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PubMed1990

Effect on histamine responsiveness of reducing airway dimensions by altering posture.

Baseline airway geometry is thought to be an important determinant of the airway response to challenge; this geometry is altered by changing posture. The effect of changes in posture on airway calibre, midtidal lung volume, and the airway response to inhaled histamine was studied in eight healthy subjects (four female; mean (SD) age 29.8 (5.1) years, FEV1 3.54 (0.65) 1). Each subject was studied in both sitting and supine postures on two days; airway calibre was assessed by measuring total respiratory resistance (Rrs) at 6 Hz with a forced oscillation technique applied over 16 seconds of tidal breathing. Appropriate doses of histamine were selected by preliminary experiments and were always inhaled with the subject in the supine posture. Midtidal lung volume was larger in the sitting (2.9 (0.8) 1) than in the supine posture (2.4 (0.5) 1). Baseline Rrs was lower in the sitting than in the supine posture (2.03 (0.44) and 3.12 (0.76) cm H2O.1(-1).s*). The mean absolute increase in Rrs after the same dose of histamine was 1.22 cm H2O.1(-1).s in the sitting position (65.8% increase over baseline) and 1.39 cm H2O.1(-1).s (48.8% increase over baseline) in the supine position. The geometric mean provocation concentration of histamine causing a given percentage increase in Rrs was similar in the sitting (8.26 mg/ml) and supine (8.65 mg/ml) positions. Thus there was no significant increase in responsiveness after the reduction of airway dimensions and extra-airway distending forces that occurs in the supine posture.

Adult↗

PubMed1989

Postural changes in spontaneous and evoked regional diaphragmatic activity in dogs.

We addressed the question whether gravity-dependent differences in passive tension and length of the diaphragm are associated with differences in its regional activation. By using intramuscular electrodes, we measured the electromyographic activity of different parts of the diaphragm (Edi) during quiet breathing in several postures in 13 anesthetized mongrel dogs. The Edi of the left and right costal hemi-diaphragm was compared between the left and right lateral decubitus postures, whereas that from the substernal and crural regions was compared between the supine and prone positions. On changing posture, the Edi of the dependent part of the diaphragm decreased in both cases, whereas that of the non-dependent part increased. The results were consistent with reflex modulation of regional diaphragm activation in response to postural changes in local resting length. However, these changes in Edi persisted after bilateral vagotomy, cordotomy (C7-T1) and dorsal rhizotomy of the C5-C7 roots. Compound muscle action potentials, recorded in different regions of the diaphragm and evoked by supramaximal stimulation of the phrenic nerves, were altered with changes in posture in the same direction as Edi. Because the stimuli were supramaximal, these changes reflected systematic changes in the recording conditions with posture, possibly because of a combination of 1) changes in the electrical environment surrounding the intramuscular electrodes and 2) passive changes in muscle length. Our results demonstrate systematic, reproducible, posture-dependent changes in regional Edi that may not be due to different neural drive.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMed1991

Interactive effects of body posture and exercise training on maximal oxygen uptake.

To determine the effect of posture on maximal O2 uptake (VO2 max) and other cardiorespiratory adaptations to exercise training, 16 male subjects were trained using high-intensity interval and prolonged continuous cycling in either the supine or upright posture 40 min/day 4 days/wk for 8 wk and 7 male subjects served as non-training controls. VO2 max measured during upright cycling and supine cycling, respectively, increased significantly (P less than 0.05) by 16.1 +/- 3.4 and 22.9 +/- 3.4% in the supine training group (STG) and by 14.6 +/- 2.0 and 6.0 +/- 2.0% in the upright training group (UTG). The increase in VO2 max measured during supine cycling was significantly greater (P less than 0.05) in the STG than in the UTG. The increase in VO2 max in the UTG was significantly greater (P less than 0.05) when measured during upright exercise than during supine exercise. However, there was no significant difference in posture-specific VO2 max adaptations in the STG. A postural specificity was also evident in other maximal cardiorespiratory variables (ventilation, CO2 production, and respiratory exchange ratio). In the UTG, maximal heart rate decreased significantly (P less than 0.05) only during supine cycling; there was no significant difference in maximal heart rate after training in the STG. We conclude that posture affects maximal cardiorespiratory adaptations to cycle training. Additionally, supine training is more effective than upright training in increasing maximal cardiorespiratory responses measured during supine exercise, and the effects of supine training generalize to the upright posture to a greater extent than the effects of upright training generalize to the supine posture.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed2003

Contribution of genetic and environmental effects to postural balance in older female twins.

