1,050 research outputs found

    A mathematical model for predicting HR max, VO2 max, and oxygen uptake kinetics during treadmill walking and running at varied intensities

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    Maximal oxygen uptake (VO2 max) is difficult to measure and most predictions are inaccurate due to a variety of assumptions. The purpose of this study was to validate a dynamical system model (DSM) for predicting HR max and VO2 max during walking and running. A secondary purpose was to predict VO2 responses using a neural network. Twenty-six healthy males completed a maximal cardiopulmonary exercise test (CPET) and a submaximal protocol. The models were applied to the submaximal data to estimate the participants’ HR/VO2 responses and predict their HR max and VO2 max. The model accurately tracked HR and VO2 responses (R2 = -.85-0.99). However, it did not accurately estimate max (R2 < 0). Further refinement of the model is needed. This study elucidated some of the challenges of using a DSM and demonstrated that a neural network may be useful for easily predicting VO2 responses.Master of Art

    Rowing-ramp protocol as a cardiopulmonary exercise test for hemiparetic stroke survivors

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    Cardiopulmonary capacity should be evaluated accurately to determine exercise intolerance and training intensity of stroke survivors before an exercise rehabilitation programme is prescribed. However, no cardiopulmonary exercise test (CPET) is suitable because of the stroke victims’ physical impairment. The aim of this study was to develop and validate a new rowing-ramp protocol as a CPET for stroke survivors. Eleven stroke patients (6 male; 5 female; age, 45 + 16.01 years, performed two incremental exercise tests on a Concept II rowing ergometer to determine the peak oxygen consumption (VO2 peak). Test-retest reliability for VO2 peak, measured 1-week apart, resulted in an intra-class correlation of 0.97 and 0.95, respectively. A linear regression equation was developed to predict the VO2 peak from final stage stroke power. Validity and reliability of the prediction equation were established. The regression equation for predicted VO2 peak was VO2 peak=11.429±+ 0.232 (Final Stage Stroke Power) + 12.63 (F=25.326, p<0.01; R=0.859, R2=0.738). Limits of agreement between predicted and measured VO2 peak were acceptable, with a mean bias of 0.37 ml/kg/min. The validity coefficient (R) was 0.83 (p<0.01) and 0.81 (p<0.01) in both trials. Test-Retest reliability coefficient for predicted VO2 peak 0.95 (p<0.01). The positive relationship between Final Stage Stroke Power and VO2 peak suggests that the Rowing-Ramp protocol could be used to measure VO2 peak of stroke survivors. Additional studies are needed to cross-validate the regression equation using larger sample size, different type and severity of stroke

    Prediction of oxygen uptake (VO2) using neural networks

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    This thesis focuses on using neural network models for the prediction of oxygen uptake (VO2). The predictions are made using regression techniques. The dataset contains independent predictor variables such as heart rate (HR), energy expenditure (EE), height, body mass, gender and age. VO2 is the output dependent variable. The goal is to evaluate and compare the performance of neural networks to other machine learning techniques such as support vector machines and multiple linear regression. Few neural network models have been tested previously in the literature for maximal oxygen uptake (VO2max) prediction. During the last decade, most approaches have focused on support vector machines and linear regression equations. In this thesis, data collected at the University of Jyväskylä is used to create a dataset for the prediction of VO2. A detailed statistical analysis has been performed to see the relationship between speed, VO2 and energy expenditure. Using 8 different combinations of predictor variables, neural network’s performance and the effect of predictor variables on the performance is measured. Data pre-processing is performed. R2 value and root mean square error value is used for measuring the performance of the machine learning models. Same data set is used for all models to ensure accurate results. The results of this thesis show that speed, VO2 and energy expenditure have a direct relationship. Males show higher energy produced as compared to females. The neural network model outperformed support vector machine and multiple linear regression by resulting in accurate predictions, high R2 value and low root mean square value. The highest accuracy is achieved with the model containing all predictor variables. The inclusion of HR as a predictor variable is important due to its effect on the performance of the model. Further advancements in neural networks can allow more accurate VO2 predictions, the model can also be used in a wearable device for real-time VO2 prediction. The same approach can be extended to predict VO2max values

    Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 133)

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    This special bibliography lists 276 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in September 1974

    Cardiorespiratory fitness estimation using wearable sensors: laboratory and free-living analysis of context-specific submaximal heart rates

