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Biomedical subjects

A D Flouris

Publications and source records attributed to A D Flouris.

9 recordsLinked to original sources
PubMed2006

The effect of performance feedback on cardiorespiratory fitness field tests.

We investigated the effects of performance feedback (PF) on predicting maximal oxygen uptake (VO2 max) using the 20 m Multistage Shuttle Run Test (MST) and 20 m Square Shuttle Test (SST). The agreement between these two field tests in relation to laboratory VO2 max was also examined. Forty healthy males (age: 21.5+/-2.3; BMI: 23.7+/-2.0) randomly performed four indirect VO2 max tests; that is the MST and SST, as well as a modified version of MST (MSTMD) and SST (SSTMD). During MST and SST subjects received PF with respect to both test stage and running pace. In contrast, MSTMD and SSTMD incorporated auditory feedback which solely emitted signals regulating the running pace. Participants also performed a laboratory VO2 max treadmill test (TT). ANOVA demonstrated significant mean predicted VO2 max decrements in both MSTMD (p<0.001) and SSTMD (p<0.05) compared to MST and SST, respectively. In predicting TTVO2 max, the '95% limits of agreement' analysis indicated errors equal to 3.6+/-9.6 and 1.4+/-10.3 ml kg-1 min-1 with coefficients of variation of +/-10.0% and +/-10.9%, for MST and MSTMD, respectively. The corresponding '95% limits of agreement' values for SST and SSTMD were 0.1+/-5.0 and -1.1+/-6.1 ml kg-1 min-1 with coefficients of variation of +/-5.4% and +/-6.7%, respectively. It is concluded that the application of PF leads to superior field testing performances.

Adult↗
PubMed2006

Influence of body heat content on hand function during prolonged cold exposures.

We examined the influence of 1) prior increase [preheating (PHT)], 2) increase throughout [heating (HT)], and 3) no increase [control (Con)] of body heat content (H(b)) on neuromuscular function and manual dexterity of the hands during a 130-min exposure to -20 degrees C (coldEx). Ten volunteers randomly underwent three passive coldEx, incorporating a 10-min moderate-exercise period at the 65th min while wearing a liquid conditioning garment (LCG) and military arctic clothing. In PHT, 50 degrees C water was circulated in the LCG before coldEx until core temperature was increased by 0.5 degrees C. In HT, participants regulated the inlet LCG water temperature throughout coldEx to subjective comfort, while the LCG was not operating in Con. Thermal comfort, rectal temperature, mean skin temperature, mean finger temperature (T(fing)), change in H(b) (DeltaH(b)), rate of body heat storage, Purdue pegboard test, finger tapping, handgrip, maximum voluntary contraction, and evoked twitch force of the first dorsal interosseus muscle were recorded. Results demonstrated that, unlike in HT and PHT, thermal comfort, rectal temperature, mean skin temperature, twitch force, maximum voluntary contraction, and finger tapping declined significantly in Con. In contrast, T(fing) and Purdue pegboard test remained constant only in HT. Generalized estimating equations demonstrated that DeltaH(b) and T(fing) were associated over time with hand function, whereas no significant association was detected for rate of body heat storage. It is concluded that increasing H(b) not only throughout but also before a coldEx is effective in maintaining hand function. In addition, we found that the best indicator of hand function is DeltaH(b) followed by T(fing).

Adaptation, Physiological↗
PubMed2006

Design and control optimization of microclimate liquid cooling systems underneath protective clothing.

The use of protective clothing, whether in space suits, hazardous waste disposal, or sporting equipment, generally increases the risk of heat stress and hyperthermia by impairing the capacity for evaporative heat exchange from the body to the environment. To date the most efficient method of microclimate cooling underneath protective clothing has been via conductive heat exchange from circulating cooling fluid next to the skin. In order to make the use of liquid microclimate cooling systems ((LQ)MCSs) as portable and practical as possible, the physiological and biomedical engineering design goals should be towards maximizing the efficiency of cooling to maintain thermal comfort/neutrality with the least cooling possible to minimize coolant and power requirements. Meeting these conditions is an extremely complex task that requires designing for a plethora of different factors. The optimal fitting of the (LQ)MCSs, along with placement and design of tubing and control of cooling, appear to be key avenues towards maximizing efficiency of heat exchange. We review the history and major design constraints of (LQ)MCSs, the basic principles of human thermoregulation underneath protective clothing, and explore potential areas of research into tubing/fabric technology, coolant distribution, and control optimization that may enhance the efficiency of (LQ)MCSs.

