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PubMed1986

Posture switching for prolonging functional electrical stimulation standing in paraplegic patients.

The presently employed posture for Functional Electrical Stimulation (FES) assisted standing in spinal cord injury (SCI) patients utilises the active locking of knee joints by tetanically stimulating the quadriceps muscle. The hip joints are in hyperextension and the ankle joints remain free. The upper limbs are used for balancing. This posture requires minimal corrective forces exerted by the hands, the weight is transferred across the legs, while very limited forward-backward sway is permitted. Knee jack-knifing may occur in the instance when the gravity knee bending moment exceeds the moment generated by the quadriceps muscle. Because of these effects and fatiguing of the M. quadriceps the standing time is short, lasting from several minutes up to an hour, depending on the condition of the patient's muscles. Cyclical FES with a duty cycle of 10-20 seconds (on/off) fatigues muscle considerably less. The use of different postures for standing requiring activation of different muscles permits the application of cyclical FES. The cyclic FES results in prolonging standing times by a factor of two to five. Utilising this improvement some patients can stand for up to five hours at a time. This functional achievement is comparable to the standing time of a normal man. The incorporation of the principle of posture switching also prolongs standing in patients with weak muscles, because of the possibility of cyclical coactivation of different synergistic muscle assemblies. It is shown that posture switching can be carried out automatically and that patients adapt quickly to it. In addition using co-contraction of two or three muscles with posture switching does further expand the range of suitable patients and improves standing with an increased permissible range of body sway. Also, the FES antigravity action obtained raises hopes for substantially improving FES induced reciprocal gait.

Electric Stimulation Therapy↗
PubMed1986

Effect of posture on plasma immunoreactive atrial natriuretic peptide concentrations in man.

The effect of changes of posture on plasma atrial natriuretic peptide concentrations and renal function was studied in normal human volunteers. Plasma atrial natriuretic peptide concentrations increased in the supine posture, reached a maximum value after 30-60 min, remained elevated for 4 h and decreased to baseline values on return to the upright posture. Inflation of antishock trousers, which apply positive pressure to the legs and lower abdomen, attenuated the fall in plasma atrial natriuretic peptide concentration in the upright position. In the supine posture there were increases in urine flow rate, sodium, lithium, fractional sodium and fractional lithium clearances. Fractional distal water and sodium excretion, and total distal water and sodium reabsorption, which were estimated by the lithium clearance technique, also increased. Heart rate and systolic and diastolic blood pressures decreased in the supine and increased on return to the upright posture. Inflation of antishock trousers prevented the increase in heart rate in the upright posture. The contribution of haemodynamic factors to the increase in plasma atrial natriuretic peptide concentrations in the supine position and the relationship between this increase and the associated changes in renal function are discussed. However, the contribution of atrial natriuretic peptide to these changes is uncertain.

Adult↗
PubMed2002

Effects of mandibular position and body posture on nasal patency in normal awake subjects.

The purpose of this study was to examine the changes in nasal patency induced by forward mandibular displacement or changes in body posture. Fifteen healthy adults participated in this study. To examine the influence of mandibular position, nasal resistance was recorded in intercuspal, middle, and maximum forward positions. To evaluate the effect of body posture, nasal resistance was recorded in the four postures of sitting erect, 30 degrees and 60 degrees dorsally reclined, and supine. The nasal patencies recorded in the middle and maximum forward mandibular positions were significantly higher than those recorded in the intercuspal position. Regarding the effect of body posture, the nasal patency showed a progressive decrease from the sitting erect position to the supine position. These results suggest that changes in mandibular position and body posture significantly affect nasal patency and that mandibular position and body posture should be considered basic information in the treatment of obstructive sleep apnea.

Adult↗
PubMed1997

Mechanisms of cutaneous vasoconstriction during upright posture.

