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PubMed2000

Quantification of pressure relief using interface pressure and tissue perfusion in alternating pressure air mattresses.

OBJECTIVE: To examine whether the interface pressure (IP) relief provided by alternating pressure air mattresses (APAMs) is matched with maintenance of tissue perfusion over the points of contact by measuring transcutaneous oxygen and carbon dioxide (tcPO2, tcPCO2). DESIGN: Comparative analysis of 2 APAMs with a 2-parameter continuous time-based method for quantifying pressure relief (PR) and transcutaneous gas measurement for assessing tissue perfusion. SETTING: Rehabilitation research facility in a university hospital. PARTICIPANTS: Eleven able-bodied adult postgraduate student volunteers. MAIN OUTCOME MEASURES: Two full-replacement APAM systems were used. For each mattress the mean maximum and minimum interface pressures; mean peak air pressures in the mattresses; interface pressure durations below 30, 20, and 10 mmHg over a 60-minute period; mean maximum tcPCO2 and minimum tcPO2; and mean area under the tcPO2 and tcPCO2 curves were measured for each subject. RESULTS: IP on the sacrum was held below thresholds of 30, 20, and 10 mmHg longer on a 2-cell, low pressure system than on a 3-cell, high pressure system (p < .001). Integrated over time, tcPO2 levels also indicated that the 2-cell system retained oxygen levels closer to the unloaded baseline than did the 3-cell system (p < .01). tcPCO2 levels did not rise significantly (p > 0.1) compared with the baseline measurement in both mattresses. CONCLUSIONS: PR was sensitive to the design of the APAM, especially its inflation pressure, cycle time, and inflation sequence. If future trials demonstrate that PR values and transcutaneous blood gas measurements correlate significantly with the clinical incidence of pressure sore formation, then this technique may prove useful in assessing the effectiveness of alternating pressure support surfaces.

Adult↗
PubMed2000

Clinical use of a pronuclear stage score following intracytoplasmic sperm injection: impact on pregnancy rates under the conditions of the German embryo protection law.

The German embryo protection law does not allow embryo selection, but only selection of pronuclear stage (PN) oocytes. Only as many PN oocytes are allowed to be selected as are planned to be transferred. Therefore, a clinically applicable score to assess the quality of PN oocytes would be helpful. A recently published score was used under the conditions of the German embryo protection law in 74 non-selected, consecutive intracytoplasmic sperm injection cycles. Only criteria which could be evaluated at the PN stage were included, i.e. not criteria which could only be assessed after pronuclear membrane breakdown or the first cleavage division. Supernumerary PN oocytes were cryopreserved after selection. A mean PN score of <13 (sum of scores of all selected PN oocytes/number of selected PN oocytes) led to a pregnancy rate of 4%, a mean PN score of > or =13 to a pregnancy rate of 22%. Embryo morphology and cumulative PN were correlated (r = 0.52, P < 0.05). The negative predictive value was 92% at a threshold of 13 for the mean PN score. The use of this and perhaps additional scoring systems of PN stage oocytes might help to offer patients in Germany the transfer of two selected PN oocytes, which would reduce the multiple pregnancy rate.

Adult↗
PubMed1999

Breathing patterns during slow and fast ramp exercise in man.

