Energy cost of walking in boys who differ in adiposity but are matched for body mass

Cardiopulmonary Capacity in Overweight and Obese Children and Adolescents: A Cross-Sectional Study

Background: One of the objective methods of assessing the level of cardiopulmonary capacity in overweight and obese children and adolescents is cardiopulmonary exercise testing (CPET).

Aims: The purpose of present study is an evaluation of aerobic capacity in high body mass index (BMI) children and adolescents by comparing them with a normal weight control group by CPET.

Methods and Procedures: The subjects were recruited from participants of the Program of Treatment for Overweight and Obese Children organized by a local pediatric rehabilitation center in Poland. Based on BMI for age and gender, two validation groups were selected: (1) a group of overweight children (n = 49) and (2) a group of obese children (n = 48). The study included also 53 normal weight participants as a reference group (REF). The study consisted of two parts: anthropometric measurements and CPET. The Godfrey protocol for CPET was applied.

Outcomes and Results: In this study, obese children and adolescents showed similar absolute VO_2peak values in liters per minute (1.64 L/min) compared to overweight children (1.48 L/min), but significantly higher than children with normal body weight (1.39 L/min). The obese children and adolescents presented lower VO_2peak in relation to body weight (25.44 ml/kg/min) compared to their peers with normal body weight (36.5 ml/kg/min), and overweight children (29.18 ml/kg/min).

Conclusion and Implications: The main finding of our study was recognition of significant differences between cardiopulmonary capacity parameters in obese children in comparison not only to normal weight peers, but to overweight, too.

A systematic review on biomechanical characteristics of walking in children and adolescents with overweight/obesity: Possible implications for the development of musculoskeletal disorders

It is known that obesity is associated with biomechanical alterations during locomotor tasks, which is considered a potential risk factor for the development of musculoskeletal disorders (MSKD). However, the association of obesity with biomechanical alterations of walking in the early stages of life have not yet been systematically reviewed. Thus, this review aims to summarize the biomechanical characteristics of walking in children and adolescents with overweight/obesity (OW/OB) versus their normal-weight (NW) counterparts. PubMed and Web of Science were systematically searched until November 2018. We found strong and moderate evidence supporting biomechanical differences in the gait pattern of OW/OB with respect to NW. Based on strong evidence, the gait patterns of OW/OB present greater pelvis transversal plane motion, higher hip internal rotation, higher hip flexion, extension and abduction moments and power generation/absorption, greater knee abduction/adduction motion, and higher knee abduction/adduction moments and power generation/absorption. Based on moderate evidence, OW/OB walk with greater step width, longer stance phase, higher tibiofemoral contact forces, higher ankle plantarflexion moments and power generation, and greater gastrocnemius and soleus activation/forces. These biomechanical alterations during walking in OW/OB could play a major role in the onset and progression of MSKD.

Body Size and Movement

Humans of different sizes move in very similar ways despite the size difference. The principles of geometric scaling provide insight into the reasons for the similar movement patterns observed. In human locomotion, body size influences endurance running performance, with shorter body sizes being an advantage due to better heat exchange compared with their taller counterparts. Scaling can also show the equivalence of child gait with that of adults in terms of stride length and walking velocity. In humans, maximum jump height is independent of standing height, a scaling result which has been validated by examining jumps with mass added to the body. Finally, strength scales in proportion to body mass to the two-thirds power, which explains why shorter people have greater relative body strength compared with taller individuals. Geometric scaling reveals the underlying principles of many human movement forms.

