Long COVID is a term commonly used to describe “signs and symptoms that continue or develop after acute COVID-19” (NICE Guideline, 2020a). We distinguish two stages in long COVID: (i) ongoing symptomatic COVID-19 for symptoms from 4 to 12 weeks; and (ii) post-COVID-19 syndrome for symptoms that continue for more than 12 weeks and not explained by another diagnosis (NICE Guideline, 2020a). These two forms of long COVID are characterized by multiple symptoms affecting respiratory and cardiovascular capacities, general symptoms such as fatigue, fever and pain, and several other symptoms (e.g., neurological, gastrointestinal, musculoskeletal, and psychological). On the whole, a list of more than 200 symptoms is mentioned, of which persistent fatigue has been found in 39–77% of patients previously infected by the virus (Davis et al., 2020; Townsend et al., 2020).

Post-COVID-19 syndrome can persist beyond 6 months: 76% of hospitalized patients for COVID-19 reporting at least one persistent symptom, and the most common is fatigue or muscle weakness for 63% (Huang et al., 2021). At 12 months, it is always the fatigue that mostly persists (53.1%) with reduced exercise capacity, dyspnoea, concentration problems, and sleeping problems (56.3, 37.5, 39.6, and 26%, respectively; Seeßle et al., 2021). To prevent this post-COVID-19 syndrome and to avoid the chronicity of fatigue, it seems necessary to propose an early intervention during the ongoing symptomatic COVID-19 phase (Townsend et al., 2020; O'Sullivan et al., 2021). There is currently no specific treatment for “acute” asthenia that has progressed for <4 months. However, a program combining exercise and therapeutic patient education has already shown significant benefits for combatting recent or semi recent fatigue following a cardiovascular event (Staniute et al., 2014; Van Geffen et al., 2015; Ter Hoeve et al., 2019) and even during cancer treatment (Van Vulpen et al., 2016; Zhang et al., 2018; Gheyasi et al., 2019). Exercise is also strongly recommended in chronic fatigue syndrome (Clark and White, 2005) and in fibromyalgia, where exercise is the only “strong for” therapy-based recommendation (Macfarlane et al., 2017).

While the resumption of physical activity after COVID-19 infection was controversial at the beginning of the epidemic (NICE Guideline, 2020b), the latest worldwide recommendations for returning to exercise are now unanimous even for patients suffering from long COVID (World Health Organization, 2019; NICE Guideline, 2020a; Haute Autorité de Santé, 2021a; NIHR Themed Review, 2021; World Physiotherapy, 2021). Exercise rehabilitation needs to start earlier and to be adapted to the symptoms with a focus on returning to daily activities and conserving energy (Alberta Health Services, 2019; Faghy et al., 2021). The addition of educational sessions could be beneficial to reduce anxiety (O'Sullivan et al., 2021) and to better manage and monitor the symptoms that may appear during exercise (NICE Guideline, 2020a). To set up this care, a hybrid rehabilitation is recommended with the use of in-home telehealth when the patient has the physical, technical and material capacities (Chartered Society of Physiotherapy, 2021; Ding et al., 2021).

Accordingly, the purpose of this pilot study was to assess fatigue in patients with prolonged symptoms after COVID-19 infection, i.e., during the ongoing symptomatic COVID-19 phase, and who received a mixed program of remote adapted physical activity and therapeutic education. The secondary objective was to evaluate the efficacy and safety of this training method thanks to aerobic and anaerobic parameters.

“CoviMouv': From Coaching in Visual to Mouv in real” is a nonrandomized controlled pilot study carried out on a small scale to evaluate efficiency of the telerehabilitation and its possible adverse effects, in order to determine the sample size of the definitive study. CoviMouv' received approval from the Local Ethics Board (IRBN142021/CHUSTE) and is registered at ClinicalTrials.gov (NCT05236478). Patients were recruited from March to July 2021 and signed a written informed consent. All participants had to be >18 years old, had been hospitalized in a COVID-19 unit at the Saint-Etienne Hospital without being intubated (if hospitalization in intensive care) and had to show post-COVID-19 fatigue for <3 months (COVID-19 infection confirmed by RT-PCR). The exclusion criteria were patients hospitalized in intensive care >72 h, intubated and/or ventilated in intensive care, and patients who were not hospitalized for COVID-19 initially.

In total, 17 patients (nine men and eight women) were recruited and assigned to tele-R (n = 9) or trad-R (n = 8) groups. Two trad-R patients did not return for post-testing. Thus, data were collected on nine subjects in the tele-R group and six subjects in the trad-R group (Figure 5). Participants achieved an average of 81 ± 9% and 78 ± 25% of the sessions for tele-R and trad-R groups, respectively. There were no significant differences between both groups at baseline (Table 2). No adverse events were declared.

The mean age of our sample was 52.1 ± 12.2 years old. Regarding COVID-19 infection, the average time of hospitalization was 8.1 ± 4.4 d.