Breathing frequency (fb), tidal volume (VT), and respiratory timing during slow (SR, 8 W min-1) and fast (FR, 65 W min-1) ramp exercise to exhaustion on a cycle ergometer was examined in seven healthy male subjects. Expiratory ventilation (VE), pulmonary gas exchange (VO2 and VCO2) and end-tidal gas tensions (PET,O2 and PET,CO2) were determined using breath-by-breath techniques. Arterialized venous blood was sampled from a dorsal hand vein at 2 min intervals during SR and 30 s intervals during FR and analysed for arterial plasma PCO2 (PaCO2). PET,CO2 increased with increasing work rates (WRs) below the ventilatory threshold (VT); at WRs > or = 90% VO2,max, PET,CO2 was reduced (P < 0.05) below 0 W values in SR but not in FR.fb and VT were similar for SR and FR at all submaximal WRs, resulting in a similar VE. At exhaustion VE was similar but fb was higher (P < 0.05) and VT was lower (P < 0.05) in SR (fb, 51 +/- 10 breaths min-1; VT, 2590 +/- 590 ml) than in FR (fb, 42 +/- 8 breaths min-1; VT, 3050 +/- 470 ml). The time of expiration (TE) decreased with increasing WR, but there was no difference between SR and FR. The time of inspiration (TI) decreased at exercise intensities > or = VT; at exhaustion, TI was shorter (P < 0.05) during SR (0.512 +/- 0.097 s) than during FR (0.753 +/- 0.100 s). The TI to total breath duration (TI/TTot) and the inspiratory flow (VT/TI) were similar during SR and FR at all submaximal exercise intensities; at VO2,max, TI/TTot was lower (P < 0.05) and VT/TI was higher (P < 0.05) during SR (TI/TTot, 0.473 +/- 0.030; VT/TI, 5.092 +/- 0.377 l s-1) than during FR (TI/TTot, 0.567 +/- 0.050; VT/TI, 4.117 +/- 0.635 l s-1). These results suggest that during progressive exercise, breathing pattern and respiratory timing may be determined, at least at submaximal work rates, independently of alveolar and arterial PCO2.

Adult↗
PubMed1979

[Definition and realization of a microprocessor system for monitoring during artificial ventilation (author's transl)].

A medical application of a microprocessor system is presented. The definition of a system able to control the quality of the respiratory exchanges for a patient submitted to artificial ventilation is given. The measurement system is composed by two rapid analysers of CO2 and O2 (Beckman LB2 and OM 11), a flow meter devices and an airway pressure sensor (Monaghan M 700). The monitoring of the ventilation is based on the determination of FAECO2 simultaneous the determination of FECO2, FIO2, FEO2 and FAEO2 allow, with the sequential entries of the blood gaz values, to calculate: VA/V, D (a--A) CO2, D (A--a) O2, VO2, VCO2 and respiratory quotient. Now, we are working out a system composed by: a microprocessor (Intel 8080) which allows acquisition and treatment of the signals; a peripherical with a key board for the dialogue between the operator and the system; a visual display unit and a printer. Measurements are made on the patient every 13 mn during five respiratory cycles. All the stated above parameters are then computed. When there is a variation of FAECO2, an alarm is triggered, of predeterminated threshold is exceeded. This system simple, not too expensive, not invasive, has been conceived to work on one to four patients.

Carbon Dioxide↗
PubMed2002

A new pedaling design: the Rotor--effects on cycling performance.

PURPOSE: To assess the effects of the Rotor (ROT), a new pedaling system that makes each pedal independent from the other so that cranks are no longer fixed at 180 degrees, on endurance cycling performance. METHODS: Following a randomized design, eight subjects (noncyclists; age (mean +/- SEM): 22 +/- 1 yr; VO(2max): 51.8 +/- 1.0 mL x kg(-1) x min(-1)) performed two bicycle-ergometer tests on separate days, one with the conventional pedaling system (CON) and the other one with ROT. Starting at 75 W, the power output was increased by 25 W at 3-min intervals until volitional exhaustion. Gas exchange parameters and blood lactate were measured for every 3-min interval. RESULTS: At exercise intensities between 60 and 90% VO(2max), delta efficiency (DE) was significantly higher in ROT than in CON (24.4 +/- 1.9% vs 21.1 +/- 1.1%, respectively). CONCLUSIONS: Although more research is needed, especially with trained riders, the Rotor system might improve delta efficiency during endurance cycling. Other performance determinants VO(2max), maximal power output) do not seem to be changed compared with the conventional system.

Adult↗
PubMed2001

Clinical significance of the atrial fibrillation threshold in patients with paroxysmal atrial fibrillation.

