Walking involves multitasking, and many individuals with stroke exhibit dual-task interference, gait instability, and altered lower limb muscle activity even during single-task walking. This study investigated dual-task interference in individuals with stroke and its relationship to single-task walking characteristics. A total of 30 participants completed single-task and dual-task walking. Correct response rate (CRR), dual-task effect, and percentage change in walking speed were assessed using inertial sensors and surface electromyography.
The root mean square (RMS) of trunk acceleration and the sample entropy of lower limb acceleration signals were computed. Higher CRR during walking (p = 0.048) and faster walking speed under single-task conditions (p < 0.001) were observed. Mean dual-task effect was − 32.2 %. RMS, sample entropy, and co-contraction index were elevated during dual-task walking (all p < 0.001).
Changes in walking speed were associated with co-contraction index (ρ = − 0.380, p = 0.039), RMS (ρ = − 0.764, p < 0.001), and sample entropy (ρ = − 0.734, p < 0.001).
Regression analysis indicated that single-task walking speed, RMS, and sample entropy predicted instability during dual-task walking (R2 = 0.545).
These results suggest that compromised postural control during single-task walking increases susceptibility to cognitive interference, emphasizing the importance of targeted gait stability training.
{"title":"Factors influencing instability during dual-task walking in stroke patients","authors":"Ryuya Kitago , Naomichi Mizuta , Naruhito Hasui , Shu Morioka","doi":"10.1016/j.jelekin.2025.103077","DOIUrl":"10.1016/j.jelekin.2025.103077","url":null,"abstract":"<div><div>Walking involves multitasking, and many individuals with stroke exhibit dual-task interference, gait instability, and altered lower limb muscle activity even during single-task walking. This study investigated dual-task interference in individuals with stroke and its relationship to single-task walking characteristics. A total of 30 participants completed single-task and dual-task walking. Correct response rate (CRR), dual-task effect, and percentage change in walking speed were assessed using inertial sensors and surface electromyography.</div><div>The root mean square (RMS) of trunk acceleration and the sample entropy of lower limb acceleration signals were computed. Higher CRR during walking (p = 0.048) and faster walking speed under single-task conditions (p < 0.001) were observed. Mean dual-task effect was − 32.2 %. RMS, sample entropy, and co-contraction index were elevated during dual-task walking (all p < 0.001).</div><div>Changes in walking speed were associated with co-contraction index (ρ = − 0.380, p = 0.039), RMS (ρ = − 0.764, p < 0.001), and sample entropy (ρ = − 0.734, p < 0.001).</div><div>Regression analysis indicated that single-task walking speed, RMS, and sample entropy predicted instability during dual-task walking (R<sup>2</sup> = 0.545).</div><div>These results suggest that compromised postural control during single-task walking increases susceptibility to cognitive interference, emphasizing the importance of targeted gait stability training.</div></div>","PeriodicalId":56123,"journal":{"name":"Journal of Electromyography and Kinesiology","volume":"85 ","pages":"Article 103077"},"PeriodicalIF":2.3,"publicationDate":"2025-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145423547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-24DOI: 10.1016/j.jelekin.2025.103079
Manuela Besomi, Wolbert van den Hoorn, Bill Vicenzino, Paul W. Hodges
Electromyographic (EMG) recordings of the tensor fascia latae (TFL) muscle are commonly used to assess muscle activation, yet electrode type and amplitude normalisation method can influence data interpretation. This study compared surface and fine-wire EMG recordings of the TFL during dynamic step-up and step-down tasks, and examined the effect of three amplitude normalisation methods on the TFL EMG patterns: maximum voluntary isometric contraction (MVIC), peak of the mean from average across task trials, and peak of the individual trial peaks. Eight physically active participants (5 females, 3 males) performed five trials of each task with EMG recorded from the dominant leg. Two participants were excluded due to artefact contamination or absent fine-wire signals. Surface EMG demonstrated higher early activation during the step-up task compared to fine-wire EMG (p = 0.013); a difference likely attributable to crosstalk from adjacent muscles. Normalisation methods also altered the timing (time of onset) of ensemble waveforms and between-participant variability, with MVIC introducing greater variability but preserving physiological meaning, while task-based methods reduced variability but removed amplitude information. These findings highlight the contradictory results and limitations of both surface and fine-wire EMG when applied in isolation to the TFL. Rather than endorsing one technique as superior, this study provides a tutorial regarding how methodological choices can shape interpretation and potentially lead to misleading conclusions. Future studies incorporating intra-subject variability testing and high-density surface EMG are needed to optimise electrode placement and improve methodological reliability when studying small, anatomically complex muscles such as the TFL.
