Biomedical subjects

Marco Bonifazi

Publications and source records attributed to Marco Bonifazi.

7 recordsLinked to original sources

PubMed2007

Adaptive changes in postural strategy selection in chronic low back pain.

Chronic low back pain (CLBP) patients achieve postural stability during challenging stance conditions by increasing sway speed. We investigated the mechanisms underlying this behavior, and whether postural strategy selection may be influenced by short-term experience of postural perturbation. Thirteen CLBP patients and thirteen age-matched controls underwent posturography tests. Subjects were asked to stand quietly: (a) with eyes open and eyes closed, and (b) while expecting a series of four backward translations of the support surface. Data from condition (a) was subjected to sway density analysis (SDA). This computes the number of consecutive spaces and respectively time samples during which center of pressure (COP) displacements remained inside a 2.5 mm radius. Three parameters of this analysis were considered: the mean number of peaks (MP), reflecting the time spent by COP in regions of stability, the mean time between peaks (MT) relating to the rate of production of posturographic commands, and the mean spatial distance (MD), reflecting the distance between stable regions. In condition (b) the mean COP positions were analyzed during the time (500 ms) preceding each translation. The MD was significantly increased in the CLBP group as compared to controls (P < 0.01), while the MP and MT did not present any significant difference. The expectation of backward translations initially produced a different COP positioning between the two groups (P < 0.0001) which decreased with repetition of platform translations (controls: PDelta1-4 < 0.002; patients: PDelta1-4 < 0.005). The findings show that the timing and the rate of the balance motor commands is comparable between the two groups. On the other hand, there is greater distance between regions of stability in the patient group. Such modification of motor control patterns might be the consequence of a reweighting of sensory input, possibly due to a deterioration of its reliability. Platform translation findings show that both groups aimed at optimizing their posture selection strategy based on prior testing experience. CLBP patients make use of a different postural motor strategy to maintain quiet stance. This is probably the consequence of an imprecise internal estimate of body sway, due to reduced accuracy in the sensory integration process.

Adaptation, Physiological↗

PubMed2006

Changes in salivary cortisol and corticosteroid receptor-alpha mRNA expression following a 3-week multidisciplinary treatment program in patients with fibromyalgia.

The aim of the present study was to investigate the effects of a 3-week residential multidisciplinary non-pharmacological treatment program (including individually prescribed aerobic exercise and cognitive-behavioral therapy) on fibromyalgia symptoms and hypothalamic-pituitary-adrenal (HPA) axis function. Salivary and venous blood samples were collected from 12 female patients with fibromyalgia (age: 25-58) the day before and the day after the treatment period: saliva, eight times (every two hours from 0800 to 2200 h); venous blood, at 0800 h. Peripheral blood mononuclear cells (PBMC) were separated and analyzed for glucocorticoid receptor-alpha (GR-alpha) mRNA expression by semi-quantitative RT-PCR, while the salivary cortisol concentration was determined by RIA. At the same time, pain and aerobic capacity were evaluated. Aerobic capacity improved at the end of the treatment program. The slope of the regression of salivary cortisol values on sampling time was steeper in all patients after treatment, indicating that the cortisol decline was more rapid. Concomitantly, the area under the cortisol curve "with respect to increase" (AUC(i)) was higher and there was a significant increase in GR-alpha mRNA expression in PBMC. The number of positive tender points, present pain, pain area and CES-D score were significantly reduced after the treatment, while the pressure pain threshold increased at most of the tender points. Our findings suggest that one of the active mechanisms underlying the effects of our treatment is an improvement of HPA axis function, consisting in increased resiliency and sensitivity of the stress system probably related to stimulation of GR-alpha synthesis by the components of the treatment.

Adult↗

PubMed2006

Sex hormones, central nervous system and pain.

The aim of the present review, which highlights some relationships between sex hormones, the CNS and pain, is to provide reference points for discussion on one of the most intriguing aspects of pain pathophysiology: the presence of sex differences in the response threshold to phasic painful stimuli and in the incidence of chronic pain syndromes. The first part of the review deals with sex steroids and their mechanisms of action. In the second part, the connections between sex steroids, the CNS and pain are illustrated to introduce possible areas of discussion in the study of sex differences in experimental and clinical pain.

Animals↗

PubMed2006

Effects of a high-intensity swim test on kinematic parameters in high-level athletes.

The present study aimed to investigate the effects of a high-intensity swim test among top-level swimmers on (i) the spatial and temporal parameters of both the stroke and the 3-D fingertip pattern and (ii) the mechanical, muscular, and physiological parameters. Ten male international swimmers performed a 4 x 50 m swim at maximal intensity. Isometric arm flexion force with the elbow at 90 degrees (F90 degrees ), EMG signals of right musculus biceps brachii and triceps brachii and blood lactate concentrations were recorded before and after the swim test. Kinematic stroke (stroke length, rate, and velocity) and spatiotemporal parameters of the fingertip trajectory were measured by two underwater cameras during the first and last 50 m swims. After the swim test, F90 degrees and mean power frequencies of the EMG decreased significantly when blood lactate concentration increased significantly, attesting the reaching of fatigue. From the first to the last 50 m, stroke rate, stroke velocity, and temporal parameters of the fingertip trajectory exhibited significant increases although stroke length and spatial fingertip trajectory remained unchanged. General and individual adaptations were observed among the top-level swimmers studied. The present findings could be useful for coaches in evaluating fatigue effects on the technical parameters of swimming.

