scholarly journals Effects of Short-Term Training With Uncoupled Cranks in Trained Cyclists

2012 ◽  
Vol 7 (2) ◽  
pp. 113-120 ◽  
Author(s):  
Jack M. Burns ◽  
Jeremiah J. Peiffer ◽  
Chris R. Abbiss ◽  
Greig Watson ◽  
Angus Burnett ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Vastus Lateralis ◽  
Biceps Femoris ◽  
Training Group ◽  
Recovery Phase ◽  
Muscle Recruitment ◽  
Short Term ◽  
Activation Patterns ◽  
Gross Efficiency ◽  
Muscle Activation Patterns

Purpose:Manufacturers of uncoupled cycling cranks claim that their use will increase economy of motion and gross efficiency. Purportedly, this occurs by altering the muscle-recruitment patterns contributing to the resistive forces occurring during the recovery phase of the pedal stroke. Uncoupled cranks use an independent-clutch design by which each leg cycles independently of the other (ie, the cranks are not fixed together). However, research examining the efficacy of training with uncoupled cranks is equivocal. The purpose of this study was to determine the effect of short-term training with uncoupled cranks on the performance-related variables economy of motion, gross efficiency, maximal oxygen uptake (VO2max), and muscle-activation patterns.Methods:Sixteen trained cyclists were matched-paired into either an uncoupled-crank or a normal-crank training group. Both groups performed 5 wk of training on their assigned cranks. Before and after training, participants completed a graded exercise test using normal cranks. Expired gases were collected to determine economy of motion, gross efficiency, and VO2max, while integrated electromyography (iEMG) was used to examine muscle-activation patterns of the vastus lateralis, biceps femoris, and gastrocnemius.Results:No significant changes between groups were observed for economy of motion, gross efficiency, VO2max, or iEMG in the uncoupled- or normal-crank group.Conclusions:Five weeks of training with uncoupled cycling cranks had no effect on economy of motion, gross efficiency, muscle recruitment, or VO2max compared with training on normal cranks.

Squat Muscle Activation Patterns with Hip Rotations in Subjects with Genu Varum Deformity

2020 ◽  
Author(s):  
Mohamadreza Hatefi ◽  
Farideh Babakhani ◽  
Ramin Balouchi ◽  
Amir Letafatkar ◽  
Brian J. Wallace
Keyword(s):  
Muscle Activation ◽  
Activity Ratio ◽  
External Rotation ◽  
Vastus Lateralis ◽  
Fascia Lata ◽  
Genu Varum ◽  
Vastus Medialis ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Hip Rotation

AbstractThe purpose of this study was to compare muscle activation during the squat with different hip rotations (neutral, 15, 30, and 45° of internal and external hip rotation) in subjects with and without Genu Varum deformity deformity. Surface electromyography were recorded from 32 men with (n=16) and without (n=16) Genu Varum deformity. In the Genu Varum deformity group, the squats with 30, 45 and 15° of internal rotations of the hip showed significantly greater gluteus medius activation as compared to other positions. Moreover, the tensor fascia lata activity increased with greater external rotation of the hip, and significantly more than hip internal rotations (p<0.05). For vastus medialis and vastus lateralis, both hip internal and external rotation showed a significantly greater activation compared to the neutral hip positions (p<0.05). There were significant differences in the gluteus medius:tensor fascia lata activity ratio (p=0.001) and the vastus medialis: vastus lateralis activity ratio (p=0.001) between the different hip positions in the Genu Varum deformity and healthy groups. These results demonstrate that muscle activation patterns varied significantly with the position of different hip rotation in both groups. Those with Genu Varum deformity may use this information to aid in an injury prevention strategy by choosing squat positioning that favorably alters muscle activation patterns.

scholarly journals Stability of Measurement Outcomes for Voluntary Task Performance in Participants With Chronic Ankle Instability and Healthy Participants

2011 ◽  
Vol 46 (4) ◽  
pp. 366-375 ◽  
Author(s):  
Sara Van Deun ◽  
Karel Stappaerts ◽  
Oron Levin ◽  
Luc Janssens ◽  
Filip Staes
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Intervention Program ◽  
Ankle Instability ◽  
Chronic Ankle Instability ◽  
Control Group ◽  
Muscle Recruitment ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Recruitment Order

