Cardiac, arterial and venous adaptation to weightlessness during 6-month MIR spaceflights with and without thigh cuffs (bracelets)

The objectives of this investigation were to study the effects of thigh cuffs (bracelets) on cardiovascular adaptation and deconditioning in 0 g. The cardiovascular parameters of six cosmonauts were measured by echocardiography, Doppler, and plethysmography, during three 6-month MIR spaceflights. Measurements were made at rest during preflight (−30 days), inflight (1, 3–4, and 5–5.5 months) without cuffs (morning) and after 5 h with cuffs, and during postflight (+3 and +7 days). Lower-body negative pressure (LBNP) measurements were performed 1 day after each resting session. Inflight values of left ventricle end-diastolic volume and stroke volume measured without the thigh cuffs (−8 to −24% and −10 to −16%, respectively, both P < 0.05) were lower than corresponding preflight values. The jugular and femoral vein cross-sectional areas (A _jv and A _fv, respectively) were enlarged (A _jv: by 23–30%, P < 0.001; A _fv: by 33–70% P < 0.01). The renal and femoral vascular resistances (R _ra and R _fa, respectively) decreased (R _ra: by −15 to −16%, P < 0.01; R _fa: by −5 to −11%, P < 0.01). Inflight, the thigh cuffs reduced the A _jv (by −12 to −20%, P < 0.02), but enlarged the A _fv (A _fv: by 9–20%, P < 0.02) and increased the vascular resistance (R _ra: by 8–13%, P < 0.05; R _fa: by 10–16%, P < 0.01) compared to corresponding inflight, without-cuffs values. During LBNP (−45 mmHg, where 1 mmHg=133.3 N/m²), R _fa and the ratio between cerebral and femoral blood flow (Q˙ _ca/Q˙ _fa) increased less inflight and postflight (+25% for R _fa and +30% for Q˙ _ca/Q˙ _fa) than during preflight (60% for R _fa and 75% for Q˙ _ca/Q˙ _fa, P < 0.01). This reduced vasoconstrictive response and less efficient flow redistribution toward the brain was associated with orthostatic intolerance during postflight stand tests in all of the cosmonauts. The calf circumference increased less inflight and postflight (6% P < 0.05) than preflight (9% P < 0.05). The vascular response to LBNP remained similarly altered throughout the flight. The thigh cuffs compensated partially for the cardiovascular changes induced by exposure to 0 g, but did not interfere with 0 g deconditioning. Accepted: 5 November 1999     

Effect of human head flexion on the control of peripheral blood flow in microgravity and in 1 g

This study evaluated, in six healthy subjects, whether head flexion, which stimulates the vestibular system and the tonic neck receptors, interferes with cardiovascular regulation. Arterial parameters were measured continuously using a pulsed Doppler ultrasound probe during parabolic flights with subjects either in the supine craned-head position (control) or in the supine anterior neck flexion bent-neck position. Exposure to 0 g induced a fluid shift towards the head (stroke volume +8%, P<0.05). Compared to the control situation the mean (SD) blood flow in the femoral artery decreased [ –10 (9)% vs +1 (10)%; P<0.05], and the ratio cerebral artery:femoral artery blood flow ( : ) increased [+8 (14)% vs –4 (7)%; P<0.05], in the bent-neck position. Thus, neck flexion without otolith loading (subject in 0 g) favoured cerebral perfusion during the exposure to 0 g. The return to 1 g, even in the supine position, induced a fluid shift towards the lower limbs. From 0 to 1 g, reduced less [ +6 (8)% vs –1 (8)%; P<0.05], and the : decreased more [–11 (9)% vs 0 (10)%; P<0.05], in the bent-neck position than in the control position. Thus the redistribution of peripheral blood flow in response to the fluid shift towards the legs was less efficient in the bent-neck position. In 0 g environment the passive flexion of the neck (neck receptor stimulation only) increased resistance in the femoral artery [R _fa +20 (21)%; P<0.05] and reduced the [–15(10)%; P<0.07] which increased the redistribution of flow towards the brain [ ; +12 (7)%; P<0.07]. This response was of lower amplitude when both otoliths and neck muscle were stimulated (neck flexion in 1 g) [R _fa+9 (7)%, P<0.05; –9 (12), NS; : 0 (12), NS]. We suggest that otolith and neck muscle stimulation (by neck flexion) trigger opposite vascular effects in response to a fluid shift towards the legs. Electronic Publication     

