A dynamical systems approach for the submaximal prediction of maximum heart rate and maximal oxygen uptake

This study examines the viability of utilizing a dynamical system model and heuristic parameter estimation algorithm to make predictions for maximum heart rate (\(\mathrm {HR_{max}}\)) and maximal oxygen uptake (\(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\)) using data collected from a submaximal testing protocol. \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\) is widely considered to be the best single measurement of overall fitness in humans. When a \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\) assessment is not available, \(\mathrm {HR_{max}}\) is often used to prescribe exercise intensities for training and rehabilitation. In the absence of maximal cardiopulmonary exercise testing (CPET), \(\mathrm {HR_{max}}\) and \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\) are typically estimated using traditional submaximal prediction methods with well-known limitations and inaccuracies. For this study, 12 regularly exercising healthy young adult males performed a bout of maximal CPET on a cycle ergometer to determine their true \(\mathrm {HR_{max}}\) and \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\). Participants also performed a submaximal bout of exercise at varied intensities. A dynamical system model and heuristic parameter estimation algorithm were applied to the submaximal data to estimate the participants’ \(\mathrm {HR_{max}}\) and \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\). The submaximal predictions were evaluated by computing the coefficient of determination \({R^2}\) and the standard error of the estimate (SEE) through comparisons with the true maximal values for \(\mathrm {HR_{max}}\) (\({R^2 = 0.96}\), SEE = 2.4 bpm) and \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\) (\({R^2 = 0.93}\), SEE = 2.1 mL kg\(^{-1}\) min\(^{-1}\)). The results from this study suggest that a dynamical system model and heuristic parameter estimation algorithm can provide accurate predictions for \(\mathrm {HR_{max}}\) and \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\) using data collected from a submaximal testing protocol.     

The relationship between heart rate reserve and oxygen uptake reserve in children and adolescents

The purpose of the present study was to examine the relationship between oxygen uptake (VO2) and heart rate (HR) responses during rest and exercise in Chinese children and youth and to evaluate the relationships between maximal heart rate (%HRmax), heart rate reserve (%HRR), peak oxygen uptake (% VO2peak), and oxygen uptake reserve (% VO2R) in Chinese children and youth. Forty-nine Chinese children and youth were studied at rest and during a graded maximal exercise test on treadmill. Resting, submaximal and peak HR and VO2 were collected. Regression analyses were conducted to investigate the associations between the various forms of HR and VO2 measures. The equivalency between %HRR and % VO2R for adults was examined for children using data obtained in this study. Results indicated that all regression lines between HR measures and VO2 measures were significantly different from the line of identity (p < .05), except the regression line for %HRR versus %VO2 peak in boys. The equivalency between % VO2R and % HRR for adults was not demonstrated in children and adolescents in this study. In contrast, %HRR was more closely equivalent to % VO2 peak. Because a strong linear relationship was found between HR and VO2, HR measures, in terms of either %HRmax or %HRR, would still be a practical variable for prescribing appropriate exercise intensity for children and adolescents. Unlike results found for adults, a given % HRR in children and youth was not equivalent to its corresponding % VO2R.     

影响儿童青少年最大有氧活动能力的因素(综述)

儿童青少年在青春发育期前后,机体各组织器官的功能都在迅速的提高.儿童青少年VO2max的研究和测定,可以综合反映儿童青少年体格状况、有氧运动机能,是判断儿童青少年发育水平及不同环境因素对儿童青少年体质影响的比较理想的动态机能指标.通过综述了前人对儿童青少年最大有氧活动能力的研究,特别是影响其有氧能力的遗传因素、个体状况、环境因素和训练因素在儿童青少年生长发育期的作用和特点,使大家正确认识儿童青少年这一能力的发展,关心儿童青少年的健康成长.     

