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The European Respiratory Journal Apr 1995In addition to its emerging immunodulatory properties, theophylline is a bronchodilator and also decreases mean pulmonary arterial pressure in vivo. The mechanism of... (Review)
Review
In addition to its emerging immunodulatory properties, theophylline is a bronchodilator and also decreases mean pulmonary arterial pressure in vivo. The mechanism of action of this drug remains controversial; adenosine antagonism, phosphodiesterase (PDE) inhibition and other actions have been advanced to explain its effectiveness in asthma. Cyclic adenosine monophosphate (AMP) and cyclic guanosine monophosphate (GMP) are involved in the regulation of smooth muscle tone, and the breakdown of these nucleotides is catalysed by multiple PDE isoenzymes. The PDE isoenzymes present in human bronchus and pulmonary artery have been identified, and the pharmacological actions of inhibitors of these enzymes have been investigated. Human bronchus and pulmonary arteries are relaxed by theophylline and by selective inhibitors of PDE III, while PDE IV inhibitors also relax precontracted bronchus and PDE V/I inhibitors relax pulmonary artery. There appears to be some synergy between inhibitors of PDE III and PDE IV in relaxing bronchus, and a pronounced synergy between PDE III and PDE V inhibitors in relaxing pulmonary artery. In neither tissue does 8-phenyltheophylline, a xanthine exhibiting adenosine antagonism but not PDE inhibition, cause any significant relaxation, implying that theophylline does not exert its actions through adenosine antagonism. The close correspondence of theophylline concentrations inhibiting bronchus or pulmonary artery PDE and those causing relaxation points towards PDE inhibition as the major mechanism of action of theophylline in smooth muscle relaxation.
Topics: Animals; Bronchi; Bronchodilator Agents; Cyclic AMP; Cyclic GMP; Humans; Muscle, Smooth; Muscle, Smooth, Vascular; Parasympatholytics; Phosphodiesterase Inhibitors; Pulmonary Artery; Theophylline
PubMed: 7664866
DOI: No ID Found -
Medicine and Science in Sports and... Aug 1990Rehabilitation of muscle injuries is directed toward restoration of function, not just relief of symptoms. This philosophy is reflected in the goals of rehabilitation,...
Rehabilitation of muscle injuries is directed toward restoration of function, not just relief of symptoms. This philosophy is reflected in the goals of rehabilitation, which can be stated as 1) establishment of an accurate diagnosis; 2) minimization of deleterious local effects of the acute injury; 3) allowance for proper healing; 4) maintenance of other components of athletic fitness; and 5) return to normal athletic function. The goals fit well into the framework of the tissue injury cycle described earlier in this symposium. Details of the rehabilitation goals and the relationship to the tissue injury cycle will be discussed.
Topics: Anti-Inflammatory Agents, Non-Steroidal; Athletic Injuries; Biomechanical Phenomena; Contusions; Cryotherapy; Hot Temperature; Humans; Muscle Contraction; Muscles; Rest; Sprains and Strains; Weight Lifting
PubMed: 2402205
DOI: No ID Found -
Journal of Neurophysiology Jan 2019We recently developed an approach for recording from muscle spindles in the intrinsic muscles of the foot in freestanding humans by inserting a tungsten microelectrode...
We recently developed an approach for recording from muscle spindles in the intrinsic muscles of the foot in freestanding humans by inserting a tungsten microelectrode into the posterior tibial nerve behind the medial malleolus of the ankle. Here we characterize the behavior of muscle spindles in the small muscles of the foot in 1) seated subjects with the leg horizontal and the foot naturally plantarflexed and 2) standing subjects. In the first study, recordings were made from 26 muscle spindle afferents located within flexor digiti minimi brevis ( n = 4), abductor digiti minimi ( n = 3), quadratus plantae ( n = 3), plantar interossei ( n = 4), flexor digitorum brevis ( n = 3), dorsal interossei ( n = 2), and lumbricals ( n = 2), with one each supplying abductor hallucis, adductor hallucis, and flexor hallucis brevis. The identity of another two muscle afferents was unknown. The majority of the units were silent at rest, only seven (27%) being spontaneously active. Because of the anatomic constraints of the foot, some spindles supplying muscles acting on the toes responded to movements of one or more digits. In the second study, 12 muscle spindle afferents were examined during standing. The ongoing discharge of eight spindle afferents covaried with changes in the center of pressure during postural sway. We conclude that the majority of spindle endings in the small muscles of the foot are silent at rest, which may allow them to encode changes in conformation of the foot when it is loaded during standing. Moreover, these muscle spindle afferents can provide useful proprioceptive information during standing and postural sway. NEW & NOTEWORTHY We have characterized the firing properties of muscle spindles in the intrinsic muscles of the human foot for the first time. The majority of the spindle endings are silent in seated subjects, and most fire tonically during standing, their discharge covarying with center of pressure during postural sway. We conclude that spindle endings in the intrinsic muscles of the foot provide useful proprioceptive information during free standing.