Cold Temperature↗
PubMed2006

Modelling atmospheric pollution during the games of the XXVIII Olympiad: effects on elite competitors.

UNLABELLED: The present study investigated the specific atmospheric conditions expected in Athens during the summer of 2004 in relation to the performance of elite athletes. DESIGN: Atmospheric pollution and weather data for the period April 16th to September 30th covering the entire greater Athens area and collected from 1984 to 2003 were used for descriptive statistics and model fitting. The analysis was focused on carbon monoxide (CO), ozone (O3), sulfur dioxide (SO2), nitrogen oxide (NO), nitrogen dioxide (NO2), and particulate matter with a diameter of < 10 microm (PM10). Factor and cluster analysis were used to describe atmospheric pollution in the northern, central, and southern sector of Athens. Generalized estimated equations (GEE) analysis was used to predict mean August 2004 pollutant concentration. Increased concentrations of O3 and PM10 (mean 2003 values: 134.3 +/- 9.3, 44 +/- 1.9 microg/m3, respectively) may generate adverse health and performance effects. The highest O3 values were recorded in the northern Athenian sector during the period June 12th to July 23rd, peaking around mid-day (12:00-18:00) (p < 0.05). The highest PM10 concentrations were recorded in the central Athenian sector during the period August 20th to September 9th, peaking at late afternoon (14:00-22:00) (p < 0.05). Similar concentrations were observed during all days of the week (p > 0.05). GEE approximated mean August 2004 pollutant concentrations similar to: CO: 2.8 (mg/m3), O3: 136, SO2: 24, NO: 134, and NO2: 106 (microg/m3). Concentrations of O3 and PM10 during the XXVIII Olympiad may generate adverse health and performance effects on the cardiovascular function of the elite competitors. (The present manuscript was submitted shortly before the start of the Games and became published after their completion. In this light, the actual pollution rates in Athens during August 2004 are presented in the Note Added in Proof as credence to the statistics used).

Air Pollutants↗
PubMed2006

Contribution of muscular strength in cardiorespiratory fitness tests.

AIM: Reports from laboratory-based studies have revealed a relationship between resistance training and endurance performance in both trained and untrained individuals. The purpose of the present study was to investigate the contribution of lower extremity muscular strength levels in performing cardiorespiratory fitness tests in laboratory, as well as field-based settings. METHODS: Within 2 weeks 38 healthy males (age 21.6+/-2.5 years, body mass index--BMI--24.4+/-2.2) performed three maximal oxygen uptake (VO(2max)) assessments using the 20 m multistage shuttle run test (MSR), the 20 m square shuttle run test (SSR), and a maximal treadmill test (MT) to exhaustion. Data were also obtained from knee flexion and extension isokinetic dynamometry at 60 degrees xs(-1). RESULTS: MSR performance correlated with the peak torque generated from both legs at r=0.63 (P<0.001). The equivalent for SSR was significant at r=0.44 (P<0.05), while MT demonstrated a non-significant positive correlation coefficient (r=0.34, P>0.05). Stepwise regression analyses revealed that the inclusion of leg strength parameters increased the coefficient of determination by 9% (P<0.001) and 4% (P<0.05) in the MSR and SSR, respectively. The MT model was not significantly associated with any of the isokinetic indices studied. CONCLUSIONS: Although moderately significant, the present coefficients suggest that performance in the present field-based cardiorespiratory fitness tasks is affected to a certain extent by lower extremity muscular strength. The latter also demonstrates a positive relationship with laboratory-based performance.

Adolescent↗
PubMed2005

The need for energy equilibrium.

Human bioenergetics has been extensively assessed by means of field proxies (ie, cardiorespiratory fitness field tests) during the last two decades. A systematic review of the germane literature, however, suggests considerable controversy as to whether the present tests lead to valid measurements of energy expenditure/utilisation. The present paper suggests that current modalities of field testing being used as predictive models for bioenergetics may suffer from methodological limitations, stemming primarily from inappropriate design. A major weakness in the theoretical basis of proxies is that, although based on field measurements, it seeks to predict laboratory bioenergetics which, in turn, are used to provide information on field performance. Hence, it seems reasonable that the number of transformations increases the potential for error and may have significant impact on the prediction of bioenergetics. Recent studies asserted the importance of achieving 'energy equilibrium' between the reference standard and each proxy. The suggested approach involves designing proxies that closely simulate each laboratory protocol used as reference standard. The theoretical bases of previous and contemporary approaches are discussed in an attempt to increase the validity of current proxy assessments.

