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Does short-term treatment with modafinil affect blood pressure in patients with obstructive sleep apnea?

OBJECTIVE: To investigate the effects of modafinil, a central nonamphetamine awakening substance, on blood pressure and heart rate in hypersomnolent patients with obstructive sleep apnea. DESIGN: This double-blind, randomized, placebo-controlled crossover trial was performed over 2 days and 3 nights in a single-center study of hospitalized patients from a referred care center. Twenty-six otherwise healthy men (age range, 30 to 60 years) with mild to moderate obstructive sleep apnea were recruited by the outpatient department of the Marburg University Sleep Laboratory. Patients were given 200 mg oral modafinil in the morning and 100 mg at midday. Placebo was given in the same manner in a crossover design. Mean arterial (radial) blood pressure was monitored continuously during nocturnal sleep and during a series of standardized daytime physical and psychologic performance tests. RESULTS: The difference in the main end point between the treatment with modafinil and placebo was 1.17+/-0.83 (mean +/- SE) mm Hg (95% confidence interval: -0.56 to 2.91 mm Hg). The maximal differences in blood pressure values occurred under loaded conditions (systolic blood pressure, ergometry: 5.62+/-1.13 mm Hg; mental stress test: 6.19+/-1.33 mm Hg). CONCLUSION: Short-term administration of modafinil did not elicit a significant response with regard to the main end point. However, cardiovascular effects during mental and physical load were observed. Longterm studies that include subjects with hypertension are necessary to investigate the clinical relevance of the cardiovascular effects of modafinil.

Adult↗

Force and power characteristics of a resistive exercise device for use in space.

We have developed a non-gravity dependent mechanical device, which provides resistance during coupled concentric and eccentric muscle actions, through the inertia of a spinning fly-wheel (Fly-Wheel Ergometry; FWE). Our research shows that lower-limb FWE exercise can produce forces and thus muscular stress comparable to what is typical of advanced resistance training using free weights. FWE also offers greater training stimuli during eccentric relative to concentric muscle actions, as evidenced by force and electromyographic (EMG) measurements. Muscle use of specific muscle groups, as assessed by the exercise-induced contrast shift of magnetic resonance images, is similar during lower-limb FWE and the barbell squat. Unlike free-weight exercise, FWE allows for maximal voluntary effort in each repetition of an exercise bout. Likewise, FWE exercise, not unassisted free-weight exercise, produces eccentric "overload". Collectively, the inherent features of this resistive exercise device and the results of the physiological evaluations we have performed, suggest that resistance exercise using FWE could be used as an effective exercise counter-measure in space. The flywheel principle can be employed to any exercise configuration and designed into a compact device allowing for exercises stressing those muscles and bone structures, which are thought to be most affected by long-duration spaceflight.

Aerospace Medicine↗

Free plasma catecholamines in spinal cord injured persons with different injury levels at rest and during exercise.

Spinal cord lesion leads to an interruption of pathways from brain to the peripheral sympathetic nervous system, which results in pathological changes in sympathetic innervation. Free epinephrine (E), norepinephrine (NE) and dopamine (DA) were measured in 30 tetraplegics (TETRA), 15 high-lesion paraplegics (T1 and T4, HPARA), 15 paraplegics with injuries between T5 and T10 (MPARA), 15 low-lesion paraplegics (below T10, LPARA) and 16 non-handicapped control persons (C) at rest, at 60 and 100% of maximal oxygen consumption during graded wheelchair ergometry (WCE). The TETRA showed significant lower E and NE levels at rest and only slight increases during physical exercise. The E and NE concentrations of the paraplegics with a lesion below T5 were significantly higher than those of the high-lesion paraplegics, as well as those of the control persons at every point in the study. All paraplegics and the control persons showed, at submaximal and maximal exercise, a significant increase in NE. Only a slight increase in E in HAPRA was shown. No differences were found at rest and during exercise in E and NE levels in the MPARA and LPARA. No significant differences were found in the dopamine concentration at rest or during exercise for any of the groups. In summary, different levels of lesion and the resulting interruption to sympathetic pathways in the spinal cord are decisive factors in the degree of impairment of sympathetic innervation in SCI persons. Tetraplegics show less preganglionic resting activity because of interruption of impulses from central centers and no considerable stimulation of the sympathetic nervous system during maximal exercise. Individuals with high paraplegia have a partial impairment of catecholamine release, especially of epinephrine, at rest and during exercise. Paraplegics with a lesion level below T5 showed an augmented basal and exercise-induced upper spinal thoracic sympathetic activity in comparison to control persons.

