Exercise-induced improvements in liver fat and endothelial function are not sustained 12 months following cessation of exercise supervision in nonalcoholic fatty liver disease.

Supervised exercise reduces liver fat and improves endothelial function, a surrogate of cardiovascular disease (CVD) risk, in nonalcoholic fatty liver disease (NAFLD). We hypothesised that after a 16-week supervised exercise program, patients would maintain longer-term improvements in cardiorespiratory fitness, liver fat and endothelial function. Ten NAFLD patients (5/5 males/females, age 51±13 years, body mass index 31±3 kg m-2 (mean±s.d.)) underwent a 16-week supervised moderate-intensity exercise intervention. Biochemical markers, cardiorespiratory fitness (VO2peak), subcutaneous, visceral and liver fat (measured by magnetic resonance imaging and spectroscopy respectively) and brachial artery flow-mediated dilation (FMD) were assessed at baseline, after 16 weeks of supervised training and 12 months after ending supervision. Despite no significant change in body weight, there were significant improvements in VO2peak (6.5 ml kg-1 min-1 (95% confidence interval 2.8, 10.1); P=0.003), FMD (2.9% (1.5, 4.2); P=0.001), liver transaminases (P<0.05) and liver fat (-10.1% (-20.6, 0.5); P=0.048) immediately after the 16-week supervised training. Nevertheless, 12 months after ending supervision, VO2peak (0.9 ml kg-1 min-1 (-3.3, 5.1); P=0.65), FMD (-0.07% (-2.3, 2.2); P=0.95), liver transaminases (P>0.05) and liver fat (1.4% (-13.0, 15.9); P=0.83) were not significantly different from baseline. At 12 months following cessation of supervision, exercise-mediated improvements in liver fat and other cardiometabolic variables had reversed with cardiorespiratory fitness at baseline levels. Maintenance of high cardiorespiratory fitness and stability of body weight are critical public health considerations for the treatment of NAFLD (Clinicaltrials.gov identifier: NCT01834300).

Repeated Warm Water Immersion Induces Similar Cerebrovascular Adaptations to 8 Weeks of Moderate-Intensity Exercise Training in Females.

Exercise training has the potential to enhance cerebrovascular function. Warm water immersion has recently been shown to enhance vascular function including the cerebrovascular response to heating. We suggest that passive heating can be used alternatively to exercise. Our aim was to compare the effects of exercise with warm-water immersion training on cerebrovascular and thermoregulatory function. 18 females (25±5 y) performed 8 weeks of cycling (70% HRmax) or warm water immersion (42°C) for 30 min 3 times per week. Brachial artery flow-mediated dilation (FMD) and peak cardiorespiratory fitness (VO2peak) were measured prior to and following both interventions. A passive heat stress was employed to obtain temperature thresholds (Tb) and sensitivities for sweat rate (SR) and cutaneous vasodilation (CVC). Middle cerebral artery velocity (MCAv) was measured throughout. FMD and VO2peak improved following both interventions (p<0.05). MCAv and cerebrovascular conductance were higher at rest and during passive heating (p<0.001 and <0.001, respectively) following both interventions. SR occurred at a lower Tb following both interventions and SR sensitivity also increased, with a larger increase at the chest (p<0.001) following water immersion. CVC occurred at a lower Tb (p<0.001) following both interventions. Warm water immersion elicits similar cerebrovascular, conduit, and thermoregulatory adaptations compared to a period of moderate-intensity exercise training.

Nitric oxide-mediated cutaneous microvascular function is impaired in polycystic ovary sydrome but can be improved by exercise training.

