# Capacity vs. Performance in Cerebral Palsy: A Preliminary Motion Analysis

Julie Rozaire, Alexandre Naaïm, Mickael Begon, Sonia Duprey, Emmanuelle

Chaleat-Valayer, Yosra Cherni

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## To cite this version:

Julie Rozaire, Alexandre Naaïm, Mickael Begon, Sonia Duprey, Emmanuelle Chaleat-Valayer, et al. Capacity vs. Performance in Cerebral Palsy: A Preliminary Motion Analysis. Multidisciplinary Biomechanics Journal, 2025, 50th congress of the.., 10.46298/mbj.16251. hal-05191806v2

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Submitted on 23 Oct 2025

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# Capacity vs. Performance in Cerebral Palsy:
A Preliminary Motion Analysis

Julie Rozaire<sup>a, b*</sup>, Alexandre Naaïm<sup>b</sup>, Mickael Begon<sup>c, d</sup>,
Sonia Duprey<sup>b</sup>, Emmanuelle Chaleat-Valayer<sup>a</sup>,
Yosra Cherni<sup>c, d</sup>

a Centre Médico-Chirurgical de Réadaptation des Masses Croix-Rouge française,
Lyon, France

b Univ Lyon, Univ Gustave Eiffel, Univ Claude Bernard Lyon 1, LBMC UMR_T9406,
Lyon, France

c S2M lab, Université de Montréal, Montréal (Qc), Canada

d Centre de recherche Azrieli du CHU Sainte-Justine, Montréal (Qc), Canada

* Corresponding author: julie.rozaire@croix-rouge.fr

Received date: 06/04/2025

Accepted date: 27/06/2025

Publication date: 27/10/2025

**Keywords:** cerebral palsy, upper limbs, motion analysis, performance

© 2025 The Authors

Licence CC-BY 4.0

Published by Société de Biomécanique

## 1. Introduction

Understanding the relationship between an individual's capacity (the ability in a standardized environment) and their performance (the actual behavior in their usual environment) is essential to understand the extent of one's ability and their effective use in daily life (OMS, 2001). The discrepancy between these constructs informs clinicians about potential underutilization of capacity or underlying limitations. While clinical assessments like the AHA (Krumlinde-Sundholm et al., 2007) evaluate performance, motion analysis studies can quantify spontaneous upper limb use. However, these latter are rarely used in little constrained settings (Rozaire et al., 2024). Furthermore, the inherent variability in unconstrained tasks warrants investigation. This study, based on motion analysis, aims to examine the difference between capacity and performance in individuals with cerebral palsy (CP), and characterize the inter-individual variability in performance tasks among typically developing (TD) participants.

## 2. Methods

### 2.1 Population

Five TD children (7±3 years) and five children with unilateral CP (5±2 years) were recruited within the CRME after endorsement by the ethical committee (n2025-7775). Children with CP had mild to moderate impairment (MACS level II-III).

### 2.2 Tasks

All children completed a series of capacity tasks (Shoulder Abduction and Flexion, Elbow Pronation-Supination and Flexion-Extension) and another set of bimanual performance tasks inspired by the AHA (Putting on a hat, Reaching and manipulating toys, Opening a bottle and pouring, Playing cymbals).

## 2.3 Measurement

Data were collected using 10 optoelectronic cameras Prime 13 from Optitrack (NaturalPoint, Inc., Corvallis, United States), sampled at 120 Hz. Reflective markers were placed on anatomical marker following ISB recommendation. The glenohumeral joint center was estimated using the regression method of Rab et al. (Rab et al., 2002).

## 2.4 Data Processing

Minimum and maximum elbow and shoulder angles of the non-dominant limb were calculated following ISB recommendation (Wu et al., 2005). However, in order to be clinically relevant, the pronosupination 0° position was defined as the forearm in mid-pronation/supination (Figure 1A). Group differences were compared using Wilcoxon rank-sum tests (p < 0.05). TD children variability was quantified as the range of values measured across participants.
### 3. Results and discussion

In capacity tasks, children with CP exhibited significant differences in elbow angles compared to the TD group (Table 1). Subsequent results will focus specifically on elbow supination since this movement is critical for object orientation. Here it showed both largest difference in mean values and the highest variability within the CP group.