Adult↗

Determinants of insulin sensitivity in chronic heart failure.

OBJECTIVE: To describe the determinants of insulin sensitivity (IS) in chronic heart failure (CHF), we created a model in which the influence of lifestyle factors and etiology of heart failure on IS were incorporated concomitantly with age, left ventricular ejection fraction (LVEF) and parameters of body composition. DESIGN: Observational cohort study. SETTING: Outpatient clinic for chronic heart failure. PATIENTS: Fifty-seven male CHF patients [NYHA class II-III, age 61+/-9 years, body mass index (BMI) 26.9+/-3.3 kg/m2 (mean+/-S.D.)]. INTERVENTIONS: Euglycemic hyperinsulinemic clamp, cycle ergometry, anthropometric measurements, LVEF and a physical activity questionnaire. MAIN OUTCOME MEASURES: A model explaining the variance of IS in CHF. RESULTS: IS was 18.2+/-8.6 microg.kg(-1).min(-1).mU(-1).l(-1), fasting insulin level was 15.9+/-11.0 mU/l and fasting glucose level was 5.5+/-0.6 mmol/l. Peak VO2 was 19.1+/-4.9 ml.kg(-1).min(-1) and LVEF 26.2+/-7.1%. IS was inversely associated with fasting insulin concentration (r=-0.50, P<0.001) and BMI (r=-0.54, P<0.001). After controlling for BMI, IS also revealed a correlation with age (r=-0.36, P<0.01). The model explained 60% of variance in IS: BMI contributed 20%, smoking 17%, age 17% and physical activity in daily life (DPA) 16% (all P<0.05) to the variance of IS, whereas LVEF (9%) and etiology of heart failure (8%) contributed moderately. CONCLUSIONS: In CHF patients, IS is for a major part predicted by BMI, smoking, age, daily physical activity, LVEF and etiology of heart failure.

Adult↗

High intensity exercise assessment: relationships between laboratory and field measures of performance.

The purpose of this study was to examine the relationship between high intensity cycle ergometry when resistive forces were optimised and field tests of high intensity performance in an elite sprint trained group (n = 12). Body mass, stature and age of the group were determined prior to testing (66.3 +/- 9.8kg, 177 +/- 7.6cm and 17 +/- 0.74 yrs respectively). Field tests of high intensity performance examined included sprinting. maximal shuttle running and jumping ability (vertical and horizontal). Significant correlations existed between all field tests (P < 0.01). Only moderate correlations were observed for values generated on the cycle ergometer and performance tests (P > 0.05). The results of the present study suggest that the optimised cycle ergometer test and the performance tests are unrelated when evaluated statistically. These findings also suggest that the sprinting and jumping tests examined are highly related and may be substituted for each other as possible predictors of high intensity ability.

Adolescent↗

Ergonomy of paraplegic patients working with a reciprocating gait orthosis.

A reciprocating gait orthosis (RGO) is, among others, the most widely adopted device to restore the standing and walking capability of paraplegic patients. The aim of the present study was the evaluation of the energy demand (VO2), and cardiopulmonary load (HR and VE) imposed on the subject by different working tasks while sitting in a wheelchair or standing using a RGO. In addition, a comparison with the performance of normal subjects was also attempted. The RGO use allowed a dramatic improvement of patients' mobility and reach space in the workplace. A further advantage provided by the use of the RGO was represented by the increased mobility of the subjects with respect to the wheelchair confined situation. The energy demand and the cardiorespiratory load imposed on the subjects by the use of the RGO were not different from those observed both in the same subjects sitting in a wheelchair and in the controls. The energy demand slightly exceeded the values typical of light work and was, thus, compatible with the normal duration of a working day. On the other hand, the cardiac load corresponded to that typical of moderate activity, thus limiting the duration of the working task to 5-8 h. Based on the ergometry test, all of the working activities considered can be classified as aerobic activities, energy demand being under the ventilatory threshold.

