Duration Of Muscle Activity Research Articles

Muscle Excitation During A Weighted And Unweighted Supine Bridge (a Pilot Study)

Previous studies have examined the relationship between muscle activities during a single leg bridge (SLB) without including the gluteus maximus muscle (Gmax). Similarly, few studies have evaluated the influence of additional loading during a SLB. PURPOSE: To examine muscle activation levels of the Gmax, semitendinosus (ST), and the biceps femoris long-head (BFL) during SLB, and weighted single leg bridge (wSLB). METHODS: Two recreationally active college students (1 male;1 female) were recruited for the study and were free of any muscle or orthopedic injuries. Surface electromyography (sEMG) were used to collect muscle activities. Maximal voluntary contractions (MVC) were collected for each muscle group prior to testing. Each participant performed three repetitions of both SLB and wSLB, following a pattern of 60 beats per minute (~2 beats up, ~3 beat hold, and ~2 beats down) which was verified using an electronic metronome. Data was collected and analyzed using a commercially available sEMG package. MVCs of each muscle were used to normalize the observed peak sEMG during the exercise. Peak root mean square (RMS) was obtained for each muscle and the peak RMS in SLB was set to 100% to provide a means of comparison. Burst threshold was defined as 10% of the observed peak value. This value determined the onset and offset of the muscle excitation. RESULTS: There was a 37.0 +/- 1.7 average difference in magnitude between the two exercises. The duration of activity of the Gmax, BFL, and ST during the unweighted trials were 4.0 +/- 1.25 seconds, 3.5 +/- 0.75s and 4.2+/- 0.45s, respectively. Muscle activity duration remained unchanged in the wSLB in the Gmax and STN. However, there was an increase in BFL activity during the wSLB trials (4.0 +/- 0.7s). CONCLUSION: In the male participant, it was concluded that the main muscle activated during the original single leg bridge and the weighted single leg bridge was BFL. However, for the female participant, the main muscle was the STN. Muscle activation of the hamstring muscles increased as a whole from the unweighted exercises to the weighted exercise. As well as the duration of BFL activity.This study is preliminary and will be conducted at a larger scale in the future to enhance credibility and reliability.

Evaluation of a method to scale muscle strength for gait simulations of children with cerebral palsy

Cerebral palsy (CP) is a neurological disorder that results in life-long mobility impairments. Musculoskeletal models used to investigate mobility deficits for children with CP often lack subject-specific characteristics such as altered muscle strength, despite a high prevalence of muscle weakness in this population. We hypothesized that incorporating subject-specific strength scaling within musculoskeletal models of children with CP would improve accuracy of muscle excitation predictions in walking simulations. Ten children (13.5 ± 3.3 years; GMFCS level II) with spastic CP participated in a gait analysis session where lower-limb kinematics, ground reaction forces, and bilateral electromyography (EMG) of five lower-limb muscles were collected. Isometric strength was measured for each child using handheld dynamometry. Three musculoskeletal models were generated for each child including a ‘Default’ model with the generic musculoskeletal model’s muscle strength, a ‘Uniform’ model with muscle strength scaled allometrically, and a ‘Custom’ model with muscle strength scaled based on handheld dynamometry strength measures. Muscle-driven gait simulations were generated using each model for each child. Simulation accuracy was evaluated by comparing predicted muscle excitations and measured EMG signals, both in the duration of muscle activity and the root-mean-square difference (RMSD) between signals. Improved agreement with EMG were found in both the ‘Custom’ and ‘Uniform’ models compared to the ‘Default’ model indicated by improvement in RMSD summed across all muscles, as well as RMSD and duration of activity for individual muscles. Incorporating strength scaling into musculoskeletal models can improve the accuracy of walking simulations for children with CP.

