Isometric Dynamometer Research Articles

The Influence Of Age On The Recovery From Worksite Resistance Exercise In Firefighters

Worksite resistance training may reduce injuries and improve performance in firefighters, however aging may prolong the recovery process. PURPOSE: This study examined the influence of age on recovery following an acute bout of worksite resistance training. METHODS: Nineteen young and 19 older career firefighters (FFs) completed an acute bout of resistance exercise in addition to pre- and post-testing 24, 48, and 72 hours post-exercise. A work-related fatigue (WRF) survey was completed to assess daily fluctuations in work demands. Ultrasonography was used to assess cross-sectional area (CSA) and echo intensity (EI) of the vastus lateralis, in addition to muscle thickness (MT) and EI of the biceps brachii. To determine maximal jump height and associated velocity, participants completed 3-4 countermovement jumps while standing on a jump mat with a linear transducer attached at the waist. Upper-body peak force (PF) was measured during an isometric upright row task, using a calibrated tension-compression load cell. Lower body PF was examined with the participants seated in a custom-built, calibrated isometric dynamometer and their right knee flexed at 60 degrees. Following 3 submaximal warm-up contractions, participants performed 3 maximal voluntary contractions for each strength assessment lasting 3-4 s. The FFs completed the circuit-style resistance exercise bout following pre-testing, which included 3 sets of 8-10 repetitions at 80% of their predicted 1-repetition maximum of the deadlift, shoulder press, lunge, and upright row. Linear mixed models, controlling for WRF, were used to analyze all primary outcomes, with subject as the random effect and group and time as fixed effects. Alpha level was set a priori at 0.05. RESULTS: There was a significant group by time interaction effect for WRF (P=0.002) and was controlled for in subsequent analyses. There were no other significant group by time interactions (P>0.171). Collapsed across time, young FFs showed greater lower body PF (P=0.006), jump performance (P<0.024), and lower VL EI (P=0.008) values. Across time points, upper-body PF (P=0.023) and jump performance (P<0.029) decreased as muscle size increased (P<0.006) for both groups. CONCLUSION: These results indicate that age may not influence the recovery from a bout of worksite resistance exercise in FFs.

Validity and Reliability of Isometric-Bench for Knee Isometric Assessment.

There is a strong need for a new, probably cheaper, smaller, and more portable isometric dynamometer. With this aim, we investigated the concurrent validity and reliability of a low-cost portable dynamometer to measure the isometric strength of the lower limb. Seventeen young participants (age 16.47 ± 0.51 years) were randomly assessed on three different days for knee flexion and extension isometric forces with two different devices: a commonly used isokinetic dynamometer (ISOC) and a portable isometric dynamometer prototype (ISOM). No significant differences were observed between the ISOC and the ISOM (all comparisons p > 0.05). Test–retest comparison showed the ISOM to have high reliability (ICC 0.879–0.990). This study showed that measurements with the ISOM could be performed without systematic bias and with high reliability. The ISOM is a device that is able to assess knee isometric strength with excellent concurrent validity and reliability.

Prospective Evaluation of Changes in Pain Levels, Quality of Life and Functionality After Low Dose Radiotherapy for Epicondylitis, Plantar Fasciitis, and Finger Osteoarthritis.