Adult↗

Interval training program on a wheelchair ergometer for paraplegic subjects.

BACKGROUND: Various combinations of training intensity, duration and frequency are often proposed to people with spinal cord injuries in order to improve their fitness. However, no consensus about a specific training program has been reached for such a population. OBJECTIVE: This study investigated the effects of a short interval training program specifically designed for patients with spinal cord injuries. METHODS: Paraplegic men performed 30-min wheelchair ergometry three times per week, for 4 weeks. Maximal dynamic performance and endurance capacity were studied before and after the training program with an incremental test (10 W/2 min) until volitional fatigue and a constant work rate test, respectively. Cardiorespiratory responses were continuously studied during each of these tests. RESULTS: Training induced significant improvement in maximal tolerated power (+27.9%), and in peak oxygen consumption ([VO2, +18.5%). After training the subjects were able to maintain the load applied during the constant test (total mechanical work +210.7%), for a significantly longer time. The heart rate, [VO2 and ventilation values observed when the volunteers ended their first constant load test were significantly higher (+10%, +10%, +40% respectively) than those obtained after a similar time period during the second constant load test which was performed after the training program. CONCLUSION: After this short training period, with an appropriate combination of different types of training, duration, intensity and frequency exercises, we observed a significant improvement in the fitness level and endurance capacity of paraplegic subjects.

Adult↗

Effects of a wheelchair ergometer training programme on spinal cord-injured persons.

STUDY DESIGN: Before and after investigation of the effects of a wheelchair ergometer Training programme. OBJECTIVE: To investigate the effects of an original interval-training programme on work capacity and cardiorespiratory variables with spinal cord-injured persons (SCIP's) on a wheelchair-specific ergometer. SETTING: BESANCON, FRANCE. METHODS: Seven SCIP's (male) performed 45 min of wheelchair ergometry three times per week, for 6 weeks. Training effects on maximal dynamic performance and endurance capacity were studied by comparison of performance and cardiorespiratory responses observed during both a maximal progressive test (10 W/2 min) and the same training session performed before and after training. RESULTS: Training induced significant improvements in maximal tolerated power (+19.6%), in peak oxygen consumption (VO2,+16%), and in oxygen pulse (O2p,+18.7%). At ventilatory threshold, significant improvements were also observed in power output (+63%), VO2VT(+ 34.1), ventilation VEVT(+ 37.1%), and V2pVT(+ 19.9% ). Heart rate and ventilation were significantly lower (-11 and -14.6%, respectively) after training at the same work rate, while VO2 was unchanged. Between the first and the last training session, the total physical work was improved by 24.7%, whereas heart rate was unchanged. CONCLUSION: An interval-training programme individualised to each paraplegic subject using a wheelchair ergometer can significantly improve the fitness level and endurance capacity.

Adult↗

Changes in oxygen uptake, shoulder muscles activity, and propulsion cycle timing during strenuous wheelchair exercise.

STUDY DESIGN: Cross-over study. OBJECTIVE: To determine the effect of strenuous wheelchair exercise on oxygen uptake (VO2 ), muscle activity and propulsion cycle timing (including the push time and recovery time during one full arm cycle). SETTING: Laboratory of Sport Sciences at the University of France-Comte in France. METHODS: Two exercise bouts of 6-min duration were performed at a constant workload: (1) non-fatigable exercise (moderate workload) and (2) fatigable exercise (heavy workload). Measurement of VO2, surface electromyographic activity (EMG) from shoulder muscles, and temporal parameters of wheelchair ergometer propulsion were collected from eight able-bodied men (26+/-4 years). RESULTS: A progressive increase in VO2 associated with EMG alterations (P<0.05), and a decrease of the cycle and recovery time (P<0.05) during the heavy exercise. Whereas the push time remained constant, an increased muscle activation time (P<0.05) was found during heavy exercise. CONCLUSION: Observations during wheelchair ergometry indicate the development of fatigue and inefficient muscle coordination, which may contribute to deleterious stress distributions at the shoulder joint, increasing susceptibility to injury.

Adult↗

The validity of power output recorded during exercise performance tests using a Kingcycle air-braked cycle ergometer when compared with an SRM powermeter.

