INTRODUCTION

In late-stage Parkinson’s disease (PD), progressive motor and nonmotor symptoms lead to reduced walking ability, and many individuals ultimately require wheelchairs, particularly at Hoehn and Yahr (HY) stage V [1,2]. Manual wheelchair (MW) propulsion is impaired in PD, even during straight-line driving [3]. Although recent case series have suggested that cycling wheelchairs (CWs) may enable faster propulsion than MWs do [4], evidence remains limited to a small number of patients with freezing of gait (FOG).

For daily wheelchair mobility, endurance and efficiency are critical, especially during continuous driving with repeated directional changes. Preserved cycling ability in patients with advanced PD suggests that CW use may enhance these aspects; however, they have not been systematically examined in this population. The 6-minute push test (6MPT) is widely used to assess wheelchair endurance via total driving distance [5,6], and when combined with heart rate (HR) measurements, the Physiological Cost Index (PCI) provides an index of driving efficiency [7].

In this preliminary study, using the 6MPT and PCI, the endurance and efficiency of continuous CW were compared with those of MW driving, including turning, in individuals with late-stage PD.

MATERIALS & METHODS

Participants

This cross-sectional pilot study was conducted at a rehabilitation hospital in Japan between February and March 2025. The inclusion criteria were as follows: 1) idiopathic PD diagnosed using the International Parkinson and Movement Disorder Society clinical diagnostic criteria [8], 2) late-stage PD, defined as a disease duration ≥7 years and either HY stage 4 or 5 in the ON state or a Schwab and England score ≤50% [9,10], 3) understanding of MW and CW operation, 4) ability to drive an MW, 5) ability to pedal without assistance, and 6) no changes in antiparkinsonian medication during the measurement period. The exclusion criteria were neuromuscular, orthopedic, or vestibular disorders that could interfere with pedaling; highly unpredictable ON–OFF motor fluctuations; cardiac disease (including pacemaker implantation); and respiratory disease limiting exercise performance.

A total of 9 participants were included in the analysis (Table 1 and Supplementary Table 1). On the basis of previous definitions [11], all participants were categorized as “freezers,” defined as scoring ≥1 on Item 3.11 (FOG) of the Movement Disorder Society– Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) Part III [12], which can be applied even in individuals with severe gait impairment and was administered by a certified researcher (M.K.). Written informed consent was obtained. The study was approved by the ethics committees of Tsurumaki-Onsen Hospital (no. 600).

Procedures

Testing was performed on a flat outdoor asphalt course under stable conditions. All participants began each trial by turning toward the less affected side (Figure 1A). None had prior CW experience. The employed CW (PR000001HF, TESS) uses pedaling for propulsion and joystick-based directional control and operates with each participant’s dominant hand; all participants were right-handed. Before testing, participants completed brief familiarization trials with both the MW and the CW to ensure operational proficiency (Figure 1B).

The 6MPT was used to assess wheelchair endurance and efficiency. For the MW condition, participants used their own wheelchairs. MW and CW trials were performed in randomized order on separate days, at least one day apart and within eight days. In accordance with standard 6MPT procedures, total driving distance was used as an index of endurance, and rest was allowed as needed. All assessments were conducted in the ON medication state at the same time of day.

HR and fatigue measurements

HR was measured manually immediately before and after each test by palpating the radial pulse and recorded in beats per minute. The participants sat for three minutes before each trial to obtain the resting HR. The difference between the post-driving and resting HR (ΔHR) was also calculated. This method has demonstrated acceptable agreement with electrocardiographic HR measurement [13]. Fatigue was assessed with the modified Borg scale (0–10; 0=no fatigue, 10=maximal) for four components: whole-body fatigue, upper-limb fatigue, lower-limb fatigue, and dyspnea [14]. Participants rated their fatigue at the end of each test following standardized instructions. All HR and fatigue assessments were performed by the same trained examiner.

Physiological Cost Index

The PCI, a simple measure of locomotor efficiency, was calculated from manually measured HR and driving speed using the following formula: PCI = (post-driving HR – resting HR)/speed [15]. Driving speed was calculated as the total distance divided by the total elapsed time of each trial. When a participant stopped propulsion because of fatigue, the PCI was calculated using the HR and distance at the point of stopping. To support the accuracy of manual HR measurement, a subset of participants wore a validated wearable HR monitor (Apple Watch SE2) [16,17], which showed acceptable agreement with manual PCI estimates (Supplementary Table 2).

Statistical analysis

The Wilcoxon signed-rank test was used to compare the driving distance, speed (total distance divided by 6 minutes), ΔHR (post-driving HR – resting HR), and PCI between the MW and CW conditions. Effect sizes were calculated as Cohen’s r. In addition, correlations between the percent change in driving distance and clinical assessments were examined using Spearman’s rank correlation coefficients. All analyses were performed using SPSS Statistics (ver. 30.0; IBM Corp.), with the significance level set at α=0.05. Additional subgroup analyses were conducted for participants at HY stage V (n=6).

RESULTS

One participant (Case 7; Supplementary Table 1) discontinued the MW trial at 4 minutes because of progressive fatigue and did not resume propulsion thereafter. All other participants completed the MW trial without interruption. In contrast, all participants completed the 6MPT using the CW without any rest breaks or interruptions. A supplementary video illustrates differences in propulsion patterns between MWs and CWs (Supplementary Video 1).