Effect of Body Composition on Walking Economy

Purpose. The aim of the study was to evaluate walking economy and physiological responses at two walking speeds in males with similar absolute body mass but different body composition. Methods. The study involved 22 young men with similar absolute body mass, BMI, aerobic performance, calf and thigh circumference. The participants differed in body composition: body fat (HBF group) and lean body mass (HLBM group). In the graded test, maximal oxygen uptake (VO

Effect of body composition on respiratory compensation point during an incremental test

Body mass (BM) and composition are considered to be significant determinants of aerobic endurance. The purpose of this study was to examine the influence of BM and its composition makeup on endurance performance. Thirty-nine men were divided into 3 groups of significantly different BM and mass composition: a control group, a group with high body fat (HBF), and a group with high lean body mass (HLBM). Participants in the HBF and HLBM groups had similar BM, which was significantly greater than observed in the control group. All participants performed an incremental treadmill test to volitional failure. Endurance performance was assessed on the basis of respiratory compensation point (RCP). The HBF and HLBM groups exceeded RCP at a much lower work intensity, expressed as %HRmax and %VO2max, compared with the control group. When considered relative to BM and lean body mass, oxygen consumption values at RCP were significantly less in the HBF and HLBM groups compared with the control group. Increased BM, regardless of its composition, substantially reduced aerobic endurance performance. Therefore, athletes and coaches should pay attention to not only the percentage of body fat but also to the amount of lean body mass because any gain may adversely affect aerobic endurance performance.

Cardiorespiratory fitness in children: a simple screening test for population studies

Cardiorespiratory fitness is one measure of body functions, and its assessment should play an important role in the activities associated with the promotion of physical activity as an important component of a healthy lifestyle. This study aimed to develop a reference system of the mean post-exercise heart rate (HRmean post-ex) after a 3-min step test for use in screening the cardiorespiratory fitness of 6- to 12-year-old children. The study included 14,501 children ages 6-12 years from primary schools in Gdansk. The participants were subjected to the 3-min Kasch Pulse Recovery Test (KPR Test). The reference range for the classification of cardiorespiratory fitness was developed on the basis of the age-specific percentile distribution of HRmean post-ex in 6- to 9- and 10- to 12-year-old children. This study showed that the 3-min KPR Test is easy to perform and well tolerated by school-age children. As such, it can constitute a useful tool for health promoters and educators. The presented age- and gender-specific reference range of HRmean post-ex enables the assessment and monitoring of submaximal exercise-induced changes in the cardiovascular system and, consequently, the physical fitness of a given individual.

Predicting metabolic rate across walking speed: one fit for all body sizes?

We formulated a “one-size-fits-all” model that predicts the energy requirements of level human walking from height, weight, and walking speed. Our three-component model theorizes that the energy expended per kilogram per stride is independent of stature at mechanically equivalent walking speeds. We measured steady-state rates of oxygen uptake of 78 subjects who spanned a nearly twofold range of statures (1.07–2.11 m) and sevenfold range of body masses (16–112 kg) at treadmill speeds from 0.4 to 1.9 m/s. We tested the size independence of the model by deriving best-fit equations in the form of the model on four stature groups ( n ≥ 15): short, moderately short, moderately tall, and tall. The mean walking metabolic rates predicted by these four independently derived equations for the same set of reference subjects ( n = 16; stature range: 1.30–1.90 m) agreed with one another to within an average of 5.2 ± 3.7% at the four intermediate speeds in our protocol. We next evaluated the model's gross predictive accuracy by dividing our 78 subjects into 39 stature-matched pairs of experimental and validation group subjects. The model best-fit equation derived on the experimental group subjects predicted the walking metabolic rates of the validation group subjects to within an average of 8.1 ± 6.7% ( R2 = 0.90; standard error of estimate = 1.34 ml O2·kg−1·min−1). The predictive error of the American College of Sports Medicine equation (18.0 ± 13.1%), which does not include stature as a predictor, was more than twice as large for the same subject group. We conclude that the energy cost of level human walking can be accurately predicted from height, weight, and walking speed.

Mechanical efficiency during a cycling test is not lower in children with excess body weight and low aerobic fitness

OBJECTIVE

The aims of this study were to assess the association between (i) body weight status and mechanical efficiency (ME); and (ii) ME and aerobic fitness in children aged 8-10 years.

DESIGN AND METHODS

The sample included 464 prepubertal children (258 boys). A total of 288 were normal-weight (NW); 84 overweight (OW); and 92 obese (OB). Subjects performed an incremental maximal cycling test with indirect calorimetry. MEcrude (%) was calculated for the first five stages of the protocol (25, 50, 75, 100, and 125 W) as follows: work produced, in watts total energy consumption, in watts(-1) · 100(-1). For MEnet, resting energy consumption was subtracted from total energy consumption. Energy consumption was calculated as follows: (4.94 · respiratory exchange ratio + 16.04) · VO2, in ml · min(-1) · 60(-1).

