Effects of unilateral leg weight perturbation intensity on spatiotemporal gait parameter symmetry and lower limb muscle activity: An exploratory laboratory study in healthy adults.

Individuals exhibit significant variability in their ability to adapt locomotor skills, with some adapting quickly and others more slowly. Differences in brain activity likely contribute to this variability, but direct neural evidence is lacking. We investigated individual differences in electrocortical activity that led to faster locomotor adaptation rates. We recorded high-density electroencephalography while young, neurotypical adults adapted their walking on a split-belt treadmill and grouped them based on how quickly they restored their gait symmetry. Results revealed unique spectral signatures within the posterior parietal, bilateral sensorimotor, and right visual cortices that differ between fast and slow adapters. Specifically, fast adapters exhibited lower alpha power in the posterior parietal and right visual cortices during early adaptation, associated with quicker attainment of steady-state step length symmetry. Decreased posterior parietal alpha may reflect enhanced spatial attention, sensory integration, and movement planning to facilitate faster locomotor adaptation. Conversely, slow adapters displayed greater alpha and beta power in the right visual cortex during late adaptation, suggesting potential differences in visuospatial processing. Additionally, fast adapters demonstrated reduced spectral power in the bilateral sensorimotor cortices compared with slow adapters, particularly in the theta band, which may suggest variations in perception of the split-belt perturbation. These findings suggest that alpha and beta oscillations in the posterior parietal and visual cortices and theta oscillations in the sensorimotor cortex are related to the rate of gait adaptation.

The main goal was to investigate changes in muscle activity and joint moments related to step length (SL) symmetry improvements in individuals poststroke following repeated split-belt treadmill (SBT) walking. Twelve individuals with a first unilateral cerebral stroke presenting initial SL asymmetry (ratio = 1.10–2.05), and mean time post stroke 23 (SD 24.7 months) were included. Participants were trained during six sessions of SBT walking using an error-augmentation protocol. The training resulted in a reduction in SL asymmetry during walking over ground retained over 1-month post-training (p = 0.002). Significant increases in SL and joint moments (plantarflexors: 20–60%, knee flexors: 20–60% and hip extensors: 0–20% of the gait cycle) were observed on the side trained on the fast belt (effect size from 0.41 to 0.60). The improvement in SL symmetry was observed with an increase in plantarflexion joint moment symmetry. Changes in muscle activity varied among participants. In contrast to previous findings with a single exposure to SBT-training, our results showed no negative effects on paretic plantarflexors when walking over ground after repeated exposure to SBT walking. These findings justify larger trials to gain more solid information on the current protocol which appears as an efficient training for long-term recovery on SL asymmetry and on affected plantarflexors.

Comparing the effects of adapting to a weight on one leg during treadmill and overground walking: A pilot study

Walking speed, unilateral leg loading, and step symmetry in young adults

Muscle coordination patterns in regulation of medial gastrocnemius activation during walking

Effects of restraining forces on propulsion and other gait characteristics during treadmill walking post-stroke.

(1) Background: Squatting is one of the common closed-kinetic chain (CKC) exercises for knee rehabilitation. Some patients cannot perform squatting exercises on land occasionally due to knee pain. Several studies had suggested that lower limb muscle activities are lower in water than on land while performing CKC exercises. The purpose of this study is to investigate the surface electromyography (sEMG) activities of Rectus femoris (RF) and Biceps femoris (BF) muscles when doing a squatting exercise in water and on land. (2) Methods: This was a cross-sectional experimental study. A total of 20 healthy participants (10 males, 10 females) were recruited by convenience sampling. The sEMG of RF and BF muscles in water and on land were collected and the knee motions were videotaped. Participants were instructed to perform closed kinetic-chain back squatting exercises at a specific speed (30 beats per minute) in water and on land at angular speed of 45°/s. Eight repetitions of the squatting exercise (0–90° knee flexion) were performed. The mean percentage maximal voluntary contraction (%MVC) between two muscles was compared in two conditions. The %MVC of RF and BF muscles at different specific knee flexion angles (30°, 60° and 90° knee flexion) was also identified. (3) Result: Muscle activities of RF (p = 0.01) and BF (p < 0.01) muscles were significantly lower in water than on land. The %MVC of RF and BF muscles was found to be 15.01% and 10.68% lower in water than on land respectively. For different knee angle phases, the differences in %MVC between land and water had significant difference for both RF muscles and BF muscles. (4) Conclusion: This study found a difference of mean percentage MVC of RF and BF muscles between land and water in different phases of squatting. The water medium reduced the two muscles’ activities to a similar extent. The result showed that the aquatic environment allows an individual to perform squatting with less muscle activation which may serve as an alternative knee exercise option for patients who encounter difficulty in land squatting due to lower limb muscle weakness or a high level of knee pain.