The total distance and speed associated with the CW were significantly greater than those associated with the MW (distance: 306.0 m [interquartile range (IQR): 201.0–476.0] vs. 62.0 m [IQR: 30.0–130.0]; speed: 51.0 m/min [IQR: 33.5–79.3] vs. 10.3 m/min [IQR: 6.3–21.7]; both p<0.05, r=0.89) (Figure 1C). No significant differences between conditions were found in the ΔHR (p=0.317) (Figure 1D). The PCI was significantly lower with the CW than with the MW (0.25 beats/m [IQR: 0.13– 0.36] vs. 0.63 beats/m [IQR: 0.39–2.40]; p<0.05, r=-0.89) (Figure 1E). No significant between-condition differences were found in the modified Borg scale ratings for whole-body fatigue (p=0.777), upper-limb fatigue (p=0.154), lower-limb fatigue (p=0.326), or dyspnea (p=0.497) (Supplementary Table 1). No significant associations were observed between the differences in CW–MW distance and clinical measures (Supplementary Table 3). In the HY stage V subgroup (n=6), CW propulsion resulted in greater distance and speed and a lower PCI than did MW, while the ΔHR remained nonsignificant (Supplementary Figure 1).

DISCUSSION

This preliminary study demonstrated that individuals with late-stage PD, including those at HY stage V, could drive longer distances with lower PCI values during the 6MPT when the CW was used. These findings suggest that the CW may support more enduring and efficient wheelchair mobility during continuous driving tasks.

Several mechanisms may underlie the longer distances achieved with the CW. Rhythmic pedaling is often preserved in PD, even in individuals with FOG [18], supporting continuous propulsion. In contrast, MW propulsion involves intermittent push–recovery cycles and complex bimanual coordination, particularly during turning, which may limit forward progression. Pedaling enables continuous bilateral force generation, while joystick steering reduces coordination demands and promotes smoother propulsion.

Despite the markedly longer distances and lower PCI values achieved with the CW, neither HR change nor subjective fatigue differed between conditions. These findings suggest that the CW enables more enduring and efficient wheelchair mobility in patients with late-stage PD without additional cardiovascular strain or perceived exertion.

The absence of additional cardiovascular strain with CW propulsion likely reflects the intrinsic advantages of pedaling over upper-limb driving. Lower-limb muscles generate higher mechanical output with less cardiac demand [19], and pedaling provides a continuous rhythmic force that relies on automatic motor patterns that are often preserved in patients with advanced PD [20]. In contrast, MW propulsion requires intermittent push–recovery cycles and complex bimanual coordination, which may increase the autonomic load.

This study has several limitations. First, the small sample size increased the uncertainty in effect estimation. Second, all participants had FOG, which may limit generalizability to late-stage PD without FOG; however, given the high prevalence of FOG in patients with advanced PD [20], the cohort likely reflects a typical clinical profile. Although wheelchair performance may differ by clinical phenotype or symptom severity, no clear association was observed between CW benefit and clinical profile, and these exploratory findings should be interpreted cautiously. In addition, HR was assessed using pre- and post-test measurements rather than continuous monitoring. Although supplementary analyses using a wrist-mounted wearable device supported the validity of the PCI, upper-limb movement during MW propulsion may have influenced these measurements. Future studies using electrocardiogram-based continuous HR monitoring or alternative physiological biomarkers are warranted.

In conclusion, this preliminary study suggests that a CW may provide a more enduring and efficient means of mobility than an MW for individuals with late-stage PD, including those at HY stage V. These findings underscore the potential practical value of CW use in advanced PD, where mobility options are severely limited. Further studies with larger cohorts and real-world evaluations are needed to validate these observations.

Supplementary Materials

Video 1.

Description of driving patterns in MW and CW. Segment 1: Case 1 (Hoehn and Yahr stage IV). MW driving was feasible, but CW driving enabled smoother and faster propulsion, including during turning maneuvers. Segment 2: Case 6 (Hoehn and Yahr stage V). MW driving showed progressively smaller, fragmented upper-limb pushes with brief bursts of speed. In contrast, CW driving remained steady and continuous throughout, including during turns.

Notes

Ethics Statement

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1975 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all the patients included in the study.

Conflicts of Interest

The authors have no financial conflicts of interest.

Funding Statement

None

Acknowledgments

We sincerely thank all participants for their involvement in this study and the clinical staff for their valuable support throughout the research.

Author Contributions

Conceptualization: Mayura Konzo, Yohei Okada. Data curation: Mayura Konzo, Masaki Naito, Ayumi Ide. Formal analysis: Mayura Konzo, Yohei Okada. Funding acquisition: Yohei Okada. Investigation: Mayura Konzo. Methodology: Mayura Konzo, Yohei Okada. Project administration: Yohei Okada. Software: Mayura Konzo. Supervision: Yohei Okada, Tomohiro Shibata. Validation: Masaru Narita, Taiyo Kai, Dai Wakabayashi, Wataru Fujita. Visualization: Mayura Konzo. Writing—original draft: Mayura Konzo, Yohei Okada. Writing—review & editing: all authors.

Figure 1.

Manual versus cycling wheelchair performance during the 6-minute push test (6MPT). A: Layout of the outdoor turning course. B: The manual wheelchair (MW) and cycling wheelchair (CW) used in the study. C: Total distance traveled during the 6MPT for MW and CW. D: Change in heart rate (ΔHR = post-driving HR – resting HR) for each condition. E: Physiological Cost Index (PCI) values for MW and CW.

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