1,720,977 research outputs found
Does Circumferential Stress Help to Explain Flow-Mediated Dilation?
No full textINTRODUCTION: Despite its potential, the validity of the flow-mediated dilation (FMD) test has been questioned because of lack of normalization to the vasodilatory stimulus. The hemodynamic conditions inside blood vessels lead to the development of superficial stress near the vessel walls, which can be divided into 2 categories: (1) circumferential stress (CS) and (2) shear stress (SS). Although SS is thought to be the primary governing stimulus, to the best of our knowledge, the degree to which CS contributes to FMD has not been reported in the literature.
PURPOSE:
The purpose of this study was to determine the importance of CS to FMD. We defined FMD as the SS-diameter dose-response slope.
METHODS:
Fourteen physically active, young [mean (SD) age, 26 (5) years], male subjects were tested. Progressive forearm heating and handgrip exercise elicited steady-state increases in shear rate. Hierarchical linear modeling was used to estimate change in diameter with repeated measures of SS and CS nested within each subject.
RESULTS:
Circumferential stress was found to positively promote FMD in addition to SS (β = 0.019, P = 0.019). However, the variance explained by CS was less than 1%.
CONCLUSIONS:
The physiologic significance of CS to FMD was minimal. However, physically active, young men were recruited; it remains to be determined whether CS has a more pronounced effect in subjects exhibiting cardiovascular risk factors
The effect of estimation and production procedures on running economy in recreational athletes
No full textObjectivesRunning economy is an important component in any endurance event. However, the influence of effort perception on running economy has yet to be examined.DesignThe purpose of this study was to assess the oxygen cost of running (running economy) at identical ratings of perceived exertion (RPE) during estimation (EST) and production (PR) procedures, during treadmill exercise.MethodsFourteen, well-trained male participants actively produced (self-regulated) a range of submaximal exercise intensities equating to RPE values 9, 11, 13, 15 and 17, and passively estimated their perception of exertion during an incremental graded-exercise test (GXT). Allometric scaling was used to ensure an appropriate comparison in running economy between conditions.ResultsThe present study demonstrated that the overall running economy between conditions was statistically similar (p > 0.05). A significant interaction was however identified between Conditions and RPE (p < 0.001). The interaction revealed that running economy significantly improved during PR but remained fairly consistent during EST between moderate and high perceptions of exertion (RPE 11–17). Despite similarities in running economy between conditions, physiological (oxygen uptake, heart rate, minute ventilation and blood lactate) and physical (running velocity) markers of exercise intensity were significantly higher during EST for equivalent perceptions of exertion (all p < 0.05).ConclusionsPassive estimation procedures may improve running economy and enhance athletic performance when compared to identical perceptions of exertion elicited during active production procedures. Athletes, coaches and physical trainers should consider the perceptual procedures utilised during training to ensure that an athlete trains at the most effective training intensity
The perceptual response to treadmill exercise using the Eston-Parfitt scale and marble dropping task, in children age 7 to 8 years.
No full textThis study assessed the nature of the perceived exertion response to treadmill running in 14 healthy 7-8 year-old children, using the Eston-Parfitt (E-P) Ratings of Perceived Exertion (RPE) scale and a marble dropping task. For the E-P scale and the marble dropping task, the relationships between the RPE and work rate were best described as linear (R2 = .96) and curvilinear (R2 = .94), respectively. This study further suggests that individual respiratory-metabolic cues (oxygen uptake: O2, heart rate: HR, ventilation: VE) may significantly influence the overall RPE to varying degrees in young children. The E-P scale provides an intuitively meaningful and valid means of quantifying the overall perception of exertion in young, healthy children during treadmill running. The marble dropping task is a useful secondary measure of perceived exertion, which provides further insight into the nature of the perceived exertion response to exercise in young children
The perceptual response to exercise of progressively increasing intensity in children aged 7-8 years: validation of a pictorial curvilinear ratings of perceived exertion scale
No full textThis study assessed the validity of the Eston-Parfitt (E-P) curvilinear Ratings of Perceived Exertion (RPE) Scale and a novel marble quantity task to provide estimates of perceived exertion during cycle ergometry. Fifteen children aged 7-8 years performed a discontinuous incremental graded-exercise test, and reported exertional ratings at the end of each minute. Significant increases in physiological and perceptual data were observed with increasing work rate. The relationship between work rate and marbles was curvilinear (mean R(2)=.94), supporting the theoretical justification for the E-P Scale. Strong linear (R(2)=.93) and curvilinear (R(2)=.94) relationships between RPE from the E-P Scale and work rate confirmed the robustness of the E-P Scale. Valid exertional ratings may be obtained using the E-P Scale with young children. The novel marble quantity task offers an alternative method of deriving perceived exertion responses in children
Prediction of maximal oxygen uptake from submaximal ratings of perceived exertion and heart rate during a continuous exercise test: the efficacy of RPE 13
