Motor imagery training of goal-directed reaching in relation to imagery of reaching and grasping in healthy people.

The study aimed to determine whether four weeks of motor imagery training (MIT) of goal-directed reaching (reaching to grasp task) would affect the cortical activity during motor imagery of reaching (MIR) and grasping (MIG) in the same way. We examined cortical activity regarding event-related potentials (ERPs) in healthy young participants. Our study also evaluated the subjective vividness of the imagery. Furthermore, we aimed to determine the relationship between the subjective assessment of motor imagery (MI) ability to reach and grasp and the cortical activity during those tasks before and after training to understand the underlying neuroplasticity mechanisms. Twenty-seven volunteers participated in MIT of goal-directed reaching and two measurement sessions before and after MIT. During the sessions 128-channel electroencephalography (EEG) was recorded during MIR and MIG. Also, participants assessed the vividness of the MI tasks using a visual analog scale (VAS). The vividness of imagination improved significantly (P < .05) after MIT. A repeated measures ANOVA showed that the task (MIR/MIG) and the location of electrodes had a significant effect on the ERP's amplitude (P < .05). The interaction between the task, location, and session (before/after MIT) also had a significant effect on the ERP's amplitude (P < .05). Finally, the location of electrodes and the interaction between location and session had a significant effect on the ERP's latency (P < .05). We found that MIT influenced the EEG signal associated with reaching differently than grasping. The effect was more pronounced for MIR than for MIG. Correlation analysis showed that changes in the assessed parameters due to MIT reduced the relationship between the subjective evaluation of imagining and the EEG signal. This finding means that the subjective evaluation of imagining cannot be a simple, functional insight into the bioelectrical activity of the cerebral cortex expressed by the ERPs in mental training. The changes we noted in ERPs after MIT may benefit the use of non-invasive EEG in the brain-computer interface (BCI) context.Trial registration: NCT04048083.

Effect of gender, muscle type and skinfold thickness on myometric parameters in young people.

BACKGROUND: The aim of the study was to compare the mechanical properties of three human skeletal muscles: biceps brachii (BB), rectus femoris (RF), and tibialis anterior (TA) at rest measured by myoton device in males (n = 16, mean age 21.2 ± 0.6 years) and females (n = 16; 21.2 ± 0.9 years) and to investigate the influence of skin and subcutaneous tissue thickness (skinfold thickness, SFT) and gender on myometric parameters of the three skeletal muscles. METHODS: We measured the following mechanical and viscoelastic muscle properties using MyotonPRO®: frequency (F [Hz]), decrement (D [log]), stiffness (S [N/m]), relaxation time (R [ms]) and creepability (C [De]). The values of SFT for all selected muscles were assessed by caliper. A mixed-design analysis of variance with gender as between subject comparison was used for assessing the differences between gender and muscles in SFT and each of the myometric parameters separately (F, D, S, R and C). Pearson correlation coefficient or Spearman's rank correlation coefficient between SFT and myometric parameters was conducted for males, females and males and females together. The level of statistical significance was set at α ≤ 0.05 with Bonferroni correction for multiple comparisons. RESULTS: The SFT over the RF, TA, and BB muscles in women was statistically significantly larger compared with that of males. In females and males, the SFT over the RF was larger than over the TA and BB, and the SFT over the TA was larger compared with over the BB. The values of F and S recorded for the TA muscle were the highest among the three muscles, while D, C, and R were lowest in TA but highest in the RF muscle in men and women. The values of F and S were smaller in females than in males. Gender comparison of D, C, and R values showed that only D for the RF was significantly lower in females than in males, and C for the RF and TA was significantly larger in females than in males. Some correlation between SFT and myometric parameters were different between males and females. For example, there was a significant, negative correlation between SFT and F for all muscles in females, and a significant, positive correlation between these parameters for BB and TA (not for RF) in males. For pooled data (males and females together), a negative significant correlation between SFT and F was observed for RF and TA (not significant for BB muscle). DISCUSSION: It is concluded that the TA compared with the BB and RF has significantly greater F and S but the smallest D and C and the shortest R. Gender and muscle differences in the SFT may affect the measurements of muscle properties using MyotonPRO®. The relationship between SFT and myometric parameters is different in males and females in the RF, TA, and BB muscles. Therefore, the myometric data should be analyzed in males and females separately.

