Individual Regression Equations Research Articles

On two correlated linear models with common and different parameters

Abstract A parametric regression model may comprise several correlated individual regression equations, and these equations may have common and different unknown parameters. In such a situation, the common unknown parameter vectors in these equations can be estimated individually or simultaneously according to various available statistical inference methods. The purpose of this paper is to provide an integral account of two classic objects in regression theory: the best linear unbiased predictors (BLUPs) and the best linear unbiased estimators (BLUEs) on common and different unknown parameters in two correlated linear models with common and different parameters. We first introduce some reduced models associated with the two correlated linear models. We then define and characterize predictability and estimability of all unknown parameter vectors in the two correlated models and their reduced models, and derive analytical formulas for calculating the BLUPs and BLUEs of all unknown parameter vectors in these models by means of a constrained quadratic matrix optimization method. We also discuss a variety of theoretical properties of the predictors and estimators.

Influence of dynamic stretching on ankle joint stiffness, vertical stiffness and running economy during treadmill running.

The purpose of the present study was to investigate whether and how dynamic stretching of the plantarflexors may influence running economy. A crossover design with a minimum of 48 h between experimental (dynamic stretching) and control conditions was used. Twelve recreational runners performed a step-wise incremental protocol to the limit of tolerance on a motorised instrumented treadmill. The initial speed was 2.3 m/s, followed by increments of 0.2 m/s every 3 min. Dynamic joint stiffness, vertical stiffness and running kinematics during the initial stage of the protocol were calculated. Running economy was evaluated using online gas-analysis. For each participant, the minimum number of stages completed before peak O2 uptake (V̇O2peak) common to the two testing conditions was used to calculate the gradient of a linear regression line between V̇O2 (y-axis) and speed (x-axis). The number of stages, which ranged between 4 and 8, was used to construct individual subject regression equations. Non-clinical forms of magnitude-based decision method were used to assess outcomes. The dynamic stretching protocol resulted in a possible decrease in dynamic ankle joint stiffness (−10.7%; 90% confidence limits ±16.1%), a possible decrease in vertical stiffness (−2.3%, ±4.3%), a possibly beneficial effect on running economy (−4.0%, ±8.3%), and very likely decrease in gastrocnemius medialis muscle activation (−27.1%, ±39.2%). The results indicate that dynamic stretching improves running economy, possibly via decreases in dynamic joint and vertical stiffness and muscle activation. Together, these results imply that dynamic stretching should be recommended as part of the warm-up for running training in recreational athletes examined in this study.

A Comparison of Methods to Maintain the Equine Cecal Microbial Environment In Vitro Utilizing Cecal and Fecal Material.

Simple SummaryIn vitro systems for the fermentation of equine gastrointestinal (GI) content provide researchers with the ability to evaluate changes which may occur due to external influences but which cannot be accessed in vivo. The objective of this study was to evaluate three fermentation systems to replicate the equine cecal environment with regard to the microbiome and metabolite profile. The microbiome and metabolome of the fecal slurry used as inocula in this study were not representative of the cecal systems and care should be taken if feces are to be used to mimic proximal hindgut regions such as the cecum. However, the microbiome of the cecal inoculum maintained in either a chemostat batch fermenter or anaerobic chamber was fairly comparable. The metabolite concentrations, but not rate of production, were significantly different between the two cecal systems. These results provide a context to determine the most appropriate methods by which to create a fermentation system to reflect the equine cecal environment. They also highlight that caution must be exercised as many factors may influence the microbial and metabolic profiles within these systems; as such, they can best be used to demonstrate trends and gross reactions to environmental stimuli.The equine gastrointestinal (GI) microbiota is intimately related to the horse. The objective of the current study was to evaluate the microbiome and metabolome of cecal inoculum maintained in an anaerobic chamber or chemostat batch fermenter, as well as the fecal slurry maintained in an anaerobic chamber over 48 h. Cecal and fecal content were collected from healthy adult horses immediately upon death. Cecal fluid was used to inoculate chemostat vessels (chemostat cecal, n = 11) and vessels containing cecal fluid (anaerobic cecal, n = 15) or 5% fecal slurry (anaerobic fecal, n = 6) were maintained in an anaerobic chamber. Sampling for microbiome and metabolome analysis was performed at vessel establishment (0 h), and after 24 h and 48 h of fermentation. Illumina sequencing was performed, and metabolites were identified via nuclear magnetic resonance (NMR). Alpha and beta diversity indices, as well as individual metabolite concentrations and metabolite regression equations, were analyzed and compared between groups and over time. No differences were evident between alpha or beta diversity in cecal fluid maintained in either an anaerobic chamber or chemostat. The microbiome of the fecal inoculum maintained anaerobically shifted over 48 h and was not comparable to that of the cecal inoculum. Metabolite concentrations were consistently highest in chemostat vessels and lowest in anaerobic fecal vessels. Interestingly, the rate of metabolite change in anaerobic cecal and chemostat cecal vessels was comparable. In conclusion, maintaining an equine cecal inoculum in either an anaerobic chamber or chemostat vessel for 48 h is comparable in terms of the microbiome. However, the microbiome and metabolome of fecal material is not comparable with a cecal inoculum. Future research is required to better understand the factors that influence the level of microbial activity in vitro, particularly when microbiome data identify analogous communities.