Muscle Activity Pattern Dysfunction During Sit to Stand and Stand to Sit in the Movement System Impairment Subgroups of Low Back Pain

ObjectiveTo investigate impairment in the activity pattern of some muscles involved in sit to stand (STD) and stand to sit (STS) among 2 low back pain (LBP) subgroups of the Movement System Impairment (MSI) model. DesignCase-control study. SettingA university medical center. ParticipantsFifteen women without chronic LBP and 22 women with chronic LBP (N=37) in 2 subgroups (15 into the lumbar extension rotation (LER) and 7 into lumbar flexion rotation [LFR]) voluntarily participated in this study. InterventionsParticipants were asked to perform STD and STS at a preferred speed. Surface electromyography (EMG) were measured bilaterally from the internal oblique (IO), lumbar erector spine (ES), medial hamstring (MH), and lateral hamstring (LH) muscles. Main Outcome MeasuresChanges in mean and maximum amplitude, time to peak amplitude, duration of muscle activity, and bilateral asymmetry of these variables. ResultsDuring STD, bilateral asymmetry in mean amplitude of MH in the LER subgroup (P=.031) and bilateral asymmetry in duration of LH in the LFR subgroup (P=.026) were exhibited. Also, in this task reduced time to peak left MH activation were found in the LFR subgroup than 2 other groups (control; P=.028/LER; P=.004). During STS, increased left ES maximum amplitude were observed in the LFR subgroup than LER subgroup (P=.029). Also, reduced time to peak right ES (P=.035) and left LH (P=.038) activation in the LER subgroup than control subjects and reduced time to peak left LH activation in LFR subgroup than control subjects (P=.041) were observed during STS. ConclusionsThe differences between the 2 LBP subgroups may be a result of impairment in the activity pattern of some muscles during functional activity.

The role of curvature feedback in the energetics and dynamics of lamprey swimming: A closed-loop model

Like other animals, lampreys have a central pattern generator (CPG) circuit that activates muscles for locomotion and also adjusts the activity to respond to sensory inputs from the environment. Such a feedback system is crucial for responding appropriately to unexpected perturbations, but it is also active during normal unperturbed steady swimming and influences the baseline swimming pattern. In this study, we investigate different functional forms of body curvature-based sensory feedback and evaluate their effects on steady swimming energetics and kinematics, since little is known experimentally about the functional form of curvature feedback. The distributed CPG is modeled as chains of coupled oscillators. Pairs of phase oscillators represent the left and right sides of segments along the lamprey body. These activate muscles that flex the body and move the lamprey through a fluid environment, which is simulated using a full Navier-Stokes model. The emergent curvature of the body then serves as an input to the CPG oscillators, closing the loop. We consider two forms of feedback, each consistent with experimental results on lamprey proprioceptive sensory receptors. The first, referred to as directional feedback, excites or inhibits the oscillators on the same side, depending on the sign of a chosen gain parameter, and has the opposite effect on oscillators on the opposite side. We find that directional feedback does not affect beat frequency, but does change the duration of muscle activity. The second feedback model, referred to as magnitude feedback, provides a symmetric excitatory or inhibitory effect to oscillators on both sides. This model tends to increase beat frequency and reduces the energetic cost to the lamprey when the gain is high and positive. With both types of feedback, the body curvature has a similar magnitude. Thus, these results indicate that the same magnitude of curvature-based feedback on the CPG with different functional forms can cause distinct differences in swimming performance.

Fin and body neuromuscular coordination changes during walking and swimming in Polypterus senegalus.

The ability to modulate the function of muscle is integral to an animal's ability to function effectively in the face of widely disparate challenges. This modulation of function can manifest through short-term changes in neuromuscular control, but also through long-term changes in force profiles, fatiguability and architecture. However, the relative extent to which shorter-term modulation and longer-term plasticity govern locomotor flexibility remains unclear. Here, we obtain simultaneously recorded kinematic and muscle activity data of fin and body musculature of an amphibious fish, Polypterus senegalus After examining swimming and walking behaviour in aquatically raised individuals, we show that walking behaviour is characterized by greater absolute duration of muscle activity in most muscles when compared with swimming, but that the magnitude of recruitment during walking is only increased in the secondary bursts of fin muscle and in the primary burst of the mid-body point. This localized increase in intensity suggests that walking in P. senegalus is powered in a few key locations on the fish, contrasting with the more distributed, low intensity muscle force that characterizes the stroke cycle during swimming. Finally, the increased intensity in secondary, but not primary, bursts of the fin muscles when walking probably underscores the importance of antagonistic muscle activity to prevent fin collapse, add stabilization and increase body support. Understanding the principles that underlie the flexibility of muscle function can provide key insights into the sources of animal functional and behavioural diversity.

