Overweight (OW) and obesity (OB) are often associated with low levels of physical activity. Physical activity is recommended to reduce excess body weight, prevent body weight regain, and decrease the subsequent risks of developing metabolic and orthopedic conditions. However, the impact of OW and OB on motor function and daily living activities must be taken into account. OW and OB are associated with musculoskeletal structure changes, decreased mobility, modification of the gait pattern, and changes in the absolute and relative energy expenditures for a given activity. While changes in the gait pattern have been reported at the ankle, knee, and hip, modifications at the knee level might be the most challenging for articular integrity. This review of the literature combines concepts and aims to provide insights into the prescription of physical activity for this population. Topics covered include the repercussions of OW and OB on biomechanical and physiological responses associated with the musculoskeletal system and daily physical activity. Special attention is given to the effect of OW and OB in youth during postural (standing) and various locomotor (walking, running, and cycling) activities.
Excess body weight and a low level of physical activity are closely linked. The 2004 Canadian Community Health Survey showed that obesity rates in adults were significantly higher in sedentary men (27%) compared to both moderately active (17%) and active individuals (20%) [
Inactivity as a potential cause and/or result of OB is of great interest considering the growing obesity rates. Worldwide, over 400 million adults were reported to be OB in 2005, and by 2015, more than 700 million individuals are expected to have this condition [
The general purpose of this paper is to better understand the impact of OW and OB on motor activities, with a special focus on children. More specifically, Section
Overweight and obesity in adults lead to alterations of the musculoskeletal system that could put OB individual at higher risk of musculoskeletal pain [
Studies in children and adolescents also showed an effect of OW on both foot structure [
OB individuals have also been shown to modify the force alignment and consequently the distribution of forces at the knee during weight bearing. This has led several researchers to link alterations in force distribution, particularly those associated with varus malalignment (the load-bearing axis is shifted inward, causing more stress and force on the medial compartment of the knee), to the development of OA in obese adults [
The muscular system is a complementary component to consider. Zoico et al. [
During childhood, postural stability is considered to be a major component of the child’s development. Morphological changes due to growth interfere with postural stability and lead to high variability in balancing strategies in children less than 6 years old [
The authors also used the Bruininks-Oseretsky balance test scores. The Bruininks-Oseretsky subtest of balance consists of three tasks of static unipodal stance (on the floor and on a balance beam) with eyes open and eyes closed, as well as five tasks assessing dynamic balance using different walking conditions (walking on a line, walking forward on a balance beam, walking forward heel-to-toe on a line, walking forward heel-to-toe on a balance beam, and stepping over a stick on the balance beam) [
However, differences between OB and NW children have been reported even in tasks that required minimal muscular strength such as quiet standing. Using force platforms, static posturography showed that OW and OB during growth could interfere with postural stability [
Taken together these studies suggest that OB children may be disadvantaged when asked to stand still for a mid to long period of time and that they are more affected by visual conflict and foot placement than NW children. Nantel et al. [
Energy expenditure is another parameter that differs in the standing position according to body weight status. Lafortuna et al. [
In adults, an increased body weight leads to major modifications in the gait pattern. OW and OB individuals have been shown to walk with a shorter step length, lower cadence and velocity, a decrease in the duration of the simple support phase and an increased double support phase [
The spatiotemporal differences between NW and OW children are similar to those reported in adults. OW children have a longer gait cycle and stance phase duration as well as a reduced cadence and velocity compared to NW [
In addition to the possible long-term limitations, Hills et al. [
Butte et al. [
With this higher energy expenditure at greater walking speeds, due in part to excess body weight and lower mechanical efficiency, it should not be a surprise that the absolute aerobic performance of OB youth is lower. Mastrangelo et al. [
Sometimes, the difference between the cardiorespiratory fitness of NW and OW children does not reach statistical significance [
Structured physical activity programs can be beneficial to regulate body weight. The eight-month program conducted in Germany that includes behavioral and nutritional components reduced the disparities between OB children (
Several points must be taken into account regarding the CRF of OB children. First, a lower performance on a walk-run test, as characterized by a higher time to cover a given distance, a lower number of stages completed, a lower maximal speed, or a lower oxygen consumption expressed in ml × kg−1 × min−1 does not necessarily indicate a lower fitness profile. In fact, the absolute energy expenditure that OB individuals can generate can be higher despite a lower performance in terms of time or stages. An estimate of the energy deployed by the individuals can be estimated by multiplying the common CRF indicator (ml of oxygen consumed × kg−1 × min−1) by 0.021 kJ × ml of oxygen consumed−1, the mean energetic equivalent of oxygen, and by body weight, in kg. If everything other than body weight is held equal, an individual of 40 kg who jogs at 8 km × h−1, which represent eight metabolic equivalents or 28 ml × kg of body weight−1 × min−1, would expend 23.5 kJ × min−1. For a child 25% lighter (i.e., 30 kg), the energy expenditure would be reduced by a quarter, leading to an energy expenditure of 17.6 kJ per minute of jogging at the same speed. Considering the lower mechanical efficiency with increased body weight, it is possible that the energy expenditure of the heavier child is even higher than what general guidelines of energy expenditure suggest. No compendium of physical activity taking body weight status into consideration is currently available and individual assessment is necessary for precise measurements. If such measures are performed, the oxidative capacity of FFM is a good indicator of muscle quality that could also be measured. In order to appreciate this parameter, oxygen consumption can be reported per kg of FFM, assessed by bioimpedance scales or a DXA scan, for example. Then, more information on the abilities of muscles to perform cardiovascular work is available.