Length estimation of Atlantic bluefin tuna (Thunnus thynnus) using vertebrae

AbstractAtlantic bluefin tuna (Thunnus thynnus; BFT) is a large (up to 3.3 m in length) pelagic predator which has been exploited throughout the eastern Atlantic and Mediterranean since prehistoric times, as attested by its archeological remains. One key insight derivable from these remains is body size, which can indicate past fishing abilities, the impact of fishing, and past migration behavior. Despite this, there exists no reliable method to estimate the size of BFT found in archeological sites. Here, 13 modern Thunnus spp. skeletons were studied to provide power regression equations that estimate body length from vertebra dimensions. In modern specimens, the majority of BFT vertebrae can be differentiated by their morphological features, and thus, individual regression equations can be applied for each rank (position in vertebral column). In an archeological context, poor preservation may limit one's ability to identify rank; hence, “types” of vertebrae were defined, which enable length estimates when rank cannot be determined. At least one vertebra dimension, height, width, or length correlated highly with body length when vertebrae were ranked (R2 > 0.97) or identified to types (R2 > 0.98). Whether using rank or type, length estimates appear accurate to approximately ±10%. Finally, the method was applied to a sample of Roman‐era BFT vertebrae to demonstrate its potential. It is acknowledged that further studies with larger sample sizes would provide more precision in BFT length estimates.

FORECASTING VOLUMES OF FDI OF COUNTRIES BASED ON INDICATORS OF THEIR INVESTMENT ATTRACTIVENESS

Objective. The objective of the article is the analysis of the state and features of the development of special economic zones in the world.. Methods. The following methods and techniques of cognition are applied in the research process: theoretical generalization and comparison, analysis and synthesis, induction and deduction, grouping, correlation-regression analysis, clustering. Results. It is determined that among the wide list of indicators of investment attractiveness, the following indicators are most often used and are the most authoritative ones: Doing business Index, The Global Competitiveness Index, Global Innovation Index, Fragile States Index, Legatum Prosperity Index, Index of Economic Freedom, as well as credit ratings international rating agencies, including Moody's, Fitch, etc. Based on the analysis of the relationship between indicators of investment attractiveness and the actual volumes of FDI attraction of 101 countries of the world in 2015-2020, it is established that this relationship can be described as direct (Doing business Index, The Global Competitiveness Index, Global Innovation Index , Index of Economic Freedom) or the reverse (Fragile States index, Legatum Prosperity index); weak (Doing Business Index, Index of Economic Freedom, Fragile States Index) or moderate (Global Competitiveness Index, Legatum Prosperity (economy) Index).It is substantiated that despite the fact that the most representative indicators of investment attractiveness, according to the calculated values ​​of the correlation coefficients, are the Global Competitiveness Index and the Global Innovation Index, however, they do not have a significant impact on the actual volumes of FDI attraction of countries (the correlation coefficient varies within 0, 15-0.39), cannot be used as a dominant determinant for forecasting FDI volumes. It is substantiated that for forecasting the volume of FDI, it is advisable to use not one, but a set of indicators of investment attractiveness. It is established that the composite four-factor regression model based on individual regression equations of countries on indicators of investment attractiveness according to their cluster affiliation has the greatest predictive power.