The aim of the present study was to determine the relative roles of genetic and environmental influences on postural balance in older women. The participants were 97 monozygotic (MZ) and 102 dizygotic (DZ) female twins, aged 64-76 yr. Postural sway was measured during side-by-side stance with eyes open and eyes closed, and during semitandem stance with eyes open on a force platform. Sway data were condensed into four first-order and one second-order latent factors. The second-order factor, named balance, incorporates sway data from multiple tests and thus best describes the phenotype of postural balance. The contribution of genetic and environmental influences on the variability of the latent factors was assessed by using structural equation modeling. Additive genetic influences accounted for 35% and shared environmental influences accounted for 24% of the total variance in the balance factor. In the present study, postural balance in older women had a moderate genetic component. Genetic influences on postural balance may be mediated through gene variation in the systems that control posture. The finding that individual environmental influences accounted for almost one-half of the variance in postural balance points to the potential of targeted interventions to maintain and improve balance control in older persons.

Aged↗

PubMed2006

Reduction of intracortical inhibition in soleus muscle during postural activity.

Short-interval intracortical inhibition (SICI) decreases during voluntary contraction of the target muscle. It is unknown whether this effect also occurs with postural contractions. We have compared the effects of voluntary and postural contractions on SICI in the soleus (SOL) muscle. We applied transcranial magnetic stimuli (TMS) in subjects under three tasks: sitting at rest (Rest), sitting while activating the SOL muscle (Voluntary), or standing quietly (Postural). In control trials, we applied suprathreshold TMS to obtain unconditioned motor-evoked potentials (MEPs). In test trials, the same TMS was preceded by a subthreshold TMS at different interstimulus intervals (ISIs), to obtain a conditioned MEP. SICI and intracortical facilitation (ICF) were expressed as the decrease or increase in MEP size relative to unconditioned MEPs. There was significant effect of task in mean SICI or mean ICF in SOL. Mean SICI in SOL was 52% in Rest and decreased to 21% in Voluntary and 15% in Postural. Mean ICF in SOL was 132% and decreased to 113% in Voluntary and to 108% in Postural. Mean SICI in SOL was not different in Voluntary and Postural tasks. There was no effect of task in mean SICI or mean ICF in TA. Our results indicate that decrease of SICI with muscle contraction occurs to a similar extent with tonic voluntary and postural activation, suggesting that those contractions require a similar type of cortical involvement. However, it cannot be excluded that some part of the SICI reduction with muscle contraction depends on changes in segmental excitability.

Adult↗

PubMed2000

Effect of posture and isoproterenol on beat-to-beat heart rate and QT variability.

RATIONALE: Recent literature emphasizes the utility of QT variability to study ventricular electrophysiologic function. In this investigation, we sought to test the hypothesis that beat-to-beat fluctuations in QT intervals are mediated by sympathetic activity in normal subjects using postural challenge and isoproterenol infusions. SUBJECTS AND METHODS: We obtained ECG in the supine and standing postures during spontaneous breathing, at 12, 15 and 20 per minute controlled breathing (n = 19), and before and after infusions of isoproterenol, a beta-adrenergic agent, in the supine posture during spontaneous breathing (n = 11) using lead II configuration in healthy human adult subjects. Heart rate (HR) and QT time series data were analyzed by spectral analysis of 256 s of real-time data. Beat-to-beat QT intervals were measured by automated analysis of ECG. A QT variability index (QT(vi)) was calculated for each subject as the logarithm of the ratio of normalized QT variance to normalized HR variance. We also calculated fractal dimensions of QT time series during spontaneous breathing. RESULTS: QT(vi) was significantly higher in the standing than in the supine posture (-1. 93 +/- 0.27 vs. -1.47 +/- 0.41; p = 0.0001), and also during isoproterenol infusions in the supine posture (-1.83 +/- 0.39 vs. -1. 27 +/- 0.43; p = 0.0001). Fractal dimensions of QT time series were also significantly higher during standing (p = 0.00001) and isoproterenol infusions (p = 0.0002). Respiratory rate or tidal volume did not account for the increased QT variability seen in the standing posture. CONCLUSIONS: A change from the supine to the standing posture as well as infusion of isoproterenol significantly increased the absolute as well as normalized QT variability, which appears to be due to an increase in sympathetic activity associated with these conditions.