{"title":"Methodological influences on tensor fascia latae EMG during dynamic tasks: Electrode- and normalisation-dependent variability","authors":"Manuela Besomi, Wolbert van den Hoorn, Bill Vicenzino, Paul W. Hodges","doi":"10.1016/j.jelekin.2025.103079","DOIUrl":"10.1016/j.jelekin.2025.103079","url":null,"abstract":"<div><div>Electromyographic (EMG) recordings of the tensor fascia latae (TFL) muscle are commonly used to assess muscle activation, yet electrode type and amplitude normalisation method can influence data interpretation. This study compared surface and fine-wire EMG recordings of the TFL during dynamic step-up and step-down tasks, and examined the effect of three amplitude normalisation methods on the TFL EMG patterns: maximum voluntary isometric contraction (MVIC), peak of the mean from average across task trials, and peak of the individual trial peaks. Eight physically active participants (5 females, 3 males) performed five trials of each task with EMG recorded from the dominant leg. Two participants were excluded due to artefact contamination or absent fine-wire signals. Surface EMG demonstrated higher early activation during the step-up task compared to fine-wire EMG (p = 0.013); a difference likely attributable to crosstalk from adjacent muscles. Normalisation methods also altered the timing (time of onset) of ensemble waveforms and between-participant variability, with MVIC introducing greater variability but preserving physiological meaning, while task-based methods reduced variability but removed amplitude information. These findings highlight the contradictory results and limitations of both surface and fine-wire EMG when applied in isolation to the TFL. Rather than endorsing one technique as superior, this study provides a tutorial regarding how methodological choices can shape interpretation and potentially lead to misleading conclusions. Future studies incorporating intra-subject variability testing and high-density surface EMG are needed to optimise electrode placement and improve methodological reliability when studying small, anatomically complex muscles such as the TFL.</div></div>","PeriodicalId":56123,"journal":{"name":"Journal of Electromyography and Kinesiology","volume":"85 ","pages":"Article 103079"},"PeriodicalIF":2.3,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-24DOI: 10.1016/j.jelekin.2025.103080
Daan De Vlieger , Liese Bosman , Eva Swinnen , Manuela Besomi , Jeroen Aeles
Introduction
In surface electromyography, optimal electrode placement is critical. Various techniques are available for placing the electrodes appropriately, yet these are rarely assessed for accuracy, especially for electrode placement away from neighboring muscles considering the large variation in individual muscle morphology. This study evaluated triceps surae electrode placement using SENIAM recommendations and expert palpation, relative to anatomical muscle boundaries.
Methods
Electrodes were placed on the medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus of twenty-four participants following SENIAM guidelines and expert muscle palpation. Ultrasound was used to calculate the distances between electrodes and muscle boundaries at rest and during fixed-end plantar flexion at two intensities, in both plantar flexion and dorsiflexion positions.
Results
SENIAM placed the electrodes laterally (electrode-boundary distance: 0.7 ± 0.9 cm) and the expert more centrally (distance to lateral boundary: 4.1 ± 0.9 cm; medial boundary: 3.0 ± 0.9 cm) on the LG. In four participants, SENIAM placements were positioned outside the LG muscle boundary. In soleus, SENIAM placements were close to the tibial border (0.7 ± 0.4 cm). For MG, both methods performed well.
Conclusion
This study highlights limitations of the SENIAM placement protocol for the LG and soleus, and supports the use of individualized approaches to improve electrode accuracy and enhance the validity of EMG recordings.