Correlation of cadaveric stature with posterior curve length of sternum in Mewat Region of Haryana: A comparative analysis of SPSS with machine learning

The aim of the present study was to develop a population specific regression formula for estimating cadaveric length from posterior curve length of fresh sternum and compare the linear regression results of SPSS and machine learning. Cadaveric length and posterior curve length (PCL) of the sternum were measured from 74 dead bodies (39 males and 35 females) aged between 18 and 95 years from known corpses during medico-legal autopsies. Cadaveric stature and PCL was greater in males as compared to females (p<0.001). Regression equations and correlation coefficients were derived for PCL by SPSS and machine learning, which were Y=122.79+2.504(PCL) and Y= 122.98+2.49(PCL), respectively, with correlation coefficients of 0.609 and 0.606, respectively. Individual regression equations were also formulated for males and females separately with significant correlation. The standard error of estimate and R square model were also derived. Cross validating linear regression results of SPSS with machine learning showed almost similar results. The study suggests that posterior curve length of sternum in relation with post-mortem or cadaveric stature shows regional or geographic variation, a moderately positive correlation and relatively low reliability in estimating cadaveric stature, and thus, has limited forensic value.

Energy expenditure during a Vinyasa yoga session.

Vinyasa yoga has been recently promoted as one of the most popular mindful exercises to improve overall health, including body weight management. The purpose of this study was to determine the metabolic response of 24 moderately trained individuals during a 90-min group Vinyasa yoga routine. Heart rate (HR) time course of 12 males and 12 females (age: 39±7.33 years) was recorded during two group Vinyasa yoga sessions consisted of four sections (warm-up, high-intensity Surya Namaskar (HSN), no Surya Namaskar postures, and cool-down). Maximal oxygen uptake (V̇O<inf>2peak</inf>) and maximum HR had been estimated earlier after a maximal treadmill test. V̇O<inf>2</inf> during Vinyasa yoga sessions was estimated from individual regression equations using the relationship of V̇O<inf>2</inf> and HR values derived from V̇O<inf>2peak</inf> test, while the metabolic rate (kcal/min) was calculated from the relationship of HR and kcal/min. Total session energy consumption was the average value of the two yoga sessions. The 2 (gender) × 4 (sections) mixed ANOVA revealed no significant interaction between the two factors (P=0.101) for the mean metabolic rate (7.1±2.6 kcal/min). Mean metabolic rate thought was higher (P=0.015) in males compared to females at each section. Also, significant differences were found among the four Vinyasa yoga sections (P<0.001) in the rate of energy expenditure, with HSN presenting the highest mean values (P<0.05). It seems that systematic participation in Vinyasa yoga may effectively improve cardiorespiratory fitness and promote body weight loss, as an alternative method to traditional aerobic exercise.

Evaluation of Load-Velocity Relationships and Repetitions-to-Failure Equations in the Presence of Male and Female Spotters.

