Obesity and walking describes how the locomotion of walking differs between an obese individual (BMI ≥ 30 kg/m2) and a non-obese individual. The prevalence of obesity is a worldwide problem. In 2007–2008, prevalence rates for obesity among adult American men were approximately 32% and over 35% amongst adult American women. [1] According to the Johns Hopkins Bloomberg School of Public Health, 66% of the American population is either overweight or obese and this number is predicted to increase to 75% by 2015. [2] Obesity is linked to health problems such as decreased insulin sensitivity and diabetes, [3] cardiovascular disease, [4] cancer, [5] sleep apnea, [6] and joint pain such as osteoarthritis. [7] It is thought that a major factor of obesity is that obese individuals are in a positive energy balance, meaning that they are consuming more calories than they are expending. Humans expend energy through their basal metabolic rate, the thermic effect of food, non-exercise activity thermogenesis (NEAT), and exercise. [8] While many treatments for obesity are presented to the public, exercise in the form of walking is an easy, relatively safe activity. Walking may initially result in reduced weight, but adopting the habit over the long term may not result in additional weight loss. [9]
Knee osteoarthritis and other joint pain are common complaints amongst obese individuals and are often a reason as to why exercise prescriptions such as walking are not continued after prescribed.[ citation needed ] To determine why an obese person might have more joint problems than a non-obese individual, the biomechanical parameters must be observed to see differences between obese and non-obese walking.[ citation needed ]
Numerous studies have examined the differences in stride between obese and non-obese individuals. Spyropoulos et al. in 1991 examined stride length, width, and joint angle differences between the two groups. They found that obese individuals take shorter (1.25 m vs. 1.67 m) and wider (0.16 m vs. 0.08 m) strides than their non-obese counterparts. [10] Browning and Kram also observed obese people taking wider strides (~30% greater) across differing walking speeds (0.50, 0.75, 1.00, 1.50, and 1.75 m/s), but the stride width did not change with differing speed. [11] They did not find stride lengths to be different across speeds. [11] Along with taking wider strides, several articles have found obese individuals to walk at slower velocities than their non-obese counterparts, claiming that this might be due to balance and body control while walking. [10] [12] [13] Ledin and Odkivst support this theory in a study when they added mass by way of a weighted shirt (20% body weight) to lean individuals and saw sway increase. [14] Increased sway has also been observed in pre-pubertal boys. [15] Though obese individuals may be able to accommodate for the extra mass in terms of balance because they walk with it every day, several studies have found that obese people spend more time in the stance rather than swing phase during the walking cycle and increase double support time. [10] [11] [13] [15] Slower cadences, or number of steps within a certain period of time, have also been associated with obese individuals when compared to lean individuals and would be expected with slower walking speeds. Others have found no difference in obese people walking velocities and find that they share a similar preferred walking speed with lean individuals. [11] [16] [17]
In a study by DeVita and Hortobágyi, obese people were found to be more erect throughout the stance phase with greater hip extension, less knee flexion, and more plantarflexion during the course of stance than non-obese people. [12] They also found that obese individuals had less knee flexion in early stance and greater plantarflexion at toe off. [12] In a study looking at knee extension, Messier et al. found a significant positive correlation with maximum knee extension and BMI. [18] That same study looked at mean angular velocities at the hip and ankle and found no difference between obese and lean individuals. [18]
A ground reaction force is the force that is exerted by the ground onto whatever body is in contact with the ground and is equal to the force that is placed on the ground. An example is the force that the ground exerts onto the foot and then up the leg of a person when walking and making contact with the ground. These can be measured by having a subject walk across a force platform and collect the forces exerted on the ground. These forces have long been thought to increase loads on the knee and would increase with greater mass from an obese person. This may be a predictor of osteoarthritis for an obese subject as the vertical force has been documented to potentially be the most significant force that is transmitted up the leg to the knee. [18] In 1996, Messier and colleagues observed the differences in ground reaction forces between obese and lean older adults with osteoarthritis. They found that when they accounted for age and walking velocity, the vertical force was significantly positively correlated with BMI. [18] Therefore, as BMI increased, the forces increased. They found this in not only the vertical force, but also in the anteroposterior and mediolateral forces. [18] Because of the study population, this study did not compare obese adults with lean counterparts. Browning and Kram in 2006 observed two groups (one obese and one non-obese group) of young adult’s ground reaction forces across different speeds. They found that absolute ground reaction forces were significantly greater for the obese people than the non-obese group at slower walking speeds and at each walking speed the peak vertical force was approximately 60% greater. [11] Absolute peak in the anteroposterior and mediolateral directions were also greater for the obese group but the difference was erased when scaled to body weight. [11] Forces were also greatly reduced at slower walking speeds. [11]
