Elbow Extensors Research Articles

Does the use of an armrest modify upper extremity muscle demands during lateral sitting transfers in manual wheelchair users living with spinal cord injury?

Performing sitting transfers figures among the most demanding activities in manual wheelchair users living with spinal cord injury (MWU SCI ). Surprisingly, little is known about how the built environment may change movement strategies and upper extremity (UE) muscle demands during transfers. This study aims to determine to what extent the use of an armrest changes UE muscle demands during lateral sitting transfers in MWU SCI . Twenty MWU SCI performed lateral transfers toward the left under three experimental conditions: 1. without armrest, 2. with a left armrest at 9 cm, 3. with a left armrest at 18 cm above seat surface. Bilateral recorded EMG signals of the anterior deltoid, pectoralis major, biceps, and triceps were selected for analysis. Muscular utilization ratio (MUR) was obtained through amplitude-normalization using maximum voluntary contractions. Peak MUR and area under the MUR curve (AUC) of each muscle were compared across conditions using a non-parametric ANOVA. When transferring using the 9-cm armrest, the peak MUR increased in both triceps and decreased in left anterior deltoid, while the AUC decreased in right biceps compared to transfers without armrest. When transferring using the 18-cm armrest, the peak MUR increased in both triceps and decreased in left anterior deltoid and biceps, while AUC decreased in both biceps compared to transfers without armrest. Furthermore, the peak MUR increased in left pectoralis major compared to transfers using the 9-cm armrest. The use of an armrest during sitting transfers shifts part of the UE muscle demands from the shoulder flexors to the elbow extensors in MWU SCI . This adaptation may be linked to a reduced forward trunk flexion during transfer, although a confirmatory kinematic analysis is needed. Nonetheless, the availability of an armrest during transfers provides additional opportunities to vary UE muscle demands and to minimize UE musculoskeletal risk exposure.

The Influence of Visual, Vestibular, and Hindlimb Proprioceptive Ablations on Landing Preparation in Cane Toads

Coordinated landing from a jump requires preparation, which must include appropriate positioning and configuration of the landing limbs and body to be successful. While well studied in mammals, our lab has been using the cane toad (Rhinella marinus) as a model for understanding the biomechanics of controlled landing in anurans, animals that use jumping or bounding as their dominant mode of locomotion. In this article, we report new results from experiments designed to explore how different modes of sensory feedback contribute to previously identified features of coordinated landing in toads. More specifically, animals in which vision, hindlimb proprioception, or vestibular feedback were removed, underwent a series of hopping trials while high-speed video was used to record and characterize limb movements and electromyographic (EMG) activity was recorded from a major elbow extensor (anconeus). Results demonstrate that altering any sensory system impacts landing behavior, though loss of vision had the least effect. Blind animals showed significant differences in anconeus EMG timing relative to controls, but forelimb and hindlimb movements as well as the ability to successfully decelerate the body using the forelimbs were not affected. Compromising hindlimb proprioception led to distinctly different forelimb kinematics. Though EMG patterns were disrupted, animals in this condition were also able to decelerate after impact, though with less control, regularly allowing their trunks to make ground contact during landing. Animals with compromised vestibular systems showed the greatest deficits, both in takeoff and landing behavior, which were highly variable and rarely coordinated. Nevertheless, animals in this condition demonstrated EMG patterns and forelimb kinematics similar to those in control animals. The fact that no ablation entirely eliminates all aspects of landing preparation suggests that its underpinnings are complex and that there is no single sensory trigger for its initiation.

Effects of equal-volume resistance training with different training frequencies in muscle size and strength in trained men.

BackgroundThe objective of the present study was to compare the effects of equal-volume resistance training (RT) performed with different training frequencies on muscle size and strength in trained young men.MethodsSixteen men with at least one year of RT experience were divided into two groups, G1 and G2, that trained each muscle group once and twice a week, respectively, for 10 weeks. Elbow flexor muscle thickness (MT) was measured using a B-Mode ultrasound and concentric peak torque of elbow extensors and flexors were assessed by an isokinetic dynamometer.ResultsANOVA did not reveal group by time interactions for any variable, indicating no difference between groups for the changes in MT or PT of elbow flexors and extensors. Notwithstanding, MT of elbow flexors increased significantly (3.1%, P < 0.05) only in G1. PT of elbow flexors and extensors did not increase significantly for any group.DiscussionThe present study suggest that there were no differences in the results promoted by equal-volume resistance training performed once or twice a week on upper body muscle strength in trained men. Only the group performing one session per week significantly increased the MT of their elbow flexors. However, with either once or twice a week training, adaptations appear largely minimal in previously trained males.