Adult↗

PubMed1997

Calcium channel blockers blunt postural cutaneous vasoconstriction in hypertensive patients.

The aim of this work was to test whether calcium channel blockers interfere with skin vasoconstrictor reflexes that minimize postural increases in capillary pressure and avoid fluid extravasation and eventually subcutaneous edema. Studies were conducted in 23 untreated mild to moderate essential hypertensives; drugs, either calcium channel blockers or not, were given for 2 weeks according to a crossover, sequence-randomized design. Skin blood flow was measured by laser Doppler flowmetry in two skin areas: (1) the dorsum of the foot, where arteriovenous anastomoses are poorly represented, and (2) the plantar surface of the great toe, where those anastomoses are predominant. Determinations were obtained both with the foot at heart level and with it placed passively 50 cm below the heart level; percent flow changes from the horizontal to the dependent position were the measure of postural vasoconstriction. Two dihydropyridine derivatives, amlodipine (10 mg UID) and nifedipine (60 mg UID), and verapamil (240 mg BID), a chemically unrelated compound, diminished to similar extents the postural fall in skin blood flow at the dorsum of the foot. Blockade of alpha1-adrenergic and AT-1 subtype angiotensin II receptors by doxazosin (4 mg UID) and losartan (50 mg UID), respectively, exerted no effect. Postural skin blood flow responses at the plantar surface of the great toe were unmodified during the pharmacological trials. Thus, calcium channel blockers of different chemical origins antagonized postural skin vasoconstriction at the dorsum of the foot. The data indicate altered postural capillary blood flow regulation, since arteriovenous anastomoses are anatomically absent at this site; the effect was independent of either alpha1-adrenoceptor or angiotensin II receptor antagonism. Interference with skin postural vasoconstrictor mechanisms may result in net filtration of fluid to the extravascular compartment. This mechanism might explain the as yet unknown pathogenesis of ankle edema during treatment with calcium antagonists.

Adult↗

PubMed1991

Influence of posture and sustained loss of lung volume on pulmonary function in awake asthmatic subjects.

Nocturnal worsening occurs commonly in the asthmatic patient population and contributes substantially to the morbidity and even mortality of asthma. However, no physiologic process has yet been identified as the major contributor to this pattern. Sleep is typically associated with both the supine posture and substantial decrements in lung volume, and both have been proposed to have a role in the pattern of nocturnal worsening. To assess the effects of posture and sleep-associated reductions in functional residual capacity on pulmonary function, eight asthmatic patients were first monitored overnight in a horizontal volume-displacement body plethysmograph to determine mean FRC during sleep for each subject. We then compared, during wakefulness, the effects on FEV1 and methacholine responsiveness from chest wall and abdomen strapping (to maintain FRC at mean sleep levels) for 6 h in the supine and upright postures. FEV1 was significantly decreased after strapping in the supine posture (2.54 +/- 0.36 versus 3.38 +/- 0.29 L on control day, p = 0.0001) but was not affected by strapping in the upright posture (3.07 +/- 0.30 versus 3.34 +/- 0.31 L on control day, not significant, NS). Bronchial responsiveness to methacholine was not altered after strapping in either posture. These observations suggest that the supine posture, in conjunction with the reduction in lung volume associated with sleep, may contribute to the nocturnal worsening of asthma.

Adult↗

PubMed1991

The effect of posture on upper airway dimensions in normal subjects and in patients with the sleep apnea/hypopnea syndrome.

The effect of posture on upper airway dimensions was assessed for two reasons. First, some patients with untreated sleep apnea/hypopnea syndrome (SAHS) report they sleep better sitting upright. Second, to allow comparison of the differing techniques used to determine the site of maximal airway narrowing in awake patients with SAHS, as some are carried out in the erect and others in the supine posture. Lateral cephalometry was therefore carried out in 33 nonsnoring normal subjects and in 29 patients with obstructive SAHS (mean apneas plus hypopneas, 46 per hour; range, 17 to 103). In both normal subjects and patients, uvular width was increased (p less than 0.05) in the supine posture, and this was associated with significant narrowing of the retropalatal airway in the patients with SAHS (erect, 5.0 +/- SD 2.6 mm; supine, 3.6 +/- 2.8 mm; p less than 0.01). In both normal subjects and patients, the retroglossal hypopharynx widened (p less than 0.05) in the supine posture (e.g., in patients with SAHS, posterior airway space was: erect, 11.5 +/- 4.5 mm; supine, 13.4 +/- 4.8 mm; p = 0.003). In the supine posture there was anterior movement of the hyoid and neck flexion in both groups. However, a study of the effect of neck flexion in the erect posture showed that neck flexion produced no changes in airway caliber. Thus, posture is an important determinant of upper airway dimensions.

