Factors in breathing maneuvers that affect trunk electromyogram during manual lifting

Abolition of sagittal T7-T10 dynamics during forced ventilation in AIS patients with Lenke 1A curves

In healthy subjects, respiratory maximal volumes are highly dependent on the sagittal range of motion of the T7-T10 segment. In AIS, the abolition of T7-T10 dynamics related to the stiffness induced by the apex region in Lenke IA curves could harm ventilation during maximal breathing. The aim of this study was to analyze the dynamics of the thoracic spine during deep breathing in AIS patients and in healthy matched controls. This is a cross-sectional, case-control study. 20 AIS patients (18 girls, Cobb angle, 54.7 ± 7.9°; Risser 1.35 ± 1.2) and 15 healthy volunteers (11 girls) matched in age (12.5 versus 15.8 years mean age) were included. In AIS curves, the apex was located at T8 (14) and T9 (6). Conventional sagittal radiographs of the whole spine were performed at maximal inspiration and exhalation. The ROM of each spinal thoracic functional segment (T1-T7, T7-T10, T10-T12) and the global T1-T12 ROM were measured. In healthy subjects, the mean T1-T12 ROM during forced breathing was 16.7 ± 3.8. AIS patients showed a T1-T12 ROM of 1.1 ± 1.5 (p < 0.05), indicating a sagittal stiffness of the thoracic spine. A wide T7-T10 ROM (15.3 ± 3.0) was found in healthy controls (91.6% of the T1-T12 ROM). AIS patients showed only 0.4 ± 1.4 ROM at T7-T10 (36.4% of the T1-T12 ROM) (p < 0.001). There was a linear relationship between the magnitude of T7-T10 kyphosis in maximal exhalation and both FVC (% of predicted FVC) and FEV1. In conclusion, Lenke 1A AIS patients show a restriction of the thoracic spine motion with an almost complete abolition of T7-T10 ROM, a crucial segment for deep breathing. T7-T10 stiffness could explain the ventilatory limitations found in AIS patients.

Non-uniform Segmental Range of Motion of the Thoracic Spine During Maximal Inspiration and Exhalation in Healthy Subjects

Background and Objective: To analyse the range of motion of the thoracic spine by radiographically measuring changes in the sagittal profile of different thoracic segments during maximal inspiration and exhalation. The starting hypothesis was that forced deep breathing requires an active, but non-uniform widening of the lordotic–kyphotic range of motion of the different thoracic segments.

Methods: Cross-sectional study. Participants were 40 healthy volunteers aged 21–60. Conventional anteroposterior and functional sagittal chest radiographs were performed during maximal inspiration and exhalation. The range of motion of each spinal thoracic functional segment, global T1–T12 motion, and the sagittal displacement of the thoracic column during breathing were measured. Considering the different type of ribs and their attachment the spine and sternum, thoracic segments were grouped in T1–T7, T7–T10, and T10–T12. The displacement of the thoracic spine with respect to the sternum and manubrium was also recorded.

Results: The mean difference from inspiration to exhalation in the T1–T12 physiologic kyphosis was 15.9° ± 4.6°, reflecting the flexibility of the thoracic spine during deep breathing (30.2%). The range of motion was wider in the caudal hemicurve than in the cranial hemicurve, indicating more flexibility of the caudal component of the thoracic kyphosis. A wide range of motion from inspiration to exhalation was found at T7–T10, responsible for 73% of T1–T12 sagittal movement. When the sample was stratified according to age ranges (20–30, 30–45, and 45–60 yr.), none of the measurements for inspiration or exhalation showed statistically significant differences.

Only changes at this level showed a positive correlation with changes in the global thoracic kyphosis (r = 0.794, p <0.001).

Conclusion: The range of motion of the thoracic spine plays a relevant role in respiration dynamics. Maximal inspiration appears to be highly dependent on the angular movements of the T7–T10 segment.

Variables associated with performance of an active limb movement following within-session instruction in people with and people without low back pain

Modification of a movement pattern can be beneficial in decreasing low back pain (LBP) symptoms. There is variability, however, in how well people are able to modify performance of a movement. What has not been identified is the factors that may affect a person's ability to modify performance of a movement. We examined factors related to performance of active hip lateral rotation (HLR) following standardized instructions in people with and people without LBP. Data were collected during performance of HLR under 3 conditions: passive, active, and active instructed. In people with LBP, motion demonstrated during the passive condition (r = 0.873, P < 0.001), motion demonstrated during the active condition (r = 0.654, P = 0.008), and gender (r = 0.570, P = 0.027) were related to motion demonstrated during the active-instructed condition. Motion demonstrated during the passive condition explained 76% (P < 0.001) of the variance in motion demonstrated during the active-instructed condition. A similar relationship did not exist in people without LBP. The findings of the study suggest that it may be important to assess motion demonstrated during passive HLR to determine how difficult it will be for someone with LBP to modify the performance of HLR. Prognosis should be worst for those who display similar movement patterns during passive HLR and active-instructed HLR.