Context: Acceptable measurement stability during data collection is critically important to research. To interpret differences in measurement outcomes among participants or changes within participants after an intervention program, we need to know whether the measurement is stable and consistent. Objective: To determine the within-session stability of muscle activation patterns for a voluntary postural-control task in a group of noninjured participants and a group of participants with chronic ankle instability (CAI). Design: Descriptive laboratory study. Setting: Musculoskeletal laboratory. Patients or Other Participants: Twenty control participants (8 men, 12 women; age = 21.8 ± 2.4 years, height = 164.3 ± 13.4 cm, mass = 68.4 ± 17.9 kg) and 20 participants with CAI (12 men, 8 women; age = 21.2 ± 2.1 years, height = 176 ± 10.2 cm, mass = 71.7 ± 11.3 kg). Intervention(s): Participants performed 4 barefoot standing trials, each of which included a 30-second double-legged stance followed by a 30-second single-legged stance in 3 conditions: with vision, without vision, and with vision on a balance pad. Main Outcome Measure(s): The activity of 7 muscles of the lower limb was measured for the stance task in the 3 different conditions for each trial. The onset of muscle activity and muscle recruitment order were determined and compared between the first and the fourth trials for both groups and for each condition. Results: We found no differences in the onset of muscle activity among trials for both groups or for each condition. The measurement error was 0.9 seconds at maximum for the control group and 0.12 seconds for the CAI group. In the control group, 70% to 80% of the participants used the same muscle recruitment order in both trials. In the CAI group, 75% to 90% used the same recruitment order. Conclusions: Within 1 session, measurement stability for this task was acceptable for use in further research. Furthermore, no differences were found in measurement stability across conditions in the control or CAI groups.

A Computational Model of Muscle Recruitment for Wrist Movements

2002 ◽  
Vol 88 (6) ◽  
pp. 3348-3358 ◽  
Author(s):  
Andrew H. Fagg ◽  
Ashvin Shah ◽  
Andrew G. Barto
Keyword(s):  
Motor System ◽  
Muscle Activation ◽  
Movement Direction ◽  
Joint Motion ◽  
Muscle Recruitment ◽  
Task Constraints ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Recruitment Behavior ◽  
Total Effort

To execute a movement, the CNS must appropriately select and activate the set of muscles that will produce the desired movement. This problem is particularly difficult because a variety of muscle subsets can usually be used to produce the same joint motion. The motor system is therefore faced with a motor redundancy problem that must be resolved to produce the movement. In this paper, we present a model of muscle recruitment in the wrist step-tracking task. Muscle activation levels for five muscles are selected so as to satisfy task constraints (moving to the designated target) while also minimizing a measure of the total effort in producing the movement. Imposing these constraints yields muscle activation patterns qualitatively similar to those observed experimentally. In particular, the model reproduces the observed cosine-like recruitment of muscles as a function of movement direction and also appropriately predicts that certain muscles will be recruited most strongly in movement directions that differ significantly from their direction of action. These results suggest that the observed recruitment behavior may not be an explicit strategy employed by the nervous system, but instead may result from a process of movement optimization.

Comparative Muscle Activation Patterns of Healthy Control Limbs and Contralateral Limbs in ACL Reconstruction

2012 ◽  
Author(s):  
Chelsea Marsh ◽  
Scott Tashman
Keyword(s):  
Acl Reconstruction ◽  
Muscle Activation ◽  
Vastus Lateralis ◽  
Rectus Femoris ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Healthy Control ◽  
Reconstructed Knee

ACL reconstruction (ACLr) has been found to restore the functionality and mobility of those afflicted with ACL tears. In the process of this restoration, previous work has shown alterations in the activity of the musculature surrounding the reconstructed knee [1]. Specifically, at 5 months post-op, the gastrocnemius, vastus lateralis, and rectus femoris demonstrate significantly different activation patterns. These differences raise the question if the reconstructed leg is the only limb affected by ACLr.

Muscle Activation in World-Champion, World-Class, and National Breaststroke Swimmers

2017 ◽  
Vol 12 (4) ◽  
pp. 538-547 ◽  
Author(s):  
Bjørn Harald Olstad ◽  
Christoph Zinner ◽  
João Rocha Vaz ◽  
Jan M.H. Cabri ◽  
Per-Ludvik Kjendlie
Keyword(s):  
Tibialis Anterior ◽  
Muscle Activation ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Triceps Brachii ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
World Class ◽  
World Champion ◽  
Maximal Effort

Purpose:To investigate the muscle-activation patterns and coactivation with the support of kinematics in some of the world’s best breaststrokers and identify performance discriminants related to national elites at maximal effort.Methods:Surface electromyography was collected in 8 muscles from 4 world-class (including 2 world champions) and 4 national elite breaststroke swimmers during a 25-m breaststroke at maximal effort.Results:World-class spent less time during the leg recovery (P = .043), began this phase with a smaller knee angle (154.6° vs 161.8°), and had a higher median velocity of 0.18 m/s during the leg glide than national elites. Compared with national elites, world-class swimmers showed a difference in the muscle-activation patterns for all 8 muscles. In the leg-propulsion phase, there was less triceps brachii activation (1 swimmer 6% vs median 23.0% [8.8]). In the leg-glide phase, there was activation in rectus femoris and gastrocnemius during the beginning of this phase (all world-class vs only 1 national elite) and a longer activation in pectoralis major (world champions 71% [0.5] vs 50.0 [4.3]) (propulsive phase of the arms). In the leg-recovery phase, there was more activation in biceps femoris (50.0% [15.0] vs 20.0% [14.0]) and a later and quicker activation in tibialis anterior (40.0% [7.8] vs 52.0% [6.0]). In the stroke cycle, there was no coactivation in tibialis anterior and gastrocnemius for world champions.Conclusion:These components are important performance discriminants. They can be used to improve muscle-activation patterns and kinematics through the different breaststroke phases. Furthermore, they can be used as focus points for teaching breaststroke to beginners.