Motor Imagery Training of Reaching-to-Grasp Movement Supplemented by a Virtual Environment in an Individual With Congenital Bilateral Transverse Upper-Limb Deficiency.

This study explored the effect of kinesthetic motor imagery training on reaching-to-grasp movement supplemented by a virtual environment in a patient with congenital bilateral transverse upper-limb deficiency. Based on a theoretical assumption, it is possible to conduct such training in this patient. The aim of this study was to evaluate whether cortical activity related to motor imagery of reaching and motor imagery of grasping of the right upper limb was changed by computer-aided imagery training (CAIT) in a patient who was born without upper limbs compared to a healthy control subject, as characterized by multi-channel electroencephalography (EEG) signals recorded before and 4, 8, and 12 weeks after CAIT. The main task during CAIT was to kinesthetically imagine the execution of reaching-to-grasp movements without any muscle activation, supplemented by computer visualization of movements provided by a special headset. Our experiment showed that CAIT can be conducted in the patient with higher vividness of imagery for reaching than grasping tasks. Our results confirm that CAIT can change brain activation patterns in areas related to motor planning and the execution of reaching and grasping movements, and that the effect was more pronounced in the patient than in the healthy control subject. The results show that CAIT has a different effect on the cortical activity related to the motor imagery of a reaching task than on the cortical activity related to the motor imagery of a grasping task. The change observed in the activation patterns could indicate CAIT-induced neuroplasticity, which could potentially be useful in rehabilitation or brain-computer interface purposes for such patients, especially before and after transplantation. This study was part of a registered experiment (ID: NCT04048083).

High-density surface electromyography maps after computer-aided training in individual with congenital transverse deficiency: a case study.

BACKGROUND: The aim of this study was to determine whether computer-aided training (CAT) of motor tasks would increase muscle activity and change its spatial distribution in a patient with a bilateral upper-limb congenital transverse deficiency. We believe that our study makes a significant contribution to the literature because it demonstrates the usefulness of CAT in promoting the neuromuscular adaptation in people with congenital limb deficiencies and altered body image. CASE PRESENTATION: The patient with bilateral upper-limb congenital transverse deficiency and the healthy control subject performed 12 weeks of the CAT. The subject's task was to imagine reaching and grasping a book with the hand. Subjects were provided a visual animation of that movement and sensory feedback to facilitate the mental engagement to accomplish the task. High-density electromyography (HD-EMG; 64-electrode) were collected from the trapezius muscle during a shrug isometric contraction before and after 4, 8, 12 weeks of the training. After training, we observed in our patient changes in the spatial distribution of the activation, and the increased average intensity of the EMG maps and maximal force. CONCLUSIONS: These results, although from only one patient, suggest that mental training supported by computer-generated visual and sensory stimuli leads to beneficial changes in muscle strength and activity. The increased muscle activation and changed spatial distribution of the EMG activity after mental training may indicate the training-induced functional plasticity of the motor activation strategy within the trapezius muscle in individual with bilateral upper-limb congenital transverse deficiency. Marked changes in spatial distribution during the submaximal contraction in the patient after training could be associated with changes of the neural drive to the muscle, which corresponds with specific (unfamiliar for patient) motor task. These findings are relevant to neuromuscular functional rehabilitation in patients with a bilateral upper-limb congenital transverse deficiency especially before and after upper limb transplantation and to development of the EMG based prostheses.

Eight Weeks of Aerobic Interval Training Improves Psychomotor Function in Patients with Parkinson's Disease-Randomized Controlled Trial.