RESULTS

MEcrude was significantly higher in NW compared to OW and OB children and in OW compared to OB children at 25, 50, 75, 100, and 125 W. In contrast, MEnet did not differ significantly among NW, OW, and OB children. No statistically significant association was found between crude or net ME and peak oxygen consumption (VO2 peak; in ml · kg(-1) · min(-1)); therefore, the ability to transfer chemical energy to mechanical work is maintained in children aged 8-10 years old regardless of body weight status and aerobic fitness. Moreover, higher values of MEcrude during exercise are explained by elevated oxygen consumption at rest and not by energy consumed during physical activity.

CONCLUSIONS

These results highlight that prepubertal children are equally efficient since they are able to perform a physical task such as cycling using the same proportion of energy regardless of their body weight status.

Physical activity, fitness and the energy cost of activities: implications for obesity in children and adolescents in the tropics

The tropics cover a large section of the world in which both developed and developing countries are situated. Rapid socioeconomic development, modernization, urbanization, and globalization have affected both the food market and physical activity (PA), which in turn have propelled the obesity epidemic in the tropics. There is growing concern that overweight and obesity are emerging as major health problems among children and adolescents in the tropics, despite the fact that undernutrition still exists in many of these countries. Physical inactivity, a low metabolic rate, and lack of physical fitness (PF) have been linked to overweight and obesity. Moreover, PF in several tropical countries is declining, and these changes may be a threat to future health, as low PA and PF levels are important risk factors for noncommunicable chronic diseases. Previous studies have reported that the relationships among PA, PF, overweight, and obesity are inconsistent and inconclusive. There is no indication that variances in the energy cost of physical activities lead to obesity. Despite a lack of definite evidence to prove a causal relationship, there is enough certainty that physical inactivity and low fitness levels are linked to overweight and obesity. Hence, people living in tropical countries need to be encouraged to lead a healthier lifestyle by increasing their PA levels and reducing sedentary behaviors to prevent overweight or obesity.

[Therapy of juvenile obesity from the sports medicine/science viewpoint]

Overweight and obesity in children and adolescents had reached its highest level worldwide. In the development of overweight and within interdisciplinary training programs, physical activity and the avoidance of sedentary habits play an important role. Not only is there an increase in energy consumption, but potential comorbidities (e.g., cardiovascular risk factors) are improved. In addition, positive psychosocial benefits occur, e.g., increasing self-esteem, personal, and social skills. During realization, possible risks (e.g., exercise-induced asthma) and barriers have to be taken into account. In terms of physical activity programs, the child's surroundings have to be integrated, and transfer into daily routine should be promoted. Therefore, in addition to athletic content, daily activities have to be trained and supported, e.g., via pedometers. At least 60, better 90 and more minutes of physical activity per day are recommended; the use of audiovisual media should be reduced to a minimum (max. 120 minutes).

Childhood obesity and walking: guidelines and challenges

The development and maintenance of excess body mass in many children is partly attributable to levels of physical activity that are lower than the recommended 60 minutes/day. Walking is a recommended form of physical activity for obese children, due to its convenience and perceived ease of adoption. Unfortunately, studies that have used objective physical activity assessment continue to report low step counts and levels of physical activity in obese children. This may be due to physiological and/or biomechanical factors that make walking more difficult for obese children. The purpose of this review is to highlight the current recommended and measured levels of physical activity for children and to discuss the physiological and biomechanical challenges of walking for obese children that may help explain why these children are not meeting physical activity goals.

Recognition of physical activities in overweight Hispanic youth using KNOWME Networks

BACKGROUND

KNOWME Networks is a wireless body area network with 2 triaxial accelerometers, a heart rate monitor, and mobile phone that acts as the data collection hub. One function of KNOWME Networks is to detect physical activity (PA) in overweight Hispanic youth. The purpose of this study was to evaluate the in-laboratory recognition accuracy of KNOWME.