Background: The objective benefits of low dose radiotherapy (LDRT) for non-malignant joint disorders are controversial. This study evaluated changes in pain, quality of life (QoL) and function after LDRT for epicondylitis, plantar fasciitis, and finger osteoarthritis.Materials and Methods: Patients over 40 years old with epicondylitis, plantar fasciitis, and finger osteoarthritis were had pain following at least 6 months of conservative therapy. Patients received 0.5 Gy LDRT twice weekly for 4 weeks repeated once after 8 weeks in patients who failed to achieve complete pain relief. Patients assessed their pain according to the visual analog scale. Handgrip strength was measured with an isometric dynamometer and the fast self-paced walking test was used in patients with plantar fasciitis. QoL was evaluated according to the EQ-5D and HAQ-DI questionnaires.Results: Outcomes for 157 patients (204 sites) were documented at 2, 6, and 12 months after last LDRT. Pain reduction at rest (p < 0.001), during activity (p < 0.001) and increase in handgrip strength (extension p < 0.001, flexion p = 0.002) were highly significant for patients with lateral epicondylitis. Patients with medial epicondylitis reported pain relief at rest (p = 0.041) and during activity (p = 0.041) and significant increase in handgrip strength (p = 0.022). Patients with plantar fasciitis reported pain reduction at rest (p < 0.001), during activity (p < 0.001) and faster walking times (p < 0.001). A trend toward improved QoL was observed. Patients with finger osteoarthritis reported significant pain relief during activity (p < 0.001) and a gain in handgrip strength (p = 0.004), with a trend to both pain relief at rest (p = 0.056) and stronger pinch grip (p = 0.099).Conclusions: LDRT achieved significant pain relief at rest and during activity and a corresponding objective improvement in handgrip strength in patients with epicondylitis. Pain relief at rest, during activity and improvement in walking time were demonstrated in patients with plantar fasciitis. LDRT achieved pain relief during activity, and handgrip strength was improved in patients with finger osteoarthritis. No significant effect was seen on quality of life measures for these conditions. The observed benefits were maintained 12 months after LDRT for all 3 indications and we recommend this low cost, safe intervention for patients over 40 who have failed prior conservative therapy.

Estimates of Motor Neuron Excitability During Postural Sways in Lower Leg Muscles

Motor system investigations are often performed under isometric conditions, but real‐world motor behaviors are seldom isometric. During tasks where isometric force or torque measurements are not feasible (i.e. during unconstrainedconditions), EMG is often used as a surrogate of the level of muscle activity. However, the linear relationship between EMG and force generation breaks down during non‐isometric contractions. It is not clear how this affects investigators’ ability to discriminate motor units using state‐of‐the‐art high‐density surface EMG arrays. Additionally, the paired motor unit analysis technique, which generates an estimate of the intrinsic excitability of a ‘test’ motor unit by determining discharge rate hysteresis (ΔF), has not been evaluated in unconstrained conditions. Consequently, we asked if 1) visual feedback provided by the subject’s own EMG activity allow for subjects to adequately perform triangular ramp contractions in constrained conditions and 2) if the EMG visual feedback is provided in unconstrained conditions, are ΔF values in subjects similar to those in the constrained condition? We hypothesized that during voluntary isometric ramp contractions, ΔF will be similar regardless of the feedback source. We further hypothesized that standing postural adjustments using EMG feedback in unconstrained conditions will produce similar ΔF values to those calculated during the isometric ramps. We expected that although the mean values across conditions will be similar, the inter‐subject coefficient of variation of ΔF will be greater in the less constrained condition. Accordingly, surface EMG using high‐density array electrodes was collected from five subjects under three conditions: 1) seated in a dynamometer in the isometric mode with torque feedback, 2) in the isometric dynamometer with filtered EMG feedback, and 3) during postural adjustments while standing freely with EMG feedback. In agreement with our hypothesis, we found that ΔF values across all three conditions were similar. In the constrained conditions with either torque or EMG feedback ΔF was 3.10 ± 0.70 imp/s and 3.40 ± 0.75 imp/s, respectively; during the unconstrained case with EMG feedback, ΔF was 3.08 ± 0.73 imp/s (all n = 15, mean ± SE). Contrary to our expectations, the coefficient of variation was not greater in the unconstrained standing condition. These results demonstrate that real‐time EMG feedback is sufficiently similar to torque feedback during both isometric and near‐isometric, unconstrained contractions, suggesting that detailed investigations of motor unit activity may be expanded to more functional movements and used relatively easily in more clinical settings.