Impaired pressor response after spaceflight and bed rest: evidence for cardiovascular dysfunction

We hypothesized that impaired cardiovascular responses to isometric muscle action contribute to the cardiovascular deconditioning that occurs after space flight (SF) and head-down-tilt bed rest (HDT). Six subjects were studied before, during and after 120 days of –6° HDT, and four subjects were studied before, during (two subjects) and after 179–389 days of SF. Subjects performed a sustained handgrip (SHG) at a force equivalent to 30% of maximum contraction force for 2 min, and heart-rate (HR) and pressor (mean arterial pressure, ΔMAP) responses were recorded. At the same relative force, both ΔHR and ΔMAP were significantly reduced during the first days after HDT (–54%, P<0.05 and –43%, P<0.05). In two subjects studied within 24 h after their return from SF, ΔMAP was practically absent (–79%, P<0.05) whereas in four subjects studied 1–4 days after return from SF, ΔMAP was reduced by 35% (P<0.05). ΔHR was not significantly changed. Our finding of attenuated pressor responses to SHG after HDT and SF supports the notion of impairments at both the neurocirculatory control and effector organ levels. Electronic Publication     

Lipid and lipoprotein profiles, cardiovascular fitness, body composition, and diet during and after resistance, aerobic and combination training in young women

The purpose of this study was to evaluate the effects of various modes of training on the time-course of changes in lipoprotein-lipid profiles in the blood, cardiovascular fitness, and body composition after 16 weeks of training and 6 weeks of detraining in young women. A group of 48 sedentary but healthy women [mean age 20.4 (SD 1) years] were matched and randomly placed into a control group (CG, n=12), an aerobic training group (ATG, n=12), a resistance training group (RTG, n=12), or a cross-training group that combined both aerobic and resistance training (XTG, n=12). The ATG, RTG and XTG trained for 16 weeks and were monitored for changes in blood concentrations of lipoprotein-lipids, cardiovascular fitness, body composition, and dietary composition throughout a 16 week period of training and 6 weeks of detraining. The ATG significantly reduced blood concentrations of triglycerides (TRI) (P < 0.05) and significantly increased blood concentrations of high-density lipoprotein-cholesterol (HDL-C) after 16 weeks of training. The correlation between percentage fat and HDL-C was 0.63 (P < 0.05), which explained 40% of the variation in HDL-C, while the correlation between maximal oxygen uptake (V˙O_2max) and HDL-C was 0.48 (P < 0.05), which explained 23% of the variation in HDL-C. The ATG increased V˙O_2max by 25% (P < 0.001) and decreased percentage body fat by 13% (P < 0.05) after 16 weeks. Each of the alterations in the ATG had disappeared after the 6 week detraining period. The concentration of total cholesterol (TC), TRI, HDL-C and low density lipoprotein-cholesterol in the blood did not change during the study in RTG, XTG and CG. The RTG increased upper and lower body strength by 29% (P < 0.001) and 38%, respectively. The 6 week detraining strength values obtained in RTG were significantly greater than those obtained at baseline. The XTG increased upper and lower body strength by 19% (P < 0.01) and 25% (P < 0.001), respectively. The 6 week detraining strength values obtained in XTG were significantly greater than those obtained at baseline. The RTG, XTG and CG did not demonstrate any significant changes in either V˙O_2max, or body composition during the training and detraining periods. The results of this study suggest that aerobic-type exercise improves lipoprotein-lipid profiles, cardiorespiratory fitness and body composition in healthy, young women, while resistance training significantly improved upper and lower body strength only. Accepted: 9 April 2000     

Association between regional quadriceps oxygenation and blood oxygen saturation during normoxic one-legged dynamic knee extension