<table><caption>**Table 1.** Maxima of angles in capacity for CP and TD children.</caption><thead><tr><th rowspan="2">Angle (°)</th><th colspan="2">Mediane (IQR)</th></tr><tr><th>CP</th><th>TD</th></tr></thead><tbody><tr><td>Max. Shoulder Abduction</td><td>10 (4)</td><td>3 (6)</td></tr><tr><td>Max. Shoulder Flexion</td><td>114 (11)</td><td>135 (13)</td></tr><tr><td>Min. Elbow Supination*</td><td>-49 (64)</td><td>-85 (10) †</td></tr><tr><td>Max. Elbow Pronation*</td><td>54 (25)</td><td>78 (14) †</td></tr><tr><td>Min. Elbow Extension</td><td>26 (15)</td><td>1 (9) †</td></tr><tr><td>Max. Elbow Flexion</td><td>139 (5)</td><td>149 (4) †</td></tr></tbody></table>

Notes: † means p<0.05; * 0° of pronosupination is when the wrist and elbow mediolateral axes are in the same plane (Fig 1A).

The range of minimum supination during performance tasks in the TD group (44-63°) highlights the important variability in tasks that did not explicitly demand maximal supination (Fig. 1B).

Only CP_01 and CP_05 were considered to have limitation in capacities of supination (minimum value of 7° and 13°). This limitation had consequences on performance, as these participants performed outside of the TD range. Yet, CP_05 consistently supinated below her measured capacity across all tasks. This highlights that she may not have been able to actively supinate to her full passive range of motion, possibly due to supinator weakness, but that contact with the object was able to facilitate better supination in performance. In contrast, CP_01 generally showed higher or equal supination in performance. This divergence in the translation of capacity into performance may suggest the need for different therapeutic strategies. However, the discrepancy in performance could also be due to different motion strategies. Therefore, a qualitative analysis of performance motion would be a valuable addition to future work.

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<figure><img src="image_5.png" /><figcaption>**Figure 1.** A – Angular references for pronosupination, B – Minimum supination (°) in performance and capacity tasks in TD and CP children.</figcaption></figure>

Interestingly, in the manipulation task, while all TD children supinated below 0°, even CP peers with good supination capacity did not consistently supinate beyond neutral. This suggests that other limitations likely influence this underutilisation and warrant further study of other joints' mobility to gain clearer insight into the underlying difficulties.

Future research with a larger and more diverse sample of children with CP is essential to validate these findings. Furthermore, a larger TD cohort could establish more robust normative data on the typical range of motion used in performance tasks, providing data for rehabilitation goals.

### 4. Conclusions

This preliminary study highlights the importance to consider both capacity and performance when assessing CP children, and of comparing these findings with TD
peers. Ultimately, a more comprehensive understanding of the performance-capacity relationship will contribute to the development of more targeted and effective rehabilitation strategies.

## Acknowledgements

The authors would like to express their gratitude to the families of the participants for their time and participation and to the occupational therapist Stéphanie Aiel for her support in the recruitment process.

## Conflict of Interest Statement

None.

## Contributors Roles

JR: Conceptualization, data curation, formal; analysis, Investigation, Writing original

Draft; AN: Conceptualization, Data curation, Investigation; MB: Supervision, Writing-review & editing; SD: Supervision, Writing-review & editing; YC: Supervision, Investigation, Writing-review & editing.

## Funding

This work was partly funded by a grant of the Société de Biomécanique and JR's CIFRE thesis is funded by the CMCR de Massues, French Red Cross.

## References

Krumlinde-Sundholm, L., Holmefur, M., Kottorp, A., & Eliasson, A.-C. (2007). The assisting hand assessment: Current evidence of validity, reliability, and responsiveness to change. *Developmental Medicine & Child Neurology, 49*(4), 259-264. https://doi.org/10.1111/j.1469-8749.2007.00259.x

OMS (Éd.). (2001). *Classification internationale du fonctionnement, du handicap et de la santé : CIF*.

Rab, G., Petuskey, K., & Bagley, A. (2002). A method for determination of upper extremity kinematics. *Gait & posture, 15*(2), 113-119. https://doi.org/10.1016/S0966-6362(01)00155-2

Rozaire, J., Paquin, C., Henry, L., Agopyan, H., Bard-Pondarré, R., Naaim, A., Duprey, S., & Chaleat-Valayer, E. (2024). A systematic review of instrumented assessments for upper limb function in cerebral palsy: Current limitations and future directions. *Journal of NeuroEngineering and Rehabilitation, 21*(1), 56. https://doi.org/10.1186/s12984-024-01353-6

Wu, G., van der Helm, F. C. T., (DirkJan) Veeger, H. E. J., Makhsous, M., Van Roy, P., Anglin, C., Nagels, J., Karduna, A. R., McQuade, K., Wang, X., Werner, F. W., & Buchholz, B. (2005). ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion—Part II: Shoulder, elbow, wrist and hand. *Journal of Biomechanics, 38*(5), 981-992. https://doi.org/10.1016/j.jbiomech.2004.05.042