scholarly journals The Capacity of Generic Musculoskeletal Simulations to Predict Knee Joint Loading Using the CAMS-Knee Datasets

2020 ◽  
Vol 48 (4) ◽  
pp. 1430-1440 ◽  
Author(s):  
Zohreh Imani Nejad ◽  
Khalil Khalili ◽  
Seyyed Hamed Hosseini Nasab ◽  
Pascal Schütz ◽  
Philipp Damm ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Biceps Femoris ◽  
Contact Forces ◽  
Generic Model ◽  
Model Parameters ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Level Walking ◽  
Muscle Activations

Abstract Musculoskeletal models enable non-invasive estimation of knee contact forces (KCFs) during functional movements. However, the redundant nature of the musculoskeletal system and uncertainty in model parameters necessitates that model predictions are critically evaluated. This study compared KCF and muscle activation patterns predicted using a scaled generic model and OpenSim static optimization tool against in vivo measurements from six patients in the CAMS-knee datasets during level walking and squatting. Generally, the total KCFs were under-predicted (RMS: 47.55%BW, R 2: 0.92) throughout the gait cycle, but substiantially over-predicted (RMS: 105.7%BW, R 2: 0.81) during squatting. To understand the underlying etiology of the errors, muscle activations were compared to electromyography (EMG) signals, and showed good agreement during level walking. For squatting, however, the muscle activations showed large descrepancies especially for the biceps femoris long head. Errors in the predicted KCF and muscle activation patterns were greatest during deep squat. Hence suggesting that the errors mainly originate from muscle represented at the hip and an associated muscle co-contraction at the knee. Furthermore, there were substaintial differences in the ranking of subjects and activities based on peak KCFs in the simulations versus measurements. Thus, future simulation study designs must account for subject-specific uncertainties in musculoskeletal predictions.

scholarly journals Individuals have unique muscle activation signatures as revealed during gait and pedaling

2019 ◽  
Vol 127 (4) ◽  
pp. 1165-1174 ◽  
Author(s):  
François Hug ◽  
Clément Vogel ◽  
Kylie Tucker ◽  
Sylvain Dorel ◽  
Thibault Deschamps ◽  
...  
Keyword(s):  
Machine Learning ◽  
Muscle Activation ◽  
Vastus Lateralis ◽  
Support Vector ◽  
Experimental Session ◽  
Learning Approach ◽  
Classification Rate ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Machine Learning Approach

Although it is known that the muscle activation patterns used to produce even simple movements can vary between individuals, these differences have not been considered to prove the existence of individual muscle activation strategies (or signatures). We used a machine learning approach (support vector machine) to test the hypothesis that each individual has unique muscle activation signatures. Eighty participants performed a series of pedaling and gait tasks, and 53 of these participants performed a second experimental session on a subsequent day. Myoelectrical activity was measured from eight muscles: vastus lateralis and medialis, rectus femoris, gastrocnemius lateralis and medialis, soleus, tibialis anterior, and biceps femoris -long head. The classification task involved separating data into training and testing sets. For the within-day classification, each pedaling/gait cycle was tested using the classifier, which had been trained on the remaining cycles. For the between-day classification, each cycle from day 2 was tested using the classifier, which had been trained on the cycles from day 1. When considering all eight muscles, the activation profiles were assigned to the corresponding individuals with a classification rate of up to 99.28% (2,353/2,370 cycles) and 91.22% (1,341/1,470 cycles) for the within-day and between-day classification, respectively. When considering the within-day classification, a combination of two muscles was sufficient to obtain a classification rate >80% for both pedaling and gait. When considering between-day classification, a combination of four to five muscles was sufficient to obtain a classification rate >80% for pedaling and gait. These results demonstrate that strategies not only vary between individuals, as is often assumed, but are unique to each individual. NEW & NOTEWORTHY We used a machine learning approach to test the uniqueness and robustness of muscle activation patterns. We considered that, if an algorithm can accurately identify participants, one can conclude that these participants exhibit discernible differences and thus have unique muscle activation signatures. Our results show that activation patterns not only vary between individuals, but are unique to each individual. Individual differences should, therefore, be considered relevant information for addressing fundamental questions about the control of movement.