The objective of our study was to assess fatigue, the most persistent symptom in the different forms of long COVID, after a mixed program of telerehabilitation and therapeutic education for patients with ongoing symptomatic COVID-19, i.e., with persistent symptoms of <3 months following a COVID-19 infection. Our results showed an improvement in CFS-11 in both tele-R and trad-R groups. Managing fatigue through exercise could be an effective solution for these patients with persistent symptoms. To our knowledge, this is the first study which has assessed the benefits of adapted physical activity for persistent symptoms of COVID-19, particularly for fatigue. Barbara et al. (2022) recently demonstrated the benefit of a combination of aerobic and resistance training on both cardiorespiratory and musculoskeletal fitness in long COVID-19 patients “with several months lasting symptoms.” After 8 weeks of exercise training, VO_2peak and muscle strength increased (Barbara et al., 2022). Thus management of long COVID-19, even away from infection, could be beneficial for health. In the literature, we found two case reports about the effects of exercise showing an improvement in physical function, muscle strength and exercise capacity, but no benefits on fatigue or quality of life for one (Mayer et al., 2021), and an improvement in cardiopulmonary function, muscle strength and fatigue for the other (Longobardi et al., 2022).

Regarding the efficacy and security of our remote program, this pilot study has demonstrated benefits of telerehabilitation on several parameters of physical capacities such as VO₂max, maximal aerobic power or walking distance. Anaerobic capacities were not enhanced. These parameters were increased in both groups, showing that personalized exercise is effective even in this original remote training method if supervised by a professional. Our results are comparable to other studies that showed equal benefits of home-based telerehabilitation in comparison with center-based rehabilitation (Maddison et al., 2019; Batalik et al., 2020; Fanget et al., 2022). Furthermore, people with prolonged post-COVID symptoms have often demonstrated reduced exercise capacity (VO₂ values ≤ 85% of predicted values). This was the case for 73% of our sample, which is consistent with the 75% of a larger sample assessed in the study by Motiejunaite et al. (2021). This exercise impairment was reversed for 64% of our subjects after 1 month of personalized exercise. Thus a holistic telerehabilitation program offering adapted physical activity and education, supervised by a team of experts, seems to be a good alternative rehabilitation program when a face-to-face program is not possible, and without adverse events detected in our sample.

Special attention was paid to the hyperventilation values. All of our patients had high values of ventilation per unit of carbon dioxide production and/or low values of resting end-tidal carbon dioxide pressure. This feature was also observed at peak exercise for 24% of patients by Motiejunaite et al. (2021). Wood et al. (2021) also reported low levels of end-tidal carbon dioxide despite normal respiratory rate in individuals with long COVID. In our study, a one-month rehabilitation program at hospital or in community-based center showed an improvement in the majority of parameters of hyperventilation syndrome; which was also found in patients with persistent symptoms after a COVID-19 infection and who underwent a respiratory rehabilitation program (Bouteleux et al., 2021). However, we note nevertheless that the values remained below the thresholds of good prognosis in our sample.

The main strength of our study was the originality of the program, offering a hybrid rehabilitation with adapted physical activity and education combined with face-to-face and remote interventions. This care at an early stage of the disease could help to prevent the chronicity of post-COVID-19 symptoms and the installation of vicious cycles of physical deconditioning, which itself promotes fatigue. This integrative and person-centered approach is also the one recently recommended by Roth et al. (2021).

Our pilot study presents limitations and the first is the reduced size of our sample. We have been limited by the end of the third wave of infection in France and a decrease in the number of patients previously hospitalized and in the ongoing symptomatic COVID-19 phase. However, these first results showed that an early intervention can improve physical function and reduce fatigue for patients with persistent symptoms after a COVID-19 infection. However, we lack a control group without rehabilitation to compare changes over time and evaluate the interest of this early management for patients. In addition, there was no randomization for tele-R and trad-R (the allocation was made arbitrarily based on a patient's sports and computer equipments), and no differences were found at baseline between two groups. This non-randomization may raise issues of socioeconomic differences for those who do not have access to the internet or who have limited computer skills, for example. Finally, it is important to highlight the debate concerning the existence or not of a long COVID. A recent study questions the attribution of persistent symptoms to a COVID-19 infection (Matta et al., 2022). In our study, we limited this bias by including patients referred by COVID-19 services of the hospital and whose COVID-19 infection had been confirmed by RT-PCR. Moreover, the existence of recommendations from major entities such as the World Health Organization, the National Institute for Health and Care Excellence, and the French High Authority of Health underline the importance of recognizing and managing symptoms to avoid anxiety and medical errancy. The association of adapted physical activity and education would allow a better understanding and control of persistent symptoms.

Thus, a larger study would be necessary to assess the relevance of exercise training in telerehabilitation of patients with persistent symptoms after COVID or long COVID. Furthermore, longer term follow-up would be necessary in order to assess if the benefits of this telerehabilitation persist over time. This is the subject of our next randomized study.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by Comité d'Ethique du CHU de Saint-Etienne—Commission Recherche de Terre d'Éthique Ref: IRBN142021/CHUSTE. The patients/participants provided their written informed consent to participate in this study.

CCo, PL, MB, and DH contributed to the acquisition of data. CCo wrote the first draft of the manuscript. DH provided critical revision for intellectual content and oversight. All authors reviewed and approved the final version of the manuscript.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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