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Modified neck muscular system of the giraffe (Giraffa camelopardalis).

The muscular and skeletal systems of the long neck were morphologically examined in order to clarify their modification and their functional significance in the giraffe (Giraffa camelopardalis). The longissimus, the thoracic and cervical, spinalis and semispinalis, the cranial and caudal head oblique, and the multifidus muscles, and the nuchal ligament were observed at their origin and insertion. The atlas, axis, and the third cervical vertebra were measured and examined. The modified spinous processes provided the large attachment surface for the strong nuchal ligament and for the muscles of the axis and other cervical vertebrae, while the muscle tendons had their origin in the ventrocaudally-enlarged transverse process. It is concluded that the modified muscles with their expanded belly and tendon have the functions of occupying the interspace among long vertebrae, and also of supporting the head and neck by means of their wide attachment to the altered vertebral processes.

Animals↗

[Dorsal and lumbar paraspinal electromyographic study. Multi-MUP analysis and drawing up normal values in a reference population].

OBJECTIVE: The aim of this study was to contribute to draw up reference values relating to electromyographic (EMG) parameters in dorsal and lumbar paraspinal muscles. MATERIALS AND METHODS: 75 healthy subjects without back pain underwent electromyography of multifidus bundles, which are innervated uni-segmentally by the dorsal ram of the spinal nerve. T8, L3, L4, L5 and S1 myotomes were systematically explored. Output variables were spontaneous denervation activity and quantitative EMG data obtained by multi-MUP (Motor Unit action Potential) analysis. RESULTS: No abnormal insertional or spontaneous activity (such as fibrillation, positive sharp waves or fasciculation) was recorded at rest. Neither sex nor age influenced motor unit action potential features in our series. Reference values were drawn up for T8 and L5 segmental levels using the mean values of 20 motor unit potentials in each patient studied, the reference interval being defined by the lower and the upper outlier limits on individual values. CONCLUSION: This study offers reference data to electromyographers to help better identifying possible myogenic or neurogenic pathological changes, especially in lumbosacral radiculopathies.

Adult↗

Neuromuscular disorders associated with static lumbar flexion: a feline model.

Static flexion of the lumbar spine with constant load applied to the viscoelastic structures for 20 minutes and for 50 minutes resulted in development of spasms and inhibition in the multifidus muscles (e.g., deep erector spinae) and in creep of the supraspinous ligament in the feline model. The development of spasms and inhibition was not dependent on load magnitude. It is suggested that occupational and sports activities which require prolonged static lumbar flexion within the physiological range can cause a "sprain"-like injury to the ligaments, which in turn reflexively induce spasms and inhibition in some erector spinae muscles. Such disorder may take a long time to recover, in the order of days to weeks, depending on the level of creep developed in the tissues.

Animals↗

Sensorimotor control of the spine.

The spinal viscoelastic structures including disk, capsule and ligaments were reviewed with special focus on their sensory motor functions. Afferent capable of monitoring proprioceptive and kinesthetic information are abundant in the disc, capsule and ligament. Electrical stimulation of the lumbar afferents in the discs, capsules and ligaments seem to elicit reflex contraction of the multifidus and also longissimus muscles. The muscular excitation is pronounced in the level of excitation and with weaker radiation 1 to 2 levels above and below. Similarly, mechanical stimulation of the spinal viscoelastic tissues excites the muscles with higher excitation intensity when more than one tissue (ligaments and discs for example) is stimulated. Overall, it seems that spinal structures are well suited to monitor sensory information as well as to control spinal muscles and probably also provide kinesthetic perception to the sensory cortex.

Afferent Pathways↗

Extrapolation of time series of EMG power spectrum parameters in isometric endurance tests of trunk extensor muscles.

