Maximal Handgrip Force Research Articles

Population-specific equations of age-related maximum handgrip force: a comprehensive review.

The measurement of handgrip force responses is important in many aspects, for example: to complement neurological assessments, to investigate the contribution of muscle mass in predicting functional outcomes, in setting realistic treatment goals, evaluating rehabilitation strategies. Normative data about handgrip force can assist the therapist in interpreting a patient's results compared with healthy individuals of the same age and gender and can serve as key decision criteria. In this context, establishing normative values of handgrip strength is crucial. Hence, the aim of the this study is to develop a tool that could be used both in rehabilitation and in the prevention of work-related musculoskeletal disorders. This tool takes the form of population-specific predictive equations, which express maximum handgrip force as a function of age. In order to collect data from studies measuring maximum handgrip force, three databases were searched. The search yielded 5,058 articles. Upon the removal of duplicates, the screening of abstracts and the full-text review of potentially relevant articles, 143 publications which focussed on experimental studies on various age groups were considered as fulfilling the eligibility criteria. A comprehensive literature review produced 1,276 mean values of maximum handgrip force. A meta-analysis resulted in gender- and world region-specific (general population, USA, Europe and Asia) equations expressing maximum force as a function of age. The equations showed quantitative differences and trends in maximum handgrip force among age, gender and national groups. They also showed that values of maximum handgrip force are about 40% higher for males than for females and that age-induced decrease in force differs between males and females, with a proved 35% difference between the ages of 35 and 75. The difference was lowest for the 60-64 year olds and highest for the 18-25 year-olds. The equations also showed that differences due to region are smaller than those due to age or gender. The equations that were developed for this study can be beneficial in setting population-specific thresholds for rehabilitation programmes and workstation exposure. They can also contribute to the modification of commonly used methods for assessing musculoskeletal load and work-related risk of developing musculoskeletal disorders by scaling their limit values.

Effect of teeth clenching on handgrip force in adult men: role of periodontal mechanoreceptors.

Voluntary teeth clenching is shown to increase the strength of muscle reflexes contributing to the improvement of postural stability. However, the interaction between the handgrip strength and teeth clenching is not yet understood. In this study, we aimed to evaluate the change in handgrip force in response to voluntary teeth clenching, and its relation to the peripheral receptors that play a central role in the control of mastication. Thirty-six healthy men were divided into two groups: aged 50-59years, no dental prosthesis, and 53-62years with total dental prosthesis. Each individual was given handgrip and teeth clenching instructions for five experiments: only handgrip, teeth clenching followed by handgrip without teeth clenching, teeth clenching followed by handgrip with teeth clenching, and the repetition of the last two instructions while wearing mouth guards. Our findings showed that maximum handgrip force decreased and the resistance to fatigue increased in complete edentulous individuals using appropriate prostheses. Also, the significantly lower maximum handgrip force and higher resistance to fatigue values of the participants with dental prosthesis using a mouth guard while teeth clenching, revealed the central roles of periodontal mechanoreceptors. Decreases in masticatory sensory information processes influence handgrip force values which is the most important indicator of motor function. The lack of periodontal mechanoreceptors associated with dental prosthesis usage may lead to a loss in muscle strength.

Handgrip Strength and its Association with Anthropometric Measurements at Different Anatomical Positions of Arm among Young Individuals