BACKGROUND: This study examined the generalized effects of cycle ergometer aerobic interval training (AIT) on psychomotor behaviors in individuals with Parkinson's disease (PD), including bimanual motor control, cognitive function, and neurological motor and non-motor parkinsonian signs. METHODS: Twenty mild to moderate PD patients were randomly allocated to the following groups: (1) trained group (PD-TR, n = 10), which besides receiving usual care, underwent an 8-week moderate intensity AIT program; or (2) control group (PD-CO, n = 10) which received usual care, including participation in conventional physical therapy. Both groups were tested before and after the 8-week AIT program period with the following assessments: (1) laboratory analyses of bimanual motor control, (2) psychological evaluation of cognitive function, and (3) an evaluation of neurological parkinsonian signs. RESULTS: The PD-TR group exhibited improved (1) bimanual motor control, reflected by a decreased time (p = 0.013) and increased rate of grip force development (p = 0.013) in the manipulating hand and a decreased time delay between grip force initiation in the manipulating and stabilizing hand (p = 0.020); (2) executive function, reflected by decreased performance time in part II of the Stroop Test (p = 0.007); and (3) neurological parkinsonian signs, reflected by an amelioration of upper-extremity bradykinesia (p = 0.015) and improvement in daily life manual functions (p = 0.004), mood, and intellectual function (p = 0.005). CONCLUSIONS: Following an 8-week moderate intensity AIT program, patients with PD exhibited improved psychomotor behaviors, reflected by bimanual motor control, executive function, and neurological parkinsonian signs.

Influence of number of records on reliability of myotonometric measurements of muscle stiffness at rest and contraction.

PURPOSE: The aim of this study was to determine an effect of myotonometric records' number on stiffness measurements' reliability in muscles at rest and contraction. METHODS: Muscle stiffness was measured using Myoton-3 device. Twenty records were taken for: (i) biceps (BB) and triceps brachii (TB) at rest and for BB at 10% of maximal voluntary contraction (MVC) in healthy elderlies (HE) and in Parkinson's disease patients (PD); and (ii) brachioradialis (BR) at rest and at 25, 50 and 80% MVC in healthy young (HY) subjects. Also, in HY group, the 3-records mode was used for BR's measurements at maximal contraction. Each measurement taken with 20-records was classed into five records groups: the whole 20- and the first 15-, 10-, 5- and 3-records. Test-retest reliability for these records groups was analyzed. RESULTS: In HE and PD group measurements' reliability was excellent for all groups of records (20-3 rec- ords). In HY group, for the five groups of records taken at rest and submaximal levels of contraction (25, 50 and 80% MVC) the meas- urements reliability: (i) was mostly excellent or rarely average; and (ii) only in one per three 50% MVC conditions was unacceptable, i.e., for the 3-records group. The reliability of 3-records mode measurements at maximal contraction were unacceptable. CONCLUSIONS: Reliable myotonometric stiffness measurements in muscles at rest and during submaximal contractions can be achieved with less than 20 records (15, 10, 5 records) and even for the most of measurements with 3 records in HY and HE as well as in the PD patients. Myotonometric stiffness measurements with 3-records mode during maximal contraction were not reliable.

Influence of dopaminergic treatment on resting elbow joint angle control mechanisms in patients with Parkinson's disease - a preliminary report.

PURPOSE: Heightened tonic stretch reflex contributes to increased muscle tone and a more-flexed resting elbow joint angle (EJA) in patients with Parkinson's disease (PD). Dopaminergic medication restores central nervous system (CNS) functioning and decreases resting muscle electrical and mechanical activities. This study aimed to evaluate the effects of dopaminergic medication on parkinsonian rigidity, resting EJA, resting electrical activity (electromyography, EMG) and mechanical properties (myotonometry, MYO) of elbow flexor muscles and the associations of EJA with these muscles resting electrical activity and mechanical properties in PD patients. We also evaluated a relationship between dopaminergic treatment dose and these outcome measures values. METHODS: Ten PD patients (age 68 ± 10.1 years; body mass 70 ± 16.8 kg; height 162 ± 6.6 cm; illness duration 9 ± 4.5 years) were tested during medication on- and off-phases. Resting EJA, myotonometric muscle stiffness (S-MYO) and root mean square electromyogram amplitude (RMS-EMG) were recorded from relaxed biceps brachii and brachioradialis muscles. Based on the above parameters, we also calculated the EJA/S-MYO ratio and EJA/RMS-EMG ratio. Parkinsonian rigidity was assessed using the motor section of the Unified Parkinson's Disease Rating Scale. RESULTS: EJA, EJA/S-MYO ratio, and EJA/RMS-EMG ratio were increased and S-MYO, RMS-EMG, and parkinsonian rigidity were decreased during the medication on-phase compared with the off-phase. In addition, the dopaminergic treatment dose was negatively correlated with S-MYO and RMS-EMG, and positively correlated with EJA/SMYO and EJA/RMS-EMG ratios. CONCLUSIONS: We conclude that dopaminergic medication- induced improvements in resting elbow joint angle in tested patients with PD are related to changes in their muscle electrical and mechanical properties.