The aim of the present study was to test the viability of using short isometric contractions of trunk extensor muscles to perform an assessment of their endurance capacity. To this aim two types of analysis were performed. First, electromyographic (EMG) mean power frequency (MPF) slopes with respect to time as estimated over shorter fixed periods were compared to slopes estimated over the full contraction period of a contraction sustained until the endurance time. Second, the relationship between MPF slope estimates as estimated over various periods and the endurance time of the muscle group was evaluated. Five subjects performed three isometric trunk endurance tests at 25%, 50% and 75% of their maximum voluntary contraction (MVC), respectively. EMG signals of the left and right multifidus, iliocostalis and longissimus muscles were continuously recorded and spectral parameters were calculated. The MPF appeared to decrease consistently during all endurance tests. The extrapolation from a MPF time series of half the estimated contraction period to the time series of the complete contraction period gave reasonable results at all force levels, when data from several electrode locations were incorporated in a single slope estimate (mean or steepest slope). The accuracy of the prediction of trunk extensor endurance on the basis of these parameters describing the MPF time series over half the estimated contraction period was satisfactory. Endurance time predictions from yet shorter periods were unreliable.

Adult↗

Reliability of electromyographic and torque measures during isometric axial rotation exertions of the trunk.

OBJECTIVE: The aim of the present study was to investigate the between-days reliability of electromyographic (EMG) measurement of 6 bilateral trunk muscles and also the torque output in 3 planes during isometric right and left axial rotation at different exertion levels. METHODS: Ten healthy subjects performed isometric right and left axial rotation at 100, 70, 50 and 30% maximum voluntary contractions in two testing sessions at least 7 days apart. EMG amplitude and frequency analyses of the recorded surface EMG signals were performed for rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum and multifidus bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were measured. RESULTS: For both EMG amplitude and frequency values, good (intraclass correlation coefficient, ICC=0.75-0.89) to excellent (ICC>/=0.90) reliability was found in the 6 trunk muscles at different exertion levels during axial rotation. The reliability of both maximal isometric axial rotation torque and coupling torques in sagittal and coronal planes were found to be excellent (ICC>/=0.93). CONCLUSIONS: Good to excellent reliability of EMG measures of trunk muscles and torque measurements during isometric axial rotation was demonstrated. This provides further confidence of using EMG and triaxial torque assessment as outcome measures in rehabilitation and in the evaluation of the human performance in the work place.

Abdominal Muscles↗

Endometriosis is associated with central sensitization: a psychophysical controlled study.

Endometriosis is a pain syndrome representing a major cause of pelvic pain in women of reproductive age. The aim of this study was to test the hypothesis that persistent nociceptive input from endometriotic tissues leads to central sensitization manifested by somatic hyperalgesia and increased referred pain areas to experimental saline-induced muscle pain in patients with endometriosis, compared to healthy control subjects. Ten women with laparoscopically confirmed endometriosis and 10 healthy, age-matched women participated in the study. Hypertonic saline (0.5 mL, 5.8%) was injected intramuscularly, in random succession, into 1 site of menstrual pain referral (the multifidus muscle at the low back) and into 1 non-pain control site (first dorsal interosseous muscle [FDI] of the hand). The post-saline pain intensity and pain areas at the FDI were significantly greater in patients with endometriosis than in control subjects (P <.05) but were not different between the groups for the back. An absence of enhancement of post-saline pain responses at the back in the endometriosis group suggests that saline-induced pain at the back appears to activate segmental inhibitory systems in patients with endometriosis. Manifestation of central sensitization in women with endometriosis is demonstrated by increased muscle nociceptor input in the form of increased post-saline pain intensity, pain areas at the FDI, and hypersensitivity to pressure stimulation. These findings provide new insights into the complex pain mechanisms associated with endometriosis.

Adult↗

Skip laminectomy--a new treatment for cervical spondylotic myelopathy, preserving bilateral muscular attachments to the spinous processes: a preliminary report.