Many studies have studied the relationships between handgrip strength and different Anthropometric variables. However, the hand anatomical position when measuring the handgrip strength was not clear in many studies. This study aims to investigate the relationship between the anthropometric measurements and the handgrip strength at different anatomical positions of the arm among young individuals. 59 young males and 41 females were asked to squeeze the hand dynamometer to their maximum capacity. The maximum handgrip force was recorded for 7 different arm anatomical positions. Using SPSS, an Independent student's t-test was used to compare male and female groups. Pearson’s correlation coefficients were used to determine the correlations between handgrip strength and the anthropometric measurements, weight, and BMI at different arm anatomical positions. Furthermore, the dominance weight was computed to determine the most important predictors of grip strength. Significant correlation between handgrip strength and height and weight at all positions and with hand length for all positions except when the arm was abducted and extended 180 ͦ at the shoulder joint and 180 ͦ at the elbow joint. Arm length, forearm length and handbreadth were also correlated to handgrip strength at three positions, when the arm was adducted with 90 ͦ forward at the elbow joint, when the Arm was abducted with 90 ͦ at the shoulder joint and 180 ͦ at the elbow, and when the arm was abducted with 90 ͦ at the shoulder joint and 90 ͦ at the elbow joint with the forearm perpendicular to the frontal plane. However, these correlations were different when males and females were considered separately. Furthermore, the results showed that the height followed by hand length had the highest prediction power of handgrip strength among young adults. The current results showed the importance of considering the different anatomical positions of the arm when studying the relationship between anthropometric measurements and hand grip strength.

Association between masseter muscle volume, nutritional status, and cognitive status in older people

ObjectivesClinical evidence has suggested that oral function is associated with cognitive, physical, and nutritional status of older people. A smaller volume of masseter, a crucial muscle for mastication, was associated with frailty. It has remained unknown if smaller masseter is associated with cognitive impairment. The current study investigated the association between masseter muscle volume, nutritional status, and cognitive status in older people. Materials and methodsWe recruited 19 patients with mild cognitive impairment (MCI), 15 patients with Alzheimer's disease (AD), and 28 sex and age-matched non-cognitive impairment (non-CI) older subjects. The number of missing teeth (NMT), masticatory performance (MP), maximal hand-grip force (MGF), and calf circumference (CC) were assessed. The masseter volume index (MVI) was calculated based on the masseter volume measured using magnetic resonance imaging. ResultsThe MVI was significantly lower in the AD group, compared to the MCI as well as the non-CI group. Multiple regression analyses revealed that the MVI was significantly associated with nutritional status (as indexed by CC) in the analysis of combination of NMT, MP, and the MVI. Moreover, the MVI was a significant predictor of CC only in patients with cognitive impairment (i.e., MCI+AD) but not in the non-CI group. ConclusionsOur findings suggested that in addition to the NMT and MP, masseter volume is a critical oral factor associated with cognitive impairment. Clinical relevance. Reduction of MVI should be carefully monitored for patients with dementia and frailty, to whom a lower MVI may indicate worse nutrient intake.

Neuromuscular Fatigue in Unimanual Handgrip Does Not Completely Affect Simultaneous Bimanual Handgrip

Simultaneous bimanual movements are not merely the sum of two unimanual movements. Here, we considered the unimanual/bimanual motor system as comprising three components: unimanual-specific, bimanual-specific, and overlapping (mobilized during both unimanual and bimanual movements). If the force-generating system controlling the same limb differs between unimanual and bimanual movements, unimanual exercise would be expected to fatigue the unimanual-specific and overlapping parts in the force-generating system but not the bimanual-specific part. Therefore, we predicted that the decrease in bimanual force generation induced by unimanual neuromuscular fatigue would be smaller than the decrease in unimanual force generation. Sixteen healthy right-handed adults performed unimanual and bimanual maximal handgrip measurements before and after a submaximal fatiguing handgrip task. In the fatigue task, participants were instructed to maintain unimanual handgrip force at 50% of their maximal handgrip force until the time to task failure. Each participant performed this task in a left-hand fatigue (LF) condition and a right-hand fatigue (RF) condition, in a random order. Although the degree of neuromuscular fatigue was comparable in both conditions, as expected, the decrease in bimanual right handgrip force was significantly smaller than those during unimanual right performance in the RF condition, but not in the LF condition. These results indicate that for the right-hand, neuromuscular fatigue in unimanual handgrip does not completely affect simultaneous bimanual handgrip. Regarding the underlying mechanisms, we propose that although neuromuscular fatigue caused by unimanual handgrip reduces the motor output of unimanual-specific and overlapping parts in the force-generating system, when simultaneous bimanual handgrip is performed, the overlapping part (which is partially fatigued) and the bimanual-specific part (which is not yet fatigued) generate motor output, thus decreasing the force reduction.