AF threshold and the other electrophysiological parameters were measured to quantify atrial vulnerability in patients with paroxysmal atrial fibrillation (PAF, n = 47), and those without AF (non-PAF, n = 25). Stimulations were delivered at the right atrial appendage with a basic cycle length of 500 ms. The PAF group had a significantly larger percentage of maximum atrial fragmentation (%MAF, non-PAF: mean +/- SD = 149 +/- 19%, PAF: 166 +/- 26%, P = 0.009), fragmented atrial activity zone (FAZ, non-PAF: median 0 ms, interquartile range 0-20 ms, PAF: 20 ms, 10-40 ms, P = 0.008). Atrial fibrillation threshold (AF threshold, non-PAF: median 11 mA, interquartile range 6-21 mA, PAF: 5 mA, 3-6 mA, P < 0.001) was smaller in the PAF group than in the non-PAF group. Sensitivity, specificity, and positive predictive value of electrophysiological parameters were as follows, respectively: %MAF (cut off at 150%, 78%, 52%, 76%), FAZ (cut off at 20 ms, 47%, 84%, 85%), AF threshold (cut off at 10 mA, 94%, 60%, 81%). There were no statistically significant differences between the non-PAF and PAF groups in the other parameters (effective refractory period, interatrial conduction time, maximum conduction delay, conduction delay zone, repetitive atrial firing zone, wavelength index), that were not specific for PAF. In conclusion, the AF threshold could be a useful indicator to evaluate atrial vulnerability in patients with AF.

Adult↗
PubMed2005

The effects of chronic aerobic and anaerobic exercises n lymphocyte subgroups.

Exercise is the strongest stress to which the body is ever exposed. The body responds to this stress through a set of physiological changes in its metabolic, hormonal and immunological systems. In this study, responses of the immune system to the long-term aerobic and anaerobic exercises have been investigated. Twenty-four sedentary male university students and officers participated in this study. Subjects were divided into two groups, each consisting of twelve people. Group-1 (age: 25.67 +/- 3.79 years, height: 174.83 +/- 5.15 cm, body mass: 72.17 +/- 8.05 kg) and Group-2 (age: 24.83 +/- 2.89 years, height: 175.3 +/- 6.68 cm, body mass: 70.67 +/- 6.15 kg). After physical examinations of the two groups, resting ECG, respiratory function tests and metabolic tests with the use of the breath by breath method were completed, and anerobic heart rates at the threshold level were determined. The first group was subjected to exercise using Monark ergometry cycles at a heart rate 10% below the threshold level for 8 weeks, 3 days a week, 30 min a day. The second group exercised at a heart rate 10% above the threshold level for 8 weeks, 3 days a week, 20 min a day. Heart rates were checked with the Polar Test during exercises. Pre-exercise (Ep) venous blood samples were taken from each group before their 1st and 24th exercises. Hb (gr), Hct (%), erythrocyte (x10(6)/microl), leukocyte (x10(6)/microl), leukocyte subpopulations (neutrophil, lymphocyte, monocyte, eosinophil, basophil %) and thrombocyte (x10(6)/microl) values were determined. CD3, CD4, CD8, CD19 and CD56 values were determined by Flow Cytometry method using monoclonal antibodies. The chronic effects of exercise were examined through a comparison of Ep blood samples at the 1st exercise with Ep blood samples at the 24th exercise. While the increase in the total leukocyte number was significant (p<0.05) in the first group, increase in the second group was found to be non-significant. When percentiles of leukocyte subpopulations were taken into consideration, changes in the first and second group were found to be non-significant. When lymphocyte subgroups were examined; in the first group a decrease in CD3 and CD4 percentiles to 7% and 12%, respectively (p<0.05) and a 65% increase (p<0.01) in the CD56 value were observed. In the second group a decrease in CD3 and CD4 percentiles to 13% and 17%, respectively (p<0.05) and a 73% increase (p<0.01) in the CD56 value were observed. The Sample-t Test and The Wilcoxon Test were used for statistical analysis.

Adult↗
PubMed1985

Separate control of B lymphocyte early activation and proliferation in response to anti-IgM antibodies.

Resting B cells enter and progress through the G1 phase of the cell cycle in response to low concentrations (1 to 5 micrograms/ml) of anti-IgM antibodies. Commitment to enter S phase requires the presence of a fivefold to 50-fold higher concentration of anti-IgM. These and other results strongly suggest that two separately controlled events are involved in B cell activation. The current studies demonstrate that B cells incubated with high concentrations of anti-IgM from the initiation of culture become independent of additional anti-IgM approximately 10 hr before entry into S phase. We have designated this anti-IgM independent portion of the G1 phase of the cell cycle as G1 beta, whereas the earlier phase is referred to as G1 alpha. Furthermore, low concentrations of anti-IgM are sufficient for progress through early portions of G1 alpha, but high concentrations are required for the last 4 to 8 hr (G1 alpha') if the cells are to go through the rest of the cell cycle. Removal of anti-IgM at any time during G1 alpha causes prompt cessation of the size enlargement that accompanies progress through G1. Such cells retain their size and their relative place in G1 for periods of at least 17 hr and recommence movement through G1 alpha phase when anti-IgM is readded. Thus, B cells may exist in states of partial activation and must possess a mechanism to integrate the amount of stimulatory signal they have received; they enter a commitment period for S phase only when that signal passes some threshold value.