Polycystic ovary syndrome (PCOS) is associated with cardiovascular disease. The contribution of the nitric oxide (NO) dilator system to cutaneous endothelial dysfunction is currently unknown in PCOS. Our aim was to examine whether women with PCOS demonstrate impaired cutaneous microvascular NO function and whether exercise training can ameliorate any impairment. Eleven women with PCOS (age, 29 ± 7 years; body mass index, 34 ± 6 kg m(-2)) were compared with six healthy obese control women (age, 29 ± 7 years; body mass index, 34 ± 5 kg m(-2)). Six women with PCOS (30 ± 7 years; 31 ± 6 kg m(-2)) then completed 16 weeks of exercise training. Laser Doppler flowmetry, combined with intradermal microdialysis of l-N(G)-monomethyl-l-arginine, a nitric oxide antagonist, in response to incremental local heating of the forearm was assessed in women with PCOS and control women, and again in women with PCOS following exercise training. Cardiorespiratory fitness, homeostasis model assessment for insulin resistance, hormone and lipid profiles were also assessed. Differences between women with PCOS and control women and changes with exercise were analysed using Student's unpaired t tests. Differences in the contribution of NO to cutaneous blood flow [expressed as a percentage of maximal cutaneous vasodilatation (CVCmax)] were analysed using general linear models. At 42°C heating, cutaneous NO-mediated vasodilatation was attenuated by 17.5%CVCmax (95% confidence interval, 33.3, 1.7; P = 0.03) in women with PCOS vs. control women. Exercise training improved cardiorespiratory fitness by 5.0 ml kg(-1) min(-1) (95% confidence interval, 0.9, 9.2; P = 0.03) and NO-mediated cutaneous vasodilatation at 42°C heating by 19.6% CVCmax (95% confidence interval, 4.3, 34.9; P = 0.02). Cutaneous microvascular NO function is impaired in women with PCOS compared with obese matched control women but can be improved with exercise training.

Effects of 6 months glucagon-like peptide-1 receptor agonist treatment on endothelial function in type 2 diabetes mellitus patients.

Glucagon-like peptide-1 receptor agonists (GLP-1 RA) are used for treatment in type 2 diabetes mellitus (T2DM). Little is known about their cardiovascular (CV) impact. We sought to determine the effects of chronic treatment on vascular function in T2DM. Brachial artery endothelial-dependent flow-mediated dilation (FMD) and endothelial-independent glyceryl trinitrate (GTN) function and carotid intima-medial thickness (cIMT) were assessed in 11 severely obese T2DMs (4 females, 7 males: 55 ± 8 years, diabetes duration 8.3 ± 4.7 years mean ± s.d.) before and after 6 months GLP-1 RA. Body weight (5.3 ± 1.2 kg; p < 0.05) and magnetic resonance imaging determined total and subcutaneous fat, but not visceral fat, decreased. Glycaemic control improved. There were no significant changes in FMD, GTN and cIMT (-1.1 ± 0.4%, 0.3 ± 3.0% and 0.00 ± 0.04 mm, respectively). Despite significant improvements in body composition and glycaemic control, 6 months GLP-1 RA treatment did not modulate vascular function. Alternative strategies may therefore be needed to reduce the burden of CV risk in severely obese patients with long-standing T2DM.

Lack of relationship between sedentary behaviour and vascular function in children.

Some evidence suggests that sedentary behaviour is independently associated with cardiovascular (CV) risk. Endothelial dysfunction is the earliest detectable manifestation of CVD and a strong independent predictor of CV events. No previous study has examined the relationship between sedentary behaviour and endothelial function. We assessed the basal association between conduit artery endothelial function and sedentary behaviour in children, along with the correlation between changes in sedentary behaviour and endothelial function. We studied 116 children (70♀: 10.7 ± 0.3; 46♂: 10.7 ± 0.3 years) on two occasions; in the summer (June) and late autumn (November). We assessed endothelial function via flow-mediated dilation (FMD) using high-resolution Doppler ultrasound. Sedentary behaviour (SB) was assessed using objective uni-axial accelerometry. At baseline, there were no significant differences between girls and boys for any measured variables with the exception of total physical activity time. FMD was not associated with sedentary behaviour in either group or in the cohort as a whole. Although FMD decreased (10.0 ± 4.3-7.9 ± 3.9%, P < 0.001) and SB increased (499.1 ± 103.5-559 ± 81.6 min/day, P < 0.001) between the seasons, no relationship existed between changes in these variables. Our data suggest that sedentary behaviour and changes in sedentary behaviour are not associated with endothelial function in children.

Impact of exercise training on endothelial function and body composition in young people: a study of mono- and di-zygotic twins.