It is not clear whether muscle oxygenation (O_2-NIRS) measured by near-infrared spectroscopy (NIRS) correlates with femoral venous SO₂ (S_fvo₂) during normoxic exercise. Therefore, the purpose of this study was to compare physiologically calibrated O_2-NIRS with S_fvo₂ in subjects performing one-legged dynamic knee extension exercise (1L-KEE). Five healthy male subjects (age 25±2 year, height 177.8±4.8 cm, body weight 67.1 ± 5.0 kg; mean ± SD) performed 1L-KEE at 20, 40, and 60% of peak work rate (WR-peak) each for 4 min. S_fvo₂ was measured at rest and during the 3rd minute of each work rate. O_2-NIRS was continuously monitored in a proximal region of the vastus lateralis (VL-p), a distal region of VL (VL-d), and a proximal region of the rectus femoris (RF-p). S_fvo₂ was 56.0% at rest and decreased to 36.6 at 20% WR-peak, 35.8 at 40% WR-peak, and 31.1 at 60% WR-peak. There was a significant correlation between O_2-NIRS and S_fvo₂(VL-p: r ² = 0.62, VL-d: r ² = 0.35, RF-p: r ² = 0.62, with a moderate variation among individuals at each site; residual values = 4.83 – 11.75). These data indicate that NIRS measurement provides a reflection of S_fvo₂ during 20–60% WR-peak of normoxic 1L-KEE.     

Femoral to cerebral arterial blood flow redistribution and femoral vein distension during orthostatic tests after 4 days in the head-down tilt position or confinement

The first objective of this study was to confirm that 4 days of head-down tilt (HDT) were sufficient to induce orthostatic intolerance, and to check if 4 days of physical confinement may also induce orthostatic intolerance. Evidence of orthostatic intolerance during tilt-up tests was obtained from blood pressure and clinical criteria. The second objective was to quantify the arterial and venous changes associated with orthostatic intolerance and to check whether abnormal responses to the tilt test and lower body negative pressure (LBNP) may occur in the absence of blood pressure or clinical signs of orthostatic intolerance. The cerebral and lower limb arterial blood flow and vascular resistance, the flow redistribution between these two areas, and the femoral vein distension were assessed during tilt-up and LBNP by ultrasound. Eight subjects were given 4 days of HDT and, 1 month later, 4 days of physical confinement. Tilt and LBNP test were performed pre- and post-HDT and confinement. Orthostatic intolerance was significantly more frequent after HDT (63%) than after confinement (25%, P<0.001). Cerebral haemodynamic responses to tilt-up and LBNP tests were similar pre- and post-HDT or confinement. Conversely, during both tilt and LBNP tests the femoral vascular resistances increased less (P<0.002), and the femoral blood flow reduced less (P<0.001) after HDT than before HDT or after confinement. The cerebral to femoral blood flow ratio increased less after HDT than before (P<0.002) but remained unchanged before and after confinement. This ratio was significantly more disturbed in the subjects who did not complete the tilt test. The femoral superficial vein was more distended during post-HDT LBNP than pre-HDT or after confinement (P<0.01). In conclusion, 4 days of HDT were enough to alter the lower limb arterial vasoconstriction and venous distensibility during tilt-up and LBNP, which reduced the flow redistribution in favour of the brain in all HDT subjects. Confinement did not alter significantly the haemodynamic responses to orthostatic tests. The cerebral to femoral blood flow ratio measured during LBNP was the best predictor of orthostatic intolerance.     