Nickerson, BS, Williams, TD, Snarr, RL, Garza, JM, and Salinas, G. Evaluation of load-velocity relationships and repetitions-to-failure equations in the presence of male and female spotters. J Strength Cond Res 34(9): 2427-2433, 2020-The purpose of this study was 2 fold: (a) to determine whether differences in mean concentric velocity (MCV), repetitions-to-failure (RTF), measured 1 repetition maximum (1RM), and 1RM prediction methods vary between lifter and spotter sex and (b) determine the accuracy of velocity-based 1RM (MCV1RM) and repetitions-to-failure-based 1RM (RTF1RM) prediction equations in the presence of either a male or female spotter. Twenty resistance-trained individuals (50% men) participated in this study. The initial 2 visits involved measuring 1RM for the bench press with a male or female spotter. Visits 3 and 4 required subjects to lift loads at 30 (5-repetitions), 50 (5-repetitions), and 70% 1RM (RTF) in the presence of a male or female spotter. Velocity-based 1RM was determined through individual regression equations using the submaximal loads (MCV30, MCV50, and MCV70). Repetitions-to-failure-based 1RM was determined through the RTF at 70% 1RM using Wathen (Wathen1RM), Mayhew (Mayhew1RM), and Epley (Epley1RM) equations. There were significant interactions when assessing Wathen1RM and Mayhew1RM (p < 0.05). Female lifters produced significantly higher estimated 1RM values during the male spotter condition using Wathen1RM and Mayhew1RM than the female spotter condition (p = 0.032 and 0.033, respectively). MCV1RM and Epley1RM produced smaller mean differences than Wathen1RM and Mayhew1RM when compared with measured 1RM. However, MCV1RM produced the largest standard error of estimate, whereas Epley1RM produced the lowest values. Epley1RM should be used over MCV1RM, Wathen1RM, and Mayhew1RM when loads up to 70% 1RM are implemented. Also, spotter sex only seems to impact female lifters when using the RTF1RM prediction equations of Wathen1RM and Mayhew1RM.

Cardiorespiratory And Metabolic Responses Of High Intensity Yoga-surya Namaskar Session

The recent global rise in obesity appears to be a threat to public health as it is connected with various cardiovascular and metabolic diseases. Surya Namaskar (SN), a component of Vinyasa yoga, consisted of a specific sequence of 12 yoga postures performed with controlled breath, is often used as an alternative of a typical fitness program to improve overall health, including body weight management. However, research data studying high intensity SN (HSN) are limited. PURPOSE: The aim of the present study was to assess cardiorespiratory and metabolic demands of HSN performed with 3 s/pose. METHODS: Heart rate (HR) response of twenty-four moderately trained subjects (12 males and 12 females; mean ± sd age: 39 ±7.33 years, body stature: 167.38±9.32 cm, body mass: 66.60±14.07 kg, % body fat: 23.30±5.86; VO2peak: 45.48±7.12 ml.kg-1.min-1 and HRmax: 183.54±10.13 bpm) was recorded during two-15 min sessions HSN practice 7 days apart. Maximal oxygen uptake (VO2peak) and maximum HR (HRmax) had been estimated earlier, after an incremental test to exhaustion. VO2 during HSN was estimated from individual regression equations using the relationship of VO2 and HR values derived from VO2peak test, while the metabolic rate (kcal.min-1) was calculated from the relationship of HR and kcal.min-1. Total HSN energy consumption was the average value of the two-15 min sessions. RESULTS: Mean ± sd values of the %HRmax, %VO2max and rate of energy expenditure during HSN were 71.7 ± 7.5%, 59.9 ± 10.3 and 8.9 ± 3.3 kcal.min-1 (7.9 ± 2.0 METs) respectively. Total session energy expenditure was 133.04 ± 50.14 kcal. CONCLUSIONS: The results of the present study confirm that an HSN session may produce a sufficient training stimulus to promote cardiorespiratory fitness and favor weight loss in moderate trained adults.

Calibration and validation processes for relative humidity measurement by a Hygrochron iButton