Comparison of Elbow Extensor Muscle Strength and EMG Activity in Supine and Prone Positions in Healthy Subjects

Background There is little research on the strength and electromyograph (EMG) activity of elbow extensors according to the measuring posture. Purpose We investigated which posture influenced strength and EMG activity of elbow extensors in evaluating postures (supine and prone). Study design Comparative, repeated measures design. Methods Twenty-one healthy subjects performed maximal elbow extension in two postures (supine and prone). EMG activity was measured in the anconeus, long head of triceps (LoT), and lateral of triceps (LT). When measuring EMG activity of elbow extensors, the strength of elbow extensors was also measured by Smart KEMA strength measurement system. Results In supine, EMG activity of anconeus and LT was significant increased. The other way, EMG activity of LoT and strength of elbow extensors were significant increase in the prone position. Conclusions We recommend the prone position to increase EMG activity of LoT and to improve strength of elbow extensors. In addition, supine position should be considered to increase muscle activity of anconeus and LT.

Triceps Brachii Muscle Strength and Architectural Adaptations with Resistance Training Exercises at Short or Long Fascicle Length

The aim of this study was to investigate whether resistance training at short or long triceps brachii fascicle length induces different muscular strength and architectural adaptations. Nine young, novice, female participants, were trained for 6 weeks (two sessions/week) performing 6 sets × 6-RM (repetition maximum) unilateral cable exercises either with push-downs at short fascicle length (S) or overhead extensions with the contralateral arm at long fascicle length (L) of triceps brachii. Before and after training, 1-RM elbow extension and triceps brachii muscle architecture were evaluated. Muscle architecture was analyzed at 50% and 60% of the upper-arm length. Two-dimensional longitudinal muscle area of the triceps long head was also analyzed. The results indicated that 1-RM increased 40.1 ± 21.3% and 44.5 ± 20.1% (p &lt; 0.01) after S and L, respectively. Muscle thickness at 50% length was increased 10.7 ± 15.3% (p &lt; 0.05) and 13.7 ± 9.0% (p &lt; 0.01) after S and L, while at 60% it was increased 15.5 ± 18.8% (p &lt; 0.05) and 19.4 ± 16.3% (p &lt; 0.01), respectively. Longitudinal muscle area increased similarly after S and L (p &lt; 0.01). Fascicle angle and length were not altered with training. These results indicate that muscle strength and architecture of elbow extensors adapt similarly during the first six weeks of resistance training at either long or short fascicle length.

Is the 6-minute pegboard and ring test valid to evaluate upper limb function in hospitalized patients with acute exacerbation of COPD?

