Effects of elevated CO(2) levels on root morphological traits and Cd uptakes of two Lolium species under Cd stress

This study was conducted to investigate the combined effects of elevated CO₂ levels and cadmium (Cd) on the root morphological traits and Cd accumulation in Lolium multiflorum Lam. and Lolium perenne L. exposed to two CO₂ levels (360 and 1 000 μl/L) and three Cd levels (0, 4, and 16 mg/L) under hydroponic conditions. The results show that elevated levels of CO₂ increased shoot biomass more, compared to root biomass, but decreased Cd concentrations in all plant tissues. Cd exposure caused toxicity to both Lolium species, as shown by the restrictions of the root morphological parameters including root length, surface area, volume, and tip numbers. These parameters were significantly higher under elevated levels of CO₂ than under ambient CO₂, especially for the number of fine roots. The increases in magnitudes of those parameters triggered by elevated levels of CO₂ under Cd stress were more than those under non-Cd stress, suggesting an ameliorated Cd stress under elevated levels of CO₂. The total Cd uptake per pot, calculated on the basis of biomass, was significantly greater under elevated levels of CO₂ than under ambient CO₂. Ameliorated Cd toxicity, decreased Cd concentration, and altered root morphological traits in both Lolium species under elevated levels of CO₂ may have implications in food safety and phytoremediation.     

A Maximal Graded Exercise Test to Accurately Predict VO2max in 18–65-Year-Old Adults

The purpose of this study was to develop an age-generalized regression model to predict maximal oxygen uptake (VO_2max) based on a maximal treadmill graded exercise test (GXT; George, 1996) George, J. D. 1996. Alternative approach to maximal exercise testing and VO_2max prediction in college students. Research Quarterly for Exercise and Sport, 67: 452–457. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]. Participants (N?=?100), ages 18–65 years, reached a maximal level of exertion (mean?±?standard deviation [SD]; maximal heart rate [HR_max]?=?185.2?±?12.4 beats per minute (bpm); maximal respiratory exchange ratio [RER_max]?=?1.18?±?0.05; maximal rating of perceived exertion (RPE_max)?=?19.1?±?0.7) during the GXT to assess VO_2max (mean?±?SD; 40.24?±?9.11 mL·kg^?1·min^?1). Multiple linear regression generated the following prediction equation (R?=?.94, standard error of estimate [SEE]?=?3.18 mL·kg^?1·min^?1, %SEE?=?7.9): VO_2max (mL·kg^?1·min^?1)?=?13.160?+?(3.314 × gender; females?=?0, males?=?1) ? (.131 × age) ? (.334 × body mass index (BMI))?+?(5.177 × treadmill speed; mph)?+?(1.315 × treadmill grade; %). Cross validation using predicted residual sum of squares (PRESS) statistics revealed minimal shrinkage (R_p ?=?.93 and SEE _p ?=?3.40 mL·kg^?1·min^?1); consequently, this model should provide acceptable accuracy when it is applied to independent samples of comparable adults. Standardized β-weights indicate that treadmill speed (.583) was the most effective at predicting VO_2max followed by treadmill grade (.356), age (?.197), gender (.183), and BMI (?.148). This study provides a relatively accurate regression model to predict VO_2max in relatively fit men and women, ages 18–65 years, based on maximal exercise (treadmill speed and grade), biometric (BMI), and demographic (age and gender) data.     

Accumulation of chromium by Commelina communis L. grown in solution with different concentrations of Cr and L-histidine

Hydroponic experiments conducted to examine the chromiun uptake by C. communis in the presence of different Cr concentrations (Cr6+ 100 and 200 mg/L, respectively) and free histidine supplementation (0.5 and 1.0 mol/L) showed that shoot and root growth of C. communis decreased greatly with increasing Cr concentrations in the medium; and that the species was a typical excluder since it accumulated high concentrations of Cr in roots but comparatively low concentrations in shoots. Chromium in shoots and roots of Cr24 -supplied plants ranged from 329-1880 and 3788-4240 mg/kg DW, respectively, while those of Cr24 -histidine-supplied plants ranged from 478 to 629 mg/kg and 4157-4303 mg/kg DW, respectively. With Cr present in the hydroponic solution, C. communis accumulated more Cr in its tissues. Increasing histidine application to the solution significantly increased chromium accumulation in the plant tissues but could not alter the accumulation pattern of plants although it induced a higher concentration of Cr in its shoots and roots. These features suggested that C. communis may serve as an alternative species in a constructed wetland for phytoextraction treatment of Cr-containing wastewater and for phytostabilization of Cr mining spoils.     