Bilateral Deficits during Maximal Grip Force Production in Late Postmenopausal Women

The purpose of this study was to investigate bilateral deficit patterns during maximal hand-grip force production in late postmenopausal women. Twenty late postmenopausal and 20 young premenopausal women performed maximal isometric grip force production tasks with dominant and nondominant hands and both hands, respectively. For late postmenopausal women, pulse wave analysis was used for identifying a potential relationship between maximal hand-grip strength and risk factors of cardiovascular disease. The findings showed that late postmenopausal women produced significantly decreased maximal hand-grip strength in dominant and nondominant and bilateral hand conditions compared to those of premenopausal women. Bilateral deficit patterns appeared in late postmenopausal women. For late postmenopausal women, decreased dominant and bilateral hand-grip forces were significantly related to greater bilateral deficit patterns. Further, less maximal hand-grip strength in unilateral and bilateral hand conditions correlated with greater central pulse pressure. These findings suggested that age-related impairments in muscle strength and estrogen deficiency may interfere with conducting successful activities of bilateral movements. Further, assessing maximal dominant hand-grip strength may predict bilateral deficit patterns and risk of cardiovascular disease in late postmenopausal women.

Effects of ergonomic clip-on handles on upper-body vibration transmissibility and muscular activity during pedalling with vibrations

Mountain bikers often report impaired finger sensitivity caused by mechanical vibrations and misalignment between the wrist and the forearm when using traditional (cylindrical) handles. The aim of this study was to evaluate the acute effects of ergonomic clip-on handles that allowed the hand to rest on the medial carpal bone, on muscular activity, vibration transmissibility between the cycle ergometer and body segments, and handgrip strength. Sixteen cyclists performed two pedalling exercises at ~200 W lasting 20 minutes on a cycle ergometer that delivered vibrations under the fork (vertical amplitude: 4-25 mm; frequency: 4-17 Hz) whilst using cylindrical handles and ergonomic clip-on handles with a randomized order. Compared to cylindrical handles, ergonomic clip-on handles decreased significantly vibration transmissibility to the extensor digitorum, triceps brachii and flexor carpi radialis muscles by 10, 10 and 7%, respectively. The surface electromyography activity of the flexor carpi radialis decreased by 45%, while that of the triceps brachii increased by 12% (both significantly). Unlike the cylindrical handles, the ergonomic clip-on handles did not involve a significant decrease in the maximal handgrip force after the pedalling exercise. The ergonomic clip-o handles may prevent symptoms of hand-arm vibration syndrome in mountain bikers and could preserve their ability to effectively manoeuvre and brake the bike.

Ipsilateral and contralateral responses following unimanual fatigue with and without illusionary mirror visual feedback.

Illusionary mirror visual feedback alters interhemispheric communication and influences cross-limb interactions. Combining forceful unimanual contractions with the mirror illusion is a convenient way to provoke robust alterations within ipsilateral motor networks. It is unknown, however, if the mirror illusion affects cross-limb fatigability. We examine this concept by comparing the ipsilateral and contralateral handgrip force and electromyographic (EMG) responses following unimanual fatigue with and without illusionary mirror visual feedback. Participants underwent three experimental sessions (mirror, no-mirror, and control), performing a unimanual fatigue protocol with and without illusionary mirror visual feedback. Maximal handgrip force and EMG activity were measured before and after each session for both hands during maximal unimanual and bimanual contractions. The associated EMG activity from the inactive forearm during unimanual contraction was also examined. The novel findings demonstrate greater relative fatigability during bimanual versus unimanual contraction following unimanual fatigue (-31.8% vs. -23.4%, P < 0.01) and the mirror illusion attenuates this difference (-30.3% vs. -26.3%, P = 0.169). The results show no evidence for a cross-over effect of fatigue with (+0.62%, -2.72%) or without (+0.26%, -2.49%) the mirror illusion during unimanual or bimanual contraction. The mirror illusion resulted in significantly lower levels of associated EMG activity in the contralateral forearm. There were no sex differences for any of the measures of fatigability. These results demonstrate that the mirror illusion influences contraction-dependent fatigue during maximal handgrip contractions. Alterations in facilitatory and inhibitory transcallosal drive likely explain these findings.NEW & NOTEWORTHY Illusionary mirror visual feedback is a promising clinical tool for motor rehabilitation, yet many features of its influence on motor output are unknown. We show that maximal bimanual force output is compromised to a greater extent than unimanual force output following unimanual fatigue, yet illusionary mirror visual feedback attenuates this difference. The mirror illusion also reduces the unintended EMG activity of the inactive, contralateral forearm during unimanual contraction.