Cerebral oxygenation and cerebral oxygen extraction in the preterm infant: the impact of respiratory distress syndrome

Haemodynamic factors play an important role in the etiology of cerebral lesions in preterm infants. Respiratory distress syndrome (RDS), a common problem in preterms, is strongly related with low and fluctuating arterial blood pressure. This study investigated the relation between mean arterial blood pressure (MABP), fractional cerebral oxygen saturation (ScO₂) and fractional (cerebral) tissue oxygen extraction (FTOE), a measure of oxygen utilisation of the brain, during the first 72 h of life. Thirty-eight infants (gestational age < 32 week) were included, 18 with and 20 without RDS. Arterial oxygen saturation (SaO₂), MABP and near infrared spectroscopy-determined ScO₂ were continuously measured. FTOE was calculated as a ratio: (SaO₂–ScO₂)/SaO₂. Gestational age and birth weight did not differ between groups, but assisted ventilation and use of inotropic drugs were more common in RDS infants (P<0.01). MABP was lower in RDS patients (P<0.05 from 12 up to 36 h after birth), but increased in both groups over time. ScO₂ and FTOE were not different between groups over time, but in RDS infants ScO₂ and FTOE had substantial larger variance (P<0.05 at all time points except at 36–48 h for ScO₂ and P<0.05 at 12–18, 18–24, 36–48 and 48–60 h for FTOE). During the first 72 h of life, RDS infants showed more periods of positive correlation between MABP and ScO₂ (P<0.05 at 18–24, 24–36 36–48 48–60 h) and negative correlation between MABP and FTOE (P<0.05 at 18–24, 36–48 h). Although we found that the patterns of cerebral oxygenation and extraction in RDS infants were not different as compared to infants without RDS, we suggest that the frequent periods with possible lack of cerebral autoregulation in RDS infants may make these infants more vulnerable to cerebral damage.     

Post-resistance exercise hypotension, hemodynamics, and heart rate variability: influence of exercise intensity

The occurrence of post-exercise hypotension after resistance exercise is controversial, and its mechanisms are unknown. To evaluate the effect of different resistance exercise intensities on post-exercise blood pressure (BP), and hemodynamic and autonomic mechanisms, 17 normotensives underwent three experimental sessions: control (C—40 min of rest), low- (E40%—40% of 1 repetition maximum, RM), and high-intensity (E80%—80% of 1 RM) resistance exercises. Before and after interventions, BP, heart rate (HR), and cardiac output (CO) were measured. Autonomic regulation was evaluated by normalized low- (LF_R–Rnu) and high-frequency (HF_R–Rnu) components of the R–R variability. In comparison with pre-exercise, systolic BP decreased similarly in the E40% and E80% (−6 ± 1 and −8 ± 1 mmHg, P < 0.05). Diastolic BP decreased in the E40%, increased in the C, and did not change in the E80%. CO decreased similarly in all the sessions (−0.4 ± 0.2 l/min, P < 0.05), while systemic vascular resistance (SVR) increased in the C, did not change in the E40%, and increased in the E80%. Stroke volume decreased, while HR increased after both exercises, and these changes were greater in the E80% (−11 ± 2 vs. −17 ± 2 ml/beat, and +17 ± 2 vs. +21 ± 2 bpm, P < 0.05). LF_R–Rnu increased, while ln HF_R–Rnu decreased in both exercise sessions. In conclusion: Low- and high-intensity resistance exercises cause systolic post-exercise hypotension; however, only low-intensity exercise decreases diastolic BP. BP fall is due to CO decrease that is not compensated by SVR increase. BP fall is accompanied by HR increase due to an increase in sympathetic modulation to the heart.     

Effect of Gastroenteritis During Pregnancy on Neonatal Outcome

Previous studies have shown that gastrointestinal disease in women during pregnancy may be a risk factor for low-birthweight infants. In the present study, the prevalence of gastroenteritis during pregnancy and its effect on neonatal outcome was examined for each gestational month in 10,597 single-birth mother-infant pairs in the ABIS Project (All Babies in Southeast Sweden). After exclusion of mothers with inflammatory bowel disease, celiac disease, lactose intolerance, or cow's milk allergy, data on the remaining 10,229 mother-infant pairs were compiled. Overall, 32.5% of the mothers suffered from gastroenteritis during pregnancy (95% confidence interval [CI], 32.5–32.5%). Risk factors included young maternal age (P for trend, <0.001), previous infants (P<0.001), work in a pediatric day-care facility (P=0.004), and experience of a major life event (P=0.027). Binary logistic and multiple linear regression analyses were adopted for the following variables of neonatal outcome: birth week, preterm birth (<37 weeks), birthweight, low birthweight (≤2,499 g), birth length, cesarean section, and hospitalization in a neonatal care unit. Maternal gastroenteritis during month 4 (–0.18 week; 95%CI=–0.36, –0.01 week), month 5 (–0.30 week; 95%CI=–0.49, –0.11 week), or month 7 (–0.18 week; 95%CI=–0.35, –0.01 week) of pregnancy was associated with a shorter pregnancy (adjusted for confounders). Gastroenteritis during part of the pregnancy was associated with a shortened pregnancy, but it had no other adverse effects on neonatal outcome. The reduction in the duration of pregnancy is probably of little clinical relevance. These findings should be confirmed in a prospective study. Electronic Publication     