Low-Frequency Fatigue Assessed as Double to Single Twitch Ratio after Two Bouts of Eccentric Exercise of the Elbow Flexors.

The aim of this study was to assess low-frequency fatigue as a double to single twitch ratio after repeated eccentric exercise of the elbow flexors. Maximal isometric torque, single and double twitch responses and low-frequency fatigue were assessed on the elbow flexors in 16 untrained male volunteers before, immediately after, 24 and 48 hours following two bouts of eccentric exercise consisted of 30 repetitions of lowering a dumbbell adjusted to ~75% of each individual's maximal isometric torque. Maximal isometric torque and electrically evoked responses decreased significantly in all measurements after the first bout of eccentric exercise (p < 0.05). In measurements performed at 24 and 48 hours after the second bout both maximal voluntary isometric torque and electrically evoked contractions were significantly higher than in measurements performed after the first bout (p < 0.05). Although low-frequency fatigue significantly increased up to 48 hours after each bout of eccentric exercise, its values at 24 and 48 hours after the second bout were significantly lower than at respective time points after the first bout (p < 0.05). Double to single twitch ratio could be used as a sensitive tool in the evaluation of muscle recovery and adaptation to repeated eccentric exercise.

Spike shape analysis of electromyography for parkinsonian tremor evaluation.

INTRODUCTION: Standard electromyography (EMG) parameters have limited utility for evaluation of Parkinson disease (PD) tremor. Spike shape analysis (SSA) EMG parameters are more sensitive than standard EMG parameters for studying motor control mechanisms in healthy subjects. SSA of EMG has not been used to assess parkinsonian tremor. This study assessed the utility of SSA and standard time and frequency analysis for electromyographic evaluation of PD-related resting tremor. METHODS: We analyzed 1-s periods of EMG recordings to detect nontremor and tremor signals in relaxed biceps brachii muscle of seven mild to moderate PD patients. RESULTS: SSA revealed higher mean spike amplitude, duration, and slope and lower mean spike frequency in tremor signals than in nontremor signals. Standard EMG parameters (root mean square, median, and mean frequency) did not show differences between the tremor and nontremor signals. CONCLUSIONS: SSA of EMG data is a sensitive method for parkinsonian tremor evaluation.

Interval training-induced alleviation of rigidity and hypertonia in patients with Parkinson's disease is accompanied by increased basal serum brain-derived neurotrophic factor.

OBJECTIVE: To examine the effects of cycloergometric interval training on parkinsonian rigidity, relaxed biceps brachii muscle tone in affected upper extremities, and serum level of brain-derived neurotrophic factor. DESIGN: Case series, repeated-measures design, pilot study. SUBJECTS/PATIENTS: Eleven patients with mild-to-moderate Parkinson's disease (Hoehn & Yahr scale 2.3 ± 0.72), recruited from a neurological clinic, underwent cycle training and were tested along with non-trained, healthy control subjects (n = 11) in a motor control laboratory. METHODS: Patients underwent 8 weeks of interval training (3 × 1-h sessions weekly, consisting of a 10-min warm-up, 40 min of interval exercise, and 10-min cool-down) on a stationary cycloergometer. Parkinsonian rigidity (Unified Parkinson's Disease-Rating-Scale) in the upper extremity, resting biceps brachii muscle tone (myometric stiffness and frequency), and brain-derived neurotrophic factor level were measured 1-3 days before interval training cycle started and 6-10 days after the last training session. RESULTS: Training resulted in a decrease in rigidity (p = 0.048) and biceps brachii myometric muscle stiffness (p = 0.030) and frequency (p = 0.006), and an increase in the level of brain-derived neurotrophic factor (p = 0.035) relative to pre-training values. The increase in brain-derived neurotrophic factor level correlated with improvements in parkinsonian rigidity (p = 0.025), biceps brachii myometric stiffness (p = 0.001) and frequency (p = 0.002). CONCLUSION: Training-induced alleviation of parkinsonian rigidity and muscle tone decrease may be associated with neuroplastic changes caused by a training-induced increase in the level of brain-derived neurotrophic factor.