BACKGROUND CONTEXT: Techniques in current use for expansive laminoplasty operations (ELAP) on the cervical spine damage the extensor mechanisms, resulting in restriction of neck motion, loss of lordosis and persistent axial pains. PURPOSE: This article introduces a new surgical technique called skip laminectomy, which reduces morbidity after decompression of the cervical spinal canal. STUDY DESIGN/SETTING: A prospective study is presented of all patients with multilevel cervical spondylotic myelopathy (CSM), treated by this new procedure between December 1998 and March 2000. PATIENT SAMPLE: Since December 1998, 61 patients with CSM have undergone the procedure, of whom 24 (13 men and 11 women) were selected for this study. Follow-up periods ranged from 12 to 25 months, with an average of 18 months. Average age at operation was 69 years (range, 50 to 82 years). Eighteen patients with CSM on whom C3-C7 open-door laminoplasties had been performed by the author before 1998 were selected as controls for study of postoperative atrophy of the deep extensor cervical muscles. There were 11 men and 7 women, average age 67 years (range, 45 to 81). OUTCOME MEASURES: Axial symptoms and Japanese Orthopaedic Association (JOA) scores were recorded. Pre- and postoperative ranges of neck motion were measured on lateral flexion and extension radiographs. Pre- and postoperative cervical curvature indexes were calculated according to Ishihara's method. For quantitative analysis of damage to the posterior cervical muscles, atrophy rates were calculated from cross-sectional areas of the deep extensor muscles on the pre- and postoperative axial magnetic resonance imaging. METHODS: In skip laminectomy, standard laminectomies are performed at selected levels, combined with partial laminectomies of the cephalad halves of laminae at other selected levels, where the muscular attachments to the spinous processes are left undisturbed. Instead of a standard laminectomy, an interlaminar decompression can be performed at levels where the anterior spinal cord compression is insignificant. It is accomplished by simply removing the cephalad half of the inferior lamina and ligamentum flavum without detaching the semispinalis cervicis and multifidus muscles from the adjacent spinous processes. RESULTS: Using JOA scores, the average recovery rate was 61.0%. None of the patients complained of persistent axial symptoms. The postoperative range of flexion-extension motion averaged 97% of the preoperative measures. The cervical curvature index was reduced in 1 of the 24 patients. The atrophy rate of the deep extensor muscles after skip laminectomy was 20% of that seen after open-door laminoplasty. CONCLUSIONS: Skip laminectomy for cervical spinal canal decompression is less invasive than conventional laminectomy and ELAP. It is effective in preventing postoperative problems, such as persistent axial symptoms, restriction of neck motion and loss of cervical lordosis.

Aged↗

Rates of muscle protein synthesis in paraspinal muscles: lateral disparity in children with idiopathic scoliosis.

1. The rate of paraspinal (multifidus) muscle protein synthesis was measured bilaterally at the top, apex and bottom of the thoracic curve in nine children with an idiopathic scoliosis, using the stable-isotope-labelled amino acid L-[1-13C]leucine. 2. No significant difference was observed in rates of muscle protein synthesis between the two sides of the spine, at the levels of the first vertebrae in neutral alignment at the top and bottom of the curve. However, in every patient, at the apex of the spinal curve, synthesis was higher on the convexity than on the concavity (0.077 +/- 0.04 %/h convex, 0.052 +/- 0.02 %/h concave, mean +/- SD, P less than 0.01). 3. Muscle RNA activity (microgram of protein synthesized h-1 microgram-1 of RNA) was lower at the curve apices on the concave than the convex side (0.019 +/- 0.09 microgram h-1 microgram-1 convex apex, 0.016 +/- 0.06 microgram h-1 microgram-1 concave apex, P less than 0.05). Activities were similar on the two sides at the top and bottom of the curve. 4. Differences in muscle histology between the two sides were also observed only at the apex, with a lower type I fibre diameter (50.9 +/- 8.5 micron convex, 38.3 +/- 2.4 microns concave, P less than 0.05) and a lesser proportion of type I fibres (63 +/- 12% convex, 49 +/- 9% concave, P less than 0.05) on the concavity. 5. The results are consistent with effects on muscle protein turnover secondary to an increased muscle contractile activity on the curve convexity and functional immobilization of the muscle on the curve concavity.

Adolescent↗

Muscle activation in therapeutic exercises to improve trunk stability.