Animals↗
PubMed2005

Pretreatment serum hemoglobin level as a predictive factor of response to neoadjuvant chemotherapy in patients with locally advanced squamous cervical carcinoma: a preliminary report.

OBJECTIVE: The aim of this study was to evaluate the predictive value of pretreatment serum hemoglobin level (Hb) together with a series of clinical and pathological variables available before neoadjuvant chemotherapy in locally advanced squamous cervical cancer. METHODS: The influence on response to neoadjuvant chemotherapy of a series of pretreatment clinico-pathological features: hemoglobin level at diagnosis, age, parity, menopausal status, body mass index, clinical stage, tumor diameter, and nuclear grading were analyzed on 73 patients with locally advanced cervical cancer treated with platinum-based neoadjuvant chemotherapy followed by radical surgery. The relationships between pretreatment variables and response to chemotherapy were assessed in univariate and multivariate settings. A univariate and multivariate logistic regression model was adapted to predict an "optimal" response (pathological complete response or more than 50% reduction in tumoral diameter) or "sub-optimal" response (<50% reduction in tumoral diameter). RESULTS: Seventy-three patients-clinical stage: Ib2: 29 (39.7%) IIa: 22 (30.1%) IIb: 22 (30.1%)-received 3 cycles of platinum-based neoadjuvant chemotherapy followed by type III radical hysterectomy. A complete response to neoadjuvant chemotherapy was significantly associated with higher level of pretreatment hemoglobin (mean 14.0 mg/dl) compared to patients with > or =50% response (12.7 mg/dl) or <50% (11.9 mg/dl) (P = 0.002). At multivariate analysis, Hb level was found to be the most powerful and significantly related factor to response to neoadjuvant chemotherapy. A hemoglobin threshold of 12 mg/dl was able to distinguish between patients-with > or =12 mg/dl-at higher probability to respond to neoadjuvant chemotherapy from the ones at lower probability (hemoglobin level under 12 mg/dl). Patients with a complete response to chemotherapy had a 100% survival compared to 93.1% and 53.8% for patients with responses > or =50% and <50% respectively (P = 0.0001). Patients with a pretreatment hemoglobin level of > or =12 mg/dl showed a survival of 87% compared to 63% for patients with a lower hemoglobin level (P = 0.008). CONCLUSIONS: Pretreatment Hb level showed a prognostic and independent predictive value for response to neoadjuvant chemotherapy in locally advanced cervical cancer. In our preliminary report, performed on a limited sample, a threshold of 12 mg/dl seems to be helpful to distinguish between "optimal" and "non-optimal" response.

Analysis of Variance↗
PubMed1997

Amplitude modulation depth discrimination of a sinusoidal carrier: effect of stimulus duration.

Discrimination of the change in depth of sinusoidal amplitude modulation (AM) was investigated as a function of stimulus duration. The carrier frequency was 4000 Hz, the standard modulation depth (m) was either 0.1, 0.18, or 0.3, and the modulation rate was either 10, 20, 40, or 80 Hz. For all standard depths and modulation rates, threshold (delta m) decreased by more than a factor o two as stimulus duration doubled from the shortest duration used up to a certain duration (critical duration), beyond which the threshold decreased only slightly or remained constant. The critical duration corresponded to about four cycles of modulation. Psychometric functions were measured for different stimulus durations to examine the extent to which a multiple-looks model could explain the present data. This model provided a reasonable prediction of the change in AM depth discrimination threshold as a function of stimulus duration.

Adult↗
PubMed1997

Is the Olympic boardsailor an endurance athlete?