Blood lactate recovery and respiratory responses during diagonal skiing of variable intensity

Abstract

The aims of the study were to investigate blood lactate recovery and respiratory variables during diagonal skiing of variable intensity in skiers at different performance levels. Twelve male cross-country skiers classified as elite (n=6; [Vdot]O_2max=73±3 ml · kg^?1 · min^?1) or moderately trained (n=6; [Vdot]O_2max=61±5 ml · kg^?1 · min^?1) performed a 48-min variable intensity protocol on a treadmill using the diagonal stride technique on roller skis, alternating between 3 min at 90% and 6 min at 70% of [Vdot]O_2max. None of the moderately trained skiers were able to complete the variable intensity protocol and there was a difference in time to exhaustion between the two groups (elite: 45.0±7.3 min; moderately trained: 31.4±10.4 min) (P<0.05). The elite skiers had lower blood lactate concentrations and higher blood base excess concentrations at all 70% workloads than the moderately trained skiers (all P<0.05). In contrast, [Vdot] _E/[Vdot]O₂ and [Vdot] _E/[Vdot]CO₂ at the 70% [Vdot]O_2max workloads decreased independently of group (P<0.05). Partial correlations showed that [Vdot]O_2max was related to blood lactate at the first and second intervals at 70% of [Vdot]O_2max (r=?0.81 and r=?0.82; both P<0.01) but not to [Vdot] _E/[Vdot]O₂, [Vdot] _E/[Vdot]CO₂ or the respiratory exchange ratio. Our results demonstrate that during diagonal skiing of variable intensity, (1) elite skiers have superior blood lactate recovery compared with moderately trained skiers, who did not show any lactate recovery at 70% of [Vdot]O_2max, suggesting it is an important characteristic for performance; and (2) the decreases in respiratory exchange ratio, [Vdot] _E/[Vdot]O₂, and [Vdot] _E/[Vdot]CO₂ do not differ between elite and moderately trained skiers.     

Science and the Gaelic sports: Gaelic football and hurling

Abstract

The two major sports indigenous to Ireland are Gaelic football and hurling. Both are 15-a-side field games played on a pitch 40% longer than a soccer field. They are firmly linked to a nationalist tradition and have by far the highest participation rates in sports in the country. Both games make multiple demands on participants due to their free-flowing nature and quick movement of play from end to end of the pitch. Hurling calls for hand–eye coordination and skilled use of the hurling stick in hitting and blocking the ball. Fitness characteristics mirror game demands. Participants at elite level in both games display high aerobic power, the footballers tending to be stronger in the upper body and better in vertical jumping. Gaelic footballers in particular match the fitness characteristics of professional soccer players, except for sprinting speed. Less attention has been paid to female participants, especially in camogie, the female version of hurling. Despite their amateur status, and due to the popularity of the sports and the training regimens adopted by players, the games have garnered sports science support systems for elite performers. Support personnel benefit from a generic knowledge base as well as a burgeoning research agenda targeted at the Gaelic games.     

Transfer of momentum from different arm segments to a light movable target during a straight punch thrown by expert boxers

Abstract

Three modern views about the factors limiting oxygen uptake in healthy humans are set against the original (early 1920s) concept of A. V. Hill and colleagues. The majority view for most of the intervening time has been that cardiac output is the essential limiting function. Among recent research in support of this contention is that, in quadrupeds, pericardiectomy, which allows greater diastolic filling, elevates maximum oxygen uptake; however, the relevance to bipedal exercise can be questioned. In any case, algebraic analyses of model systems indicate that all identifiable stages on the oxygen transport pathway, from pulmonary diffusion to oxidative phosphorylation in skeletal muscle mitochondria, materially influence maximum uptake. Thus, if a high cardiac output is to be of benefit, all the other steps must function better too. Nevertheless, these two viewpoints concur that the limit to maximum oxygen uptake is somatic. In contrast, there are strong indications that at altitudes where oxygen availability is about half that at sea level, cerebral oxygenation is a limiting factor, and some recent experiments raise the possibility that it might be a substantial influence at sea level also. Clearly, consensus cannot yet be reached on the question posed in the title.     