The cutaneous circulation is thought to participate in the neurocirculatory adjustments during orthostatic stress, but the underlying mechanisms mediating such reflex cutaneous vasoconstriction are poorly understood. The aim of this study was to assess the relative importance of baroreceptor (cardiopulmonary and arterial) and positional (vestibular, exercise, veno-arteriolar and myogenic) reflexes in triggering cutaneous vasoconstriction during upright posture. First, hypotensive lower body negative pressure (LBNP) was compared with actual postural changes to assess the relative contributions of baroreceptor reflexes and positional reflexes. Then changes in body position were compared with changes in limb position in the absence or presence of proximal (axillary) or distal (local cutaneous) nerve blocks, to assess the relative contributions of vestibular, exercise, veno-arteriolar and myogenic reflexes. Skin sympathetic nerve activity was determined by microneurography, and skin blood flow was determined by laser Doppler velocimetry. LBNP of -50 mm Hg cardiopulmonary + arterial baroreceptors) had no effect on skin sympathetic nerve activity or skin vascular resistance. In contrast, an upright posture with the arms dependent (baroreceptor + vestibular + exercise + veno-arteriolar reflexes) caused a two- to threefold increase in skin vascular resistance. In the supine position passive movement of the arm into a dependent position to activate veno-arteriolar reflexes alone evoked an increase in skin vascular resistance which approximated the response to normal upright posture. Blocking central sympathetic nerve impulses by application of an axillary blockade did not influence the cutaneous vasoconstrictor response to an upright posture or changes in limb position. In contrast, application of a distal nerve block by local cutaneous surface anaesthesia completely blocked vasoconstrictor responses evoked by these manoeuvres. In conclusion, these experiments in human subjects identify a primary role for veno-arteriolar reflexes in triggering vasoconstriction in the cutaneous circulation during upright posture.

Adult↗
PubMed1998

A 2-year follow-up of mandibular posture following an increase in occlusal vertical dimension beyond the clinical rest position with fixed restorations.

While resting mandibular posture is continuously changing, repeatable relations of 'physiologic rest position' (PRP) and 'clinical rest position' (CRP) are described in the literature. The PRP is defined as a position of minimal muscle activity and CRP as a more closed clinical reference relation. Relaxed resting posture (RRP) is a repeatable postural range obtained by operator-induced relaxation techniques. This article reports on measurements of mandibular posture in a patient group following an increase in occlusal vertical dimension (OVD) with fixed restorations beyond CRP over 2 years. The relationship of CRP and RRP in the restored and a non-restored control group is compared. The relationship of RRP and corresponding masseteric EMG values to baseline minimal EMG levels is reported for both groups. Resting face height adapted to the increased OVD and remained consistent over 1 and 2 years. The RRP was greater and significantly different from CRP in both groups (P = 0.0001). Results indicated that both CRP and RRP were postural ranges and not specific postural positions. The RRP occurred at minimum baseline EMG levels for both groups and appears to be consistent with physiologic rest position. The possibility of achieving minimal EMG levels at varying interocclusal rest space relations is discussed.

Adaptation, Physiological↗
PubMed1999

The effect of head posture on direction and stability of mandibular closing movement.

This study investigated the effects of head posture on mandibular habitual closing movement. Ten healthy subjects were examined. Head posture was evaluated as a sagittally viewed inclination of the head, and was changed from 25 degrees forward bending up to 30 degrees backward bending in 5 degrees increments. The mandibular opening and closing movement was measured at each head posture. As the head bended forward, the closing path approached the maximum intercuspal position from the anterior region, and as the head was bent backward, the closing path approached the maximum intercuspal position from the posterior region. However, the limit of this relationship was found when the head was bent forward to some extent. There was also a correlation between the head posture and the stability of the closing movement. The forward bending of the head decreased the stability of the closing path, and conversely, the backward bending increased the stability of the closing path. It was concluded that the head posture affects the direction and stability of the mandibular closing movement. Possible underlying reasons for these findings are masticatory muscle activity and the tension and resistance of inframandibular soft tissue varying with the change of head posture.

Adolescent↗
PubMed2002

Is there a relationship between head posture and craniomandibular pain?

An often-suggested factor in the aetiology of craniomandibular disorders (CMD) is an anteroposition of the head. However, the results of clinical studies to the relationship between CMD and head posture are contradictory. Therefore, the first aim of this study was to determine differences in head posture between well-defined CMD pain patients with or without a painful cervical spine disorder and healthy controls. The second aim was to determine differences in head posture between myogenous and arthrogenous CMD pain patients and controls. Two hundred and fifty persons entered the study. From each person, a standardized oral history was taken and blind physical examinations of the masticatory system and of the neck were performed. The participants were only included into one of the subgroups when the presence or absence of their symptoms was confirmed by the results of the physical examination. Head posture was quantified using lateral photographs and a lateral radiograph of the head and the cervical spine. After correction for age and gender effects, no difference in head posture was found between any of the patient and non-patient groups (P > 0.27). Therefore, this study does not support the suggestion that painful craniomandibular disorders, with or without a painful cervical spine disorder, are related to head posture.