Vertical whole-body vibration does not increase cardiovascular stress to static semi-squat exercise

The purpose of this study was to determine the effect of vertical whole-body vibration (WBV) on heart rate (HR), mean arterial pressure (MAP), femoral artery blood flow (FBF), and leg skin temperature (LSk_temp) during static exercise. These parameters were examined: seated next to the WBV device (passive, unloaded), with feet secured onto the WBV platform (knees 90° flexion) and while standing in a semi-squat position (static, loaded, knees 120° flexion); both with and without WBV. Conditions involved 1 min bouts separated by 1 min rest, repeated 15 times followed by 10 min recovery. WBV in the seated condition had no effect on the responses examined. The static semi-squat without WBV increased MAP 9 mmHg (P < 0.05) with no significant effect on HR, FBF, or LSk_temp. Similarly, WBV static semi-squat increased MAP 8–14 mmHg (P < 0.05), FBF 135–180 mL/min, and LSk_temp 1.8–3.1°C (P < 0.05). However, only the LSk_temp was increased above the no-WBV semi-squat position (P < 0.05). The addition of WBV to repeated intermittent static semi-squats does not appear to be a significant cardiovascular stressor.     

Analysis of Risk Factors for Ventilator-Associated Pneumonia in a Multidisciplinary Intensive Care Unit

 A prospective study was conducted to determine the incidence, risk factors and pathogens of ventilator-associated pneumonia (VAP) in 198 patients requiring mechanical ventilation for more than 48 hours. VAP occurred in 67 (33.8%) patients. Risk factors associated with VAP were admission APACHE II score >20 (odds ratio [OR] 4.77, 95% confidence interval [CI] 2.04–11.27, P<0.001), mechanical ventilation >10 days (OR 44.4, 95% CI 2.16–26.7, P<0.0001), ICU length of stay >10 days (OR 9.4, 95% CI 3.55–25.65, P<0.0001), and admission PaO₂/FiO₂ ratio <200 mmHg (OR 3.4, 95% CI 1.00–11.41, P<0.05). Logistic regression analysis showed a relationship between VAP and length of stay in ICU, duration of fever and presence of catheter-related infection. The pathogens isolated were predominantly gram-negative bacteria (83.2%), with a high proportion of Acinetobacter spp. (35%) resistant to commonly used antimicrobial agents. The mortality rate was not influenced by VAP.     

Enhanced flow-dependent vasodilatation after bed rest, a possible mechanism for orthostatic intolerance in humans

We investigated the alteration in flow-dependent-dilatation in the orthostatic intolerance occurring after bed-rest deconditioning. Eight men [aged mean (SEM) 32 (2) years] underwent two consecutive periods of 7 days of head-down-tilt (HDT, –6°) during bed rest. A control age and sex matched group [n=8, 30 (2) years], maintained its usual physical activity. Blood flow velocity (BFV) and diameter (Doppler and echotracking systems) were measured in the brachial artery, under basal conditions and during the post ischaemic hyperaemia following occlusion. The increase in BFV post-ischaemia did not change before, during and after HDT but the relative increase in the diameter was greater on the 7th day of the HDT period than before HDT [+8.8 (1.6)% compared to +3.7 (1.0)%, P<0.001]. After HDT, 11 of 16 standing tests (comprising eight subjects in the two HDT periods) had to be stopped because of orthostatic intolerance. The flow-dependent-dilatation measured at the end of HDT was negatively correlated with the post-bed-rest duration of orthostatic tolerance (r=0.78, P<0.01). After the sublingual administration of glyceryl trinitrate, there was no change in the increase in diameter. No significant changes were observed in the control group. Bed-rest deconditioning enhances the flow-dependent vasodilatation of large arteries and might contribute to the orthostatic intolerance observed following bed-rest. Electronic Publication     