This study assessed muscle activity (root mean square, RMS, and median frequency, MDF) to evaluate the acute response to blood flow restriction (BFR) resistance exercise (RE) and conventional moderate intensity (MI) RE. We also performed exploratory analyses of differences based on sex and exercise-induced hypoalgesia (EIH). Fourteen asymptomatic individuals performed four sets of unilateral leg press with their dominant leg to volitional fatigue under two exercise conditions: BFR RE and MI RE. Dominant side rectus femoris (RF) and vastus lateralis (VL) muscle activity were measured using surface electromyography (sEMG) through exercise. RMS and MDF were calculated and compared between conditions and timepoints using a linear mixed model. Pressure pain thresholds (PPT) were tested before and immediately after exercise and used to quantify EIH. Participants were then divided into EIH responders and nonresponders, and the differences on RMS and MDF were compared between the two groups using Hedges' g. RMS significantly increased over time (RF: p = 0.0039; VL: p = 0.001) but not between conditions (RF: p = 0.4; VL: p = 0.67). MDF decreased over time (RF: p = 0.042; VL: p < 0.001) but not between conditions (RF: p = 0.74; VL: p = 0.77). Consistently lower muscle activation was found in females compared with males (BRF, RF: g = 0.63; VL, g = 0.5. MI, RF: g = 0.72; VL: g = 1.56), with more heterogeneous findings in MDF changes. For BFR, EIH responders showed greater RMS changes (Δ RMS) (RF: g = 0.90; VL: g = 1.21) but similar MDF changes (Δ MDF) (RF: g = 0.45; VL: g = 0.28) compared to nonresponders. For MI, EIH responders demonstrated greater increase on Δ RMS (g = 0.61) and decrease on Δ MDF (g = 0.68) in RF but similar changes in VL (Δ RMS: g = 0.40; Δ MDF: g = 0.39). These results indicate that when exercising to fatigue, no statistically significant difference was observed between BFR RE and conventional MI RE in Δ RMS and Δ MDF. Lower muscle activity was noticed in females. While exercising to volitional fatigue, muscle activity may contribute to EIH.

Many theories of motor control suggest that we select our movements to reduce energy use. However, it is unclear whether this process underlies short-term motor adaptation to novel environments. Here we asked whether adaptation to walking on a split-belt treadmill leads to a more economical walking pattern. We hypothesized that adaptation would be accompanied by a reduction in metabolic power and muscle activity and that these reductions would be temporally correlated. Eleven individuals performed a split-belt adaptation task where the belt speeds were set at 0.5 and 1.5 m s(-1). Adaptation was characterized by step length symmetry, which is the normalized difference in step length between the legs. Metabolic power was calculated based on expired gas analysis, and surface EMG was used to record the activity of four bilateral leg muscles (tibialis anterior, lateral gastrocnemius, vastus lateralis and biceps femoris). All participants initially walked with unequal step lengths when the belts moved at different speeds, but gradually adapted to take steps of equal length. Additionally, net metabolic power was reduced from early adaptation to late adaptation (early, 3.78 ± 1.05 W kg(-1); and late, 3.05 ± 0.79 W kg(-1); P < 0.001). This reduction in power was also accompanied by a bilateral reduction in EMG throughout the gait cycle. Furthermore, the reductions in metabolic power occurred over the same time scale as the improvements in step length symmetry, and the magnitude of these improvements predicted the size of the reduction in metabolic power. Our results suggest that increasing economy may be a key criterion driving locomotor adaptation.

Split-belt treadmill walking allows researchers to understand how new gait patterns are acquired. Initially, the belts move at two different speeds, inducing asymmetric step lengths. As people adapt their gait on a split-belt treadmill, left and right step lengths become more symmetric over time. Upon returning to normal walking, step lengths become asymmetric in the opposite direction, indicating deadaptation. Then, upon re-exposure to the split belts, step length asymmetry is less than the asymmetry at the start of the initial exposure, indicating readaptation. Changes in step length symmetry are driven by changes in step timing and step position asymmetry. It is critical to understand what factors can promote step timing and position adaptation and therefore influence step length asymmetry. There is limited research regarding the role of visual feedback to improve gait adaptation. Using visual feedback to promote the adaptation of step timing or position may be useful of understanding temporal or spatial gait impairments. We measured gait adaptation, deadaptation, and readaptation in twenty-nine healthy young adults while they walked on a split-belt treadmill. One group received no feedback while adapting; one group received asymmetric real-time feedback about step timing while adapting; and the last group received asymmetric real-time feedback about step position while adapting. We measured step length difference (non-normalized asymmetry), step timing asymmetry, and step position asymmetry during adaptation, deadaptation, and readaptation on a split-belt treadmill. Regardless of feedback, participants adapted step length difference, indicating that walking with temporal or spatial visual feedback does not interfere with gait adaptation. Compared to the group that received no feedback, the group that received temporal feedback exhibited smaller early deadaptation step position asymmetry (p = 0.005). There was no effect of temporal or spatial feedback on step timing. The feedback groups adapted step timing and position similarly to walking without feedback. Future work should investigate whether asymmetric visual feedback also results in typical gait adaptation in populations with altered step timing or position control.