BackgroundThe 6-minute pegboard and ring test (6-PBRT) is a useful test for assessing the functional capacity of upper limbs in patients with stable COPD. Although 6-PBRT has been validated in stable patients, the possibility of a high floor effect could compromise the validity of the test in the hospital setting. The aim of this study was to verify the convergent validity of 6-PBRT in hospitalized patients with acute exacerbation of COPD (AECOPD).MethodsA cross-sectional study was conducted in a tertiary hospital. Patients who were hospitalized due to AECOPD and healthy elderly participants, voluntarily recruited from the community, were considered for inclusion. All participants underwent a 6-PBRT. Isokinetic evaluation to measure the strength and endurance of elbow flexors and extensors, handgrip strength (HGS), spirometry testing, the modified Pulmonary Functional Status Dyspnea Questionnaire (PFSDQ-M), the COPD assessment test (CAT), and symptoms of dyspnea and fatigue were all measured as comparisons for convergent validity. Good convergent validity was considered if >75% of these hypotheses could be confirmed (correlation coefficient>0.50).ResultsA total of 17 patients with AECOPD (70.9±5.1 years and forced expiratory volume in 1 second [FEV1] of 41.8%±17.9% of predicted) and 11 healthy elderly subjects were included. The HGS showed a significant strong correlation with 6-PBRT performance (r=0.70; p=0.002). The performance in 6-PBRT presented a significant moderate correlation with elbow flexor torque peak (r=0.52; p=0.03) and elbow extensor torque peak (r=0.61; p=0.01). The total muscular work of the 15 isokinetic contractions of the elbow flexor and extensor muscles showed a significant moderate correlation with the performance in 6-PBRT (r=0.59; p=0.01 and r=0.57; p=0.02, respectively). Concerning the endurance of elbow flexors and extensors, there was a significant moderate correlation with 6-PBRT performance (r=−0.50; p=0.04 and r=−0.51; p=0.03, respectively). In relation to the upper-extremity physical activities of daily living (ADLs) assessed by means of PFSDQ-M, there was a significant moderate correlation of 6-PBRT with three domains: influence of dyspnea on ADLs (r=−0.66; p<0.001), influence of fatigue on ADLs (r=−0.60; p=0.01), and change in ADLs in relation to the period before the disease onset (r=−0.51; p=0.03). The CAT was also correlated with 6-PBRT (r=−0.51; p=0.03). Finally, the performance in 6-PBRT showed a significant moderate correlation with the increase in dyspnea (r=−0.63; p=0.01) and a strong correlation with the increase in fatigue of upper limbs (r=−0.76; p<0.001) in patients with AECOPD. Convergent validity was considered adequate, since 81% from 16 predefined hypotheses were confirmed. There was no correlation between 6-PBRT and patients’ height. The performance in 6-PBRT was worse in patients with AECOPD compared to healthy elderly individuals (248.7±63.0 vs 361.6±49.9 number of moved rings; p<0.001).ConclusionThe 6-PBRT is valid for the evaluation of functional capacity of upper limbs in hospitalized patients with AECOPD.

T80. Alteration of intermuscular coherence in synergistic muscle pairs during actual elbow flexion contractions after cervical spinal cord injury

Introduction During isometric contractions, the level of antagonist muscles activation is increased in people with cervical spinal cord injury (cSCI) in comparison to healthy participants. This alteration of antagonists activation after cSCI has been primarily associated with a lower cortical control of the spinal mechanisms – especially reciprocal inhibition – regulating agonists-antagonists co-activation. Through time-frequency intermuscular coherence analysis, which is likely to reflect the strength of the common neural drive across multiple muscles, this study investigates the influence of a cSCI on the common neural drive regulating the activity of agonist and antagonist muscles pairs. Methods The EMG of elbow flexors (biceps brachii, brachioradialis) and elbow extensors (long and short heads of the triceps brachii) was recorded while 8 participants with cSCI (SCI group) and 10 able-bodied participants (AB group) performed 21 isometric 6-s elbow isometric flexion contractions at 3 force levels (20%, 40% and 60% of MVC). The magnitude of intermuscular coherence between the EMG signals from elbow flexors (AGO-AGO), elbow extensors (ANTAGO-ANTAGO) and all possible pairs of elbow flexors-extensors (AGO-ANTAGO) was quantified in alpha (8–12 Hz), beta (15–30 Hz) and gamma (35–60 Hz) frequency bands. The magnitude of the intermuscular coherence and the mean net joint torque produced around the elbow joint were analyzed over a 2-s stable force production window for all contractions. The effects of the Force level and Group were tested using adequate statistical tests according to the distribution of the dependent variables. Results Results revealed that the net joint torque significantly increased with the Force level in both groups with no significant Group difference. In the beta-band, AGO-ANTAGO intermuscular coherence magnitude was significantly lower in the SCI group than in the AB group. In the gamma-band, the ANTAGO-ANTAGO intermuscular coherence magnitude significantly increased concomitantly with the Force level in both groups. No significant intermuscular coherence was found in the alpha-band, whatever the group and the muscle pair. Conclusion The alteration of AGO-ANTAGO intermuscular coherence magnitude in the beta-band after cSCI could reflect reduced common neural drive influencing the spinal inhibitory mechanisms. This finding may suggest lower common drive to agonist-antagonist muscle pairs in SCI participants, which could take part in the alteration of antagonist muscles co-activation. Increased ANTAGO-ANTAGO coherence magnitude with the force level revealed in the gamma-band could be related to the Piper rhythm phenomenon, which contributes to synchronize muscle activations to gain in efficiency, especially at high force levels. Despite lower intermuscular coupling between agonist and antagonist muscles, our results taken together support that the central mechanisms controlling the modulation of the force level are preserved during actual contractions after cSCI.