{"title":"Assessment of common electrode placement methods for surface electromyography recordings of the triceps surae muscles","authors":"Daan De Vlieger , Liese Bosman , Eva Swinnen , Manuela Besomi , Jeroen Aeles","doi":"10.1016/j.jelekin.2025.103080","DOIUrl":"10.1016/j.jelekin.2025.103080","url":null,"abstract":"<div><h3>Introduction</h3><div>In surface electromyography, optimal electrode placement is critical. Various techniques are available for placing the electrodes appropriately, yet these are rarely assessed for accuracy, especially for electrode placement away from neighboring muscles considering the large variation in individual muscle morphology. This study evaluated triceps surae electrode placement using SENIAM recommendations and expert palpation, relative to anatomical muscle boundaries.</div></div><div><h3>Methods</h3><div>Electrodes were placed on the medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus of twenty-four participants following SENIAM guidelines and expert muscle palpation. Ultrasound was used to calculate the distances between electrodes and muscle boundaries at rest and during fixed-end plantar flexion at two intensities, in both plantar flexion and dorsiflexion positions.</div></div><div><h3>Results</h3><div>SENIAM placed the electrodes laterally (electrode-boundary distance: 0.7 ± 0.9 cm) and the expert more centrally (distance to lateral boundary: 4.1 ± 0.9 cm; medial boundary: 3.0 ± 0.9 cm) on the LG. In four participants, SENIAM placements were positioned outside the LG muscle boundary. In soleus, SENIAM placements were close to the tibial border (0.7 ± 0.4 cm). For MG, both methods performed well.</div></div><div><h3>Conclusion</h3><div>This study highlights limitations of the SENIAM placement protocol for the LG and soleus, and supports the use of individualized approaches to improve electrode accuracy and enhance the validity of EMG recordings.</div></div>","PeriodicalId":56123,"journal":{"name":"Journal of Electromyography and Kinesiology","volume":"85 ","pages":"Article 103080"},"PeriodicalIF":2.3,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145497554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The infrapatellar fat pad (IFP) plays a role in the mechano-pathology of patients with knee osteoarthritis (OA), and its morphological changes during walking may serve as an indicator for detecting the condition. However, the effects of knee muscle activation on IFP morphology during walking in patients with knee OA remain unclear. This study investigated the relationship between muscle activation and morphological changes in the IFP during walking in patients with knee OA. Twenty-two patients with knee OA were enrolled in this cross-sectional study. IFP thickness and kinematic and kinetic data were measured during walking using ultrasound imaging and a three-dimensional motion analysis system. The activities of the quadriceps and hamstring muscles were recorded simultaneously, and muscle co-contraction indices were calculated. No correlation was found between quadriceps activation and IFP parameters. By contrast, a significant negative correlation was observed between morphological changes in the IFP and lateral muscle co-contraction during the stance phase. These results suggest that co-contraction of knee muscles involves poor IFP dynamics during walking, potentially playing a role in the development of mechano-pathological changes in patients with knee OA.
{"title":"Relationship between knee muscle activation and morphological changes in the infrapatellar fat pad in patients with knee osteoarthritis during gait","authors":"Kexin Zhu , Yosuke Ishii , Akinori Nekomoto , Goki Kamei , Riko Okinaka , Takato Hashizume , Kohei Matsumura , Miharu Sugimoto , Minoru Toriyama , Yuko Nakashima , Makoto Takahashi , Nobuo Adachi","doi":"10.1016/j.jelekin.2025.103076","DOIUrl":"10.1016/j.jelekin.2025.103076","url":null,"abstract":"<div><div>The infrapatellar fat pad (IFP) plays a role in the mechano-pathology of patients with knee osteoarthritis (OA), and its morphological changes during walking may serve as an indicator for detecting the condition. However, the effects of knee muscle activation on IFP morphology during walking in patients with knee OA remain unclear. This study investigated the relationship between muscle activation and morphological changes in the IFP during walking in patients with knee OA. Twenty-two patients with knee OA were enrolled in this cross-sectional study. IFP thickness and kinematic and kinetic data were measured during walking using ultrasound imaging and a three-dimensional motion analysis system. The activities of the quadriceps and hamstring muscles were recorded simultaneously, and muscle co-contraction indices were calculated. No correlation was found between quadriceps activation and IFP parameters. By contrast, a significant negative correlation was observed between morphological changes in the IFP and lateral muscle co-contraction during the stance phase. These results suggest that co-contraction of knee muscles involves poor IFP dynamics during walking, potentially playing a role in the development of mechano-pathological changes in patients with knee OA.</div></div>","PeriodicalId":56123,"journal":{"name":"Journal of Electromyography and Kinesiology","volume":"85 ","pages":"Article 103076"},"PeriodicalIF":2.3,"publicationDate":"2025-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145402977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-18DOI: 10.1016/j.jelekin.2025.103075
Oscar Vila-Dieguez , Daniel McPherson , George Salem , Clark R. Dickerson , Andrew R. Karduna , Lori A. Michener
Background
Exercise is a first-line treatment for rotator cuff (RC) tendinopathy, but responses are variable. Defining mechanisms underlying patient improvement is necessary. This study investigated the relationship between neuromuscular factors—specifically peak force, rate of force development (RFD), and muscle activation onset—and patient-reported disability outcomes during an 8-week resistance exercise program.
