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Biomechanics of running in overweight/obese children

by P. Debraux | 19 October 2021

biomechanics, running, obesity, overweight, children, health, problem, joint, kinetics, kinematics, force, moments, stress

The prevalence of overweight and obesity among children and adolescents has become a real public health problem in 40 years, rising from 4% in 1975 to 18% in 2016. As a result, more than 340 million children and adolescents (5-19 years) are now overweight or obese. The health risks associated with childhood obesity include cardiovascular disease, metabolic syndrome, depression and social isolation. In addition to the negative physiological and psychological effects, excessive body mass in children is linked to movement disfunction, excessive joint stress and the development of osteoarthritis and other joint pathologies (note that osteoarthritis is also linked to obesity through chronic inflammation).

Many studies have investigated the impact of overweight and obesity on gait biomechanics by comparing the movement of children with normal body mass with that of overweight and obese children. Differences in kinematics, ground reaction forces or joint stresses were revealed. However, few studies have looked at biomechanical differences in higher impact activities such as running. Rightly or wrongly, running is one of the most recommended forms of exercise for reducing obesity and improving general health. It is therefore important to examine the kinematics and kinetics of running in overweight and obese children in order to identify the risks that this activity may have for this public.

The Study

In order to find out more, American researchers compared the kinematics and kinetics of running in children with a healthy body mass and children who were overweight or obese. Forty-two children aged between 8 and 12 years took part in the study (16 of them were overweight or obese). The protocol consisted of running at an imposed speed of 3.5 m/s (i.e. 12.6 km/h) on a straight line of 15 metres. To analyse the kinematics of the movement, 3D cameras (Qualysis) were placed along the running track and to analyse the kinetics, a force platform (AMTI) was embedded in the track. Each child performed between 3 and 5 trials.

The kinematic variables studied included joint angles in the frontal and sagittal planes and excursions (i.e., range of motion) of the hip, knee and ankle. The kinetic variables studied included vertical impact peak, average vertical loading rate, instantaneous vertical loading rate, vertical force peak, braking force peak and propulsive force peak.

Results & Analyzes

The main results of this study show that significant differences exist in running biomechanics between the two groups of children. First of all, overweight/obese children have shorter step length and spend more time in the stance phase compared to children with normal body mass. One explanation for this is that the shorter stride would avoid the high metabolic cost of moving excess body mass. But the difference could also be explained by a decrease in range of motion and poor balance control. The researchers observed lower ranges of motion in the overweight/obese children, with an even greater difference at the hip and knee. And regarding balance, previous studies have shown that overweight/obese children have greater postural instability than those with normal body mass. This may be due to greater difficulty in controlling the fall of their centre of gravity during movement. Thus, shorter strides and a longer stance time could help them to better control the fall of their centre of gravity with each step, thus helping them to maintain their balance while moving.

In the sagittal plane, overweight/obese children show smaller ranges of motion at the knee and hip than children with normal body mass. These differences are especially noticeable at the beginning of the stance phase. This indicates a more rigid gait that involves greater vertical stresses on the body. This lack of flexion could be due to a lack of mobility related to the accumulation of fatty tissue, and would result in a lack of shock absorption in activities such as running.

In the frontal plane, overweight/obese children have greater ankle inversion at foot placement followed by greater eversion. Excessive eversion is linked to various running-related injuries, including tibial stress fractures, patellofemoral syndrome and Achilles tendonopathy. At the knee level, greater abduction is observed throughout the stance phase in overweight/obese children. Increased knee abduction during dynamic movements is one of the mechanisms of non-contact ACL injuries and is associated with greater mechanical stress on the ACL. In addition, a greater knee abduction angle during running increases contact forces on the lateral patellofemoral joint.

At the kinetic level, overweight/obese children show significantly higher ground impact forces and joint force moments. This is probably a consequence of the more rigid (less damped) stride. When the forces are expressed relative to body mass, no difference appears between the two groups of children. However, it should be remembered that joint surfaces and plantar areas are not proportional to the increase in body mass. Furthermore, studies have shown that bone mineral density is reduced in overweight children...

Practical Applications

The results of this study highlight the detrimental impact that excess body mass has on the biomechanics of running in children. The greater ground reaction forces and joint moments can lead to greater joint stresses, misalignments and ultimately joint problems.

One of the main limitations of this study is the standardisation of running speed for all children. It is likely that overweight/obese children would naturally choose a slower running speed which would limit the problems observed.

While a recent research advise to increase fitness levels as a priority rather than lose weight, it seems important to prescribe appropriate physical activity to avoid the risk of injury associated with over-stressing or misalignement. The progression from low to high impact activities must be appropriate and respected to allow time for the musculo-tendinous, ligamentous and bony structures to adapt. As the researchers note, it is important to create a positive association with physical activity and sport from an early age in order to create lifelong habits.


  1. Bowser BJ and Roles K. Effects of Overweight and Obesity on Running Mechanics in Children. Med Sci Sports Exerc, 53 (10), 2101-2110, 2021.

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