This study assessed the validity of power output recorded using an air-braked cycle ergometer (Kingcycle) when compared with a power measuring crankset (SRM). For part one of the study thirteen physically active subjects completed a continuous incremental exercise test (OBLA), for part two of the study twelve trained cyclists completed two tests; a maximal aerobic power test (MAP) and a 16.1 km time-trial (16.1 km TT). The following were compared; the peak power output (PPO) recorded for 1 min during MAP, the average power output for the duration of the time-trial and power output recorded during each stage of OBLA. For all tests, power output recorded using Kingcycle was significantly higher than SRM (P < 0.001). Ratio limits of agreement between SRM and Kingcycle for OBLA showed a bias (P < 0.00) of 0.90 (95%CI = 0.90-0.91) with a random error of X or / 1.07, and for PPO and 16.1 km TT ratio limits of agreement were 0.90 (95%CI = 0.88-0.92) X or / 1.07 and 0.92 (95% CI = 0.90-0.94) X or / 1.07, respectively. These data revealed that the Kingcycle ergometry system did not provide a valid measure of power output when compared with SRM.

Adult↗

Heart-rate recommendations: transfer between running and cycling exercise?

With the expanding use of portable heart rate (HR) monitors in endurance sports, HR is increasingly used as a marker for exercise intensity. Hereby, HR at the so-called individual anaerobic threshold (IAT) is one possible reference point. However, once determined, it is often attempted to apply HR recommendations from one type of ergometry to different kinds of exercises. We examined whether HR at IAT and at 4 mmol x l -1 blood lactate is predictable from cycling to running and vice versa. Data of 371 subjects (304 male, 67 female) were analyzed. All subjects underwent an incremental test on a treadmill (TR, starting speed 6 or 8 km x h -1, increments 2 km x h -1 every 3 min) and on a bicycle ergometer (BE, start at 50 Watt, increments 25 or 50 Watt every 3 min). IAT was determined at a net increase of lactate concentration of 1 - 5 mmol x l -1 above lactate concentration at lactate threshold for running (as in: Med Sci Sports Exerc 1998, 30 (10); 1552 - 1557) and 1.0 mmol x l -1 for cycling. A maximum time span of three weeks was allowed between the tests. We found that heart rate at IAT or at 4 mmol x l -1 blood lactate did not correlate between cycling and running. A sports specific test seems to be a prerequisite for reliable heart rate recommendations.

Adult↗

Sport specific performance diagnosis in rowing: an incremental graded exercise test in coxless pairs.

The aim of the present study was to develop and validate an incremental graded exercise test performed in the rowing boat(coxless pair) in order to give specific performance evaluation data. Furthermore, an attempt was made to transfer these data to training recommendations. Thirty-four female rowers of national and international level performed a 4 x 6 min incremental graded exercise test GXT(boat) in coxless pairs on a lake (6 km, no wind, no waves). The boat velocity on the water (V; measured by a speedometer PACE COACH) was increased continuously from 3.55 m x s-I to 4.03 m x s-1. The individual anaerobic threshold(IAT) was determined by means of the lactate (LA) kinetics during and after exercise. Within 28 days all subjects performed arowing ergometry test GXT(ergo); Gjessing rowing ergometer: 40 watts increments every 3 min) as well as 70 min of constant endurance training in the boat in moderate velocity (ET; n- 10 pairs because of changing weather conditions). Results for V/LAIHR at IAT are: GXT(boat): 3.84+/- 0.10 m x s-1/2.44 +/- 0.66 mmol x 1-1/172 + 11 min(-1); GXT(ergo): 206+/-10 watts/2.53 +0.40 mmol x 1-171 +/- 10 min-' (means+/-SD). The Spearman rank order test showed significant correlations for HR (p < 0.001) and the mean performances of the coxless pairs (p < 0.05). A'5 % lower V during ET lead to a 10% lower HR and a 30% lower LA compared to the values at IAT. In conclusion, both a performance specific evaluation and velocity oriented control of training are possible by means of a 4 x 6 min incremental graded exercise test in coxlesspairs. However, this test on the water requires almost perfect weather conditions. The HR recommendations based on GXT (ergo) were confirmed during GXT(boat).

