Recruitment difficulties caused by a lack of eligible patients in the investigating center, calling into question the feasibility of the study.

The goal of this experimental prospective study is to build an explicative model of trait fatigue in adults with schizophrenia engaged in a psychosocial rehabilitation process.

The main questions it aims to answer are:

• Which factors amongst those evaluated explain the most of fatigue variance in people with schizophrenia?
• Which clinical factors characterise the most fatigued participants compared to less fatigued participants?

Participants will wear an accelerometer for seven days to assess their sedentary and physical activity behaviours as well as their sleep.

After this, they will undergo an experimental visit, to asses:

• Fatigue
• Cognitive function
• Tobacco and caffeine consumption
• Fatigue catastrophizing
• Sleep quality
• Sarcopenia risk
• Functional capacities
• Handgrip strength
• Quadriceps maximal strength and fatigability

Schizophrenia is a severe mental illness affecting about 1% of worldwide population. Diagnostic relies on multiple symptoms, divided into three main categories: positive symptoms, negative symptoms and cognitive/dissociative symptoms. Antipsychotic medication is actually the main pharmacologic treatment in schizophrenia but adverse effects can exacerbate other symptoms such as fatigue.

Fatigue has a high prevalence in schizophrenia. Unfortunately, fatigue has negative repercussions on daily living activities in this population, and no effective treatment has been identified for now. The lack of effective strategies to manage fatigue in schizophrenia can be due to the lack of knowledge about factors that can explain fatigue. As such, an explicative model of fatigue in schizophrenia has yet to be established.

Because fatigue is a complex and multifactorial mechanism, investigating its correlates could allow to propose new avenues for its multidisciplinary management, in order to delay its onset or minimize its negative impact. In comparison to healthy subjects, people with schizophrenia show increased physical inactivity and sedentary levels, worsened physical fitness and higher risks of sarcopenia, disturbed sleep, altered cognitive function, increased consumption of psychoactive substances (coffee and tobacco), an increased fatigue catastrophizing. Moreover, negative symptoms could also be linked to fatigue as it has been shown that fatigue could contribute to anhedonia in schizophrenia. Finally, antipsychotic medication can induce sedation, overlapping with fatigue, contributing to an exacerbated experience of the symptom.

Therefore, the goal of this study is to investigate whether physical inactivity, sedentary behaviour, physical fitness, sarcopenia risk, sleep, cognitive capacities, psychoactive substance consumption, fatigue catastrophizing, antipsychotic treatment and negative symptoms could contribute to fatigue in people in schizophrenia.

Inclusion Criteria:

• Patient with schizophrenia engaged in a psychosocial rehabilitation process.
• Patient with a stabilised evolution according to usual literature criteria (no modification or increase in antipsychotic treatment during the 4 weeks prior to inclusion).
• Absence of characterised major depressive episode.
• Patient affiliated or entitled to a social security scheme.
• Obtention of free and informed written consent, as well as the free and informed written consent of the guardian in the case of a patient placed under protection measure (guardianship).

Exclusion Criteria:

• Physical pain superior to 3 on a visual analog scale.
• History of severe inflammatory pathology or severe brain trauma.
• Medical contraindication to moderate-intensity physical activity practice.
• Patient having electroconvulsive therapy as current treatment.
• Addiction to toxic products such as alcohol, cannabis or other toxic substances other than tobacco.

Participants will be patients with schizophrenia, included in a psychosocial rehabilitation program.