OBJECTIVE: To evaluate the relative activation amplitudes from 3 abdominal and 2 trunk extensor muscle sites in healthy subjects performing the pelvic tilt, abdominal hollowing, and level 1 of the trunk stability test (TST level 1) exercises and to compare the activation amplitudes among muscle sites and exercises. DESIGN: Prospective comparative study. SETTING: Motion Analysis Research Center, Dalhousie University, Canada. PARTICIPANTS: Twenty-four healthy men (mean age, 30 +/- 8.1 yr [SD]) without low back pain. INTERVENTIONS: Subjects performed 3 exercises in a balanced order, repeating each exercise 5 times while surface electromyography (EMG) was recorded from the 5 muscle sites. Exercises were divided into 2 phases: movement and stabilization. The root-mean-square amplitude of the EMG for each phase was calculated and normalized to the maximal voluntary isometric contraction (MVIC) amplitude for each muscle. A 2-factor repeated-measures analysis of variance (ANOVA) tested the muscle by exercise interaction and the main effects for each phase separately. MAIN OUTCOME MEASURES: Normalized activation amplitude was the main dependent variable. Ensemble-average curves were calculated to examine the phasing of activation. RESULTS: ANOVA showed a statistically significant interaction (p < .05) for both phases, indicating the 3 exercises recruited the 5 muscle sites using different patterns of relative activation. The external oblique (EO) muscle site was activated to higher amplitudes than the other 4 sites in all 3 exercises for both phases. The highest activity was recorded from the EO during the pelvic tilt, just more than 25% of MVIC. The only exercise to recruit the erector spinae to significantly higher amplitudes than the multifidus site was the TST level 1. CONCLUSIONS: Study exercises were not interchangeable for the patterns of trunk muscle activation amplitudes. The exercises did not recruit the abdominal muscles to adequate levels for strengthening for this healthy sample; however, all 5 muscle sites were activated, forming the basis of a stabilizing exercise approach.

Abdominal Muscles↗

Back and abdominal muscle function during stabilization exercises.

OBJECTIVES: To assess the paraspinal and abdominal muscle activities during different therapeutic exercises and to study how load increment produced by varying limb movements and trunk positions could affect these muscle activities. DESIGN: A cross-sectional study comparing muscle activities between men and women. SETTING: Rehabilitation clinic in university hospital. PARTICIPANTS: Twenty-four healthy volunteers (14 women, 10 men) aged 21 to 39 years. INTERVENTIONS: Subjects performed 16 different therapeutic exercises commonly used to treat low back pain. MAIN OUTCOME MEASURES: Surface electromyography was recorded from the paraspinal (T9, L5) and abdominal (rectus abdominis, obliquus externus) muscles during these exercises. Average electromyographic amplitudes obtained during the exercises were normalized to the amplitude in maximal voluntary contraction (% MVC) to produce interindividually comparable muscle activity assessments. RESULTS: Mean average normalized electromyographic amplitudes (% MVC) of the exercises were below 50% MVC. At L5 level, the multifidus muscle activities were significantly higher (p <.05) in women than in men, whereas no significant difference was found at T9 level. Similarly, rectus abdominis and obliquus externus activities were significantly higher (p <.001, p <.05) in women than in men. Load increment in hands or unbalanced trunk and limb movements produced higher paraspinal and abdominal muscle activities (p <.05). CONCLUSIONS: Simple therapeutic exercises are effective in activating both abdominal and paraspinal muscles. By changing limb and trunk positions or unbalancing trunk movements, it is possible to increase trunk muscle activities. Women were better able to activate their stabilizing trunk muscles than men; but it is also possible that men, having a much higher degree of strength on maximal contraction, only need to activate a smaller amount of that maximum to perform a similar activity.

Abdominal Muscles↗

Muscle activation during exercises to improve trunk stability in men with low back pain.