Methods
51 participants with RC tendinopathy underwent assessments of peak force, RFD, and EMG muscle activation onset at baseline, 2, 4, and 8 weeks. Penn Shoulder Score measured patient-reported disability. Linear mixed-effects models assessed changes over time and the association between variables.
Results
Penn scores improved from baseline through weeks 2, 4, and 8. RFD increased in external rotation and abduction and peak force in external rotation and earlier EMG onset of deltoid and RC muscles. Baseline Penn score, increase in isometric abduction peak force from week 0 to week 2 and from week 2 to week 4 were associated with improved disability outcomes after controlling for pain during the task.
Conclusion
Several force and muscle activation variables changed after the exercise intervention, but only abduction peak force was related to patient-reported disability outcomes. This may offer added insight into individual recovery mechanisms beyond patient-reported outcomes alone.
{"title":"Relationship between changes in neuromuscular factors and disability outcomes following a resistance exercise intervention in rotator cuff tendinopathy","authors":"Oscar Vila-Dieguez , Daniel McPherson , George Salem , Clark R. Dickerson , Andrew R. Karduna , Lori A. Michener","doi":"10.1016/j.jelekin.2025.103075","DOIUrl":"10.1016/j.jelekin.2025.103075","url":null,"abstract":"<div><h3>Background</h3><div>Exercise is a first-line treatment for rotator cuff (RC) tendinopathy, but responses are variable. Defining mechanisms underlying patient improvement is necessary. This study investigated the relationship between neuromuscular factors—specifically peak force, rate of force development (RFD), and muscle activation onset—and patient-reported disability outcomes during an 8-week resistance exercise program.</div></div><div><h3>Methods</h3><div>51 participants with RC tendinopathy underwent assessments of peak force, RFD, and EMG muscle activation onset at baseline, 2, 4, and 8 weeks. Penn Shoulder Score measured patient-reported disability. Linear mixed-effects models assessed changes over time and the association between variables.</div></div><div><h3>Results</h3><div>Penn scores improved from baseline through weeks 2, 4, and 8. RFD increased in external rotation and abduction and peak force in external rotation and earlier EMG onset of deltoid and RC muscles. Baseline Penn score, increase in isometric abduction peak force from week 0 to week 2 and from week 2 to week 4 were associated with improved disability outcomes after controlling for pain during the task.</div></div><div><h3>Conclusion</h3><div>Several force and muscle activation variables changed after the exercise intervention, but only abduction peak force was related to patient-reported disability outcomes. This may offer added insight into individual recovery mechanisms beyond patient-reported outcomes alone.</div></div>","PeriodicalId":56123,"journal":{"name":"Journal of Electromyography and Kinesiology","volume":"85 ","pages":"Article 103075"},"PeriodicalIF":2.3,"publicationDate":"2025-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145410857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-15DOI: 10.1016/j.jelekin.2025.103073
Matias Fröhlich , Alessandra Rizza , Rodrigo Osorio , Marco Aurélio Vaz , Brian Andrews , Giacinto Luigi Cerone , Alberto Botter , Taian Martins Vieira
Purpose
Functional electrical stimulation (FES) has been documented to provide invaluable, therapeutic effect. The success of FES applications relies on the positioning of stimulation electrodes closely to the muscle motor points. During joint movement, however, motor points may shift as the muscle length changes. Using an objective procedure to define motor points, we assessed how much and how relevantly knee extensors’ motor point location changes with joint angle. Methods: Current pulses were applied over 121 (11 × 11) equally spaced stimulation sites, determined according to the size and boundaries of the three superficial knee extensors of 17 healthy subjects. Five consecutive monophasic pulses (100 µs, 1pps) were delivered at each site for two knee joint angles (40° and 115°) and two intensities (120 % of motor threshold and maximum tolerable). The average peak torque greater than 60 % of the maximum torque was used to identify motor points across sites. The centroid of motor point clusters—motor zones—was considered to assess motor point displacement and peak torque for different knee joint angles. Results: Significant centroid shifts were observed distally (2.5 % displacement; p < 0.031) and medially (4.4 % shift; p < 0.021), representing ∼ 1 cm shifts in both directions, when going from 40° to 115° of knee flexion. Mean differences in peak torque between joint angles were negligible, however, amounting to less than 2 % of maximal voluntary torque. Conclusion: The displacement of quadriceps motor points with knee position changes is of negligible practical relevance for justifying a variable position of stimulation electrodes in FES protocols.