Adult↗
PubMed1998

Effect of postural change on urine volume and urinary sodium excretion in diabetic nephropathy.

Fluid retention develops relatively early in the renal insufficiency of patients with diabetic nephropathy. The objective of this study was to clarify the effect of postural change on urine volume and urinary sodium excretion in diabetic nephropathy. Subjects consisted of 16 patients with non-insulin-dependent diabetes mellitus (five with diabetic nephrotic syndrome [DNS], five with nonnephrotic overt diabetic nephropathy [NNODN], and six without overt diabetic nephropathy [ODN]) and 11 patients with nondiabetic renal diseases (five with nondiabetic nephrotic syndrome [NDNS] and six without nephrotic syndrome). Patients were studied during 60 minutes of recumbency, followed by 60 minutes of standing. Mean blood pressure decreased in the standing posture only in patients with DNS and nondiabetic renal diseases. Urine volume decreased in the standing posture in the three groups of diabetic patients. Urine volume showed no changes in the standing posture in nondiabetic patients with and without nephrotic syndrome. The decreases in mean blood pressure and urine volume and the percentage decrease in creatinine clearance were significantly larger in patients with DNS than in those with NDNS and NNODN. The increase in free water clearance was significantly smaller in patients with DNS than in those with NDNS and NNODN. Urinary sodium excretion decreased in the standing posture in diabetic and nondiabetic patients, while no differences in the magnitude of changes were noted among patients with NDNS, NNODN, and DNS. It is concluded that the standing posture causes a greater decrease in urine volume due to orthostatic hypotension in patients with DNS compared with those with NDNS and NNODN, and that the presence of orthostatic hypotension in patients with DNS is likely responsible for the greater fluid retention of this group compared with other nephrotic patients with similar degrees of hypoalbuminemia.

Adult↗
PubMed2001

Rehabilitation of postural disturbances of hemiplegic patients by using trunk control retraining during exploratory exercises.

OBJECTIVE: To assess use of the Bon Saint Côme device for axial postural rehabilitation in hemiplegic patients, a technique based on voluntary trunk control during exploratory retraining. DESIGN: A 3-month randomized controlled trial. SETTING: A public neurorehabilitation center. PATIENTS: Twenty consecutive hemiplegic patients with axial postural disturbance resulting from recent stroke were randomly assigned to a device group (DG) or control group (CG). The 2 groups of 10 patients were similar. INTERVENTION: For 1 month, the DG patients followed an experimental program for 1 hour daily and conventional neurorehabilitation for 1 hour daily, whereas CG patients had conventional neurorehabilitation for 2 hours daily. For the next 2 months, all 20 patients had conventional neurorehabilitation for 2 hours daily. MAIN OUTCOME MEASURES: Patients were assessed on days 0, 30, and 90 by using a battery of postural tests, gait evaluation, the Bells neglect test, and the FIM instrument. RESULTS: On day 30, postural and neglect tests improved significantly more in DG than in CG. The benefit remained at day 90. Gait improved earlier in DG than in CG. FIM scores improved equally. CONCLUSIONS: Voluntary trunk control retraining during spatial exploration with the Bon Saint Côme device appears to be a useful approach for rehabilitation of postural disorders in hemiplegic patients. Treatments designed to improve spatial cognition deficits probably enhance postural disorder recovery in hemiplegia.

Activities of Daily Living↗
PubMed2003

Catecholamine response during haemodynamically stable upright posture in individuals with and without tilt-table induced vasovagal syncope.

