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Biomedical subjects

T Nicolaisen

Publications and source records attributed to T Nicolaisen.

15 recordsLinked to original sources
PubMed1999

Physiological response to submaximal isometric contractions of the paravertebral muscles.

STUDY DESIGN: Brief (30-second) isometric trunk extensions at 5%, 20%, 40%, 60%, and 80% of maximal voluntary contraction (MVC) and 3 minutes of prolonged trunk extension (20% MVC) in erect position were studied in nine healthy male subjects. OBJECTIVES: To investigate the intercorrelation between intramuscular pressure and tissue oxygenation of the paravertebral muscles during submaximal isometric contractions and further, to evaluate paravertebral electromyogram and intramuscular pressure as indicators of force development. SUMMARY OF BACKGROUND DATA: Local physiologic responses to muscle contraction are incompletely understood. METHODS: Relative oxygenation was monitored with noninvasive near-infrared spectroscopy, intramuscular pressure was measured with a transducer-tipped catheter, and surface electromyogram was monitored at three recording sites. RESULTS: The root mean square amplitudes of the paravertebral electromyogram (L4, left and right; T12, right) and intramuscular pressure measured in the lumbar multifidus muscle at L4 increased with greater force development in a curvilinear manner. A significant decrease in the oxygenation of the lumbar paravertebral muscle in response to muscle contraction was found at an initial contraction level of 20% MVC. This corresponded to a paravertebral intramuscular pressure of 30-40 mm Hg. However, during prolonged trunk extension, no further decrease in tissue oxygenation was found compared with the tissue oxygenation level at the end of the brief contractions, indicating that homeostatic adjustments (mean blood pressure and heart rate) over time were sufficient to maintain paravertebral muscle oxygen levels. CONCLUSION: At a threshold intramuscular pressure of 30-40 mm Hg during muscle contraction, oxygenation in the paravertebral muscles is significantly reduced. The effect of further increase in intramuscular pressure on tissue oxygenation over time may be compensated for by an increase in blood pressure and heart rate. Surface electromyogram amplitudes and intramuscular pressure can be used as indicators of paravertebral muscle force.

Adult↗
PubMed1997

Conservative treatment of a partial Achilles tendon rupture with an intratendinous lesion.

The Achilles tendon is a common site of acute and overuse injuries in runners. A case is described here in which the diagnosis of a post-traumatic intratendinous lesion was based on clinical examination and magnetic resonance imaging (MRI), and where conservative treatment was given. After a 6 months follow-up, symptoms as well as the MRI verified that intra-tendinous structural abnormalities had disappeared. This case report demonstrates that conservative treatment may be sufficient to cure Achilles injury with severe structural changes inside the tendon.

Achilles Tendon↗
PubMed1996

Regulation of glucose turnover and hormonal responses during electrical cycling in tetraplegic humans.

To examine the importance of blood-borne vs. neural mechanisms for hormonal responses and substrate mobilization during exercise, six spinal cord-injured tetraplegic (C5-T1) males (mean age: 35 yr, range: 24-55 yr) were recruited to perform involuntary, electrically induced cycling [functional electrical stimulation (FES)] to fatigue for 24.6 +/- 2.3 min (mean and SE), and heart rate rose from 67 +/- 7 (rest) to 107 +/- 5 (exercise) beats/min. Voluntary arm cranking in tetraplegics (ARM) and voluntary leg cycling in six matched, long-term immobilized (2-12 mo) males (Vol) served as control experiments. In FES, peripheral glucose uptake increased [12.4 +/- 1.1 (rest) to 19.5 +/- 4.3 (exercise) mumol.min-1.kg-1; P < 0.05], whereas hepatic glucose production did not change from basal values [12.4 +/- 1.4 (rest) vs. 13.0 +/- 3.4 (exercise) mumol.min-1.kg-1]. Accordingly, plasma glucose decreased [from 5.4 +/- 0.3 (rest) to 4.7 +/- 0.3 (exercise) mmol/l; P < 0.05]. Plasma glucose did not change in response to ARM or Vol. Plasma free fatty acids and beta-hydroxybutyrate decreased only in FES experiments (P < 0.05). During FES, increases in growth hormone (GH) and epinephrine and decreases in insulin concentrations were abolished. Although subnormal throughout the exercise period, norepinephrine concentrations increased during FES, and responses of heart rate, adrenocorticotropic hormone, beta-endorphin, renin, lactate, and potassium were marked. In conclusion, during exercise, activity in motor centers and afferent muscle nerves is important for normal responses of GH, catecholamines, insulin, glucose production, and lipolysis. Humoral feedback and spinal or simple autonomic nervous reflex mechanisms are not sufficient. However, such mechanisms are involved in redundant control of heart rate and neuroendocrine activity in exercise.