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    In this work, we propose to use pattern recognition methods to determine submaximal heart rate (HR) during specific contexts, such as walking at a certain speed, using wearable sensors in free-living, and use context-specific HR to estimate cardiorespiratory fitness (CRF). CRF of 51 participants was assessed by a maximal exertion test (VO2max). Participants wore a combined accelerometer and HR monitor during a laboratory based simulation of activities of daily living and for two weeks in free-living. Anthropometrics, HR while lying down and walking at predefined speeds in laboratory settings were used to estimate CRF. Explained variance (R2) was 0.64 for anthropometrics, and increased up to 0.74 for context-specific HR (0.73 to 0.78 when including fat-free mass). Then, we developed activity recognition and walking speed estimation algorithms to determine the same contexts (i.e. lying down and walking) in free-living. Context-specific HR in free-living was highly correlated with laboratory measurements (Pearson's r = 0.71-0.75). R2 for CRF estimation was 0.65 when anthropometrics were used as predictors, and increased up to 0.77 when including free-living context-specific HR (i.e. HR while walking at 5.5 km/h). R2 varied between 0.73 and 0.80 when including fat-free mass among the predictors. RMSE was reduced from 354.7 ml/min to 281.0 ml/min by the inclusion of context-specific HR parameters (21% error reduction). We conclude that pattern recognition techniques can be used to contextualize HR in free-living and estimated CRF with accuracy comparable to what can be obtained with laboratory measurements of HR response to walking

    Aerospace medicine and biology: A continuing bibliography with indexes, supplement 129, June 1974

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    This special bibliography lists 280 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1974

    On the Use of a Test to Exhaustion Specific to Tennis (TEST) with Ball Hitting by Elite Players.

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    PURPOSE: We aimed to a) introduce a new Test to Exhaustion Specific to Tennis (TEST) and compare performance (test duration) and physiological responses to those obtained during the 20-m multistage shuttle test (MSST), and b) determine to which extent those variables correlate with performance level (tennis competitive ranking) for both test procedures. METHODS: Twenty-seven junior players (8 males, 19 females) members of the national teams of the French Tennis Federation completed MSST and TEST, including elements of the game (ball hitting, intermittent activity, lateral displacement), in a randomized order. Cardiorespiratory responses were compared at submaximal (respiratory compensation point) and maximal loads between the two tests. RESULTS: At the respiratory compensation point oxygen uptake (50.1 ± 4.7 vs. 47.5 ± 4.3 mL.min(-1).kg(-1), p = 0.02), but not minute ventilation and heart rate, was higher for TEST compared to MSST. However, load increment and physiological responses at exhaustion did not differ between the two tests. Players' ranking correlated negatively with oxygen uptake measured at submaximal and maximal loads for both TEST (r = -0.41; p = 0.01 and -0.55; p = 0.004) and MSST (r = -0.38; P = 0.05 and -0.51; p = 0.1). CONCLUSION: Using TEST provides a tennis-specific assessment of aerobic fitness and may be used to prescribe aerobic exercise in a context more appropriate to the game than MSST. Results also indicate that VO2 values both at submaximal and maximal load reached during TEST and MSST are moderate predictors of players competitive ranking

    Quarter-mile walk test sensitive to training-induced fitness changes

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    BACKGROUND: Cardiorespiratory fitness (CRF) is an important aspect of the overall health of an individual and its monitoring must be promoted in the general population. Thus, the aim of the study was to cross-validate and improve CRF estimation based on quarter-mile Rockport Fitness Walking Test. METHODS: Thirty participants (31.4±7.99 years) were randomized in either a four-week aerobic training group (10 men and 10 women) or a control group (eight men and two women). CRF was assessed via VO2max test and estimated via quarter-mile Rockport Fitness and Ebbeling treadmill tests, before and after the training intervention. The original quarter-mile Rockport VO2max estimation was found to greatly overestimate CRF by 22 mL/kg/min. When its coefficient was updated according to our data, it largely improved (by 6.8 mL/kg/min). Furthermore, a new algorithm for predicting VO2max was designed using multi-linear regression analysis. RESULTS: The original quarter-mile Rockport Fitness Walking Test was not sensitive to CRF changes. It showed changes in VO2max, which were significantly different from the actual observed changes (-1.1±4.08 vs. 1.61±2.84, P=0.02, respectively). The Ebbeling treadmill test appeared to systematically overestimate CRF changes. Our new algorithm showed improved sensitivity for detecting CRF changes and stability. CONCLUSIONS: The original quarter-mile Rockport Fitness Walking Test equation for predicting VO2max was neither accurate nor sensitive to changes in CRF, most likely due to cardiovascular drift. Our new algorithm, based on the same brisk walking test, can provide a more accurate estimate of CRF, which is also sensitive to VO2max changes, in a broad age range (18 to 50 years)