OBJECTIVES: To evaluate the relative activation amplitudes from 3 abdominal and 2 trunk extensor muscle sites of persons with low back pain (LBP) performing the pelvic-tilt, the abdominal-hollowing, and level 1 of the trunk stability test (TST) exercises and to compare the activation amplitudes among muscle sites and exercises. DESIGN: A prospective, comparative, repeated-measures design. SETTING: Motion analysis research laboratory. PARTICIPANTS: Fourteen men with LBP (mean duration, 8y; mean age +/- standard deviation, 39+/-5y). INTERVENTIONS: Subjects performed 3 exercises in random order while surface electromyograms were recorded from 5 muscle sites: lower and upper rectus abdominus, external oblique, erector spinae, and multifidus. The exercises were divided into 2 phases: a movement phase and a stabilization phase. The root-mean-square (RMS) electromyographic amplitude for each phase was calculated and normalized to the highest RMS amplitude from a series of 4 exercises, which attempted to elicit maximal voluntary isometric contractions (MVICs) for each muscle. A 2-factor, repeated-measures analysis of variance (ANOVA) tested the muscle by exercise interaction and the 2 main effects for each phase separately. MAIN OUTCOME MEASURES: Normalized RMS amplitude was the main dependent variable. The ensemble-average profiles for each muscle were calculated to examine the phasing of activation throughout the exercises. RESULTS: The ANOVA revealed a statistically significant muscle-by-exercise interaction (P<.05) for both phases, which showed that the 3 exercises; recruited the 5 muscle sites using different patterns of relative amplitudes. The external oblique muscle site was activated to higher amplitudes than the other 4 muscle sites for all 3 exercises; the highest normalized RMS activity occurred at the external oblique during the pelvic tilt (32% MVIC). The phasic patterns among the 5 muscle sites were not consistent for the TST but were consistent among the 5 sites for the other 2 exercises. CONCLUSIONS: None of the exercises recruited the abdominal muscles to intensities deemed adequate for strengthening. The TST challenges the coordination of muscle activity during the leg-loading task (stabilization phase) as evidenced by changes in amplitudes over the total exercise time for the external oblique site, but not the other 4 sites. All 3 exercises could be used as initial exercises in a dynamic stability progression when low-recruitment amplitudes of specific muscles were the objective but not for strengthening.

Abdominal Muscles↗

Effect of fatigue on torque output and electromyographic measures of trunk muscles during isometric axial rotation.

OBJECTIVES: To examine the changes in torque output resulting from fatigue, as well as changes in electromyographic measures of trunk muscles during isometric axial rotation and to compare these changes between directions of axial rotation. DESIGN: Subjects performed fatiguing right and left isometric axial rotation of the trunk at 80% of maximum voluntary contraction while standing upright. SETTING: A rehabilitation center. PARTICIPANTS: Twenty-three men with no history of back pain. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Surface electromyographic signals were recorded from 6 trunk muscles bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were also measured. RESULTS: During the fatiguing axial rotation contraction, coupling torques of both sagittal and coronal planes were slightly decreased and no difference was found between directions of axial rotation. Decreasing median frequency and an increase in electromyographic amplitude were also found in trunk muscles with different degrees of changes in individual muscles. There were significant differences (P<.05) between right and left axial rotation exertions in median frequency slope of external oblique, internal oblique, latissimus dorsi, and iliocostalis lumborum muscles, but no such difference was found in median frequency slope of rectus abdominis and multifidus muscles. This could be attributed to different functional roles among the muscles. Similar differences (P<.05) between right and left axial rotation in median frequency slope were also detected in the electromyographic amplitude slope of the trunk muscles. Coefficient of variation of the torque output and electromyographic activation in most of the trunk muscles increased during the fatigue process. CONCLUSION: The changing coupling torque, different fatigue rate, and activation changes of trunk muscles, as well as the increase in variability during fatiguing axial rotation exertion, could affect the internal loading and stability of the spine; this needs to be further quantified in future studies.

Abdominal Muscles↗

Muscle control-pain control. What exercises would you prescribe?

A very specific type of exercise has been devised which is proving to provide effective pain relief for chronic and recurrent back pain sufferers. The exercise approach focuses on retraining a precise co-contraction pattern of the deep trunk muscles, the transversus abdominis and lumbar multifidus. The approach is based on the knowledge of how muscles provide stability for the spine in normal situations. It has been further developed according to research evidence which has demonstrated dysfunction in the deep trunk muscles in patients with back pain. The mechanism for pain relief with this specific exercise approach is believed to be through enhanced stability of the lumbar spine segments.

Journal Article↗

Intra-operator and inter-operator reliability of surface electromyography in the clinical evaluation of back muscles.

As a prerequisite to the use of a test battery based on electromyographic (EMG) analysis of the paraspinal muscles for identifying and remedying back muscle dysfunction, the intra- and inter-operator reliability was assessed. Fifteen volunteers underwent EMG tests on three occasions. The test subjects were asked to perform 22 exercises, subdivided into four categories: coordination, stabilization, balance and strength exercises. The time interval between the tests was one week. The myoelectric signals of the multifidus (MF) and iliocostalis lumborum pars thoracis (ICLT) were analysed with regard to amplitude (averaged EMG) and frequency (zero cross rate). The results indicated that the reliability was better for the MF than for the ICLT, and also for exercises at higher loads (strength exercises). In the intra-operator condition, the reproducibility of the averaged EMG was good (ICC>0.75), except for the balance exercises (ICC = 0.40-0.74). In general, the averaged EMG in the inter-operator condition and the zero cross rate in both the intra- and inter-operator conditions are less or poorly reliable. These results demonstrate that when back muscle function is evaluated during coordination, stabilization and strength exercises, only the averaged EMG parameter has acceptable reproducibility over time when assessed by the same operator.

