The Effects of Breath Control on Intra-Abdominal Pressure During Lifting Tasks

ArticleinSpine 29(4):464-9 · February 2004with 966 Reads 
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Abstract
This was a repeated measures study examining 11 asymptomatic subjects while performing dynamic lifting using various postures, loads, and breath control methods. To examine the effects of breath control on magnitude and timing of intra-abdominal pressure during dynamic lifting. Intra-abdominal pressure has been shown to increase consistently during static and dynamic lifting tasks. The relationship between breath control and intra-abdominal pressure during lifting is not clear. Eleven healthy subjects were tested using lifting trials consisting of two levels of posture and load and four levels of breath control (natural breathing, inhalation-hold, exhalation-hold, inhalation-exhalation). Intra-abdominal pressure was measured using a microtip pressure transducer placed within the stomach through the nose. Timing of intra-abdominal pressure was determined relative to lift-off of the weights. Repeated measures analysis of variance was used to determine the effect of breath control, posture, and load on intra-abdominal pressure magnitude and timing. There was a significant effect of breath control (P < 0.018) and load (P < 0.002), but not of posture (P < 0.434), on intra-abdominal pressure magnitude. The inhalation-hold form of breath control produced significantly greater peak intra-abdominal pressure than all other forms of breath control (P < 0.000 for all comparisons). No other comparisons among levels of breath were significantly different. No significant main effects of breath control were found relative to intra-abdominal pressure timing. Breath control is a significant factor in the generation of intra-abdominal pressure magnitude during lifting tasks. The effects of respiration should be controlled in studies analyzing intra-abdominal pressure during lifting.

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  • ... MAINTENANCE OF UPRIGHT POSTURE involves complex neuromotor processes. Although research related to postural control of the trunk has largely focused on the role of abdominal and erector spinae (ES) muscles (24,33), control of pressures in the thoracic and abdominal cavities make an important contribution (14,17). Recent research has highlighted the role of other muscles that influence intrathoracic (ITP) and intraabdominal (IAP) pressures such as the diaphragm (1,6,20,49), intercostal (2,26,38), and pelvic floor muscles (25,39,44,47,48). ...
    ... ITP depends not only on activation of the thoracic muscles, but also on regulation of airflow resistance (40). The glottis modulates airway opening, supporting the airway and ITP for tasks such as talking, coughing, and breathing, yet glottal control is rarely reported in relation to postural control (14,32,34,35,40). Although postural control is commonly evaluated by investigation of the recovery of balance after a perturbation, most work has focused on glottal control during high-level postural demands such as weight lifting (7,12,17,37,40). ...
    ... These alternatives require further investigation. Considering the thoracic and CoP displacement findings together, a breath-holding strategy would appear to be effective for ensuring the stability of the thorax, hence the logic for use of breath-holding when the primary demand is thoracic stability such as lifting a heavy object (14) or pushing a heavy door. However, it would appear that to optimize dynamic control of CoP, a mid-range glottal control technique such as talking may be more effective. ...
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    Maintenance of upright posture involves complex neuromotor processes that include control of thoracic and abdominal pressures. Control of airflow by glottal structures is a primary determinant of thoracic pressure and may have a role in control of postural stability. This study aimed to investigate the effect of modulation of airway control on upright postural stability during postural perturbations. Standing balance was gently perturbed in the sagittal plane during 7 breathing/voicing tasks that ranged from completely closed (breath-hold), to partially opened (voicing) or completely open (sigh) glottal conditions in 11 healthy adults. Dependent measures were peak amplitude of displacement of the thorax and center of pressure (CoP). When the glottis was completely open during sigh, thoracic displacement in response to the perturbation was greater than in all other conditions, regardless of direction of perturbation (Post hoc:all P<0.002). The absolute amplitude of CoP displacement was greater with backward perturbation (Main effect-Direction:P=0.001) and was greater at both extremes of glottal modulation (glottis closed and completely open) than when the glottis was partially opened during counting out loud (Post hoc: all P<0.04). These results show that airway modulation affects postural control during upright perturbations. The thorax was more stable when the glottis was engaged than when it was required to remain open whereas control of CoP displacement appeared more optimal during the natural dynamic mid-range airway modulation of voicing. These data suggest glottal control influences balance, and that glottal control strategies may be an important consideration for patients with breathing and/or balance disorders.
  • ... The increased variability in IAP from the VM may be attributed to lung volumes and abdominal muscle strength. Greater lung volumes before the closing of the glottis have been shown to increase IAP resulting from the descending diaphragm acting on the relatively incompressible abdominal contents (19,20). Furthermore, contraction of the abdominal muscle, as occurs with the VM, markedly increases the IAP (11,12). ...
    ... The increased IAP offered by the VM can be thought of as the body's natural response to establish spine stability (8,28). The VM pressurizes the abdominal cavity through a combination of diaphragm and abdominal and pelvic floor muscle activity (11,12,18,20). Spine stability is important during exercises requiring high axial loading and may explain why peak IAP was greatest for leg exercises such as squats, dead lifts, and leg press (compared with upper body exercises, including bench press and arm curls). ...
    ... However, despite the VM augmenting IAP during resistance exercises, this review has shown that IAP generated seems to be lower Valsalva Maneuver during Resistance Exercise than IAP generated from the VM alone. This may be attributed to the postures in which the resistance exercises were performed (18) or to the lower inspiratory volumes during the exercises (19,20,28). Males and resistance trained subjects were also shown to have a lower IAP relative to that achieved through a VM alone compared with females and untrained subjects during exercises at the same percentage of MVC (14,28). ...
    Article
    During resistance exercise, a brief Valsalva maneuver (VM) is unavoidable when lifting heavy loads (>80% of maximal voluntary contraction) or when lifting lighter loads to failure. It has been proposed that the performance of the VM during resistance exercise increases the stability of the spine due to augmented intra-abdominal pressure (IAP). However, resistance trainers are often advised to avoid the VM during resistance exercise due to potential adverse vascular events. The aim of this review was to establish the effect of the VM on IAP and to evaluate if the VM during resistance exercise is a safe practice. Relevant databases were searched to examine the effect of the VM on: 1) IAP; and 2) hemodynamics during resistance exercise and reported adverse events. The data show that the VM alone increases IAP and that the VM augment IAP during various resistance exercises. An incremental rise in IAP was observed as the lifting intensity and effort increased, with IAP tending to be lower compared with peak IAP from the VM alone. The VM was associated with an increase in blood pressure during resistance exercise, but the VM alone was associated with greater haemodynamic changes. In conclusion, the VM effectively increases IAP, which may assist with spine stability and trunk rigidity during resistance exercise. The health risks associated with the VM during resistance exercise remain unconfirmed.
  • ... Pressures recorded in our subjects during coughing are similar to those routinely obtained during urodynamic studies 11 and are also generally similar to those recorded using different technologies in studies on lifting and spine dynamics. [12][13][14][15] A study of 12 women undergoing laparoscopy revealed that measuring rectal pressure at a depth greater than 10 cm accurately reflected changes in intra-abdominal pressure. 16 Of note, although each activity had a fairly consistent effect on intra-abdominal pressures and baseline measurements remained relatively stable during data collection, we observed high levels of intersubject variability. ...
    ... Current thinking in that field holds that increased intra-abdominal pressure serves a protective role by increasing lumbar stability by forming a "rigid cylinder" of the abdominal musculature and stabilizing fascial connections to the vertebra. 15 Similarly, current thinking about physical activity after hernia surgery is changing. Recent large-scale data from the Danish Hernia Database have not demonstrated more recurrences in people who quickly resumed activities after surgery compared with those with more traditional convalescence periods. ...
    Article
    Because of a widespread but untested belief that increased intra-abdominal pressure contributes to pelvic floor disorders, physicians commonly restrict various activities postoperatively. Our aim was to describe intra-abdominal pressures during common physical activities. Thirty women of wide age and weight ranges who were not undergoing treatment for pelvic floor disorders performed 3 repetitions of various activities while intra-abdominal pressures (baseline and maximal) were approximated via microtip rectal catheters. We calculated median peak and net pressures (centimeters of H(2)O). We assessed correlations between abdominal pressures and body mass index, abdominal circumference, and grip strength (a proxy for overall strength). P < .025 was considered significant. Median peak abdominal pressures ranged from 48 (lifting 8 lb from a counter) to 150 (lifting 35 lb from the floor), with much variation. Many activities did not raise the intra-abdominal pressure more than simply getting out of a chair, including lifting 8, 13, and 20 lb from a counter, lifting 8 or 13 lb from the floor, climbing stairs, walking briskly, or doing abdominal crunches. Body mass index and abdominal circumference each correlated positively with peak, but not net, pressures. Age and grip strength were not associated with abdominal pressure. Some activities commonly restricted postoperatively have no greater effect on intra-abdominal pressures than unavoidable activities like rising from a chair. How lifting is done impacts intra-abdominal pressure. Many current postoperative guidelines are needlessly restrictive. Further research is needed to determine whether increased intra-abdominal pressure truly promotes pelvic floor disorders. III.
  • ... Intra-abdominal pressure has been shown to increase consistently during both static and dynamic lifting tasks. 34 Breath control is a significant factor in the generation of intra-abdominal pressure magnitude during lifting tasks. 34 IOP increases significantly during a bench press exercise and to a greater extent with breath holding. ...
    ... 34 Breath control is a significant factor in the generation of intra-abdominal pressure magnitude during lifting tasks. 34 IOP increases significantly during a bench press exercise and to a greater extent with breath holding. 35 ...
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    Dry eye syndromes can involve both nociceptive and neuropathic symptoms. Nociceptive symptoms are the normal physiological responses to noxious stimuli. Neuropathic symptoms are caused by a lesion or disease of the somatosensory nervous system and can be the result of hypersensitisation of peripheral or central corneal and conjunctival somatosensory nerves. For example, inflammation could induce neuroplastic peripheral sensitisation of the ocular surface or lid wiper and exacerbate nociceptive symptoms. Neuropathic symptoms may explain the incommensurate relation between signs and symptoms in some dry eye syndromes although absence of signs of a dry eye syndrome may also be a consequence of inappropriate methods used when examining for them. Involvement of neuropathic mechanisms may also help explain dry eye symptoms which occur in association with reduced corneal sensitivity. This review includes a discussion of the potential for ocular symptoms involving neuropathic mechanisms to contribute to psychosocial problems such as depression, stress, anxiety and sleep disorders as well as for these types of psychosocial problems to contribute to neuropathic mechanisms and dry eye syndromes. Failure to consider the possibility that neuropathic mechanisms can contribute to dry eye syndromes may reduce accuracy of diagnosis and the suitability of treatment provided. Dry eye symptoms in the absence of commensurate evidence of tear dysfunction, and unsatisfactory response to tear dysfunction therapies should prompt consideration of neuropathic mechanisms being involved. Symptoms which persist after local anaesthetic instillation are more likely to be neuropathic in origin. Reducing inflammation may help limit any associated neuroplastic hypersensitivity.
  • ... Intra-abdominal pressure has been shown to increase consistently during both static and dynamic lifting tasks. 34 Breath control is a significant factor in the generation of intra-abdominal pressure magnitude during lifting tasks. 34 IOP increases significantly during a bench press exercise and to a greater extent with breath holding. ...