Flow mediated dilation (FMD) is a surrogate marker of arterial function which can be improved by exercise training. To date, no study has assessed the magnitude of FMD changes in response to exercise training between groups of mono- (MZ) and di-zygotic (DZ) twins. The purpose of this study was therefore to compare FMD in MZ- and DZ twins before and after identical exercise training interventions. At baseline, FMD was assessed using high resolution Duplex ultrasound in 12 twin pairs (6 MZ pairs 13.5 ± 0.8 years, 6 DZ pairs 13.4 ± 0.8 years). Twins completed 8 weeks of exercise training (65-85% HR(max)), consisting of three 45-min sessions per week. Change (Δ) scores were entered into twin versus twin intraclass correlation analyses by group. Change in %body fat (r = 0.63, P = 0.05) was significantly correlated in the MZ, but not the DZ group (r = 0.31, P = 0.23). Change in FMD was also highly correlated in MZ (r = 0.74, P = 0.02) but not in the DZ group (r = 0.37, P = 0.18). Heritability of ΔFMD was estimated at 0.74. Exercise induced changes in FMD were similar within sets of monozygotic twins but not dizygotic twins. These data suggest that a significant portion of the arterial function response to exercise training may be genetically determined.

The effects of exercise training in the cold on cerebral blood flow and cerebrovascular function in young healthy individuals.

Exercise elicits acute increases in cerebral blood flow velocity (CBFv) and provokes long-term beneficial effects on CBFv, thereby reducing cerebrovascular risk. Acute exposure to a cold stimulus also increases CBFv. We compared the impact of exercise training in cold and thermoneutral environments on CFBv, cerebrovascular function and peripheral endothelial function. Twenty-one (16 males, 22 ± 5 years) individuals were randomly allocated to either a cold (5 °C) or thermoneutral (15 °C) exercise intervention. Exercise consisted of 50-min cycling at 70% heart rate max, three times per week for eight weeks. Transcranial Doppler was used to determine pre and post intervention CBFv, dynamic cerebral autoregulation (dCA) and cerebrovascular reactivity (CVRCO2). Conduit endothelial function, microvascular function and cardiorespiratory fitness were also assessed. Cardiorespiratory fitness improved (2.91 ml.min.kg-1, 95%CI 0.49, 5.3; P = 0.02), regardless of exercise setting. Neither intervention had an impact on CBFv, CVRCO2, FMD or microvascular function (P > 0.05). There was a significant interaction between time and condition for dCA normalised gain with evidence of a decrease by 0.192%cm.s-1.%mmHg-1 (95%CI -0.318, -0.065) following training in the cold and increase (0.129%cm.s-1.%mmHg-1, 95%CI 0.011, 0.248) following training in the thermoneutral environment (P = 0.001). This was also evident for dCA phase with evidence of an increase by 0.072 rad (95%CI -0.007, 0.152) following training in the cold and decrease by 0.065 (95%CI -0.144, 0.014) radians following training in the thermoneutral environment (P = 0.02). Both training interventions improved fitness but CBFv, CVRCO2 and peripheral endothelial function were unaltered. Exercise training in the cold improved dCA whereas thermoneutral negated dCA.

Does brachial artery flow-mediated dilation scale to anthropometric characteristics?

Flow-mediated dilation (FMD) assesses the health of the vascular endothelium. Despite widespread adoption of scaling practices in cardiac research, scaling for body size or composition has not been used for FMD. The present study investigated the relationships between brachial FMD and body composition in 129 children aged 9-10 (75 female symbol, 54 male symbol), and 50 men aged 16-49. Body composition variables (total, lean, fat mass in the whole body, arm, forearm) were assessed by dual-energy X-ray absorptiometry, FMD was measured in the brachial artery using high-resolution ultrasound. FMD was scaled using simple ratios (y/x) and allometric approaches (y/x ( b )) after log-log least squares linear regression produced allometric exponents (b). Size independence was confirmed via bivariate correlations (x:y/x; x:y/x ( b )). No relationships were evident between FMD and body composition variables in adults. Small correlations existed between FMD and measures of segmental fat mass in children (r = -0.18 to -0.19, p < 0.05), there were no significant relationships between FMD and measures of lean or total mass in children. For all significant relationships, b-exponents were different from 1 (CIs -0.36 to 0.07), suggesting ratio scaling approaches were flawed. This was confirmed when ratio scaling produced negative residual size correlations, whereas allometric scaling produced size-independent indices. Correlations between FMD and body composition were weak in children and insignificant in adults. As the results of this study are limited to the populations examined, our findings do not support the adoption of scaling procedures to correct FMD.

The effect of prolonged endurance exercise upon blood pressure regulation during a postexercise orthostatic challenge.