Impact of an individual personalised rehabilitation program on mobility performance in older-old people.

Studies have shown benefits of exercise interventions on preferred and fast gait speed in healthy older adults, but the impact of a personalised rehabilitation program targeting a large cohort of non-disabled older-old adults has rarely been examined. The purpose was to determine whether personalised intervention-related improvements in gait and mobility performance in older-old adults were dependent on cognitive status and/or history of falls. Based on a pre-post design, 483 older-old persons (mean age: 83.3 ± 5.1years) were followed during a personalised rehabilitation program over a period of 7 weeks, with twice-weekly sessions (45min each). Gait speed in four conditions (preferred, fast, and under two dual-task conditions), static postural sway, Timed Up and Go test, Five Times Sit to Stand test, the ability to rise from the floor, and handgrip strength test were assessed. Using a pre-post analysis of covariance, a significant increase in preferred gait speed (+ 20.1%), fast gait speed (+ 15.8%), and dual-task speed while counting (+ 13.4%) was observed after the rehabilitation, regardless of the baseline cognitive status and fall history. Similar improvements in TUG and maximal handgrip force were observed, with a significant reduction of performance time (-19.5%) or an increase of handgrip strength (+ 6.2%). Results suggest the effectiveness of personalised intervention to improve a battery of physical performance measures in older-old adults, even for the frailest participants. Implementing a personalised intervention for targeting the high-risk older-old adults in priority is critical regarding the clinically meaningful change in gait speed.

Comparison of Three Physical-Cognitive Training Programs in Healthy Older Adults: A Study Protocol for a Monocentric Randomized Trial.

(1) Combining aerobic, coordination and cognitive training allows for more improved physical and cognitive performance than when performed separately. A Nordic walking (NW) and two cognitive-motor circuit training programs (CT-c and CT-fit) are compared. CT-c and CT-fit stimulate cognition differently: CT-c, is through conventional complex coordination training performed in single and dual-task conditions; CT-fit, incorporates it into complex goal-directed actions, implemented by fitness gaming technology (2) The aim is to determine whether CT-fit brings additional benefits to cognition compared to more traditional training. (3) Forty-five healthy independent living community dwellers participants (65–80 years) will be included after a general medical examination. The main exclusion criteria are signs of cognitive impairments (Mini–Mental State Examination < 26/30) and physical impairments. Pre and post-tests will be performed to assess: cognitive functions (Montreal Cognitive Assessment; Trail Making Test; Stroop task, working memory test, Rey Complex Figure copy task, Oral Trail Making Test, and dual-task); motor fitness (Bipedal and unipedal balance test, gait assessments, Time Up and Go, chair sit and reach test and four-square stepping test); and physical fitness (10 m incremental shuttle walking test, maximal handgrip force, Timed-Stands test). (4) Incorporating cognitive demands into complex, goal-directed actions using fitness gaming technology should be the best solution to optimize training benefits.

Sustained Isometric Wrist Flexion and Extension Maximal Voluntary Contractions on Corticospinal Excitability to Forearm Muscles during Low-Intensity Hand-Gripping.