    ... 34 Breath control is a significant factor in the generation of intra-abdominal pressure magnitude during lifting tasks. 34 IOP increases significantly during a bench press exercise and to a greater extent with breath holding. 35 ...
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    Intraocular pressure may become elevated with muscle exertion, changes in body position and increased respiratory volumes, especially when Valsalva manoeuver mechanisms are involved. All of these factors may be present during physical exercise, especially if hydration levels are increased. This review examines the evidence for intraocular pressure changes during and after physical exercise. Intraocular pressure elevation may result in a reduction in ocular perfusion pressure with the associated possibility of mechanical and/or ischaemic damage to the optic nerve head. A key consideration is the possibility that, rather than being beneficial for patients who are susceptible to glaucomatous pathology, any intraocular pressure elevation could be detrimental. Lower intraocular pressure after exercise may result from its elevation causing accelerated aqueous outflow during exercise. Also examined is the possibility that people who have lower frailty are more likely to exercise as well as less likely to have or develop glaucoma. Consequently, lower prevalence of glaucoma would be expected among people who exercise. The evidence base for this topic is deficient and would be greatly improved by the availability of tonometry assessment during dynamic exercise, more studies which control for hydration levels, and methods for assessing the potential general health benefits of exercise against any possibility of exacerbated glaucomatous pathology for individual patients who are susceptible to such changes.
  • ... Some of the intra-abdominal pressures during activities we tested have been described previously; our results fit in the range of others (Cobb et al., 2005;Essendrop, Hye-Knudsen, Skotte, Hansen, & Schibye, 2004;Gerten et al., 2008;Guttormson et al., 2008;Hagins, Pietrek, Sheikhzadeh, Nordin, & Axen, 2004;Weir et al., 2006), though it is important to note that the variability in intra-abdominal pressure between different studies is large and due in part to the variety of methods used for collecting intra-abdominal pressure as well as to multiple methods for calculating maximal pressure. Of greater clinical interest is the wide range of intraabdominal pressures we found amongst different women doing the same activity. ...
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    Abstract Strenuous physical activity has been linked to pelvic floor disorders in women. Using a novel wireless intra-vaginal pressure transducer, intra-abdominal pressure was measured during diverse activities in a laboratory. Fifty-seven women performed a prescribed protocol using the intra-vaginal pressure transducer. We calculated maximal, area under the curve and first moment of the area intra-abdominal pressure for each activity. Planned comparisons of pressure were made between levels of walking and cycling and between activities with reported high pressure in the literature. Findings indicate variability in intra-abdominal pressure amongst individuals doing the same activity, especially in activities that required regulation of effort. There were statistically significant differences in maximal pressure between levels of walking, cycling and high pressure activities. Results for area under the curve and first moment of the area were not always consistent with maximal pressure. Coughing had the highest maximal pressure, but had lower area under the curve and first moment of the area compared to most activities. Our data reflect novel findings of maximal, area under the curve and first moment of the area measures of intra-abdominal pressure, which may have clinical relevance for how physical activity relates to pelvic floor dysfunction.
  • ... Exhalation with exertion has been recommended to decrease pelvic pressure. This instruction did not consis- tently lead to decrease in pressure with lifting and repeated exercise, corroborating a previous study [24]. ...
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    We recorded vaginal pressure in 12 women without risk factors for prolapse during two activity and exercise sessions, compared exercise and cough pressure, and evaluated method reproducibility and patterns of relative pressure. Portable urodynamic equipment, repeated measures descriptive design, and purposeful sampling were used with nonparametric analysis and visual comparison of pressure graphs. Mean participant age was 31.1 years (range 20-51), and mean body mass index was 22.7 (range 18.5-29.3). Mean pressures (in cm H(2)O): cough, 98.0 (48.0-133.7); standing, 24.0 (15.9-28.5); supine exercise, 34.0 (6.3-91.9); exercise machines, 37.0 (20.3-182.3). Repeated measures correlations for selected measures ranged from 0.66 (p <or= 0.05) to 0.91 (p <or= 0.01), and median within-woman coefficients of variation ranged from 3.8% to 7.2%. Individual pressure patterns were not consistent with patterns of group medians. We concluded that vaginal pressure measurement is reproducible in women without prolapse and that studied exercises generally produced lower pressure than cough, but individuals varied in pressure exerted. Individual variations warrant further study.
  • ... 1,2 During lifting, the intraabdominal pressure (IAP) is increased. [3][4][5][6][7] The peak pressure rises both when the lifting speed and when the lifting force are increased. 8 -11 It has been shown that IAP enhances trunk stiffness 12 and spine stability. ...
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    An in vivo study on weightlifters. To determine if and how a stiff back belt affects spinal compression forces in weightlifting. In weightlifting, a back belt has been reported to enhance intraabdominal pressure (IAP) and to reduce back muscle EMG and spinal compression forces. Nine experienced weightlifters lifted barbells up to 75% body weight while inhaling and wearing a belt, inhaling and not wearing a belt, and exhaling and wearing a belt. IAP, trunk muscle EMG, ground reaction forces, and kinematics were measured. An EMG-assisted trunk model, including IAP effects, was used to calculate spinal compression and shear forces and to reveal the contribution of back muscles, abdominal muscles, and IAP to moment generation. The belt reduced compression forces by about 10%, but only when inhaling before lifting. The moment generated by IAP increased when wearing a belt and inhaling, but this moment was small and the increase was largely negated by the flexing moment generated by abdominal muscles. Wearing a tight and stiff back belt while inhaling before lifting reduces spine loading. This is caused by a moment generated by the belt rather than by the IAP.
  • ... The prevention, treatment, and rehabilitation programs would subsequently benefit from such improved knowledge. One parameter with the potential to influence spinal mechanics and stability is intra-abdominal pressure (IAP) that has been reported to increase during static and dynamics lifting tasks [1,5,24,27,34,45,46,52,54]. For years, it has been argued that an increase in IAP could unload the spine both directly by pressing upwards on the rib cage via diaphragm and indirectly by generating an extensor moment on the lumbar spine that decreases the back-muscle activities [5, 20-22, 31, 36-38, 41, 54]. ...
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    The role of intra-abdominal pressure (IAP) in unloading the spine has remained controversial. In the current study, a novel kinematics-based approach along with a nonlinear finite-element model were iteratively used to calculate muscle forces, spinal loads, and stability margin under prescribed postures and loads measured in in vivo studies. Four coactivity levels (none, low, moderate, and high) of abdominal muscles (rectus abdominis, external oblique, and internal oblique) were considered concurrently with a raise in IAP from 0 to 4 kPa when lifting a load of 180 N in upright standing posture and to 9 kPa when lifting the same load in forward trunk flexions of 40 degrees and 65 degrees. For comparison, reference cases with neither abdominal coactivity nor IAP were investigated as well. A raise in IAP unloaded and stabilized the spine when no coactivity was considered in the foregoing abdominal muscles for all lifting tasks regardless of the posture considered. In the upright standing posture, the unloading action of IAP faded away even in the presence of low level of abdominal coactivity while its stabilizing action continued to improve as abdominal coactivity increased to moderate and high levels. For lifting in forward-flexed postures, the unloading action of IAP disappeared only with high level of abdominal coactivities while its stabilizing action deteriorated as abdominal coactivities increased. The unloading and stabilizing actions of IAP, hence, appear to be posture and task specific.
  • ... Advice regarding how to breathe during the task has not been included in standard lifting recommendations to date. This is true despite clear evidence that voluntary breath control influences intra-abdominal pressure (IAP) (McGill et al. 1990, Cresswell et al. 1992, Cresswell et al. 1994, Goldish et al. 1994, Hagins et al. 2004) and that IAP has been shown, both indirectly (McGill et al. 1990, Cholewicki et al. 1999, Essendrop et al. 2002, Hodges et al. 2004) and directly (McGill et al. 1994, Cholewicki et al. 1999, Shirley et al. 2003), to influence lumbar stability. Indirect measures in these studies included computer modelling and the measurement of trunk oscillations or trunk resistance in response to perturbation while direct measures included measures of applied force and displacement of individual segments ...
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    Clear evidence links voluntary breath control, intra-abdominal pressure and lumbar stability. However, little is known regarding optimal breath control during manual materials handling. No studies have examined natural breath control while lifting a maximal load. Fourteen healthy subjects lifted a loaded crate from the floor to a table while respiratory flow data were collected. The loads lifted began at 10% of body weight and increased up to 50% (if tolerated) by 5% increments. Data from the minimum, moderate and maximum loads were analysed. Uniform and consistent breath holding during lifting of a maximally tolerated load did not occur. Across all three loads, frequency of inspiration was highest immediately prior to lift-off and significantly higher inspired volume occurred at lift-off of the load compared with preparation for lifting. Holding the breath does not appear to be related to lifting of a maximally tolerated load from floor to table. STATEMENT OF RELEVANCE: The findings demonstrate that consistent patterns of naturally occurring breath control during lifting of a maximal load can be identified and do not include uniform breath holding. The findings may assist in creating models for optimal breath control, which will minimise risk of injury during manual material handling tasks.
  • ... The bulging of the rectus abdominis muscle during agonal PUE may further accentuate weak points within the rectus sheath, such as the site of emissary vessels. The increased abdominal pressure caused by the increased intensity/effort during isometric contractions (Harman et al., 1988;Hagins et al., 2004;Kawabata et al., 2010) provides additional opportunity for herniation. In humans, the inhalation form of breath control has been shown to produce greater intraabdominal pressure than other forms of breath hold (Hagins FIGURE 8 | Acute abdominal hernias in a bycaught bottlenose dolphin (with the peritoneum reflected back). ...
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    Peracute underwater entrapment (PUE) is a recognized cause of death associated with anthropogenic trauma in marine mammals. We describe internal lesions likely resulting from extreme agonal exertion in bottlenose dolphins due to entanglement and forced submergence in fishing gear during PUE. We reviewed necropsy findings from bottlenose dolphins with known PUE statuses in Virginia, United States from 2016–2019 (n = 31) for the presence of five lesions: pulmonary petechiae, pulmonary perivascular edema, hemorrhagic pulmonary lymph, separation of the rectus abdominis muscles, and acute abdominal hernias. Of the 31 cases, 23 were considered PUE cases due to the presence of external ligature marks consistent with entanglement in fishing gear. Of the animals examined, pulmonary perivascular edema, pulmonary petechiae, and hemorrhagic pulmonary lymph were found in both PUE and non-PUE cases. Though found in one non-PUE case, pulmonary perivascular edema was significantly related to PUE. There was no significant relationship between PUE and pulmonary petechiae or hemorrhagic pulmonary lymph. Rectus abdominis muscle separations and acute abdominal hernias were only found in PUE cases and nine animals exhibited either one (n = 7) or both (n = 2) of these traumatic lesions. Although these two lesions were relatively rare, there was a statistically significant relationship between the presence of one or both of the lesions and positive PUE status. This study suggests that pulmonary perivascular edema, acute hernias and separations of the rectus abdominis muscles may be useful for diagnosing PUE in the absence of external fishery interaction lesions, and highlights the severity of agonal fisheries interactions.