Accurate relative humidity (RH) measurement is demanded in studies of thermal comfort. Thermal discomfort occurs when the near-to-skin temperature or RH is outside of the thermal comfort zone. The Hygrochron, a small wireless device which measures both temperature and RH, would be suitable and convenient in exercise or sleep studies. However, the RH measurement has not been validated. This paper has three parts. Part 1: In evaluating the sensor surface for RH detection, four Hygrochrons were placed on a wet paper towel. Two were placed on the towel with the protruding surface facing up and the other two facing down. The results showed that the Hygrochron with the protruding side was the sensor surface for detecting RH. Part 2: Twenty-seven Hygrochrons were calibrated in a humidity calibration chamber at a RH range from 40 to 90% at a constant temperature from 32 to 37°C. The mean bias was −1.08% between the Hygrochrons and the calibration chamber. The Hygrochron overestimated RH at the lower range (40–60%) and underestimated RH at the higher range (80–90%). The application of individual regression equations to each Hygrochron improved accuracy and reduced the mean bias to −0.002%. However, one Hygrochron showed outlier values that may be due to a manufacturing defect. Part 3: The reproducibility of Hygrochron for RH measurements was tested twice at the same condition of 35°C over a three-month interval. The intra-class coefficient was 0.996 to 1.000 with non-significant differences in the mean RH between test and re-test results (p=0.159). Hygrochrons are valid for RH measurements which show high reproducibility. It is recommended that Hygrochrons be calibrated over a range of desired RH and temperature prior to use to improve accuracy and detect any manufacturing defects.

Dyadic Short Forms of the Wechsler Adult Intelligence Scale-IV.

Full Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) administration can be time-consuming and may not be necessary when intelligence quotient estimates will suffice. Estimated Full Scale Intelligence Quotient (FSIQ) and General Ability Index (GAI) scores were derived from nine dyadic short forms using individual regression equations based on data from a clinical sample (n = 113) that was then cross validated in a separate clinical sample (n = 50). Derived scores accounted for 70%-83% of the variance in FSIQ and 77%-88% of the variance in GAI. Predicted FSIQs were strongly associated with actual FSIQ (rs = .73-.88), as were predicted and actual GAIs (rs = .80-.93). Each of the nine dyadic short forms of the WAIS-IV was a good predictor of FSIQ and GAI in the validation sample. These data support the validity of WAIS-IV short forms when time is limited or lengthier batteries cannot be tolerated by patients.

Estimating the inhaled dose of pollutants during indoor physical activity

BackgroundIt is undeniable that many benefits come from physical activity. People exercise in fitness centers to improve their health and well-being, prevent disease and to increase physical attractiveness. However, these facilities join conditions that cause poor indoor air quality. Moreover, increased inhalation rates during exercise have influence on inhaled doses of air pollution. ObjectivesThis study aims to calculate the inhaled dose of air pollutants during exercise, by estimating minute ventilation of participants and measuring air pollutant concentrations in fitness centers. MethodsFirstly, the 20 participants performed an incremental test on a treadmill, where heart rate and minute ventilation were measured simultaneously to develop individual exponential regression equations. Secondly, heart rate was measured during fitness classes and minute ventilation was estimated based on the calculated regression coefficients. Finally, the inhaled dose of air pollutants was calculated using the estimated minute ventilation and the concentrations of the pollutants measured in a monitoring program performed in 63 fitness classes. ResultsEstimated inhaled doses were higher in aerobic classes than in holistic classes. The main difference was registered for PM10 inhaled dose that presented an average ratio between aerobic and holistic classes greater than four. Minute ventilation and PM10 concentrations in aerobic classes were, on average, 2.0 times higher than in holistic classes. Results showed that inhalation of pollutants is increased during heavy exercise, demonstrating the need to maintain high indoor air quality in fitness centers. ConclusionsThis study illustrates the importance of inclusion minute ventilation data when comparing inhaled doses of air pollution between different population groups. This work has estimated for the first time the minute ventilation for different fitness classes. Also constitutes an important contribution for the assessment of inhaled dose in future studies to be performed in fitness centers.