Evaluation of a laser-based sensor for the diagnosis of neurological disorders.

Involuntary muscle activities like fasciculations or tremor are an indication for several neurological disorders. However, currently used techniques for measuring those activities are limited due to their invasiveness, the unsuitability for measuring a whole body simultaneously and the lack of an objective measurement of amplitude and duration of muscle activity. Hence, we developed a new laser-based sensor for the remote quantification of muscle activity. In the present paper we show a basic evaluation of our system by reference to ultrasound measurements. Our results show the detection limits of our remote sensor technology in terms of fasciculation size and depth within the muscle. Those results will help us for a better interpretation of our measurement results and hold promise for the future development of our system.

Characterization of Involuntary Contractions after Spinal Cord Injury Reveals Associations between Physiological and Self-Reported Measures of Spasticity.

Correlations between physiological, clinical and self-reported assessments of spasticity are often weak. Our aims were to quantify functional, self-reported and physiological indices of spasticity in individuals with thoracic spinal cord injury (SCI; 3 women, 9 men; 19–52 years), and to compare the strength and direction of associations between these measures. The functional measure we introduced involved recording involuntary electromyographic activity during a transfer from wheelchair to bed which is a daily task necessary for function. High soleus (SL) and tibialis anterior (TA) F-wave/M-wave area ratios were the only physiological measures that distinguished injured participants from the uninjured (6 women, 13 men, 19–67 years). Hyporeflexia (decreased SL H/M ratio) was unexpectedly present in older participants after injury. During transfers, the duration and intensity of involuntary electromyographic activity varied across muscles and participants, but coactivity was common. Wide inter-participant variability was seen for self-reported spasm frequency, severity, pain and interference with function, as well as tone (resistance to imposed joint movement). Our recordings of involuntary electromyographic activity during transfers provided evidence of significant associations between physiological and self-reported measures of spasticity. Reduced low frequency H-reflex depression in SL and high F-wave/M-wave area ratios in TA, physiological indicators of reduced inhibition and greater motoneuron excitability, respectively, were associated with long duration SL and biceps femoris (BF) electromyographic activity during transfers. In turn, participants reported high spasm frequency when transfers involved short duration TA EMG, decreased co-activation between SL and TA, as well as between rectus femoris (RF) vs. BF. Thus, the duration of muscle activity and/or the time of agonist-antagonist muscle coactivity may be used by injured individuals to count spasms. Intense electromyographic activity and high tone related closely (possibly from joint stabilization), while intense electromyographic activity in one muscle of an agonist-antagonist pair (especially in TA vs. SL, and RF vs. BF) likely induced joint movement and was associated with severe spasms. These data support the idea that individuals with SCI describe their spasticity by both the duration and intensity of involuntary agonist-antagonist muscle coactivity during everyday tasks.

Altered joint kinematics and increased electromyographic muscle activity during walking in patients with intermittent claudication

Patients with intermittent claudication (IC) tend to walk at a slower pace, have less lower leg muscle strength, and consume approximately 40% more oxygen during walking compared with healthy individuals. An unfavorable locomotion pattern has been suggested to explain this metabolic inefficiency. However, knowledge on gait patterns in IC is limited. Muscle activity patterns during walking measured using surface electromyography (EMG) have not been investigated in this patient population. In this cross-sectional study, gait pattern of patients newly diagnosed with IC and age-matched controls were evaluated using kinematic parameters and medial gastrocnemius (MG) and tibialis anterior (TA) muscles activity patterns. The protocol included pain-free and painful (only IC patients) treadmill walking sessions. A total of 22 IC patients and 22 healthy control subjects were included. Patients walked 1.4 km/h slower (3.2 km/h vs 4.6 km/h; P < .001) than control subjects, coinciding with a 10% slower cadence (110 steps/min vs 122 steps/min; P < .001). The kinematic analysis resulted in a patient's ankle plantar flexion reduction of 45% during the propulsion phase, and ankle dorsal flexion reduction of 41% at initial contact. No additional kinematic changes were observed when claudication pain presented. Interestingly, kinematic differences did not influence the muscle activity duration during walking, because equal duration of muscle activity was found in IC patients and healthy controls. However, the amount of muscle activity in microvolts did significantly increase in IC patients when claudication pain presented (TA: Δ23%; P < .001; MG: Δ54%; P = .007). Patients with IC show significant kinematic changes during walking. These alterations did not affect EMG activity duration of MG and TA muscles. However, EMG amplitude of both muscles did significantly increase during painful walking in IC patients.