Adult↗

PubMed2004

Postural stability after vestibular schwannoma surgery.

Factors related to postural stability and the course of recovery after vestibular schwannoma surgery were analyzed in a retrospective study of 177 patients and in a prospective study of 44 patients. Before surgery, 7 of the 44 patients in the prospective group complained of postural instability. The body sway velocity was measured. In the retrospective study, the sway velocity was abnormal under nonvisual control in 63% of the patients and under visual control in 34%. The sway velocity correlated with tumor size, smooth pursuit deficit, and postoperative work history. We compared patients with abnormal postural control to those with normal postural control, and found that the former relied to a greater extent on visual information and the latter on proprioceptive information. In the prospective study, the sway velocity increased after the operation, and 1 year after surgery it had not returned to preoperative values. In the logistic regression analysis, a translabyrinthine approach, rehabilitation, the patient's age, and preserved function of the facial nerve predicted a good outcome of postural stability. The retrosigmoid approach and depression were the most significant risk factors for postoperative gait difficulties. Vestibular rehabilitation increased the reliance on proprioception for maintenance of postural control and improved postural stability.

Adult↗

PubMed2004

Bilateral deficits in postural control following lateral ankle sprain.

BACKGROUND: Although postural control deficits have been identified after lateral ankle sprains, objective and subjective comparisons of data before and after injury are limited. The purpose of this project was to prospectively assess and compare the changes in postural control and self-reported functional status in athletes who suffer acute lateral ankle sprains. We evaluated postural control and self-reported functional status before injury and at 1, 7, 14, 21, and 28 days after acute lateral ankle sprain. METHODS: Postural control in single-limb stance and self-reported functional status were evaluated in 460 collegiate athletes during preseason examinations. Twenty-eight athletes suffered a lateral ankle sprain during the competitive season and participated in testing at 1, 7, 14, 21, and 28 days after injury. RESULTS: Significant deficits in postural control were noted in both the injured and the uninjured ankles at 1 day after injury compared to the baseline measurements taken during the preseason examinations. Significant differences (p < .05) also were noted between the uninjured and injured ankles at 1, 7, and 21 days after injury. CONCLUSIONS: After lateral ankle sprain, postural control deficits occur in the injured and uninjured ankles, suggesting a central impairment in neuromuscular control. Changes in self-reported functional status followed a trend of deficit and improvement that was similar to that shown by the postural control data taken after injury, but the two measures did not strongly correlate.

Acute Disease↗

PubMed2005

The effect of condyle fossa relationships on head posture.

Although it is commonly accepted that there is an interrelationship between the temporomandibular joint (TMJ) and head posture, few, if any, previous studies have quantified this effect. The purpose of this study is to quantify the effect of a change in the condyle fossa relationship of symptomatic temporomandibular joints on head posture. Charts of 51 patients (N=10 men and N=41 women) with symptomatic TMJ pathology were reviewed. The condyle fossa relationships were measured pre- and posttreatment using sagittal corrected hypocycloidal tomography. The amount of slant between the shoulder and external auditory meatus (EAM) was measured in pre- and posttreatment photographs as an indicator of forward head posture; less slant indicates better posture. Subjects ranged in age from 13-74 years (mean=43.1) and had been treated for an average of 5 months. Comparisons with pre-treatment measures showed that after treatment, the amount of retrodiskal space was significantly increased by an average of 1.67 mm on the left side (t=-10.11, p<0.0001) and 1.92 mm on the right (t=-9.62, p<0.0001). Comparisons also showed that after treatment, the amount of slant between the shoulder and EAM decreased by 4.43 inches on average which was also significant (t=13.08, p<0.0001). Improvement in the condyle fossa relationship was related to decreased forward head posture. This suggests that optimizing mandibular condyle position should be considered in the management of forward head posture (adaptive posture).