The present study was carried out in order to describe the physiological profile of top Olympic boa rdsailors of both genders and to measure the energy cost during actual boardsailing with particular attention to the most demanding conditions. Fourteen elite Olympic boardsailors (7 males and 7 females) volunteered to participate in the study. Each subject underwent a maximal cycle ergometer test in orderto measure VO2peak and ventilatory threshold (Tvent). Additionally, anthropometric measurements including body fat percentage were taken. The cardiorespiratory demand and the energy cost of actual boardsailing were assessed by means of a very light telemetric device (K2 Cosmed) which allowed the measurements of VO2, VE and HR. VO2peak was 63.6 +/- 2.3 ml x kg(-1) x min(-1) (Tvent 70% of maximum) and 49.2 +/- 4.1 (Tvent 60% of maximum) in males and females, respectively. The data recorded during actual boardsailing show that this sport activity can be classified as aerobic, the VO2 values being above or very close to those of Tvent values (75% and 60% of the maximum in males and females). Furthermore the mean blood lactate values obtained at the end of each regatta testing were 6 +/- 2 mMol x l(-1) in males and 5 +/- 1.5 mMol x l(-1) in females indicating a partial involvement of anaerobic metabolism, which in some regatta phases could represent a limiting factor for performance.

Adipose Tissue↗
PubMed1983

Force reserve of the diaphragm in patients with chronic obstructive pulmonary disease.

The fatigue threshold of the human diaphragm in normal subjects corresponds to a transdiaphragmatic pressure (Pdi)-inspiratory time integral (TTdi) of about 15% of Pdimax. The TTdi of resting ventilation was measured in 20 patients with chronic obstructive pulmonary disease (COPD) and ranged between 1 and 12% of Pdimax (mean 5%). TTdi was significantly related to total airway resistance (Raw) (r = 0.57; P less than 0.05). Five of these patients were asked to voluntarily modify their TI/TT (ratio of inspiratory time to total cycle duration; from 0.33 to 0.49) so as to increase their TTdi from a control value of 8% to an imposed value of 17% of Pdimax. The imposed pattern induced a progressive decline in the high-frequency (150-350 Hz)/low-frequency (20-40 Hz) power ratio (H/L) of the diaphragm electromyogram (fatigue pattern), quantitatively similar to that seen in normal subjects breathing with similar TTdi levels. The decay in H/L was followed by a progressive fall in mean Pdi meanly due to decrease in gastric pressure swings. It is concluded that 1) the force reserve of the diaphragm in COPD patients is decreased because of a decrease in Pdimax; 2) the remaining force reserve of the diaphragm can be exhausted by even minor modifications in the breathing pattern; and 3) at a TI/TT of 0.40 our COPD patients can increase their mean Pdi 3-fold before reaching a fatiguing pattern of breathing compared with 8-fold in normal subjects.

Aged↗
PubMedDate not supplied

[Status of thymoleptics in the treatment of bipolar disorders].

The widening of the concept of bipolar disorders to embrace the notion of a "spectrum" of disorders leads to the supposition that almost 5% of the general population may affected. Thymoleptics are the key treatment, but they should be prescribed over many years, and it is necessary to determine the threshold above which treatment should be considered. Lithium salts remain the reference thymoleptic treatment, but they are insufficiently effective in 30 to 60% of patients. They have a narrow therapeutic margin and are frequently accompanied by adverse effects. Numerous studies, mainly open, have confirmed the value of anti-epileptic thymoleptics (carbamazepine and valpromide) in mood disorders. They are comparable in efficacy to lithium salts, both in first-time treatment and in prophylactic use. Their main indications are as follows: marked progression of the mood disorder with the presence of mixed disorders or rapid-cycling disorders, concomitant organic pathology, substance abuse or personality disorder, poor response to lithium salts.

Anticonvulsants↗
PubMed2000

Local critical power is an index of local endurance.