{"title":"Changes in knee joint angle affect to a negligible extent the distribution of motor points—the motor zones—in the quadriceps muscles","authors":"Matias Fröhlich , Alessandra Rizza , Rodrigo Osorio , Marco Aurélio Vaz , Brian Andrews , Giacinto Luigi Cerone , Alberto Botter , Taian Martins Vieira","doi":"10.1016/j.jelekin.2025.103073","DOIUrl":"10.1016/j.jelekin.2025.103073","url":null,"abstract":"<div><h3>Purpose</h3><div>Functional electrical stimulation (FES) has been documented to provide invaluable, therapeutic effect. The success of FES applications relies on the positioning of stimulation electrodes closely to the muscle motor points. During joint movement, however, motor points may shift as the muscle length changes. Using an objective procedure to define motor points, we assessed how much and how relevantly knee extensors’ motor point location changes with joint angle. <em>Methods:</em> Current pulses were applied over 121 (11 × 11) equally spaced stimulation sites, determined according to the size and boundaries of the three superficial knee extensors of 17 healthy subjects. Five consecutive monophasic pulses (100 µs, 1pps) were delivered at each site for two knee joint angles (40° and 115°) and two intensities (120 % of motor threshold and maximum tolerable). The average peak torque greater than 60 % of the maximum torque was used to identify motor points across sites. The centroid of motor point clusters—motor zones—was considered to assess motor point displacement and peak torque for different knee joint angles. <em>Results:</em> Significant centroid shifts were observed distally (2.5 % displacement; p < 0.031) and medially (4.4 % shift; p < 0.021), representing ∼ 1 cm shifts in both directions, when going from 40° to 115° of knee flexion. Mean differences in peak torque between joint angles were negligible, however, amounting to less than 2 % of maximal voluntary torque. <em>Conclusion:</em> The displacement of quadriceps motor points with knee position changes is of negligible practical relevance for justifying a variable position of stimulation electrodes in FES protocols.</div></div>","PeriodicalId":56123,"journal":{"name":"Journal of Electromyography and Kinesiology","volume":"85 ","pages":"Article 103073"},"PeriodicalIF":2.3,"publicationDate":"2025-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145350150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-12DOI: 10.1016/j.jelekin.2025.103074
Ana Ferri-Caruana , Joaquín Martín Marzano-Felisatti , Carlos Sendra-Pérez , Jose Ignacio Priego-Quesada
Understanding the neuromuscular demands of explosive tasks is essential for enhancing performance and reducing injury risk. This study analyzed inter-limb activation of the medial and lateral gastrocnemius during take-off and landing phases of bilateral and unilateral countermovement jumps (CMJ) and horizontal jumps (HJ), examining its relationship with inter-limb asymmetry and performance. Twenty-six physically active participants performed CMJ and HJ tasks while bilateral surface electromyography was recorded from both gastrocnemius heads. Jump performance was evaluated using flight time (CMJ) and distance (HJ), and asymmetry indices were computed between dominant and non-dominant limbs. Results showed significantly greater muscle activity during take-off than landing across all conditions (p < 0.05). During CMJ landings, the medial gastrocnemius was more active than the lateral, with no activation differences found between unilateral and bilateral jumps. A moderate positive correlation was observed between CMJ performance and bilateral take-off asymmetry (r = 0.43, p = 0.02). Conversely, greater activation in the non-dominant gastrocnemius was negatively associated with performance in both CMJ and HJ (r = –0.39 to –0.48, p < 0.05). In conclusion, gastrocnemius muscles display phase-specific activation patterns. Moderate asymmetry during take-off may benefit performance, while excessive activation in the non-dominant limb may reflect compensatory strategies detrimental to jump efficiency.