    The impact of exercise in children and adolescents with movement impairment

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    The relationship between level of movement skill and fitness in children and adolescents plays an important role in improving physical activity (PA) and health. Children with poor motor proficiency and coordination categorised as having movement impairment (MI) often choose a more sedentary lifestyle as a consequence of their movement difficulties and inefficient movement patterns. The literature has highlighted the association between movement difficulties and disengagement with sport and play; citing physiological and psychosocial aspects as limiting factors. Furthermore, children with MI who do engage in PA often participate at lower intensities and fail to attain recommended levels. Consequently, there is limited knowledge regarding how youth respond to various exercise intensities in relationship to MI. Additional research is warranted to fully understand the neurophysiological mechanisms (underpinnings) and limitations that may explain the association between PA and movement skills in MI. Therefore, the aim of this thesis is to better understand the physiological and perceptual responses during and following exercise of different intensities for exercise prescription in children and adolescents with movement impairment (MI). A comprehensive, systematic literature review was conducted of the recent available studies on interventions focused on PA and fitness in children and adolescents with MI (Chapter 2). This review provided the background for the other three studies included in this thesis and evaluated the efficacy of interventions on physical fitness and psychosocial outcomes. The findings highlighted the range of intervention designs that have the potential for improving physical fitness and performance, however, larger RCT studies with follow-up periods are needed. In Chapter 3, a review of the common methods used to describe and measure components of fitness was summarised. The primary focus of this chapter was to review the background literature validating and providing a rationale for the methods used throughout this thesis. In Chapter 4, the physiological and perceptual responses during and following an acute bout of high and low-intensity exercise was explored in a randomized crossover design (study 1). Participants were categorized as MI (n=17) and no movement impairment (NMI) (n=21) on the Bruininks-Oseretsky Test of Motor Proficiency 2 Short Form (BOT-2 SF) and performed an incremental bike test to establish aerobic capacity. Heart rate (HR), rating of perceived exertion (RPE), muscle strength (torque) and fatigue (EMG) was assessed pre-and post-exercise in the following two sessions. Significant differences in maximal oxygen uptake (V̇O2peak) (MI: 31.5±9.2 vs. NMI: 40.0±9.5 ml·kg·min1), PPO (MI: 157±61 vs. NMI: 216±57 watts, p.05) or RPE at either intensity for legs (MI: 8±2 vs. NMI: 7±2, p>.05) and overall (MI: 7±3 vs. NMI: 6±2, p>.05). The results highlighted a reduced exercise capacity in MI compared to NMI and potentially suggest central (i.e., motivation and perceived adequacy) rather than peripheral factors may limit exercise performance in MI. In Chapter 5, the criterion validity of the Åstrand-Rhyming (A-R) cycle test and the Chester Step Test (CST) for assessment of V̇O2peak in field settings was conducted (study 2). The first part of this study established the criterion validation (n=18) and reliability (n=8) of the Åstrand cycle test to measure and estimate aerobic capacity in children and adolescents. The second part consisted of validating the CST for mass screening purposes (n=20) utilised in Chapter 6. The A-R cycle test overestimated V̇O2peak by 10-15% and demonstrated a moderate reliability (R=0.84) when repeated. Similarly, the CST overestimated V̇O2peak by 10% confirming that submaximal data should be interpreted with caution but are a feasible option for measuring aerobic fitness across varying levels of MI. To further build upon the findings in study 1 and 2 (Chapter 4 and 5), the final study aimed to provide a pathway for identifying adolescents (13-14 year olds) with MI and lower fitness levels based on an adapted screening process within Year 9 students (n=522). Individuals performing in the <25th percentile of their class were invited to join the EPIC (Engagement, Participation, Inclusion and Confidence in sport and play) feasibility study, a 6-week gym intervention (EPIC Club) offered twice weekly consisting of cardiovascular and strength training elements. Out of the 155 adolescents identified and recruited to join EPIC, 31 participants enrolled in the study. Pre- and post-intervention assessments were performed to monitor changes in fitness outcomes. The intervention pilot period had a high attendance rate (~90%) with participants reaching target exercise intensities between 65-95% HRmax during the sessions. However, no significant changes were observed pre- and post-intervention. Collectively, these studies provide novel insight on the physiological underpinnings and perceptual factors contributing to exercise tolerance in MI. Furthermore, the screening process and targeted recruitment approach for the EPIC study intervention served as a feasible pathway for identifying adolescents with MI and lower fitness levels in school settings. Strategies that increase fitness parameters and development of movement skills in childhood may be a vital target for improving PA and play in youth with MI. Keywords: Movement impairment, movement difficulties, motor coordination, developmental coordination disorder, fitness, physical activity, randomised controlled trial, feasibility, exercise, intensit

    The Interrelationships Between Predicted And Actual Measures Of Max VO2 And Running Performance

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    This study investigated the interrelationships between predicted Max VO2, actual Max VO2 and various running performances of individuals from three subject groups. More specifically, the study attempted to ascertain within a composite and each of three ability subgroups: (1) the relationship between actual Max VO2 and predicted Max VO2; (2) the correlations between actual oxygen uptake (L/min. and ml/kg/min.) and half-mile, mile, and three-mile performance times; (3) the relationship between predicted Max VO2 and performance in the half-mile, mile, and three-mile run; and (4) the significance of the difference among the correlation coefficients obtained between the predicted and actual measures of oxygen uptake (ml/kg/min.) and running performance . . . The relationships between predicted oxygen uptake and running performance were significant for the composite group at each distance vs. MAX VO2 ml/kg/min. and the trained runners at half mile (L/min.). The t value obtained for the differences among the correlation coefficients revealed significance for the trained runner sub-group at the half-mile and mile. With one exception, the relationships between actual and predicted Max VO2 (ml/kg/min.) increased as a function of distance
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