The Effects of Sex and Motoneuron Pool on Central Fatigue.

It is uncertain if sex influences central fatigue because the reduction in voluntary activation (VA) has been reported as not different between the sexes for elbow flexors (EF) but greater in males compared with females for knee extensors. This disparity could result from the facilitatory and inhibitory effects of group III/IV muscle afferents on flexor versus extensor motoneurons, respectively. The purpose of this study was to examine central fatigue and motoneuron responsiveness of EF and elbow extensors (EE) in males and females. Twenty-two participants (11 females) performed a 2-min isometric maximal voluntary contraction of EF and EE (on separate days) followed by 2 min of recovery. EMG potentials were recorded from biceps or triceps brachii in response to the stimulation of the brachial plexus (Mmax), corticospinal tract (cervicomedullary motor evoked potential [CMEP]), and motor cortex (motor evoked potential [MEP]). Superimposed and resting doublets (for determining VA) were evoked via muscle belly stimulation of biceps or triceps brachii. Only CMEP and superimposed doublets were recorded during fatigue. There was no effect of sex on CMEP area for either muscle group during fatigue or recovery. During the 2 min after EE fatigue, mean normalized CMEP and MEP area were ∼85% and ∼141% of control, indicating inhibition and facilitation of the motoneurons and motor cortex, respectively. VA during recovery was significantly reduced in males but not females for the EF, and unchanged in either sex for the EE. The findings do not support the concept that equivocal findings regarding sex differences in central fatigue are related to augmented effects of group III/IV afferent feedback in males compared with females.

A Muscle’s Functional Role Influences Movement Accuracy Before and After Eccentric Exercise

Eccentric muscle contractions, especially if unaccustomed and intense, can cause fatigue and muscle damage that contributes to acute decrements in motor performance. Because performance of motor tasks requires the precise coordination of agonist and antagonist musculature, the effect of the eccentric activity on accuracy will likely depend on the damaged muscle’s functional role as an agonist or antagonist in the task. PURPOSE: To compare the effect of fatiguing eccentric exercise (EE) on the accuracy of aiming movements when the EE muscle group’s function is that of an agonist or antagonist. METHODS: 16 untrained subjects (9 M, 7 F; 27 ± 3 yrs.) completed discrete horizontal pointing movements between 2 targets (13mm diameter) that required 40° of elbow movement. Twenty elbow-extension and 20 elbow-flexion pointing movements were performed with their right arm before and immediately after eccentric exercise of the elbow extensor muscles standardized by isokinetic dynamometry. Movement accuracy was quantified by the incidence (overall accuracy) and duration to initiation (magnitude of error) of secondary submovements that were identified by zero crossings in the tangential velocity and acceleration profiles. RESULTS: When the exercised muscles performed the pointing task as the agonist (i.e. extension movements), movement times (MT) were longer and peak velocity (PV) decreased after EE compared with before EE (MT= 222 ± 40, 248 ± 37ms, p<0.05; PV= 3.4 ± 0.6, 3.1 ± 0.6m/s, p<0.05). However, when the exercised muscle was the antagonist (i.e. flexion movements), MT and PV remained unchanged. There were more trials with no corrective submovements (i.e. more accurate) for the extension compared with flexion movements before EE (92% vs. 62%, p<0.001), but there was a greater decline in accurate trials after EE for the extension movements (78% vs. 41% decline p<0.0001). Furthermore, although initially similar, the duration of the primary submovement was shorter (further from target) after EE for the movements in which the agonist was the exercised muscle compared with an antagonistic role (62% vs. 73% of total movement time, p<0.001). CONCLUSIONS: There is a greater effect of EE-induced muscle fatigue and damage on movement kinematics and accuracy when the muscle’s functional role is agonistic.