OBJECTIVE: To investigate the regulation of blood pressure in response to an orthostatic challenge in athletes running a marathon. METHODS: 10 experienced male runners (mean (SD) age 29 (4) years) were tested on the day prior to the 2004 London Marathon, and again immediately postrace (race time 210 (36) min). In addition, 6 of the subjects were retested 24 h postrace. During each examination, beat-to-beat systolic arterial blood pressure (SBP) and heart rate (HR) were measured, and stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) were estimated via arterial transmural pressure waveforms during 3 min in a supine position and then during 3 min of upright, unsupported standing. Data were averaged over 20 s epochs, and the final 20 s of each posture were compared prerace and postrace via repeated measures 2-way ANOVA. RESULTS: Prerace SBP in standing increased only moderately when compared with supine values (2 (9) mm Hg, NS). This was accompanied by an increase in HR (13 (7) beats/min, p<0.05), as well as a decrease in SV (16 (9) ml, p<0.05). However, there was little change in CO (-0.13 (0.97) litres/min, NS) or TPR (0.047 (0.280) medical units (MU), NS). Postrace SBP significantly decreased from supine to standing (-15 (20) mm Hg, p<0.05). The change in SBP was accompanied by an increase in HR (19 (6) beats/min, p<0.05) and a reduction in SV (26 (14) ml, p<0.05) and CO (-1.02 (1.39) litres/min, p = 0.05). Postrace there was no change in TPR (0.366 (0.607) MU, NS) upon standing. The orthostatic adjustments in SBP, HR and CO were greater than at prerace (p<0.05). The postrace orthostatic challenge resulted in only one subject experiencing presyncopal symptoms. At 24 h postrace, cardiovascular responses to an orthostatic challenge mirrored those at prerace. CONCLUSIONS: Following prolonged exercise, a fall in systolic blood pressure during orthostasis results from an inadequately compensated decrease in SV and resultant CO during standing.

Does conduit artery diameter vary according to the anthropometric characteristics of children or men?

Arterial measurements are commonly undertaken to assess acute and chronic adaptations to exercise. Despite the widespread adoption of scaling practices in cardiac research, the relevance of scaling for body size and/or composition has not been addressed for arterial measures. We therefore investigated the relationships between brachial artery diameter and body composition in 129 children aged 9 to 10 yr (75 girls and 54 boys), and 50 men aged 16-49 yr. Body composition variables (total, lean, and fat mass in the whole body, arm, and forearm) were assessed by dual-energy X-ray absorptiometry, and brachial artery diameter was measured using high-resolution ultrasound. Bivariate correlations were performed, and arterial diameter was then scaled using simple ratios (y/x) and allometric approaches after log-log least squares linear regression and production of allometric exponents (b) and construction of power function ratios (y/xb). Size independence was checked via bivariate correlations (x:y/x; x:y/xb). As a result, significant correlations existed between brachial artery diameter and measures of body mass and lean mass in both cohorts (r=0.21-0.48, P<0.05). There were no significant relationships between diameter and fat mass. All b exponents were significantly different from 1 (0.08-0.50), suggesting that simple ratio scaling approaches were likely to be flawed. This was confirmed when ratio scaling produced negative residual size correlations, whereas allometric scaling produced size-independent indexes (r=0.00 to 0.03, P>0.05). In conclusion, when between- or within-group comparisons are performed under circumstances where it is important to control for differences in body size or composition, allometric scaling of artery diameter should be adopted rather than ratio scaling. Our data also suggest that scaling for lean or total mass may be more appropriate than scaling for indexes of fat mass.

Energy expenditure in adolescents playing new generation computer games.

OBJECTIVE: To compare the energy expenditure of adolescents when playing sedentary and new generation active computer games. DESIGN: Cross sectional comparison of four computer games. Setting Research laboratories. PARTICIPANTS: Six boys and five girls aged 13-15 years. PROCEDURE: Participants were fitted with a monitoring device validated to predict energy expenditure. They played four computer games for 15 minutes each. One of the games was sedentary (XBOX 360) and the other three were active (Wii Sports). MAIN OUTCOME MEASURE: Predicted energy expenditure, compared using repeated measures analysis of variance. RESULTS: Mean (standard deviation) predicted energy expenditure when playing Wii Sports bowling (190.6 (22.2) kl/kg/min), tennis (202.5 (31.5) kl/kg/min), and boxing (198.1 (33.9) kl/kg/min) was significantly greater than when playing sedentary games (125.5 (13.7) kl/kg/min) (P<0.001). Predicted energy expenditure was at least 65.1 (95% confidence interval 47.3 to 82.9) kl/kg/min greater when playing active rather than sedentary games. CONCLUSIONS: Playing new generation active computer games uses significantly more energy than playing sedentary computer games but not as much energy as playing the sport itself. The energy used when playing active Wii Sports games was not of high enough intensity to contribute towards the recommended daily amount of exercise in children.