METHODS

Twenty overweight Hispanic participants (10 males; age 14.6 ± 1.8 years), underwent 4 data collection sessions consisting of 9 activities/session: lying down, sitting, sitting fidgeting, standing, standing fidgeting, standing playing an active video game, slow walking, brisk walking, and running. Data were used to train activity recognition models. The accuracy of personalized and generalized models is reported.

RESULTS

Overall accuracy for personalized models was 84%. The most accurately detected activity was running (96%). The models had difficulty distinguishing between the static and fidgeting categories of sitting and standing. When static and fidgeting activity categories were collapsed, the overall accuracy improved to 94%. Personalized models demonstrated higher accuracy than generalized models.

CONCLUSIONS

KNOWME Networks can accurately detect a range of activities. KNOWME has the ability to collect and process data in real-time, building the foundation for tailored, real-time interventions to increase PA or decrease sedentary time.

Obesity: the new childhood disability?

This review addresses the impact of obesity on paediatric physical functioning utilizing the World Health Organization International Classification of Functioning, Disability and Health Framework (ICF). The ICF encompasses functioning (as it relates to all body functions and structures), activities (undertaking a particular task) and participation (in a life situation) with disability referring to impairments in body functions/structures, activity restrictions or participation limitations. Electronic databases were searched for peer-reviewed studies published in English prior to May 2009 that examined aspects of physical functioning in children (≤18 years). Eligible studies (N = 104) were ranked by design and synthesized descriptively. Childhood obesity was found to be associated with deficits in function, including impaired cardiorespiratory fitness and performance of motor tasks; and there was some limited evidence of increased musculoskeletal pain and decrements in muscle strength, gait and balance. Health-related quality of life and the subset of physical functioning was inversely related to weight status. However, studies investigating impacts of obesity on wider activity and participation were lacking. Further research utilizing the ICF is required to identify and better characterize the effects of paediatric obesity on physical function, activity and participation, thereby improving targets for intervention to reduce disability in this population.

The mass-specific energy cost of human walking is set by stature

The metabolic and mechanical requirements of walking are considered to be of fundamental importance to the health, physiological function and even the evolution of modern humans. Although walking energy expenditure and gait mechanics are clearly linked, a direct quantitative relationship has not emerged in more than a century of formal investigation. Here, on the basis of previous observations that children and smaller adult walkers expend more energy on a per kilogram basis than larger ones do, and the theory of dynamic similarity, we hypothesized that body length (or stature, Lb) explains the apparent body-size dependency of human walking economy. We measured metabolic rates and gait mechanics at six speeds from 0.4 to 1.9 m s–1 in 48 human subjects who varied by a factor of 1.5 in stature and approximately six in both age and body mass. In accordance with theoretical expectation, we found the most economical walking speeds measured (J kg–1 m–1) to be dynamically equivalent (i.e. similar U, where U=velocity2/gravity · leg length) among smaller and larger individuals. At these speeds, stride lengths were directly proportional to stature whereas the metabolic cost per stride was largely invariant (2.74±0.12 J kg–1 stride–1). The tight coupling of stature, gait mechanics and metabolic energy expenditure resulted in an inverse relationship between mass-specific transport costs and stature (Etrans/Mb∝Lb–0.95, J kg–1 m–1). We conclude that humans spanning a broad range of ages, statures and masses incur the same mass-specific metabolic cost to walk a horizontal distance equal to their stature.

Do mechanical gait parameters explain the higher metabolic cost of walking in obese adolescents?

