# EXPERT SPLIT BELT WALKERS? GAIT BIOMECHANICS AND ENERGETICS IN TWO INDIVIDUALS OVER TEN DAYS OF ADAPTATION

Samantha N Jeffcoat, Andrian Kuch, Russell T Johnson, Natalia Sanchez

► To cite this version:

Samantha N Jeffcoat, Andrian Kuch, Russell T Johnson, Natalia Sanchez. EXPERT SPLIT BELT WALKERS? GAIT BIOMECHANICS AND ENERGETICS IN TWO INDIVIDUALS OVER TEN DAYS OF ADAPTATION. American Society of Biomechanics, ASB, Aug 2024, Madison (US-WI), United States. hal-05130131

HAL Id: hal-05130131

https://hal.science/hal-05130131v1

Submitted on 25 Jun 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
Samantha N. Jeffcoat¹*, Andrian Kuch¹, Russell T. Johnson², Natalia Sanchez¹

¹Department of Physical Therapy, Crean College of Health and Behavioral Sciences, Chapman University

²Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University

*Corresponding author's email: jeffcoat@chapman.edu

**Introduction:** People continuously adapt their walking behavior in a changing environment. In the lab, gait adaptation can be induced with a split-belt treadmill [1], where the belt under each leg moves at a different speed, leading to an asymmetric walking pattern. Over time, the neuromotor system adapts to this novel environment by transitioning from a negative to a more positive step length asymmetry [1,2]. This adaptation occurs in parallel with a reduction in energetic cost [2,3] and in positive work by the legs [2,4], indicating that people learn to use external assistance to improve economy [2,4]. Research has shown that adaptation of walking patterns can be retained from one day to the next, allowing faster relearning with retraining [5]. What remains to be determined is, given the novelty of the split-belt treadmill, if individuals continuously adapt their gait over multiple sessions to reduce energetic cost. We hypothesized: 1) participants will adapt walking patterns during 10 sessions, exemplified by a stable, positive step length asymmetry by day 10, 2) participants will continue to adapt metabolic cost during the 10 sessions, with ongoing reductions in metabolic cost and work done by the legs after 10 sessions [6], 3) gait patterns and energetic cost adapted over the 10 days will be retained in a follow-up session one month after the 10th session.

**Methods:** We tested two participants in a 10-day split-belt training protocol over the course of 3 weeks, and again at one month follow-up. **P1:** age 30, male, 1.7 m, 72 kg, exercise: cardio 4 hours a week. **P2:** age 30, female, 1.52 m, 50 kg, exercise: 2 hours a week low intensity. Participants walked on a split-belt for 10 minutes with the left belt at 1.5 m/s and the right belt at 0.5 m/s. We measured net metabolic power, step length asymmetry (SLA), and positive work by the fast leg (W+). We obtained average values of metabolic power, SLA, and W+ during early (EA) and late adaptation (LA), which were roughly the first and last 30 seconds of split-belt walking. We calculated correlations between outcome variables and session number.

**Results & Discussion:** We observed distinct participant responses (Fig. 1). **P1:** Metabolic power did not decrease with repeated exposure during EA (r = -0.23, p = 0.517) or LA (r = -0.62, p = 0.095). SLA was positively associated with session number during EA (r = 0.79, p < 0.005) such that the participant had a less negative SLA with each session. SLA did not change consistently over the 10 sessions during LA (r = -0.35, p = 0.317). SLA was sustained in the one-month follow-up during EA (day 10 = -0.07, day 11 = -0.06). W+ was significantly associated with session number during EA (r = -0.77, p = .009) but not LA (r = -0.60, p = 0.069). **P2:** Metabolic power did not decrease with repeated exposure during EA (r = -0.10, p = 0.780) or LA (r = 0.16, p = 0.527). SLA was not associated with session number during EA (r = 0.59, p = 0.072) or LA (r = -0.14, p = 0.696). SLA was sustained in the one-month follow-up during EA (day 10 = -0.093, day 11 = -0.098). W+ was not associated with session number during EA (r = -0.57, p = 0.084) or LA (r = 0.08, p = 0.830).

We observed distinct responses in repeated split-belt treadmill adaptation. In agreement with our hypotheses, P1 retained changes in SLA and W+ during EA and adapted toward positive asymmetries during LA with repeated exposure. However, P1 did not continuously reduce W+ or metabolic power between sessions during LA. P2 only reduced EA SLA from day 1 to day 2 and plateaued after day 2. P2 also did not consistently adapt metabolic power or W+ during EA or LA across days. Both participants retained EA SLA at follow-up but Metabolic Power and W+ were not retained. Our findings contrast those observed over a long 45-minute bout of adaptation where individuals continuously adapted SLA toward positive values while reducing W+ and metabolic power [2]. Our results suggest that short bouts of repeated adaptation do not lead individuals to maximize external assistance from the environment.

**Significance:** External assistance is used in clinical settings to retrain walking patterns in individuals with gait impairment. Our findings indicate that adaptation during short bouts of multi-day training cannot be equated to long bouts in a single session [2]. We also show that there is variability between individual responses to split-belt adaptation, which points at the need to tailored training for each individual.

<figure><img src="image_2.png" /><figcaption>**Figure 1:** P1 and P2 timeseries for metabolic power (Pnorm) and SLA across sessions and correlation with session number during early and late adaptation.</figcaption></figure>

**Acknowledgments:** Funding: NIH NCMRR R03HD107630 and NIH NCATS R03TR004248 to N. Sanchez.

**References:** [1] Reisman DS et al. (2005) *J Neurophysiol* 94(4); [2] Sánchez N et al. (2021) *Journal of Neurophysiology* 125(2); [3] Finley JM et al. (2013) *J Physiol* 591(4); [4] Sánchez N et al. (2019) *J Physiol* 597(15); [5] Leech KA et al. (2018) *Journal of Neurophysiology* 120(4); [6] Poggensee KL et al. (2021) *Sci. Robot* 6(58)