Adult↗

A physiological comparison of synchronous and asynchronous hand cycling.

The purpose of this study was to compare submaximal physiological responses (oxygen uptake, ventilation, heart rate) and gross mechanical efficiency between synchronous and asynchronous hand cycling at different cadences. Thirteen non-disabled men (22.4 +/- 1.6 yr) performed two submaximal exercise tests on a treadmill, using synchronous and asynchronous crank settings in counter balanced order. Tests were performed using a commercially available hand cycle unit that was attached to a hand rim wheelchair. Each test consisted of five 5-min exercise bouts at 36, 47, 55, 65, and 84 rpm. ANOVA for repeated measures showed a significant effect of crank mode (p < 0.001) and cadence (p < 0.001), as well as an interaction effect between both (p < 0.01). Physiological responses were lower, and efficiency higher, in synchronous versus asynchronous hand cycling at all cadences. Post-hoc analysis of the (overall) effect of cadence showed significantly higher physiological responses and lower efficiency at the higher (84 vs. 65 rpm and 65 vs. 55 rpm) and lower (36 vs. 47 rpm) cadences. The interaction effect indicates that the effect of crank mode was dependent on cadence, showing a larger difference between synchronous and asynchronous hand cycling at 84 vs. 65 rpm and at 36 vs. 47 rpm. It is concluded that, in contrast to previous results in arm crank ergometry, synchronous hand cycling is less strenuous and more efficient than asynchronous hand cycling.

Adult↗

Effects of aerobic exercise training on lymphocyte subpopulations.

This study was conducted to determine the effects of an aerobic exercise training program on subpopulations of lymphocyte phenotypes. Fourteen healthy but sedentary males, 18-40 years of age, were randomly assigned to either an aerobic exercise training or control condition. Aerobic exercise training consisted of three 45-minute sessions of cycle ergometry exercise per week at 70-80% of age-predicted maximum heart rate for ten weeks. The aerobic exercise training resulted in a significant decrease in submaximal heart rate from 176 to 150 beats per minute to a fixed work rate of 150 watts (p < .01). This training effect was accompanied by increases in the resting level of the following lymphocyte subpopulations: CD2 (1717 vs 2183 mm3; p < .01), CD4 (942 vs 1280 mm3; p < .01), CD45RA+CD4+ (312 vs 595 mm3; p < .01), CD8 (655 vs 816 mm3; p < .05), and CD20 (162 vs 244 mm3; p < .01) cell counts. These findings indicate that several lymphocyte subpopulations are increased following a 10-week program of aerobic exercise training.

Adolescent↗

The effect of moderate resistance weight training on peak arm aerobic power.

The purpose of this study was to examine the effect of moderate resistance weight training (MRWT) on peak arm aerobic power as measured by arm cranking ergometry. Fourteen sedentary college age males, divided equally into two groups, served as subjects. The seven subjects in the MRWT group completed 12, 1-hr bouts of weight lifting over a 4 week period, exercising on Monday, Wednesday and Friday of each week. Exercise sessions included 3 sets of 10 repetitions of the following lifts: bench press, overhead dumbbell press, dumbbell arm curl, and behind the neck pull down. The remaining seven subjects served as a non-training control group, whose purpose was to account for possible learning effects on the arm ergometer test that could distort the statistical relevance of the aerobic power data. These subjects did not serve as a control for the weight training exercises, as the procedures used to determine muscular strength may produce a modest training effect. Peak arm aerobic power and muscular strength, as measured by the one-repetition maximum for each lift, were determined before and after the training program. The average increase in strength for all lifts combined for the trained group was 20.0%. They also experienced a 13.4% (p < .005) increase in peak arm aerobic power, whereas there was no significant change in this variable for the control group. It is concluded that peak arm aerobic power is enhanced by the changes in muscular strength produced by 4 wks of MRWT.

Adolescent↗

Carbohydrate ingestion immediately before exercise does not improve 20 km time trial performance in well trained cyclists.