Time Analysis of Muscle Activation during Basketball Free Throws

Objective of the study: The study assessed and compared the duration of the muscle activation in a basketball free throw, by players representing a preliminary and specialist stage of training. There was also analysed the accuracy of throws according to the stage of training, and whether individual changes in duration of activation have impact on the accuracy of free throws. Material and methods: Players from national basketball teams second and third league of the AZS Academic Sports Club of Opole University performed twenty free throws shooting to the basket during the research study. During tests, players were equipped with EMG apparatus, which registered the time of muscle activation, when subsequent free throws were performed. Arm muscle (biceps and triceps) activation time was measured from the beginning of muscle activation to the time of completion of their work, and from muscle activation to the time of reaching the rim.Results: Players of specialist stage of training, have 0,30 sec shorter average arm muscle time activation, counted from the beginning of activation to obtain the minimum value, from players of the preliminary stage of training. They also gained average 2 points better result in throw accuracy. Variability coefficient of throws duration was higher by 19.56% at players of the specialist stage of training. In the case of unforced extend duration of muscle activation, 80% of specialists and 40% players of preliminary group, don’t score the basket.Conclusions: It was observed that the basketball players of higher training experience, have lower average time of arm muscle activation. It was demonstrated that in players of the specialist stage of training, missed free throws were mostly caused by longer duration from the beginning of muscle activity to the rim, with players of the preliminary stage it was reverse.

Deficit in late-stage contingent negative variation provides evidence for disrupted movement preparation in patients with conversion paresis

Conversion paresis is the presence of unexplained weakness without detectable neuropathology that is not feigned. To examine the ‘abnormal preparation’ and ‘disrupted execution’ hypotheses proposed to explain the movement deficits in conversion paresis, electroencephalographic, electromyographic and kinematic measures were recorded during motor preparation and execution. Six patients with unilateral upper limb conversion weakness, 24 participants feigning weakness and 12 control participants performed a 2-choice precued reaction time task. Precues provided advance information about the responding hand or finger. Patients and feigners demonstrated similar diminished force, longer movement time and extended duration of muscle activity in their symptomatic limb. Patients showed significantly suppressed contingent negative variation (CNV) amplitudes, but only when the symptomatic limb was precued. Despite the similarity in performance measures, this CNV suppression was not seen in feigners. Diminished CNV for symptomatic hand precues may reflect engagement of an inhibitory mechanism suppressing cortical activity related to preparatory processes.

Muscle Activity Patterns during Transient and Prolonged Cycling in Young and Older Individuals

PURPOSE: To evaluate activation patterns of the upper and lower leg muscles during transient and prolonged cycling and compare the responses between young and older individuals. METHODS: Twelve healthy male, novice cyclists, with no history of joint problems, participated in this study and were divided into two age groups of young (22±2 yrs.) and older (53±3 yrs.). All participants signed an informed consent prior to the beginning of the study. Each subject participated in two separate sessions of cycling. TC: transient randomly assigned workloads (0, 50, 100 W; 90 sec. each) and PC: prolonged constant workload (50 W; 30 min.). During both sessions, participants pedaled at a constant cadence of 60rpm. Electromyography (EMG) activities of rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius medialis (GT) were recorded; during all TC trials and at the first and last two minutes of PC trials. Position of the pedal was also recorded throughout both sessions of cycling using a motion capture system. Two-factor ANOVA with repeated-measures was used to analyze the data. RESULTS: During TC, with increased workload, the EMG magnitude of all muscles increased proportionally in both groups. In addition, the duration of activity for RF and BF increased proportionally with workload and was significantly different between the two age groups (p<0.05). For all muscle groups, there were discrepancies in duration of muscle activity between young and old during TC. There were no differences in muscles’ EMG magnitudes and patterns of activation between the two age groups during PC. CONCLUSIONS: There were differences in muscle activity patterns and responses to different exercise intensities between young and older groups during TC (transient randomly assigned workloads). However, these differences were not observed during the moderate intensity PC (prolonged constant workload) session. Comparing the older group to a healthy, young population allows us to conclude that older individuals may benefit from longer durations of cycling exercise at low or moderate intensities without inducing exhaustion or increasing potential risk of injury.