Effect of voluntary teeth clenching and sitting posture on maximal static force of limb muscles.

People clench their teeth to activate facial, neck and abdominal muscles when they need to generate heavy muscle force against large resistance like lifting heavy objects, in order to gain possible ergogenic advantage. These are termed as remote voluntary contractions. Aim of this study was to evaluate the effect of voluntary teeth clenching on maximal voluntary contraction of extensors and flexors of the knee, shoulder and elbow joints of the dominant side during slouch and unsupported upright sitting. One hundred healthy young male adults (mean age 23.3 years) participated in this study. Maximal voluntary contraction was measured using a hand-held dynamometer. Jaw clenching caused different ergogenic effect during slouch versus unsupported sitting postures. The data revealed that during unsupported upright sitting, the effect of jaw clenching consistently results in larger maximal voluntary contraction of both extensor and flexor muscles of all the three studied joints. However, during slouch sitting, only the maximal voluntary contraction of extensors of elbow and flexors of knee were larger with clenched teeth position. Jaw clenching can affect the maximal voluntary contraction of limb muscles which is sitting posture dependent. Jaw clenching can consistently facilitate certain muscles of the upper and lower limbs to generate greater force production during upright sitting.

Biomechanical Profile of the Muscles of the Upper Limbs in Sport Climbers

Abstract Introduction. Studies have demonstrated an important role of muscle strength and endurance in climbing. However, little research has explored the speed parameters of the muscles of climbers. This study aimed to evaluate biomechanical indices of the functional status of the upper limbs in climbers. Material and methods. Group G1 (n = 3) were athletes who were able to climb 8c+/9a climbing routes using the red-point style and 7c+/8b routes with the on-sight style. Group G2 (n = 5) comprised climbers who were able to climb 8a/8b+ and 7b+/8a routes, respectively. Maximum muscle torques were measured in the elbow and arm flexors and extensors. Hand grip tests, dynamometric arm strength tests, and laboratory endurance tests were conducted. Results. Strength parameters in both joints were similar in the two groups of climbers. Maximum absolute values of hand grip, crimp grip, and global arm force in hanging did not differ between the groups. Furthermore, significant differences were found for relative indices (from circa 3% to circa 12%). No significant differences were recorded for the parameters of muscle speed. Furthermore, no significant effect of the subjects’ skill level on the results of endurance tests was found. The results obtained in the groups of athletes (G1, G2, and G1+2) were compared with the values recorded in a control group of students (GC, n = 48). Conclusions. Elite climbers were found to have an advantage over the controls only in strength and muscular endurance. No significant differences were observed in the results of speed tests in the muscles of the athletes and students examined in the study. The climbers (G1 and G2) differed in the strength potential of their muscles, but only when relative force indices were analysed. No differences were found in the biomechanical variables of speed and muscular endurance. Conventional tests are typically not a valuable diagnostic tool for the evaluation of climbers.

Modification of a sonographic enthesitis score to differentiate between psoriatic arthritis and young healthy volunteers

Objectives: We aimed to describe sonographic structural and inflammatory changes in entheses of patients with recently diagnosed psoriatic arthritis (PsA), patients with established PsA, and young healthy volunteers, and to investigate whether the MAdrid Sonographic Enthesitis Index (MASEI) enables us to distinguish these groups in an extreme comparison.Method: New and established PsA patients and healthy volunteers (aged 20–30 years) were recruited. The triceps, quadriceps, patellar, Achilles and elbow extensor tendon insertion, and plantar fascia entheses were investigated sonographically for structural changes, erosions, calcifications, increased thickness, bursitis, and power Doppler (PD) signal according to the MASEI.Results: The study included 25 new and 25 established PsA patients, and 25 healthy volunteers. Increased thickness and PD signal in knee entheses were common for patients and healthy volunteers, while changes at other locations predominantly occurred in patients only. PD was recoded (1, one spot; 1.5, two or three spots; 2, confluent signal; 3, severe confluent signal) and thickness of knee entheses excluded. This resulted in different modified MASEI scores between PsA patients and young healthy controls: median (interquartile range) modified MASEI of 13 (10–22.5) in new PsA, 13.5 (9.5–18) in established PsA, and 3 (1–8.5) in healthy volunteers (p = 0.002).Conclusions: Structural ultrasound changes and PD in entheses are common in both new and established PsA and healthy controls. MASEI score did not differentiate PsA patients from young healthy volunteers. After recoding of PD severity and excluding thickness of knee entheses, marked differences between PsA patients and healthy controls were observed.

