# Effects of Obesity on Adaptation Transfer from Treadmill to Over-Ground Walking
###### Abstract  
Discerning whether individuals with obesity transfer walking adaptation from treadmill to over-ground walking is critical to advancing our understanding of walking adaptation and its usefulness in rehabilitating obese populations. We examined whether the aftereffects following split-belt treadmill adaptation transferred to over-ground walking in adults with normal-weight body mass index (BMI) and obese BMI. Nineteen young adults with obesity and 19 age-matched adults with normal weight walked on flat ground at their preferred speed before and after walking on a treadmill with tied belts (preferred speed) and with the split-belt at their preferred speed and at a speed 50% slower than their preferred speed. The adaptation and aftereffects in step length and double-limb support time symmetry were calculated. We found that the amount of temporal adaptation was similar for adults with obesity and with normal weight (\(p>0.05\)). However, adults with obesity showed greater asymmetry for double-limb support time following split-belt treadmill walking compared to adults with normal weight (\(p<0.05\)). Furthermore, the transfer of asymmetry for double-limb support time from the treadmill to over-ground walking was less in adults with obesity than in adults with normal weight (\(p<0.05\)). The transfer of adapted gait following split-belt treadmill walking provides insight into how atypical walking patterns in individuals with obesity could be remediated using long-term gait training. obesity; gait; adaptation; rehabilitation +
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clearance to cross low versus high obstacles [14]. Additionally, adults with obesity have difficulty matching steps to an audio metronome beat while walking; they step later than the metronome beat regardless of the BPM (beats per minute) [12]. Adults with obesity also walk slower after a slow metronome pace and faster after a fast metronome pace, thus demonstrating aftereffects. Taken together, the evidence shows that these challenges with adaptation may make it difficult to safely complete walking and activities of daily living, such as walking to the grocery store and crossing the street in accordance with traffic signals. This raises a question; how do individuals with obesity change the ways in which they walk when posed with a disruption in their typical patterns of walking? A split-belt treadmill training paradigm has been used to examine walking adaptation. In a split-belt treadmill paradigm, two separate belts moving beneath each leg can be independently controlled [15; 16]. This paradigm allows for repeated practice of walking in which each leg moves at a different speed. Previous research on split-belt treadmill walking adaptation in healthy adults has demonstrated that step length and double-limb support time are asymmetric during an initial adaptation period when the belt speed is changed so that one belt moves faster than the other [16]. Consequently, the limb on the slow belt takes a longer step than the limb walking on the fast belt. Over time, walkers gradually adapt to re-establish step symmetry during split-belt walking. After only 10-15 min of split-belt treadmill walking, walkers exhibit aftereffects [16; 17]. These findings have led to the suggestion that the adaptive strategies observed during split-belt treadmill walking may have the potential to be used as a rehabilitative technique for individuals post-stroke [18; 16], with Parkinson's disease [19], and who have had amputations [20]. However, whether the same would be true for adults with obesity is unknown. Using split-belt treadmill training as a rehabilitative tool might spur faster adaptation to future perturbations experienced in everyday life and facilitate increased physical activity; short-term changes in walking could be capitalized upon with repeated practice to produce long-term changes in walking [21].