The influence of ventilatory control on heart rate variability in children

The aim of this study was to determine the influence of breathing frequency and tidal volume on resting heart rate variability in children aged 9 years (n = 29) and 16 years (n = 19). Heart rate variability was measured in four conditions: (1) without the control of ventilation followed at random by (2) a fixed breathing frequency of 12 breaths x min(-1), (3) a breathing frequency of 12 breaths x min(-1) but with a fixed tidal volume of 30% vital capacity and (4) a fixed breathing frequency of 6 breaths x min(-1) and a tidal volume of 30% vital capacity. A total of 128 RR intervals (the time between two spikes in the heart rate) were detected and absolute high- and low-frequency spectral components were calculated using autoregressive modelling. The younger children were unable to control ventilation to achieve conditions 3 and 4; therefore, a 2 x 2 (group x condition) analysis of variance was used to analyse conditions 1 and 2. There were significant interactions between group and heart rate variability conditions for the low-frequency component and the ratio of low to high frequencies (P < 0.001). The main effect for condition showed that at 12 breaths x min(-1) with no fixed tidal volume there was a significantly higher standard deviation of the RR interval, total power and high-frequency (P< 0.01) and low-frequency spectral components (P < 0.05) than in the condition with no ventilatory control. Across the four breathing conditions for the older participants, the high-frequency spectral component was significantly higher in the condition at 6 breaths x min(-1) with a fixed tidal volume than in that with no ventilatory control (P < 0.005); the ratio of high to low frequencies was significantly lower for the spontaneous condition than those performed at 12 breaths x min(-1) (P < 0.001). The results provide evidence of the need for ventilatory control when assessing short-term resting heart rate variability in children.     

The influence of ventilatory control on heart rate variability in children

The aim of this study was to determine the influence of breathing frequency and tidal volume on resting heart rate variability in children aged 9 years ( n = 29) and 16 years ( n = 19). Heart rate variability was measured in four conditions: (1) without the control of ventilation followed at random by (2) a fixed breathing frequency of 12 breaths· min -1 , (3) a breathing frequency of 12 breaths· min -1 but with a fixed tidal volume of 30% vital capacity and (4) a fixed breathing frequency of 6 breaths·min -1 and a tidal volume of 30% vital capacity. A total of 128 RR intervals (the time between two spikes in the heart rate) were detected and absolute high- and low-frequency spectral components were calculated using autoregressive modelling. The younger children were unable to control ventilation to achieve conditions 3 and 4; therefore, a 2 2 2 (group 2 condition) analysis of variance was used to analyse conditions 1 and 2. There were significant interactions between group and heart rate variability conditions for the low-frequency component and the ratio of low to high frequencies ( P ? 0.001). The main effect for condition showed that at 12 breaths· min -1 with no fixed tidal volume there was a significantly higher standard deviation of the RR interval, total power and high-frequency ( P ? 0.01) and lowfrequency spectral components ( P ? 0.05) than in the condition with no ventilatory control. Across the four breathing conditions for the older participants, the high-frequency spectral component was significantly higher in the condition at 6 breaths· min -1 with a fixed tidal volume than in that with no ventilatory control ( P ? 0.005); the ratio of high to low frequencies was significantly lower for the spontaneous condition than those performed at 12 breaths· min -1 ( P ? 0.001). The results provide evidence of the need for ventilatory control when assessing short-term resting heart rate variability in children.     

Effect of asthma and six-months high-intensity interval training on heart rate variability during exercise in adolescents

ABSTRACT

Little is known regarding the influence of asthma and exercise, and their interaction, on heart rate variability (HRV) in adolescents.

Thirty-one adolescents with asthma (13.7±0.9 years; 21.9±3.9 kg·m^?2; 19 boys, 12 girls) and thirty-three healthy adolescents (13.8±0.9 years; 20.3±3.2 kg·m^?2; 16 boys, 17 girls) completed an incremental ramp test and three heavy-intensity constant-work-rate cycle tests. Thirteen adolescents (7 boys, 6 girls; 6 asthma, 7 control) completed six-months high-intensity interval training (HIIT) and were compared to age- and sex-matched controls. Standard time-domain, frequency-domain and non-linear indices of HRV were derived at baseline, three- and six-months.