Adult↗
PubMed1992

Effect of 5 wk of detraining on epinephrine response to insulin-induced hypoglycemia in athletes.

Long-term endurance-trained subjects are known to have an enhanced capacity to secrete epinephrine. It is, however, unknown to what extent this is a reversible phenomenon, i.e., whether the adrenal medullary secretory capacity is diminished during a period of abstinence from training. Hormonal responses to insulin-induced hypoglycemia were studied in seven endurance-trained young male athletes at the onset and the termination of a 31- to 44-day period of detraining necessitated by a sports injury that required leg casting. During insulin infusion, plasma glucose decreased to a mean range of 2.0-2.1 mM for the two conditions. The epinephrine response to hypoglycemia did not decrease significantly during the 4-6 wk of detraining (P greater than 0.05). Responses of other counterregulatory hormones, i.e., norepinephrine, glucagon, growth hormone, and cortisol, were identical in trained and detrained subjects (P greater than 0.05). Heart rate and blood pressure responses to hypoglycemia were similar in the two conditions (P greater than 0.05). In conclusion, in endurance athletes the enhanced capacity to secrete epinephrine is maintained during 5 wk of detraining.

Adolescent↗
PubMed1990

Traumatic rupture of the ureter.

A case of rupture of the ureter from blunt trauma is described. The clinical signs of trauma to the trunk of the patient were very discrete. The police report made it possible to reconstruct the events of the accident and to propose a mechanism of the injury.

Accidents, Traffic↗
PubMed1986

Two methods for determining trunk extensor endurance. A comparative study.

In the last few years epidemiological surveys have shown correlation between low endurance capacity of the trunk extensors and low back trouble. In this report two methods for the determination of trunk extensor endurance are compared. In method I the fixated subject is lying prone with the cranial border of the iliac crest at the edge of a couch. The endurance time for maintaining the upper part of the body horizontal was measured (max. 240 s). In method II the standing subject performed a horizontal isometric pull on a strain gauge force transducer equivalent to 60% MVC of the trunk extensors. The time until complete exhaustion in the muscles (inability to maintain the preset force level) was determined. The methods were applied to two groups of normal, healthy subjects: 1) 23 female (22-61 years) and 53 male (27-60 years) postmen. 2) 10 male students (20-37 years). The results show that method II is preferable to method I, not least in the field of ergonomics. Method II is easily practicable and does not demand expensive or complicated equipment. Furthermore this method gives reliable results suitable for statistical preparation, and is not influenced by anthropometrical factors.

Adult↗
PubMed1985

Trunk strength, back muscle endurance and low-back trouble.

The strength and endurance of the trunk muscles was studied in relation to the extent of earlier low-back trouble (LBT) in a homogeneous, and occupationally active group. Twenty-four female and 53 male postmen with an occupational seniority of more than 2 years took part in the investigation. The cumulative lifetime prevalence, the one-year and the point prevalence of LBT were 67%, 62%, and 4% in females and 55%, 52%, and 0% in males. The rates are higher than in a representative Danish population 40 years old. Anthropometrical measurements and isometric strength (MVC) in trunk flexors and extensors were recorded. The flexibility of the spine, hip and knee joints, the fingertip-floor distance, and the restricted extension of the knee were evaluated. The isometric endurance in the trunk extensors was measured by two methods: 1) prone with the unsupported trunk in a horizontal position and the legs and hips fixated to a couch; and 2) standing, at 60% MVC. The participants were divided into three groups according to the extent of previous LBT, Group I: LBT to a degree that made work impossible, Group II: LBT experienced but not to such a degree that work was hindered, and Group III: LBT never experienced. The main findings were that the isometric endurance time of the trunk extensors was shorter in group I than in II and III, while the trunk muscle strength, anthropometrical measures and joint flexibility were independent of the persons' earlier low-back episodes. Differences in the distribution of ST and FT muscle fibres are suggested as an explanation of the endurance difference.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