Topics: Adolescent; Adult; Female; Foot; Humans; Male; Muscle Spindles; Posture; Rest; Weight-Bearing; Young Adult
PubMed: 30427762
DOI: 10.1152/jn.00539.2018 -
Journal of Applied Physiology... Feb 2021In 11 healthy adults (25 ± 4 yr; 2 female, 9 male subjects), we investigated the effect of expiratory resistive loaded breathing [65% maximal expiratory mouth...
In 11 healthy adults (25 ± 4 yr; 2 female, 9 male subjects), we investigated the effect of expiratory resistive loaded breathing [65% maximal expiratory mouth pressure (MEP), 15 breaths·min, duty cycle 0.5; ERL] on mean arterial pressure (MAP), leg vascular resistance (LVR), and leg blood flow ([Formula: see text]). On a separate day, a subset of five male subjects performed ERL targeting 65% of maximal expiratory gastric pressure (ERL). ERL-induced expiratory muscle fatigue was confirmed by a 17 ± 5% reduction in MEP ( < 0.05) and a 16 ± 12% reduction in the gastric twitch pressure response to magnetic nerve stimulation ( = 0.09) from before to after ERL and ERL, respectively. From rest to task failure in ERL and ERL, MAP increased (ERL = 31 ± 10 mmHg, ERL = 18 ± 9 mmHg, both < 0.05), but group mean LVR and [Formula: see text] were unchanged (ERL: LVR = 0.78 ± 0.21 vs. 0.97 ± 0.36 mmHg·mL·min, [Formula: see text] = 133 ± 34 vs. 152 ± 74 mL·min; ERL: LVR = 0.70 ± 0.21 vs. 0.84 ± 0.33 mmHg·mL·min, [Formula: see text] = 160 ± 48 vs. 179 ± 110 mL·min) (all ≥ 0.05). Interestingly, [Formula: see text] during ERL oscillated within each breath, increasing (∼66%) and decreasing (∼50%) relative to resting values during resisted expirations and unresisted inspirations, respectively. In conclusion, fatiguing expiratory muscle work did not affect group mean LVR or [Formula: see text] in otherwise resting humans. We speculate that any sympathetically mediated peripheral vasoconstriction was counteracted by transient mechanical effects of high intra-abdominal pressures during ERL. Fatiguing expiratory muscle work in otherwise resting humans elicits an increase in sympathetic motor outflow; whether limb blood flow ([Formula: see text]) and leg vascular resistance (LVR) are affected remains unknown. We found that fatiguing expiratory resistive loaded breathing (ERL) did not affect group mean [Formula: see text] or LVR. However, within-breath oscillations in [Formula: see text] may reflect a sympathetically mediated vasoconstriction that was counteracted by transient increases in [Formula: see text] due to the mechanical effects of high intra-abdominal pressure during ERL.
Topics: Adult; Exhalation; Female; Humans; Male; Muscle Fatigue; Respiratory Muscles; Rest; Vascular Resistance
PubMed: 33356985
DOI: 10.1152/japplphysiol.00116.2020 -
Brazilian Journal of Physical Therapy 2018Individuals with short resting pectoralis minor muscle length have been shown to have aberrant scapulothoracic motion when compared to individuals with long resting...
Pectoralis minor muscle elongation and scapulothoracic motion do not differ in individuals with short versus typical resting pectoralis minor muscle length: a cross-sectional study.