Asthma did not influence HRV at baseline or following HIIT. Total power, low frequency and normalised low frequency power, and sympathovagal balance increased at three-months in HIIT, subsequently declining towards baseline at six-months. Normalised high frequency power was reduced at three-months in both groups, which was sustained at six-months. No effects of HIIT were observed in the time-domain nor in the non-linear indices.

HRV was not influenced by asthma, potentially because such derangements are a function of disease progression, severity or duration. HIIT may be associated with a short-term shift towards greater sympathetic predominance during exercise, perhaps caused by physiological overload and fatigue.     

Effects of adding a preceding run-up on performance, blood lactate concentration and heart rate during maximal intermittent vertical jumping

In this study, we examined the effects of a prior run-up on intermittent maximal vertical jump performance. Seven regionally ranked male volleyball players volunteered to participate in the study. They performed three randomized tests: (1) six repeated intermittent maximal jumps (jump condition), (2) six repeated intermittent run-ups (run-up condition), and (3) six repeated run-ups followed by maximal jumps (run-up plus jump condition). All performances were assessed and blood lactate concentration and heart rate were measured before and after each of the tests. Mean ( +/- ) jump performance (64.7 +/- 2.3 cm) increased significantly (P = 0.02) over the course of the jump condition and was significantly higher (P < 0.001) than for the run-up plus jump condition (58.0 +/- 3.2 cm), which tended to decrease with repetition. Blood lactate concentration was significantly higher in the run-up plus jump condition (3.73 +/- 0.24 mmol . l(-1)) than in the jump (2.61 +/- 0.26 mmol . l(-1), P = 0.02) and run-up (2.86 +/- 0.18 mmol . l(-1), P = 0.03) conditions. The increase in heart rate was significantly higher both in the run-up plus jump condition (33 +/- 6 beats . min(-1), P = 0.05) and run-up condition (33 +/- 4 beats . min(-1), P = 0.02) than in the jump condition (21 +/- 3 beats . min(-1)). The results indicate that the addition of run-ups probably impeded performance in the repetition of vertical jumps.     

Maximal oxygen uptake versus maximal power output in children

Maximal oxygen uptake VO(2max)) is considered the optimal method to assess aerobic fitness. The measurement of VO(2max), however, requires special equipment and training. Maximal exercise testing with determination of maximal power output offers a more simple approach. This study explores the relationship between [Vdot]O(2max) and maximal power output in 247 children (139 boys and 108 girls) aged 7.9-11.1 years. Maximal oxygen uptake was measured by indirect calorimetry during a maximal ergometer exercise test with an initial workload of 30 W and 15 W x min(-1) increments. Maximal power output was also measured. A sample (n = 124) was used to calculate reference equations, which were then validated using another sample (n = 123). The linear reference equation for both sexes combined was: VO(2max) (ml x min(-1)) = 96 + 10.6 x maximal power + 3.5 . body mass. Using this reference equation, estimated VO(2max) per unit of body mass (ml x min(-1) x kg(-1)) calculated from maximal power correlated closely with the direct measurement of VO(2max) (r = 0.91, P <0.001). Bland-Altman analysis gave a mean limits of agreement of 0.2+/-2.9 (ml x min(-1) x kg(-1)) (1 s). Our results suggest that maximal power output serves as a good surrogate measurement for VO(2max) in population studies of children aged 8-11 years.     