The effect of resisted inspiration during an active straight leg raise in pain-free subjects

Alterations of respiratory patterns have been observed in pelvic girdle pain subjects during the active straight leg raise (ASLR). This study investigated how pain-free subjects coordinate motor control during an ASLR when this task is complicated by the addition of a respiratory challenge. 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, breathing with inspiratory resistance (IR) and ASLR+IR. Subjects responded to ASLR+IR with an increase in the motor activation in the abdominal wall and chest wall compared to when ASLR and IR were performed in isolation. Activation of obliquus internus abdominis was greater on the side of the leg lift during the ASLR+IR, in comparison to symmetrical activation observed in the other abdominal wall muscles. The incremental increase of motor activity was associated with greater intra-abdominal pressure baseline shift when lifting the leg during ASLR+IR compared to ASLR. Individual variation was apparent in the form of the motor control patterns, mostly reflected in variable respiratory activation of the abdominal wall. The findings highlight the flexibility of the neuromuscular system in adapting to simultaneous respiratory and stability demands.

Links between the mechanics of ventilation and spine stability

Spine stability is ensured through isometric coactivation of the torso muscles; however, these same muscles are used cyclically to assist ventilation. Our objective was to investigate this apparent paradoxical role (isometric contraction for stability or rhythmic contraction for ventilation) of some selected torso muscles that are involved in both ventilation and support of the spine. Eight, asymptomatic, male subjects provided data on low back moments, motion, muscle activation, and hand force. These data were input to an anatomically detailed, biologically driven model from which spine load and a lumbar spine stability index was obtained. Results revealed that subjects entrained their torso stabilization muscles to breathe during demanding ventilation tasks. Increases in lung volume and back extensor muscle activation coincided with increases in spine stability, whereas declines in spine stability were observed during periods of low lung inflation volume and simultaneously low levels of torso muscle activation. As a case study, aberrant ventilation motor patterns (poor muscle entrainment), seen in one subject, compromised spine stability. Those interested in rehabilitation of patients with lung compromise and concomitant back troubles would be assisted with knowledge of the mechanical links between ventilation during tasks that impose spine loading.

The effects of breath control on maximum force and IAP during a maximum isometric lifting task

BACKGROUND

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.

METHODS

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.

FINDINGS

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).

INTERPRETATION

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.

Bone induction by AdBMP-2/collagen implants

BACKGROUND

Demineralized bone matrix and recombinant human bone morphogenetic protein-2 or 7 (BMP-2 or BMP-7)-containing collagenous matrix have been shown to induce new bone formation in orthotopic and heterotopic sites. We examined the ability of subcutaneous implants of collagen combined with adenoviral vector containing the BMP-2 gene (AdBMP-2) to induce bone formation in rats. We also evaluated whether targeting the AdBMP-2 vector through an alternative receptor pathway, fibroblast growth factor (FGF), would increase the vector's potency.

METHODS

In a time-course study, rat subcutaneous sites were implanted with (1) AdBMP-2 in rat-bone-derived collagen or (2) rat-bone-derived collagen alone. Samples were collected three, seven, fourteen, or thirty-five days after treatment. In a dose-response study, bone induction by AdBMP-2 in collagen (AdBMP-2/collagen) or by AdBMP-2 and FGF2 Fab' anti-adenovirus knob protein antibody in collagen (FGF2-AdBMP-2/collagen) was tested at fourteen days. Viral vector doses of 1 x 10(9) PN (viral particle number), 3 x 10(9) PN, 1 x10(10) PN, 3 x 10(10) PN, or 1 x 10(11) PN per implant were used. Equal amounts of collagen (25 mg) were used to formulate all implants. Explanted tissues were evaluated histologically to determine bone formation, specific activity of alkaline phosphatase, and calcium content.

RESULTS

AdBMP-2/collagen implants induced robust bone formation. New bone was formed by the fourteenth day after implantation. In contrast, little or no bone was induced by the implant containing collagen alone. FGF2-AdBMP-2/collagen implants stimulated significantly more bone formation (p < 0.05) than did AdBMP-2/collagen implants, regardless of the dose of viral particles.

CONCLUSIONS

Local delivery of AdBMP-2 in a collagen matrix rapidly induces bone formation, and targeting the virus through FGF receptors enhances the osteogenic potential of AdBMP-2.