Effect of Exergaming on Muscle Strength, Pain, and Functionality of Shoulders in Cancer Patients.

Objective: To compare the strength of the middle deltoid muscle by means of dynamometry and the Shoulder Pain and Disability Index (SPADI) in participants in treatment for cancer after the practice of an exergaming protocol. Materials and Methods: We conducted a randomized controlled clinical trial. Thirty-eight voluntary participants were divided into two groups: cancer group (n = 19; age = 61.46 ± 8.79 years; body mass index [BMI] = 28.36 ± 4.94 kg/m3) and control group (n = 19; age = 57.62 ± 7.57 years; BMI = 28.06 ± 3.74 kg/m3), and they participated in the study. All participants performed an exergame protocol by using Xbox 360 Kinect® (Microsoft, Redmond) with the game Your Shape Fitness Evolved 2012 two to three times per week for 20 sessions. They were evaluated through the isometric dynamometer in the middle deltoid muscle and the SPADI at three moments: preintervention (EV1), after 10 sessions (EV2), and after 20 sessions (EV3). Results: The cancer group scored higher on both the disability index, in all three evaluations, and the pain index, in EV2 and EV3, when compared with the control group. There was a significant reduction in the disability score in EV2 and EV3 when compared with EV1 in the cancer group, whereas pain was lower in EV2 and EV3 when compared with EV1 in the control group. There were no significant interevaluation or intergroup differences in the maximal isometric voluntary contraction of the deltoid muscle of both upper limbs. Conclusion: At the end of the exergaming, protocol reduced the disability of the shoulder joint of the cancer group and decreased the differences between the groups for disability and pain scores, without changing isometric force.

Muscle fatigability in patients with type 2 diabetes: relation with long-term complications.

It is unclear whether long-term complications play a role in muscle fatigue characteristic of patients with type 2 diabetes mellitus (T2DM). The purpose of this study was to investigate the association between muscle fatigability and microvascular and macrovascular complications in patients with T2DM. One-hundred forty-six patients with T2DM (80 males, 66 females, aged 66.9 ± 7.9 years) were recruited. Maximal voluntary contraction (MCV) and endurance time (ET, 50% of the MVC) were assessed at the knee extensor muscles with an isometric dynamometer. Univariate and multivariate correlations of ET values with diabetic complications, a wide range of surrogate measures of these sequelae, and cardiovascular risk factors were examined. A higher muscle fatigability was detected in patients with diabetic peripheral neuropathy (DPN, ET: -32.4%), cardiovascular disease (CVD, ET: -32.1%), retinopathy (ET: -35.8%), and nephropathy (ET: -30.4%). At univariate analysis, muscle fatigability was associated with age, physical activity level, diabetes duration, HbA1c , systolic blood pressure, albuminuria, eGFR, and several parameters of nervous and vascular function. Multivariate analysis showed that, after adjusting for covariates, ET was independently associated with sensory nerve conduction velocity, vibration perception threshold at malleolus, and ankle-brachial index. In addition, ET values were independently associated with the presence of DPN, CVD, and retinopathy. In T2DM, muscle fatigability is associated with presence of DPN, CVD, and retinopathy. Such defect appears to be mediated predominantly by sensory nerve and peripheral vascular dysfunction.

Effects of photobiomodulation on muscle strength in post-menopausal women submitted to a resistance training program.