Inspiratory muscle training improves cycling time-trial performance and anaerobic work capacity but not critical power

We examined whether inspiratory muscle training (IMT) improved cycling time-trial performance and changed the relationship between limit work (W _lim) and limit time (T _lim), which is described by the parameters critical power (CP) and anaerobic work capacity (AWC). Eighteen male cyclists were assigned to either a pressure-threshold IMT or sham hypoxic-training placebo (PLC) group. Prior to and following a 6 week intervention subjects completed a 25-km cycling time-trial and three constant-power tests to establish the W _lim–T _lim relationship. Constant-power tests were prescribed to elicit exercise intolerance within 3–10 (Ex1), 10–20 (Ex2), and 20–30 (Ex3) min. Maximal inspiratory mouth pressure increased by (mean ± SD) 17.1 ± 12.2% following IMT (P < 0.01) and was accompanied by a 2.66 ± 2.51% improvement in 25-km time-trial performance (P < 0.05); there were no changes following PLC. Constant-power cycling endurance was unchanged following PLC, as was CP (pre vs. post: 249 ± 32 vs. 250 ± 32 W) and AWC (30.7 ± 12.7 vs. 30.1 ± 12.5 kJ). Following IMT Ex1 and Ex3 cycling endurance improved by 18.3 ± 15.1 and 15.3 ± 19.1% (P < 0.05), respectively, CP was unchanged (264 ± 62 vs. 263 ± 61 W), but AWC increased from 24.8 ± 5.6 to 29.0 ± 8.4 kJ (P < 0.05). In conclusion, these data provide novel evidence that improvements in constant-power and cycling time-trial performance following IMT in cyclists may be explained, in part, by an increase in AWC.     

Effect of water ingestion on cardiovascular and thermal responses to prolonged cycling and running in humans: a comparison

The aim of this investigation was to examine the effect of water ingestion on physiological responses to prolonged cycling (CYC) and running (RUN). A group of 11 men with mean (SEM) maximal oxygen uptake (V˙O_2max) 48.5 (1.8) ml·kg^–1·min^–1 on a cycle-ergometer and 52.1 (2.2) ml·kg^–1·min^–1 on a treadmill (P<0.01) exercised for 90 min on four occasions, twice on each ergometer, at 60% of mode specific V˙O_2max. No fluid was taken (D) in one trial on each ergometer, whereas 60% of fluid losses were replaced by drinking water in the other trial (W). In CYC, water ingestion attenuated the change in cardiac output ( ) and the reduction in stroke volume (ΔSV) [ΔSV: –22.7 (3.8) in D, –10.7 (2.9) ml·beat^–1 in W, P<0.01; : –1.9 (0.5) in D, –0.2 (0.4) l·min^–1 in W at 85 min, P<0.01], but did not affect rectal temperature [T _re at 90 min: 38.8 (0.1)°C in D, 38.7 (0.1)°C in W]. In contrast, fluid replacement reduced hyperthermia in RUN [T _re at 90 min: 39.6 (0.2) in D, 39.1 (0.2)°C in W, P<0.01], and this was linked with a higher skin blood flow [RUN-W 88.9 (8.5), RUN-D 70.7 (8.4)%, P<0.05]. The and ΔSV were also attenuated with water ingestion in this mode of exercise (P<0.05). It is concluded that water ingestion improves physiological function in both cycling and running, but that the underlying mechanism is different in the two modes of exercise. Electronic Publication     

Body composition,fitness, and metabolic health during strength and endurance training and their combination in middle-aged and older women

