportsmedicine : Flexibility and strength are compromised in pronated feet, which could in turn lead to alteration of the dynamic balance and muscle activity in the lower extremities. This study aimed to analyze the effects of selective tibialis posterior strengthening and iliopsoas stretching on navicular drop, dynamic balance, and lower limb muscle activity in young adults with pronated feet. : Twenty-eight participants with pronated feet were randomly assigned to either the stretching and strengthening group ( = 14) or the conventional exercise group ( = 14). The stretching and strengthening group performed tibialis posterior strengthening exercises and iliopsoas stretching three times a week for 6 weeks in addition to the conventional towel curl exercises. The conventional exercise group performed towel curl exercises only. Navicular drop, dynamic balance, and lower limb muscle activity were assessed at baseline and post-intervention. A mixed model analysis of variance was performed to test the study hypothesis. : Significant group effects for the activity of tibialis anterior ( = 0.003) and abductor hallucis muscle ( = 0.010), as well as for the posterolateral ( = 0.036) and composite reach scores ( = 0.018), were detected. Significant group × time interactions were observed for naviculardrop ( < 0.001), all dynamic balance components ( < 0.001), and the activity of tibialis anterior ( < 0.001) and abductor hallucis ( < 0.001). : This study demonstrated that inclusion of selective tibialis posterior strengthening and iliopsoas stretching in addition to the conventional towel curl exercise program could improve important clinical outcomes, such as navicular drop, muscle activity, and dynamic balance in flatfeet. 10.1080/00913847.2018.1553466