Conduit Artery Diameter During Exercise Is Enhanced After Local, but Not Remote, Ischemic Preconditioning.

Introduction: The ability of ischemic preconditioning (IPC) to enhance exercise capacity may be mediated through altering exercise-induced blood flow and/or vascular function. This study investigated the hypothesis that (local) IPC enhances exercise-induced blood flow responses and prevents decreases in vascular function following exercise. Methods: Eighteen healthy, recreationally trained, male participants (mean ±SD: age 32 ± 8 years; BMI 24.2 ± 2.3; blood pressure 122 ± 10/72 ± 8 mmHg; resting HR 58 ± 9 beats min-1) received IPC (220 mmHg; 4 × 5-min bilateral arms), REMOTE IPC (220 mmHg; 4 × 5-min bilateral legs), or SHAM (20 mmHg; 4 × 5-min bilateral arms) in a counterbalanced order prior to 30-min of submaximal (25% maximal voluntary contraction) unilateral rhythmic handgrip exercise. Brachial artery diameter and blood flow were assessed every 5-min throughout the 30-min submaximal exercise using high resolution ultrasonography. Pre- and post-exercise vascular function was measured using flow-mediated dilation (FMD). Results: IPC resulted in enlarged brachial artery diameter during exercise [0.016 cm (0.003-0.03 cm), P = 0.015] compared to REMOTE IPC, but blood flow during exercise was similar between conditions (P > 0.05). Blood flow (l/min) increased throughout exercise (time: P < 0.005), but there was no main effect of condition (P = 0.29) or condition ∗ time interaction (P = 0.83). Post-exercise FMD was similar between conditions (P > 0.05). Conclusion: Our data show that local (but not remote) IPC, performed as a strategy prior to exercise, enhanced exercise-induced conduit artery diameter dilation, but these changes do not translate into increased blood flow during exercise nor impact post-exercise vascular function.

Anthropometric profiles of elite Asian female handball players.

AIM: Handball has increased in status as a sport since its introduction in 1972 into the Summer Olympic Games. Whereas anthropometric profiles of female athletes have been reported for certain sports, data for elite handball players are limited. The current study was based on anthropometric measurements of 60 female Asian handball players competing in the continental championship, the aim being to identify any differences between countries and between playing positions. METHODS: The setting was the 12(th) Asian Games in Hiroshima, Japan. Anthropometric data were obtained from 60 players including teams from China, Japan, Kazakhstan and South Korea. Measurements included height, mass, skinfold thicknesses: from these measures percent body fat and muscle mass were estimated. Profiles were compared between 4 nations and 4 positional roles by means of ANOVA. RESULTS: Overall, mean (SD) values were 1.708 (0.068) m, 64.6 (7.7) kg, 20.8% (4.4%), 39.6% (5.2%) for stature, mass, percent body fat and percent muscle mass, respectively. There were small differences between players from different countries but no significant (P>0.05) influence of playing position. Players from Japan were shortest, lightest and lowest in adiposity. The Chinese players were tallest and had the greatest muscle mass. CONCLUSION: These female international handball players differed in some respects in anthropometric characteristics according to their country of origin. The Asian players were found to be relatively homogeneous across the different positions.

Does oral contraceptive use affect maximum force production in women?