In this study adaptations in body composition, physical fitness and metabolic health were examined during 21 weeks of endurance and/or strength training in 39- to 64-year-old healthy women. Subjects (n = 62) were randomized into endurance training (E), strength training (S), combined strength and endurance training (SE), or control groups (C). S and E trained 2 and SE 2 + 2 times in a week. Muscle strength and maximal oxygen uptake (VO₂max) were measured. Leg extension strength increased 9 ± 8% in S (P < 0.001), 12 ± 8% in SE (P < 0.001) and 3 ± 4% in E (P = 0.036), and isometric bench press 20% only in both S and SE (P < 0.001). VO₂max increased 23 ± 18% in E and 16 ± 12% in SE (both P < 0.001). The changes in the total body fat (dual X-ray absorptiometry) did not differ between groups, but significant decreases were observed in E (−5.9%, P = 0.022) and SE (−4.8%, P = 0.005). Lean mass of the legs increased 2.2–2.9% (P = 0.004–0.010) in S, SE and E. There were no differences between the groups in the changes in blood lipids, blood pressure or serum glucose and insulin. Total cholesterol and low-density lipoprotein cholesterol decreased and high-density lipoprotein cholesterol increased in E. Both S and SE showed small decreases in serum fasting insulin. Both endurance and strength training and their combination led to expected training-specific improvements in physical fitness, without interference in fitness or muscle mass development. All training methods led to increases in lean body mass, but decreases in body fat and modest improvements in metabolic risk factors were more evident with aerobic training than strength training.     

The influence of inspiratory and expiratory muscle training upon rowing performance

We investigated the effect of 4 week of inspiratory (IMT) or expiratory muscle training (EMT), as well as the effect of a subsequent 6 week period of combined IMT/EMT on rowing performance in club-level oarsmen. Seventeen male rowers were allocated to either an IMT (n = 10) or EMT (n = 7) group. The groups underwent a 4 week IMT or EMT program; after interim testing, both groups subsequently performed a 6 week program of combined IMT/EMT. Exercise performance and physiological responses to exercise were measured at 4 and 10 week during an incremental rowing ergometer ‘step-test’ and a 6 min all-out (6MAO) effort. Pressure threshold respiratory muscle training was undertaken at the 30 repetition maximum load (∼50% of the peak inspiratory and expiratory mouth pressure, P _Imax or P _Emax, respectively). P _Imax increased during the IMT phase of the training in the IMT group (26%, P < 0.001) and was accompanied by an improvement in mean power during the 6MAO (2.7%, P = 0.015). Despite an increase in P _Emax by the end of the intervention (31%, P = 0.03), the EMT group showed no significant changes in any performance parameters during either the ‘step-test’ or 6MAO. There were no significant changes in breathing pattern or the metabolic response to the 6MAO test in either group, but the IMT group showed a small decrease in HR (2–5%, P = 0.001). We conclude that there were no significant additional changes following combined IMT/EMT. IMT improved rowing performance, but EMT and subsequent combined IMT/EMT did not.     

Hormone changes induced by 37.5-h head-down tilt (−6°) in humans

Endocrine regulation of hormones and electrolytes during 37.5 h of –6° head down tilt (HDT) was studied in 13 men. The acute effects of simulated weightlessness are today well documented, but no study has been made concerning the hormone changes between 12 h and 2 days of HDT. Plasma volume showed a maximal increase of 9.23 (SEM 1.97) % after 6.5 h (P<0.01) and had returned to prestudy levels after 13.5 h of HDT. From 1.5 h to 4 h of HDT, C-terminus and N-terminus atrial natriuretic peptide (ANP) concentrations in plasma were increased by about 50% (P<0.01) and thereafter declined to pre-HDT levels. Plasma renin activity (PRA) was decreased by 47% (P<0.05) after 4 h of HDT; PRA increased after 23.5 h to 60%; noradrenaline concentration decreased immediately and remained low up to 37.5 h. Diuresis and natriuresis were evident during the 1st day of HDT, resulting in a marked increase in the urinary Na⁺. These results showed that the initial hormone (ANP, PRA) changes during HDT did not last more than 13.5 h and that after 24 h a new state would seem to have been established to adapt the body to hypovolaemia.     

