Adolescent children experience a critical developmental period marked by rapid biological changes.
Research question
To describe the longitudinal changes in postural control that occur in adolescent ...boys and girls before the age of peak height velocity (PHV).
Here, to address the gap of knowledge, we compared the postural control and activation strategies of the muscles that control the ankle joint in twenty-three boys (age 12.5 ± 0.29) and twenty-one girls (age 10.5 ± 0.32). They performed easy (two legs) and difficult (two legs-eyes closed; one leg) postural balance tasks at 18 and 9 months before PHV and at PHV. We quantified the center of pressure (COP) displacements in the anterior-posterior (AP) and mediolateral (ML) directions and electromyographic (EMG) activity of tibialis anterior (TA) and medial gastrocnemius (MG) muscles.
Boys exhibited greater AP and ML COP displacement than girls only for the one leg task (difficult task). Although boys and girls had similar postural control 18 months prior to PHV, girls exhibited lesser COP displacement at 9 months before PHV, which related to greater TA-MG coactivation (R2 = 0.26; p < 0.01). In contrast, postural control was not different between boys and girls with an easy balance task (two legs) performed with eyes open and closed. Rather, we found that all children improved their COP displacement in the ML direction with maturity and both AP and ML COP was significantly lower with eyes open.
These findings provide novel evidence that postural control is superior in early adolescent girls than boys 9 months prior to PHV, likely associated with an earlier maturation of muscle coordination.
•Postural control is better in early adolescent girls than boys.•Increased coactivation in ankle joint muscles is related with better postural control.•Removal of visual feedback impairs postural control of early adolescents.
Falls in older adults generally occur during unpredictable situations. Controlling posture through fine-tuned muscle force before and after falls is necessary to avoid serious injuries. However, ...details regarding force control among older adults during unpredictable situations are unclear. This study determined the features of force control in a random force-tracking task among older adults.
Ten healthy older adults (67–76 years) and eight healthy young adults (20–23 years) participated in three force-tracking tasks with ankle plantar flexion: low-range (LR), high-range (HR), and pseudo-random (PR) force tasks. Force control ability was assessed using the root mean square error (RMSE) between the target and muscle forces produced by the participants. Muscle activities from the lateral head of the gastrocnemius and the tibialis anterior during each task were measured using surface electromyography to calculate the co-contraction index (CCI).
In all tasks, older adults (RMSEs: 1.09–3.70, CCIs: 29.4–56.4) had a significantly greater RMSEs and CCIs than young adults (RMSEs: 0.49–1.83, CCIs: 11.7–20.6; all, p < 0.05). The RMSEs during force generation were significantly greater than those during force release (LR: p < 0.01, HR: p < 0.05), except for the random force-tracking task in older adults. CCIs during the force release phase in both groups (older adults: 27.8–56.4, young adults: 15.0–20.6) were consistently greater than those during force generation (older adults: 24.5–50.4, young adults: 11.7–17.2). CCIs in force-tracing tasks differed in older adults, whereas those in the random force-tracing task increased. RMSEs and CCIs in the random and LR force-tracing tasks were significantly negatively correlated with the functional reach test (all: r > 0.5, p < 0.05).
Force control in older adults declines in low-band and random muscle force output. Moreover, increased CCIs in older adults are particularly pronounced during unpredictable situations.
•Older adults show increased force error during force tracking.•Force release control in older adults decreases in unpredictable situations.•Motor performance in unpredictable tasks correlates with balance ability.
Anticipatory postural adjustments (APAs) are the coordinated muscular activities that precede the voluntary movements to counteract the associated postural perturbations. Many studies about gait ...initiation call APAs those activities that precede the heel-off of the leading foot, thus taking heel-off as the onset of voluntary movement. In particular, leg muscles drive the center of pressure (CoP) both laterally, to shift the body weight over the trailing foot and backward, to create a disequilibrium torque pushing forward the center of mass (CoM). However, since subjects want to propel their body rather than lift their foot, the onset of gait should be the CoM displacement, which starts with the backward CoP shift. If so, the leg muscles driving such a shift are the prime movers. Moreover, since the disequilibrium torque is mechanically equivalent to a forward force acting at the pelvis level, APAs should be required to link the body segments to the pelvis: distributing such concentrated force throughout the body would make all segments move homogeneously. In the aim of testing this hypothesis, we analyzed gait initiation in 15 right-footed healthy subjects, searching for activities in trunk muscles that precede the onset of the backward CoP shift. Subjects stood on a force plate for about 10 s and then started walking at their natural speed. A minimum of 10 trials were collected. A force plate measured the CoP position while wireless probes recorded the electromyographic activities. Recordings ascertained that at gait onset APAs develop in trunk muscles. On the right side, Rectus Abdominis and Obliquus Abdominis were activated in 11 and 13 subjects, respectively, starting on average 33 and 54 ms before the CoP shift; Erector Spinae (ES) at L2 and T3 levels was instead inhibited (9 and 7 subjects, 104 and 120 ms). On the contralateral side, the same muscles showed excitatory APAs (abdominals in 11 and 12 subjects, 27 and 82 ms; ES in 10 and 7 subjects, 75 and 32 ms). The results of this study provide a novel framework for distinguishing postural from voluntary actions, which may be relevant for the diagnosis and rehabilitation of gait disorders.