BACKGROUND
Individuals with short resting pectoralis minor muscle length have been shown to have aberrant scapulothoracic motion when compared to individuals with long resting pectoralis minor muscle length. However, the degree to which the pectoralis minor muscle can be lengthened and whether or not scapulothoracic motion differs between individuals with short and typical resting pectoralis minor muscle length is unknown.
OBJECTIVES
To determine if: (1) pectoralis minor muscle elongation (percent pectoralis minor muscle can be actively and passively lengthened beyond resting length), (2) pectoralis minor muscle percent length change during overhead reaching, and (3) scapulothoracic motion during overhead reaching differ between individuals with short and typical resting pectoralis minor muscle length.
DESIGN
Two group comparison.
METHODS
Thirty healthy individuals were placed into a short or typical resting pectoralis minor muscle length group. A caliper was used to measure resting pectoralis minor muscle length and pectoralis minor muscle length during active and passive muscle lengthening. An electromagnetic tracking system was used to measure pectoralis minor muscle length change as well as scapular, humeral, and trunk motion during several arm elevation tasks. Pectoralis minor muscle elongation and length change during arm elevation tasks were compared between groups using independent t-tests. Two-factor mixed-model analyses of variance were used to compare scapulothoracic motion at arm elevation angles of 30°, 60°, 90°, and 120°.
RESULTS
Pectoralis minor muscle elongation and pectoralis minor muscle length change during arm elevation did not differ between groups. Scapulothoracic motion did not differ between groups across arm elevation tasks.
CONCLUSIONS
Although resting pectoralis minor muscle length differed between groups, pectoralis minor muscle lengthening and scapulothoracic motion were similar between participants with short and typical resting pectoralis minor muscle length. Additional studies are needed to better understand the role of pectoralis minor muscle elongation on scapulothoracic motion.
Topics: Cross-Sectional Studies; Humans; Pectoralis Muscles; Rest; Scapula
PubMed: 29914856
DOI: 10.1016/j.bjpt.2018.05.003 -
The American Journal of Physiology May 1959
Topics: Animals; Humans; Mammals; Muscle, Skeletal; Muscles; Relaxation
PubMed: 13649937
DOI: 10.1152/ajplegacy.1959.196.5.1088 -
Magnetic Resonance in Medicine Jul 2020To develop and test real-time MR elastography for viscoelastic parameter quantification in skeletal muscle during dynamic exercises.
PURPOSE
To develop and test real-time MR elastography for viscoelastic parameter quantification in skeletal muscle during dynamic exercises.
METHODS
In 15 healthy participants, 6 groups of lower-leg muscles (tibialis anterior, tibialis posterior, peroneus, extensor digitorum longus, soleus, gastrocnemius) were investigated by real-time MR elastography using a single-shot, steady-state spiral gradient-echo pulse sequence and stroboscopic undersampling of harmonic vibrations at 40 Hz frequency. One hundred and eighty consecutive maps of shear-wave speed and loss angle (φ) covering 30.6 s of total acquisition time at 5.9-Hz frame rate were reconstructed from 360 wave images encoding 2 in-plane wave components in an interleaved manner. The experiment was carried out twice to investigate 2 exercises-isometric plantar flexion and isometric dorsiflexion-each performed over 10 s between 2 resting periods.
RESULTS
Activation of lower-extremity muscles was associated with increasing viscoelastic parameters shear-wave speed and φ, both reflecting properties related to the transverse direction relative to fiber orientation. Major viscoelastic changes were observed in soleus muscle during plantar flexion (shear-wave speed: 20.0% ± 3.6%, φ: 41.3% ± 12.0%) and in the tibialis anterior muscle during dorsiflexion (41.8% ± 10.2%, φ: 27.9% ± 2.8%; all P < .0001). Two of the muscles analyzed were significantly activated by plantar flexion and 4 by dorsiflexion based on shear-wave speed, whereas φ changed significantly in 5 muscles during both exercises.
CONCLUSION
Real-time MR elastography allows mapping of dynamic, nonperiodic viscoelasticity changes in soft tissues such as voluntary muscle with high spatial and temporal resolution. Real-time MR elastography thus opens new horizons for the in vivo study of physiological processes in soft tissues toward functional elastography.