Curve fitting problem: torque - velocity relationship with polynomials and Boltzmann sigmoid functions.

The aim of this study was to investigate the curve fitting and model selection problem of the torque-velocity relationship of elbow flexors and extensors in untrained females. The second goal was to determine the optimal models in different function classes and the best, among the optimal ones. Lastly, test the best models to predict the torque were tested. Using the polynomials (second - fourth degree) and Boltzmann sigmoid functions, and a different presentation of data points (averages, a point cloud, etc.), we determined the optimal models by both error criteria: minimum residual sum of squares and minimum of the maximal absolute residue. To assess the best models, we applied Akaike and Bayesian information criteria, Hausdorff distance and the minimum of the smallest maximal absolute residue and the predictive torque-velocity relationships of the best models with torque values, calculated beyond the experimental velocity interval. The application of different error and model selection criteria showed that the best models in the majority of cases were polynomials of fourth degree, with some exceptions from second and third degree. The criteria values for the optimal Boltzmann sigmoids were very close to those of the best polynomial models. However, the predicted torque-velocity relationships had physiological behavior only in Boltzmann's sigmoid functions, and their parameters had a clear interpretation. The results obtained suggest that the Boltzmann sigmoid functions are suitable for modeling and predicting of the torque-velocity relationship of elbow flexors and extensors in untrained females, as compared to polynomials, and their curves are physiologically relevant.

Relationship between Joint Position Sense, Force Sense, and Muscle Strength and the Impact of Gymnastic Training on Proprioception.

The aims of this study were (1) to assess the relationship between joint position (JPS) and force sense (FS) and muscle strength (MS) and (2) to evaluate the impact of long-term gymnastic training on particular proprioception aspects and their correlations. 17 elite adult gymnasts and 24 untrained, matched controls performed an active reproduction (AR) and passive reproduction (PR) task and a force reproduction (FR) task at the elbow joint. Intergroup differences and the relationship between JPS, FS, and MS were evaluated. While there was no difference in AR or PR between groups, absolute error in the control group was higher during the PR task (7.15 ± 2.72°) than during the AR task (3.1 ± 1.93°). Mean relative error in the control group was 61% higher in the elbow extensors than in the elbow flexors during 50% FR, while the gymnast group had similar results in both reciprocal muscles. There was no linear correlation between JPS and FS in either group; however, FR was negatively correlated with antagonist MS. In conclusion, this study found no evidence for a relationship between the accuracy of FS and JPS at the elbow joint. Long-term gymnastic training improves the JPS and FS of the elbow extensors.

EFFECT OF MOUTAIN BIKE SPIRGRIPS® ON TRANSMISSIBILITY OF MECHANICAL VIBRATIONS, PERCEIVED COMFORT, MUSCULAR ACTIVITY AND HAND GRIP FORCE