{"title":"Inter-limb neuromuscular activity of the gastrocnemius muscle during unilateral and bilateral explosive jumps and relationship with jump performance","authors":"Ana Ferri-Caruana , Joaquín Martín Marzano-Felisatti , Carlos Sendra-Pérez , Jose Ignacio Priego-Quesada","doi":"10.1016/j.jelekin.2025.103074","DOIUrl":"10.1016/j.jelekin.2025.103074","url":null,"abstract":"<div><div>Understanding the neuromuscular demands of explosive tasks is essential for enhancing performance and reducing injury risk. This study analyzed inter-limb activation of the medial and lateral gastrocnemius during take-off and landing phases of bilateral and unilateral countermovement jumps (CMJ) and horizontal jumps (HJ), examining its relationship with inter-limb asymmetry and performance. Twenty-six physically active participants performed CMJ and HJ tasks while bilateral surface electromyography was recorded from both gastrocnemius heads. Jump performance was evaluated using flight time (CMJ) and distance (HJ), and asymmetry indices were computed between dominant and non-dominant limbs. Results showed significantly greater muscle activity during take-off than landing across all conditions (p < 0.05). During CMJ landings, the medial gastrocnemius was more active than the lateral, with no activation differences found between unilateral and bilateral jumps. A moderate positive correlation was observed between CMJ performance and bilateral take-off asymmetry (r = 0.43, p = 0.02). Conversely, greater activation in the non-dominant gastrocnemius was negatively associated with performance in both CMJ and HJ (r = –0.39 to –0.48, p < 0.05). In conclusion, gastrocnemius muscles display phase-specific activation patterns. Moderate asymmetry during take-off may benefit performance, while excessive activation in the non-dominant limb may reflect compensatory strategies detrimental to jump efficiency.</div></div>","PeriodicalId":56123,"journal":{"name":"Journal of Electromyography and Kinesiology","volume":"85 ","pages":"Article 103074"},"PeriodicalIF":2.3,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145304558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-01Epub Date: 2025-08-05DOI: 10.1016/j.jelekin.2025.103046
Nicholas Toninelli, Giuseppe Coratella, Christian Doria, Eloisa Limonta, Marta Borrelli, Susanna Rampichini, Fabio Esposito, Stefano Longo, Emiliano Cè
We assessed passive static stretching (PS) effects on the spatial distribution of muscle excitation (SDME) of the stretched (SL) and contralateral non-stretched limb (CL) during maximum voluntary isometric contractions (MVC). Before (PRE) and after 5-min PS, immediately (POST), at min 5 (POST5) and 10 (POST10), range of motion (ROM), maximal M-wave (Mmax) and MVC of both limbs were assessed in thirty men. During MVC, high-density surface electromyographic signals from the gastrocnemius medialis (GM) and lateralis (GL) were collected. The root mean square (RMS) and centroid coordinates were then obtained. During PS, discomfort perception (VAS), proximal and distal GM architecture were recorded. At POST, ROM increased and MVC decreased together with RMS in both limbs (P < 0.05). A cranio-caudal shift in SDME occurred in both muscles of SL and CL (P < 0.01) that persisted only in SL until POST5 in GM (P = 0.04), and POST10 in GL (P = 0.01). During PS, VAS was high (>8.0), and fascicle length and angle increased from rest (P < 0.01). No differences between GM portions were found in muscle architecture and in Mmax (P > 0.05). The results suggest involvement of central neural mechanisms in SDME shift. The prolonged effect in SL compared to CL indicates a possible additional contribution from mechanical mechanisms.
