# Effects of Obesity on Adaptation Transfer from Treadmill to Over-Ground Walking
## 4 Discussion
Considering that individuals with obesity have impaired postural control and stability [25], increasing double-limb support time, along with increasing step width and decreasing walking speed, could be a primary strategy to maximize postural stability, and to avoid asymmetric gait and falling after split-belt treadmill walking. Furthermore, it is reasonable to suppose that step length could be balanced by contributions from increased double-limb support time. When exposed to split-belt perturbation, the treadmill powers the legs, so more control is required for regulating the period of double-limb support (i.e., when both limbs are on the ground). This may have led to longer double-limb support times in adults with obesity compared with adults with normal weight. Researchers have studied how human actions adapted to a specific environment are transferred to other environments and demonstrated that similarity of the movements can influence the transfer of action [26; 27]. The transfer of adapted patterns is greatest when walking in a familiar environment [28; 29; 30]. The amount of transfer could be similar for adults with obesity and with normal weight if both groups have experience with treadmill walking. We suspect that the transfer of the adapted gait pattern observed in adults with obesity could be similar to that observed in normal weight adults, considering the fact that treadmills have been widely used for exercise. However, the altered temporal gait parameters (i.e., increased double-limb support times) observed in the obese population might reduce the ability to switch temporal patterns with the change in gait environment from the treadmill to over-ground walking (i.e., less transfer of aftereffects for the temporal gait parameter). Previous studies on rehabilitative gait training have demonstrated that, although a little different, there are similarities observed between treadmill and over-ground walking in young adults [31; 32; 33]. An ideal rehabilitation intervention could include both treadmill and over-ground walking to maximize improvements in walking through task-specific training. In the current study, participants reduced step asymmetry in both treadmill and over-ground walking and transferred aftereffects for step symmetry from the treadmill to over-ground walking. Therefore, it could be beneficial for future studies to examine the use of split-belt treadmill walking paired with over-ground walking in interventions with those with obesity. One drawback of this approach, of course, would be the cost incurred by using a rehabilitation paradigm that necessitates the use of split-belt treadmill technology. However, future findings may reveal whether there are rehabilitative benefits that outweigh the cost of the equipment. We acknowledge that the present study has limitations. Firstly, we intentionally recruited participants without comorbidities, such as osteoarthritis, plantar fascitits, or cardiovascular disease. Thus, the generalizability of our study is limited by the fact that our participants may not be representative of those with obesity and additional conditions. However, this reduced confounding variables that could have influenced the interpretation of our results. Secondly, the number of male participants with obesity that we tested was smaller than the number of females, which may reduce the ability to generalize the results to males. Third, we did not have the participants rate their perceived exertion during the walking task. Future studies should examine how perceived exertion affects walking adaptation in adults with obesity. Despite these limitations, our results provide important information about the effect of obesity on walking adaptation and transfer from treadmill to over-ground walking.