Electromyogram features during linear torque decrement and their changes with fatigue.

PURPOSE: Surface electromyogram (EMG) spike shape analysis (SSA) has recently been proposed as an adjunct tool to EMG time and frequency domain analysis to increase our knowledge of motor unit (MU) control strategies. The study was aimed to understand more in MU deactivation strategy during torque decrement, and its possible changes in fatigued muscle, using a combination of traditional time and frequency domain analysis and SSA techniques. METHODS: EMG was detected from the biceps brachii of 11 untrained male subjects during static down-going ramp contractions (90-0% of the maximal voluntary contraction, MVC) under non-fatigued (DGR) and fatigued (FDGR) conditions. The root mean square (RMS) and mean frequency (MF), as well as SSA parameters, were calculated on 1-s EMG windows centred on each 10 % MVC step for both conditions. RESULTS: In both the DGR and FDGR EMG-RMS, mean spike amplitude and mean spike slope decreased by 50 % in the 90-60 % MVC. The mean spike frequency also decreased by 50 % in the 30-10 % MVC. Except the "mean number of spikes per second" all the other estimated EMG parameters were significantly different during FDGR compared to DGR. CONCLUSION: The dynamics of EMG parameters during torque decrement would support a MU deactivation strategy which relies more on MU de-recruitment in the high % MVC range and more on firing rate reduction in the low % MVC range. The adopted integrated approach to EMG signal processing could indicate that SSA is an important tool to disclose alterations in motor control due to fatigue.

Effects of submaximal eccentric exercise on muscle activity at different elbow joint angles.

Our study aimed to determine whether electrical and mechanical factors contributing to acute or long-term maximal torque reduction and muscle soreness due to submaximal eccentric exercise (ECC) are elbow-joint-angle specific and to what extent the joint angle affects the contribution of antagonist coactivation to this torque reduction. Maximal isometric torque (MIT), muscle soreness assessment, agonist electromechanical activities, and antagonist coactivation during the maximal voluntary contraction (MVC) were measured at elbow joint angles of 60°, 90°, and 150° before ECC, immediately after exercise, and 24, 48, 72, and 120 hr after exercise. ECC causes an immediate decrease in MIT as well as increased antagonist coactivation at three angles. Antagonist coactivation returned to its baseline level at 24 hr regardless of joint angle. The most rapid torque recovery and the highest force level at which pain occurred were found after ECC at a joint angle of 60°. During the recovery period, no mechanomyographical changes were observed when measuring surface mechanomyography changes at three angles, while the electrical activity differed between angles.

Twitch mechanical properties after repeated eccentric exercise of the elbow flexors.

The purpose of this study was to assess if the protective adaptation after eccentric exercise affects changes of twitch contractile properties of the biceps brachii muscle. Maximal isometric torque (MVC), twitch contractile properties, muscle soreness, and relaxed elbow angle (RANG) assessments were measured in 12 untrained, right-handed male volunteers (age, 23 ± 2 years; height, 182 ± 5 cm; mass, 75 ± 7 kg) before, immediately after, 48 h, and 120 h following each bout of eccentric exercise that consisted of 30 repetitions of lowering a dumbbell adjusted to 75% of each individual's maximal isometric torque of the right elbow flexors. MVC, peak twitch torque, maximal rate of twitch torque development, maximal rate of relaxation, muscle soreness, and RANG changes were significantly attenuated after the second bout of eccentric exercise when compared with the first bout. In contrast, time to twitch peak torque and half relaxation time did not change significantly after both the first and the second bout. The findings indicate that the mechanisms responsible for rapid adaptation affect some twitch mechanical properties such as peak torque, maximal rate of torque development, and maximal rate of relaxation but not time to peak torque and half relaxation time.

Myometry revealed medication-induced decrease in resting skeletal muscle stiffness in Parkinson's disease patients.