{"title":"Passive stretching-induced changes in the spatial distribution of muscle excitation: A step forward in the interpretation of the underlying mechanisms.","authors":"Nicholas Toninelli, Giuseppe Coratella, Christian Doria, Eloisa Limonta, Marta Borrelli, Susanna Rampichini, Fabio Esposito, Stefano Longo, Emiliano Cè","doi":"10.1016/j.jelekin.2025.103046","DOIUrl":"10.1016/j.jelekin.2025.103046","url":null,"abstract":"<p><p>We assessed passive static stretching (PS) effects on the spatial distribution of muscle excitation (SDME) of the stretched (SL) and contralateral non-stretched limb (CL) during maximum voluntary isometric contractions (MVC). Before (PRE) and after 5-min PS, immediately (POST), at min 5 (POST<sub>5</sub>) and 10 (POST<sub>10</sub>), range of motion (ROM), maximal M-wave (M<sub>max</sub>) and MVC of both limbs were assessed in thirty men. During MVC, high-density surface electromyographic signals from the gastrocnemius medialis (GM) and lateralis (GL) were collected. The root mean square (RMS) and centroid coordinates were then obtained. During PS, discomfort perception (VAS), proximal and distal GM architecture were recorded. At POST, ROM increased and MVC decreased together with RMS in both limbs (P < 0.05). A cranio-caudal shift in SDME occurred in both muscles of SL and CL (P < 0.01) that persisted only in SL until POST<sub>5</sub> in GM (P = 0.04), and POST<sub>10</sub> in GL (P = 0.01). During PS, VAS was high (>8.0), and fascicle length and angle increased from rest (P < 0.01). No differences between GM portions were found in muscle architecture and in M<sub>max</sub> (P > 0.05). The results suggest involvement of central neural mechanisms in SDME shift. The prolonged effect in SL compared to CL indicates a possible additional contribution from mechanical mechanisms.</p>","PeriodicalId":56123,"journal":{"name":"Journal of Electromyography and Kinesiology","volume":"84 ","pages":"103046"},"PeriodicalIF":2.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144805360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-01Epub Date: 2025-08-05DOI: 10.1016/j.jelekin.2025.103045
Carlos Cruz-Montecinos, Camila Barraza-Viluñir, Luis Acuña-Cancino, Jean Arias, Cristina Olivares, Rodrigo Nuñez-Cortés, Joaquín Calatayud, Xavier Garcia-Masso, Carlos De la Fuente, Claudio Tapia, Felipe P Carpes
Intermuscular coordination (IMC) refers to the nervous system's ability to synchronise muscle activity. While regular physical activity is thought to enhance IMC, the nature of this relationship remains poorly understood. Here we investigate whether high and low IMC between ankle muscles during gait differs based on physical activity levels and individuals' weekly engagement in vigorous activities among young adults. Twenty-five participants (10 females) aged 20-34 years were evaluated. Surface electromyography (EMG) recorded activity of the tibialis anterior (TA), soleus (SOL), and medial gastrocnemius (GM) at 1000 Hz during 10 walking trials at 1 m/s (90 m total). Each EMG epoch included 200 ms before to 600 ms after heel contact and was analysed using causal empirical mode decomposition to identify intrinsic mode functions (IMFs) with stronger causal relationships among muscle pairs. Coordination between selected IMFs of the SOL-TA and SOL-MG muscle pairs was assessed using cross-approximate entropy (XApEn). K-means clustering of XApEn values identified low and high IMC groups (p < 0.001). Proportion of physically active individuals was 83 % in high IMC group, compared to 23 % in low IMC group (p = 0.003). Weekly vigorous activity was greater in the active group (240 vs. 0 min, p = 0.010) and showed a significant moderate correlation with IMC between antagonistic muscles. Physical activity enhances intermuscular coordination among ankle muscles during gait. This emphasizes the role of physical activity, particularly vigorous activity, in enhancing neuromuscular function and counteracting the negative effects of sedentary behaviour on the neuromuscular system.
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Pub Date : 2025-09-23DOI: 10.1016/j.jelekin.2025.103072
Joana Azevedo , Pedro Fonseca , Adérito Seixas , José Oliveira , João Paulo Vilas-Boas
Purpose
This study aimed to describe muscle coactivation during knee joint-position sense (KJPS) assessments in healthy individuals, before and after muscle fatigue, and to analyse the implications for the magnitude of errors and directional bias.
Methods
The KJPS of 21 healthy males was assessed in the sitting position through concentric (SIT_CC) and eccentric repositionings (SIT_ECC) to 45° of knee flexion. Two fatigue protocols were tested, consisting of concentric contractions of the knee extensors or flexors. Muscle coactivation indices were calculated based on the normalized mean activation of the vastus lateralis and biceps femoris muscles. Absolute and relative errors were calculated to group participants by magnitude of errors (lower vs. higher errors) and directional bias (extension vs. flexion).
Results
Coactivation indices ranged between 74.92 % - 98.43 %. Significant overall decrease in coactivation indices after both fatigue protocols (p < 0.05). No significant differences in coactivation were found between magnitude of errors groups (p > 0.05), but significant higher coactivation were observed in participants failing the target position into flexion, only in the SIT_CC test (0.001 < p < 0.042).
Conclusion
Muscle coactivation between knee extensors and flexors was high in the assessed JPS tests, and decreased after fatigue. Muscle coactivation does not appear to explain the magnitude of errors, while it seems to influence directional bias.
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