The hypothesis that critical power (CP) is significantly lower than the maximal aerobic power of the knee extensors has been tested in nine endurance-trained subjects, seven gymnasts and seven weight lifters. CP was calculated as being equal to the slope of the linear relationship between exhaustion time and work performed at exhaustion on a knee-extension ergometer. CP was compared with the power output at the end of a progressive knee-extension exercise (P(peak)) and the power outputs corresponding to exhaustion times equal to 4 (P(4 min)), 6 (P(6 min)), 8 (P(8 min)) and 10 min (P(10 min)), calculated according to the linear relationship between work and exhaustion time. The hypothesis that CP corresponds to a steady state in metabolic and physiological parameters was tested in the gymnasts and the weight lifters by comparing CP with the fatigue thresholds of the integrated electromyogram (iEMG(FT)), lactate level (La(FT)), oxygen uptake (VO(2FT)) and heart rate (HR(FT)). The results of the present study demonstrate that the value of CP of a local exercise cannot be considered as the equivalent of the maximal aerobic power for general exercises. The values of P(4 min), P(6 min), P(8 min), P(10 min) and P(peak) were significantly higher than CP, and corresponded to 138, 126, 119, 115 and 151% CP, respectively. The results of the present study indicate that CP can be considered as an index of muscular endurance. Indeed, La(FT), iEMG (FT), VO(2FT) and HR(FT) were not significantly different from CP. All of these fatigue thresholds were significantly correlated with CP (r > 0.92). Moreover, the highest coefficient of correlation (r=0.71; P < 0.01) between the percentage of maximal aerobic power in cycling that corresponds to a blood lactate concentration of 4 mmol x l(-1) (OBLA%) and the different local aerobic indices was observed with CP.

Adult↗
PubMed1997

Circulating levels of peripheral blood leucocytes and cytokines following competitive cycling.

The objective of the study was to determine if prolonged and strenuous cycling leads to a polarized cytokine response, and/or unique mobilization of circulating leucocyte populations. Resting venous blood samples were collected from 6 amateur cyclists, 24 hr before, and at 10-25 min and 150 min after completion of a 250-km road race (race time: 404 +/- 3.5 min). Total leucocyte counts were significantly elevated following competition. Cell counts of CD3+CD8bright+ lymphocytes were depressed by 50% 150 min after competition. A significant increase in CD4+ cells expressing the IL-2R alpha chain was evident 150 min after competition. IL-6 concentrations were greatly increased, both at 10-25 min and 150 min after competition. Resting TNF-a concentrations were approximately doubled at both time points after competition. Plasma levels of IFN-gamma, IL-10 and IL-12 were below detection thresholds at all time points. These results suggest that performance of a 6.5 h competitive cycle-race does not induce a Type-1 or Type-2-dominated cytokine response, but one that is typical of a proinflammatory cytokine response.

Adult↗
PubMed2000

Effect of gender on the development of hypocapnic apnea/hypopnea during NREM sleep.

We hypothesized that a decreased susceptibility to the development of hypocapnic central apnea during non-rapid eye movement (NREM) sleep in women compared with men could be an explanation for the gender difference in the sleep apnea/hypopnea syndrome. We studied eight men (age 25-35 yr) and eight women in the midluteal phase of the menstrual cycle (age 21-43 yr); we repeated studies in six women during the midfollicular phase. Hypocapnia was induced via nasal mechanical ventilation for 3 min, with respiratory frequency matched to eupneic frequency. Tidal volume (VT) was increased between 110 and 200% of eupneic control. Cessation of mechanical ventilation resulted in hypocapnic central apnea or hypopnea, depending on the magnitude of hypocapnia. Nadir minute ventilation in the recovery period was plotted against the change in end-tidal PCO(2) (PET(CO(2))) per trial; minute ventilation was given a value of 0 during central apnea. The apneic threshold was defined as the x-intercept of the linear regression line. In women, induction of a central apnea required an increase in VT to 155 +/- 29% (mean +/- SD) and a reduction of PET(CO(2)) by -4.72 +/- 0.57 Torr. In men, induction of a central apnea required an increase in VT to 142 +/- 13% and a reduction of PET(CO(2)) by -3.54 +/- 0.31 Torr (P = 0.002). There was no difference in the apneic threshold between the follicular and the luteal phase in women. Premenopausal women are less susceptible to hypocapnic disfacilitation during NREM sleep than men. This effect was not explained by progesterone. Preservation of ventilatory motor output during hypocapnia may explain the gender difference in sleep apnea.

Adult↗
PubMed2000

Effects of gender on neuroendocrine and metabolic counterregulatory responses to exercise in normal man.