The aim of this study was to compare the effects of resistance training of low volume and high intensity with or without photobiomodulation (PBM) on muscle strength and functional performance in post-menopausal women. Thirty-four post-menopausal women were randomized into resistance training (RTG, n = 17) or resistance training plus PBM (PBMG, n = 17). Individuals from both groups received the same RT protocol consisting of leg-press 45°, front lat pulldown, leg curl, chest press, and squat performed in two sets of 10 repetitions with a workload of 75% of one repetition maximum (1RM), twice per week, during 8weeks. PBMG individuals also received, prior to the exercise session, PBM through a cluster containing 7 visible diodes (630nm) and 7 infrared diodes (850nm) with power of 100mW each and energy of 4J per diode, applied to the quadriceps femoris muscle; individuals from RTG received placebo PBM prior to the sessions, applied with the same device switched off. Muscle strength (1RM; isometric dynamometer), functional performance (Time Up and Go; Berg Balance Scale; 6-min walk test), and quality of life (World Health Organization Quality of Life-Bref) were performed before and after 8weeks. Both groups increased muscle strength (p < 0.001) for all exercises, without group differences (p = 0.651). Quality of life (p = 0.015) and balance (p = 0.006) increased only in the RTG. The results suggest that PBM were not able for inducing additional benefits to RT to improve muscle strength in post-menopausal women.

Assessment of human motoneuron excitability during functional motor tasks

Detailed investigations of the human motor system are often performed under isometric conditions, although few real‐world activities incorporate isometric contractions. Because of their one‐to‐one relationship with muscle fibers and high safety factor, spinal motoneurons are the only cells in the central nervous system from which firing patterns can be readily accessed in humans. Recent advances in motor unit action potential (MUAP) decomposition techniques using high‐density surface array electrodes allow large numbers of MUAPs to be discriminated relatively non‐invasively. The activity of multiple motor units can allow for the quantification of motoneuron excitability. For example, the paired motor unit analysis technique compares the onset and offset of a high‐threshold motor unit with respect to a low‐threshold unit and quantifies discharge rate hysteresis (ΔF), which is proportional to the intrinsic excitability of the spinal motoneuron. During movements where joint torque measurements are not feasible (i.e. unconstrained by the dynamometer) electromyography (EMG) is often used as a surrogate for the level of muscle activity. However, whether activity level feedback provided by EMG measurements or torque during voluntary contractions elicits similar ΔF values is unknown. We hypothesized that during voluntary isometric ramp contractions, ΔF is similar whether feedback is provided with a torque signal or conditioned EMG. We further hypothesized that standing postural adjustments using EMG feedback in unconstrained conditions will produce similar ΔF values to those calculated during the isometric ramps. We expected that although the mean values across conditions will be similar, the inter‐subject coefficient of variation of ΔF will be greater in the less constrained condition. Accordingly, surface EMG using high‐density array electrodes was collected from five subjects under three conditions: 1) seated in a dynamometer in the isometric mode with activity level feedback provided by the torque (ISO‐TOR), 2) in the isometric dynamometer with feedback provided by EMG (ISO‐EMG), and 3) during postural adjustments while standing freely with feedback provided by EMG (POS‐EMG). In agreement with our hypothesis, we found that ΔF values across all three conditions were similar. In the ISO‐TOR and ISO‐EMG conditions, ΔF was 2.70 ± 0.70 imp/s and 3.40 ± 0.75 imp/s, respectively; during POS‐EMG it was 3.08 ± 0.73 imp/s (all n = 5, mean ± SE). Contrary to our expectations, the coefficient of variation was not greater in the unconstrained standing condition. These results demonstrate that real‐time EMG feedback is sufficiently similar to torque feedback during both isometric and near‐isometric, unconstrained contractions, suggesting that detailed investigations of motor unit activity may be expanded to more functional movements.Support or Funding InformationFunded by R01 NS098509‐01 and T32 HD007418‐27This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Sensitivity of the human ventilatory response to muscle metaboreflex activation during concurrent mild hypercapnia.