Maximal oxygen uptake versus maximal power output in children

Abstract

Maximal oxygen uptake ([Vdot]O_2max) is considered the optimal method to assess aerobic fitness. The measurement of [Vdot]O_2max, however, requires special equipment and training. Maximal exercise testing with determination of maximal power output offers a more simple approach. This study explores the relationship between [Vdot]O_2max and maximal power output in 247 children (139 boys and 108 girls) aged 7.9–11.1 years. Maximal oxygen uptake was measured by indirect calorimetry during a maximal ergometer exercise test with an initial workload of 30 W and 15 W · min^?1 increments. Maximal power output was also measured. A sample (n = 124) was used to calculate reference equations, which were then validated using another sample (n = 123). The linear reference equation for both sexes combined was: [Vdot]O_2max (ml · min^?1) = 96 + 10.6 · maximal power + 3.5 · body mass. Using this reference equation, estimated [Vdot]O_2max per unit of body mass (ml · min^?1 · kg^?1) calculated from maximal power correlated closely with the direct measurement of [Vdot]O_2max (r = 0.91, P <0.001). Bland-Altman analysis gave a mean limits of agreement of 0.2±2.9 (ml · min^?1 · kg^?1) (1 s). Our results suggest that maximal power output serves as a good surrogate measurement for [Vdot]O_2max in population studies of children aged 8–11 years.     

Injuries during football tournaments in 45,000 children and adolescents

Four percent of the world’s population, or 265 million people, play football, and many players are injured every year. The present study investigated more than 1800 injuries in over 45,000 youth players participating in three consecutive international football tournaments in Denmark in 2012–2014. The aim was to investigate the injury types and locations in children and adolescent football players and the differences between genders and age groups (11–15 and 16–19 years of age). An overall injury rate of 15.3 per 1000 player hours was found. The most common injury location was lower extremities (66.7%), and the most common injury type was contusion (24.4%). Girls had a relative risk of injury of 1.5 compared with boys, p?p?p?相似文献   

Health-enhancing physical activity and sedentary behaviour in children and adolescents

We provide a wide-ranging review of health-related physical activity in children and adolescents using a behavioural epidemiology framework. In contrast to many other reviews, we highlight issues associated with true sedentary behaviours alongside physically active behaviours. Specifically, we review the evidence concerning the links between physical activity and cardiovascular disease, overweight and obesity, psychosocial measures, type II diabetes, and skeletal health. Although the evidence is unconvincing at times, several factors lead to the conclusion that promoting physical activity in youth is desirable. A review of the prevalence of physical activity and sedentary behaviours shows that many young people are active, but this declines with age. A substantial number are not adequately active for health benefits and current trends in juvenile obesity are a cause for concern. Prevalence data on sedentary behaviours are less extensive but suggest that total media use by young people has not changed greatly in recent years. Most children and adolescents do not exceed recommended daily hours of TV viewing. Physical activity is unrelated to TV viewing. We also identified the key determinants of physical activity in this age group, highlighting demographic, biological, psychological, behavioural, social and environmental determinants. Interventions were considered for school, family and community environments. Finally, policy recommendations are offered for the education, governmental, sport and recreation, health, and mass media sectors.     

Health-enhancing physical activity and sedentary behaviour in children and adolescents

We provide a wide-ranging review of health-related physical activity in children and adolescents using a behavioural epidemiology framework. In contrast to many other reviews, we highlight issues associated with true sedentary behaviours alongside physically active behaviours. Specifically, we review the evidence concerning the links between physical activity and cardiovascular disease, overweight and obesity, psychosocial measures, type II diabetes, and skeletal health. Although the evidence is unconvincing at times, several factors lead to the conclusion that promoting physical activity in youth is desirable. A review of the prevalence of physical activity and sedentary behaviours shows that many young people are active, but this declines with age. A substantial number are not adequately active for health benefits and current trends in juvenile obesity are a cause for concern. Prevalence data on sedentary behaviours are less extensive but suggest that total media use by young people has not changed greatly in recent years. Most children and adolescents do not exceed recommended daily hours of TV viewing. Physical activity is unrelated to TV viewing. We also identified the key determinants of physical activity in this age group, highlighting demographic, biological, psychological, behavioural, social and environmental determinants. Interventions were considered for school, family and community environments. Finally, policy recommendations are offered for the education, governmental, sport and recreation, health, and mass media sectors.     