Topics: Elasticity Imaging Techniques; Exercise; Humans; Leg; Muscle, Skeletal; Rest
PubMed: 31774210
DOI: 10.1002/mrm.28095 -
Journal of Strength and Conditioning... Dec 2015Inspiratory muscle training (IMT) strengthens the muscles of respiration, improves breathing efficiency, and increases fitness. The IMT is generally performed...
Inspiratory muscle training (IMT) strengthens the muscles of respiration, improves breathing efficiency, and increases fitness. The IMT is generally performed independently of aerobic exercise; however, it is not clear whether there is added benefit of performing the IMT while simultaneously performing aerobic exercise in terms of activating and strengthening inspiratory muscles. The purpose of our study was to determine the effect of IMT on respiratory muscle electromyography (EMG) activity during stationary cycling in the upright and drops postures as compared with that when the IMT was performed alone. Diaphragm and sternocleidomastoid EMG activity was measured under different resting and cycling postures, with and without the use of the IMT at 40% maximal inspiratory pressure (n = 10; mean age 37). Cycling in an upright posture while simultaneously performing the IMT resulted in a significantly greater diaphragm EMG activity than while performing the IMT at rest in upright or drops postures (p ≤ 0.05). Cycling in drops postures while performing the IMT had a significantly greater diaphragm EMG activity than when performing the IMT at rest in either upright or drops postures (p ≤ 0.05). Sternocleidomastoid muscle activity increased with both cycling and IMT, although posture had little effect. These results support our hypothesis in that the IMT while cycling increases respiratory EMG activity to a significantly greater extent than when performing the IMT solely at rest, suggesting that the combination of IMT and cycling may provide an additive training effect.
Topics: Abdominal Muscles; Adult; Bicycling; Breathing Exercises; Diaphragm; Electromyography; Exercise; Female; Humans; Male; Middle Aged; Posture; Rest; Young Adult
PubMed: 26584054
DOI: 10.1097/JSC.0000000000000238 -
Proceedings of the Royal Society of... Mar 1956
Topics: Humans; Mental Disorders; Muscles; Relaxation
PubMed: 13420148
DOI: 10.1098/rspb.1957.0011 -
Magnetic Resonance Imaging Nov 2023T2 relaxation times (T2 times) are different between resting and exercised muscles and between muscles of healthy subjects and subjects with muscle pathology. However,...
T2 relaxation times (T2 times) are different between resting and exercised muscles and between muscles of healthy subjects and subjects with muscle pathology. However, studies specifically focusing on neck muscles are lacking. Furthermore, normative neck muscle T2 times are not well defined and methodology used to analyse T2 times in neck muscles is not robust. We analysed T2 times in key neck muscles and explored factors affecting variability between muscles. 20 healthy subjects were recruited. Two circular regions of interest (ROIs) were drawn in two mutually exclusive regions within neck muscles on T2 weighted images and values averaged. ROI measurements were performed by a co-investigator, supervised by a neuro-radiologist. For the first ten subjects, measurements were done from C1-T1. For the remaining subjects, ROIs were drawn at two pre-determined levels. Two MRIs were repeated at 31 degrees acquisition to evaluate the effect of muscle fibre orientation. ROI values were translated into T2 times. Results showed semispinalis capitis had the longest T2 times (range 46.88-51.42 ms), followed by splenius capitis (range 47.37-48.33 ms), trapezius (range 45.27-47.46 ms), levator scapulae (range 43.17-45.63 ms) and sternocleidomastoid (range 38.45-42.91 ms). T2 times did not vary along length of muscles and were unaffected by muscle fibre orientation (P > 0.05). T2 times of splenius capitis correlated significantly with age at C2/C3 and C5/C6 levels and trapezius at C7/T1 level. Gender did not influence relaxation times (P > 0.05). In conclusion, results of normative neck muscle T2 time values and factors influencing the T2 times could serve as a reference for future MR analysis of neck muscles. The methodology used may also be useful for related studies of neck muscles.
Topics: Humans; Neck Muscles; Magnetic Resonance Imaging; Rest; Healthy Volunteers
PubMed: 37517766
DOI: 10.1016/j.mri.2023.07.013