Biceps Femoris Compensates for Semitendinosus After Anterior Cruciate Ligament Reconstruction With a Hamstring Autograft: A Muscle Functional Magnetic Resonance Imaging Study in Male Soccer Players

2021 ◽  
pp. 036354652110033
Author(s):  
Thomas Tampere ◽  
Jan Victor ◽  
Thomas Luyckx ◽  
Hannes Vermue ◽  
Nele Arnout ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Cruciate Ligament ◽  
Biceps Femoris ◽  
Soccer Players ◽  
Hamstring Muscle ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
History Of ◽  
Anterior Cruciate ◽  
Tendon Autograft

Background: Rates of reinjury, return to play (RTP) at the preinjury level, and hamstring strain injuries in male soccer players after anterior cruciate ligament reconstruction (ACLR) remain unsatisfactory, due to multifactorial causes. Recent insights on intramuscular hamstring coordination revealed the semitendinosus (ST) to be of crucial importance for hamstring functioning, especially during heavy eccentric hamstring loading. Scientific evidence on the consequences of ST tendon harvest for ACLR is scarce and inconsistent. This study intended to investigate the repercussions of ST harvest for ACLR on hamstring muscle function. Hypothesis: Harvest of the ST tendon for ACLR was expected to have a significant influence on hamstring muscle activation patterns during eccentric exercises, evaluated at RTP in a population of male soccer athletes. Study Design: Controlled laboratory study. Methods: A total of 30 male soccer players with a history of ACLR who were cleared for RTP and 30 healthy controls were allocated to this study during the 2018-2019 soccer season. The influence of ACLR on hamstring muscle activation patterns was assessed by comparing the change in T2 relaxation times [ΔT2 (%) = [Formula: see text]] of the hamstring muscle tissue before and after an eccentric hamstring loading task between athletes with and without a recent history of ACLR through use of muscle functional magnetic resonance imaging, induced by an eccentric hamstring loading task between scans. Results: Significantly higher exercise-related activity was observed in the biceps femoris (BF) of athletes after ACLR compared with uninjured control athletes (13.92% vs 8.48%; P = .003), whereas the ST had significantly lower activity (19.97% vs 25.32%; P = .049). Significant differences were also established in a within-group comparison of the operated versus the contralateral leg in the ACLR group (operated vs nonoperated leg: 14.54% vs 11.63% for BF [ P = .000], 17.31% vs 22.37% for ST [ P = .000], and 15.64% vs 13.54% for semimembranosus [SM] [ P = .014]). Neither the muscle activity of SM and gracilis muscles nor total posterior thigh muscle activity (sum of exercise-related ΔT2 of the BF, ST, and SM muscles) presented any differences in individuals who had undergone ACLR with an ST tendon autograft compared with healthy controls. Conclusion: These findings indicate that ACLR with a ST tendon autograft might notably influence the function of the hamstring muscles and, in particular, their hierarchic dimensions under fatiguing loading circumstances, with increases in relative BF activity contribution and decreases in relative ST activity after ACLR. This between-group difference in hamstring muscle activation pattern suggests that the BF partly compensates for deficient ST function in eccentric loading. These alterations might have implications for athletic performance and injury risk and should probably be considered in rehabilitation and hamstring injury prevention after ACLR with a ST tendon autograft.

Lower-Extremity Muscle Activation during the Star Excursion Balance Tests

2001 ◽  
Vol 10 (2) ◽  
pp. 93-104 ◽  
Author(s):  
Jennifer Erin Earl ◽  
Jay Hertel
Keyword(s):  
Lower Extremity ◽  
Repeated Measures ◽  
Muscle Activation ◽  
Vastus Lateralis ◽  
Biceps Femoris ◽  
Emg Activity ◽  
Muscle Activation Patterns ◽  
Lower Extremity Muscle ◽  
Balance Tests ◽  
Integrated Emg

Objective:To identify integrated EMG (I-EMG) activity of 6 lower-extremity muscles during the 8 Star Excursion Balance Tests (SEBTs).Design and Setting:Repeated measures, laboratory setting.Subjects:10 healthy young adults.Interventions:The SEBTs require the subject to balance on the stance leg and maximally reach with the contralateral foot along each of 8 lines extending from a common axis at 45° intervals.Measures:I-EMG activity of the vastus medialis obliquus (VMO), vastus lateralis (VL), medial hamstring (MH), biceps femoris (BF), anterior tibialis (AT), and gas-trocnemius.Results:Significant differences were found in all muscles (P < .05) except the gastrocnemius (P = .08). VMO and VL activity tended to be greatest with anteriorly directed excursions, whereas the MH and BF activity were greatest with posteriorly directed excursions. AT activity was lowest with the lateral excursion.Conclusions:Performance of the different SEBTs results in different lower-extremity muscle-activation patterns.

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