Resistance training improves femoral artery endothelial dysfunction in aged rats

Although endurance exercise improves age-associated endothelial dysfunction, few studies have examined the effects of resistance training and the potential molecular mechanisms involved in altering vascular reactivity with age. Young (9 months) and aged (20 months) male, Fisher 344 rats were divided into four groups: Young Sedentary (YS, n = 14), Young Trained (YT, n = 10), Aged Sedentary (AS, n = 12), and Aged Trained (AT, n = 10). Resistance training consisted of climbing a 1 m wire ladder, at an 85° angle, 3 days/week for 6 weeks with increasing weight added to the tail. Endothelial function in femoral arteries was determined by constructing acetylcholine dose–response curves on a wire myograph. Femoral artery phospho-Ser1179-eNOS, eNOS and Hsp90 expression were evaluated by Western blot. Acetylcholine-induced vasorelaxation was significantly (P < 0.05) impaired in AS compared to YS and YT but not AT compared to YS and YT. Phospho-Ser1179-eNOS and eNOS were elevated (P < 0.05) in aged animals but not changed with resistance training. Resistance training increased Hsp90 levels in both young and old animals. Therefore, resistance training improves age-associated endothelial dysfunction in femoral arteries without changes in eNOS phosphorylation and expression. Increased Hsp90 expression, a regulator of eNOS activity and coupling, suggests a potential mechanism for this improvement.     

Cardiovascular responses to upright and supine exercise in humans after 6 weeks of head-down tilt (−6°)

Seven healthy men performed steady-state dynamic leg exercise at 50 W in supine and upright postures, before (control) and repeatedly after 42 days of strict head-down tilt (HDT) (−6°) bedrest. Steady-state heart rate (f _c), mean arterial blood pressure, cardiac output (Q˙ _c), and stroke volume (SV) were recorded. The following data changed significantly from control values. The f _c was elevated in both postures at least until 12 days, but not at 32 days after bedrest. Immediately after HDT, SV and Q˙ _c were decreased by 25 (SEM 3)% and 19 (SEM 3)% in supine, and by 33 (SEM 5)% and 20 (SEM 3)% in upright postures, respectively. Within 2 days there was a partial recovery of SV in the upright but not in the supine posture. The SV and Q˙ _c during supine exercise remained significantly decreased for at least a month. Submaximal oxygen uptake did not change after HDT. We concluded that the cardiovascular response to exercise after prolonged bedrest was impaired for so long that it suggested that structural cardiac changes had developed during the HDT period. Accepted: 6 June 2000     

Relationship between side medicine-ball throw performance and physical ability for male and female athletes

The purpose of the study was to examine the factors contributing to performance of a side medicine-ball throw (S-MBT) and a fast side medicine-ball throw (FS-MBT) and to analyze some of the factors which account for the difference in side medicine ball throw performance between the sexes. Sixteen males and ten females were evaluated by S-MBT, FS-MBT, isometric maximal trunk rotation torque (IMTRT), One repetition maximum of Parallel Squat (1RM_PS) and Bench Press (1RM_BP), Bench Press peak power (BP_PP), Static Squat Jump peak power (SSJ_PP) and vertical jump height. Males demonstrated significantly greater scores than females in all measurements. Significant correlations were observed in males, but not in females, between the distances during S-MBT and the IMTRT values (r = 0.596–0.739, P < 0.05–0.01) and the 1RM_PS values (r = 0.683–0.725, P < 0.01). In FS-MBT performance, significant correlations were observed in males, but not in females, between the ball velocity values during FS-MBT and the IMTRT values (r = 0.611–0.687, P < 0.05–0.01), 1RM_BP values (r = 0.596–0.655, P < 0.05–0.01) and 1RM_PS values (r = 0.679–0.718, P < 0.01). These results suggested that the contributing factors of S-MBT and FS-MBT performance were deferent in males and females. Hence, the side medicine-ball throw test would be useful to examine the trunk rotation power of male athletes, but may have a limited potential as a predictor of trunk rotation power for female athletes.