The measurement of ambulatory activities represents another important challenge from both the evaluation and intervention point of view. Pedometers are affordable devices that individuals can wear to provide objective measures of physical activity levels. Tudor-Locke et al. [
While walking and running are good physical activities to lose weight, they imply supporting body weight at each step. When an individual has an excess of body weight such locomotor activities are surely much difficult and may be associated with various musculoskeletal discomfort and or pain. An alternative is to look for nonweight bearing locomotor activities such as cycling. However, to our knowledge most studies looking at cycling in OB used a more physiological approach.
Obese youth expend more energy than non-OB individuals to perform activities in which the body weight is not supported. But what about energy expenditure when the body weight is supported? Studies addressing this question have been conducted with girls and women. A first study done with OB, OW, and NW girls indicates that the difference in energy expenditure during activities like cycling or riding a scooter are lower than that observed for walking [
Experimentally induced weight gain or weight loss is very informative to better understand the bioenergetics of weight changes. Goldsmith et al. [
At maximal exertion, similar [
Both OW and OB have been associated with changes in musculoskeletal structure and mobility. While changes in the gait pattern have been reported at the ankle, knee, and hip, modifications at the knee level might be the most challenging for articular integrity. Several studies have reported a knee overload in OB individuals when walking at a normal or fast speed and have highlighted a possible role in the development of OA. Consequently, a reduction in walking speed has been recommended to avoid musculoskeletal degeneration in OB adults. However, weight reduction was shown to reduce pain, improve mobility, and reduce the load at the knee in OB adults. A higher speed is one key parameter in weight reduction because of the associated higher energy expenditure, especially for individuals with a higher body weight status. Moreover, diet combined with a one-hour training program three times a week, including weight training and walking, was reported to maximize weight loss when compared to diet or exercise alone. In children, the higher mechanical energy expenditure while walking makes it a good exercise to lose weight. Higher intensity activities such as fast walking or activities with frequent speed changes should be proposed depending on the presence of pain or dynamic postural instability. These studies highlighted the complexity of physical activity prescription in OB populations, especially in the presence of postural instability, pain, or OA.
Activities in which the body weight is supported appear to be an alternative to high intensity activities with potentially fewer musculoskeletal constraints. To the best of our knowledge, no studies have documented the biomechanical parameters linked to OA and other disorders in OB individuals during cycling. Based on studies of individuals who were standing, walking or cycling, training on an elliptical trainer, in which the body weight is not necessarily supported by a device but where the individual stands and trains without the impact associated with walking or running, could be an interesting compromise. Again, this would need to be confirmed in further studies.
What emerges from current studies is that simple movements such as standing, walking at low speed and cycling without resistance or with very low resistance should not be neglected. They increase energy expenditure and could be part of a healthy lifestyle when included in training programs as active recovery. Building the confidence of OB individuals practicing physical activities, even if the intensity appears low, is important because some of them, potentially more girls, report low confidence in physical activity. Including how physical activity and the fitness profile are reported and interpreted could improve the compliance of an OB individual in physical activity. Addressing only the time to cover a distance or the frequency and intensity of activities performed without taking into account body weight and, thus, energy expenditure results in an underestimation of the actual work performed. For example, the ratio of total energy expenditure to basal energy expenditure in OW and NW children was reported to be similar for various activities including walking and cycling [
Obesity and OW are two conditions for which the impact on physical activities goes far beyond the important body fat accumulation. Major changes were noted for foot, knee, and hip structures and are associated with discomfort, pain, and illness. This can seriously impede daily physical activity level and limit the performance of OB and OW persons during fitness tests.
For exercise prescription, we have shown that not all activities present the same difficulties at different intensities. Cycling is more demanding at low intensity for OW and OB individuals while ambulatory activities are more difficult at high intensities. Strategies like slowing the self-selected walking pace, shortening step length, or reducing resistance should be considered in exercise prescription for individuals with excess body weight, and this includes children. A good understanding of biomechanical and physiological profile is mandatory for safe testing and effective prescription of physical activity in OW and OB individuals. Future researches should look at the effect of varying biomechanical constraints (cadence, step length, inclination) and physiological demands (various intensities) on energetic expenditure to optimize training effect.
J. Nantel and M.E. Mathieu are both first authors.