Neuromotor Control of Gluteal Muscles in Runners with Achilles Tendinopathy

The purpose of this study was to compare the neuromotor control of the gluteus medius (GMED) and gluteus maximus (GMAX) muscles in runners with Achilles tendinopathy to that of healthy controls. Fourteen male runners with Achilles tendinopathy and 19 healthy male runners (control) ran overground while EMG of GMED and GMAX was recorded. Three temporal variables were identified via visual inspection of EMG data: (i) onset of muscle activity (onset), (ii) offset of muscle activity (offset), and (iii) duration of muscle activity (duration). A multivariate analysis of covariance with between-subject factor of group (Achilles tendinopathy, control) and variables of onset, offset, and duration was performed for each muscle. Age, weight, and height were included as covariates, and α level was set at 0.05. The Achilles tendinopathy group demonstrated a delay in the activation of the GMED relative to heel strike (P < 0.001) and a shorter duration of activation (P < 0.001) compared to that of the control group. GMED offset time relative to heel strike was not different between the groups (P = 0.063). For GMAX, the Achilles tendinopathy group demonstrated a delay in its onset (P = 0.008), a shorter duration of activation (P = 0.002), and earlier offset (P < 0.001) compared to the control group. This study provides preliminary evidence of altered neuromotor control of the GMED and GMAX muscles in male runners with Achilles tendinopathy. Although further prospective studies are required to discern the causal nature of this relationship, this study highlights the importance of considering neuromotor control of the gluteal muscles in the assessment and management of patients with Achilles tendinopathy.

Very short-term effect of brace wearing on gait in adolescent idiopathic scoliosis girls

Adolescent idiopathic scoliotic (AIS) deformity induces excessive oxygen consumption correlated to a bilateral increase of lumbo-pelvic muscles timing activity (EMG) during gait. Wearing a brace, the usual treatment for AIS, by supporting the spine and the pelvis, would generate lumbo-pelvic muscular relaxation and consequently reduce excessive oxygen consumption. The purpose of this study was to evaluate the short-term effect of bracing on gait biomechanics in scoliotic spine when compared with normal braced spine. Thirteen healthy volunteers were compared to 13 AIS girls. In both samples, gait analysis was assessed using a three-dimensional motion analysis, including synchronous kinematic, electromyographic, mechanical and energy measurements, first without brace, then wearing a brace. For scoliotic patients, comparison of in-brace and out-brace situations revealed a significant decrease of frontal pelvis (p < 0.001), hip (p < 0.001) and shoulder (p = 0.004) motion in brace associated with a significant reduction of pelvis rotation (p = 0.003). However, the brace did not change significantly the lumbo-pelvic muscle activity duration (EMG) or the mechanical and energetic parameters. Transversal pelvis motion was reduced by 39% (p = 0.04), frontal hip and shoulder motions by 23% (p = 0.004) and 30% (p = 0.01) respectively, and energy cost of walking remained increased by 37% in braced AIS girls relatively to braced healthy subjects. Mechanical and electromyographic variables were not significantly different between the two braced populations during gait except for the gluteus medius muscle that showed bilaterally an increase of duration of electrical activity in healthy subjects and contrarily a decrease in AIS patients (healthy: -3.5 ± 9.6% of gait cycle vs. scoliotic: 3.7 ± 7.7% of gait cycle; p = 0.04). Bracing changed neither the oxygen consumption nor the timing of the lumbo-pelvic muscles activity in both groups during gait. However, in brace the timing activity of bilateral gluteus medius muscles tended to decrease in AIS patients and increase in healthy subjects. Moreover, braced AIS patients had more restricted frontal hips and shoulder motion as well as pelvis rotation than braced healthy subjects.