Measurement of maximal muscle cross-sectional area of the elbow extensors and flexors in children,teenagers and adults

Abstract

The aims of this study were to examine age and sex differences in elbow extensor and flexor anatomical muscle cross-sectional area (mCSA) measured by magnetic resonance imaging (MRI) and the location of maximal mCSA as a percentage of the distance from the distal to the proximal end of the humerus. Ninety-five individuals spread across the age groups 9 – 10 years, 16 – 17 years and 21 years participated in the study. Muscle cross-sectional area derived from the manual MRI tracing proved to be highly reliable in terms of limits of agreement (?2.5 to 1.5 cm²) and the intraclass correlation coefficient (ICC = 0.998). A sex-by-age group analysis of variance revealed significant effects (P < 0.01) of sex, group and a sex-by-group interaction, the latter reflecting a greater increase in males than females of upper arm mCSA from childhood to adulthood. Extensor mCSA was more proximal (55 ± 6%) than that of the flexors (28 ± 6%). A significant effect (P < 0.01) of group was found for location of maximal extensor mCSA, reflecting its more distal position with increasing age. Measurements of muscle size should be made at the individually determined position of maximal mCSA if interpreting data collected during growth and maturation, especially if the muscle group of interest is the elbow extensors and if different age groups are being monitored.     

Measurement of maximal muscle cross-sectional area of the elbow extensors and flexors in children, teenagers and adults

The aims of this study were to examine age and sex differences in elbow extensor and flexor anatomical muscle cross-sectional area (mCSA) measured by magnetic resonance imaging (MRI) and the location of maximal mCSA as a percentage of the distance from the distal to the proximal end of the humerus. Ninety-five individuals spread across the age groups 9 - 10 years, 16 - 17 years and ?21 years participated in the study. Muscle cross-sectional area derived from the manual MRI tracing proved to be highly reliable in terms of limits of agreement (-2.5 to 1.5 cm(2)) and the intraclass correlation coefficient (ICC = 0.998). A sex-by-age group analysis of variance revealed significant effects (P < 0.01) of sex, group and a sex-by-group interaction, the latter reflecting a greater increase in males than females of upper arm mCSA from childhood to adulthood. Extensor mCSA was more proximal (55 +/- 6%) than that of the flexors (28 +/- 6%). A significant effect (P < 0.01) of group was found for location of maximal extensor mCSA, reflecting its more distal position with increasing age. Measurements of muscle size should be made at the individually determined position of maximal mCSA if interpreting data collected during growth and maturation, especially if the muscle group of interest is the elbow extensors and if different age groups are being monitored.     

Relationship of tennis play to executive function in children and adolescents

This study evaluated the association between the frequency of tennis play and executive function in children and adolescents. One hundred and six junior tennis players (6–15 years old) participated in this study. Executive function, including inhibitory control, working memory, and cognitive flexibility were evaluated at rest. Females showed better inhibitory control and cognitive flexibility than males. In males, more frequent tennis play was associated with higher basic processing speed and inhibitory control after controlling for age, gender, body mass index (BMI), and tennis experience. More frequent tennis play was associated with better working memory in both males and females after controlling for age, gender, BMI, and tennis experience. Furthermore, longer tennis experience was related to better cognitive flexibility in males after controlling for age, gender, BMI, and frequency of tennis play. These findings suggest that tennis play is associated with the development of three foundational aspects of executive function (i.e. inhibitory control, working memory, cognitive flexibility). Especially, frequent participation in tennis play is related to better inhibitory control and working memory, while longer experience of tennis play is associated with better cognitive flexibility. Although development of inhibitory control and cognitive flexibility is slower in males than in females, the associations between tennis play and inhibitory control and cognitive flexibility appear to be larger in males than in females.