OBJECTIVE: To examine the effects of oral contraceptive use on maximum force production in young women. METHODS: In the study, 21 female subjects (14 pill users and seven eumenorrheic controls) took part. All pill using subjects had been taking a combined, monophasic oral contraceptive pill for at least 6 months. Maximum dynamic and isometric leg strength, maximum isometric strength of the first dorsal interosseus (FDI) muscle, and plasma concentrations of oestradiol and progesterone were measured on days 7 and 14 of pill consumption and day 5 of pill withdrawal. The eumenorrheic group was tested (FDI strength and hormone concentrations) on days 2 and 21 of the menstrual cycle. RESULTS: There were no significant changes in the concentration of endogenous oestradiol or progesterone or any measure of muscle strength between pill phases (p<0.05). The pill group did not significantly differ from the eumenorrheic group (p<0.05), despite a significant increase in the concentration of progesterone and oestradiol on day 21 of the menstrual cycle compared with day 2 of the menstrual cycle and pill consumption and withdrawal (p<0.05). CONCLUSIONS: These data suggest that oral contraceptive use does not significantly affect muscle strength. Moreover, oral contraceptive users were not stronger or weaker than their eumenorrheic counterparts.

Modification of forearm resistance vessels by exercise training in young men.

The aim of this study was to determine whether a 4-wk handgrip training program would elicit changes in endothelium-dependent and endothelium-independent vasodilatation in resistance vessels of the human forearm. Minimum vascular resistance after a 10-min ischemic stimulus, an index of peak vasodilator capacity, was also determined. Forearm blood flow response to the endothelium-dependent vasodilator methacholine chloride did not change over the 4-wk-intervention period either in the group undertaking training (n = 11) or in control subjects (n = 6). Similarly, the response to sodium nitroprusside was not influenced by the handgrip training program. Peak vasodilator capacity of the trained forearms significantly increased, whereas no change was evident in the untrained limbs. These results suggest that 4 wk of forearm exercise training enhances peak vasodilator capacity of the vasculature without influencing stimulated activity of the nitric oxide dilator system.

The influence of recovery posture on post-exercise hypotension in normotensive men.

PURPOSE: Postexercise hypotension may be the result of an impaired vasoconstrictor response. This hypothesis was investigated by examining the central and peripheral hemodynamic responses during supine and seated recovery after maximal upright exercise. METHODS: After supine or seated baseline measurements, seven normotensive male volunteers completed a graded upright cycling protocol to volitional exhaustion. This was immediately followed by either supine or seated recovery. Measurements of pulsatile arterial blood pressure and central and peripheral hemodynamic variables recorded 30 min before exercise were compared with those taken throughout 60 min of recovery. RESULTS: Compared with baseline, mean arterial pressure (MAP) was reduced after exercise (P < 0.05) although the degree of change was not different between the supine (-9 +/- 4 mm Hg) and seated positions (-6 +/- 2 mm Hg). This change in MAP was associated with a reduction in diastolic blood pressure (DBP) (P < 0.05) and arterial pulse pressure (APP) (P < 0.01) for the supine and seated positions, respectively. The reduction in APP during seated recovery was accompanied by a decline in stroke volume (SV) (P < 0.05), not seen in the supine position, that limited the contribution of cardiac output (CO) to the maintenance of MAP. This effect of seated recovery was compensated by greater systemic (SVR) and regional vascular resistances in the forearm (FVR) and the forearm skin (SkVRA). There was also evidence of an augmented return of FVR and SkVRA to resting levels in the seated position after exercise. CONCLUSION: The lower peripheral resistance in the supine compared with seated recovery position suggests there is potential for greater vasoconstriction, although this is not evoked to increase blood pressure. This further suggests that the arterial baroreceptor reflex is reset to a lower operating pressure after exercise.

The isolated and combined effects of menstrual cycle phase and time-of-day on muscle strength of eumenorrheic females.