The wrist extensors demonstrate an earlier fatigue onset than the wrist flexors. However, it is currently unclear whether fatigue induces unique changes in muscle activity or corticospinal excitability between these muscle groups. The purpose of this study was to examine how sustained isometric wrist extension/flexion maximal voluntary contractions (MVCs) influence muscle activity and corticospinal excitability of the forearm. Corticospinal excitability to three wrist flexors and three wrist extensors were measured using motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation. Responses were elicited while participants exerted 10% of their maximal handgrip force, before and after a sustained wrist flexion or extension MVC (performed on separate sessions). Post-fatigue measures were collected up to 10-min post-fatigue. Immediately post-fatigue, extensor muscle activity was significantly greater following the wrist flexion fatigue session, although corticospinal excitability (normalized to muscle activity) was greater on the wrist extension day. Responses were largely unchanged in the wrist flexors. However, for the flexor carpi ulnaris, normalized MEP amplitudes were significantly larger following wrist extension fatigue. These findings demonstrate that sustained isometric flexion/extension MVCs result in a complex reorganization of forearm muscle recruitment strategies during hand-gripping. Based on these findings, previously observed corticospinal behaviour following fatigue may not apply when the fatiguing task and measurement task are different.

The ratio of maximal handgrip force and maximal cycloergometry power as a diagnostic tool to screen for metabolic myopathies

Metabolic myopathies comprise a diverse group of inborn errors of intermediary metabolism affecting skeletal muscle, and often present clinically as an inability to perform normal exercise. Our aim was to use the maximal mechanical performances achieved during two functional tests, isometric handgrip test and cycloergometer, to identify metabolic myopathies among patients consulting for exercise-induced myalgia. Eighty-three patients with exercise-induced myalgia and intolerance were evaluated, with twenty-three of them having a metabolic myopathy (McArdle, n = 9; complete myoadenylate deaminase deficiency, n = 10; respiratory chain deficiency, n = 4) and sixty patients with non-metabolic myalgia. In all patients, maximal power (MP) was determined during a progressive exercise test on a cycloergometer and maximal voluntary contraction force (MVC) was assessed using a handgrip dynamometer. The ratio between percent-predicted values for MVC and MP was calculated for each subject (MVC%pred:MP%pred ratio). In patients with metabolic myopathy, the MVC%pred:MP%pred ratio was significantly higher compared to non-metabolic myalgia (1.54 ± 0.62 vs. 0.92 ± 0.25; p < 0.0001). ROC analysis of MVC%pred:MP%pred ratio showed AUC of 0.843 (0.758–0.927, 95% CI) for differentiating metabolic myopathies against non-metabolic myalgia. The optimum cutoff was taken as 1.30 (se = 69.6%, sp = 96.7%), with a corresponding diagnostic odd ratio of 66.3 (12.5–350.7, 95% CI). For a pretest probability of 15% in our tertiary reference center, the posttest probability for metabolic myopathy is 78.6% when MVC%pred:MP%pred ratio is above 1.3. In conclusion, the MVC%pred:MP%pred ratio is appropriate as a screening test to distinguish metabolic myopathies from non-metabolic myalgia.

Maximum handgrip strength as a function of type of work and hand-forearm dimensions

Handgrip strength is a measurement of upper extremity functionality and an indicator of overall physical ability. The objective of this study was to compare maximum handgrip strength (MGS) between manual workers and office employees and to investigate if the expected difference is related to the anthropometric dimensions of the workers' hands and forearms. This was a cross-sectional study with a sample of 1740 male workers (905 light manual workers; and 835 office employees), aged 20-64 years. Maximum voluntary contractions were obtained using a JAMAR dynamometer according to the methodology proposed by the American Society of Hand Therapy (ASHT). The highest value obtained from three trials was considered as the MGS for each side. Six anthropometric dimensions (i.e., hand length, palm length, forearm length, hand breadth, wrist circumference and forearm circumference) were measured by digital caliper and tape measure. Maximum handgrip strength of light manual workers (52.7±8.5 kg) was significantly higher than that of office employees (47.3±8.4 kg) (p < 0.001). Maximum handgrip strength was positively correlated with Hand breadth (r = 0.781 for light manual workers and r = 0.766 for office employees; p < 0.001) and Forearm circumference (r = 0.741 for light manual workers and r = 0.752 for office employees; p < 0.001); the only dimensions which were significantly different between the two studied job groups. The results of this study revealed that light manual workers are approximately 12.4% stronger than office employees in terms of maximum handgrip force. It is therefore imperative to consider the observed differences in clinical, workstations, and hand tool designs in order to increase efficiency and comfort at work.