What is the central question of this study? What is the relationship between the level of systemic hypercapnia and the magnitude of the additional hyperpnoea produced in response to a standardized level of muscle metaboreflex activation? What is the main finding and its importance? When a standardized activation of the muscle metaboreflex was combined with exposure to increasing levels of hypercapnia, the hyperpnoea this caused increased linearly. The concept of a synergistic interaction between the muscle metaboreflex and the central chemoreflex in humans is supported by this finding. Ventilation increases during muscle metaboreflex activation when postexercise circulatory occlusion (PECO) traps metabolites in resting human muscle, but only in conditions of concurrent systemic hypercapnia. We hypothesize that a linear relationship exists between the level of hypercapnia and the magnitude of the additional hyperpnoea produced in response to a standardized level of muscle metaboreflex activation. Fifteen male subjects performed four trials, in which the end-tidal partial pressure of carbon dioxide ( ) was elevated by 1, 3, 7 or 10mmHg above resting values using a dynamic end-tidal forcing system. In each trial, subjects were seated in an isometric dynamometer designed to measure ankle plantar flexor force. Rest for 2 min in room air was followed by 15min of exposure to one of the four levels ofhypercapnia, at which 5min further rest was followed by 2 min of sustained isometric calf muscle contraction at 50% of predetermined maximal voluntary strength. Immediately before cessation of exercise, a cuff around the upper leg was inflated to a suprasystolic pressure to cause PECO for 3min, before its deflation and a further 5min of rest, concluding exposure to hypercapnia. The PECO consistently elevated mean arterial blood pressure by ∼10mmHg in all trials, indicating similar levels of metaboreflex activation. Increased ventilation during PECO was related to as described by the following linear regression equation: Change in minute ventilation (lmin-1 )=0.85× (mmHg)+0.80 (lmin-1 ). This finding supports our hypothesis and furthers the idea of a synergistic interaction between muscle metaboreflex activation and central chemoreflex stimulation.

Neuromuscular parameters and anaerobic power of U-20 futsal players

The current investigation aimed to find the difference between right and left lower limb strength of quadriceps and hamstring muscles and describe young futsal players’ explosive strength and anaerobic power. The study comprised 12 university male U-20 futsal players (74.5 ± 9.7 kg;173.2 ± 7.2 cm; 18.7 ± 1.2 yrs.). Isometric strength was measured using an isometric dynamometer, lower limb explosive strength was assessed through the Countermovement Jump and anaerobic power was estimated with the Wingate test. Initially, results were displayed through descriptive statistics. Magnitude-based inference with respective Confidence Intervals (CI=90%) and effect size were used to compare inter-lower limb strength. No substantial differences were found between right and left lower limb, to knee extension and flexion. Team’s explosive strength and anaerobic power were 36.7 ± 7 cm and 998.3 ± 125.9 W, respectively. These findings suggest that young futsal players’ performance may be less affected due to inter-lower limb asymmetries.

The Correlation between Power Error and Velocity Error according to the Condition and Frequency of Self-Controlled Feedback during Knee Extension

This study examined the correlation between power error (PE) and velocity error (VE) according to the condition and frequency of self-controlled feedback (SCF) during knee extension. One hundred participants were randomly assigned to 30% SCF, 70% SCF, 30% yoked feedback (YF), 70% YF and control group, respectively. The SCF group was provided with feedback when they requested it, whereas the YF group did not influence the feedback schedule. Participants in the control group were not given any visual feedback during the experiment. The isotonic, isometric, and isokinetic dynamometer (PRIMUS RS, BTE, USA) was used to measure the power and velocity error during knee extension. The collected data was analyzed using a Pearson test and SPSS 21.0. The correlation between PE and VE according to the condition and frequency of feedback on each phase during knee extension was significant. Both PE and VE were significantly higher when the feedback was provided with high frequency, passive, and no feedback. Our study suggests that application of SCF can help to improve the proprioception of the healthy person while reducing errors through low frequency and active feedback.