Should Women “Ditch The Workout And Join The Party”? Physiological And Psychological Benefits Of Zumba

PURPOSE: to investigate the physiological and psychological effects of an 8-week intervention based on Zumba in healthy moderately active women. METHODS: forty-four women were randomly allocated to a Zumba group (n = 22, age: 26.6±5.4 years old; height: 165.8±7.1cm) and a control group (n = 22, age: 27.9±6.0 years old; height: 164.7±6.2cm). Each participant took part in one pre-test and one post-test sessions (psychology questionnaires, anthropometric measurements, and a running economy and maximal oxygen consumption (VO2max) tests) before and after an 8-week period with either a home-based Zumba intervention (Zumba group) or no intervention (control group). Mean heart rate (HRmean) was calculated during the Zumba sessions. VO2 values were extrapolated from HR data recorded during the Zumba sessions, using the individual regression equations from the incremental test. Student T-tests assessed between group differences in the data variations between pre- and post-tests, and Pearson correlations were used to evaluate the relation between the changes in all variables in the Zumba group. RESULTS: Compared to the control group, the Zumba group significantly decreased their running economy and significantly improved their VO2max (p 0.05). The Zumba group also experienced significantly greater increases in perceived strength (+16.3±14.2% vs. +5.4±10.4%), Autonomy (+8.0±9.4% vs. -3.6±9.0%) and Purpose (+4.4±6.5% vs. -3.2±9.6%), p < 0.05, compared to the control group. Finally, baseline body fat was significantly related to the change in sport perception (r = -0.492, p < 0.05) and relationship with others (r = -0.415, p < 0.05). Significant correlations were also observed between the improvement in VO2max and the change in the perception of one’s fitness (r = 0.638, p < 0.05), and between the changes in body fat and the variation perception of one’s body (r = -0.730, p < 0.01). CONCLUSIONS: This is the first study to show the benefits of a home-based Zumba Fitness intervention on fitness and psychological well-being, and there were links between the physiological and psychological changes observed. However, a longer intervention might be necessary for weight loss.

Influence of Al2O3 Filler on Slurry Erosion Behavior of Glass/Epoxy Composites

In the present study, slurry erosion behavior of glass/epoxy composites incorporated with alumina fillers was investigated. Glass/epoxy composites were incorporated with 5%, 10% and 15% alumina fillers, in addition unfilled composites were used in the study. Slurry pot erosion test was conducted on the samples. Slurry concentration, contact angle and speed were considered as the parameters. Abrasive slurry used in the study includes sand particles in the range of 170μm to 250μm suspended in the tap water. Tests were conducted in accordance L27 orthogonal array for obtaining the results in a systematic manner. ANOVA was used to study the contribution of individual parameters and regression equations were developed to predict the response. The results reveal that slurry erosion was found to be increased with increase slurry concentration and turning speed. The increase in contact angle had resulted in the increase of erosion till it reaches 60°, further increase in contact angle leads to the drop of erosion volume revealing semiductile nature of composites. ANOVA analysis had illustrated that slurry erosion and angle are the significant influencing factors on the response, contribution of speed was less significant. The present regression models were validated with the experimental results and found to be feasible.

ASYMPTOTIC THEORY IN FIXED EFFECTS PANEL DATA SEEMINGLY UNRELATED PARTIALLY LINEAR REGRESSION MODELS

This paper deals with statistical inference for the fixed effects panel data seemingly unrelated partially linear regression model. The model naturally extends the traditional fixed effects panel data regression model to allow for semiparametric effects. Multiple regression equations are permitted, and the model includes the aggregated partially linear model as a special case. A weighted profile least squares estimator for the parametric components is proposed and shown to be asymptotically more efficient than those neglecting the contemporaneous correlation. Furthermore, a weighted two-stage estimator for the nonparametric components is also devised and shown to be asymptotically more efficient than those based on individual regression equations. The asymptotic normality is established for estimators of both parametric and nonparametric components. The finite-sample performance of the proposed methods is evaluated by simulation studies.