The vestibular influence on human walking is phase-dependent and modulated across both limbs with changes in locomotor velocity and cadence. Using a split-belt treadmill, we show that vestibular influence on locomotor activity is modulated independently in each limb. The independent vestibular modulation of muscle activity from each limb occurs rapidly at the onset of split-belt walking, over a shorter time course relative to the characteristic split-belt error-correction mechanisms (i.e. muscle activity and kinematics) associated with locomotor adaptation. Together, the present results indicate that the nervous system rapidly modulates the vestibular influence of each limb separately through processes involving ongoing sensory feedback loops. These findings help us understand how vestibular information is used to accommodate the variable and commonplace demands of locomotion, such as turning or navigating irregular terrain. During walking, the vestibular influence on locomotor activity is phase-dependent and modulated in both limbs with changes in velocity. It is unclear, however, whether this bilateral modulation is due to a coordinated mechanism between both limbs or instead through limb-specific processes that remain masked by the symmetric nature of locomotion. Here, human subjects walked on a split-belt treadmill with one belt moving at 0.4ms-1 and the other moving at 0.8ms-1 while exposed to an electrical vestibular stimulus. Muscle activity was recorded bilaterally around the ankles of each limb and used to compare vestibulo-muscular coupling between velocity-matched and unmatched tied-belt walking. In general, response magnitudes decreased by ∼20-50% and occurred ∼13-20% earlier in the stride cycle at the higher belt velocity. This velocity-dependent modulation of vestibular-evoked muscle activity was retained during split-belt walking and was similar, within each limb, to velocity-matched tied-belt walking. These results demonstrate that the vestibular influence on ankle muscles during locomotion can be adapted independently to each limb. Furthermore, modulation of vestibular-evoked muscle responses occurred rapidly (∼13-34 strides) after onset of split-belt walking. This rapid adaptation contrasted with the prolonged adaptation in step length symmetry (∼128 strides) as well as EMG magnitude and timing (∼40-100 and ∼20-70 strides, respectively). These results suggest that vestibular influence on ankle muscle control is adjusted rapidly in sensorimotor control loops as opposed to longer-term error correction mechanisms commonly associated with split-belt adaptation. Rapid limb-specific sensorimotor feedback adaptation may be advantageous for asymmetric overground locomotion, such as navigating irregular terrain or turning.

Running with body weight support (BWS) (e.g., running on a lower positive pressure treadmill) has been used for physical fitness enhancement. Nevertheless, gait mechanics of running with BWS is not fully understood. PURPOSE: To investigate influence of stride frequency (SF) manipulation on muscle activity during running at different BWS conditions. METHODS: Nineteen subjects (23.8±4.1 years) ran on a lower body positive pressure treadmill at their preferred running speed (PS) for different BWS conditions (i.e., 0%, 50%, and 80% of BWS conditions). The SF conditions consist of running at preferred SF (PSF), PSF+10%, and PSF-10%. Muscle activity from the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GA) were measured. In addition, rating of perceived exertion (RPE) and SF were measured. Muscle activity, RPE, and SF were analyzed using a 3 (mode) x 3 (BWS) repeated measures analysis of variance (ANOVA) (α = 0.05). PS was analyzed using a one-way repeated measures ANOVA (α = 0.05). RESULTS: Muscle activity (RF, BF, TA, and GA), RPE, and SF were not influenced by the interaction of BW support and SF (P>0.05). Muscle activity from the RF, TA, and GA were different between BWS conditions (P<0.001). Specifically, muscle activity from the RF, TA, and GA were lower with increasing BWS (e.g., a decrease of 26%~46% between 80%BWS and 0%BWS conditions). Muscle activity from the RF, BF, and TA were different between SF conditions (P<0.05). For example, RF muscle activity during running at PSF was 11%~18% lower than when running at PSF+10%. Additionally, BF muscle activity during running was higher with increasing SF (e.g., a 20% increase in SF resulted in 12%~27% increase in the BF muscle activity). RPE was not different between BWS conditions (P>0.05) and between SF conditions (P>0.05). SF was different between BWS conditions (P<0.001) and between SF conditions (P<0.001). For example, SF was lower with increasing BWS (e.g., a decrease of 15% between 80%BWS and 0%BWS conditions). PS was higher with increasing BWS (9.8±2.1 km/h, 11.0±2.6 km/h, and 11.8±2.8 km/h for 0%, 50%, and 80% of BWS conditions, respectively: P<0.001). CONCLUSION: These observations suggest that a change in SF may influence muscle activity (i.e., RF and TA) during running, regardless of BWS.