Effect of biological maturation on maximal oxygen uptake and ventilatory thresholds in soccer players: An allometric approach

Abstract

In this study, we investigated the effect of biological maturation on maximal oxygen uptake ([Vdot]O_2max) and ventilatory thresholds (VT₁ and VT₂) in 110 young soccer players separated into pubescent and post-pubescent groups.. Maximal oxygen uptake and [Vdot]O₂ corresponding to VT₁ and VT₂ were expressed as absolute values, ratio standards, theoretical exponents, and experimentally observed exponents. Absolute [Vdot]O₂ (ml · min^?1) was different between groups for VT₁, VT₂, and [Vdot]O_2max. Ratio standards (ml · kg^?1 · min^?1) were not significantly different between groups for VT₁, VT₂, and [Vdot]O_2max. Theoretical exponents (ml · kg^?0.67 · min^?1 and ml · kg^?0.75 · min^?1) were not properly adjusted for the body mass effects on VT₁, VT₂, and [Vdot]O_2max. When the data were correctly adjusted using experimentally observed exponents, VT₁ (ml · kg^?0.94 · min^?1) and VT₂ (ml · kg^?0.95 · min^?1) were not different between groups. The experimentally observed exponent for [Vdot]O_2max (ml · kg^?0.90 · min^?1) was different between groups (P = 0.048); however, this difference could not be attributed to biological maturation. In conclusion, biological maturation had no effect on VT₁, VT₂ or [Vdot]O_2max when the effect of body mass was adjusted by experimentally observed exponents. Thus, when evaluating the physiological performance of young soccer players, allometric scaling needs to be taken into account instead of using theoretical approaches.     

Accelerometer-measured daily physical activity related to aerobic fitness in children and adolescents

Abstract

Maximum oxygen uptake ([Vdot]O_2PEAK) is generally considered to be the best single marker for aerobic fitness. While a positive relationship between daily physical activity and aerobic fitness has been established in adults, the relationship appears less clear in children and adolescents. The purpose of this paper is to summarise recently published data on the relationship between daily physical activity, as measured by accelerometers, and [Vdot]O_2PEAK in children and adolescents. A PubMed search was performed on 29 October 2010 to identify relevant articles. Studies were considered relevant if they included measurement of daily physical activity by accelerometry and related to a [Vdot]O_2PEAK either measured directly at a maximal exercise test or estimated from maximal power output. A total of nine studies were identified, with a total number of 6116 children and adolescents investigated. Most studies reported a low-to-moderate relationship (r = 0.10–0.45) between objectively measured daily physical activity and [Vdot]O_2PEAK. No conclusive evidence exists that physical activity of higher intensities are more closely related to [Vdot]O_2PEAK, than lower intensities.     

Ventilatory Threshold,Running Economy and Distance Running Performance of Trained Athletes

Abstract

The purpose of this study was to assess the relationships among ventilatory threshold T(vent), running economy and distance running performance in a group (N=9) of trained experienced male runners with comparable maximum oxygen uptake ([Vdot]O₂ max). Maximal oxygen uptake and submaximal steady state oxygen uptake were measured using open circuit spirometry during treadmill exercise. Ventilatory threshold was determined during graded treadmill exercise using non-invasive techniques, while distance running performance was assessed by the best finish time in two 10-kilometer (km) road races. The subjects averaged 33.8 minutes on the 10km runs, 68.6 ml · kg ^-1 · min ^-1 for [Vdot]O₂ max, and 48.1 ml · kg ^-1 · min ^-1 for steady state [Vdot]O₂ running at 243 meters · min ^-1. The T(vent) (first deviation from linearity of [Vdot]_E, [Vdot]CO ₂ ) occurred at an oxygen consumption of 41.9 ml · kg ^-1 · min ^-1. The relationship between running economy and performance was r = .51 (p>0.15) and the relationship between T(vent) and performance was r = .94 (p < 0.001). Applying stepwise multiple linear regression, the multiple R did not increase significantly with the addition of variables to the T(vent); however, the combination of [Vdot]O₂ max, running economy and T(vent) was determined to account for the greatest amount of total variance (89%). These data suggest that among trained and experienced runners with similar [Vdot]O₂ max, T(vent) can account for a large portion of the variance in performance during a 10km race.