BACKGROUND: Based on combined analysis of clinical assessment of parkinsonian rigidity (constant resistance force generated during passive movement in a joint), electromyography and/or dynamometry many studies showed objectively that anti-parkinsonian medication decreases the rigidity in Parkinson's disease (PD). Rigidity-related changes in resting muscle stiffness (changed muscle's mechanical property related to its structural changes and changed neural drive) in PD patients have been revealed by myometry, a simple, sensitive, and reliable method for measuring mechanical properties in human soft tissues. However, an application of myometry in estimation of medication effects on the PD rigidity-related muscle stiffness has not been reported yet. Therefore, our study aimed to assess medication-induced changes in resting muscle stiffness in PD patients using myometry. METHODS: We measured resting muscle stiffness by myometry and recorded a surface electromyogram of relaxed biceps brachii, brachioradialis and triceps brachii muscles in ten patients with PD (age: 51-80 years; Hoehn and Yahr stage: 2.5-4) during medication on-phase (when subjects felt best comfort and fitness after medication: Levodopa, Piribedil, Ropinirol) and medication off-phase (12h after withdrawal of the medication). FINDINGS: Our patients had significantly lower myometric stiffness and electromyogram amplitude in all tested muscles, and also lower clinical rigidity scores during the medication on-phase compared with the medication off-phase. INTERPRETATION: Myometry revealed that anti-parkinsonian medication decreases not only rigidity in PD, but also rigidity-related stiffness in resting skeletal muscles in PD patients. These findings show that myometry can enrich neurological practice, by allowing objective and reliable assessment of parkinsonian rigidity treatment effectiveness.

Muscle stiffness at different force levels measured with two myotonometric devices.

Myotonometric measurements are quantitative methods of muscle tone assessment and may be used as an alternative for palpation evaluation. The objective of the study was to compare the measurements of brachioradialis muscle tone and stiffness using the Myoton-3 and the Myotonometer. The participants were young males (N = 17, mean age 21 ± 1 years). The skeletal muscle state was expressed by the Myoton-3 parameters stiffness (N m(-1)), frequency (Hz) and decrement (no unit) and the Myotonometer's area under the curve (AUC) parameter (area under the curve, no unit), when muscle was at rest and during activity at 25%, 50%, 80% and 100% of maximal voluntary contraction for elbow flexors. Pearson's correlation between AUC and stiffness is r = -0.89, AUC and frequency r = -0.84 and AUC and decrement r = 0.79, p < 0.01. When comparing the results from each experimental condition separately for frequency and AUC, the correlation was from -0.63 to -0.80, for stiffness and AUC it ranged from -0.25 to -0.75 and for decrement and AUC from 0.27 to 0.74. The degree of correlation between myotonometric measurements depends on whether the measured muscle is at rest or during contraction. The correlation is diverse among related parameters.

Increased muscle belly and tendon stiffness in patients with Parkinson's disease, as measured by myotonometry.

BACKGROUND: Based on Davis's law, greater tonus of the muscle belly in individuals with Parkinson's disease can create greater tension in the tendon, leading to structural adjustment and an increase in tendon stiffness. Our study aimed to separately assess passive stiffness in the muscle belly and tendon in medicated patients with Parkinson's disease, using myotonometry. METHODS: We tested 12 patients with Parkinson's disease and 12 healthy matched controls. Passive stiffness of muscle belly and tendon was estimated by myotonometry, electromyography, and mechanomyography in relaxed biceps and triceps brachii muscles. RESULTS: Compared with controls, patients with Parkinson's disease had higher stiffness in the muscle belly and tendon of the biceps brachii and in the tendon of the triceps brachii. In patients with Parkinson's disease, there was a positive correlation between muscle belly stiffness and parkinsonian rigidity in the biceps brachii. CONCLUSION: Patients with Parkinson's disease have higher passive stiffness of the muscle belly and tendon than healthy matched controls.

Muscle passive stiffness increases less after the second bout of eccentric exercise compared to the first bout.