Significant, sexual dimorphisms exist in counterregulatory responses to commonly occurring stresses, such as hypoglycemia, fasting, and cognitive testing. The question of whether counterregulatory responses differ during exercise in healthy men and women remains controversial. The aim of this study was to determine whether a sexual dimorphism exists in neuroendocrine, metabolic, or cardiovascular responses to prolonged moderate exercise. Sixteen healthy (eight men and eight women) subjects matched for age (28+/-2 yr), body mass index (22+/-1 kg/m2), nutrient intake, and spectrum of physical fitness were studied in a randomized fashion during 90 min of exercise on a cycle ergometer at 80% of their anaerobic threshold (approximately 50% VO2 max). Respiratory quotient and oxygen consumption relative to body weight were identical in men and women. Glycemia was equated (5.3+/-0.2 mmol/L) during exercise via an exogenous glucose infusion. Gender had significant effects on counterregulatory responses during exercise. Arterialized epinephrine (1.05+/-0.2 vs. 0.45+/-0.04 nmol/L), norepinephrine (9.2+/-1.1 vs. 5.8+/-1.1 nmol/L), and pancreatic polypeptide (52+/-6 vs. 37+/-6 pmol/L) were significantly (P<0.01) increased in men compared to women, respectively. Plasma glucagon, cortisol, and GH levels responded similarly in men and women. Insulin values were higher at baseline in men and fell by a greater amount to reach similar levels during exercise compared to those in women. Endogenous glucose production, measured with [3-3H]glucose was similar in men and women. Carbohydrate oxidation was significantly increased in men relative to women (21.2+/-2 vs. 15.6+/-2 mg/kg fat free mass x min; P<0.05). Despite reduced sympathetic nervous system (SNS) drive, lipolytic responses were increased in women. Arterialized blood glycerol (215+/-30 vs. 140+/-20 micromol/L), beta-hydroxybutyrate (54+/-9 vs. 25+/-10 micromol/L), and plasma nonesterified fatty acids (720+/-56 vs. 469+/-103 micromol/L) were significantly (P<0.01) increased in women. In keeping with increased SNS activity, systolic blood pressure and mean arterial pressure were significantly increased (P<0.01) in men. In summary, this study demonstrates that a significant sexual dimorphism exists in neuroendocrine, metabolic, and cardiovascular counterregulatory responses to prolonged moderate exercise in man. We conclude that during exercise, men have increased autonomic nervous system (epinephrine, norepinephrine, pancreatic polypeptide), cardiovascular (systolic, mean arterial pressure) and certain metabolic (carbohydrate oxidation) counterregulatory responses, but that women have increased lipolytic (glycerol, nonesterified fatty acids) and ketogenic (beta-hydroxybutyrate) responses. Women may compensate for diminished SNS activity during exercise by increased lipolytic responses.

Adult↗
PubMed2006

Warm-up prior to undertaking a dynamic psychomotor task: does it aid performance?

AIM: The purpose of this study was to examine the effect of differing types of warm-up on the performance of a psychomotor skill that required quick reaction and movement times (MTs), and whole-body co-ordination. METHODS: Subjects (n=12) carried out a psychomotor task which involved reacting to 1 of 3 lights, then running through a slalom course before kicking a mini-soccer ball at a target. The task was completed following rest, a physical warm-up, a skill-specific warm-up and a skill plus physical warm-up. In the physical, and skill plus physical warm-ups the subjects cycled on an ergometer at a workload calculated to induce exercise at their lactate threshold. The outcome dependent variables were time to initiate a movement (reaction time), time to complete the slalom run (MT) and two measures of passing accuracy(constant error and variable error. Biomechanical variables(knee, hip and ankle angles, and horizontal and vertical ankle velocities at contact(were also compared. RESULTS: A repeated measures analysis of variance showed no significant effect of warm-up type on any of the dependent variables. Stepwise multiple regression analyses showed that changes in heart rate from resting values to those before performance of the skill test (D HR pre-performance) and those after performance of the test (D HR post-performance) combined were significant predictors of MT (R(2)=0.31, P<0.001), while D HR post-performance significantly predicted reaction time (R(2)=0.12, P<0.02). CONCLUSIONS: It was concluded that warm-up provided no significant benefit in performance for a task that was dynamic in nature but that physical arousal probably aids reaction and MTs.

Adult↗