Adolescent↗

PubMed2003

Postural stability is altered by the stimulation of pain but not warm receptors in humans.

BACKGROUND: It is now recognized that large diameter myelinated afferents provide the primary source of lower limb proprioceptive information for maintaining an upright standing position. Small diameter afferents transmitting noxious stimuli, however, can also influence motor behaviors. Despite the possible influence of pain on motor behaviors, the effects of pain on the postural control system have not been well documented. METHODS: Two cutaneous heat stimulations (experiment 1: non-noxious 40 degrees C; experiment 2: noxious 45 degrees C) were applied bilaterally on the calves of the subject with two thermal grills to stimulate A delta and C warm receptors and nociceptors in order to examine their effects on postural stability. The non-noxious stimulation induced a gentle sensation of warmth and the noxious stimulation induced a perception of heat pain (visual analogue scores of 0 and 46 mm, respectively). For both experiments, ten healthy young adults were tested with and without heat stimulations of the lower limbs while standing upright on a force platform with eyes open, eyes closed and eyes closed with tendon co-vibration of tibialis anterior and triceps surae muscles. The center of pressure displacements were analyzed to examine how both stimulations affected the regulation of quiet standing and if the effects were exacerbated when vision was removed or ankle proprioception perturbed. RESULTS: The stimulation of the warm receptors (40 degrees C) did not induce any postural deterioration. With pain (45 degrees C), subjects showed a significant increase in standard deviation, range and mean velocity of postural oscillations as well as standard deviation of the center of pressure velocity. The effects of heat pain were exacerbated when subjects had both their eyes closed and ankle tendons vibrated (increased standard deviation of the center of pressure velocity and mean velocity of the center of pressure). CONCLUSIONS: A non-noxious stimulation (40 degrees C) of the small diameter afferents is not a sufficiently intense sensory stimulation to alter the control of posture. A painful stimulation (45 degrees C) of the skin thermoreceptors, however, yielded a deterioration of the postural control system. The observed deteriorating effects of the combined stimulation of nociceptors and Ia afferents (when ankle tendons were vibrated) could result from the convergence of these afferents at the spinal level. This could certainly lead to the hypothesis that individuals suffering from lower limb pain present alterations of the postural control mechanisms; especially populations already at risk of falling (for example, frail elderly) or populations suffering from concomitant lower limb pain and sensory deficits (for example, diabetic polyneuropathy).

Adult↗

PubMed1976

Circadian rhythm and effect of posture on plasma aldosterone concentration in primary aldosteronism.

The effect of circadian rhythm and alterations in posture on plasma aldosterone concentration was studied in 13 patients with primary aldosteronism (six adenoma, five idiopathic hyperplasia, two carcinoma) to define the regulatory mechanism in each of these pathologic subtypes. Blood samples for aldosterone, cortisol, renin, and potassium concentrations were obtained every 4 h during prolonged recumbency (32 h) and upright posture (16 h). During recumbency, aldosterone and cortisol followed a normal circadian pattern in patients with adenoma and hyperplasia, with peak values at 0400-0800 h and the nadir at 1600-2400 h. Normalized aldosterone and cortisol values correlated significantly in both groups (adenoma r=+0.66, P less than 0.001; hyperplasia r=+0.42, P less than 0.01). With upright posture, aldosterone levels declined parallel to the normal circadian fall in cortisol in patients with adenoma (r=+0.68, P less than 0.001); whereas aldosterone levels increased in patients with hyperplasia parallel to small increments in renin (r=+0.65, P less than 0.001) and potassium (r=+0.64, P less than 0.001). During the administration of dexamethasone, aldosterone no longer correlated with cortisol in patients with adenoma but continued to correlate with renin during upright studies in patients with hyperplasia (r=+0.77, P less than 0.01). Aldosterone circadian rhythm was abnormal in patients with carcinoma and no effect of posture was noted. Unilateral adrenalectomy restored the normal postural relationship in four patients with adenoma. These studies suggest that aldosterone secretion is under continuous ACTH control regardless of posture in patients with adenoma, whereas persistent adrenal responsiveness to small increments in renin and/or potassium mediate the postural increase in plasma aldosterone in patients with hyperplasia. True adrenal autonomy occurs only in patients with adrenal carcinoma and when ACTH is suppressed in those with adenoma.