Net metabolic cost of walking normalized by body mass ( CW·BM−1; in J·kg−1·m−1) is greater in obese than in normal-weight individuals, and biomechanical differences could be responsible for this greater net metabolic cost. We hypothesized that, in obese individuals, greater mediolateral body center of mass (COM) displacement and lower recovery of mechanical energy could induce an increase in the external mechanical work required to lift and accelerate the COM and thus in net CW·BM−1. Body composition and standing metabolic rate were measured in 23 obese and 10 normal-weight adolescents. Metabolic and mechanical energy costs were assessed while walking along an outdoor track at four speeds (0.75–1.50 m/s). Three-dimensional COM accelerations were measured by means of a tri-axial accelerometer and gyroscope and integrated twice to obtain COM velocities, displacements, and fluctuations in potential and kinetic energies. Last, external mechanical work (J·kg−1·m−1), mediolateral COM displacement, and the mechanical energy recovery of the inverted pendulum were calculated. Net CW·BM−1 was 25% higher in obese than in normal-weight subjects on average across speeds, and net CW·BM−67 (J·kg−0.67·m−1) was significantly related to percent body fat ( r2 = 0.46). However, recovery of mechanical energy and the external work performed (J·kg−1·m−1) were similar in the two groups. The mediolateral displacement was greater in obese subjects and significantly related to percent body fat ( r2 = 0.64). The mediolateral COM displacement, likely due to greater step width, was significantly related to net CW·BM−67 ( r2 = 0.49). In conclusion, we speculate that the greater net CW·BM−67 in obese subjects may be partially explained by the greater step-to-step transition costs associated with wide gait during walking.

An exploratory study of cardiac function and oxygen uptake during cycle ergometry in overweight children

OBJECTIVE

Obesity has been proposed to negatively impact cardiac function in overweight (OW) individuals. The relationship between diastolic dysfunction and oxygen uptake (Vo(2)) kinetics is equivocal. This exploratory investigation evaluated the relationship between resting left ventricular function and Vo(2) kinetics during cycle ergometry in OW and non-overweight (NO) children and adolescents.

RESEARCH METHODS AND PROCEDURES

Fourteen OW (>85 percentile for BMI for age and gender) children, 10 boys and 4 girls (age, 11.7 +/- 1.9 years; body mass, 80.6 +/- 45.5 kg) and 10 NO children (4 boys, 6 girls) volunteered to participate in the study (age, 12.5 +/- 2.1 years; body mass, 45.8 +/- 13.8 kg). Resting cardiovascular structure and function were assessed using spectral Doppler echocardiography. All subjects underwent two sub-maximal exercise stages on a cycle ergometer (3 minutes unloaded and 5 minutes at 50 W, both at a cadence of 50 rpm). Respiratory data were measured on a breath-by-breath basis at both workloads and the mean response time (MRT) was calculated.

RESULTS

Analysis of the MRT data demonstrated that there were no significant differences between OW and NO (OW, 52.6 +/- 11.7 seconds vs. NO, 45.6 +/- 7.4 seconds). Significant correlations (p < 0.05) were obtained between MRT Vo(2) and echocardiographic-derived mitral valve inflow pressure half-time (r = 0.55) and between MRT Vo(2), and mitral valve inflow deceleration time (r = 0.55).

DISCUSSION

The evidence from this research suggests a possible link between left ventricular diastolic function at rest and oxygen uptake kinetics during sub-maximal exercise in OW and NO children and adolescents.

The impact of childhood obesity on musculoskeletal form

Despite the greater prevalence of musculoskeletal disorders in obese adults, the consequences of childhood obesity on the development and function of the musculoskeletal system have received comparatively little attention within the literature. Of the limited number of studies performed to date, the majority have focused on the impact of childhood obesity on skeletal structure and alignment, and to a lesser extent its influence on clinical tests of motor performance including muscular strength, balance and locomotion. Although collectively these studies imply that the functional and structural limitations imposed by obesity may result in aberrant lower limb mechanics and the potential for musculoskeletal injury, empirical verification is currently lacking. The delineation of the effects of childhood obesity on musculoskeletal structure in terms of mass, adiposity, anthropometry, metabolic effects and physical inactivity, or their combination, has not been established. More specifically, there is a lack of research regarding the effect of childhood obesity on the properties of connective tissue structures, such as tendons and ligaments. Given the global increase in childhood obesity, there is a need to ascertain the consequences of persistent obesity on musculoskeletal structure and function. A better understanding of the implications of childhood obesity on the development and function of the musculoskeletal system would assist in the provision of more meaningful support in the prevention, treatment and management of the musculoskeletal consequences of the condition.