Validity and reliability of temperature measurement by heat flow thermistors, flexible thermocouple probes and thermistors in a stirred water bath

We determined the validity and reliability of heat flow thermistors, flexible thermocouple probes and general purpose thermistors compared with a calibrated reference thermometer in a stirred water bath. Validity (bias) was defined as the difference between the observed and criterion values, and reliability as the repeatability (standard deviation or typical error) of measurement. Data were logged every 5 s for 10 min at water temperatures of 14, 26 and 38 °C for ten heat flow thermistors and 24 general purpose thermistors, and at 35, 38 and 41 °C for eight flexible thermocouple probes. Statistical analyses were conducted using spreadsheets for validity and reliability, where an acceptable bias was set at ±0.1 °C. None of the heat flow thermistors, 17% of the flexible thermocouple probes and 71% of the general purpose thermistors met the validity criterion for temperature. The inter-probe reliabilities were 0.03 °C for heat flow thermistors, 0.04 °C for flexible thermocouple probes and 0.09 °C for general purpose thermistors. The within trial intra-probe reliability of all three temperature probes was 0.01 °C. The results suggest that these temperature sensors should be calibrated individually before use at relevant temperatures and the raw data corrected using individual linear regression equations.

Minute ventilation of cyclists, car and bus passengers: an experimental study.

BackgroundDifferences in minute ventilation between cyclists, pedestrians and other commuters influence inhaled doses of air pollution. This study estimates minute ventilation of cyclists, car and bus passengers, as part of a study on health effects of commuters' exposure to air pollutants.MethodsThirty-four participants performed a submaximal test on a bicycle ergometer, during which heart rate and minute ventilation were measured simultaneously at increasing cycling intensity. Individual regression equations were calculated between heart rate and the natural log of minute ventilation. Heart rates were recorded during 280 two hour trips by bicycle, bus and car and were calculated into minute ventilation levels using the individual regression coefficients.ResultsMinute ventilation during bicycle rides were on average 2.1 times higher than in the car (individual range from 1.3 to 5.3) and 2.0 times higher than in the bus (individual range from 1.3 to 5.1). The ratio of minute ventilation of cycling compared to travelling by bus or car was higher in women than in men. Substantial differences in regression equations were found between individuals. The use of individual regression equations instead of average regression equations resulted in substantially better predictions of individual minute ventilations.ConclusionThe comparability of the gender-specific overall regression equations linking heart rate and minute ventilation with one previous American study, supports that for studies on the group level overall equations can be used. For estimating individual doses, the use of individual regression coefficients provides more precise data. Minute ventilation levels of cyclists are on average two times higher than of bus and car passengers, consistent with the ratio found in one small previous study of young adults. The study illustrates the importance of inclusion of minute ventilation data in comparing air pollution doses between different modes of transport.

Use of Accelerometers as a Means of quantifying Swim Training Load

Training load prescription and an athlete's adherence to it are flip sides of the same problematic coin. PURPOSE: To determine whether or not a commercially available accelerometer is capable of assessing swimmer's distance and velocity during an assigned interval training bout. METHODS: Six competitive swimmers (4 male, 2 female) were fitted with two accelerometers (placed on their right wrist and ankle) while completing a 50, 100, 200, and 400m even paced freestyle swim set, as well as a progressive set of 4 x 50m freestyle swims (i.e. each consecutive 50 m is swum faster). On a separate day, swimmers completed an interval swim training session composed of varying distances (m) and intensities (velocities in m&*;sec−1) with all bouts timed and recorded by an independent observer. Accelerometer output from this session and the individual regression equations were then given to a third party not present during the training bout. Estimated velocity and distance were calculated and compared to measured values. RESULTS: Linear regression analysis resulted in equations using accelerometer output to calculate swim distance (m) and swim velocity (example: swim distance = 0.005 * Accelerometer output - 5.271, r=0.99, p<0.05 and swim velocity = 0.001 * Accelerometer output + 0.980, r = 0.97). The correlation between actual and predicted swim bout distance was high (r=0.97) with statistical significance (p<0.05) and an average error of 16% over the distances tested. Similar analysis utilizing accelerometer output to estimate swim bout velocity resulted in r = 0.97, also significant, and an average error of 10.75% over the velocities measured. CONCLUSION: The results suggest that to accurately quantify a competitive swim training session, an individual regression equation can be developed for each swimmer. The results encourage the use of activity monitors as a simple, yet non-invasive method to evaluate specific characteristics of a swimmer's actual training load and remotely quantify training. Additional work is needed to refine the equations as a means to reduce the current magnitude of the error.