Differences in Net Information Flow and Dynamic Connectivity Metrics Between Physically Active and Inactive Subjects Measured by Functional Near-Infrared Spectroscopy (fNIRS) During a Fatiguing Handgrip Task.

Twenty-three young adults (4 Females, 25.13 ± 3.72 years) performed an intermittent maximal handgrip force task using their dominant hand for 20 min (3.5 s squeeze/6.5 s release, 120 blocks) with concurrent cortical activity imaging by functional Near-Infrared Spectroscopy (fNRIS; OMM-3000, Shimadzu Corp., 111 channels). Subjects were grouped as physically active (n = 10) or inactive (n = 12) based on a questionnaire (active-exercise at least four times a week, inactive- exercise less than two times a week). We explored how motor task fatigue affected the vasomotion-induced oscillations in ΔHbO as measured by fNIRS at each hemodynamic frequency band: endothelial component (0.003–0.02 Hz) associated to microvascular activity, neurogenic component (0.02–0.04 Hz) related to intrinsic neuronal activity, and myogenic component (0.04–0.15 Hz) linked to activity of smooth muscles of arterioles. To help understand how these three neurovascular regulatory mechanisms relate to handgrip task performance we quantified several dynamic fNIRS metrics, including directional phase transfer entropy (dPTE), a computationally efficient and data-driven method used as a marker of information flow between cortical regions, and directional connectivity (DC), a means to compute directionality of information flow between two cortical regions. The relationship between static functional connectivity (SFC) and functional connectivity variability (FCV) was also explored to understand their mutual dependence for each frequency band in the context of handgrip performance as fatigued increased. Our findings ultimately showed differences between subject groups across all fNIRS metrics and hemodynamic frequency bands. These findings imply that physical activity modulates neurovascular control mechanisms at the endogenic, neurogenic, and myogenic frequency bands resulting in delayed fatigue onset and enhanced performance. The dynamic cortical network metrics quantified in this work for young, healthy subjects provides baseline measurements to guide future work on older individuals and persons with impaired cardiovascular health.

Impact of age, sex and heart rate variability on the acute cardiovascular response to isometric handgrip exercise.

Isometric handgrip exercise (IHG) triggers acute increases in cardiac output to meet the metabolic demands of the active skeletal muscle. An abnormal cardiovascular response to IHG might reflect early stages of cardiovascular disease. In a large community-based cohort, we comprehensively assessed the clinical correlates of acute cardiovascular changes during IHG. In total, 333 randomly recruited subjects (mean age, 53 ± 13 years, 45% women) underwent simultaneous echocardiography and finger applanation tonometry at rest and during 3 min of IHG at 40% maximal handgrip force. We calculated time-domain measures of short-term heart rate variability (HRV) from finger pulse intervals. We assessed the adjusted associations of changes in blood pressure (BP) and echocardiographic indexes with clinical characteristics and HRV measures. During IHG, men presented a stronger absolute increase in heart rate, diastolic BP, left ventricular (LV) volumes and cardiac output than women, even after adjustment for covariables. In adjusted continuous and categorical analyses, age correlated positively with the increase in systolic BP and pulse pressure, but negatively with the increase in LV stroke volume and cardiac output during exercise. After full adjustment, a greater increase in systolic and diastolic BP during exercise was associated with lower absolute real variability (P ≤ 0.026) and root mean square of successive differences (P ≤ 0.032) in pulse intervals at rest. In a general population sample, women presented a weaker cardiovascular response to IHG than men. Older age was associated with greater rise in BP pulsatility and diminished cardiac reserve. Low HRV at rest predicted a higher BP increase during isometric exercise.