Diurnal variation in muscle performance has been well documented in the past few years, but almost exclusively in the male population. The possible effects of the menstrual cycle on human circadian rhythms have remained equivocal, particularly in the context of muscle strength. The purpose of the study was to analyze the isolated and combined effects of circamensal variation and diurnal changes on muscle strength. Eight eumenorrheic females (age 30 +/- 5 yrs, height 1.63 +/- 0.06m and body mass 66.26 +/- 4.6kg: mean +/- SD) participated in this investigation. Isokinetic peak torque of knee extensors and flexors of the dominant leg were measured at 1.05, 3.14rad.s(-1) (through 90 degrees ROM) at two times-of-day (06:00, 18:00 h) and five time points of the menstrual cycle (menses, mid-follicular, ovulation, mid-luteal, late luteal). In addition, maximum voluntary isometric contraction of knee extensors and flexors and electrically stimulated isometric contraction of the knee extensors were measured at 60 degrees of knee flexion. Rectal temperature was measured during 30min before the tests. There was a significant time-of-day effect on peak torque values for isometric contraction of knee extensors under electrical stimulation (P< 0.05). At 18:00 h, muscle force was 2.6% greater than at 06:00 h. The time-of-day effect was not significant when the tests were performed voluntarily without stimulation: effect size calculations indicated small differences between morning and evening for maximal voluntary isometric contraction and peak torque (at 1.05rad.s(-1) for the knee extensors. A circamensal variation was observed for peak torque of knee flexors at 1.05rad.s(-1), extensors at 3.14rad.s(-1), and also isometric contraction of knee flexors, values being greatest at the ovulation phase. Interaction effects between time-of-day and menstrual cycle phase were not observed in any of the indices of muscle strength studied. The phase of the menstrual cycle seemed to have a greater effect than did the time-of-day on female muscle strength in this group of subjects. The present results suggest that peripheral rather than central mechanisms (e.g., motivation) are implicated in the diurnal variation of maximal isometric strength of women.

Heart rate and oxygen consumption during walking on land and in deep water.

Oxygen consumption and heart rate were measured during treadmill walking and during walking in deep water in a group of women and in a group of men. In both groups predicted maximum oxygen uptakes were similar on land as in the water. However, there were obvious individual differences in the responses to land versus water exercise. These differences suggest that if deep water walking is used for training, the intensity of work should be assessed from preliminary fitness tests in water and not on land.

Impact of age and sex on carotid and peripheral arterial wall thickness in humans.

BACKGROUND: Although previous studies have reported age-related wall thickening in carotid arteries, it is not clear whether this is a systemic phenomenon which is also apparent in peripheral conduit arteries or whether conduit wall thickness (WT) changes occur to a similar degree in men and women. AIM: To determine whether sex modifies the impact of ageing on WT or wall-to-lumen ratio (W:L) in atherosclerosis-prone (i.e. carotid artery, femoral, superficial femoral, popliteal artery) and atherosclerosis-resistant (i.e. brachial artery) conduit arteries. METHODS: We included 30 young (23 ± 2 year; 15M : 15F) and 31 older (70 ± 5 year; 18M : 13F) healthy subjects. High-resolution ultrasound was used to measure diameter, WT and wall-to-lumen ratio (W/L) in all arteries. RESULTS: Older subjects had increased WT and W/L in the carotid, femoral, superficial femoral, popliteal and brachial arteries (all P < 0.05). Compared with women, men demonstrated larger diameter and WT (both P < 0.01) across all arteries. Sex did not impact upon age-related changes in WT or W/L (P = 0.39 and 0.43 respectively). CONCLUSION: Our data suggest that age-related wall thickening, evident in the carotid artery, is also apparent in the arteries of the upper and lower limbs. The impact of age on wall thickening did not differ between men and women. These data support the presence of systemic increases in WT and W/L with age in apparently healthy humans, independent of sex.

Flow-mediated dilation and cardiovascular event prediction: does nitric oxide matter?

Endothelial dysfunction is an early atherosclerotic event that precedes clinical symptoms and may also render established plaque vulnerable to rupture. Noninvasive assessment of endothelial function is commonly undertaken using the flow-mediated dilation (FMD) technique. Some studies indicate that FMD possesses independent prognostic value to predict future cardiovascular events that may exceed that associated with traditional risk factor assessment. It has been assumed that this association is related to the proposal that FMD provides an index of endothelium-derived nitric oxide (NO) function. Interestingly, placement of the occlusion cuff during the FMD procedure alters the shear stress stimulus and NO dependency of the resulting dilation: cuff placement distal to the imaged artery leads to a largely NO-mediated response, whereas proximal cuff placement leads to dilation which is less NO dependent. We used this physiological observation and the knowledge that prognostic studies have used both approaches to examine whether the prognostic capacity of FMD is related to its role as a putative index of NO function. In a meta-analysis of 14 studies (>8300 subjects), we found that FMD derived using a proximal cuff was at least as predictive as that derived using distal cuff placement, despite the latter being more NO dependent. This suggests that, whilst FMD is strongly predictive of future cardiovascular events, this may not solely be related to its assumed NO dependency. Although this finding should be confirmed with more and larger studies, we suggest that any direct measure of vascular (endothelial) function may provide independent prognostic information in humans.