No full textThis study assessed the utility of a single, continuous exercise protocol in facilitating accurate estimates of maximal oxygen uptake V(O)(2max) from submaximal heart rate (HR) and the ratings of perceived exertion (RPE) in healthy, low-fit women, during cycle ergometry. Eleven women estimated their RPE during a continuous test (1 W 4 s(-1)) to volitional exhaustion (measured V(O)(2max)). Individual gaseous exchange thresholds (GETs) were determined retrospectively. The RPE and HR values prior to and including an RPE 13 and GET were extrapolated against corresponding oxygen uptake to a theoretical maximal RPE (20) and peak RPE (19), and age-predicted HRmax, respectively, to predict V(O)(2max)). There were no significant differences (P > 0.05) between measured (30.9 +/- 6.5 ml kg(-1) min(-1)) and predicted V(O)(2max) from all six methods. Limits of agreement were narrowest and intraclass correlations were highest for predictions of V(O)(2max) from an RPE 13 to peak RPE (19). Prediction of V(O)(2max) from a regression equation using submaximal HR and work rate at an RPE 13 was also not significantly different to actual V(O)(2max) (R( 2 ) = 0.78, SEE = 3.42 ml kg(-1) min(-1), P > 0.05). Accurate predictions of V(O)(2max) may be obtained from a single, continuous, estimation exercise test to a moderate intensity (RPE 13) in low-fit women, particularly when extrapolated to peak terminal RPE (RPE(19)). The RPE is a valuable tool that can be easily employed as an adjunct to HR, and provides supplementary clinical information that is superior to using HR alone
A boxing-oriented exercise intervention for obese adolescent males: Findings from a pilot study
No full textIn New Zealand, obese Mãori and Pasifika adolescents are at risk of numerous cardio-metabolic conditions with raising physical activity levels being proposed as a useful intervention. The present study used a mixed method design to explore the effects of a non-contact boxing-oriented training programme designed in terms of improvements to cardio-metabolic variables. Traditional recruitment strategies (media, referrals) were employed, with limited success leading to 3 adolescent boys (14-15 y) participating in the pilot intervention. Exercise sessions included 30 minutes of non-contact boxing training, followed by 30 minutes of progressive resistance training. Participants attended three 1h training sessions each week, for a total of 12 weeks. Physiological variables included anthropometric indices, visceral fat thickness, central blood pressures, central arterial stiffness (augmentation index: AIx), and carotid arterial stiffness (β). Results revealed that there was no trend for change in body weight (125.5 ± 12.1 kg vs. 126.5 ± 11.0 kg) or BMI (39.3 ± 4.1 kg·m-2 vs. 39.0 ± 4.6 kg·m-2). However, there was a moderate decrease in visceral fat thickness (4.34 ± 2.51 cm vs 3.65 ± 1.11 cm, d = 0.36). There was no change in central pulse pressure (38.7 ± 7.3 mmHg vs. 38.3 ± 5.0 mmHg), however, there was a small improvement in β (3.01 ± 0.73 vs. 2.87 ± 0.84, d = 0.18). Focus group interview data with participants and their parents were used to explore issues related to motivation to participation. Results revealed participants commented on how the programme has led to new friendships, changes to their physical appearance, and increased physical fitness. Parents commented on increased self-confidence, better performance in school, and a willingness to take part in new activities. In conclusion, it appears participating in the boxing oriented training programme was motivating to participants who engaged and had some physiological benefits in obese adolescent boys of Mãori and Pasifika descent. However, despite these positive attributes, poor recruitment rates suggest that future work should focus on identifying the barriers to engagement
Decreasing the cardiovascular disease burden in Māori Children: the interface of pathophysiology and cultural awareness
No full textPreventive medicine needs to begin with our children
Full text linkAlthough cardiovascular disease (CVD) is typically associated with middle or old age, the atherosclerotic process often initiates early in childhood and is occurring at an increasing rate. There is a consensus that changes in life-style have driven the current epidemic. Adverse changes in physical activity, nutrition, and sleep behavior have been strongly linked to the development of a host of cardio-metabolic conditions, including obesity, dyslipidemia, hypertension, and type 2 diabetes mellitus. These conditions independently and additively increase CVD risk, even in children and adolescents. The result is that today’s children and adolescents are not only becoming pre-conditioned for CVD, but are also, due to developmental issues, unable to achieve the level of health achieved by their parents. Such early development of the disease risk factors also means that by simply focusing on the clinical manifestations of CVD that is “reactive” medicine, we are tackling the problem too late. Public health-care policy needs to place a stronger focus on paediatric “preventive” medicine, not only for the well-being of children, but to alleviate the increasing economic cost that is being placed on society through the prolonged burden of disease
Should the augmentation index be normalized to heart rate?
No full textPulse wave analysis(PWA) is widely used to investigate systemic arterial stiffness. The augmentation index(AIx), the primary outcome derived from PWA, is influenced by the mean arterial pressure(MAP), age, gender and heart rate(HR). Gender- and age-specific reference values have been devised, and it is recommended that the MAP be used as a statistical covariate. The AIx is also commonly statistically adjusted to a HR of 75 b·min(-1); however, this approach may be physiologically and statistically inappropriate. First, there appears to be an important physiological chronic interaction between HR and arterial stiffness. Second, the method used to correct to HR assumes that the relationship with AIx is uniform across populations. A more appropriate practice may be to include HR as an independent predictor or covariate; this approach is particularly recommended for longitudinal studies, in which changes in HR may help to explain changes in arterial stiffness
- …