Adaptation, Physiological↗

PubMed2004

Effects of gonadal steroids on the input-output relationship of the corticospinal pathway in humans.

Most of our knowledge about gonadal steroid effects on the nervous system come from studies of limbic structures, while virtually nothing is known about the action of these hormones on the motor system. We carried out experiments on six healthy volunteer males to determine the threshold and gain of the input-output relationship (i.e. stimulus intensity vs. response size) of the corticospinal motoneurones in relation to the transient increase of gonadal steroids induced by a single intramuscular injection of human chorionic gonadotropin (hCG). The motor cortex was excited by focal transcranial magnetic stimuli and the evoked responses from the first dorsal interosseous (FDI) were recorded with surface electromyographic electrodes. In some experiments, the threshold and recruitment curve of the soleus H reflex were determined to assess the gonadal steroid effects on spinal motoneurones. All the subjects showed a significant decrease of cortical motor threshold concomitant with a significant increase of testosterone and oestradiol plasma concentrations. By contrast, there was no significant change of the slope of the curve expressing the relationship between the intensity of magnetic stimulation and the size of the muscle response. Both the threshold and slope of the H reflex were unaffected by the gonadal steroid levels. Latencies of the maximal FDI response to cortical and cervical magnetic stimulation were also unmodified. We conclude that gonadal steroids are involved in regulating the threshold of corticospinal motoneurones in humans. Our observations confirm that the threshold and gain of corticospinal motoneurones are determined by different neural mechanisms.

Adult↗

PubMed2004

Platelet adhesion and aggregation on polyethylene: effect of exhaustive exercise.

The aim of the present study was to evaluate the effect of an exhaustive exercise on platelet adhesion and aggregation on polyethylene (PE) in relation to changes in plasma cortisol concentration in order to ascertain the effect of physical stress response in the blood-contacting properties of polymeric materials. Twelve healthy sedentary subjects, six males and six females, were studied. Each subject performed an exercise test on a bicycle ergometer at intensity corresponding to 70% VO2 max until exhaustion. One month after the exercise session, each subject participated in a control rest session. In both sessions, blood samples were drawn every 5 min for cortisol, lactate, hemoglobin, and hematocrit determinations and every 15 min for evaluation of platelet adhesion and aggregation. Individual comparisons between the rest and exercise cortisol patterns identified three categories of cortisol responders to exercise: positive responders (C +, showing higher concentrations during exercise than during rest), negative responders (C -, showing lower concentrations during exercise than during rest), and nonresponders (NR, showing similar concentrations during exercise and rest). The results revealed that C + had lower platelet adhesion and aggregation scores during exercise than during rest; moreover C - had higher scores than C + and NR during exercise. The results obtained demonstrated no effects of sex or exercise on either cortisol plasma levels or platelet adhesion and aggregation on PE surface. With regard to cardiovascular risk, the results suggest that exercise favorably affects platelet functions when mechanisms of metabolic adaptation to prolonged muscular work, expressed by a cortisol increase, are activated during exercise.

Blood Platelets↗

PubMed2004

Influences of chemically-induced muscle pain on power output of ballistic upper limb movements.

OBJECTIVE: To analyse the conditioning effects of localised acute muscle pain on power output during ipsi- and contra-lateral ballistic arm extensions. METHODS: Eight male subjects performed right arm (ipsilateral) and left arm (contra-lateral) bench press movements. The power output (and force and velocity) of the concentric phase of movement was measured before and during muscle pain induced by a standardised intramuscular injection of levo-ascorbic acid in the right pectoralis major muscle (prime mover muscle) and in the lateral head of the right triceps brachii muscle (synergist). RESULTS: The power output of ipsi- and contra-lateral arm bench press movements was significantly decreased during pain of the right pectoralis major muscle, but not during pain of the right lateral triceps muscle. The velocity and force were both affected and contributed to the decrease in power output. CONCLUSIONS: Acute muscle pain of a prime mover muscle reduces ipsi- and contra-lateral motor performance of ballistic upper limb extension. This is not a generalised or non-specific inhibitory effect on the motor system, since pain failed to modify motor performance when applied to a synergist, non-prime mover, muscle. A basically bilateral executive cortical plan for ballistic upper limb extension could explain the conditioning effect of muscle pain on both ipsi- and contra-lateral arm. SIGNIFICANCE: The results presented here contributes to the understanding of the conditioning effects of muscle pain on movement performance.

Adult↗