A MODEL OF THE CHARACTERISTICS OF HAND GRIP MUSCLE FORCE BASED ON ELITE FEMALE HANDBALL PLAYERS OF VARIOUS AGES

The aim of the study was to establish trends in the development of contractile characteristics of hand grip in terms of the maximum and relative force, as a test for upper body strength. The sample consisted of 207 female handball players organised into age categories; 52 senior (age = 24.5 ± 3.3), 51 junior (U18, age = 17.4 ± 0.7), 45 youth (U16, age = 15.5 ± 0.9), and 49 young players (U14, age = 13.4 ± 0.5). There is a statistically significant difference of absolute and relative maximal hand grip muscle force between all age groups (Wilks’s lambda = 0.416, p = 0.000). The results showed that the values of the maximum right hand grip force ranged from 430.7 N to 297.7 N and from 405.5 N to 268.6 N for left hand for senior to young players, respectively (Table 1). Also, according to the results it was determined that trend of change in observed contractile characteristics according to the age groups are 44.7N and 43.6N for absolute, and 0.462 and 0.463 N·BW-1 for relative values of maximal hand grip force for the right and the left hand, respectively.

Reliability, Sensitivity, and Minimal Detectable Change of a New Specific Climbing Test for Assessing Asymmetry in Reach Technique.

Čular, D, Dhahbi, W, Kolak, I, Iacono, AD, Bešlija, T, Laffaye, G, and Padulo, J. Reliability, sensitivity, and minimal detectable change of a new specific climbing test for assessing asymmetry in reach technique. J Strength Cond Res 35(2): 527-534, 2021-The aims of this study were to establish intertrial and intersession reliability, sensitivity, and minimal detectable change of a new climbing test specifically for assessing asymmetry in reach technique (TEST). Twenty-four young climbers (16 males and 8 females) participated in this study. The protocol consisted of performing, in counterbalanced random order, 3 tests; TEST, maximum handgrip force, and squat on the bench, in 2 sessions (with 3 trials for each session). TEST performance was expressed as: TEST performance for left hand (TESTL), TEST performance for right hand (TESTR), and absolute symmetry index (ASI). For intertrial and intersession reliability assessment, TESTL and TESTR showed excellent reliability (intraclass correlation coefficients ranged: 0.96-1.00; SEM% ranged: 0.07-1.23; and coefficient of variation-CV%: 1.28-2.53). In addition, SEMs were smaller than the smallest worthwhile change (SWC) values (SWC% = 1.07 and 0.99 for TESTL and TESTR, respectively), and the minimal detectable change (MDC95) for both sides was small (<4.36 cm). An exception was ASI, which showed low absolute reliability and marginal sensitivity (SEM% = 15.13 > SWC% = 8.40 and CV% = 41.98). Pairwise test comparisons revealed no difference between sides. Considering the high reliability and the satisfactory sensitivity, TEST can be used to define individual asymmetry in the performance of the reach technique to the left or the right body side in climbers. However, interpreting data using the ASI index requires caution because it had poor absolute reliability and marginal sensitivity.

Subparalyzing Doses of Rocuronium Reduce Muscular Endurance without Detectable Effect on Single Twitch Height in Awake Subjects.