Is hip strengthening the best treatment option for females with patellofemoral pain? A randomized controlled trial of three different types of exercises

ObjectiveTo evaluate the effect of three types of exercise intervention in patients with patellofemoral pain and to verify the contributions of each intervention to pain control, function, and lower extremity kinematics. MethodsA randomized controlled, single-blinded trial was conducted. Forty women with patellofemoral pain were randomly allocated into four groups: hip exercises, quadriceps exercises, stretching exercises and a control group (no intervention). Pain (using a visual analog scale), function (using the Anterior Knee Pain Scale), hip and quadriceps strength (using a handheld isometric dynamometer) and measuring lower limb kinematics during step up and down activities were evaluated at baseline and 8 weeks post intervention. ResultsAll treatment groups showed significant improvements on pain and Anterior Knee Pain Scale after intervention with no statistically significant differences between groups except when compared to the control group. Only hip and quadriceps groups demonstrated improvements in muscle strength and knee valgus angle during the step activities. ConclusionHip strengthening exercises were not more effective for pain relief and function compared to quadriceps or stretching exercises in females with patellofemoral pain. Only hip and quadriceps groups were able to decrease the incidence of dynamic valgus during step-down activity. This study was approved by Brazilian Clinical Trials Registry registration number: RBR-6tc7mj (http://www.ensaiosclinicos.gov.br/rg/RBR-6tc7mj/).

Comparison of shoulder strength assessment in scaption with an isometric dynamometer and a weighing machine: a pilot study

BackgroundStrength testing is an important aspect of shoulder examination. To date, strength assessment has many limitations. There is no single standard instrument for measuring, and various current devices have problems in reliability, accuracy, and cost. This study compared the results of an innovative and simple method of strength testing (weighing machine) with an existing method (isometric dynamometer).MethodsShoulder strength was tested in 80 individuals, 60 with normal shoulders (group 1) and 20 with shoulder pathology (group 2). Strength was tested in the standard position of 90° of elevation in the scapular plane (scaption) with the elbow extended and forearm pronated while resistance was applied just proximal to the wrist. A weighing machine and an isometric dynamometer were used for strength testing.ResultsThere was a mean difference of 0.26 kg in group 1 (95% confidence interval [CI], 0.16-0.36; P < .0001) and 0.30 kg in group 2 (95% CI, 0,04-0,72; P = .0291) between the weighing machine and the isometric dynamometer. Although statistically significant, these differences were not clinically significant.ConclusionsThis pilot study shows that strength assessment by an innovative and simpler technique with a weighing machine gives similar results as an isometric dynamometer.

Sports Physical Therapy Section Poster Presentations (Abstracts SPO1-SPO166).

These abstracts are presented here as prepared by the authors. The accuracy and content of each abstract remain the responsibility of the authors. In the identification number above each abstract, SPO designates a Sports Physical Therapy Section poster presentation. J Orthop Sports Phys Ther 2018;48(1):A203-A276. doi:10.2519/jospt.2018.48.1.A203.

Prevalence of Glenohumeral Internal Rotation Deficit and its Association with Scapular Dyskinesia and Rotator Cuff Strength Ratio in Collegiate Athletes Playing Overhead Sports

Introduction: Glenohumeral Internal Rotation Deficit (GIRD) indicates a 15° or greater loss of internal rotation of the throwing shoulder compared with the non-dominant shoulder.Aim: To estimate the prevalence of GIRD in collegiate overhead sports player and determine whether GIRD is associated with scapular dyskinesia and rotator cuff strength ratio. Materials and Methods: The present study was a Cross-sectional study. A total of 127 collegiate athletes were assessed for passive range of motion, external to internal rotation strength ratio (ER/IR ratio) and scapular dyskinesia for the throwing and non-throwing shoulder. Internal and external rotation of shoulder was measured using an inclinometer with the subject in prone and arm abducted to 90°. Scapular dyskinesia was measured using Lateral Scapula Slide test (LSST) and external to internal rotator strength was measured using a held hand isometric dynamometer. Chi-square test was used to find the association between GIRD and scapular dyskinesia and rotator cuff strength ratio.Results: Prevalence of GIRD (n=37) was found to be 29.1%. GIRD was not found to be associated with Scapular dyskinesia (p=0.237) and ER/IR strength ratio (p=0.411).Conclusion: Prevalence of GIRD in collegiate athletes playing overhead sports was found to be 29.1% and there was no association of GIRD with scapular dyskinesia, rotator cuff strength ratio.