  • ... The diaphragm and expiratory muscles contribute to increases in IAP via the VM (Cresswell et al., 1992;Goldish et al., 1994;Nachemson et al., 1986). Breath hold (BH) also produces a similar effect (Hagins et al., 2004;Hagins et al., 2006). It was identified that the subjects in this study performed the VM or BH as they approached repetition failure, during the execution of lifts within the later sets of the high volume session. ...
    Article
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    This study investigated the effect of a high-volume compared to a low-volume resistance training session on maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP). Twenty male subjects with resistance training experience (6.2 ± 3.2 y), in a crossover trial, completed two resistance training protocols (high-volume: 5 sets per exercise; low-volume: 2 sets per exercise) and a control session (no exercise) on 3 separate occasions. MIP and MEP decreased by 13.6% (p < 0.01) and 14.7% (p < 0.01) respectively from pre-session MIP and MEP, following the high-volume session. MIP and MEP were unaffected following the low-volume or the control sessions. MIP returned to pre-session values after 40 minutes, whereas MEP remained significantly reduced after 60 minutes post-session by 9.2% compared to pre-session (p < 0.01). The findings suggest that the high-volume session significantly decreased MIP and MEP post-session, implicating a substantially increased demand on the respiratory muscles and that adequate recovery is mandatory following this mode of training. Key pointsRespiratory muscular strength performance is acutely diminished following a high-volume whole-body resistance training session.Greater ventilatory requirements and generation of IAP during the high-volume resistance training session may have contributed to the increased demand placed on the respiratory muscles.Protracted return of respiratory muscular strength performance to baseline levels may have implications for individuals prior to engaging in subsequent exercise bouts.
  • ... Spinal stiffness also changes throughout the breathing cycle due to fluctuating IAP and trunk muscle activity (Shirley et al., 2003). Holding the breath at the end of inspiration during loading generates higher levels of IAP and spinal stiffness (Hagins et al., 2004(Hagins et al., , 2006. However a regular breathing pattern under loading conditions results in 'more optimal' IAP levels reducing the risk of undue spinal compression (Beales et al., 2010b). ...
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  • ... Identify the deterministic model based on principles of engineering mechanics. The lifting model described by Chaffin was selected for implementation (it is described above and presented in more detail in [3,7]), but the effect of intra-abdominal pressure was not included because its effectiveness depends on breath control [9]. 2. ...
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    Background: Biomechanists are often asked to provide expert opinions in legal proceedings, especially personal injury cases. This often involves using deterministic analysis methods, although the expert is expected to opine using a civil standard of “more likely than not” that is inherently probabilistic. Methods: A method is proposed for converting a class of deterministic biomechanical models into hybrid Bayesian networks that produce a probability well suited for addressing the civil standard of proof. The method was developed for spinal injury during lifting. Its generalizability was assessed by applying it to slip and fall events based on the coefficients of friction at the shoe–floor interface. Results: The proposed method is shown to be generalizable beyond lifting by applying it to a slip and fall event. Both the lifting and slip and fall models showed that incorporating evidence of injury could change the probabilities of critical quantities exceeding a threshold from “less likely than not” to “more likely than not.” Conclusions: The present work shows that it is possible to develop Bayesian networks for legal use based on laws of engineering mechanics and probabilistic descriptions of measurement error and human variability.
  • ... The diaphragm contraction intensity is proportional to the lung volume (i.e., depth of inspiration) (Depalo et al. 2004;Hodges et al. 2001) and plays a significant role in producing high IAP. Indeed, IAP has been shown to vary with breathing state and lung volume (Hagins et al. 2004;Kawabata et al. 2010;McGill et al. 1990;Miyamoto et al. 1999). Therefore, to test the aforementioned hypothesis, we investigated IAP and torque during hip extension and flexion MVC tasks in three different breath-hold conditions. ...
    Article
    Purpose: Intra-abdominal pressure (IAP) has been recently shown to be associated specifically with maximal voluntary isometric contraction (MVC) torque of hip extension, although the causal relationship remains unclear. The present study aimed to elucidate whether IAP has a causal effect on hip extension MVC torque. Methods: IAP during hip extension MVC was changed by controlling the lung volume (i.e., depth of inspiration). Twelve healthy males conducted MVCs of hip extension during breath-hold at full inspiration (inspiratory condition) or expiration (expiratory condition), or during normal breath-hold (normal condition). IAP during MVCs was measured a pressure transducer placed in the rectum. Results: The IAP during hip extension MVC was significantly higher in inspiratory condition (132.0 ± 46.1 mmHg) than in the other two conditions and also higher in normal condition (104.6 ± 35.9 mmHg) than in expiratory condition (77.0 ± 39.1 mmHg). The hip extension MVC torque was significantly higher in inspiratory condition (297.7 ± 82.7 N m) than in expiratory condition (266.4 ± 84.5 N m). In each condition, the hip extension MVC torque correlated with IAP during the MVC task. Conclusion: The current results suggest that IAP has a positive causal effect on hip extension MVC torque and that a sufficient increase in IAP directly leads to an enhancement of hip extension MVC torque.
  • ... There is limited research investigating the role of glottis as intra-abdominal pressure and intra-thoracic pressure regulator [36,37], or in the quality of postural control/balance [38]. ...
  • ... Belts made of both leather and synthetic material are commercially available. Lifting in general increases the intraabdominal pressure (IAP) (12,24,30,46). As the force needed to lift the weight increases, the IAP also increases (10,23,31,40) and is therefore a good indicator of forces on the spine (33,35). ...
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  • ... Quantifying the contribution of the active and passive components of the human trunk during various daily, occupational, or athletic activities is essential for the design of effective spinal fixation systems, and would greatly benefit research and clinical stakeholders in the field of spinal biomechanics. Intra-abdominal pressure (IAP), considered as the most likely factor to influence lumbar spinal mechanics, has been continuously investigated under static and dynamic lifting conditions for many decades now (Davis, 1956;Bartelink, 1957;Davis and Troup, 1964;Andersson et al., 1976;McGill et al., 1990;Marras and Mirka, 1996;Hagins et al., 2004). Most of the existing studies advocate that the IAP produces an extensor torque (Bartelink, 1957;Morris et al., 1961), which reduces the spinal loads and back muscle activity, hence influencing the overall loading scenarios and stability of the lumbar spine Thorstensson, 1997, 2003;Cholewicki and Reeves, 2004). ...
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    The intra-abdominal pressure (IAP), which generates extensor torque and unloads the spine, is often neglected in most of the numerical studies that use musculoskeletal (MSK) or finite element (FE) spine models. Hence, the spinal loads predicted by these models may not be realistic. In this work, we quantified the effects of IAP variation in forward flexion on spinal loads and load-sharing using a novel computational tool that combines a MSK model of the trunk with a FE model of the ligamentous lumbosacral spine. The MSK model predicted the trunk muscle and reaction forces at the T12-L1 junction, with or without the IAP, which served as input in the FE model to investigate the effects of IAP on spinal loads and load-sharing. The findings confirm the unloading role of the IAP, especially at large flexion angles. Inclusion of the IAP reduced global muscle forces and disc loads, as well as the intradiscal pressure (IDP). The reduction in disc loads was compensated for by an increase in ligament forces. The IDP, as well as the strain of the annular fibers were more sensitive to the IAP at the upper levels of the spine. Including the IAP also increased the ligaments' load-sharing which reduced the role of the disc in resisting internal forces. These results are valuable for more accurate spinal computational studies, particularly toward clinical applications as well as the design of disc implants.
  • ... However, the Valsalva maneuver elevates blood pressure and increases the load on the heart. Hence, it is difficult to use in subjects with cardiovascular system disease 11) . Moreover, an accurate method and mechanism is yet to be clarified, and the specific impact on the limbs is still unclear 12,13) . ...
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    [Purpose] Maximum voluntary isometric contraction can increase the reliability of electromyography data by controlling respiration; however, many studies that use normalization of electromyography data fail to account for this. This study aims to check changes in maximum voluntary isometric contraction based on changes in posture and respiration conditions. [Subjects and Methods] Twenty-two healthy volunteers were included in this study. Using 22 healthy subjects, MVIC of the biceps brachii muscle was measured in three respiration conditions: (1) Maximum voluntary isometric contraction during inspiration after maximal expiration, (2) Maximum voluntary isometric contraction during expiration after maximal inspiration and (3) Maximum voluntary isometric contraction during the Valsalva maneuver. The subjects were in tested in standing and supine postures under all three respiration conditions. [Results] A significant difference was observed in the standing and supine postures based on the respiration condition. A significant difference was observed in the maximum voluntary isometric contraction during inspiration after maximal expiration and maximum voluntary isometric contraction during the Valsalva maneuver conditions when the subjects were in the supine posture. [Conclusion] It is necessary to apply the same respiration condition and the same posture to each subject when measuring Maximum voluntary isometric contraction for the normalization of electromyography data.
  • ... In addition, maximal IAPs vary across studies for the same activity, in part related to the instrumentation with which IAP is measured and how maximal IAP is constructed, as well as to differences between populations [27,28]. Breathing pattern is generally not standardized, which can also influence IAP [29]. IAPs across studies also vary because both total (that is, maximal IAP from atmospheric pressure baseline) and net (difference between maximal IAP and a baseline value, usually standing) are used to operationalize IAP but usually not specified in reports. ...
    Article
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    More women participate in sports than ever before and the proportion of women athletes at the Olympic Games is nearly 50%. The pelvic floor in women may be the only area of the body where the positive effect of physical activity has been questioned. The aim of this narrative review is to present two widely held opposing hypotheses on the effect of general exercise on the pelvic floor and to discuss the evidence for each. Hypothesis 1: by strengthening the pelvic floor muscles (PFM) and decreasing the levator hiatus, exercise decreases the risk of urinary incontinence, anal incontinence and pelvic organ prolapse, but negatively affects the ease and safety of childbirth. Hypothesis 2: by overloading and stretching the PFM, exercise not only increases the risk of these disorders, but also makes labor and childbirth easier, as the PFM do not obstruct the exit of the fetus. Key findings of this review endorse aspects of both hypotheses. Exercising women generally have similar or stronger PFM strength and larger levator ani muscles than non-exercising women, but this does not seem to have a greater risk of obstructed labor or childbirth. Additionally, women that specifically train their PFM while pregnant are not more likely to have outcomes associated with obstructed labor. Mild-to-moderate physical activity, such as walking, decreases the risk of urinary incontinence but female athletes are about three times more likely to have urinary incontinence compared to controls. There is some evidence that strenuous exercise may cause and worsen pelvic organ prolapse, but data are inconsistent. Both intra-abdominal pressure associated with exercise and PFM strength vary between activities and between women; thus the threshold for optimal or negative effects on the pelvic floor almost certainly differs from person to person. Our review highlights many knowledge gaps that need to be understood to understand the full effects of strenuous and non-strenuous activities on pelvic floor health.
  • ... In healthy nonpregnant adults, breath control, although not posture, affected IAP during dynamic weight lifting. 30 It is possible that childbirth may reset the factors that lead to variability in IAP; that is, the muscles and connective tissues that are altered as a result of childbirth at 6 to 10 weeks postpartum may not be representative of a "normal" physiological state, leading to different relationships between IAP and factors analyzed than might be seen in other populations. Indeed, the muscles and connective tissue of the abdomen, back, and pelvic floor that are recovering after childbirth are precisely the structures that are recruited to increase IAP for postural bracing. ...