Relationships Between Energetic, Stroke Determinants, and Velocity in Butterfly

The purpose of this study was to identify the relationship between the bioenergetical and the biomechanical variables (stroke parameters), through a range of swimming velocities, in butterfly stroke. Three male and one female butterflier of international level were submitted to an incremental set of 200-m butterfly swims. The starting velocity was 1.18 m . s (-1) for the males and 1.03 m . s (-1) for the female swimmer. Thereafter, the velocity was increased by 0.05 m . s (-1) after each swim until exhaustion. Cardio-pulmonary and gas exchange parameters were measured breath by breath for each swim to analyze oxygen consumption and other energetic parameters by portable metabolic cart (K4b (2), Cosmed, Rome, Italy). A respiratory snorkel and valve system with low hydrodynamic resistance was used to measure pulmonary ventilation and to collect breathing air samples. Blood samples from the ear lobe were collected before and after each swim to analyze blood lactate concentration (YSI 1500 L, Yellow Springs, US). Total energy expenditure (E (tot)), energetic cost (EC), stroke frequency (SF), stroke length (SL), mean swimming velocity (V), and stroke index (SI) were calculated for each lap and average for each 200-m stage. Correlation coefficients between E (tot) and V, EC, and SF, as well as between EC and SI were statistically significant. For the relation between EC and SL, only one regression equation presented a correlation coefficient with statistical significance. Relations between SF and V, as well as between SI and V were significant in all of the swimmers. Only two individual regression equations presented statistically significant correlation coefficient values for the relation established between V and the SL. As a conclusion, the present sample of swims demonstrated large inter individual variations concerning the relationships between bioenergetic and biomechanical variables in butterfly stroke. Practitioners should be encouraged to analyze the relationships between V, SF, and SL individually to detect the deflection point in SL in function of swimming velocity to further determine appropriate training intensities when trying to improve EC.

Submaximal Cardiovascular Fitness Testing As An Alternative To Maximal Oxygen Consumption Testing In Teenagers

Cardiovascular (CV) fitness is often expressed as maximal oxygen consumption (VO2max). However, the practical value of VO2max testing is weakened because many subjects do not meet objective physiologic criteria for VO2max and frequently find maximal testing to be aversive. PURPOSE To evaluate the use of oxygen consumption at a heart rate of 170 bpm (VO2-170) as a submaximal index of CV fitness. METHODS VO2-170 and VO2max (mL/kg/min) were obtained with a multi-stage treadmill test in black and white 14–19 year olds (n=659). Percent body fat (%BF) was measured with dual-energy x-ray absorptiometry. Using all the treadmill workloads completed, we computed individual regression equations of VO2 on HR for each subject. RESULTS The VO2 (in L/min) corresponding to a HR of 170 bpm was calculated for each subject and expressed per unit of body weight (mL/kg/min). Group comparisons were made on unweighted means to test differences between subjects who achieved (n=376) and who did not achieve VO2max (n=283), using age, sex, race, and the sex by race interaction as covariates. Those who achieved VO2max had a significantly lower body mass index (22.75 vs 23.80 kg/m2, p<0.05), waist circumference (73.83 vs 75.74 cm, p<0.05), percent body fat (22.80 vs 25.19, p<0.001), and fat mass (15.20 vs 17.64 kg, p<0.01). Those who achieved VO2max had a significantly higher VO2peak (27.87 vs 26.36 mL/kg/min, p<0.01). To facilitate comparisons in projects that do not push the subjects to maximal effort, we derived a regression equation to predict VO2max from VO2-170. The equation also included age, race, and sex, and accounted for 73% of the variance in VO2max. CONCLUSIONS Our data suggest that in studies of adolescents it is preferable to measure CV fitness with a submaximal and objectively-measured index such as VO2-170 rather than with VO2max because subjects who do not achieve VO2max have significantly different body composition from those who do. Supported by NHLBI(64157).