The impact of type 1 diabetes and diabetic polyneuropathy on muscle strength and fatigability.

Although it is widely accepted that diabetic polyneuropathy (DPN) is linked to a marked decline in neuromuscular performance, information on the possible impact of type 1 diabetes (T1D) on muscle strength and fatigue remains unclear. The purpose of this study was to investigate the effects of T1D and DPN on strength and fatigability in knee extensor muscles. Thirty-one T1D patients (T1D), 22 T1D patients with DPN (DPN) and 23 matched healthy control participants (C) were enrolled. Maximal voluntary contraction (MVC) and endurance time at an intensity level of 50% of the MVC were assessed at the knee extensor muscles with an isometric dynamometer. Clinical characteristics of diabetic patients were assessed by considering a wide range of vascular and neurological parameters. DPN group had lower knee extensor muscles strength than T1D (-19%) and the C group (-37.5%). T1D group was 22% weaker when compared to the C group. Lower body muscle fatigability of DPN group was 22 and 45.5% higher than T1D and C group, respectively. T1D group possessed a higher fatigability (29.4%) compared to C group. A correlation was found between motor and sensory nerve conduction velocity and muscle strength and fatigability. Patients with T1D are characterised by both a higher fatigability and a lower muscle strength, which are aggravated by DPN. Our data suggest that factors other than nervous damage play a role in the pathogenesis of such defect.

Alterations in strength of the shoulder rotators in young elite swimmers

Abstract Introduction: Shoulder muscle strength imbalance is considered a risk factor for shoulder injuries in athletes, especially in sports involving arm movements above the head. Objective: To assess the strength of the external rotators (ER) and internal rotators (IR) of the shoulder in elite swimmers, to determine possible differences between the dominant and non-dominant limbs, and to calculate the shoulder IR/ER ratio. Methods: Fifteen athletes participated in the study from age 20 ± 2 years, mass of 76 ± 4 kg, stature of 1.83 ± 4 cm, and BMI of 22 ± 1 kg/m2. Duration of practice of 10.74 ± 4.03 years; training frequency 5.95 ± 0.22 days/week, 2.07 ± 0.41 hours/day; and weekly number of meters swum 34.905. An isometric dynamometer (Globus Ergo System®, Codognè, Italy) was used to assess ER and IR strength. Data were analyzed using descriptive statistics (mean and standard deviation), paired-sample t-test, Pearson’s correlation coefficient and the Statistical Package for Social Sciences software (SPSS), version 16.0. Results: IR and ER strength was lower in the left than in the right shoulder of the swimmers (p &lt; 0.05). Additionally, ER strength ratio was higher than IR strength ratio (p &lt; 0.05). Conclusion: The results showed that the swimmers had an alteration of the shoulder ER/IR ratio, especially in the dominant limb.

Evaluation of bilateral force deficit in shoulder flexion using a handheld dynamometer in healthy subjects.

[Purpose] This study aimed to develop a simple, inexpensive, and accurate method for measuring the strength of shoulder flexion (Experiment 1) and evaluate the bilateral force deficit in shoulder flexion (Experiment 2) in healthy subjects. [Subjects and Methods] In Experiment 1, maximal voluntary contractions (MVCs) in isometric shoulder flexion were measured on both sides using an isometric dynamometer (ID) and a hand-grip dynamometer (HGD), as an alternative dynamometer, in six subjects. In Experiment 2, bilateral force deficit was evaluated using HGD in 21 subjects who performed unilateral and bilateral MVCs in isometric flexions of the shoulder. The peak value of electromyography (PVE) in the lateral head of the biceps brachii and anterior deltoid was measured during MVCs. [Results] In Experiment 1, ID and HGD showed almost similar coefficients of variation. A strong positive correlation was found between the values obtained using the two methods. In Experiment 2, the bilateral force deficit in shoulder flexion associated with a reduced PVE (‒10.9%) was found in 85.7% of subjects. [Conclusion] The reproducibility of measurements was similar between ID and HGD. HGD could evaluate the bilateral force deficit in shoulder flexion and is a practical tool for measuring shoulder strength.