AIM: Changes in circulating catecholamine concentrations during vasovagal faints have been the subject of considerable study. However, whether catecholamines are part of the triggering mechanism, or principally reflect attempted compensation for an evolving circulatory crisis is unknown. To address this issue, we determined whether the circulating catecholamine response to upright posture differs among patients with and without inducible vasovagal faints at a time when there is no detectable haemodynamic compromise. METHODS AND RESULTS: Blood samples for measurement of adrenaline and noradrenaline (Norepi) concentrations were obtained in the baseline state, and at both 2-3 min and 4-6 min of upright posture in 22 patients undergoing head-up tilt-table testing for evaluation of syncope of unknown cause. In 11 individuals tilt-testing induced syncope at >5 min head-up posture (Group 1). In 11 other individuals tilt testing did not result in syncope (Group 2). Supine arterial catecholamine levels were comparable in the two groups. However, adrenaline concentrations during upright posture tended to be greater at 2-3 min and were significantly greater at 4-6 min in Group 1 than in Group 2 (P< 0.01). These differences occurred in the absence of significant intergroup differences in mean arterial pressure or cardiac cycle lengths. Norepi concentrations also increased in both groups, but without significant differences. CONCLUSION: Circulating adrenaline concentrations in posturally induced vasovagal faints rise more rapidly in vasovagal fainters than in comparably posturally stressed non-fainters, and were significantly greater in fainters prior to either detectable haemodynamic compromise or diminution of circulating Norepi levels. These findings suggest that a premonitory rise in adrenaline concentrations occurs in vasovagal fainters unassociated with an evolving circulatory crisis.

Adolescent↗
PubMed1996

The effect of posture on central blood volume in patients with preascitic cirrhosis on a sodium-restricted diet.

The status of the central blood volume in cirrhosis is controversial. A combination of sodium restriction and upright posture, which redistributes intravascular volume to dependent parts of the body should further aggravate a contracted central blood volume reduction. The aim of this study was to determine the effect of upright posture and sodium restriction on central blood volume (CBV) in preascitic cirrhotic patients, compared with controls. Eight male, preascitic, alcoholic cirrhotic subjects and eight healthy male controls were studied while on a 20-mmol/d sodium diet. Measurements of CBV by radionuclide angiography, and neurohumoral factors were performed on day 7 in both supine and erect positions and cardiac output and systemic vascular resistance (SVR) was calculated. Sodium restriction resulted in less weight loss in the cirrhotic patients (P = .03), with significantly lower plasma renin activity (P = .001). Similar central blood volumes and systemic hemodynamics were observed in both groups in the supine posture. In contrast to the cirrhotic patients, in the control subjects, upright posture resulted in a significant reduction in cardiac output (P = .002) and increase in SVR (P = .005), associated with a decrease in all blood volumes which were significantly less than in the cirrhotic patients. Mean arterial pressure was maintained in both groups in both postures. In conclusion, with sodium restriction, preascitic cirrhotic patients have less intravascular volume contraction than control patients. Erect posture results in redistribution of this relatively expanded intravascular volume to the CBV. Therefore, a low-sodium diet can be safely administered in preascitic cirrhotic patients.

Adult↗
PubMed2001

Influence of patient posture on oxygen saturation during fibre-optic bronchoscopy.

This study was designed to investigate the effect of posture on oxygen saturation during fibre-optic bronchoscopy (FOB). Thirty-eight consecutive patients requiring diagnostic FOB were randomized into two groups according to the initial posture in which the FOB was performed. In group 1 (20 patients), FOB was commenced supine, and in group 2 (18 patients) in a semi-recumbent position (45 degrees from horizontal). Sedation with midazolam was titrated according to clinical response. All patients received atropine 0.6 mg intravenously and topical lignocaine. Observations of peak, trough and plateau oxygen saturation and pulse rate were recorded during six study periods, each lasting 3 min. Periods 1 and 2 were pre- and post-sedation without supplemental oxygen, respectively. The bronchoscope was then inserted into the distal end of the trachea and observations taken during periods 3 and 4 (no supplemental oxygen) and periods 5 and 6 (2 l oxygen by nasal cannulae). In group 1, posture was changed from supine to semi-recumbent from periods 3-4 and reversed in periods 5 and 6. In group 2, posture changes were in reverse sequence. Patients with initial oxygen saturation of less than 90% or showing a fall below 85% during FOB were excluded. Five patients from each group were withdrawn because of hypoxia. In both groups, oxygen saturation fell significantly (P<0.001) following sedation. There was no significant change in saturation (peak, trough or plateau) with change in posture from supine to semi-recumbency (group 1) or the reverse (group 2). These correspond to periods 3-4 and 5 6 in both groups. Supplemental oxygen was associated with a significant rise in oxygen saturation in both postures, attaining levels close to presedation levels.

Adult↗
PubMed1984

Effect of body posture on the serum potassium response to glucose in healthy subjects, diabetics and hyperthyroid patients.