OBJECTIVES: The purpose of this study was to assess if the protective adaptation after eccentric exercise affects changes in passive stiffness of the biceps brachii muscle. DESIGN: A within-group repeated measures design was used to compare changes in passive muscle stiffness after eccentric exercise between the first and second bouts separated by 2-3 weeks. METHOD: Maximal isometric torque, passive muscle stiffness and soreness were measured on the right elbow flexors in 14 untrained male volunteers before, immediately after, 24, 48 and 120 h following each bout of eccentric exercise that consisted of 30 repetitions of lowering a dumbbell adjusted to 75% of each individual's maximal isometric torque. RESULTS: Maximal isometric torque reduced immediately after the first bout by 24 ± 11% (mean ± SD; P < 0.05) and remained decreased for the next 120 h (~23%). Passive muscle stiffness immediately increased from 223 ± 19 N/m to 254 ± 22 N/m (P < 0.05) and remained higher for 120 h. After the second bout maximal isometric torque decreased 21 ± 13%, and 48 h later recovered to pre-exercise level (P < 0.05). Increase in passive muscle stiffness was attenuated after the second bout (238 ± 17 N/m; P < 0.05). The perceived muscle soreness was lower after the second bout. CONCLUSIONS: Smaller increases in passive muscle stiffness and soreness, and faster maximal isometric torque recovery after the second bout of eccentric exercise could result from adaptation process that occurred after the first bout.

Weakening of synergist muscle coupling during reaching movement in stroke patients.

BACKGROUND: After hemiparetic stroke, coordination of the shoulder flexor and elbow extensor muscles during a reaching movement is impaired and contributes to poor performance. OBJECTIVE: The aim was to determine whether functional coupling between electromyographic signals of synergist muscles during reaching was weakened in stroke patients who had poor motor coordination. METHODS: Surface electromyography (EMG) from the anterior deltoid, triceps brachii, biceps brachii, pectoralis major, supraspinatus, and latissimus dorsi of the affected upper limb in 11 stroke patients (mean Fugl-Meyer upper extremity score 27 ± 8) and in the dominant arm of 8 healthy controls were measured. RESULTS: Coherence between the EMG of the anterior deltoid and triceps brachii, 2 synergists for reaching, was lower in patients compared with controls, in the 0- to 11-Hz range. Detailed segmented frequency-range analysis indicated significant differences in the coherence between groups in 0- to 3.9-Hz and 4- to 7.9-Hz ranges. CONCLUSIONS: This weakened functional coupling may contribute to poor reaching performance and could be a consequence of a loss of common drive at the frequency bands as a result of interruption of information flow in the corticospinal pathway.

Higher muscle passive stiffness in Parkinson's disease patients than in controls measured by myotonometry.

OBJECTIVE: To assess muscle passive stiffness in medicated Parkinson's disease patients using myotonometry. DESIGN: Case-control study. SETTING: Kinesiology laboratory. PARTICIPANTS: Women with Parkinson's disease (PD) (n=8) and healthy matched elderly women (controls) (n=10) (mean age: PD, 77+/-3y; controls, 77+/-4y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Passive stiffness of relaxed biceps brachii (BB) muscle was measured using myotonometry. Additionally, surface electromyographic and mechanomyographic signals were recorded from the muscle at rest, and amplitude of those signals was analyzed offline. RESULTS: The values of BB muscle passive stiffness were significantly (P=.004) higher in PD than in the controls, with a statistically significant influence of parkinsonian rigidity score (Unified Parkinson's Disease Rating Scale) on intergroup differences (P<.001). The Spearman correlation coefficient rho value showed a significant (P=.005) positive relationship (rho=.866) between the parkinsonian rigidity score and passive stiffness values of BB in PD. The groups did not differ significantly in the electromyogram amplitude (P=.631) and mechanomyogram amplitude (P=.593) of the BB muscle, and values of these parameters did not correlate significantly with rigidity score (P=.555, P=.745, respectively) in the patients. CONCLUSIONS: Myotonometer is a sensitive enough tool to show that PD patients have higher muscle passive stiffness than healthy controls.

Electromyography and mechanomyography of elbow agonists and antagonists in Parkinson disease.

The purpose of this study was to assess the electromyographic (EMG) and mechanomyographic (MMG) activities of agonist and antagonist muscles in Parkinson disease patients during maximal isometric elbow contraction in flexion and extension. Ten elderly females with Parkinson disease (average age 75 years) and 10 age-matched healthy females were tested. The torque and the EMG and MMG signals from biceps brachii and triceps brachii were recorded during sustained maximal voluntary isometric contraction of the elbow flexors and extensors. There were no intergroup differences in the EMG and MMG activities of agonist and antagonist muscles or in torque. This might be because the Parkinson subjects were tested during their medication "ON" phase, or perhaps maximal isometric contraction (MVC) induced greater active muscle stiffness that affected the MMG signal. Muscle Nerve 40: 240-248, 2009.