Background: Prolonged mountain biking can involve pain complain in the wrists due to the ulnar nerve compression when using traditional grips (Capitani et al., 2002; Eckman et al., 1975). This phenomenon seems to be amplified by mechanical vibrations that are largely encountered during MTB practice despite the use of damping systems located in the fork and/or the frame. Recently, SPIRGRIPS® (SG) have been designed to correct the position of the hands of the user naturally by aligning the joints of his forearms correctly which is not the case with traditional grips. Purpose: The aim of this experimental study was to evaluate the effect of SG on transmissibility of mechanical vibrations, perceived comfort, muscular activity and hand grip force during a prolonged pedalling exercise. Methods: Sixteen trained cyclists without SG experience (age: 27 ± 10 years; height: 178 ± 6 cm; mass: 70 ± 7 kg) volunteered to participate in the study. Each participant performed a one-day laboratory cycling test on an aluminium hardtail mountain bike (Merida, Taiwan, Taiwan) equipped with a wireless SRM crank powermeter (Schoberer Rad Messtechnik, Fuchsend, Germany; accuracy ± 1%). The rear wheel of the bike was fixed onto an electromagnetic-braked ergometer (Elite, Fontaniva, Italy) while the front fork of the bike was connected to an electrical motor by a mechanical pivot. The test included two 20-minutes pedalling sessions at ~200 W that were separated by 20-minutes of passive recovery. Each pedalling session contained two pedalling periods of 9 minutes with fork vibrations interspersed by 2 min of pedalling without fork vibrations. Mechanical vibrations delivered by the motor were characterized by vertical acceleration from 12 to 53 m.s -2 and vibration frequency from 4 to 17 Hz. Participants had to keep their hands on the traditional grips (TG) or on the ergonomic SG throughout the pedalling session. All the subjects reported their ratings of perceived comfort (RPC) on a visual numeric scale graded from 0 (very much uncomfortable) to 10 (very much comfortable) approximately 10 seconds before the end of pedalling bout. Mechanical vibrations were simultaneously measured at 1350 Hz on the mechanical pivot of the ergometer and the right wrist of the rider by two Hikob Fox inertial measurement units (HIKOB, Vileurbanne, France). Surface EMG activity of flexor carpi radialis (FCR), extensor digitorum (ED) and triceps brachii (TB) were continuously measured by Trigno sensors (Delsys, Boston, USA) which are composed of two dry bar electrodes (1 mm x 10 mm) spaced by 10 mm. Maximum voluntary grip force (MVGF) of right hand was measured by an electronic force transducer one minute before and one minute after each pedalling session. Statistical analysis was assessed by paired t-test (MVGF) and two way (grips x vibration frequency) repeated measured ANOVA (RMS of EMG and vertical acceleration data) by Statistica (Statsoft, Tulsa, USA). Results: While MVGF decreased by 7% after pedalling exercise with TG (p < 0.05), no significant change in MVGF was found with SG. Transmissibility of vertical acceleration to the wrist was higher with SG when vibration frequency exceeds 8 Hz (Figure 2), but the difference with the TG was only significant at 17 Hz. EMG activity of FCR and TB muscles was lower with SG, notably for the highest vibration frequencies (12 and 14 Hz). RPC was not significantly different between the two grips whatever the vibration frequency.  Conclusion: This study showed that the use of MTB SPIRGRIPS® decreases fingers flexor and elbow extensor muscle activity while increasing vibration transmissibility to the wrist. In addition, maximum voluntary grip force was not altered after a prolonged pedalling exercise with vibrations. Therefore, these ergonomic grips would be interesting for mountain bikers to keep force reserve in hand and forearm for braking in steeper downhill and/or driving bike in technical sections. Acknowledgment : The authors would like to thank Pascal Badollet founder of SPIRGRIPS®, for his technical helpful.

A Preceding Bout of Endurance Exercise Decreases Peak Power of the Arm Extensor Muscles

The combination of aerobic exercise (AE) and resistance exercise (RE) within a given training protocol, termed concurrent training (CT), lacks sufficient analysis concerning the upper body. In the lower body knee extensor muscles, we have previously demonstrated reduced peak power when AE precedes RE. However, postural requirements of the lower body, as compared to the upper body, may give rise to unique responses following CT. Thus, further investigation as to specific peak power alterations of the upper body muscles are warranted. PURPOSE: To investigate the effects of a preceding AE bout on muscle strength to subsequent RE of the arm extensors. METHODS: Healthy men (n=8) performed AE+RE (CT) for the elbow extensors in one arm, while the contralateral arm performed RE only. The AE consisted of unilateral, moderate endurance exercise (43±2 min of repeated elbow extensions) using an isokinetic dynamometer. After 15-min rest, subjects performed unilateral RE (4x7 iso-inertial RE) with a flywheel device for both arms targeting the arm extensor muscles. Work produced during AE and peak concentric power during RE were recorded. RESULTS: The AE bout resulted in a gradual increase in heart rate (126±12 bpm) with a parallel increase in RPE reaching the termination threshold (18±0.5 RPE). The implementation of AE prior to RE led to a 21% decrease (p=0.045) in arm extensor peak concentric power from 98W to 78W, respectively. There was no change in performance from pre- to post in the RE-only arm (94W to 89W). CONCLUSIONS: These results demonstrate that the implementation of AE prior to RE, as compared to RE alone, compromises peak concentric power adaptations of the arm extensors. The noticeable decrement in peak concentric power between pre- and post from the CT intervention (21%), relative to a similar study with the same testing protocol which targeted the lower body (10%), gives credence to the possibility that upper and lower body muscles respond differently to concurrent training.