    Article
    Objectives: Intra-abdominal pressure (IAP) may contribute to pelvic floor health, although the direction and magnitude of such an effect, if any, are not yet known. Identifying individual characteristics, and in particular modifiable factors, associated with higher IAP during recovery from vaginal childbirth might serve to mitigate early pelvic floor dysfunction. The aim of this study was to identify characteristics associated with maximal IAP during lifting in postpartum primiparous women who delivered vaginally. Methods: At 6 to 10 weeks postpartum, we measured maximal IAP, assessed via an upper vaginal sensor, as participants (enrolled in an ongoing cohort study) lifted a weighted car seat (12.5 kg). We evaluated whether the following independent variables were associated with maximal IAP: age, ethnicity, body mass index, height, abdominal circumference, weight gain during pregnancy, lifting time, breath holding during lifting, lifting technique, measures of muscular fitness, and days since delivery. Results: In the 206 participants, weight, waist circumference, body mass index, and days since delivery were positively associated with mean maximal IAP during lifting, whereas IAP decreased as height increased. As the duration of the lifting task increased, mean maximal IAP during lifting also increased, but there were no associations between lifting technique or breath holding during lifting and IAP. Neither pelvic floor muscle strength nor abdominal muscle endurance was associated with IAP during lifting. Conclusions: Other than measures of body habitus and lifting duration, we did not identify modifiable factors that could mitigate maximal pressures experienced by the pelvic floor during the early postpartum period.
  • ... However, it is possible that women used different strategies during the trunk flexor test in early versus later postpartum. Though breathing patterns were not assessed, a natural, dynamic breathing pattern during exertion results in lower IAP response in comparison to breath holding or forceful expiration even during strenuous activity (Hagins et al., 2004). In the context of the present study, IAP does not seem to explain how women improve trunk flexor endurance from early to later postpartum. ...
    Article
    Objectives: To describe change in trunk flexor endurance and intra-abdominal pressure (IAP) associated with trunk flexor assessment and explore factors associated with change in trunk flexor endurance during the first postpartum year. Design: Ancillary analysis of an ongoing prospective cohort study. Methods: Participants (N = 282) were primiparous women delivered vaginally. They completed trunk flexor endurance testing while assessing IAP, body habitus measures (body mass index, waist circumference, and body composition), and questionnaires 5–10 weeks and 11–15 months postpartum. We investigated change in trunk flexor endurance by quartile of improvement and factors associated with improvement (Q4 vs. Q1-Q3) using multivariable models, adjusted for baseline endurance. Results: Mean age was 28 ± 5 years. The median (IQR) trunk flexor hold time increased from early to late postpartum (129/IQR = 68, 217 vs 148/IQR = 80, 265 seconds, p = .01) and mean (SD) IAP decreased (55/SD = 13 vs 48/SD = 14 cmH20, p < .0001). The most improved group (Q4) increased endurance time by 176 seconds (95% CI = 103, 254), were less likely to be Hispanic, more likely to be older, more educated, and have lower measures of body habitus than women in Q1-Q3. Conclusion: Trunk flexor endurance increased and IAP decreased over one year postpartum. Lower body habitus and higher age early postpartum predicted greatest improvement in trunk flexor endurance at 1 year.
  • ... The exercise activities were not randomized, but rather reflected the standard Pilates routine where the early activities gradually warm the participant up before engaging in the more strenuous activities. Breath control, which has been shown to contribute to the magnitude of peak IAP, was cued during the exercise by the movement practitioner [29]. However, the synchronization of movement and breath was not verified and is a likely contributor to IAP variability. ...
    Article
    Full-text available
    The objective was to describe the intra-abdominal pressures (IAP) generated during Pilates Mat and Reformer activities, and determine whether these activities generate IAP above a sit-to-stand threshold. Twenty healthy women with no symptomatic vaginal bulge, median age 43 (range 22-59 years), completed Pilates Mat and Reformer exercise routines each consisting of 11 exercises. IAP was collected by an intra-vaginal pressure transducer, transmitted wirelessly to a base station, and analyzed for maximal and area under the curve (AUC) IAP. There were no statistically significant differences in the mean maximal IAP between sit-to-stand and any of the Mat or Reformer exercises in the study population. Six to twenty-five percent of participants exceeded their individual mean maximal IAP sit-to-stand thresholds for 10 of the 22 exercises. When measuring AUC from 0 cm H2O, half the exercises exceeded the mean AUC of sit-to-stand, but only Pilates Reformer and Mat roll-ups exceeded the mean AUC of sit-to-stand when calculated from a threshold of 40 cm H2O (consistent with, for example, walking). Our results support recommending this series of introductory Pilates exercises, including five Mat exercises and six Reformer exercises to women desiring a low IAP exercise routine. More research is needed to determine the long-term effects of Pilates exercise on post-surgical exercise rehabilitation and pelvic floor health.
  • Article
    The purpose of this study was to compare arterial stiffness after a bout of resistance exercise (RE) and an experimental condition consisting of repeated Valsalva maneuvers (VMs). Fourteen male participants randomly completed a lower-body, unilateral RE bout and a VM bout designed to alter blood pressure (BP) in a similar pulsatile fashion. Pulse-wave velocity (PWV, measured in metres per second (m.s-1)) was used to measure central and peripheral arterial stiffness and was assessed before and 20 min after each perturbation. Beat-to-beat blood pressure (BP) was assessed during bouts using finger plethysmography. Change in systolic BP, diastolic BP, mean arterial pressure, and pulse pressure were similar during both bouts. Central PWV increased after repeated VMs (7.1 +/- 0.3 m/s to 7.8 +/- 0.3 m/s), but not after RE (7.2 +/- 0.3 m/s to 7.2 +/- 0.3 m/s) (interaction, p = 0.032). There was no change in peripheral PWV after VM (8.9 +/- 0.3 m/s to 9.3 +/- 0.3 m/s) or RE (8.5 +/- 0.2 m/s to 8.4 +/- 0.2 m/s). Arterial stiffness increased after repeated VM. Even though presented with a similar BP load, arterial stiffness did not increase after acute RE. These findings suggest a role for VM in acutely altering arterial properties.
  • Article
    The objective of the study was to measure vaginal pressure during various daily activities in patients before and after vaginal surgery for pelvic organ prolapse, searching data for evidence-based activity guidelines. Vaginal pressure (VP) was studied in 23 patients during activities such as rest, pelvic floor contraction (PFC), coughing, Valsalva, rising from sitting to standing and lifting 2 and 5 kg with four different lifting techniques. VP was measured before, 1-5 days and 4-6 weeks after vaginal repair. Mean VP was four to five times higher during coughing and Valsalva compared to PFC and lifting 2 and 5 kg. Lifting in the walking position created a slightly higher VP compared to other lifting techniques, which did not differ. The VP did not increase when lifting 5 kg compared to 2 kg. Mean VP during coughing and Valsalva were significantly lower 1-5 days after the operation. VP was not related to the type of vaginal repair. The results imply that post-operative counselling should concentrate more on treating chronic cough and constipation than restrictions of moderate physical activities.
  • Article
    Evidence exists linking breath control to increases in intra-abdominal pressure and lumbar stability. Weight-lifting experts use this evidence as a rationale to suggest that increases in lumbar stability afforded by specific forms of breath control can influence the amount of force produced by the trunk. No studies have examined this issue. Therefore, this study determined whether voluntary control of the breath is related to maximal trunk extension force and if maximal force is correlated to intra-abdominal pressure. Thirteen men and 20 women (mean age: 25.6 years (5.5)) performed a maximal isometric trunk exertion in a knee bent posture using voluntary breath conditions: (1) inhalation prior to exertion with hold during exertion; (2) exhalation prior to exertion with hold during the exertion; (3) inhalation prior to the exertion with exhalation during the exertion. A subset of subjects (n=11) were also simultaneously measured for intra-abdominal pressure. Separate repeated measures ANOVA were used to determine the effects of breath conditions on force and intra-abdominal pressure. Pearson coefficients were used to determine the correlation between force and intra-abdominal pressure. Breath control did not significantly affect isometric force production (P=.089) but did affect intra-abdominal pressure (P=.003). Correlations between force and intra-abdominal pressure in each breath condition were low (range: 0.152-0.583). Although breath control was shown to influence intra-abdominal pressure, it does not appear to influence isometric trunk extension force in a knees bent position. Further, the intra-abdominal pressure produced in such efforts appears to be unrelated to the amount of force produced.
  • Article
    Anecdotal evidence suggests that people hold their breath during lifting tasks in order to increase intra-abdominal pressure (IAP) and thereby increase lumbar stability. Studies have shown that voluntary control of the breath influences IAP and that increases in IAP are related to increases in lumbar stability. However, a description of naturally occurring breath control during whole-body lifting tasks in normal healthy subjects is currently not available. Therefore, the specific aims of this study were to: (1) determine the naturally occurring breath patterns during lifting tasks in healthy subjects; (2) determine the effects of different levels of load during lifting tasks on natural breath control patterns in healthy subjects. The present study enrolled 20 healthy subjects to describe inspired volume and categories of airflow direction (inspiration, expiration, or breath hold) during two self-paced lifts of crates loaded at 5, 15, and 25% of body weight. When the breath pattern was examined across all loads there was a significant increase in the magnitude of inspired volume and the frequency of occurrence of inspiration immediately prior to lift-off. When examining the effect of load on breath patterns, there was a significant increase of inspired volume and occurrence of breath holding when lifting the heavy load compared to the medium and light loads. These results suggest that: (1) distinct patterns of natural breath control occur during lifting tasks; and (2) breath control is responsive to the timing and magnitude of load lifted.
  • Article
    Purpose Intra-abdominal pressure (IAP) and breathing behaviour are important preparative pre-lifting actions for functional stability during lifting. This study aimed to examine spontaneous changes in the peak rate of IAP development (Rate-IAP), peak IAP (Peak-IAP), the time of Rate- and Peak-IAP occurrence and respiratory volume in response to dynamic load lifting. Methods Eleven healthy men performed quick dynamic deadlifting using 30, 45, 60 and 75 % of the isometric maximal lifting effort (iMLE). IAP was measured using an intrarectal pressure transducer. The spontaneous respiratory volume was calculated from air flow data using pneumotachography. The lifting motion onset was determined from the hip joint motion using an electrogoniometer. Results From 30 to 75 % of the iMLE, Rate-IAP occurred early from 2 ± 28 to −179 ± 16 ms (P
  • Article
    Intra-abdominal pressure (IAP) is closely related to breathing behavior during lifting. Abdominal muscles contribute to both IAP development and respiratory function. The purpose of this study was to examine whether spontaneous breath volume and IAP altered with increased isometric lifting effort, and to compare the effect of different abdominal muscle strengths on these parameters. Maximal IAP during the Valsalva maneuver (maxIAP) and maximal isometric trunk flexor strength were measured in 10 highly trained judo athletes (trained) and 11 healthy men (controls). They performed isometric lifting with 0 (rest), 30, 45, 60, 75, 90, and 100% of maximal lifting effort (MLE). Natural inspiratory and expiratory volumes were calculated from air-flow data immediately before and after the start of lifting. IAP, measured using an intra-rectal pressure transducer during lifting, was normalized by maxIAP (%maxIAP). Trained athletes had higher maxIAP and stronger trunk flexor muscles than controls. A significant main effect of lifting effort was found on %maxIAP and respiratory volume. An interaction (lifting effort by group) was found only for %maxIAP. No significant group main effect or interaction was found for respiratory volume. Inspiratory volume increased significantly from tidal volume to above 60 and 45% of MLE in trained athletes and controls, respectively. Expiratory volume decreased significantly from tidal volume at above 30% of MLE in both the groups. These results suggest that spontaneous breath volume and IAP development are coupled with increased lifting effort, and strong abdominal muscles can modify IAP development and inspiratory behavior during lifting.