Energy Metabolism↗
PubMed2005

Enhancing the efficacy of the 20 m multistage shuttle run test.

OBJECTIVE: Maximal oxygen uptake (Vo(2max)) of 44 ml kg(-1) min(-1) is an accepted criterion (Vo(2CR)) below which health and fitness for young male adults may be compromised. New algorithms validated for Vo(2CR) screening using the 20 m multistage shuttle run test (20mMST) were developed. METHODS: Vo(2max) was assessed in 110 males using a stationary gas analyser in a treadmill test (TT) and in 40 of these subjects using a portable gas analyser in the 20mMST. Vo(2max) predicted from the 20mMST in 70 subjects was used for cross validation. Two equations predicting Vo(2max) during 20mMST (EQ(MST)) and TT (EQ(TT)) were developed. RESULTS: Significant energy cost variance (EC(V)) was detected between TT and 20mMST (p<0.001), correlated significantly with subject height, and was a significant predictor of Vo(2max) differences between TT and 20mMST. The r(2) of EQ(MST) was 0.92 (p<0.001). Predicted Vo(2max) values from EQ(MST) correlated with directly measured 20mMST Vo(2max) at r = 0.96 (p<0.001). ANOVA detected no mean difference (p>0.05) between predicted and measured values. Prevalence of low fitness based on Vo(2CR) was 0.37. McNemar chi(2) indicated significant differences in sensitivity (p<0.001) and specificity (p<0.05) between the original 20mMST equation (EQ(LEG)) and EQ(TT), regarding Vo(2CR) screening. Cohen's kappa demonstrated higher agreement with TT Vo(2max) for EQ(TT) (p<0.001) than EQ(LEG) (p<0.05). TT Vo(2max) correlated with the end result of both EQ(LEG) and EQ(TT) at r = 0.75 (p<0.001). Unlike EQ(TT) (p>0.05), mean predicted Vo(2max) from EQ(LEG) was significantly higher compared to TT Vo(2max) (p<0.001). CONCLUSION: These algorithms increase the efficacy of 20mMST to accurately evaluate aspects of health and fitness.

Adult↗
PubMed2004

Enhancing specificity in proxy-design for the assessment of bioenergetics.

The purpose of this study was to examine the hypothesis that improved prediction of bioenergetics may be achieved when proxies are designed to simulate closely gold standard laboratory protocols. To accomplish this, a modified 'square' variation (SST) of the classical 20m Multistage Shuttle Run Test (MST) was designed aiming to reduce the stopping, turning and side-stepping manoeuvres. Within two weeks, 50 male volunteers (age 21.5+/-1.6, BMI 24.4+/-2.2) randomly underwent three maximal oxygen uptake (VO2max) assessments using a treadmill test (TT), the SST and MST. To assess SST reproducibility, 10 randomly-selected subjects performed the test twice. Validity results showed that mean predicted VO2max from SST was not significantly different compared to TT VO2max (p>0.05). In contrast, the equivalent value from MST was significantly higher (p<0.001) than TT. Furthermore, TT VO2max correlated with SST and MST at r=0.88 (p<0.001) and r=0.61 (p<0.05), respectively. The '95% limits of agreement' analysis (LIM(AG)) for SST and MST indicated a range of error equal to -0.5+/-5.4 and 8.1+/-8.0 (ml.kg(-1).min(-1)) with a coefficient of variation of +/-6 and +/-8.2%, respectively. Test-retest results for SST revealed no mean difference in VO2max (p>0.05) and a correlation coefficient of r=0.98 (p<0.001), while LIM(AG) demonstrated a range of error equal to -0.2+/-2.6 (ml.kg(-1).min(-1)) with a coefficient of variation of +/-5.6%. It is concluded that, compared to MST, the SST had a higher agreement with TT. The latter may well be explained by the closer simulation in bioenergetics between the two protocols (ie, the continuous nature of SST provides a closer proxy of TT).

Adult↗