Effects of obesity and sex on the energetic cost and preferred speed of walking

The metabolic energy cost of walking is determined, to a large degree, by body mass, but it is not clear how body composition and mass distribution influence this cost. We tested the hypothesis that walking would be most expensive for obese women compared with obese men and normal-weight women and men. Furthermore, we hypothesized that for all groups, preferred walking speed would correspond to the speed that minimized the gross energy cost per distance. We measured body composition, maximal oxygen consumption, and preferred walking speed of 39 (19 class II obese, 20 normal weight) women and men. We also measured oxygen consumption and carbon dioxide production while the subjects walked on a level treadmill at six speeds (0.50–1.75 m/s). Both obesity and sex affected the net metabolic rate (W/kg) of walking. Net metabolic rates of obese subjects were only ∼10% greater (per kg) than for normal-weight subjects, and net metabolic rates for women were ∼10% greater than for men. The increase in net metabolic rate at faster walking speeds was greatest in obese women compared with the other groups. Preferred walking speed was not different across groups (1.42 m/s) and was near the speed that minimized gross energy cost per distance. Surprisingly, mass distribution (thigh mass/body mass) was not related to net metabolic rate, but body composition (% fat) was ( r2= 0.43). Detailed biomechanical studies of walking are needed to investigate whether obese individuals adopt novel energy saving mechanisms during walking.

The biomechanics of restricted movement in adult obesity

In spite of significant advances in the knowledge and understanding of the multi-factorial nature of obesity, many questions regarding the specific consequences of the disease remain unanswered. In particular, there is a relative dearth of information pertaining to the functional limitations imposed by overweight and obesity. The limited number of studies to date have mainly focused on the effect of obesity on the temporospatial characteristics of walking, plantar foot pressures, muscular strength and, to a lesser extent, postural balance. Collectively, these studies have implied that the functional limitations imposed by the additional loading of the locomotor system in obesity result in aberrant mechanics and the potential for musculoskeletal injury. Despite the greater prevalence of musculoskeletal disorders in the obese, there has been surprisingly little empirical investigation pertaining to the biomechanics of activities of daily living or into the mechanical and neuromuscular factors that may predispose the obese to injury. A better appreciation of the implications of increased levels of body adiposity on the movement capabilities of the obese would afford a greater opportunity to provide meaningful support in preventing, treating and managing the condition and its sequelae. Moreover, there is an urgent need to establish the physical consequences of continued repetitive loading of major structures of the body, particularly of the lower limbs in the obese, during the diverse range of activities of daily living.

Overweight children reduce their activity levels earlier in life than healthy weight children

OBJECTIVE

To determine differences in the time overweight and nonoverweight youth spend on light, moderate, hard, and very hard activity plus gender and age differences in activity patterns.

DESIGN AND SETTING

This study was a cross-sectional design in a primary care hospital.

PARTICIPANTS

A total of 197 children and adolescents (4-16 years) participated. The overweight group (n = 107) were on a waiting list for an obesity treatment program and were defined as overweight, with a body mass index >95th percentile, and the nonoverweight group (n = 90) were volunteers recruited via advertisements and had a body mass index <75th percentile. INTERVENTIONS AND OUTCOME MEASUREMENTS: To determine activity patterns and perception of activity level, an interview was conducted with the child and a parent using a validated 7-day recall. Body fat was measured with bioelectrical impedance.

RESULTS

There was a negative correlation between adiposity and total amount of activity performed, with the amount of moderate activity the best predictor of obesity. Girls did less activity than boys whether overweight or not. Between the ages of 4 and 7 years, overweight and nonoverweight subjects did similar amounts of activity. In the older subjects, the activity of the overweight was less than in nonoverweight. The overweight subjects perceived themselves to be just as active as others their same age and sex.

CONCLUSIONS

Clinicians need to be aware that overweight children and adolescents are less active than nonoverweight children at an earlier age, particularly females, but feel that their activity level is similar to that of nonobese children.