Methodological considerations in the calculation of the rate of force development scaling factor

Objective: Within this methodological study, we aimed to explore the effects of seven different commonly applied routines for rate of force development (RFD) calculation on the calculation of rate of force development scaling factor (RFD-SF) and r2 and the between session reliability of RFD-SF in three different muscle groups. Approach: We tested grip force muscles, elbow extensors and knee extensors of 13 healthy subjects asking them to produce around 120 rapid isometric force pulses per muscle to varying submaximal amplitudes. Then, we applied different filtering and analysis procedures, such as different filtering cut-off frequencies (no filter, 5 Hz cut-off, 10 Hz cut-off) and time windows during which RFD was calculated (0–50 ms, 0–75 ms, 0–100 ms and time from onset of contraction to peak force (PF) value). RFD-SF and r2 were obtained from the relationship between the PF and the corresponding RFD. Results: Our results showed that the magnitude of the calculated RFD-SF and r2 values significantly differed among different RFD calculation methods (p < 0.0005), but that r2 was high in most applied methods (RFD-SF ranged between 4.6 and 17.7, while r2 ranged between 0.63 and 0.98). Regardless of the tested muscle group and applied method to calculate RFD, the reliability of the calculated RFD-SF was moderate (0.5 < ICC3,1 < 0.75) to good (ICC3,1 > 0.75). The highest r2, highest ICC, lowest SEM% and MDD% were observed in case of RFD calculated during first 100 ms and when cut-off filter at 5 Hz was applied, indicating those two methods as the most appropriate ones. Significance: Our study contributes to the establishment of methodological suggestions that will help in maximizing the reliability of RFD-SF measurements, collecting normative data, and comparing results among different populations and lab settings.

Acute effects of maximal isometric muscle action of the elbow extensors on contralateral dynamic task of the elbow flexors: a pilot study

Acute effects of maximal isometric muscle action of the elbow extensors on contralateral dynamic task of the elbow flexors: a pilot study

Modulation of corticospinal output in agonist and antagonist proximal arm muscles during motor preparation.

Previous studies have shown modulation of corticospinal output of the agonist muscle when a known-movement is prepared but withheld until a response signal appearance, reflecting motor preparation processes. However, modulation in the antagonist muscles has not been described, despite the fact that reaching movements require precise coordination between the activation of agonist and antagonist muscles. In this study, participants performed an instructed-delay reaction time (RT) task, with randomized elbow flexion and extension movements. The aim was to assess the time course modulation of corticospinal output in two antagonist muscles, by simultaneously quantified the amplitude of motor evoked potentials (MEPs) in biceps brachii and triceps brachii, and the amplitude and direction of elbow movements evoked by transcranial magnetic stimulation (TMS). Depending on the prepared movement direction, a specific modulation of corticospinal output was observed, MEPs and TMS-evoked movements amplitude being relatively greater for extension compared to flexion. At the end of motor preparation, a decrease in MEPs amplitude was observed for both biceps brachii and triceps brachii, regardless of the prepared movement direction. In contrast, the probability of evoking movement in the flexion direction and the amplitude of TMS-evoked movement decreased at the end of preparation for flexion, but not for extension. Together, these results confirm the existence of inhibitory processes at the end of the motor preparation, probably to avoid a premature motor response. Moreover, they provide evidence of differences in the corticospinal control of elbow flexor and extensor muscles with patterns of modulation that are not necessarily reciprocal during motor preparation.

Cluster analysis of novel isometric strength measures produces a valid and evidence-based classification structure for wheelchair track racing

BackgroundThe Para athletics wheelchair-racing classification system employs best practice to ensure that classes comprise athletes whose impairments cause a comparable degree of activity limitation. However, decision-making is largely subjective and...