  • Article
    It has been proposed that pelvic girdle pain (PGP) subjects adopt a high load motor control strategy during the low load task of the active straight leg raise (ASLR). This study investigated this premise by observing the motor control patterns adopted by pain free subjects during a loaded ASLR (ASLR+PL). Trunk muscle activation, intra-abdominal pressure, intra-thoracic pressure, pelvic floor motion, downward pressure of the non-lifted leg and respiratory rate were compared between resting supine, ASLR and ASLR+PL. Additionally, side-to-side comparisons were performed for ASLR+PL. Incremental increases in muscle activation were observed from resting supine to ASLR to ASLR+PL. During the ASLR+PL there was a simultaneous increase in intra-abdominal pressure with a decrease in intra-thoracic pressure, while respiratory fluctuation of these variables were maintained. The ASLR+PL also resulted in increased pelvic floor descent and greater downward pressure of the non-lifted leg. Trunk muscle activation was comparable between sides during ASLR+PL in all muscles except lower obliquus internus abdominis, which was more active on the leg lift side. Pain free subjects respond to an ASLR+PL by a general increase in anterior trunk muscle activation, but preserve the pattern of greater activation on the side of the leg lift observed during an unloaded ASLR. This contrasts to findings in PGP subjects who, despite having a high load strategy for performing an ASLR on the symptomatic side of the body, display equal bilateral activation of the anterior abdominal wall during the ASLR. This differentiates PGP subjects from pain free subjects, supporting the notion that PGP subjects have aberrant motor control patterns during an ASLR.
  • Article
    Case control, repeated-measures, experimental laboratory study. To determine if, during a whole-body lifting task, individuals with low back pain (LBP) breathe differently than age-matched controls. Breath control may be optimized to provide increased intersegmental control of the lumbar spine through the generation of intra-abdominal pressure. Consequently, impairments in respiratory and trunk muscle coordination during lifting tasks may contribute to the occurrence or maintenance of LBP. Participants without LBP (n = 30) were matched by gender and age with those presenting with chronic mechanical LBP (n = 32) of at least 1 year in duration. Participants completed a total of 8 self-paced lifts of a crate from the floor to a table, with the crate empty during 4 of the lifts and loaded to 25% of the participant's body weight during 4 of the lifts. The amount of volume in the lungs, measured as a percentage of the individual's vital capacity (%VC), was identified at 9 points during the lifting task. A 2 × 2 × 2 × 9 (group by gender by load by time) mixed-model analysis of covariance (ANCOVA), with age as the covariate, was used to identify differences among conditions and groups of %VC used during the lift. Individuals with LBP performed the lifting task with more volume in their lungs (48.2 %VC) than healthy peers (40.9 %VC). Age significantly affected %VC used during the lift: with increasing age, participants with LBP increased inspired volume and participants without LBP decreased inspired volume. Individuals with LBP performed a lifting task with more inhaled lung volume than individuals without LBP. These findings are consistent with the theoretical link between breath control, intra-abdominal pressure, and lumbar segmental control.
  • Article
    Preventative and rehabilitative efforts relative to low back pain (LBP) and manual material handling (MMH) are often directed toward proper technique. However, breath control may be an additional factor to consider. Optimizing breath control may provide increased segmental control of the spine through the production of increased intra-abdominal pressure. It has been found that breath control differs during the lifting phase of MMH for individuals with LBP. However, little is known about breath control during the lowering portion even though it accounts for 30% of MMH tasks. In this study, individuals with LBP (n = 32) and aged-matched healthy individuals (n = 30) lowered a crate from a table to the floor four times with the crate empty and four times with the crate loaded at 25% of body weight. The amount of volume in the lungs as a percentage of each individual's vital capacity (VC) was identified at nine points during the lowering task. Individuals with LBP completed the lowering task with significantly more volume in their lungs (45.9% VC) than healthy peers (40.9% VC). Further, with increasing age %VC significantly increased in those with LBP. Moreover, %VC significantly increased in response to the mechanical challenges introduced when lowering a load. These findings support the theoretical link between breath control and lumbar segmental control and provide preliminary evidence supporting rehabilitative efforts which add a focus on breath control for those with LBP.
  • Article
    When rats are subjected to chemical hepatocarcinogenesis according to the protocol of D. Solt and E. Farber ((1976) Nature (London)263, 701–703), the liver exhibits elevated levels of tyrosine protein kinase activity as early as 3 weeks after the injection of diethylnitrosoamine. A more striking elevation in tyrosine protein kinase activity is noted in rat hepatomas induced by administration of chemical carcinogens, in particular that of 3′-methyl-4-dimethylaminoazobenzene (3′-Me-DAB). Tyrosine protein kinase solubilized from the particulate fraction of 3′-Me-DAB-induced hepatoma has a molecular weight identical to that of p60v-src, cross-reacts with p60v-src immunologically, phosphorylates the heavy chain of anti-p60v-src IgG, and probably belongs to a family of p60c-src. The tyrosine protein kinase from the particulate fraction of normal rat liver is indistinguishable from the hepatoma kinase in these properties; thus it apparently differs only in the level of activity. Whether the liver and hepatoma kinases differ merely quantitatively or whether they differ even qualitatively, however, remains to be elucidated.
  • Many surgeons recommend rest and restricting activities to their patients after surgery. The aim of this review is to summarize the literature regarding types of activities gynecologic surgeons restrict and intra-abdominal pressure during specific activities and to provide an overview of negative effects of sedentary behavior (rest). We searched PubMed and Scopus for years 1970 until present and excluded studies that described recovery of activities of daily living after surgery as well as those that assessed intra-abdominal pressure for other reasons such as abdominal compartment syndrome and hypertension. For our review of intra-abdominal pressure, we excluded studies that did not include a generally healthy population, or did not report maximal intra-abdominal pressures. We identified no randomized trial or prospective cohort study that studied the association between postoperative activity and surgical success after pelvic floor repair. The ranges of intra-abdominal pressures during specific activities are large and such pressures during activities commonly restricted and not restricted after surgery overlap considerably. There is little concordance in mean peak intra-abdominal pressures across studies. Intra-abdominal pressure depends on many factors, but not least the manner in which it is measured and reported. Given trends towards shorter hospital stays and off work intervals, which both predispose women to higher levels of physical activity, we urge research efforts towards understanding the role of physical activity on recurrence of pelvic organ prolapse and urinary incontinence after surgery.
  • Article
    Full-text available
    Aim: The purpose of this study was to compare the respiratory muscle and lung function measures of bodybuilders (BB) and endurance athletes (EA). Methods: Forty-two male subjects (22 BB and 20 EA) aged 20-35 years underwent respiratory muscle strength measurements (MIP and MEP), lung function testing (FEV1, FVC, FEV1/FVC%, IC, ERV, FRC, RV, and TLC), hydrostatic weighing and VO2max testing. One-repetition maximum (1RM) for bench press, squat and deadlift was performed by BB. Results: BB had significantly greater MIP and MEP compared to EA by 43% and 53% respectively (P<0.01). Moderate correlation was found for MEP and 1RM bench press (P<0.01), and weak correlations found for the squat and deadlift (P<0.01). Fat-free mass was significantly greater for BB compared with EA (P<0.01), while VO2max was significantly greater for EA compared with BB (P<0.01). No differences in lung function indices were observed between groups. Conclusion: When compared to EA, BB exhibited significantly greater respiratory muscle strength. The maximal load lifted for bench press predicted expiratory muscle strength gain. Lung function measures did not differ between the groups.
  • Article
    Abstract Examination of naturally occurring respiration during postural challenges may increase our understanding of the factors linking respiration to lumbar segmental control. This study determined if the timing and magnitude of inhaled volume changes were related to mechanical events that challenge spinal stability during a tiptoe task. Thirty healthy individuals (15 male) had airflow recorded while they completed a tiptoe task which involved: moving onto tiptoe while reaching toward a hanging target (ascent); grasping and holding the target while maintaining the tiptoe position for 3 s (hold); and then returning to the start position (descent). The rate of airflow and amount of inhaled volume (normalized to vital capacity (%VC)) were identified at 13 different intervals spanning the ascent, hold and descent phase. Using repeated measures analysis of variance, significant main effects were identified for both rate of airflow (p < 0.001) and %VC (p < 0.001). Exploration of these main effects revealed that individuals tended to inspire and increase %VC during the ascent phase, hold their breath and maintain %VC during the hold phase when whole body balance is challenged, and exhale during the descent phase. These findings are congruent with theories suggesting that breath control is linked in predictable ways to potentially improve lumbar spine stiffness when presented with mechanical challenges during functional tasks.
  • Article
    Functional constipation is a common bowel disorder leading to activity restrictions, and reduced health-related quality of life. Typically, this condition is initially managed with prescription of laxatives and/or fiber supplementation. However, these interventions are often ineffective and fail to address the underlying pathophysiology and impairments contributing to this condition. Physical therapists possess knowledge and skills to diagnose and manage a wide range of musculoskeletal and motor coordination impairments that may contribute to functional constipation. Relevant anatomic, physiologic and behavioral contributors to functional constipation are discussed with regard to specific constipation diagnoses. A framework for physical therapy examination of impairments that can impact gastrointestinal function including postural, respiratory, musculoskeletal and neuromuscular; and behavioral is offered. Within the context of diagnostic-specific patient cases, multifaceted interventions are described as they relate to impairments underlying functional constipation type. The current state of evidence to support these interventions and patient recommendations is summarized. This perspective not only aims to heighten physical therapists' awareness and management of this condition, but also to stimulate clinical questioning that will open avenues for future research to improve patient care.
  • Article
    Many surgeons restrict activities postoperatively. Intra-abdominal pressure during some activities is known; however, many everyday activities have not been studied. Our aim was to compare the intra-abdominal pressures created during unavoidable physical activities with activities that commonly are restricted after surgery. Nine healthy subjects (2 men, 7 women; age, 28 +/- 7 y) performed 5 repetitions of various activities while their intravesicular pressures was measured. The resting intravesicular pressure was 17 +/- 5 mm Hg, increasing to a maximum of 112 +/- 35 mm Hg during forceful coughing. The intravesicular pressure increase was greatest with forceful coughing, followed by the Valsalva maneuver. The results suggest that the greatest increase in intra-abdominal pressure occurs during some unavoidable activities. Based on this study, postoperative restrictions may be unnecessary. Further experience based on a larger study is needed to answer this important clinical question.