One of the most common symptoms in stroke patients is spasticity. The aims were to investigate the effects of anodal trans-cranial direct current stimulation (a-tDCS) over the affected primary motor ...cortex (M1) on ankle plantar flexor spasticity and dorsiflexor muscle activity in stroke patients. The design of this study was a randomized sham-controlled clinical trial. Thirty-two participants with stroke were randomly assigned to three groups (experimental, sham, control groups). Participants in the experimental and sham groups received 10-session 20-min M1 a-tDCS concurrent with physical therapy (PT), while the control group only received 10-session PT. All groups were instructed to perform home stretching exercises and balance training. Berg Balance Scale (BBS), Modified Ashworth Scale (MAS) of plantar flexors, and EMG activity of lateral gastrocnemius (LG) and tibialis anterior (TA) were recorded during active and passive ankle dorsiflexion immediately and 1 month after interventions. A significant reduction was shown in MAS and EMG activity of LG during dorsiflexion, immediately and 1 month after intervention in the M1 a-tDCS group (
p
<0.001). BBS also significantly increased only in the M1 a-tDCS group (
p
<0.001). In addition, EMG activity of TA during active dorsiflexion increased immediately and 1 month after intervention in the M1 a-tDCS group (
p
<0.001). However, in the sham and control groups, EMG activity of TA increased immediately (
p
<0.001), while this was not maintained 1 month after intervention (
p
>0.05). PT concurrent with M1 a-tDCS can significantly prime lasting effects of decreasing LG spasticity, increasing TA muscle activity, and also balance in stroke patients.
The purpose of this study was to analyze the activity of ankle muscles during normal gait by simulation method using the human musculoskel-etal model. The equipment used in this study was ...three-dimensional motion capture system and force platform, and OpenSim was used for simulation. Collected data was scaled to Gait2392 that is the human musculoskeletal simulation model using in the OpenSim. Tibialis anteri-or (TA) worked as a major muscle during gait, producing a higher force than other muscles. Main muscles contributing to propulsion were gas-trocnemius medial head (GMH) and soleus (SOL) with their maximum forces appear to be more than 1.5 times the body weight. GMH and SOL showed cooperation for maintaining propulsion around left foot initial contact in the gait cycle. This study has shown a difference between activation and force pattern. The peak-activation of the TA and extensor digitorum longus (EDL) was similarly shown to be around 0.8 in the initial double stance, but the peak-force produced by these muscles in the same period showed a difference with 0.4 Newton/body weight higher in TA than in EDL. We suggest that when assessing muscle contribution to gait, it would be reasonable to consider the force generated because the human movement was generated by the mechanical net force of muscles.
Ankle and foot injuries are common among athletes and physically active individuals. The most common residual disability, ankle sprain, is characterized by instability along with postural sway. If ...the supporting structures around a joint become lax, posture stability and balance are also affected. Previous studies have examined muscle stiffness and elasticity and postural sway separately; however, the relationship between these factors is yet unknown. It is well known that the levels of sex hormones, especially estrogen, change in women over the phase of the menstrual cycle. Therefore, this study examined the relationship between the mechanical properties of tissue and balance activity using a non-invasive digital palpation device to determine if they undergo any changes over the menstrual cycle in young women. Sixteen young women with regular menstrual cycles completed the study. Tone, stiffness, and elasticity of the ankle muscles (lateral gastrocnemius, peroneus longus, and tibialis anterior) were measured using a non-invasive digital palpation device. Postural sway was recorded while the participants performed balance tasks during ovulation and menstruation. Significantly greater posture sway characteristics and ankle muscle elasticity were found during ovulation than during menstruation; lower tone and stiffness of the ankle muscles were observed at ovulation (p < 0.05). Additionally, weak-to-strong relationships between ankle muscle mechanical properties and postural sway characteristics were found (p < 0.05). These results suggest the effect of estrogen on human connective tissues. We therefore postulate that estrogen increases joint and muscle laxity and affects posture stability according to the phase of the menstrual cycle.
The objective of this study was to investigate the effect of obesity on markers of neuromuscular fatigability of ankle muscles and their potential relationships with postural control capacities.
Two ...groups: non-obese control group (CG; n = 15; age = 40.1 ± 13.9 years; BMI = 23.9 ± 2.8 kg/m2) and obese group (OG; n = 15; age = 44.2 ± 12.4 years; BMI = 42.2 ± 5.2 kg/m2), performed two postural tasks with and without vision in order to collect parameters of center of pressure (CoP) displacements; area (cm2), velocity (mm/s), length (cm) and the ratio length/area. Fatigability was estimated during 60 repeated maximal voluntary contractions of plantar (PF) and dorsal flexors (DF). The maximal force, critical force (Fcr) presenting the asymptote of the force-time evolution and rate of the force decrease (τ) were extracted. Results reported that CoP parameters were higher in OG compared to CG in all postural tasks (p < 0.05). Fcr of PF and DF were 39% and 28% lower respectively in OG compared to CG (p < 0.05). Only τ of PF was 12% lower in OG (p < 0.05). Fcr of PF was negatively correlated with the ratio length/area in OG in all postural tasks (r = 0.86 and r = 0.85, respectively, p < 0.05). We concluded that obesity is associated with a decreased Fcr of ankle muscles expressing the intensity threshold above which fatigue develops drastically. We also revealed that decreased fatigability threshold particularly that of PF, could partly explain postural control alterations in obese adults.