Lower extremity joint loading is estimated through net muscle moments, joint reaction forces, and joint loading rates. Net muscle moments can increase up to 40% as walking speeds rise from 1.2 to 1.5 m/s. [19] One could then predict that as speed increases, loads felt by the lower-extremity joints would increase as the net muscle moments and ground reaction forces increase. Browning and Kram have also found that stance-phase sagittal-plane net muscle moments are greater in obese adults when compared to lean individuals. [11]
It is well established that obese individuals expend a greater amount of metabolic energy at rest and when performing some physical activity such as walking than lean individuals,. [20] [21] [22] Added mass demands more energy to move. This is observed in a study by Foster et al. in 1995 when they took 11 obese women and calculated their energy expenditure before and after weight loss. They found that after significant weight loss, the subjects expended less energy on the same task as they did when they were heavier. [23] To determine if walking was more expensive per kilogram of body mass and if obese individuals preferred walking speeds would be slower, Browning and Kram sought to characterize the metabolic energy obese females would expend while walking across differing speeds. They found that walking for obese women was 11% more expensive per kilogram of body mass than lean individuals and that the obese women preferred to walk at a similar speed as the lean individuals that minimized their gross energy cost per distance. [17] Wanting to look at metabolic rates of obese men compared to obese women and determine if the adipose distribution (gynoid vs. android) differing between the sexes play a role in energy expenditure, Browning et al. observed class II obese males and females walking across differing speeds. They found that standing metabolic rate when normalized for body weight was ~20% less for obese people (more adipose tissue and less metabolically active tissue), but that metabolic rates during walking were ~10% greater per kilogram body mass for obese individuals when compared to lean. [16] These researchers also found that increased thigh mass and adipose distribution did not matter, overall body composition of percent body fat was related to net metabolic rate. [16] Therefore, obese individuals are using more metabolic energy than their lean counterparts when walking at the same speed.
Many measurements are normalized to body weight in order to account for differing body weights when doing comparisons (see VO2 max testing). Normalizing body weight when comparing obese and lean individuals' metabolic rates reduces the difference, indicating that body weight rather than body fat composition is the primary indicator for the metabolic cost of walking. [24] Caution must be taken when analyzing the scientific literature to understand if findings are normalized or not because they may be interpreted differently.
One possible suggested strategy to maximize energy expenditure while reducing lower joint extremity is to have obese people walk at a slow speed with an incline. Researchers found that by walking at either 0.5 or 0.75 m/s and a 9° or 6° incline respectively would equate to the same net metabolic rate as an obese individual walking at 1.50 m/s with no incline. [25] These slower speeds with an incline also had significantly reduced loading rates and reduced lower-extremity net muscle moments. [25] Other strategies to consider are slow walking for extended periods of time and training underwater to reduce loads on joints and increase lean body mass. [26]
It is often very difficult to recruit obese people that do not have other comorbidities such as osteoarthritis or cardiovascular disease. It is also difficult to deduce if a healthy population is representative of the entire obese population because the people that volunteer may already be somewhat active and have a greater fitness than their sedentary counterparts. Another difficulty lies in the ability to characterize biomechanical variables due to the large variability between research groups placement of biomechanical markers. Marker placement often used for lean individuals can be difficult to find on obese individuals due to the excess of adipose between the bone landmark and the marker. The uses of DEXA and X-rays have improved the placement of these biomechanical markers, but variability still remains and should be taken into account when analyzing scientific findings.
Running is a method of terrestrial locomotion by which humans and other animals move rapidly on foot. Running is a gait with an aerial phase in which all feet are above the ground. This is in contrast to walking, where one foot is always in contact with the ground, the legs are kept mostly straight, and the center of gravity vaults over the stance leg or legs in an inverted pendulum fashion. A feature of a running body from the viewpoint of spring-mass mechanics is that changes in kinetic and potential energy within a stride co-occur, with energy storage accomplished by springy tendons and passive muscle elasticity. The term "running" can refer to a variety of speeds ranging from jogging to sprinting.
Walking is one of the main gaits of terrestrial locomotion among legged animals. Walking is typically slower than running and other gaits. Walking is defined by an "inverted pendulum" gait in which the body vaults over the stiff limb or limbs with each step. This applies regardless of the usable number of limbs—even arthropods, with six, eight, or more limbs, walk. In humans, walking has health benefits including improved mental health and reduced risk of cardiovascular disease and death.
Leptin, also known as obese protein, is a protein hormone predominantly made by adipocytes. Its primary role is likely to regulate long-term energy balance.
Adipose tissue is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular endothelial cells and a variety of immune cells such as adipose tissue macrophages. Its main role is to store energy in the form of lipids, although it also cushions and insulates the body.