Administration of glucose induces normally a decrease in serum potassium, though exceptionally a paradoxcial increase (PGIH) may occur. The effect of posture on glucose-induced serum potassium changes in health and disease has not been previously studied. We have investigated the influence of changes in body posture on the different serum potassium responses to glucose in various groups of 47 subjects. We have found a smaller decrease in serum potassium in the upright position than in the recumbent one in 20 healthy subjects and in 12 non-insulin dependent diabetics, but no significant difference in hyperthyroidism. The variable effect of posture on glucose-induced insulin secretion in the various groups of subjects did not provide explanation for the postural inhibition of the normal serum potassium response to glucose. A tendency to PGIH was found in a small number of diabetics. Although PGIH was completely reversed by DOC the normal postural difference between serum potassium curves was uneffected. It was concluded that change in the body posture has a definite influence on the glucose-induced decrease in serum potassium in normal people and is not mediated by insulin and/or aldosterone; PGIH develops in the upright position more easily than recumbency; exact serum potassium changes after glucose loading can be explored only by adequate standardization and carrying out both recumbent and upright measurements.

Adult↗
PubMedDate not supplied

[Function of back extensor muscles in upright standing position and during sitting with identical back posture--an electromyography study].

PROBLEM: There is a controversial discussion about the loading of the spine by the force of the extending muscles of the back in upright sitting with the back curved as in upright standing. Experimental studies investigating this issue are still lacking. METHODS: In the study presented in this paper we measured in 30 subjects the activity of the extending back muscles both in a natural upright standing posture and in sitting with identical posture of the back as recommended in some back training programs. To this end we recorded the electromyographical surface activity of the back muscles at four levels of the spine in both postures. The EMG activities were intraindividually normalized with reference to the respective activity recorded at maximum voluntary isometric contraction (MVC). RESULTS: At three of the four levels of the spine examined, the group averages of the EMG activity in sitting were significantly higher than in standing (p < 0.001). The maximum activity enhancement evaluated was 48% at Th12. The force of the lower back muscles in sitting with a posture of the back as in natural upright standing could be estimated to be at least greater than 30% of the force at MVC. CONCLUSION: The force needed to enforce in sitting a posture of the back identical to the posture at natural standing entails lower back muscle fatigue in a few minutes. The results of our study agree with recent experimental findings about an increased loading of the spine in lordotic sitting.

Adolescent↗
PubMed2006

Dynamic postural stability in blind athletes using the biodex stability system.

Three systems affect the upright standing posture in humans - visual, vestibular, and somatosensory. It is well known that the visually impaired individuals have bad postural balance. On the other hand, it is a well documented fact that some sports can improve postural balance. Therefore, it is aimed in this study to evaluate the dynamic postural stability in goal-ball athletes. Twenty blind goal-ball players, 20 sighted and 20 sedentary blind controls were evaluated using the Biodex Stability System. Three adaptation trials and three test evaluations (a 20-second balance test at a platform stability of 8) were applied to the blind people, and to the sighted with eyes open and closed. Dynamic postural stability was measured on the basis of three indices: overall, anteroposterior, and mediolateral. Means of each test score were calculated. The tests results were compared for the blind athletes, sighted (with eyes open and closed) subjects, and sedentary blind people. There were significant differences between the results of the blind people and the sighted subjects with regards to all of the three indices. Although the stability of goal-ball players was better than sedentary blinds', only ML index values were statistically different (4.47 +/- 1.24 in the goal-ball players; 6.46 +/- 3.42 in the sedentary blind, p = 0.04). Dynamic postural stability was demonstrated to be affected by vision; and it was found that blind people playing goal-ball 1 - 2 days per week have higher ML stability than the sedentary sighted people.

Adolescent↗
PubMed2001

Changes in postural control in healthy elderly subjects are related to vibration sensation, vision and vestibular asymmetry.

The aim of this study was to analyze the composition of sway in adults and "healthy" elderly people and to evaluate the influence of vibration sensation and asymmetric vestibular function on the sway pattern. Ten adults with a mean age of 37.5 years and 40 healthy senior citizens with a mean age of 74.6 years living independently in the community were studied. Vibration-induced body sway was measured on a force platform. The sway was analyzed and separated into its high and low frequency components above and below 0.1 Hz, respectively. Additionally the elderly subjects were observed for the occurrence of spontaneous gaze and head shake-induced nystagmus using infrared charge-coupled device cameras and the vibration perception in the lower limbs was tested with a tuning fork. Vibration perception was the major determinant for postural control in the elderly subjects. Postural control among the elderly subjects with intact vibration perception in their lower limbs was very similar to that of the adults. The elderly subjects with impaired vibration sensation had increased high frequency sway compared to adults and the elderly subjects with intact sensation. Regardless of the strong influence of vibration sensation on postural control, asymmetric vestibular function might also be a contributing factor to postural instability in the elderly. Age per se had little effect on the outcome of the tests except that the elderly subjects had diminished ability to use visual cues to reduce postural sway. We concluded that sensory status in the lower limbs is of utmost importance for postural control in the elderly. Rehabilitation programs for senior citizens should therefore include exercises to preserve recognition of body motion by the lower limbs. Exercises to facilitate vestibular compensation could be useful for elderly people with vestibular dysfunction.