The purpose of this study was to determine whether the mechanical contribution of ankle muscles in the upright stance differed among young adults (YA) (n=10, age: ~24.3), elderly non-fallers (ENF) ...(n=12, age: ~77.3) and elderly fallers (EF) (n=20, age: ~80.7). Torque and electromyographic (EMG) activity were recorded on the triceps surae and tibialis anterior during maximum and submaximum contractions in the seated position. EMG activity was also recorded in subjects standing still. Plantar flexor (PF) and dorsal flexor (DF) torques generated in the upright posture were estimated from the torque–EMG relationship obtained during submaximum contractions in the seated position. Center of pressure (CoP) displacement was measured to quantify postural stability. Results showed that, in upright standing, EF generated greater ankle muscle relative torque (i.e. PF+DF torque in the upright stance/PF+DF during maximum isometric torque) than non-fallers (i.e. ENF, YA). The greater involvement of ankle muscles in EF was associated with higher CoP displacement. PF+DF torque in the upright stance was no different among the groups, but PF+DF torque during maximum effort was impaired in older groups compared with YA and was lower in EF than ENF. These results suggest that the postural stability impairment observed with aging is highly related to ankle muscle weakness.
•This study investigated the ankle muscle involvements to the upright stance in young adults, elderly non-fallers and fallers.•Elderly fallers generated greater ankle muscle relative torque than non-fallers when maintaining upright posture.•This greater contribution of ankle muscles to upright stance was associated with higher postural instability.•The postural stability impairment observed with aging is highly related to ankle muscle weakness.
Abstract Background Anticipatory postural adjustments during gait initiation have an important role in postural stability but also in gait performance. However, these first phase mechanisms of gait ...initiation have received little attention, particularly in subcortical post-stroke subjects, where bilateral postural control pathways can be impaired. This study aims to evaluate ankle anticipatory postural adjustments during gait initiation in chronic post-stroke subjects with lesion in the territory of middle cerebral artery. Methods Eleven subjects with post-stroke hemiparesis with the ability to walk independently and twelve healthy controls participated in this study. Bilateral electromyographic activity of tibialis anterior, soleus and medial gastrocnemius was collected during gait initiation to assess the muscle onset timing, period of activation/deactivation and magnitude of muscle activity during postural phase of gait initiation. This phase was identified through centre of pressure signal. Findings Post-stroke group presented only half of the tibialis anterior relative magnitude observed in healthy subjects in contralesional limb (t = 2.38, P = 0.027) and decreased soleus deactivation period (contralesional limb, t = 2.25, P = 0.04; ipsilesional limb, t = 3.67, P = 0.003) as well its onset timing (contralesional limb, t = 3.2. P = 0.005; ipsilesional limb, t = 2.88, P = 0.033) in both limbs. A decreased centre of pressure displacement backward (t = 3.45, P = 0.002) and toward the first swing limb (t = 3.29, P = 0.004) was observed in post-stroke subjects. Interpretation These findings indicate that chronic post-stroke subjects with lesion at middle cerebral artery territory present dysfunction in ankle anticipatory postural adjustments in both limbs during gait initiation.
Abstract Background People with floppy ankle muscles paresis use ankle foot orthoses to improve their walking ability. Ankle foot orthoses also limit ankle range of motion thereby introducing ...additional problems. Insight in effects of ankle foot orthoses on body functions and activities in people with floppy paretic ankle muscles aids in clinical decision making and may improve adherence. Methods Studies published before October 27th, 2014, were searched in Pubmed, Embase, Cinahl, and Cochrane Library. Studies evaluating effects of ankle foot orthoses on body functions and/or activities in people with floppy paretic ankle muscles were included. Studies solely focusing on people with spastic paretic ankle muscles were excluded. Study quality was assessed using a custom-made scale. Body functions and activities were defined according to the International Classification of Functioning, Disability and Health. Findings Twenty-four studies were included, evaluating 394 participants. Participants were grouped according to paresis type (i) dorsiflexor paresis, (ii) plantar flexor paresis, (iii) both dorsiflexor and plantar flexor paresis. Dorsal, circular, and elastic ankle foot orthoses increased dorsiflexion during swing (by 4–6°, group i). Physical comfort with dorsal ankle foot orthoses was lower than that with circular ankle foot orthoses (groups i and iii). Dorsal ankle foot orthoses increased push-off moment (by 0.2–0.5 Nm/kg), increased walking efficiency, and decreased ankle range of motion (by 12-30°, groups ii and iii). Interpretation People with dorsiflexor paresis benefit more from circular and elastic ankle foot orthoses while people with plantar flexor paresis (and dorsiflexor paresis) benefit more from dorsal ankle foot orthoses.
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