Adult↗

PubMed2004

Postural control in children: implications for pediatric practice.

Based on a systems theory of motor control, reactive postural control (RPA) and anticipatory postural control (APA) in children are reviewed from several perspectives in order to develop an evidence-based intervention strategy for improving postural control in children with limitations in motor function. Research on development of postural control, postural control in children with specific motor disabilities, and interventions to improve postural control is analyzed. A strategy for intervention to improve postural control systems at the impairment and functional activity levels based on a systems theoretical perspective is presented. Suggestions for research to improve evidence for best practice are provided.

Child↗

PubMed1996

Effect of posture on the flow-volume loop in two patients with euthyroid goiter.

In two patients with a goiter and respiratory symptoms occurring only in the recumbent posture, flow-volume loops (FVLs) were performed in various body postures: while sitting upright, supine, and left and right lateral decubitus. In both patients, flow rates, upper airway obstruction indices, and FVL morphologic features with patients in recumbent postures indicated the appearance of upper airway flow limitation with patients in the recumbent posture as compared with the upright posture. In the one patient who underwent thyroid surgery, these posture-related changes disappeared. We conclude that in patients with a goiter (or any extrinsic mass near to the upper airway), the comparison of FVLs performed in various body positions may help to clarify the origin of posture-related respiratory symptoms.

Adult↗

PubMed1998

Transient change in standing posture after linear treadmill locomotion.

Postural sway was measured in 24 healthy subjects after running or walking with eyes open on a standard treadmill exerciser. The speeds of running and walking were set at 10 and 7 km/h, respectively, and locomotion was maintained for 7 min. The postural sway response was characterized by systematic forward displacement followed by gradual decay to baseline and was accompanied by self-motion perception. Mean fore-back postural after sway was significantly greater after treadmill running than after normal running. The aftereffects of treadmill walking were significantly less than those of treadmill running. The 6 subjects showing distinct forward postural sway after treadmill walking were instructed to walk on the treadmill with their eyes closed. After this, none of the 6 subjects felt self-motion perception and had no evidence of postural aftersway. These results clearly demonstrate that vision during treadmill locomotion plays an important role in evoking postural sway after treadmill locomotion. It can be inferred that somatosensory/motor signals may be stored during visual-somatosensory/motor conflict and that this stored information may evoke postural change and self-motion perception.

Adult↗

PubMed2005

Mechanical impedance and absorbed power of hand-arm under x(h)-axis vibration and role of hand forces and posture.

The biodynamic responses of the hand-arm system under x(h)-axis vibration are investigated in terms of the driving point mechanical impedance (DPMI) and absorbed power in a laboratory study. For this purpose, seven healthy male subjects are exposed to two levels of random vibration in the 8-1,000 Hz frequency range, using three instrumented cylindrical handles of different diameters (30, 40 and 50 mm), and different combinations of grip (10, 30 and 50 N) and push (0, 25 and 50 N) forces. The experiments involve grasping the handle while adopting two different postures, involving elbow flexion of 90 degrees and 180 degrees, with wrist in the neutral position for both postures. The analyses of the results revealed peak DPMI magnitude and absorbed power responses near 25 Hz and 150 Hz, for majority of the test conditions considered. The frequency corresponding to the peak response increased with increasing hand forces. Unlike the absorbed power, the DPMI response was mostly observed to be insensitive to variations in the excitation magnitude. The handle diameter revealed obvious effects on the DPMI magnitude, specifically at frequencies above 250 Hz, which was not evident in the absorbed power due to relatively low velocity at higher frequencies. The influence of hand forces was also evident on the DPMI magnitude response particularly at frequencies. above 100 Hz, while the effect of hand-arm posture on the DPMI magnitude was nearly negligible. The magnitude of power absorbed within the hand and arm was observed to be strongly dependent upon the excitation level over the entire frequency range, while the influence of hand-arm posture on the total absorbed power was observed to be important. The effect of variations in the hand forces on the absorbed power was relatively small for the bent elbow posture, while an increase in either the grip or the push force coupled with the extended arm posture resulted in considerably higher energy absorption. The results suggested that the handle size, hand-arm posture and hand forces, produce coupled effect on the biodynamic response of the hand-arm system.

Arm↗