  • Article
    Intra-abdominal pressure (IAP) has been proposed as an important mechanism in manual lifting and breathing mechanics. Direct (invasive) measures of IAP have required the swallowing of a radio transducer or insertion of a pressure sensor into the rectum or down the oesophagus to the stomach. The purpose of this study was to investigate the relationship between a non-invasive method (EMG) and IAP. Several tasks involving abdominal muscle activation were performed to assess whether or not IAP played a common role in these tasks. IAP and EMG from rectus abdominis, the abdominal obliques, intercostals and erector spinae were measured. Peak IAP reached 340 mmHg (valsalva) for one subject but most values were less than 100 mmHg for tasks other than valsalva. The IAP and EMG data provide some insight into the role of IAP during the performance of specific tasks. Peak IAP within 60 ms of the onset of vigorous abdominal activation indicated the importance of a very rapid pressure response to abdominal muscle activation. The correlations between various muscle EMG time histories and IAP exceeded 0·80 for only two activities (i.e. r(2) = 0·82 between the intercostals and IAP during valsalva manoeuvres). These data suggest that no unifying hypothesis exists to explain the role of IAP for a wide variety of movement tasks; rather, the role of IAP is task specific.
  • Article
    The increases in pressure in the thoracic and abdominal cavities when pushing, pulling and stooping to lift hove been measured in 16 male and 15 female young adults. The greatest pressure increases in the largest number of subjects occurred when pushing, and least pressure changes occurred when pulling. It is suggested that changes in intratruncal pressures may be used as an index of the magnitudes of forces acting on the trunk during working manoeuvres.
  • Article
    The intervertebral disc pressure in the third lumbar disc, the intraabdominal pressure, and the myoelectric activity of several muscles of the back were recorded simultaneously in 4 healthy subjects. The studies comprised static pulling against a fixed resistance with the back either straight or flexed, dynamic lifting, and holding of a weight at various distances to the body. The distance between the weight and the body was found to influence the stress on the back much more than the method used to lift. (C) Lippincott-Raven Publishers.
  • Article
    To evaluate the effects of abdominal belts on lifting performance, muscle activation, intra-abdominal pressure and intra-muscular pressure of the erector spinae muscles. Simultaneous measurement of intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles was performed during the Valsalva maneuver and some isometric lift exertions. While several hypotheses have been suggested regarding the biomechanics of belts and performance has been found to increase when lifting with belts, very little is known about the modulating effects on trunk stiffness. At present, there is no reason to believe that spine tolerance to loads increases with belts. An abdominal belt designed for weightlifting was used. Intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles and myoelectric activities of trunk muscles (erector spinae, rectus abdominis and external oblique) were measured simultaneously during the Valsalva maneuver as well as three types of isometric lifting exertions (arm, leg and torso lift). A paired t-test was used to analyze for statistical differences between the two conditions (without-belt and with-belt) in intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles and in the integrated EMG of the trunk muscles. Intra-muscular pressure of the erector spinae muscles increased significantly by wearing the abdominal belt during Valsalva maneuvers and during maximum isometric lifting exertions, while maximum isometric lifting capacity and peak intra-abdominal pressure were not affected. Integrated EMG of rectus abdominis increased significantly by wearing the abdominal belt during Valsalva maneuvers (after full inspiration) and during isometric leg lifting. Wearing abdominal belts raises intra-muscular pressure of the erector spinae muscles and appears to stiffen the trunk. Assuming that increased intra-muscular pressure of the erector spinae muscles stabilizes the lumbar spine, wearing abdominal belts may contribute to the stabilization during lifting exertions.
  • Article
    Evaluation of trunk movements, trunk muscle activation, intra-abdominal pressure and displacement of centres of pressure and mass was undertaken to determine whether trunk orientation is a controlled variable prior to and during rapid bilateral movement of the upper limbs. Standing subjects performed rapid bilateral symmetrical upper limb movements in three directions (flexion, abduction and extension). The results indicated a small (0.4-3.3 degrees) but consistent initial angular displacement between the segments of the trunk in a direction opposite to that produced by the reactive moments resulting from limb movement. Phasic activation of superficial trunk muscles was consistent with this pattern of preparatory motion and with the direction of motion of the centre of mass. In contrast, activation of the deep abdominal muscles was independent of the direction of limb motion, suggesting a non-direction specific contribution to spinal stability. The results support the opinion that feedforward postural responses result in trunk movements, and that orientation of the trunk and centre of mass are both controlled variables in relation to rapid limb movements.
  • Article
    The weight of the upper part of the trunk is partially transmitted to the pelvis via the vertebral column. If the muscle walls around the abdominal cavity are contracted, a high pressure can be generated within the cavity (greater than 200 mmHg). The abdominal space can them transmit part of weight to, e.g., the upper part of the body, Intra-abdominal pressure recordings have been performed during locomotion and other natural movements with intragastric pressure recordings. With each step, there is a phasic variation in pressure, with its peak coinciding with that of the peak vertical force exerted by the leg against the ground. The peak values increase progressively with the speed of walking/running up to a mean of 38 mmHg and with trough values of 16 mmHg. The phasic variations with each step is due to a phasic activation of the abdominal muscles, with an EMG activity starting 50 ms or more before foot contact. If an extra load is put on the back, the posture changes and at the highest speed of running the pressure values are significantly higher than without this additional load. After a jump down from a moderate height of 0.4 m, the average increase is 89 mmHg and can often exceed 100 mmHg. These pressure changes are large and will presumably act to unload the spine under the prevailing biomechanical conditions and, in addition, there will no doubt be an effect on the circulatory system.
  • Article
    The aim was to investigate possible relationships between activities of the individual muscles of the ventrolateral abdominal wall and the development of pressure within the abdominal cavity. Intra-muscular activity was recorded bilaterally from transversus abdominis, obliquus internus, obliquus externus and rectus abdominis with fine-wire electrodes guided into place using real-time ultrasound. Intra-abdominal pressure was measured intragastrically using a micro tip pressure transducer. Six males were studied during loading and movement tasks with varied levels of intra-abdominal pressure. During both maximal voluntary isometric trunk flexion and extension, transversus abdominis activity and intra-abdominal pressure remained constant, while all other abdominal muscles showed a marked reduction during extension. When maximal isometric trunk flexor or extensor torques were imposed upon a maximal Valsalva manoeuvre, transversus abdominis activity and intra-abdominal pressure remained comparable within and across conditions, whereas obliquus internus, obliquus externus and rectus abdominis activities either markedly increased (flexion) or decreased (extension). Trunk twisting movements showed reciprocal patterns of activity between the left and right sides of transversus abdominis, indicating an ability for torque development. During trunk flexion--extension, transversus abdominis showed less distinguished changes of activity possibly relating to a general stabilizing function. In varied pulsed Valsalva manoeuvres, changes in peak intra-abdominal pressure were correlated with mean amplitude electromyograms of all abdominal muscles, excluding rectus abdominis. It is concluded that the co-ordinative patterns shown between the muscles of the ventrolateral abdominal wall are task specific based upon demands of movement, torque and stabilization. It appears that transversus abdominis is the abdominal muscle whose activity is most consistently related to changes in intra-abdominal pressure.
  • Article
    The purpose of this study was to determine whether abdominal belts such as those prescribed to industrial workers reduced trunk muscle activity and/or increased intra-abdominal pressure (IAP). In this study, six subjects lifted loads (72.7 to 90.9 kg) both with and without wearing a weightlifter belt. In addition, further trial conditions required that subjects lifted both with the breath held or continuously expiring on lifting effort. Dynamic hand loads were recorded together with intra-abdominal pressure (IAP) and abdominal, intercostal and low back EMG. Every subject demonstrated an increase in IAP when wearing the belt during both breathing conditions: 99 mmHg with no belt; 120 mmHg wearing belt (p less than 0.0001). However, it was also found that significant increases in IAP occurred (p less than 0.017) when the breath was held versus exhaling with or without the belt. One would expect that if the belt relieved either the direct compressive load on the spine or assisted IAP to produce an extensor moment then this would be reflected in diminished extensor muscle activity. Erector spinae activity tended to be lower with the breath held suggesting a reduced load on the lumbar spine although wearing a belt did not augment this reduction. In the case studies with subjects wearing an ergogenic corset designed for use by industrial manual materials handlers, perceptions of improved trunk stability were reported. However, the muscle activity and IAP results of this study during short duration lifting tasks make it difficult to justify the prescription of abdominal belts to workers.
  • Article
    Intra-abdominal pressure (IAP) has been widely hypothesized to reduce potentially injurious compressive forces on spinal discs during lifting. To investigate the effects of a standard lifting belt on IAP and lifting mechanics, IAP and vertical ground reaction force (GRF) were monitored by computer using a catheter transducer and force platform while nine subjects aged 28.2 +/- 6.6 yr dead-lifted a barbell both with and without a lifting belt at 90% of maximum. Both IAP and GRF rose sharply from the time force was first exerted on the bar until shortly after it left the floor, after which GRF usually plateaued while IAP either plateaued or declined. IAP rose significantly (P less than 0.05) earlier with than without the belt. When the belt was worn, IAP rose significantly earlier than did GRF. Both with and without the belt, IAP ended its initial surge significantly earlier than did GRF. Variables significantly greater with than without a belt included peak IAP, area under the IAP vs time curve from start of initial IAP surge to lift-off, peak rate of IAP increase after the end of its initial surge, and average IAP from lift-off to life completion. In contrast, average rate of IAP increase during its initial surge was significantly lower with the belt. Correlations are presented which provide additional information about relationships among the variables. Results suggest that the use of a lifting belt increases IAP, which may reduce disc compressive force and improve lifting safety.
  • Article
    Full-text available
    The abdominal mechanism, utilizing intraabdominal pressure, has been described and numericized. Simulations show that the lumbodorsal fascia under control of the abdominal muscles contributes to reduce the stress at the intervertebral joint. The musculature of the lumbar spine is of primary importance in the control of the efficiency of the spinal mechanism. The system of loading, which results in observable physiologic response, maintains the compressive load at virtually 90 degrees at the bisector of the disc for all weights and all angles of forward flexion.
  • Article
    The aim of this study was to compare trunk muscle strength and intra-abdominal pressure during lifting in low-back patients and in healthy controls. Twenty male workers with 2-18 year history (median 5.5 years) of low-back pain went through strength tests of trunk flexion and extension and a series of standardized lifts. The intra-abdominal pressure (IAP) and the EMG activity of the oblique abdominal muscles and of the erector spinae muscles were recorded. The results were compared with those in 20 healthy men exposed to similar loads at work and at leisure. The low-back patients had reduced abdominal muscle strength (-25%) compared with the healthy controls. The IAP during lifting was the same in the two groups despite the difference in abdominal muscle strength. The trunk extension strength was the same in the two groups. The oblique abdominal muscles were only moderately activated during lifting (5-15% of maximum activity with 25 kg) both in low-back patients and in healthy controls. The erector spinae muscle was strongly activated during lifting (40-60% of maximum activity with 25 kg) both in low-back patients and in healthy controls. During backlifting the duration of erector spinae activity varied. Back patients had extended activity compared with the healthy controls. Stiffness seemed to affect the duration of activity in both groups. The oblique abdominal muscles seem to be of no decisive importance to the IAP.