This study examined the effects of carbohydrate ingestion on 20 km cycle time-trial (TT) performance in 14 well-trained cyclists (11 males, 3 females; peak oxygen uptake [VO2peak] 4.52 +/- 0.60 l/min; values are mean +/- SD). All subjects performed two experimental trials on their own bicycles mounted on an air-braked ergometry system (Kingcycle). Subjects were instructed to maintain the same training and dietary regimens before trials, which were conducted in a random order, 3-7 days apart, and at the same time of day for each subject. On the day of a trial, subjects reported to the laboratory and ingested an 8 ml/kg body mass bolus of either a 6.8 g/100 ml commercial carbohydrate-electrolyte (CHO) beverage (39 +/- 4 g of CHO), or a coloured, flavoured placebo. Ten min after finishing the drink, subjects commenced a 5 min warm-up at 150 W, before commencing the 20 km TT. The average power output (312 +/- 40 vs 311 +/- 38 W) and heart-rate (171 +/- 6 vs 171 +/- 5 beats/min for CHO and placebo, respectively) during the two rides did not differ between treatments. Accordingly, the performance times for the two TT's were the same (27:41 +/- 1:39 min:sec, for both CHO and placebo). We conclude that the ingestion of approximately 40 g of carbohydrate does not improve maximal cycling performance lasting approximately 30 min, and that carbohydrate availability, in the form of circulating blood glucose, does not limit high-intensity exercise of this duration.

Adolescent↗

Aortic and peripheral blood pressure during isometric and dynamic exercise.

The purpose of this study was to compare aortic blood pressure (AOR) to peripheral measurements by the Riva-Rocci/Korotkov (RRK) and Finapres continuous finger pressure (FIN) methods during dynamic and static exercise. A tip manometer was introduced in the ascending aorta after coronary angiography in 7 cardiac patients with good exercise capability. Static exercise was of moderate intensity and led to an increase of average diastolic and systolic AOR of 20 and 18 mmHg, respectively. The corresponding RKK values were 20 and 30 mmHg and the FIN values were 16 and 14 mmHg, respectively. In maximal cycle ergometry the discrepancies were larger, especially in the 4 subjects who reached 80% or more of predicted maximal work load. Diastolic and systolic increases in AOR in these 4 subjects were 12 and 38 mmHg, respectively. The RRK values were 17 and 76 mmHg. Increases in FIN values of 17 and 74 mmHg for diastolic and systolic measurements, respectively, were found. The peripheral FIN and RRK measurements give a systolic increase that is twice as large as that for AOR. It is concluded that RRK and FIN greatly overestimate the load to the cardiovascular system in dynamic exercise. When the cardiovascular load is estimated by the rate-pressure product, RRK produces an increase of 197%, FIN of 181%, while AOR gives an increase of only 133%. This suggests that the present criteria for blood pressure in exercise testing should be critically examined.

Adult↗

Long-term resistance training in the elderly: effects on dynamic strength, exercise capacity, muscle, and bone.

We examined the effects of 42 weeks of progressive weight-lifting training on dynamic muscle strength, peak power output in cycle ergometry, symptom limited endurance during progressive treadmill walking and stair climbing, knee extensor cross-sectional areas, and bone mineral density and content in healthy males and females aged 60-80 years, currently enrolled in a 2-year resistance training program. Subjects were randomized into either exercise (EX) or control (CON) groups (60-70 years: 38 males and 36 females; 70-80 years: 25 males and 43 females). EX trained several muscle groups twice per week for 42 weeks at intensities ranging from 50-80% of the load that they could lift once only (1 RM); CON did usual daily activities. After the 10 months there was no change in 1 RM strength in CON, but significant gains (mean increases up to 65%) in EX (no independent age or gender effects); 30% and 47% of the increase in 1 RM had occurred by 6 and 12 weeks, respectively. In EX, the 7.1% increase in peak cycling power output was significantly greater than in CON (+1.1%). The 17.8% improvement in symptom limited treadmill walking endurance was also greater than in CON (+3.4%), but the difference between groups during stair climbing was not significant (EX + 57%, CON + 33%). The cross-sectional areas of the knee extensors increased significantly by 5.5% in EX but were unchanged in CON. There were no changes in bone mineral density or content in either group. We conclude that long-term resistance training in older people is feasible and results in increases in dynamic muscle strength, muscle size, and functional capacity.

Aged↗