Adult↗

[Evaluation of specific stabilizing exercise in the treatment of low back pain and lumbar disk disease in outpatient rehabilitation].

AIM: The aim of the study was to evaluate the outcome of outpatient rehabilitation in patients with low back pain and lumbar disk disease with a specific stabilizing exercise of the M. multifidus and M. transversus abdominis. METHOD: 99 outpatients admitted to a rehabilitation unit were included in a prospective randomized controlled interventional trial. The interventional group consisted of 50 patients (34 male, 16 female; mean age 41.1 +/- 9.1, range; 21 - 54 years), 49 patients (31 male, 18 female; mean age 37.9 +/- 9.5, range; 19 - 55 years) were in the control group. Outcomes were assessed at the beginning and the end of the treatment and at a three month follow-up with the Oswestry Low Back Pain Disability Questionnaire, the Hannover Functional Ability Questionnaire FFbH-R, the pain scale SES and a numeric rating scale. RESULTS: In both groups there was a significant functional improvement as measured with the Oswestry Score and the FFbH-R. The interventional group showed better values at the end of the treatment. Pain as well could be reduced significantly by the treatment, but no differences were noted between the two groups. CONCLUSION: Outpatient rehabilitation improved functional capacity and pain in both groups. Advantages could be seen in the interventional group concerning functional status. The specific stabilizing exercise approach appears to be effective in conservative treatment programs of low back pain and lumbar disk disease.

Adolescent↗

The influence of age on isometric endurance and fatigue is muscle dependent: a study of shoulder abduction and torso extension.

The present study examined differences in isometric muscle capacity between older (55-65 years) and younger (18 - 25 years) individuals. A total of 24 younger and 24 older participants (gender balanced within each group) performed sustained shoulder abductions and torso extensions to exhaustion at 30%, 50% and 70% of individual maximal voluntary contraction (MVC). Along with endurance time, manifestations of localized fatigue were determined based on changes in surface electromyographic signals obtained from the shoulder (middle deltoid) and the torso (multifidus and longissimus thoracis) muscles. Strength recovery was monitored using post-fatigue MVCs over a 15-min period. Compared to the younger group, older individuals exhibited lower muscular strength, longer endurance time and slower development of local fatigue. Age effects on fatigue were typically moderated by effort level, while effects of gender appeared to be marginal. Non-linear relationships between target joint torque and endurance time were observed, with effects of age differing between shoulder abduction and torso extension. Overall, the effects of age on endurance and fatigue were more substantial and more consistent for the shoulder muscle than for the torso muscles and were likely related to differences in muscle fibre type composition. For strength recovery rates, no significant age or gender effects were found in either experiment. In summary, this study suggests that differences in isometric work capacity do exist between older and younger individuals, but that this effect is influenced by effort level and the muscle tested.

Adult↗

Spectral analysis of erector spinae EMG during intermittent isometric fatiguing exercise.

The applicability of EMG spectral analysis in the study of muscular fatigue of the erector spinae muscle was investigated. At three locations (L1, L2, L5) of the erector spinae muscle, representing different functional parts, EMG was sampled during fatiguing intermittent isometric extension of the trunk. The multifidus muscle (L5) appeared to show the most consistent changes of the EMG power spectrum as a consequence of fatigue. Whether the effects of the increase in muscle temperature on the power spectrum could be eliminated by low-pass filtering the data (60 Hz and 40 Hz) was also investigated. It was expected that this would make it possible to detect better the effects of fatigue on the firing characteristics of the motorunits by the inherent changes in the power spectrum. Low-pass filtering did not cause a more significant trend of the median frequency of the power spectrum. Future research will have to explore which parts of the power spectrum are affected by an increase of the muscle temperature.

Adult↗