  • Article
    The intra-abdominal pressure (IAP) has been regarded as important for stabilization and relief of the lumbar spine when exposed to heavy loads, such as when lifting. Previous trials, however, have failed to increase the IAP by abdominal muscle training. Twenty healthy subjects, 20 low-back patients and 10 weight-lifters, were tested with various breathing techniques in order to elucidate the causal factors of the IAP rise during lifting and the effects respiration. Those with high IAP and low IAP as well as those with great variations in IAP underwent an extended program. The intra-abdominal and intrathoracic pressures and the EMG of the oblique abdominal, the erector spinae and--in some cases--the puborectalis muscles, were recorded. The transdiaphragmatic pressure was calculated both during lifting and during the Mueller manoeuvre. The IAP rise during lifting seems to be correlated to a good coordination between the muscles surrounding the abdominal cavity. Of these, the diaphragm seems to be the most important for the IAP level. Closure of the glottis seems to help the diaphragm to maintain the IAP rise, otherwise the respiration type seems to be less important for the IAP during lifting.
  • Article
    Isometric training of the abdominal muscles is often recommended in programs of primary or secondary prevention for low-back pain. In this study 20 male workers with 2-18 years' history (average 5 1/2 years) of low-back pain without sciatica went through intense isometric abdominal muscle training for 5 weeks. Before and after training the subjects had trunk flexion and extension strength tests and a series of standardized lifts. The intraabdominal pressure (IAP) and the EMG activity of the oblique abdominal muscles, and of the erector spinae muscle were recorded. It was found that: the strength of the abdominal muscles increased; the increased strength was correlated to an improved recruitment of motor units in the oblique abdominal muscles; the EMG activity of the oblique abdominal muscles when lifting decreased after training, i.e. the acquired ability to recruit more motor units was not made use of; the IAP at lifting was generally not affected. A better knowledge of the mechanisms responsible for the IAP in different situations is needed to support advice on training or other prevention.
  • Article
    The recording of intra-abdominal pressure (IAP) variations has been proposed as a tool for evaluating the biomechanical stress imposed on the low back in working tasks. Literature data are however controversial as regards the relationship between IAP and lumbar stress, some studies showing that IAP increases with trunk flexion while others indicate that IAP is greater when the trunk is kept erect. The present study was aimed at a quantification of this relation for sagittal-plane lifting activities performed at various inclinations of the trunk. Fifteen young males lifted loads ranging from 49N to 147 N from four standing postures: Trunk erect and trunk flexed at 30,60 and 90 degrees from the vertical. The force exerted at the hands, as well as intra-abdominal and intrathoracic pressures were recorded throughout the lift and the UILS moment was calculated using a static biemechanical model. Results showed that the IAP-moment relation is influenced both by the trunk angle and by individual characteristics. Peak IAP increases per unit increase in lumbar moment were higher in the erect posture than in the flexed ones, and in each posture were inversely related to the subject's stature and maximal oxygen uptake. In the flexed postures, no significant general TAP-moment relation could be drawn from the 15 subjects' data, whereas at the individual level, the relation was significant for two thirds of the subjects. The study thus shows that IAP cannot be used as an index of biomechanical stress, unless the individual IAP to lumbar moment relation is considered. It is suggested that the differences in pressure response found between erect and flexed trunk postures were related more to differences in the leverage moment acting at the shoulder than to differences in trunk angle.
  • Article
    In order to investigate intra-thoracic pressure (ITP) and intra-abdominal pressure (IAP) during lifting and jumping, 11 males were monitored as they performed the dead lift (DL), slide row (SR), leg press (LP), bench press (BP), and box lift (BL) at 50, 75 and 100% of each subject's four-repetition maxima, the vertical jump (VJ), drop jump (DJ) from 0.5 and 1.0 m heights, and Valsalva maneuver (VM). Measurements were made of peak pressure, time from pressure rise to switch-marked initiation of body movement, and time from the movement to peak pressure. The highest ITP and IAP occurred during VM (22.2 +/- 6.0 and 26.6 +/- 6.7 kPa, respectively) with one individual reaching 36.9 kPa (277 mm Hg) IAP. In ascending order of peak ITP during the highest resistance sets, the activities were SR, BP, VJ, DJ, DL, BL, LP, and VM, while the order for IAP was BP, VJ, DJ, BL, DL, LP, SR, and VM. Pressures significantly (P less than 0.05) increased with amount of weight lifted, rising before and peaking after the weight moved. IAP generally rose earlier and was of greater magnitude than ITP. For the jumps, pressure rose and diminished before the feet lost contact with the ground. Drop-jump height did not affect pressure. Correlation of pressure with weight lifted was fair to good for most activities.
  • Article
    Biomechanical models used to estimate loads on the lumbar spine often predict internal low back forces for heavy lifts that exceed known tissue tolerances, yet the particular lift caused no apparent damage to the lifter. To deal with this paradox, many researchers have incorporated some form of spinal compression alleviation from intra-abdominal pressure (IAP). The purpose of this work was to re-examine some of the issues involved in the feasibility of IAP to reduce spinal loads during stressful lifts. Questions remain over the trade-off between the beneficial tensile force on the spine, exerted via the diaphragm and pelvic floor when IAP is produced, and the undesirable compressive effects of abdominal muscular force required to maintain the pressure within the abdomen. Various strategies of modelling IAP and its effects on low back loading were employed, Three major differences between this and most previous models of IAP effects were the attempt to quantify the size of abdominal muscle forces and the utilization of a considerably smaller diaphragm cross-sectional area and corresponding IAP moment arm. Abdominal EMG recorded from rectus abdominis, external oblique and internal oblique generally indicated low levels of activity throughout the high loading phase of the lifts. However, model output predicted that the compressive forces generated by the abdominal wall musculature were larger than the beneficial action of those forces thought to alleviate spinal compression via IAP. These results suggest that modelling IAP as a force vector which produces a trunk extensor moment and lumbar disc compression alleviation, without accounting for the compressive effects of abdominal muscle forces required to produce the IAP, is incorrect. This does not exclude a possible role of IAP in assisting the trunk during loading, only that the role of IAP is not modelled properly at present. IAP may indeed play a role in spinal stabilization as yet not well understood.
  • Article
    The ability of a partial or full Valsalva maneuver (voluntary pressurization of the intraabdominal cavity) to unload the spine was investigated in four subjects. During the performance of five isometric tasks, intraabdominal and intradiscal pressures and surface myoelectric activities in three lumbar trunk muscle groups were measured. The tasks were carried out without voluntary pressurization of the intraabdominal cavity and then when the subjects performed partial and full Valsalva maneuvers. A biomechanical model analysis of each task was made to help interpret the experimental measurements. Intraabdominal pressure was found not to be an indicator of spine load in these experiments. The Valsalva maneuvers did raise intraabdominal pressure, but in four of the five tasks increased rather than decreased lumbar spine compressions occurred.
  • Article
    The aim of the work is to establish guidelines for force applications by all normal female workers which can be used to assess the acceptability of existing working conditions, and to assist in the design of new working procedures. A significant relationship between lumbar stress and increase in intra-abdominal pressure has been established for females which is sufficiently sound for use when investigating load handling by women in industry. Female occupations with differing incidences of posterior trunk injuries have been identified and it has been shown that the lumbar stresses sustained by the high- and low-risk groups are different. This difference has been used to create a provisional level of lumbar stress for female which, if exceeded sufficiently often, might increase the risk of a back injury. Force limits for a fit young female population based on this provisional level are, on average, between 45 and 60% of the corresponding male limit values. It is hoped to confirm these findings in the near future.
  • Article
    An experiment was performed to test the static and dynamic lifting capabilities of the back. Twenty healthy male and female subjects exerted maximal force with the back under isometric and isokinetic lifting positions. Torque about the lumbosacral junction and intra-abdominal pressure (IAP) production were monitored under the experimental conditions. Torque production capability was found to increase as trunk angle increased and decreased as angular velocity increased. IAP was found to be primarily a funciton of angle and a weak indicator of torque. A significant IAP-torque onset delay was identified as was a physiological source of IAP.
  • Article
    The study is an investigation into the form of the abdominal pressure reflex in normal individuals under isometric loading of the torso. Various directions of load are imposed, and both flexed and upright postures are adopted. The sensitivity of the pressurization to the applied moment is calculated, the form of the response being linear in each case. The results show that the response sensitivity varies with subject posture and mass and with the direction and site of loading. The highest sensitivities are in response to extensor moments and the lowest, when the torso is flexed. It would appear that the supportive influence of the trunk cannot be considered constant under all loading conditions, nor can a single explanation of its function be adequate under both extensor and flexor applied moments.
  • Article
    Several investigations have shown that during physical activity there is a relationship between the magnitude of trunk stresses and increases in intraabdominal pressure (IAP). This study was undertaken to quantify this relationship for moments acting at lumbar level (L4/5) during lifting activities. Fourteen young males performed a series of 60 bimanual lifts in the sagittal plane in 12 different hand positions, while standing in an erect posture. In each hand position, loads ranging from 59 to 706 N were selected in order to apply identical forces at the shoulder, whatever the hand-shoulder distance. The moment about L4/5 was determined through a biomechanical model deriving data from the subject's anthropometry and the photographically recorded posture.Results showed that IAP was well correlated with the lumbar moment in all the hand positions but one, whose postural configuration put some limitations on the exertion of force. When data from that position were excluded, IAP (kPa) was related to the moment (Nm) at L4/5 level by y=0·079x−1127 (r=0·75). IAP measurement may thus be used as an index of spinal stress in real-life lifting tasks.
  • Ten young (average age 20 years) healthy male volunteers performed the Valsalva maneuver (40 mmHg for 15 seconds) in the supine and the upright position. The heart rate (HR), stroke volume (SV) and the cardiac index (CI) were registered using ECG and impedance cardiography. During the expiratory strain of the Valsalva maneuver the HR increased about equally in the two positions while the decreases in the SV and the CI were in the supine position significantly greater than in the upright position. The CI decreased to equal levels in both positions after 15 seconds of strain. The rise in the HR due to the expiratory strain did not correlate significantly with the decrease in the CI in either position. The correlation between the HR rise and the SV decrease was almost significant (p less than 0.05) in the supine position and significant (p less than 0.01) in the upright position after 5 seconds of strain but not after 10 or 15 seconds. These observations suggest that the relationship between the rise in the HR and the decrease in the venous return does not remain constant during 15 seconds of expiratory strain. Perhaps the cardiopulmonary baroreceptor reflexes affect the HR after five seconds of strain more than they do after 10 or 15 seconds of strain.
  • Article
    Ten male and ten female subjects were tested for their ability to exert maximal force about the lumbo-sacral junction (as is done during lifting) under controlled isometric and isokinetic conditions. The myoelectric activity of ten trunk muscles, intra-abdominal pressure, and torque produced by the back were monitored. There are prominent differences in the manner in which subjects utilize the musculature of the trunk for the production of torque statically and dynamically. A significant lag was identified between the onset of intra-abdominal pressure and torque, and this lag increased with increasing trunk velocity. These differences between isometric and isokinetic exertions suggest that isokinetic trunk testing provides a means of controlled evaluation that is appropriate for manual materials handling situations.
