Fractal fluctuations in spatiotemporal variables when walking on a self-paced treadmill

Area of Science:

• Biomechanics
• Human movement analysis
• Complex systems

Background:

• Gait analysis often uses fixed-speed treadmills (FTM), which may alter natural walking dynamics.
• Self-paced treadmills (STM) adjust belt speed to the user's walking pace, potentially offering a more ecologically valid simulation.
• Understanding fractal dynamics of gait parameters is crucial for assessing motor control and identifying pathological changes.

Purpose of the Study:

• To compare the fractal dynamic properties of stride time (ST), stride length (SL), and stride speed (SS) between STM and FTM.
• To investigate the influence of metronomes on gait variability and fractal dynamics under both treadmill conditions.
• To determine which treadmill type more closely replicates overground walking fractal dynamics.

Main Methods:

• Twelve healthy young adults walked under four conditions: STM, STM with metronome (STM+met), FTM, and FTM with metronome (FTM+met).
• Analysis included mean, variability, and fractal dynamics of ST, SL, and SS.
• Cross-correlated surrogate data were used to examine relationships among variables.

Main Results:

• Mean values for ST, SL, and SS were similar across conditions.
• Variability was generally higher on STM compared to FTM.
• Metronomes reduced ST and SS variability.
• STM maintained the fractal dynamics of SS, unlike FTM.
• Fractal dynamics of ST were lost with metronome use.
• STM walking exhibited fractal dynamic properties closer to overground walking than FTM.

Conclusions:

• Self-paced treadmills provide a more realistic simulation of overground walking fractal dynamics compared to fixed-speed treadmills.
• Gait variability and fractal dynamics are influenced by treadmill type and metronome use.
• Findings support the use of STM for research on gait fractal dynamics and in rehabilitation settings.