No Critical Peripheral Fatigue Threshold during Intermittent Isometric Time to Task Failure Test with the Knee Extensors.

It has been proposed that group III and IV muscle afferents provide inhibitory feedback from locomotor muscles to the central nervous system, setting an absolute threshold for the development of peripheral fatigue during exercise. The aim of this study was to test the validity of this theory. Thus, we asked whether the level of developed peripheral fatigue would differ when two consecutive exercise trials were completed to task failure. Ten trained sport students performed two exercise trials to task failure on an isometric dynamometer, allowing peripheral fatigue to be assessed 2 s after maximal voluntary contraction (MVC) post task failure. The trials, separated by 8 min, consisted of repeated sets of 10 × 5-s isometric knee extension followed by 5-s rest between contractions. In each set, the first nine contractions were performed at a target force at 60% of the pre-exercise MVC, while the 10th contraction was a MVC. MVC and evoked force responses to supramaximal electrical femoral nerve stimulation on relaxed muscles were assessed during the trials and at task failure. Stimulations at task failure consisted of single stimulus (SS), paired stimuli at 10 Hz (PS10), paired stimuli at 100 Hz (PS100), and 50 stimuli at 100 Hz (tetanus). Time to task failure for the first trial (12.84 ± 5.60 min) was longer (P < 0.001) than for the second (5.74 ± 1.77 min). MVC force was significantly lower at task failure for both trials compared with the pre-exercise values (both P < 0.001), but there were no differences in MVC at task failure in the first and second trials (P = 1.00). However, evoked peak force for SS, PS100, and tetanus were all reduced more at task failure in the second compared to the first trial (P = 0.014 for SS, P < 0.001 for PS100 and tetanus). These results demonstrate that subjects do not terminate exercise at task failure because they have reached a critical threshold in peripheral fatigue. The present data therefore question the existence of a critical peripheral fatigue threshold during intermittent isometric exercise to task failure with the knee extensors.

Validation of upper limb motor assessment tasks using a rehabilitation robot in healthy children

To validate, establish norms and evaluate the reproducibility of upper limb motor assessment tasks using REAplan in healthy children. REAplan is a rehabilitation robotic device allowing upper limb mobilization in the horizontal plane. Forty-nine healthy children between six and twelve years participated in this study. Each child was assessed clinically and with REAplan, and twelve children were assessed twice. Elbow flexor and extensor muscles force were assessed with an isometric dynamometer Microfet II. REAplan allows assessing muscle force by an isometric and isokinetic evaluation (18 cm/s) in three directions. Finally, the kinematic was assessed by a pointing task to 30 targets evenly distribute in the REAplan working space. The isometric force assessed with REAplan is highly correlated with the one assessed with the dynamometer for flexor muscles ( r = 0.8 and P < 0.001) and is moderate for extensor muscles ( r = 0.61 and P < 0.001). The isokinetic force assessment showed that children developed a higher force when their upper limb was mobilized in a trajectory in front of them compared to trajectories angled 45°C in diagonal. This is true for elbow flexor and extensor muscles ( P < 0.001). For the kinematic assessment, straightness, averaged speed and speed metric improve when the distance to reach a target is longer ( P < 0.05). Finally, all assessment tasks showed a very good reproducibility (ICC > 0.82 and P < 0.001) and this study allowed to establish norms for each age group. This study allowed validating, establishing norms and evaluating the reproducibility of motor performance assessment tasks in healthy children using REAplan. This method can now be used to assess brain-damaged children. Some of these results will be illustrated during the congress.