Background and Aims Hip dysplasia is a pathological condition of the hip joint characterized by abnormal acetabular geometry, resulting in insufficient femoral head coverage. This inadequate coverage, along with the relative lateral displacement of the femoral head, reduces the articular contact surface, alters intra-articular loading, and increases mechanical stress throughout the hip joint. Such stress accelerates cartilage wear, making patients more susceptible to early-onset hip osteoarthritis. Muscle forces and joint reaction forces are the primary mechanical factors in hip joint loading, and these forces are altered in patients with hip dysplasia. Examining the relationship between muscle activity, gait patterns, and joint contact forces can enhance the understanding of the pathophysiological mechanisms underlying hip dysplasia and aid in developing more effective treatment strategies. This study aims to analyze these interactions and identify factors influencing the improvement of hip joint function in individuals with hip dysplasia. The findings and insights derived from this research can be applied in clinical settings to aid muscle-strengthening exercises, thereby enhancing rehabilitation and clinical management of such patients. The primary objective of this study is to investigate and compare the activity of pelvic girdle muscles in individuals with hip dysplasia and healthy controls using musculoskeletal modeling. Methods In this study, 10 healthy individuals (mean age: 23±1.68 years) and 10 patients with left-side hip dysplasia (mean age: 25±2.54 years) were recruited and voluntarily participated. The study aimed to analyze and compare the activity of the gluteus medius, gluteus maximus, rectus femoris, and tensor fascia lata (TFL) muscles in the two groups. The OpenSim software, version 4.4 utilized gait data from healthy and dysplastic participants to calculate and analyze muscle activity for further investigation. Results No significant differences were observed in the demographic characteristics of participants between the healthy and dysplasia groups (P&gt;0.05). However, the significance level of muscle activity in the gluteus medius, TFL, and rectus femoris muscles was &lt;0.05. The gluteus medius and TFL muscles exhibited significantly higher activity in individuals with hip dysplasia compared to the control group. Additionally, the gluteus maximus muscle activity increased relative to the control group. Conversely, the rectus femoris muscle demonstrated a decrease in activity. Conclusion This study demonstrated that individuals with hip dysplasia exhibit elevated muscle activation levels during the gait cycle compared to healthy controls. Furthermore, the GRFs and center of pressure dynamics showed distinct patterns in the dysplasia group. The altered biomechanics of hip dysplasia shorten the muscle moment arm, necessitating greater muscle forces to achieve the required joint torques. These findings highlight that increased muscle activity in hip dysplasia impairs movement efficiency and elevates intra-articular forces. Therefore, developing targeted therapeutic interventions aimed at optimizing biomechanical function and mitigating excessive muscle activation is crucial for effectively managing hip dysplasia.

A change in running speed influences gait mechanics of running. PURPOSE: The purpose of this study was to investigate the influence of a change in running speed on muscle activity during forward and backward running at different body weight support (BWS) conditions. METHODS: Eleven participants (29.7 ± 12.3 years) ran forward and backward on a lower body positive pressure treadmill at 0%BWS, 20%BWS, and 50%BWS conditions. The running speed conditions consisted of forward and backward running at preferred speed (PS), PS+10%, and PS-10%. Muscle activity from the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius and stride frequency were measured. Muscle activity and stride frequency were analyzed using a 2 (running direction) x 3 (BWS) x 3 (running speed) repeated measures analysis of variance (α = 0.05). RESULTS: Muscle activity from the rectus femoris (P<0.01) and gastrocnemius (P<0.01) were significantly different between running speeds. For example, muscle activity from the rectus femoris (P<0.05) and gastrocnemius (P<0.05) during running at PS were significantly greater than when running at PS-10%, regardless of running direction and BWS. Furthermore, muscle activity from the rectus femoris (P<0.01) and gastrocnemius (P<0.05) during running at PS+10% were significantly greater than when running at PS, regardless of running direction and BWS. Stride frequency was influenced by the interaction of running direction and running speed (P<0.05). Using the pairwise comparisons, stride frequency during running at PS was significantly higher than that of running at PS-10% only when running forward and backward at 0%BWS (e.g., 84.5 strides/min and 82.0 strides/min for backward running at PS and PS-10% conditions, respectively: P<0.05). Furthermore, stride frequency during running at PS+10% was significantly higher than that of running at PS during forward and backward running at 0%BWS (P<0.05). CONCLUSIONS: Muscle activity from the rectus femoris and gastrocnemius during running may increase with increasing running speed, regardless of BWS and running direction. However, unique biomechanical strategies for the increased muscle activity from the lower extremity may exist for running with BWS.

Prolonged activity of knee extensors and dorsal flexors is associated with adaptations in gait in diabetes and diabetic polyneuropathy