Mass affects lower extremity muscle activity patterns in children's gait

Overweight children demonstrate biomechanical differences during gait; however it is not known if these differences occur within active or passive tissue. The purpose of this study was to examine differences in lower extremity muscle activation patterns of children with different body mass during three walking speeds. Twenty children (8–12 years) were recruited and classified as overweight (OW), normal-weight (NW), or underweight (UW). Electromyography was recorded for vastus lateralis, semitendinosus, gastrocnemius, and tibialis anterior while participants walked on a treadmill at slow (SP), self-selected (SSP), and fast (FP) speeds. Differences in group and walking speed were analyzed for duration of muscle activation (presented as a percentage of stride, stance, or swing phases). Compared to OW, UW experienced greater duration of vastus lateralis and tibialis anterior activation during the swing phase. OW had greater duration of gastrocnemius activation during stride than UW. Increased walking speed resulted in greater duration of vastus lateralis activation for all groups. NW also exhibited greater duration of tibialis anterior activation at faster walking speeds. During FP, OW had greater duration of gastrocnemius activity during stance, but lower duration during swing. These findings are consistent with the idea that children with greater mass adopt a more passive gait strategy during swing to maximize energy recovery. Increased duration of gastrocnemius activity during stance also provides greater stability and stronger propulsion, which corroborates previous research. These findings help to understand the neuromuscular mechanisms associated with previous biomechanical findings in children's gait.

Changes in activity and structure of jaw muscles in Parkinson's disease model rats

Parkinson's disease (PD), a major neurological disease, is characterised by a marked loss of dopaminergic neurons in the substantia nigra. Patients with PD frequently show chewing and swallowing dysfunctions, but little is known about the characteristics of their stomatognathic functions. The purpose of this study was to evaluate the influence of PD on jaw muscle fibre and functions. PD model rats were made by means of the injection of 6-hydroxydopamine (6-OHDA) into the striatum of 8-week-old Sprague-Dawley male rats. Five weeks after the injection, a radio-telemetric device was implanted to record muscle activity continuously from the superficial masseter and anterior belly of digastric muscles. Muscle activity was recorded for 3days and was evaluated by the total duration of muscle activity per day (duty time). After recording the muscle activities, jaw muscles were isolated for immunohistochemical and PCR analyses. In PD model rats, the following findings of the digastrics muscles verify that compared to the control group: (i) the higher duty time exceeding 5% of the peak activity level, (ii) the higher expression of the mRNA of myosin heavy chain type I, and (iii) the tendency for fast to slow fibre-type transition. With respect to the masseter muscle, there were no significant differences in all analyses. In conclusion, PD leads to the changes in the jaw behaviours, resulting in a PD-specific chewing and swallowing dysfunctions.

Surface electromyography in orthodontics – a literature review

Electromyography is the most objective and reliable technique for evaluating muscle function and efficiency by detecting their electrical potentials. It makes it possible to assess the extent and duration of muscle activity. The main aim of surface electromyography is to detect signals from many muscle fibers in the area of the detecting surface electrodes. These signals consist of a weighted summation of the spatial and temporal activity of many motor units. Hence, the analysis of the recordings is restricted to an assessment of general muscle activity, the cooperation of different muscles, and the variability of their activity over time.This study presents the main assumptions in the assessment of electrical muscle activity through the use of surface electromyography, along with its limitations and possibilities for further use in many areas of orthodontics. The main clinical uses of sEMG include the diagnostics and therapy of temporomandibular joint disorders, an assessment of the extent of stomatognathic system dysfunctions in subjects with malocclusion, and the monitoring of orthodontic therapies.