  • Article
    Intra-abdominal pressure measurements correlate with intradiscal pressures and myoelectric activity of the trunk muscles and are useful determinants of spinal stress. Measurements made in industrial situations using a radio pill allow analysis of stresses imposed by different tasks.
  • Article
    The effect of 10 weeks' specific abdominal strength training (resisted trunk rotations) on intra-abdominal pressure was investigated in 10 healthy males. Isometric rotational force, trunk flexor and extensor torque and intra-abdominal pressure were measured as well as intra-abdominal pressure responses to Valsalva manoeuvres, maximal pulsed pressures, drop jumps and trunk perturbations. The rotational strength increased 29.7% after training without significant change in intra-abdominal pressure. The isometric flexor strength did not change, while the extensor strength increased 11.0%. Valsalva and pulsed pressures increased 11.6 and 9.2%, respectively. The rate of intra-abdominal pressure development during pulsed pressures, drop jumps and trunk perturbations increased after training. The level of intra-abdominal pressure during the latter two tasks remained unchanged. It is concluded that an increase in strength of the trunk rotators with training improves the ability to generate higher levels of voluntarily induced intra-abdominal pressure and increases the rate of intra-abdominal pressure development during functional situations.
  • Intra-abdominal pressure (IAP), force and electromyographic (EMG) activity from the abdominal (intra-muscular) and trunk extensor (surface) muscles were measured in seven male subjects during maximal and sub-maximal sagittal lifting and lowering with straight arms and legs. An isokinetic dynamometer was used to provide five constant velocities (0.12-0.96 m.s-1) of lifting (pulling against the resistance of the motor) and lowering (resisting the downward pull of the motor). For the maximal efforts, position-specific lowering force was greater than lifting force at each respective velocity. In contrast, corresponding IAPs during lowering were less than those during lifting. Highest mean force occurred during slow lowering (1547 N at 0.24 m.s-1) while highest IAP occurred during the fastest lifts (17.8 kPa at 0.48-0.96 m.s-1). Among the abdominal muscles, the highest level of activity and the best correlation to variations in IAP (r = 0.970 over velocities) was demonstrated by the transversus abdominis muscle. At each velocity the EMG activity of the primary trunk and hip extensors was less during lowering (eccentric muscle action) than lifting (concentric muscle action) despite higher levels of force (r between -0.896 and -0.851). Sub-maximal efforts resulted in IAP increasing linearly with increasing lifting or lowering force (r = 0.918 and 0.882, respectively). However, at any given force IAP was less during lowering than lifting. This difference was negated if force and IAP were expressed relative to their respective lifting and lowering maxima.(ABSTRACT TRUNCATED AT 250 WORDS)
  • Article
    1. The response of the diaphragm to the postural perturbation produced by rapid flexion of the shoulder to a visual stimulus was evaluated in standing subjects. Gastric, oesophageal and transdiaphragmatic pressures were measured together with intramuscular and oesophageal recordings of electromyographic activity (EMG) in the diaphragm. To assess the mechanics of contraction of the diaphragm, dynamic changes in the length of the diaphragm were measured with ultrasonography. 2. With rapid flexion of the shoulder in response to a visual stimulus, EMG activity in the costal and crural diaphragm occurred about 20 ms prior to the onset of deltoid EMG. This anticipatory contraction occurred irrespective of the phase of respiration in which arm movement began. The onset of diaphragm EMG coincided with that of transversus abdominis. 3. Gastric and transdiaphragmatic pressures increased in association with the rapid arm flexion by 13.8 +/- 1.9 (mean +/- S.E.M.) and 13.5 +/- 1.8 cmH2O, respectively. The increases occurred 49 +/- 4 ms after the onset of diaphragm EMG, but preceded the onset of movement of the limb by 63 +/- 7 ms. 4. Ultrasonographic measurements revealed that the costal diaphragm shortened and then lengthened progressively during the increase in transdiaphragmatic pressure. 5. This study provides definitive evidence that the human diaphragm is involved in the control of postural stability during sudden voluntary movement of the limbs.
  • Article
    Full-text available
    The increased intra-abdominal pressure (IAP) commonly observed when the spine is loaded during physical activities is hypothesized to increase lumbar spine stability. The mechanical stability of the lumbar spine is an important consideration in low back injury prevention and rehabilitation strategies. This study examined the effects of raised IAP and an abdominal belt on lumbar spine stability. Two hypotheses were tested: (1) An increase in IAP leads to increased lumbar spine stability, (2) Wearing an abdominal belt increases spine stability. Ten volunteers were placed in a semi-seated position in a jig that restricted hip motion leaving the upper torso free to move in any direction. The determination of lumbar spine stability was accomplished by measuring the instantaneous trunk stiffness in response to a sudden load release. The quick release method was applied in isometric trunk flexion, extension, and lateral bending. Activity of 12 major trunk muscles was monitored with electromyography and the IAP was measured with an intra-gastric pressure transducer. A two-factor repeated measures design was used (P < 0.05), in which the spine stability was evaluated under combinations of the following two factors: belt or no belt and three levels of IAP (0, 40, and 80% of maximum). The belt and raised IAP increased trunk stiffness in all directions, but the results in extension lacked statistical significance. In flexion, trunk stiffness increased by 21% and 42% due to 40% and 80% IAP levels respectively; in lateral bending, trunk stiffness increased by 16% and 30%. The belt added between 9% and 57% to the trunk stiffness depending on the IAP level and the direction of exertion. In all three directions, the EMG activity of all 12 trunk muscles increased significantly due to the elevated IAP. The belt had no effect on the activity of any of the muscles with the exception of the thoracic erector spinae in extension and the lumbar erector spinae in flexion, whose activities decreased. The results indicate that both wearing an abdominal belt and raised IAP can each independently, or in combination, increase lumbar spine stability. However, the benefits of the belt must be interpreted with caution in the context of the decreased activation of a few trunk extensor muscles.
  • Article
    Three-dimensional trunk motion, trunk muscle electromyography and intra-abdominal pressure were evaluated to investigate the preparatory control of the trunk associated with voluntary unilateral upper limb movement. The directions of angular motion produced by moments reactive to limb movement in each direction were predicted using a three-dimensional model of the body. Preparatory motion of the trunk occurred in three dimensions in the directions opposite to the reactive moments. Electromyographic recordings from the superficial trunk muscles were consistent with preparatory trunk motion. However, activation of transversus abdominis was inconsistent with control of direction-specific moments acting on the trunk. The results provide evidence that anticipatory postural adjustments result in movements and not simple rigidification of the trunk.
  • Article
    In humans, when the stability of the trunk is challenged in a controlled manner by repetitive movement of a limb, activity of the diaphragm becomes tonic but is also modulated at the frequency of limb movement. In addition, the tonic activity is modulated by respiration. This study investigated the mechanical output of these components of diaphragm activity. Recordings were made of costal diaphragm, abdominal, and erector spinae muscle electromyographic activity; intra-abdominal, intrathoracic, and transdiaphragmatic pressures; and motion of the rib cage, abdomen, and arm. During limb movement the diaphragm and transversus abdominis were tonically active with added phasic modulation at the frequencies of both respiration and limb movement. Activity of the other trunk muscles was not modulated by respiration. Intra-abdominal pressure was increased during the period of limb movement in proportion to the reactive forces from the movement. These results show that coactivation of the diaphragm and abdominal muscles causes a sustained increase in intra-abdominal pressure, whereas inspiration and expiration are controlled by opposing activity of the diaphragm and abdominal muscles to vary the shape of the pressurized abdominal cavity.
  • Article
    Objective. This study was designed to help interpret the biomechanical role of intraabdominal pressure during lifting type motions of the trunk. Design. An in vivo study was performed in which intra-abdominal pressure was observed as subject trunks were subjected to different dynamic trunk loading conditions common during industrial lifting. Background. There is a little consensus as to the biomechanical role of intra-abdominal pressure during lifting. Previous studies have suggested that: it may assist in load relief when lifting, may be involved in trunk stability, and/or may be used as a measure fo spine loading. Thus, in general, our understanding of intra-abdominal pressure is rather poor. Methods. In this study intra-abdominal pressure was monitored using a radio pill in 114 subjects over a series of four experiments. Subject's trunks were subjected to different dynamic trunk symmetric and asymmetric trunk loading conditions that are common during industrial lifting tasks. Results. The results indicated that (1) intra-abdominal pressure increased to significant levels (above 10 mmHg) only when more than 54 Nm of trunk torque were supported; (2) intra-abdominal pressure increases monotonically (up to 150 mmHg) as a function of trunk velocity; and (3) under concentric conditions intra-abdominal pressure increases as a function of greater asymmetry, whereas, under eccentric conditions the response changes to a much lesser extent as asymmetry changes. Conclusions. These findings suggest that intra-abdominal pressure appears to be more a by-product of trunk muscle coactivation. Any mechanical advantage gained from intraabdominal pressure might be in the form of a preparatory action resulting from muscle coactivation that stiffens the trunk just prior to a rapid trunk extension exertion. This function may reinforce previous hypotheses regarding the stability role of intra-abdominal pressure.
  • Article
    The purpose of the present study was to investigate whether increased intra-abdominal pressure (IAP) can be achieved without elevating the overall trunk muscle co-contraction that causes increased spine compression force. Ten subjects performed isometric trunk flexion, extension, and lateral bending exertions while generating 0%, 40% and 80% of their maximal IAP or while co-contracting trunk muscles without consciously raising IAP. An additional three subjects performed a variety of ramp IAP, co-contraction and isometric exertion tasks while holding their breaths and while exhaling. An 18 degree-of-freedom, electromyogram (EMG)-assisted biomechanical model was used to quantify trunk muscle co-contraction with calculations of spine compression force and stability. Spine stability and compression force increased proportionally with increased IAP regardless of whether the subjects intentionally generated IAP or consciously avoided it. This increase was accomplished with significantly greater co-contraction of 12 major trunk muscles. The EMG activation of all muscles was highly correlated with IAP and intra-thoracic pressure (ITP) ( r from 0.59 to 0.95). Activity of the thoracic erector spinae correlated the best with ITP ( r=0.81), which in turn was correlated with IAP ( r=0.91). It was not possible to co-contract trunk muscles without generating IAP and ITP, or conversely to generate IAP without trunk muscle co-contraction and increased ITP.
  • Article
    In this study, sudden load was applied to the trunk and situations with alternating low levels of intra-abdominal pressure (IAP) realistic to work situations were compared. The aim was to see if IAP and the small increases in co-contraction of back muscles that follow are capable of increasing the stiffness of the lumbar spine. Nine subjects participated in ten sudden load situations during which they were asked to hold a box and conduct a percentage of maximal IAP. The hip was fixed and the load was applied horizontally on the trunk. EMG, IAP, and movement of the trunk were measured. It was found that IAP of a size likely to appear in work situations, and the concomitant increase in muscle co-activation increased the spine stiffness. This increase in stiffness decreased the movement caused by the sudden load. These results show that both abdominal- and back muscles may have an important role in stabilising the spine, and in decreasing movements caused by sudden loads likely to appear in numerous work