A gait is a manner of limb movements made during locomotion. Human gaits are the various ways in which humans can move, either naturally or as a result of specialized training. Human gait is defined as bipedal forward propulsion of the center of gravity of the human body, in which there are sinuous movements of different segments of the body with little energy spent. Various gaits are characterized by differences in limb movement patterns, overall velocity, forces, kinetic and potential energy cycles, and changes in contact with the ground.
Weight gain is an increase in body weight. This can involve an increase in muscle mass, fat deposits, excess fluids such as water or other factors. Weight gain can be a symptom of a serious medical condition.
Bariatrics is a discipline that deals with the causes, prevention, and treatment of obesity, encompassing both obesity medicine and bariatric surgery.
Running economy (RE) a complex, multifactorial concept that represents the sum of metabolic, cardiorespiratory, biomechanical and neuromuscular efficiency during running. Oxygen consumption (VO2) is the most commonly used method for measuring running economy, as the exchange of gases in the body, specifically oxygen and carbon dioxide, closely reflects energy metabolism. Those who are able to consume less oxygen while running at a given velocity are said to have a better running economy. However, straightforward oxygen usage does not account for whether the body is metabolising lipids or carbohydrates, which produce different amounts of energy per unit of oxygen; as such, accurate measurements of running economy must use O2 and CO2 data to estimate the calorific content of the substrate that the oxygen is being used to respire.
Adipose tissue is an endocrine organ that secretes numerous protein hormones, including leptin, adiponectin, and resistin. These hormones generally influence energy metabolism, which is of great interest to the understanding and treatment of type 2 diabetes and obesity.
Being overweight is having more body fat than is optimally healthy. Being overweight is especially common where food supplies are plentiful and lifestyles are sedentary.
Sarcopenic obesity is a combination of two disease states, sarcopenia and obesity. Sarcopenia is the muscle mass/strength/physical function loss associated with increased age, and obesity is based off a weight to height ratio or body mass index (BMI) that is characterized by high body fat or being overweight.
Running energetics is the study of the energy cost of running. It is clear in the vast majority of species that as running speed increases the energetic cost of running increases. It also has long been known that between and within species variability exists in the energy cost of running a given speed. This variability has led to the study of biomechanical or physiological factors that may be predictive of the energy cost to run both between and within species.
The preferred walking speed is the speed at which humans or animals choose to walk. Many people tend to walk at about 1.42 metres per second. Individuals may find slower or faster speeds uncomfortable.
Human locomotion is considered to take two primary forms: walking and running. In contrast, many quadrupeds have three distinct forms of locomotion: walk, trot, and gallop. Walking is a form of locomotion defined by a double support phase when both feet are on the ground at the same time. Running is a form of locomotion that does not have this double support phase.
Terrestrial locomotion by means of a running gait can be accomplished on level surfaces. However, in most outdoor environments an individual will experience terrain undulations requiring uphill running. Similar conditions can be mimicked in a controlled environment on a treadmill also. Additionally, running on inclines is used by runners, both distance and sprinter, to improve cardiovascular conditioning and lower limb strength.
Neuromechanics of orthoses refers to how the human body interacts with orthoses. Millions of people in the U.S. suffer from stroke, multiple sclerosis, postpolio, spinal cord injuries, or various other ailments that benefit from the use of orthoses. Insofar as active orthoses and powered exoskeletons are concerned, the technology to build these devices is improving rapidly, but little research has been done on the human side of these human-machine interfaces.
The effect of gait parameters on energetic cost is a relationship that describes how changes in step length, cadence, step width, and step variability influence the mechanical work and metabolic cost involved in gait. The source of this relationship stems from the deviation of these gait parameters from metabolically optimal values, with the deviations due to environmental, pathological, and other factors.
Normal weight obesity is the condition of having normal body weight, but with a high body fat percentage, leading to some of the same health risks as obesity.
Gait deviations are nominally referred to as any variation of standard human gait, typically manifesting as a coping mechanism in response to an anatomical impairment. Lower-limb amputees are unable to maintain the characteristic walking patterns of an able-bodied individual due to the removal of some portion of the impaired leg. Without the anatomical structure and neuromechanical control of the removed leg segment, amputees must use alternative compensatory strategies to walk efficiently. Prosthetic limbs provide support to the user and more advanced models attempt to mimic the function of the missing anatomy, including biomechanically controlled ankle and knee joints. However, amputees still display quantifiable differences in many measures of ambulation when compared to able-bodied individuals. Several common observations are whole-body movements, slower and wider steps, shorter strides, and increased sway.
Energy expenditure, often estimated as the total daily energy expenditure (TDEE), is the amount of energy burned by the human body.
{{cite journal}}
: CS1 maint: multiple names: authors list (link)