Muscle Activation Patterns in Infants With Myelomeningocele Stepping on a Treadmill

To characterize how infants with myelomeningocele (MMC) activate lower limb muscles over the first year of life, without practice, while stepping on a motorized treadmill. Twelve infants with MMC were tested longitudinally at 1, 6, and 12 months. Electromyography was used to collect data from the tibialis anterior, lateral gastrocnemius, rectus femoris, biceps femoris. Across the first year, infants showed no electromyographic activity for approximately 50% of the stride cycle with poor rhythmicity and timing of muscles, when activated. Single muscle activation predominated; agonist-antagonist coactivation was low. Probability of individual muscle activity across the stride decreased with age. Infants with MMC show high variability in timing and duration of muscle activity, few complex combinations, and very little change over time.

Dynamic Electromyography After Cruciate-retaining Total Knee Arthroplasty Revealed A Threefold Quadriceps Demand Compared With The Contralateral Normal Knee

Quadriceps functional impairment accounts for a considerable amount of morbidity after knee replacement. Cruciate-retaining total knee arthroplasty (CR-TKA) may predispose to increased quadriceps demand. We compared bilateral relative quadriceps effort in seven patients with successful unilateral CR-TKA at least 2years after surgery. Dynamic electromyography (EMG) recorded quadriceps activity during walking recorded simultaneously with gait analysis using IDEEA. There was greater EMG activity for the operated knees, both in amplitude (43.08±26.47 vs. 16.02±5.38, P=.0355), and the area under the curve (7231.1±3869.8 vs. 2547.3±1007.9, P=.0267). The onset and duration of muscle activity were similar for both knees (P=.74). CR-TKA demonstrated threefold EMG activity and muscle effort during normal walking. The study suggested that quadriceps functional deficiency is associated with CR-TKA.

Quantification of the Safe Maximal Lift in Functional Capacity Evaluations: Comparison of Muscle Recruitment Using SEMG and Therapist Observation

This study aimed to identify any correlation between muscle activity using surface electromyography (SEMG) and therapist determined safe maximal lift (SML) during the bench to shoulder lift of the WorkHab FCE. This would support construct (convergent) validity of SML determination in the WorkHab FCE. An experimental laboratory based study design was used. Twenty healthy volunteers performed the bench to shoulder lift of the WorkHab FCE whilst SEMG of upper trapezius, mid deltoid, thoracic, brachioradialis and bicep muscles were recorded. A summary of the data is presented using descriptive statistics and differences between groups were tested using generalised linear mixed models. Results showed a significant difference in activity and duration of muscle activation with increasing weight lifted [p = 0.000 and p = 0.024 (brachioradialis)]. There was a significant difference between the up lift (bench to shoulder) and the down lift (shoulder to bench) for all muscles (p = 0.000) except the brachioradialis (p = 0.819). No significant change was found in muscle activity before or after the SML. Convergent validity of the bench to shoulder lift of the WorkHab FCE was not established as no relationship between the muscle recruitment using SEMG and SML, as determined by therapist observation was identified during this lift.

The impact of altered task mechanics on timing and duration of eccentric bi-articular muscle contractions during cycling

In order to understand muscle adaptations to altered task mechanics during cycling, this study investigated the impact of altered seat height and cadence on timing and duration of gastrocnemius (GAST), biceps femoris (BF) and vastus lateralis (VL) eccentric contractions and muscle activation patterns, and cycling economy. Ten male cyclists completed 9×5min of cycling at 3 seat heights and 3 cadences. Three-dimensional leg kinematics and muscle activation patterns were recorded to estimate timing of eccentric muscle contractions. Onset, offset and duration of eccentric contractions and, onset, offset and duration of muscle activation were calculated, along with cycling economy. Duration of GAST and VL eccentric contractions decreased with increasing seat height due to earlier offset of eccentric muscle contractions. Duration of BF eccentric contractions significantly increased with seat height due to a later eccentric contraction offset. Offset of GAST and BF muscle activation occurred earlier with increasing cadence. Cycling economy was significantly affected by cadence but not seat height. The results suggest that as a consequence of altered seat height, proprioceptive feedback is used to fine-tune the timing of bi-articular eccentric muscle contractions. These results may have implications for seat height self-selection.