Purpose To test the hypothesis that a low-dose rocuronium acts mainly by means of reducing muscular endurance rather than by reducing momentary force. Methods In a randomized placebo-controlled double-blinded study, eight healthy volunteers were studied in two sets of experiments. In the first set, the subjects made a sustained maximum effort with the dominant hand for 80 seconds while squeezing an electronic handgrip dynamometer at three minutes after intravenous administration of placebo, 0.04 or 0.08 mg/kg rocuronium. Handgrip force at initiation of testing (maximum handgrip force) and after 60 seconds was evaluated. In the second set, the ulnar nerve of the subjects was electrically stimulated every tenth second for at least 10 and a maximum of 30 minutes following the administration of placebo and 0.08 mg/kg rocuronium. Single twitch height of the adductor pollicis muscle was recorded. Results There was no significant difference in the effect on maximum handgrip force at time 0 between the three different doses of rocuronium. As compared with placebo, handgrip force after 0.08 mg/kg rocuronium was reduced to approximately a third at 60 seconds (214 N (120–278) vs. 69 (30–166); p=0.008), whereas only a slight reduction was seen after 0.04 mg/kg (187 (124–256); p=0.016). Based on these results, the sustained handgrip force after 0.2 mg/kg at 60 seconds was calculated to be 1.27% (95% CI [0.40, 4.03]) of the maximum force of placebo. No effect on single twitch height after 0.08 mg/kg rocuronium at four minutes after drug administration could be detected. Conclusions Subparalyzing doses of rocuronium show a distinct effect on muscular endurance as opposed to momentary force. The findings support the hypothesis that low doses of rocuronium act mainly by reducing muscular endurance, thereby facilitating, for example, tracheal intubation.

Perceived exertion during muscle fatigue as reflected in movement-related cortical potentials: an event-related potential study.

The aim of this study was to explore the mechanism on perceived exertion during muscle fatigue. A total of 15 individuals in the fatigue group and 13 individuals in the nonfatigue group were recruited into this study, performing 200 intermittent handgrip contractions with 30% maximal voluntary contraction. The force, surface electromyography (sEMG), movement-related cortical potentials (MRCPs), and rating perception of effort (RPE) were combined to evaluate the perceived exertion during muscle fatigue. The maximal handgrip force significantly decreased (P<0.01), the root mean square of sEMG over each block significantly increased (P<0.01), and SD of force at plateau increased (P<0.01) during muscle fatigue. The RPE scores reported by the individuals and the motor potential amplitude of MRCPs in the fatigue group significantly increased (P<0.001). However, as for the individuals in the nonfatigue group, the other indexes showed no significant changes except for a little increase in the RPE. The within-subject correlation coefficients showed that there were significant correlations between RPE and motor potential amplitude of MRCPs at the C1 site (r=-0.609, P<0.001) and between RPE and root mean square of sEMG (r=0.541, P<0.001). Our results substantiate that the perceived exertion correlates with the central motor command during movement execution rather than the preparatory process. The perceived exertion not only reflects central fatigue but could also reflect the peripheral local muscle fatigue.

Effect of Acute Effort on Isometric Strength and Body Balance: Trained vs. Untrained Paradigm.

Years of training in competitive sports leads to human body adaptation to a specific type of exercise. In judo bouts, maintaining hand grip on an opponent’s clothes and postural balance is essential for the effective technical and tactical actions. This study compares changes after maximal anaerobic exercise among judo athletes and untrained subjects regarding 1) maximum isometric handgrip strength (HGSmax) and accuracy at the perceived 50% maximum handgrip force (1/2HGSmax) and 2) the balance of 13 judo athletes at national (n = 8) and international (n = 5) competitive levels and 19 untrained university students. The groups did not differ in age, body height, and weight. Body mass index (BMI) and body composition (JAWON) were evaluated. The Wingate Anaerobic Test (WAnT, Monark 875E) measured recommended anaerobic capacity indices. Hand grip strength (Takei dynamometer) and balance (biplate balance platform) were measured before warm-up (T1), before the WAnT test (T2), and after (T3). Parametric or non-parametric tests were performed after verifying the variable distribution assumption. Judoists had higher BMI and fat-free mass index (FFMI) than the students. The athletes also showed higher relative total work and relative peak power and lower levels of lactic acid. The difference in judoists between HGSmax at T1 and HGSmax at T3 was statistically significant. Before warm-up (T1), athletes showed higher strength (more divergent from the calculated ½HGSmax value) compared to students. Substantial fatigue after the WAnT test significantly deteriorated the body stability indices, which were significantly better in judo athletes at all time points. The findings suggest specific body adaptations in judoists, especially for body composition, anaerobic energy system efficiency, and postural balance. These characteristics could be trained for specifically by judo athletes to meet the time-motion and anaerobic demands of contemporary bouts.