Adult↗
PubMed2002

Sound-evoked postural responses in normal subjects.

A pattern of sound-induced paroxysms of the eye and head and other spinal motor neuron synkinesis (Tullio's phenomenon) in human subjects always implies either a pathological contiguity of the tympano-ossicular chain and membranous labyrinth or a dehiscence of the bone overlying the superior semicircular canal. However, it has become clear in the last decade that sound-evoked vestibular stimulation is not only a sign of disease but also a physiological phenomenon, The examination of such physiologically sound-induced vestibular (saccular) responses contributes today to the clinical testing of the vestibular organ, mainly in the form of vestibular-evoked myogenic potentials. In this study it was observed that, in a group of 20 normal subjects, a 500 Hz tonal stimulus of high intensity (105 dB HL = 118.5 dB SPL), applied monoaurally, elicited postural responses. Each subject was studied under 4 different conditions: (i) head facing forwards, eyes open; (ii) head facing forwards, eyes closed; (iii) head rotated approximately 90 degrees to the right, eyes closed: and (iv) head rotated approximately 90 degrees to the left, eyes closed. Body sway, measured using a force platform, was recorded in all subjects, with eyes either open or closed. Postural responses, which were also elicited with a 250 Hz tonal stimulus, were not observed with a tone of 2000 Hz, with legs slightly flexed or with binaural stimulation. The postural sway (head facing forwards, eyes open or closed) was in a lateral direction towards the stimulated ear: with the stimulus applied to the right ear the subject had postural sway towards the right, with the stimulus applied to the left ear towards the left. When the head was rotated approximately 90 degrees sideways and the stimulus was given facing forwards (i.e. head rotated contralaterally to stimulated ear) the postural sway was in a forward direction; when the head was rotated approximately 90 degrees sideways and the stimulus was given facing backwards (i.e. head rotated ipsilaterally to stimulated ear) the postural sway was in a backward direction. The mean values (mm) of body sway obtained with the head facing forwards and the eyes closed were higher than those with the eyes open (21.7 and 22.8 vs 15.7 and 14.7 for the right and left ears, respectively); higher mean values were obtained with the head turned to the side contralateral to the ear stimulated and the eyes closed (29.3 and 24.8 for the right and left ears, respectively). Under this condition the body sway was mainly in a forward direction. The sound-evoked vestibulopostural reflex seems to be a useful test for exploring the saccular function and, as a click-evoked vestibulocollic reflex, can be considered a physiological Tullio phenomenon.

Acoustic Stimulation↗
PubMed2005

The development and validation of equations to predict grip force in the workplace: contributions of muscle activity and posture.

The inherent difficulty of measuring forces on the hand in ergonomic workplace assessments has led to the need for equations to predict grip force. A family of equations was developed, and validated, for the prediction of grip force using forearm electromyography (six finger and wrist muscles) as well as posture of the wrist (flexed, neutral and extended) and forearm (pronated, neutral, supinated). Inclusion of muscle activity was necessary to explain over 85% of the grip force variance and was further improved with wrist posture but not forearm posture. Posture itself had little predictive power without muscle activity (<1%). Nominal wrist posture improved predictive power more than the measured wrist angle. Inclusion of baseline muscle activity, the activity required to simply hold the grip dynamometer, greatly improved grip force predictions, especially at low force levels. While the complete model using six muscles and posture was the most accurate, the detailed validation and error analysis revealed that equations based on fewer components often resulted in a negligible reduction in predictive strength. Error was typically less than 10% under 50% of maximal grip force and around 15% over 50% of maximal grip force. This study presents detailed error analyses to both improve upon previous studies and to allow an educated decision to be made on which muscles to monitor depending on expected force levels, costs and error deemed acceptable by the potential user.

Ergonomics↗